Building Integrated Solar Technology 9783955533632, 9783955533625

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Roland Krippner (Ed.)

Building-Integrated

Solar Technology

Architectural Design with Photovoltaics and Solar Thermal Energy ∂ Green Books

Building-Integrated Solar Technology

Edition ∂ Green Books

Building-Integrated

Solar Technology Architectural design with photovoltaics and solar thermal energy

Roland Krippner (Ed.)

Imprint

Editor: Roland Krippner, Prof. Dr.-Ing. Authors: Gerd Becker, Prof. Dr.-Ing. Ralf Haselhuhn, Dipl.-Ing. Claudia Hemmerle, Dr.-Ing. Beat Kämpfen, Dipl. Arch. ETH SIA M. Arch. Roland Krippner, Prof. Dr.-Ing. Tilmann E. Kuhn, Dr. Christoph Maurer, Dr.-Ing. Georg W. Reinberg, Arch. vis.Prof. DI. M. Arch. Thomas Seltmann Project Management: Fabian Flade, M.A. Jakob Schoof, Dipl.-Ing. Editing and Layout: Jana Rackwitz, Dipl.-Ing. Jakob Schoof, Dipl.-Ing. Translation: Susanne Hauger Proofreading: Emma Letizia Jones Graphics: Ralph Donhauser, Dipl.-Ing. (FH) Simon Kramer, Dipl.-Ing. Simon Axmann, B.A. Annika Ludwig, B.A. Fabiola Tchamko, B.A. Ka Xu, B.A. Frido Flade GmbH FP-Werbung

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Contents

Prologue

6

Introduction and history Solar technology and building culture From solar house to energy self-sufficient building The actors in solar construction Conclusions and outlook

8 8 9 18 19

Buildings as catalysts for energy transformation From energy transition to energy transformation The merging of energy sectors Solar technology as design challenge

20 20 21 22

Physical and geometric principles Foundations of solar energy use Design tools

24 24 27

Technology and systems – photovoltaics The functioning of photovoltaic installations Solar cells and photovoltaic modules Inverters as system headquarters Battery storage systems Planning and design Installation, commissioning, operation and maintenance Requirements, standards and regulations

28 28 30 36 37 38 44 47

Technology and systems – solar thermal energy Operation of solar thermal installations Applications of solar thermal energy Solar thermal energy in the context of the building shell Building shell components with solar thermal functionality Storage and other system components System concepts for solar thermal energy installations Requirements for integrated collectors

52 52 54 56

Integration of solar installations Basics Additive or integrated installation? Building inventory Design integration Structural integration

64 64 64 65 66 68

Designing and building − photovoltaics From the igloo to the tree The building shell as part of the energy system Influence on the design process

72 72 73 76

57 60 62 63

Designing and building – solar thermal energy Climate-appropriate construction Types of solar energy use Indirect use of solar power via thermal collectors Building design with thermal collectors Implementation of thermal collectors in practice Outlook: the future of solar thermal energy Case study 1: Residential complex in Salzburg Gneis-Moos Case study 2: Residential building Schellenseegasse, Vienna

80 80 80 82 86 88 89 90 91

Economy and ecology A look at the life cycle of solar installations Financing Profitability of PV installations Profitability of solar thermal installations Ecological assessment Energy certification and green building labels

92 92 92 94 98 100 102

Built examples Building-integrated solar technology in detail Kindergarten, Deutsch-Wagram Single-family house, Glattfelden Office and residential building, Darmstadt Office building, Kemptthal Office building, Kasel Museum of Archaeology, Herne Apartment building, Bennau Day care centre, Marburg Residential and office building, Romanshorn Education centre, Niestetal Convention centre, Lausanne Centre for Photovoltaics, Berlin

104 104 106 108 110 112 114 116 118 120 122 124 126 128

Appendix Acknowledgements Authors Index of illustrations Literature Regulations, guidelines, standards Glossary Subject index Register of companies and individuals

130 130 130 132 133 135 136 138 140

Prologue

Roland Krippner

In the past few decades, architecture and solar energy have been engaged in an increasingly close, occasionally tense interrelationship. Even though predictions such as “Solar Building to Become a Megatrend” [1] have not been fully borne out, energy-efficient design, construction and modernisation have nevertheless earned a central role in legislation, and a significant place in the curricula of universities and training institutes. The implementation of the EU’s building guidelines (2010/31/EU) now marks the next big step. As yet, the member states of the EU have only partly defined the form that the minimum energy standard mandated in the guidelines for all new buildings in the EU will take. But it is already apparent that supplying buildings with renewable energies, primarily solar heating and solar electricity, will become increasingly important over the coming years. In light of these developments, it is surprising how reticently the discussion of the production of solar energy in buildings has been broached both in public and in professional circles. In the overcrowded and somewhat unmanageable market of books written for architects and engineers, active solar technology is at best a niche topic, and relevant publications on the subject are often already years behind. Texts specialising in the respective energy system technologies dominate. In addition, the reception of the subject is determined largely by photovoltaics. Solar thermal energy, by contrast, remains proverbially underexposed; yet it is perhaps the very thing that could make a significant contribution to a “thermal transition” in Germany. In 2015, 32.5 per cent of the electricity used in Germany was from renewable sources [2]. In the thermal sector of the same year the number was merely 9 per cent. The CO2 emissions for the thermal energy consumed in Germany 6

have remained essentially constant over the last ten years or more [3]. It would be a mistake to reduce the discussion of solar energy in and on buildings merely to its technical aspects. Model calculations and initial pilot projects are already making it clear that photovoltaics and solar thermal energy will have to be fully incorporated into the design of any zero-energy and PlusEnergy buildings of the future that exceed the size of single-family houses. The (flat) roof areas of such buildings alone are generally not large enough to produce the requisite amounts of energy. The design of active solar technology and its integration into buildings therefore constitutes the major challenge facing all architects who wish to contribute to planning the building inventory of the future. In light of the above, the book Building-Integrated Solar Technology for the first time addresses the intersection of architecture and active solar technology within a broader textual framework. Unlike previous texts, it places its investigations of solar thermal energy and photovoltaics on an equal footing, and discusses their individual design potentials. The title of the book relates to established terminology from the solar industry. In the field of photovoltaics, the phrase “building-integrated photovoltaics” (BIPV) or “construction-integrated photovoltaics” has already established itself; but solar thermal energy, too, represents a central building block in the development of a decentralised energy supply for the future. For this reason, the Solarenergieförderverein Bayern e. V. (the Bavarian Association for the Promotion of Solar Energy) categorises its associated operations under the heading “building-integrated solar technology” (BIST), a term 0.1 Umwelt Arena, Spreitenbach (CH) 2012, René Schmid Architekten

which is still relatively new among scientists, and whose definition still suffers from a certain lack of conceptual clarity. A major characteristic of building-integrated solar technology is that, as a rule, the collector surface and/or the PV generator represent a design-determining element of the building shell. In principle, two different strategies can be observed in handling collectors and PV modules. The solar technology system can be concealed in the roof area, in which case it has little effect on the design of the building. Particularly in the context of historically important building complexes, this is a possible way to employ solar technology. In such projects, admittedly, the opportunity to effect the bold transformation of buildings from energy consumers to energy producers is often squandered. Such a goal is better achieved when the solar installation is integrated visibly into the roof, and especially into the facade. The latter approach, however, makes much higher demands on the design not only of the solar installation itself, but also of the entire building. Only in qualitatively sophisticated architecture can solar technology have an enriching influence on contemporary building culture. For this reason, this book focuses on buildings in which architects have specifically employed solar technology as a design-determining element (Figure 0.1). The structure of the book is designed so that it provides rapid access to essential content useful for both experts and laypeople alike. After a brief historical overview of building-integrated solar technology, the chapter “Buildings as Catalysts of Energy Transformation” establishes the societal and urban development context of the present challenge. Chapters 3 through 5 deal with the physical and geometrical foundations of solar energy usage, and provide a more in-depth discussion of the important technical characteristics of photovoltaic and solar heat-

ing systems. In this section, authors from the Deutsche Gesellschaft für Sonnenenergie e. V. (The German Society for Solar Energy), as well as the Fraunhofer Institute for Solar Energy Systems (ISE), bring to bear the expertise they have acquired through both research and practice. The application of the material to real projects is covered in chapters 6 through 8 of the book. Building on general assessments of the “work of integration”, two architects who have spent years making outstanding contributions to the field report from their wealth of experience and give advice on the design and implementation of building-integrated solar installations. A further chapter points out the important economic and ecological aspects of solar energy use. The book then concludes with a selection of representative buildings, complete with architectural drawings and information on the technologies and products used. It is hoped that this book will serve as an impetus for architects and engineers, students, employees of public agencies and, last but certainly not least, building clients, to explore and employ the numerous fascinating technical and design possibilities of solar technology, and to develop them further through new approaches in their own projects. Notes [1] German Solar Energy Association (BSW: Bundesverband Solarwirtschaft e. V.): Press release on the occasion of Munich trade fair BAU 2007. www.solarserver.de [2] Agora Energiewende (ed.): Die Energiewende im Stromsektor: Stand der Dinge 2015 (The Energy Transition in the Electricity Sector: The State of Affairs 2015). www.agora-energiewende.de/fileadmin/Projekte/2016/Jahresauswertung_2016/ Agora_Jahresauswertung_2015_web.pdf (Status as of 31.08.2016) [3] PwC (ed.): Energiewende-Outlook: Kurzstudie Wärme (Energy Transition Outlook: Brief Study on Thermal Energy). www.pwc.de/de/energiewende/assets/pwc-ewo-kurzstudie-waerme-2015.pdf (Status as of 30.08.2016)

0.1

7

Introduction and history

Roland Krippner

• Solar technology and building culture • From solar house to energy self-sufficient building • The actors in solar construction • Conclusions and outlook

Solar technology and building culture

Even in the many cases in which they are integrated in a functionally correct and structurally coherent way, it must be said that their integration into the aesthetic aspect of design is often less successful. Solar systems have occasioned an enormous expansion in the technical building repertoire, but – as has been the case for other new products and innovative materials – this expansion must be converted into a conceptual architectural framework. In the incorporation of collectors and PV modules, both technical features and structural and aesthetic concerns must be taken into account. The term “building-integrated solar technology” encompasses both of these aspects in equal measure, and this book likewise addresses them together. Since the early days of active solar energy use in the 1970s, the intersection of architecture and solar technology has been emphasised, and the “willingness to engage in creative approaches from design to architecture” [3] advocated. A large number of realised projects over the past decades have shown, however, that it is precisely this call that has all too often gone unanswered. Given the many positive examples in existence, this would be quite puzzling were it not for the fact that these exemplars are simply too little known. It follows that building-integrated solar technology – that is to say, those design solutions in which the relevant systems form a significant part of the building – continues to lead a niche existence in the field of energy-efficient construction. Reasons for this include professional barriers between the participating players (engineers versus architects), as well as the failure of manufacturers to maximise innovation potential in the production process [4]. Furthermore, thanks to guaranteed feed-in compensations and sharp price reductions on the international

The use of solar energy in and on buildings will be a central theme in future construction. Thermal solar collectors and photovoltaic (PV) modules are already natural components of energy-efficient buildings and innovative shell constructions. The systems available on the market feature efficiency and elegance in equal parts, as demonstrated in trade fairs and in numerous design awards. It is no accident that the past decades have seen photovoltaics and solar thermal energy achieve their status as symbols of progress. Solar collectors and PV modules are important elements of solar construction, but they are not the only ones. In the building-specific use of solar energy one must differentiate between direct (passive) and indirect (active) principles [1]. The first step is to exhaustively employ the direct measures in order to reduce energy needs and to ensure a comfortable internal climate. This encompasses fundamental planning strategies such as a sensibly organised layout, a compact building volume design, appropriate choices of materials and an optimised construction of the building shell, which should in turn reference regional building traditions [2]. Building on this, the next step utilises solar heating and photovoltaics via indirect measures to contribute a sustainable source of energy, replace fossil fuel energy supplies and reduce CO2 emissions. Building-integrated solar technology as a design challenge

Regardless of whether they are of standard format, or custom made for projects of sophisticated design, installation systems always alter the appearance of buildings, and therefore of the cities and the countryside as well. 8

From solar house to energetically self-sufficient building

market, there is a disproportionate focus on photovoltaics. As a consequence, the equally energy efficient and economical installation systems of solar thermal energy are underutilised, especially in ambitious architectural concepts. In addition, the substantial economic downturn in the European solar energy sector over the past few years has led in turn to radical structural changes in building-integrated solar technology. At present, only a few design specialists and systems manufacturers are active on the market. To date, this has not yet negatively impacted on the number and quality of sophisticated solutions, as evidenced, for example, by the “BuildingIntegrated Solar Technology Architecture Prize” of 2014. Paths to a smart solar architecture

For sustainable architecture and urban development, a decentralisation of the energy supply is of critical importance. Referencing Ernst Friedrich Schumacher’s “Small is beautiful” (1973), the German journalist Franz Alt speaks of “Dächertec statt Desertec (roof tech instead of desert tech)”. With this, he emphasises the crucial role that the activation of building shell surfaces by solar technology will play in a future Germany with a technically and economically feasible, 100% renewable energy supply [5]. With the implementation of the European directive governing the overall energy efficiency of buildings, which takes effect in 2019 and 2021 respectively and demands that new buildings conform to the “Nearly Zero Energy” standard, building-integrated solar technology will (again) make clear gains in currency and relevance. The increased research and marketing activities over the past years, coupled with building labels such as “Plus-Energy House”, “Efficiency House Plus” or “SolarActivehouse”, have already had similar effects. The challenge now lies in viewing these developments as a building culture mission – not only in new construction, but also in the energy refurbishment of the existing building inventory.

From solar house to energetically self-sufficient building Building-integrated solar technology is not a new phenomenon. Already toward the end of the 1930s, prototypical developments of solar houses with solar energy roofs were to be found, particularly in the USA. The first “active solar house” was the MIT Solar House I in Cambridge, Massachusetts (1939), where flat-plate collectors are extensively integrated into the pitched roof. In 1948, the architect Eleanor Raymond, working with the energy engineer Maria Telkes, completed the Dover Sun House (also known as MIT Solar House VI) in Dover, Massachusetts. On the south side of the upper storey it features the first complete collector facade of vertical components and is touted as the first solar-heated residence in the world [6]. Up until the mid 1970s, the USA oversaw the construction of further experimental buildings in whose design architects increasingly became involved. This followed the recognition, beginning in the mid-1950s, that the design of active solar houses necessitates close interdisciplinary teamwork among architects, heating engineers and prospective residents [7]. Occasionally, an American prototype would become known in central Europe: In his search for ideas for an energy-efficient building company, the engineer Klaus Daniels set out on a research trip through the USA in the mid-1970s to familiarise himself with the energy and economic potential of active solar technology [8]. In Germany, where the same time period saw an increasing preoccupation with alternatives to fossil fuel energy sources, the topic was approached on multiple levels. The year 1974, during which the first solar facilities were installed, is taken to be the “inception” date of such models. In a piece written in 1979, the author Axel Urbanek suggested that, as this “technical-sociological development” was still in its early stages, the “predominantly aesthetic” demands on the new construction challenges 1.1 Joinery workshop, Freising-Pulling (D) 2010, Deppisch Architekten

1.1

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Introduction and history

1.3

1.2

were premature. Urbanek was therefore confident that there would be a “second phase of consciousnessraising” [9]. The first buildings with solar collectors, created in part through private initiatives, and in part as publicly backed projects or as business developments, show clear evidence of a formal repertoire that persists even to the present day. Equally evident, however, is a frequent lack of architectural quality. A collection of the “most beautiful German solar houses” is not apparent; though from solar housing’s infancy, trade journals have espoused the topic of the integration of solar technology into buildings as an “architectural expedient” [10]. Early achievements in synthesis – the 1980s

The beginning of the 1980s finally brought with it a synthesis between the newest solar technology and innovative architecture. In 1982, Thomas Herzog, together with Bernhard Schilling and in collaboration with the Fraunhofer Institute for Solar Energy Systems, created a residential complex in Munich in which tube collectors and PV modules are integrated into the building shell in a functionally and aesthetically coherent way. The building, highly regarded in its day, represents the further development of a solar house typology designed by Herzog in the 1970s, in which the living spaces are expanded southward via glass-enclosed additions with a triangular

1.4

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cross-sectional geometry. In this case, additional active solar technology is integrated into the plane of the glazed roof of the conservatory (Figure 1.4). Just one year later, an inexpensive residential complex designed by Paolo Puccetti was built, and a majority of its pitched roofs fitted with full-surface solar collectors. However, the neighbourhood concept, still groundbreaking today, has inspired no direct imitations. Its fate is entirely symptomatic of the fact that the main focus in the 1980s remained fixed on passive solar architecture, and on general questions of ecological construction. In a series of projects, active solar technology was taken into consideration conceptually but deemed practically feasible only once the systems become economically “affordable” [11]. In the meantime, a set of research studies was completed that primarily addressed the integration of solar technological systems in industrial prefabricated construction [12]. Further research investigated the technical and formal installation requirements of flat-plate collectors in select roof and outer wall constructions of industrially prefabricated industrially prefabricated single-family and semi-detached residences. The assessment of tolerances was conducted, among other things, in the areas of dimensions, collector loads, edge connections and electrical wiring, and was evaluated in morphological overviews [13]. Typically, these first studies placed functional

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From solar house to energetically self-sufficient building

and constructive criteria – largely uncoupled from questions of aesthetics – at front and centre. In the middle of the 1980s, the German architecture journal Deutsches Architektenblatt featured its first substantial and detailed contribution to the “Design of Solar Installations”. In addition to (solar) geometrical parameters such as azimuthal and inclination angles, it introduced solar thermal components with their respective range of applications and suitability. The author of the article emphasised that collector technology had matured to the point where the “available state of knowledge” could be used for “creative design work” [14]. But even though he explicitly addressed architects, there are no built examples to be found anywhere in the article. The establishment of photovoltaics – the 1990s

Plausible concepts for the integration of active solar technology into architecture are to be found among the already mentioned precursors. But the more regular use of natural and assured building-integrated solar technology truly began only in the early 1990s. In some cases this development was stimulated by federal or state-run promotional initiatives, such as the “1000 Roof Programme” launched in September of 1990, but for the most part the impetus stemmed from the ambitions of architects and/or building clients. An example illustrating the new attitude is the kindergarten in Frankfurt-Griesheim (1990), in which a glass atrium with a triangular cross section connects the two parts of the building (Figure 1.2). Beneath the ventilation flaps in the ridge area, architects Funk and Schröder have mounted a band-like PV installation composed of three rows of vertically oriented modules above the glass surface. Another “additive” solution can be seen in the public utilities operations building in Konstanz by Schaudt Architekten (1997). The five-storey building has a 45° pitched roof drawn down to the ground floor, which is clearly partitioned into full height sections by a shading structure made up of PV elements (Figure 1.3). Architects Kramm & Strigl showcased their PV installation at the Zukunftszentrum (Future Centre) in Herten in 1995 as an independent constructive element. The square polycrystalline modules in this case are attached to the facade of the administrative building, which has a 5° slant. They form a harmonious accent between the white metal panels of the building pedestal and the superimposed glazed greenhouse (Figure 1.5). By far the most public attention in favour of active solar energy use was garnered by the Freiburg architect Rolf Disch with his residential and office building Heliotrope (1994). The bi-axial sun-tracking PV installation on the roof of this rotating Plus Energy House generates more

electrical energy than the building uses (Figure 1.7). Integrated into the railings of the circumferential balcony are additional horizontal evacuated tubes, whose vertical collector boxes reference the facade’s grid pattern. Heliotrope represents a significant marker in the advent of the “solar” era, and its impact is not limited to the building’s immediate built environment. In the refurbishment of the stairwell facade of the Public Utilities Building in Aachen (1991), the architect Georg Feinhals first employed (poly)crystalline cells in insulation glass (Figure 1.6). The post-and-beam construction, which is vertically and horizontally partitioned into a regular alternating arrangement of narrow and broad sections, features more than 100 large custom made inset photovoltaic modules. The PV installation functions as a sun shade, but the spacing of the cells also admits daylight and allows for a visual link between inside and out. The architect varied this almost self-evident approach to a PV facade, “the first of its kind worldwide” [15], a few years later in an office building in Cologne (2003). Two additional public buildings of the mid-1990s demonstrate the integration of photovoltaics into warm facades on a new order of magnitude. In the Pompeu Fabra Library (1995) in Mataró by Miquel Brullet i Tenas, virtually the entire south face of the building above the ground floor is a PV facade. The poly-crystalline modules are arranged in three rows on the exterior surface of the double facade, which acts as a kind of air collector. The top section of the facade area is glazed. At the time of its completion, the library’s facade was one of the largest building-integrated PV installations in Europe

1.2 Kindergarten in Griesheim (D) 1990, FS Architekten 1.3 Operations building in Konstanz (D) 1997, Schaudt Architekten 1.4 Residential building in Munich (D) 1982, Thomas Herzog und Bernhard Schilling 1.5 Zukunftszentrum in Herten (D) 1995, Kramm & Strigl Architekten 1.6 Public utilities building in Aachen (D) 1991, Georg Feinhals 1.7 Residential and office building in Freiburg (D) 1994, Rolf Disch SolarArchitektur 1.7

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(Figure 1.11). The same could be said four years later of the Mont-Cenis Academy (1999) in Herne-Sodingen, by Jourda + Perraudin and HHS Planer + Architekten (Figure 1.12). Here, large-scale PV modules have been installed as shading elements into the glazed outer climatic shell. While the monocrystalline modules in the western facade are arranged in up to three rows offset from one another, the slightly slanted modules on the roof are distributed depending on their shading effect. Here, different module types with varying degrees of transparency have been employed. Above the two building rows within the glass hall, the modules are denser, whereas those above the communal areas in between are fitted more porously with solar cells. The result is that the “glass sky” of the hall has a more piecemeal structure. The multiple applications of its physical characteristics are considered a big advantage of photovoltaics [16]. An especially illustrative example for this functional and aesthetic overlap is the utilisation of PV modules as sun protection, as in the buildings just mentioned. Shading elements as well as photovoltaic installations work most effectively when they are optimally aligned with the sun. In the Public Utilities Building in Aachen and in the Mont-Cenis Academy, for example, the modules integrated into the glass roofs and facades provide “simple” sun protection. This function is effectively increased when the photovoltaics are attached to the building as a brise-soleil, or integrated into adjustable shading elements. The mid-1990s gave rise to groundbreaking applications of these concepts. In 1992, on the six-storey south-western facade of the Scheidegger office building, Hostettler & Partner combined projecting, slanted PV elements to form a folded “saw-tooth” facade. In some sections, inward-sloping glass panels in the window areas create an intermediate temperature zone in order to harness solar radiation in winter and prevent heating in summer. In the Solar House in the International Horticultural Exposition (1993) in Stuttgart, HHS Planer + Architekten took this strategy one step further. Arranged above the glazed, slanted roofs of the conservatories are, among other things, PV louvres that can be tracked about their vertical axes. In the Public Works office building (1996) in Winterthur, Theo Hotz used mono-axially tracking PV fins in a pre12

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positioned steel construction, so as to ensure effective sun shading during good daylight conditions as well as a visual connection between interior and exterior spaces. The role of solar thermal energy at the turn of the millennium

As a rule, it was photovoltaic installations used in conjunction with advanced architectural projects that garnered the most attention during the 1990s. Nonetheless, by this time, solar thermal installations were already considered fully matured, “state-of-the-art" technology for water heating and space heating support. Overall, in the decade from 1990 to 2000, well over two million square metres of collector area was installed, with capacity growing at an annual rate of 20 – 40 %. Two significant examples in residential construction in which flat-plate collectors were added to or integrated into the facades are the Double House in Bregenz (1996) and the terraced house complex in Batschuns (1997), both designed by Walter Unterrainer. The large-scale deployment of air collectors in building facades is showcased in two other projects. In the Naturerlebniszentrum (Nature Experience Centre) Gaytalpark (1996) in Körperich-Obersgegen, Eckard Wolf divided the collector facade into four sections of varying size. The facade elements are inclined slightly sunward with respect to the vertical plane, and are well suited to the terrain. The south-eastern facade of the four-storey Gründerzentrum (Centre for Entrepreneurs) (1998) in Hamm, by HHS Planer + Architekten, functions as a huge, glazed collector. Ventilation grilles form the upper edge of this well proportioned, horizontally gridded facade (Figure 1.13). Occurring in parallel with the completion of these buildings, extensive international studies were conducted in the mid 1990s in which integration strategies were investigated in detail and summarised [17]. At this time, the architect Manfred Hegger stated, “We are still standing at the beginning stages of the deployment of PV in architecture [...]. [The movement] has just started to take up the challenges of a new technology and to combine them in interesting ways with a new architecture, which utilises the sun and light in new ways.” [18] A cursory view of the decade – the first phase in which one can truly speak of “building-integrated solar technology” –

From solar house to energetically self-sufficient building

shows that a large array of applications of solar technology had already been proven in practice, even if only a scattering of those projects is known among experts. A kaleidoscope of ideas – the SeV competitions since 2000

The competition activities sponsored by the Bavarian Association for the Promotion of Solar Energy (Solarenergieförderverein Bayern e. V., abbreviated SeV), founded in 1997 [19], clearly reflects the increasingly wide-ranging impact of the topic in the ensuing years. The SeV architecture prize, with its emphasis on “building-integrated solar technology”, has now become one of the leading events in this field in Europe, joining the Swiss Solar Prize, which has been awarded to buildings, integrated installations and architects since May of 1990, and the German and European Solar Prize offered by Eurosolar, which has been honouring architects annually since 1994. In 2000, the SeV competition was held for the first time, with the theme “innovative building-integrated solar electricity installations in Bavaria”. Among the sixteen rather heterogeneous entries, two designs in particular showed potential for the integration of photovoltaic installations into building shells. First place was awarded to the Nikolaus-Fiebiger-Centre of the Clinical Molecular Biology Research Centre of the Friedrich-Alexander University in Erlangen (University Building Authority, Christof Präg 2000). In the uppermost storey of its south facade it features a light-weight curved “solar awning”, while the facade of the bulk of the building is largely covered with horizontal, linearly tracking PV glass louvres. The photovoltaics are incorporated into the technical aesthetic of the research building in an exemplary fashion (Figure 1.8). The office building Jockisch in Landshut by Architekten HBH (Special Prize 2000) recognisably references Rolf Disch’s Heliotrope (Figure 1.9). Outside the glass facade of the cylindrical building, the architects have placed a steel construction with horizontal PV louvres; and together with the flat, inclined roof installation, these continually track the sun’s position. Though the approaches used are not completely new, these outstanding projects showcase a broad variety of integration possibilities within the context of thoroughly ambitious energy and design solutions. The next competition, with the theme “Solar Electricity from Facades”, was announced in 2001, and for the first time, accepted project entries from all over Germany. Selected from a pool of ten submissions, the Headquarters of the Timber Trade Association (1999) in Munich by PMP Architekten received First Prize. Incorporated into the projecting, glazed anterior structure of this 50-metrehigh building are polycrystalline PV modules. Extending from the third to the eleventh storeys, they form one broad and one narrow band which emphasises the verticality of the building from afar, but on closer approach, can be seen to be horizontally sectioned by cover strips (Figure 1.10, page 12). Two further projects were awarded special prizes in the competition, and for the first time one of them was a

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1.13 1.8 Nikolaus Fiebiger Centre in Erlangen (D) 2000, University Building Authority Erlangen (Christof Präg) 1.9 Office building in Landshut (D) 2000, Architekten HBH 1.10 Office building in Munich (D) 1999, PMP Architekten 1.11 Library in Mataró (E) 1995, Miquel Brullet i Tenas 1.12 Academy for advanced training Mont-Cenis in Herne (D) 1999, Jourda + Perraudin; HHS Planer + Architekten 1.13 Business incubator in Hamm (D) 1998, HHS Planer + Architekten

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building refurbishment project: the modernisation of a simple industrial warehouse in Erfurt (2001). In this case, the photovoltaics have been detached from the building face and integrated, in the form of eleven rows of polycrystalline glass modules, into an eleven-metre-high galvanised steel construction set in front of the facade (Figure 6.13, page 70). The project, developed by the author together with Peter Bonfig, with expert advice from Prof. Thomas Herzog at the Technical University of Munich, is as much a visible symbol for a technology of the future as it is solar protection with optimised solar electricity use. The third call for competition entries under the heading “Architecture and Solar Power – Building-Integrated Photovoltaic Installations” went out in 2005. Despite the long interval between this competition and the previous one, only seventeen projects were entered. Nevertheless, on this occasion the submission designs were of a significantly higher quality overall. First prize was won by the refurbishment of two nine-storey residential buildings in Freiburg (2001, Figure 6.9, page 69) that were built in the second half of the 1960s. The architects Rolf + Hotz transformed the closed south facade into a full height unbroken photovoltaic installation. The horizontally arranged glass modules form a suspended, rear-ventilated facade. On their long sides they are fixed to the aluminium supporting structure with visible black clamping profiles. The back is covered with a black foil, so that even from afar each rectangular frameless element is individually outlined by a dark border. One of the five recognition awards of this competition was awarded to the Paul Horn Arena in Tübingen (2004, Figure 6.5, page 66). Here, Allmann Sattler Wappner have furnished its entire south facade with vertically oriented modules in four different sizes. The architects have employed green polycrystalline PV cells in a glass-foil construct, referencing both the location and the general concept of the building. A distinct white border formed by the foil laminate on its back structures each module and the overall appearance of the facade. Each frameless PV panel is fastened with four multi-part light-alloy stand-offs, which makes it possible to replace individual units if needed.

In contrast to this, the single-family house in Hegenlohe by Tina Volz and Michael Resch (2005, Figure 6.1, page 65) features an elevated PV array atop its shallowangled southwest-facing pitched roof. The horizontally oriented polycrystalline modules are arranged in six rows, and the entire installation is partitioned into two sections conforming to the interior zoning of the building. The module rows project slightly beyond the ridge and eaves, and their stand-off mounting is apparent. With this house, the architects have succeeded in creating an outstanding example of a residential building that embodies a compelling symbiosis between solar technology and architecture.

14

International dynamics – developments since 2008

Starting in 2008, SeV began to hold its competition on a three-year cycle, broadened its scope to include solar thermal energy, and opened it – initially billed as a “European Prize” – to full international participation. In 2008, 40 projects were submitted, of which the jury reviewed 38 entries from eight countries. The European Prize for Building-Integrated Solar Technology was awarded to a new office building for Marché International in Kemptthal near Zurich (2007) by Beat Kämpfen (see Built Example, page 112f); while second place went to an inner city residential and office building in Darmstadt (2006) by Opus Architekten (see Built Example, page 110f). Both projects showcase exemplary energy roof solutions in which not only the overall building concept but also the specific details in the solar technology are convincingly expressed. The jury also awarded three honourable mentions. Two of them were given to buildings that pursue very different and novel approaches to their integration work. In the Sino-Italian Ecological and Energy Efficient Building (SIEEB) for the Tsinghua University in Beijing by Mario Cucinella Architects (2006) – a powerful and architecturally unusual composition – the fin-like PV structures that project from the building, floor by floor, constitute an important and design-defining element (Figure 1.16). The institute building has a U-shaped footprint and is oriented on a north-south axis. Its design incorporates multiple overlapping uses and many references to traditional Chinese symbolism. The varying functional levels of

From solar house to energetically self-sufficient building

the building shell are expressed effectively in both construction and design. The Solar House, with which the team of the Technische Universität Darmstadt won the Solar Decathlon in Washington (USA) for the first time, also represents a new building type. In this experimental building, the solar technology systems integrated into the roof and the facade contribute significantly to the goal of energy selfsufficiency. On the building sides, the amorphous silicon modules are fastened to wood slats and integrated into folding shutter-like wooden doors. This ensures that the slat orientation can be adjusted both for full sun exposure, and to control the amount of light entering through the facade (Figure 1.14). In 2011, the architecture competition for Building-Integrated Solar Technology began accepting projects from all over the world for the first time. Even though most of the 84 entries came from German-speaking regions, the response from a total of thirteen countries attested to the expansion of the event. This time, the architecture prize was awarded to a building type in which design requirements are usually relatively rare: a joinery shop in Freising-Pulling (2010). The building, designed by Deppisch Architekten, is a paredback, elegant structure with a gently inclined north-southoriented roof whose entire surface is covered with photovoltaics. The PV array terminates precisely at the roof edges and has no visible penetrations, which lends the entire building shell a smooth, planar appearance (Figure 1.1, page 9).

The deltaZERO buiding in Lugano by DeAngelis Mazza Architetti (2nd prize, 2009) is a residential high-rise, with a primary construction of reinforced steel acting as its internal storage mass, and a steel and glass facade (Figure 6.11, page 70). On its southern side, integrated full storey-high solar collectors support heating and hot water supply. In this building, the zero-energy concept is combined with a purist design style. The architects have succeeded in incorporating the solar thermal components into the facade in an exceptionally elegant manner, both technically and structurally. The refurbishment of a historical brewery in Bad Tölz by Lichtblau Architekten (3rd prize, 2009) shows that, despite the increased complexity it entails, the successful transformation of original tile roofs into energy roofs is entirely feasible. The central element is the fully glazed solar roof with integrated, mutually coordinated modular systems for light, air, heating and electricity – a symbiosis between old and new that beautifully demonstrates the potential of solar technology in existing buildings. New approaches to the renovation of existing buildings and to energy self-sufficiency have likewise been taken in the three projects that received recognition awards in the competition. In the refurbishment of the headquarters of Energie Steiermark in Graz (2010), Ernst Giselbrecht + 1.14 Solar House for the Solar Decathlon in Washington (USA) 2007, Team Deutschland/TU Darmstadt 1.15 home+ for Solar Decathlon Europe in Madrid (E) 2010, Hochschule für Technik, Stuttgart 1.16 Institute building in Beijing (CN) 2006, Mario Cucinella Architects

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Introduction and history

1.17

Partner partitioned the office building facade according to the respective programmatic demands. The opaque areas of the parapets are partially fitted with PV modules (Figure 1.18). For the Solar Academy of the firm SMA in Niesetal (2010), HHS Planer + Architekten designed a building that is independent of the grid and supplies 100 % renewable electricity (see Built Example, page 124f). In the energy self-sufficient new event centre at Schloss Montabaur (2010), the architectural firm Graf has integrated semi-transparent thin film modules into the oval glass dome. Varying degrees of transmission in the modules combine with the solar protection glass to create appealing lighting effects in the building’s interior (Figure 1.17). In 2011, in addition to the recognition awards, a special prize for “Student Projects” was conferred for the first time in order to honour the significance of the Solar Decathlon Competitions with their exciting building prototypes. One contribution to the Solar Decathlon Europe in Madrid, home+ (2010) by the Hochschule für Technik (Technical University) in Stuttgart, is persuasive in its ingenious energy concept; in which PVT hybrid collectors are employed to generate heating, cooling, and electricity. The bi-toned, gold-bronze shimmering silicon cells of its PV facade present solar technology in new and colourfully stylish forms (Figure 1.15, page 14). The search for holistic concepts – the present situation

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2014 marked the sixth time the competition was held, and in that year the timeliness and relevance of the topic, which had receded in recent years from the attention of architects and building clients due to the economic problems facing the solar sector, was reinforced quantitatively as well as qualitatively. The 137 submitted projects, from a total of 20 countries, represented a 60% increase in entries since 2011. The 2014 architecture prize was awarded to the Umwelt Arena (Environmental Arena) in Spreitenbach near Zurich (2012), by René Schmid Architekten. This new construction is dominated by a prismatic folded roof with 33 variously slanted and exposed sections. The long sides are oriented along a southwest-northeast axis, but because even the north-facing surfaces are activated by sun, a total of about 5400 square metres of monocrystalline frameless glass modules generate 750 kW of power. The solar energy harvested thus exceeds the energy requirements of the arena by a factor of two. The architects have spoken of a “futuristic solar garment” whose tectonic and stylistic implementation is as persuasive from afar as up close (Figure 0.1, page 7). The Umwelt Arena marks the third time in a row that a building with a PV roof has received the architecture prize. Among the five recognition awards given in the 2014 competition, there were likewise four roof-based approaches: In the single-family house in Glattfelden (2013), Mirlo Urbano created an energy roof with stainless steel solar absorbers, photovoltaics and two roof windows in a style typical for the region (see Built Example, page 108f). Alex Buob presented a variation on the

From solar house to energetically self-sufficient building

theme “Modifying Existing Buildings” in his refurbishment of a lightly pitched roof with a complex geometric form on a Catholic church in Heiden (1963/2012, Figure 4.34, page 48), while Jourda Architectes took on the Halle Pajol in Paris (2013, Figure 6.3, page 66), where an existing steel construction has been used both as weather protection for the four-storey timber building and as an energy generating roof for a mixed-use neighbourhood. With the covering of the carport of a waste management company in Munich (2011), architects Ackermann und Partner and their engineers have broken new ground by combining pneumatically pre-stressed, multilayered EFTE cushions with flexible thin-film PV modules. The result is a thin, semi-transparent roof whose PV coverage of about 40 per cent shades the carport floor while still admitting plenty of daylight (Figure 6.4, page 66). Richter Dahl Rocha & Associés pursued an equally novel approach in the SwissTech Convention Center (2012) in Lausanne (see Built Example, page 126f) – they were the first in the world to employ dye solar cells on this scale. The combination of adaptive building shell and solar technology is illustrated well in “Rooftop”, a project submitted to Solar Decathlon Europe 2014 by students from the University of the Arts (UdK) and Technische Universität (TU) of Berlin. The project received a special prize in the SeV competition. In this prototype of a single story roof expansion in timber, the horizontal folding shutters in the facade are a special feature. Integrated into the upper half of each wooden element are two CIGS thin-film modules. When the shutters are raised, these sections become an extension of the roof, which is covered with the same modules, while the shutters themselves provide shade. Apart from the SeV competitions, the years since 2000 have seen the proliferation of a multitude of buildings featuring an exemplary integration of solar technology. In 2001, Månsson Dahlbäck Arkitektkontor employed large fields of evacuated tube collectors in the facade of the residential and office building “Tegelborgen” in Malmö’s

West Harbour (Figure 6.2, page 65). In the process of repurposing a church ruin into a tourist information centre in Alès (2001), Jean Francois Rougé covered all the front faces of the alcove-like installations in photovoltaics. The large photovoltaic glass roof above the newly created village square at the community centre in Ludesch (2005) by Hermann Kaufmann (Figure 1.19) is part of an ambitious energy and biological building concept. The architects of Busse Klapp Brüning extended the PV installations on the shed roofs of the Westphalian Museum of Archaeology in Herne (2003, see Built Example, page 116f) beyond the roof edges. The same stylistic approach was taken nine years later in the expressive roof design of the museum MUSE in Trento by Renzo Piano (2012, Figure 1.21). Commercial buildings likewise manifest a broad spectrum of solutions, ranging from Atelier niv-o’s stainless steel solar absorber facade for the autobahn administration building in Bursins (2007, Figure 5.17, page 59) to the screen-like arrangement of the solar energy systems on the outer steel structure of the zero-emissions factory in Brunswick (2002), by Banz+Riecks Architekten. In contrast, the meandering bands of thin-film photovoltaics that colour designer Friedrich Ernst von Garnier has integrated into the matte metal facade of the hot strip mill in Duisburg (2002) convey a primarily graphic image. For the World Games Stadium (2009) in Kaohsiung, Taiwan, Toyo Ito has used a serpentine steel frame as a substructure for a large solar roof with almost 9000 PV modules (Figure 1.22, page 18). The 2.5 – 3.5 metre-long modules are mounted between the steel tubing profiles of the secondary support structure so that the structure remains 1.17 Event centre “Akademie Deutscher Genossenschaften” in Montabaur (D) 2010, Architekturbüro Graf 1.18 Administrative building in Graz (A) 2010, Ernst Giselbrecht + Partner 1.19 Community centre in Ludesch (A) 2005, Hermann Kaufmann 1.20 High-bay warehouse in Coesfeld (D) 2012, Wortmann Architekten; facade design: Nabo Gaß 1.21 Museo delle Scienze – MUSE in Trento (I) 2012, Renzo Piano Building Workshop

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Introduction and history

1.22

visible from above – a design solution that is intriguing both from a distance and close up. The horizontally unfolding glass facade of the high-bay warehouse in Coesfeld (Figure 1.20, page 16) by Nabo Gaß represents another innovative approach. In the “Energiewürfel” (Energy Cube) of the public utilities building in Konstanz (2011, Figure 6.10, page 69), architect Arnold Wild has been the first to install PV modules with semi-transparent crystalline cells in triple-glazed elements of 3 – 4 metres in size. Apart from superlative examples like these, there are other projects in which a preferably small-scale module partitioning has been raised to a design principle. On the southeast corner of the Oskar von Miller Forum in Munich (2009) by Herzog + Partner, narrow frameless PV louvres have been placed on the glazed access areas. This “additive” solution enhances the otherwise somewhat busy steel and glass facade by providing it with an aesthetically and functionally persuasive emphasis. Two projects from 2015 are experimenting with new, aesthetically effective technologies in the field of photovoltaics. During the refurbishment and conversion of a coal silo in Basel (2015, Figure 7.3, page 74), baubüro has had new coloured PV modules with monocrystalline cells installed on the roof as well as on the southern and northern facades. On the roof of the German pavilion at EXPO 2015 in Madrid, the firm Schmidhuber has erected a row of shade-giving “Solar Trees”, whose hexagonal “leaves” consist of foil modules with organic solar cells. The Aktiv-Stadthaus (Active City House) in Frankfurt-amMain (2015) by HHS Planer + Architekten (Figure 1.23) is groundbreaking in that it embodies a logical combination of conceptually diverse requirements. The eight-storey residential and office building, built on a ground plan only eight metres wide, covers the complete energy needs of its residents thanks to 2400 square metres of photovoltaics on the single pitch roof and on the southern facade. A 250 kWh storage battery captures and supplies over 50 per cent of the required building power. On the approximately 150-metre-long south facade, custom-made 18

monocrystalline PV modules alternate with the window openings. The cited examples show that solar technology systems have by now become self-evident components of innovative building shells. However, work remains to be done in the area of existing building renovation. Today’s approaches, for the most part, remain design and construction variations on established themes from the 1990s. Innovations in cell development as well as significantly expanded options in component dimensions, frame profiles and coverings will likely stimulate further growth potential. A great many contributions are characterised by high ecological ambitions, and zero and plusenergy concepts are increasingly joined by approaches to energy self-sufficiency.

The actors in solar construction Over the past three-and-a-half decades, architects, engineers and building clients have created a large number of outstanding examples for the building-specific application of solar energy, in a spectrum spanning singlefamily houses, administrative and industrial buildings and solar housing developments. These include new construction as well as refurbished buildings of (almost) all ages. The exemplars that have won awards or that have been featured in architecture magazines earn widespread praise beyond expert circles and are perceived as “beautiful” in the broadest sense of the word. A common critique, however, centres on the fact that the solutions depicted are far removed from the everyday (financial) reality of many owners of single-family and semidetached homes. What are the reasons for this discrepancy? First and foremost, it is evident that a dwindling number of architects are engaged with the design and implementation of small home construction. This is one of the main reasons that solar technology is often employed in a very simple non-integrated form. As a consequence, the enormous potential for utilising the roof and facade

Conclusions and outlook

surfaces of single-family and semi-detached houses remains largely untapped. Designers, too, have a lot of catching up to do. To achieve an increase in the quality of building-integrated solar technology in everyday architecture requires the input of competent decision makers. This refers particularly to architects, which means that the profession must grapple more intensively with the future task of designing energetically optimised buildings. Already in the fall of 2009, the conclusion reached at an international conference was that “building-integration of photovoltaics fails thanks to architects” [20], and even today, questions such as why so few architects work with PV – especially when it comes to facades – arise from the solar sector. Twenty years ago, in his editorial in the magazine glasforum, architect Dieter Schempp wrote, “During my visit to the Architecture Biennale in Venice I was forced to the conclusion that solar and ecological building were of no interest there.” [21] Similarly, when Rem Koolhaas and his science team toured the exhibit “Elements of Architecture” in the central pavilion of the 2014 Architecture Biennale in Venice, they were baffled by the fact that (active) solar energy use was not even hinted at in either the “roof” or “facade” exhibit topics. This is an unfortunate but by no means isolated occurrence, since solar technology often plays no role in architectural conferences and discussions. Action must not be limited to architects. Manufacturers would be wise to demonstrate greater flexibility, for example in a willingness to be open to adaptations in system configurations. Private and public building authorities acting as building clients must in turn demand stylistically persuasive solutions from the designers.

Conclusions and outlook In building-integrated solar technology it is important not only to fulfil quantitative goals, but to meet qualitative demands as well. Part of this challenge involves transferring the concepts of the “lighthouse” and pilot projects shown here into everyday building practice. In this process there is a set of fundamental design principles to fall back on, which are discussed in the chapter “Integration of Solar Installations” of this text, and elsewhere. Ultimately, however, building-integrated solar technology projects must always be examined on a case-by-case basis, in which the local climatic and constructive boundary conditions must be taken into account. This requires not only structural and physical knowledge but also creative and stylistic competence. Integrating the components into the building shell in a functionally efficient and structurally sound way is not enough; they must also be fully incorporated into an overall design concept. The transformation of buildings from energy consumers to “energy collectors” is thus not merely an ecological imperative and a technical challenge, but a matter of building culture as well. And it applies to new constructions and refurbishment projects in equal measure.

Notes [1] cf. Krippner, Roland: Die Gebäudehülle als Wärmeerzeuger und Stromgenerator. In: Schittich, Christian (ed.): Gebäudehüllen. Munich / Basle /Boston /Berlin 2006, page 47f [2] “Architektur muss die Beherrschung der neuen Materialien lernen, darf aber dennoch die Vergangenheit nicht aus den Augen verlieren.” Pawley, Martin: Theorie und Gestaltung im zweiten Maschinenzeitalter. Bauwelt Fundamente, Bd. 106. Braunschweig / Wiesbaden 1998, pages 72ff [3] Urbanek, Axel: Fünfzig deutsche Sonnenhäuser. Ausgeführte Solaranlagen aus den Jahren 1974 bis 1978. Gräfelfing 1979, page 6 [4] “Trotz Automatisierung ist häufig noch Handarbeit gefragt” (VDI Nachrichten, Nr. 3 22.01.1999, page 3). 16 years later this has remained basically unchanged. [5] Henning, Hans-Martin; Palzer, Andreas: 100 % Erneuerbare Energien für Strom und Wärme in Deutschland. Freiburg 2012, pages 4f [6] “Sun Furnace in your Attic”; cf. Denzer, Anthony: The solar house. Pioneering sustainable design. New York 2013, page 122 [7] cf. ibid. page 134 [8] Daniels, Klaus: Sonnenenergie. Beispiele praktischer Nutzung. Bericht über eine Studienreise 1975. Karlsruhe 1976 [9] see note [3], page 5 [10] cf. among others Hullmann, Heinz; Schmidt, Baldur: Solar-Kollektoren. Ansätze für die Integration in Gebäuden. In: DBZ – Deutsche Bauzeitschrift, 24. Jg., 4/1976, pages 437– 441, and Jesorsky, Reinhold: Zunehmende Integration der Solaranlage in den Hochbau. In: HLH – Heizung Lüftung/Klima Haustechnik, 29. Jg., 7/1978, pages 279 – 281 [11] Herzog, Thomas (ed.): Solar Energy in Architecture and Urban Planning. Solarenergie in Architektur und Stadtplanung. München / New York 1996, page 74 [12] cf. among others: Weber, Helmut: Integration von Solaranlagen in Gebäuden. In: DBZ – Deutsche Bauzeitschrift, 25. Jg., 2/1977, page 207f., pages 46 – 49; Hullmann, Heinz: Anforderungskriterien im Sinne einer bautechnischen Affinität für Energiedächer. Habilitationsschrift. Hannover 1984 [13] cf. Hullmann, Heinz: Solarenergie-Anlagen und Gebäude. Dissertation. Hannover 1977 [14] cf. Bossel, Ulf: Planung von Solaranlagen. In: Deutsches Architektenblatt, 17. Jg., 3/1985, pages 315 – 318 [15] Behling, Sophia; Behling, Stefan: Sol Power. Die Evolution der solaren Architektur. München u. a. 1996, page 220 [16] cf. among others: Das Multitalent Photovoltaik. In: Multifunktionale Photovoltaik – Photovoltaik in der Gebäudehülle. Hamburg / Kassel, März 2006, pages 23 – 27 [17] cf. among others: Sick, Friedrich; Erge, Thomas (ed.): Photovoltaics in buildings. A Design Handbook for Architects and Engineers. London 1996, pages 91–105 [18] Hegger, Manfred: Photovoltaik und Architektur – integrative Lösungen. In: glasforum, 46. Jg., 6/1996, page 43 [19] https://www.sev-bayern.de (July 3, 2016) [20] http://www.enbausa.de (May 28, 2016) [21] glasforum, 46. Jg., 6/1996, page 2

1.22 World Games Stadium in Kaohsiung (RC) 2009, Toyo Ito, Takenaka, RLA Kaohsiung Main Stadium Design Team 1.23 Aktiv-Stadthaus (residential building) in Frankfurt (D) 2015, HHS Planer + Architekten

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Buildings as catalysts for energy transformation

Thomas Seltmann

• From energy transition to energy transformation • The energy sectors merge • Solar technology as a design challenge

From energy transition to energy transformation

The fossil fuels oil, coal and natural gas as well as uranium are mined in largely remote locations under questionable environmental conditions, and are converted with high losses into usable forms of energy. In this process, a third of the energy contained in the raw materials is lost. The most unfavourable energy-tocost ratio is that of nuclear power: the future expenditures for the dismantling, storage and monitoring of the nuclear waste over millennia will undoubtedly exceed the few decades’ worth of benefit – not to mention the risks inherent in the operation of the power plants and the waste disposal facilities. In contrast, in Germany the sun delivers more than a thousand kilowatt-hours of energy per square metre of built surface area every year free of charge. Metaphorically speaking this is equivalent to the energy content of 100 litres of premium petrol raining down in the form of daylight. Multiplying this by the area of Germany, it amounts to 80 times more energy than is actually consumed there per year. On paper it would be enough to convert just over 1 % of this into electricity and heat in order to meet the complete energy needs of the country. Savings and efficiency have not even been factored into this calculation. What could be better suited to harvesting this heavensent energy windfall than the large external surfaces of buildings? The vehement political discussions centring on the energy transition and on climate protection have also led to increased demands in recent years for greater energy efficiency and more solar energy utilisation in buildings. If all the energy consumed by the transportation and the business and industry sectors were set aside, the largest remaining energy consumers would be buildings, with their heating and electricity needs. Almost half of the

“Solar architecture is not about fashion – it is about survival.” Norman Foster The term “energy transformation” encompasses more than just the often debated energy transition. In the media and in public discourse, the treatment of changes in our energy supply is often narrowly centred on the electricity sector. In energy research, the term transformation is used instead of transition whenever the subject is the conversion from a fossil-fuel and nuclearbased energy system to renewable, inexhaustible sources. From the perspective of the energy industry, renewable energies and their production methods are not simply “additive” or “alternative” energy sources, as they are still sometimes dismissively described. Instead, they form the completely new foundations of our energy supply.

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The merging of energy sectors

energy expended in Germany goes into supplying buildings with heat and electricity. Pioneers of the 1990s

The first energy-independent solar house in Germany had an impact like that of a recently landed spaceship in a science fiction movie. The house was designed by solar pioneer Adolf Goetzberger in the institute that he founded, the Institute for Solar Energy Systems (ISE) in Freiburg, and built in 1991 in collaboration with architects Hölken & Berghoff (Figure 2.1). The building was a structural exclamation point, promoting both the paradigm shift in energy-efficiency, for which demand was already on the rise, and renewable energies. Politicians would however require another two decades to give the transformation a proactive spin by labelling it with the programmatic phrase, invented years before, of “energy transition”. In the interim, in 2000, the German Bundestag passed an internationally trend-setting subsidy law. The Renewable Energy Sources Act (EEG -- Erneuerbare-EnergienGesetz) gave renewable power sources legal precedence over fossil-fuel and nuclear power plants for the first time, and supported this further through a feed-in compensation that made the nationwide operation of photovoltaic and wind power plants economically feasible. After its first amendment in 2004, the EEG began to differentiate between freestanding facilities and solar modules installed on buildings. Lawgivers were quick to recognise the latter as the more sensible approach. The goal of the law was to make the consumption of renewable energies competitive on the energy market by taking advantage of the cost savings of mass production. This goal was achieved sooner than even its proponents had thought possible. Owing in part to subsidy laws, based on the German EEG, that have been adopted in more than 60 countries worldwide, more money is now invested in new solar and wind power plants annually than in conventionally fired facilities. In Germany, research has long progressed beyond dealing only with the use and improvement of individual technologies. Even the ISE in Freiburg, which has now been integrated into the Fraunhofer Consortium, looks far beyond the supply of individual buildings with solar

energy. Within the Renewable Energy Research Association (FVEE -- Forschungsverbund Erneuerbare Energien), the ISE and its partners are developing scenarios for the already mentioned transformation of the energy system. The merging of energy sectors According to researchers, in this effort it is essential to think beyond individual energy sector boundaries. Furnishing all energy needs through renewables is made easier and cheaper if the electricity, heating and transportation sectors are no longer kept separate from one another. Energy will in this scenario be transferred between modalities; in the energy system of the future the harvesting, storing and utilisation of energy will be solved via sector-spanning task sharing. The old one-way street from mine to consumer will no longer exist. Infrastructure facilities are increasingly serving multiple functions in the new energy world. Buildings, for example, must not only be made more efficient, but must also be equipped to harvest and store solar energy. Even the electric car sitting in the garage can become a significant part of the supply infrastructure if its battery is connected to the public network as a storage device (Figures 2.2 and 2.4, page 23). Here is a little example calculation: The Tesla Model S, an electric car, reaches its maximum distance of up to 500 kilometres on a single charge with a 90 kWh capacity battery. If half of all German passenger cars were equipped with a battery of this size, and furthermore, if half of these cars (and their cumulative battery capacity) were available at any given time to draw on or contribute to the electricity network, then this decentralised energy storage would be large enough to store and deliver half of Germany’s daily electricity needs. This alone would largely safeguard the everyday balance between generation and consumption for a very high 2.1 Energy self-sufficient solar house, Freiburg (D) 1992, Planerwerkstatt Hölken & Berghoff: Research and Demonstration Projects of the Fraunhofer Society 2.2 Aktivhaus B 10, Stuttgart (D) 2014, Werner Sobek. The research project generates twice its own energy requirements and supplies, among other things, two electric cars.

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Buildings as catalysts for energy transformation

proportion of sun- and wind-generated electricity. The example serves to illustrate how valuable the coupling of different energy sectors – in this case, transportation and electricity supply – could be. The electric car is also the perfect example for how pointof-consumption generation and the switch to electricity consumption can reduce the overall energy requirements of the system. With an efficiency of over 90 %, electric motors are three to four times as efficient as combustion engines. As a model project in the Netherlands shows, even the streets themselves could become energy suppliers if they were covered with photovoltaic modules (Figure 2.3). A growing responsibility for architects as well

If this vision and other, as yet unforeseen ideas were to become a reality, the design responsibilities of infrastructure planners and architects would grow enormously. Local solar heat distribution networks, which have so far often failed to be realised because their design has been focused on individual buildings, are a typical example of how the thinking and planning of the future will have to be broader in both scale and perspective. The energy industry has already coined the term “prosumers” for the image of the new multifunctional and bidirectional energy market participants. A prosumer is a consumer who not only consumes energy, but simultaneously or alternately functions as an energy producer for his own or for others’ use. A prosumer can also store energy or take over coordination or management tasks within decentralised supply units. The exact form that the division of labour between the various design levels will take is as yet completely open. What is clear, however, is that the hierarchical structure from individual building to city district to region, up through the international energy markets, will be more or less disrupted by the energy supply structures of the future. Centralised or decentralised – or both?

How self-sufficient will houses and factories of the future be? Will solar and wind-generated power be stored in basements and electric cars, or in municipal batteries? Will entire regions cut themselves off from the energy network, or will the trans-regional

exchanges of energy surpluses and storage capacities represent the optimal way to ensure a reliable and inexpensive supply? Will surplus energy from German wind farms be stored in Norway’s mountain lakes? Models for all these scenarios can already be viewed in Germany. And usually the conditions specific to each individual case determine which concept will function best. The examples of photovoltaics and batteries demonstrate that the technical components can be combined to form units of very different sizes with virtually no efficiency losses. In general, the manufacture of system components becomes less expensive as the number of units increases, whereas the complexities of conceptual work and of individual designs tend to grow with project size. The importance of considering connections across sectors and on many levels concurrently is illustrated in the studies being done by the Fraunhofer ISE [1] and the FVEE (Renewable Energy Research Association) [2] on the transformation of the German energy industry. In an evolutionary process, these research efforts are showcasing the technical and economic possibilities of an energy supply from renewable energies, and developing paths to its implementation. Technical structural change requires societal acceptance

One of the most exciting conclusions of all this is that, after the transition process, renewable sources will supply us at least as reliably -- and at similar cost – as fossil fuels and atomic energy have to date. When external costs and the increasing scarcity of raw materials are taken into account, they are probably even less expensive. However, research studies and the current developments in large energy companies also reveal that the transformation is not just of a technological nature, but is also shaking the foundations of familiar economic structures. If the economic structures are to change successfully in response to the technological changes, it is crucial that the energy transformation gains and maintains societal acceptance. The protests against the rail project “Stuttgart 21” and regional citizens’ initiatives against wind farms demonstrate that citizens must be included in the decision making and planning process. Sometimes conflicts arise over a single photovoltaic installation, because a neighbour is blinded by its reflections on sunny days.

Solar technology as a design challenge Twenty-five years after the ISE in Freiburg many architects and designers have accepted the new challenge, and are countering the initially somewhat technophile aesthetic of the solar scientists with more aesthetically successful integrations of solar installations – even into historical monuments and ensembles. Solar technology can be unobtrusively but functionally incorporated into existing buildings, just as historically listed church roofs, the Berlin Reichstag, or other exemplary refurbishment 2.3

22

Solar technology as a design challenge

2.4

2.5

projects have shown. But solar technology can also be employed as a deliberate design element of modern and contemporary architecture. Through its sponsorship of several architectural competitions, the Bavarian Association for the Promotion of Solar Energy has brought together a large number of exciting examples in which solar technology is not an “add-on” feature of a conventional building, but functions as an integral design component. The examples show that the issue is not just a matter of adopting a new technology into customary building methods. Solar technology can expand the vocabulary of architecture to encompass interesting new forms of stylistic expression (Figure 2.5). In everyday architecture, the question is not so much whether it is necessary to forego traditional roof landscapes to protect the climate as it is why so few building clients in Germany have adopted a solar facility that blends harmoniously into the building and its surroundings. In Switzerland or France, for example – where integrated solar installations are more attractively promoted – the situation is quite different.

requirement for the operation of such a building is already almost zero, and most of that is covered by renewable energies and ambient heat from the building property itself. Denmark is one country at the vanguard of the energy transformation, and does not shy away from prohibitions. Since 2013, the installation of oil and gas furnaces in new buildings has been forbidden, and starting in 2016 new oil furnaces cannot even be installed in existing buildings, providing that these have access to district heating or natural gas networks. In June of 1997, Adolf Goetzberger, solar research pioneer and founder of the Fraunhofer Institute for Solar Energy Systems in Freiburg, declared solar energy to be the energy of the people. The European Commission and the EU parliament want to allow citizens to take on more responsibility for the energy supply and to strengthen their rights as “prosumers”. The responsible conversion of these rights into practice requires not only clear and supportive parameters, but most importantly skilled advice and planning. Only this will allow an effective energy transformation to emerge from the possibilities that exist in a new energy world. Successful solar architecture makes solar energy accessible for citizens, but beyond that it creates sustainable living spaces for people. It will provide the daily living and working worlds of the future with a fresh face.

On the path to the Plus Energy building

The rapid development of solar technology is driving rapid price decreases and a growth in new application possibilities. Unfortunately, however, fully developed products that would allow for its aesthetically pleasing integration into buildings are still a scarce commodity, or very expensive. The solar industry has thus far sorely neglected the essential advantage of its technology, namely its functional and stylistic integration into existing or new infrastructure. In the political sphere some progress in this regard has already been made. Even now, the Energy Saving Ordinance contains elements that not only require a reduction in energy consumption, but also stipulate how energy is to be generated and used; and these questions have long been part of the political discourse. Controversies centre not so much on “if”, but rather on “when” building clients should be obligated to comply. A guideline of the European Union is now in effect stipulating that any buildings constructed in or after 2021 must conform to a “nearly zero energy” standard. The energy

Notes [1] Hans-Martin Henning, Andreas Palzer: Was kostet die Energiewende? Wege zur Transformation des deutschen Energiesystems bis 2050. Freiburg 2015 [2] ForschungsVerbund Erneuerbare Energien (ed.): Forschung für die Energiewende – Phasenübergänge aktiv gestalten. Berlin 2015

2.3 Laying of the modules for the electricity-generating bicycle path in Zaanstad (NL) 2.4 Efficiency House Plus with electromobility, Berlin (D) 2012, Werner Sobek. A total of 22 kW of power from installed PVs (8 kW from the facade) generates more energy than the owners use, including mileage of 30,000 km/year. 2.5 “Smart is green” Case Study House for the IBA, Hamburg (D) 2013, zillerplus Architekten und Stadtplaner: The solar thermal collectors installed as fascia, and on the roof, provide warmth for hot water and heating. Photovoltaic modules in the balcony parapets generate electricity, including for a car charging station.

23

Physical and geometric principles

Gerd Becker

• Foundations of solar energy use • Design tools

Foundations of solar energy use

The strength of the incoming solar radiation depends heavily on the time of year (Figure 3.1). The seasons are a consequence of the fact that Earth’s axis of rotation is tilted with respect to its orbital plane (ecliptic) around the sun. The angle of the tilt, or declination, varies cyclically over several tens of thousands of years, but for the purposes of building design, it can be assumed to be constant at 23.45°. In June, when the sun shines predominantly in the northern hemisphere, it is summer in Europe, Asia and North America. Conversely, the southern summer falls between November and February, when the southern hemisphere is more oriented toward the sun. In Munich, on June 21, the sun reaches an elevation of 66° above the horizon, but on December 21 it peaks at 19°. In winter, therefore, the sun’s radiation not only follows a much flatter trajectory but must also traverse a much longer path through the atmosphere. This weakens it even further. Due to Earth’s elliptical orbit around the sun as well as its declination and rotation about its own axis, rays from the sun strike objects on the Earth’s surface at different angles depending on the season and time of day. The incident directions can be described using the solar azimuthal angle αS (the sun’s angular departure from the north-south axis) and the sun’s elevation angle γS (Figures 3.2 and 3.3). There are complex mathematical equations with which to calculate the elevation and azimuth, but it is more practical to employ sun path diagrams. These charts are available for many locations and make it easy to determine sun elevation and azimuth for any given date or time. The internet is another source of sun path diagrams for any desired location, and corresponding software [1] is just as freely available (Figure 3.3).

Solar energy on Earth occurs in direct (radiation) and indirect (e.g., wind energy) forms. For buildings, the radiation represents a particularly significant energy source. It can be used both actively and passively. Passive and active applications

Passive use describes the employment of specific structural measures to collect, store and distribute incoming solar radiation, generally without the use of technical installations. Active use encompasses all technical measures that are utilised for the capture, distribution and, at times, storage of solar energy. There are two different types of active use of solar energy to distinguish: solar thermal energy and photovoltaics (PV). In solar thermal energy, collectors convert solar radiation into heat; in contrast, PV modules use it to produce electricity. The energy yields of these systems are primarily influenced by local conditions and can vary strongly with geographical location. Secondly, the inclination angle and the exposure of the installations themselves determine energy yields. In these cases, the differences between solar thermal and photovoltaic systems must be taken into account. Sun elevation and solar azimuth

Earth’s elliptical orbit around the sun takes one year. The Earth-sun distance varies slightly between 0.983 and 1.017 astronomical units (AU; 1 AU = 149.6 million kilometres, which represents the average distance from the Earth to the sun). In addition, the Earth rotates around its own axis once per day. This creates the daytime variations that have a significant influence on the use of solar radiation. 24

Foundations of solar energy use

Spring in the northern hemisphere

Solar power and energy

Nuclear fusion processes occurring in the sun’s interior generate energy in the form of electromagnetic radiation. The wavelengths of this radiation range from 10 – 20 metres to several kilometres. The power at the sun’s surface measures 62.5 MW/m2, which corresponds to a temperature of 5777 K. Since this power is radiated outward into space in all directions, only a tiny fraction of it arrives on Earth. No losses occur in the journey through the vacuum between the sun and the Earth. The incoming power density of the radiation that reaches the upper edge of the atmosphere is known as the solar constant. Because of Earth’s elliptical path about the sun, and because of the resulting time-dependence of the sun-Earth distance, the solar constant varies very slightly. Its median value is 1367 W/m2. On its way through the atmosphere, the sun’s radiation is reduced by reflection, absorption and scattering. The cumulative effects of these depend on how far the sunlight must travel through the atmosphere, which is expressed by the air mass coefficient (AM). Radiation striking the atmosphere from the outside has not yet traversed any air, so its AM coefficient is zero. On the equator the value is AM 1.0, while in central Europe it is AM 1.5. The composition of the sunlight – its spectrum – depends on the air mass, or density of the air (Figure 3.4).

Summer in the northern hemisphere

June

N March Winter in the northern hemisphere

Autumn in the southern S hemisphere

N

N December Sun

S Winter in the southern hemisphere

Autumn in the northern hemisphere

S N

Spring in the southern hemisphere

September S

Summer in the southern hemisphere

3.1 Zenith North

S S

Sun elevation S

Solar azimuth (from the north or south) South 3.2 West

Typical power/energy values of annual solar radiation

Meridian

North

Elevation angle γS Sun paths a

South c

b

Azimuth αS

East

2.25

UV Light

2.00 1.75 1.50 1.25

Direct and diffuse solar radiation AM1.5; ASTM G173 Global radiation on a surface located opposite the zenith and tilted at 37°; AM1.5; ASTM G173; 1000 W/m2 Extraterrestrial radiation; AM0; ASTM E490; 1367 W/m2 Spectral sensitivity according to DIN 5031-1

1.00

100 80

Infrared 3.1 Position of the Earth with respect to the sun in different seasons 3.2 The incident angles at which solar rays strike an object are described by the solar azimuthal angle and the solar elevation angle 3.3 Seasonal sun path at 50° northern latitude a June 21 (summer solstice) b March 21/September 21 (equinoxes) c December 21 (winter solstice) 3.4 Extraterrestrial (AM 0) and global (AM 1.5) spectrum of sunlight. The energy content of the radiation depends strongly on wavelength.

0.75

60

0.50

40

0.25

20

0

Spectral sensitivity [%]

3.3 Radiation intensity [W/(m2·nm)]

For reasons already described, the solar radiation on the Earth’s surface (global radiation) is smaller than the solar constant. Its median value is 1000 W/m2. The global radiation can be divided into three main parts: direct radiation, indirect radiation (diffuse radiation) and a smaller component that stems from reflections from the surrounding environment. In central Europe, more than 50 % of the total annual radiation consists of diffuse radiation (Figure 3.8). The effects of haze in urban and industrial regions increase this percentage further. For technical use however, the decisive factor is primarily the direct radiation percentage, though to a limited extent, diffuse light is also converted to energy. In physics, the equation relating energy and power is given by energy = power ≈ time interval. Therefore, the solar energy available per year or per month at any given location is the sum of the products of all momentary radiation power levels and their associated durations. For every location on Earth there exist typical solar energy values that vary from year to year (about ±10 % in

0 280 600

1000

1400

1800

2200 2600 Wavelength [nm] 3.4

25

Global radiation [W/m2]

Physical and geometric principles

1200

Germany). Relative geographical position also causes small changes in the German values; in general, south of the Main they are higher than farther north. In 2014, for example, the German Weather Service (DWD) determined a value of 1152 kWh/m2 for Munich, 1131 kWh/m2 for Würzburg and 1059 kWh/m2 for Hamburg. A longer term forecast of radiation data, that is to say, a prediction of the amount of solar power expected on a particular day, is practically impossible (Figure 3.5). The amount corresponding to an entire year, however, can be projected astonishingly accurately. Even the monthly values, though less exact, are quite indicative. The charts of the German Weather Service are one method for obtaining a rough estimate of radiation data (Figure 3.7). Radiation atlases and relevant software tools are also readily available [2].

1000

Solar radiation supply

1200 1000 800 600 400 200 0 00:00

12:00

00:00

12:00

00:00

Global radiation [W/m2]

a

800 600 400 200 0 00:00

12:00

00:00

12:00

b

00:00 3.5

Direct radiation

Diffuse radiation

Reflected radiation Shading by surrounding vegetation

Shading by surrounding topography

Emitted infrared radiation

Shading from neighbouring buildings 3.6

3.5 Level of global radiation on two successive days on a 28° inclined module surface in Munich-Riem: a in summer b in winter In each case the first day is sunny, with light cloud cover only in the morning. The global radiation energy on the summer day is 7.8 kWh/m2 while in winter it is 1.8 kWh/m2. The following day is characterised by heavier cloud cover, and here the global radiation energy measures 3.3 kWh/m2 in summer and 0.8 kWh/m2 in winter. 3.6 Schematic illustration of the sun exposure of a housing development 3.7 Global radiation map of the German Weather Service (1981 – 2010) 3.8 Daily average radiation intensity using central Germany as an example 3.9 Dependence of the solar yield (PV) on exposure and inclination

26

Throughout the course of the day and the year, solar radiation undergoes extremely large fluctuations and is strongly impacted by the prevailing local weather conditions. Incoming radiation can differ from one day to the next by a factor of ten, and on a clear summers day it can reach a value 25 times higher than on a cloudy day in winter (Figure 3.8). In addition, the solar energy supply in central Europe is markedly shifted on a daily as well as on a yearly basis with respect to heating and electricity demand. Short-term shortfalls can be offset through the use of batteries. In contrast, seasonal fluctuations present a significant problem: in Germany, about three quarters of the annual solar radiation supply is delivered in the summer half of the year; the only way to stockpile this harvested energy is by way of very expensive underground storage facilities. These constraints on availability can impose technological and economic limits on the use of solar energy. Its practical implementation in buildings is determined by two important parameters: the exposure of the surface, i.e., its orientation direction as well as its inclination angle; and the absence of shade. Daily and seasonal fluctuations and shading from trees or other buildings must be taken into account in determining the power and yield prognoses (Figure 3.6). If the solar modules are tilted towards the sun, the solar yield can increase. In Germany, orienting the array to the south and inclining it at an angle of about 30° will net about 10 % more energy than the horizontal equivalent (Figure 3.9). On the other hand, the more the exposure deviates from a southerly direction, the smaller the solar yield (Figure 9.10, page 98). The energy yield increases further if the solar modules actively track the sun; in Germany the gain in this case is about 20 – 25 % compared to that of solar radiation on a horizontal surface. Shading losses

In the real world, completely shade-free surfaces are very hard to find. Shade can cause significant losses in usable solar energy. Trees, bushes, buildings, masts and power lines, as well as other obstacles, all cast shadows

Foundations of solar energy use

on surfaces that are exposed to sunlight. These shadows change as the sun’s position changes: that is to say, with solar elevation and azimuth. Certain measuring instruments can give a quantitative approximation of shading losses. The instruments record the obstacles on the scene and calculate the annual losses on the basis of the relevant sun path data. Simulation software is also useful in the consideration of obstacles. The programmes run calculations to determine the amount of shade and the reductions in global radiation that are to be expected for each time interval over the course of a year. The sum of the reductions from all sources yields the annual energy losses. In the design phase, it is important to ensure that shading is minimised and that the angles of incidence are optimised for both summer and winter.

Kiel Rostock Hamburg Bremen Hanover Münster

Berlin

Essen

Leipzig

Kassel Cologne

Dresden

Frankfurt Trier

Nuremberg Stuttgart Ulm Freiburg

< 950 kWh /m2a > 950 kWh /m2a > 1000 kWh /m2a > 1050 kWh /m2a > 1100 kWh /m2a > 1150 kWh /m2a

Passau Munich

3.7

Numerous simulation programmes are available on the market to aid in the design of solar installations [3]. They include radiation data banks with global radiation values, and regional temperatures for many locations throughout the world. After the technical specifications of the solar installation and its components, as well as their integration and shading details, are entered, the programmes calculate by time increments what energy yield is expected for that increment. The sum of all the individual incremental energy gains over the year represents the annual energy yield. Most of these design tools have convenient user interfaces and are easy to work with after a brief familiarisation period. A simple model for a specific installation can be generated by varying the building integration parameters and the technical data. The design tools offer an initial feasibility estimate for the utilisation of solar energy at a specific location with selected technologies and a fixed system configuration. In the next step, they supply yield prognoses generated on the basis of highly resolved weather datasets drawn from various sources. In addition, the programmes allow for a focused analysis of individual aspects of solar installations (e.g., elevated horizons, self-shading, shading analyses and 3-D representations).

Irradiation [kWh/m 2/day]

Design tools

5 4 Direct radiation 3

2 Diffuse radiation 1 0 J F Winter

M

A

J J Summer

M

A

S

O

N D Winter 3.8

Inclination 90° 60° West

30° East

South 90–100% Notes [1] Examples include PVGIS, the “Photovoltaic Geographical Information System” of the EU (http://re.jrc.ec.europa.eu/pvgis/apps4/pvest. php), www.sunearthtools.com which contains a multitude of simulation possibilities; and also software for lighting design such as Relux, Sunrays or the Sun Surveyor app. [2] Apart from the German Weather Service (DWD), other examples are Meteonorm and PVGIS. Global data on solar radiation can be found on the NASA Surface Meteorology and Solar Energy Database, but NREL und NOAA also contain information based on satellite data. [3] For example, the programmes Meteonorm and PV*SOL. Meteonorm is software that provides meteorological information and includes weather data from all over the world. PV*SOL is used for the simulation and interpretation of the operational performance of photovoltaic installations worldwide, and it has an extensive radiation data bank. For the evaluation of solar thermal installations T*SOL can be used instead.

80–90%

70–80%

60–70%

50 – 60 % 3.9

27

Technology and systems – photovoltaics

Ralf Haselhuhn

• The functioning of photovoltaic installations • Solar cells and photovoltaic modules • Inverters as system headquarters • Battery storage systems • Planning and design • Installation, commissioning, operation and maintenance • Requirements, standards and regulations

The functioning of photovoltaic installations

would have to be placed on the number of installations feeding into the grid in the future. Therefore, designers must ensure that at noon in summer, as much solar electricity as possible is used in the building if the installation is not linked to a battery. The utilisation of east or west-facing arrays can also be quite practical, as these lower the noon peak, and instead produce more solar electricity in the morning or afternoon. In Germany, most PV arrays are installed on rooftops or integrated into facades. This marks a big advantage over other technologies that generate electricity from renewable energies: PV installations can become a part of the building, and they provide additional uses such as weather or sun protection – or, in conjunction with storage solutions, load-balancing functions. Grid-independent PV installations (stand-alone systems) are primarily employed in regions of the world where there is no widespread electricity grid. In general they are now more cost-effective than an electricity supply

A photovoltaic (PV) installation generates electrical energy from solar radiation. Its main component is the PV generator, built up of modules, which in buildings is mounted onto roof or facade surfaces. PV installations are divided into two types: grid-connected and standalone installations. In 2015, grid-connected PV installations (Figure 4.1) generated more than 6 per cent of all the electricity in Germany. The world-wide generating capacity in 2015 was about 40 gigawatts, which corresponds to about 320 million square metres of module area. The larger the proportion of fluctuating sources from wind and solar electricity in the power grid, however, the more important the temporal correspondence between demand and supply. Solar electricity generation in Germany reaches its peak at noon on a sunny summer day. If consumption during that time is small, as on a weekend for example, a limit 4 Inverter with optional data acquisition system 5 AC wiring

1 PV generator 2 DC wiring 3 Main DC switch

1

9 Connection to the grid 10 Optional battery storage system

6 PV energy meter 7 Feed-in meter 8 Consumption meter

1 2

2

8 3

kWh 7

4

=

3

5

~

10

9

kWh Maximum feed-in

4

= ~

9 6

7

kWh

kWh kWh

5

8 Self-consumption 4.1

28

The functioning of photovoltaic installations

from a diesel generator, for example. Stand-alone installations are designed to provide users with electricity reliably for one or more days. In small solar home systems the electricity is often used directly, for example for lighting. Increasingly however, stand-alone systems are being built to provide alternating current, which in turn necessitates an inverter. In many developing countries, PV stand-alone installations are the most practical means of providing electricity. In addition to stand-alone installations in regions far from a utility grid, such as in the Alps or on islands, German-speaking countries are building projects in locations with a good electrical network as well, some of which are even in the commercial sector. The motivation for this is a stable and economically attractive energy supply based on ecologically sound principles. Though the initial investment for these installations exceeds that for the classic grid-connected energy supply system, the savings in operational energy costs makes them profitable in the long term. Case study 1: Energy factory in Neuenstadt

The energy for this 950-square-metre energy self-sufficient industrial building (Figure 4.3) is drawn entirely from renewable sources: photovoltaics and biogas. The PV installations on the facade and roof generate 112 kilowatts of power; and combined with a 400 kilowatt-hour storage capacity lead gel battery system, this corresponds to about 80 per cent of the overall energy demand. Two biogas cogeneration plants of 20kilowatts power each deliver electricity and heat when the sunshine is insufficient. The redundancy of the cogeneration units also guarantees a backup energy source during times of maintenance or in case of failure. Heating and cooling are provided by three variablepower heat pumps as well as hot and cold reservoirs. Control and regulation employs a specially designed energy management system to utilise the most economical energy source at any given time. Heating and cooling demands are determined using a webbased weather forecast: and the room temperatures, adjustable loads and the optimised charging of electric cars via three charging stations are managed accordingly.

4.2 Case study 2: Energy self-sufficient multi-family residence in Brütten

This residential building for nine families (Figure 4.2) is the first of its type in the world to manage without external connectivity to electrical, oil or natural gas supplies. Its shell consists entirely of matte photovoltaic modules which deliver an annual electrical output of 90 - 105 megawatt-hours. About 70 per cent of this energy comes from the 512 square-metre roof-integrated 79.5 kilowatts peak array of monocrystalline silicon cells. The remaining 30 per cent is produced by the 485 square-metre 47.0 kilowatts peak facade installation of thin film modules. Heating is provided by a 28 kilowatt water-to-water heat pump coupled to two 338 metre-deep geothermal probes. The house has three energy storage facilities: a 192 kilowatthour lithium iron phosphate battery for short-term storage; a power-to-gas installation with an electrolyser, a 120-cubic-metre hydrogen tank and a fuel cell for longterm storage; and two 125-cubic-metre hot water storage tanks in the ground beneath the house.

4.1 Grid-connected PV installation consisting of generator and system technology for the feed-in and self-consumption of solar electricity 4.2 Multi-family residence in Brütten (CH) 2016, René Schmid Architekten; Design of PV installation and battery: Basler & Hoffmann; Building services: Pro-Energie; Building client: Umwelt Arena Spreitenbach 4.3 Energy factory in Neuenstadt (D) 2014, Weller Architekten (design); Riemer Planung (factory planning); Energy design: Widmann Energietechnik; Building services: New Energy Solutions; Building client: Widmann Energietechnik

4.3

29

Technology and systems – photovoltaics

Seal

Aluminium frame

Solar cells and photovoltaic modules Glass EVA composite

Solar cells

Reverse side foil of synthetic composite 4.4 +

Efficiency records [%]

Solar glass PVB foil /cast resin Cell layer PVB foil /cast resin Backing glass

–

Solar glass Cell layer Reverse side foil composite

Solar glass Cell layer Reverse side VSG

Solar glass Cell layer Glass panel/foil composite Air space Inner insulating glass pane

Solar glass Cell layer Glass panel/foil composite Air space Inner insulating glass pane VSG

4.5

50 40 30 20 10 0 1990

1995

2000

Stacked cells (concentrator) Silicon monocrystalline Silicon polycrystalline Silicon micromorph/amorphous

2005

2010

2015

CIS, CIGS CdTe Dye cells Organic cells

Mono and polycrystalline silicon cells

Solar cells based on crystalline silicon (Si) dominate the market with a current share of 90 %. Silicon is a nontoxic material that has been long known and proven in the field 4.6

30

A single crystalline solar cell can now supply about 4 Watts with a typical cell voltage of about 0.5 Volts. To create larger units with conventional voltages as readyto-install building components, many solar cells are combined to form a PV module. In a standard module, sets of 54, 60 or 72 cells connected in a series combine to form a single or occasionally double string (Figure 4.5). A typical crystalline standard module has a power output of between 150 and 300 Watts corresponding to a surface area of 1.2 – 2 square metres – with approximate dimensions of 1.6 metres ≈ 1 metre. At 15 – 25 kg mass it can be managed by a single person. Geometrically, thesolar cells in a single module are arrayed in 4 – 6 rows, sandwiched between a glass pane in front and a composite plastic film on the back. During the manufacturing process the solar cells are embedded bilaterally into a transparent synthetic medium called ethylene vinyl acetate (EVA). This ensures that the cells are protected from weather, mechanical stresses and moisture. The facing glass is a special hardened solar glass with a low iron oxide content, and is therefore especially transparent. Most modules are equipped with an aluminium frame that protects the vulnerable glass edges and is used for mounting (Figure 4.4). The use of frameless modules is also unproblematic, provided that special care along with the appropriate mounting clamps are used in the installation process. The electrical contacts are made through sockets fixed to the rear of the modules. These are equipped with the standard connection cables and with polarised and touch-safe plug contacts. Materials other than EVA that can be used to encapsulate solar cells in a standard module include polyvinyl butyral (PVB), Teflon and cast resin. These alternatives are employed, for example, when glass is used as backing instead of foil. With the appropriate permits, such double glazed modules can serve as overhead glazing or as a component of the facade (Figure 4.12, page 33). Solar modules come in standard and special varieties. In contrast to the custom-made special modules, standard modules are produced inexpensively in bulk and are used in photovoltaic installations that place no unusual demands on the modules. They are installed with standard mounting systems on the roof or on open surfaces. There are many materials and concepts for solar cells (Figure 4.8) that differ from one another in form and colour as well as properties and performance characteristics (Figure 4.15, page 34). The following sections will present a few important types of solar cell.

Solar cells and photovoltaic modules

3.5 Wp

100– 250 Wp 1 kWp –10 MWp

60 –100 cm 15.6 cm

100–200 cm 1 kWp – 500 kWp Cell string

Cell

Module

String

Generator 4.7

of electronics, and is readily available in the Earth's crust. Since it does not occur in its pure form, however, it must be extracted at high temperatures from molten quartz sand. By chemical processes the raw silicon is then purified until it is nearly 100 % pure. The resulting silicon is subjected to various processes in blast furnaces to yield monocrystalline or polycrystalline silicon. In the manufacture of cells, crystalline silicon blocks, or ingots, are cut into thin wafers. These are then furnished with an additional phosphorus-doped cell layer, as well as an antireflective coating and contact points, to create the finished solar cells. • Monocrystalline silicon cells are mostly square with rounded corners (semisquare). The side length of the square cells is 12.5 or 15 centimetres. Since the cell material consists of only a single crystal, the cell surface is homogeneously dark blue to black. The electrical quality of monocrystalline solar cells is very high, reaching efficiencies of between 15 and 19 % (Figure 4.6). • Polycrystalline cells can be identified by the shimmering shades of blue in their crystal structure. They are square with a side length of 10, 12.5, 15 or 15.6 centimetres. Their efficiencies typically lie in the 14 to 17 % range. Polycrystalline silicon is easier and cheaper to produce than the monocrystalline variety, which is why Crystalline silicon solar cells

Monocrystalline

Polycrystalline

polycrystalline PV modules dominate the world market with a 50 % market share. High performance cells Manufacturers and research institutes are continually working to improve solar cells. High performance cells stand out in that their efficiencies are markedly higher than those of most solar cells. They are based on the use of very pure silicon as well as on an improved cell structure coupled with innovative contacts, for example contacts on the rear face. This raises the cell efficiencies to more than 22 %. Other manufacturers combine different technologies, such as applying an additional amorphous silicon layer to monocrystalline wafers to raise efficiencies to more than 21 %. One possibility for producing high performance cells inexpensively is the so-called PERC concept, in which polycrystalline cells are processed further by automated standard means. PERC stands for “Passivated Emitter Rear Cell”; meaning the

4.4 Cross section of a framed standard solar module 4.5 Typical layering (from outside in) of photovoltaic modules for building integration 4.6 Efficiency curves: verified records of laboratory-made miniature solar cells 4.7 Modular construction of a solar generator 4.8 Typology and characteristics of the three solar cell generations Organic solar cells

Thin film solar cells

On glass pane

Foil and strip-shaped solar cells

Special types • High-efficiency cells • Hybrid cells

• Amorphous silicon • Micromorph silicon

• Wafer technology: round to square individual slices • Slice thickness 0.2 mm, edge length 10.0 –15.6 cm • Approx. 85 % market share, mature technology • 14 – 20 % • 13 – 17 % Cell efficiency Cell efficiency

• Vacuum technology, galvanic: normally full-surface substrate layering • Layer thickness 0.5 – 5.0 μm, cell width 0.5 – 17.0 mm or strip width 1 – 36 cm • Approx. 15% market share and rising • 6 –10 % • 8 –14 % Module efficiency Module efficiency

• CdTe • CIS, CIGS

• Amorphous silicon • CIGS

Foil /glass substrate • Dye solar cells • Polymer solar cells • Oligomer solar cells

• Printing process or similar • Nanostructure • Pilot stage • 2 – 3 % efficiency

4.8

31

Technology and systems – photovoltaics

emitter and the rear face of the cell are designed with a protective layer, which reflects the light striking it back to the wafer. This allows additional energy to be utilised, making efficiencies of about 19 per cent possible. Thin film solar cells

4.9

4.10

4.9 The thin film modules form a homogeneous surface. University of Erfurt (D) 2011, AIG Gotha 4.10 Coloured solar cells are used as a stylistic element. Office building in Bordeaux (F) 2013, BDM Architectes 4.11 The flexible foil modules are fully integrated into the air-filled ETFE foil cushions. They lie flat on the mechanically pre-stressed middle layer of three layers of foil. The modules are grouped together inside the cushions by cables, which exit these through the underside. Carport, Waste Management Department, München (D) 2011, Ackermann Architekten 4.12 Laminated safety glass with polycrystalline PV cells; Research Centre AGC Glass Europe in Gosselies (B) 2013, Assar Architects

32

The substantial material and energy requirements for the manufacture of crystalline silicon cells have been reflected in high production costs. In the 2000s, the growing cost pressure led to increases in the development and production of thin film cells, for which the material and energy needs were smaller. Although it was assumed early on that the market share of thin film technologies would continue to rise, the cost savings achieved in the interim in the crystalline sector, coupled with its higher efficiencies, made a technological transition unlikely in the medium term. The thin film market share in 2015 stood at 10 %. Thin film technology is interesting from a technological and usage standpoint because of a number of characteristics. Among these are reduced sensitivity to temperature and shading, flexibility, better utilisation of the spectral bandwidth of sunlight, geometrical freedom, possible transparency levels of the material, a homogeneous appearance, integration advantages, and a tunability to to desired light spectra. These advantages, however, must be weighed against a reduction in efficiency compared to crystalline modules, as well as a more rapid degradation in efficiency over the modules’ lifetimes. The optical qualities of the thin film modules are especially noticeable. Their individual cells are narrow strips, which, in contrast to the typical grid pattern of crystalline modules, look homogeneous from afar (Figure 4.9). Because of this, thin film modules on roofs are often less conspicuous and easier to integrate into the architecture of the building. Nowadays however, crystalline modules with dark frames and foil backing, and a similar visual appearance, are also available on the market. Amorphous silicon (a-Si) and micromorph (μ-Si) silicon cells Amorphous silicon is the star of thin film technology. Small amorphous modules are incorporated in their millions into calculators, watches, torches, etc. A disadvantage of amorphous cells is their low efficiency of about 6 %. The development of stacked cells has led to a higher efficiency of up to 7 %, and in the case of micromorph cells up to 12 %. In stacked cells, cell layers (two in tandem cells, three in triple cells) with differing spectral sensitivity are stacked to increase efficiency. Amorphous silicon cells have good temperature behaviour in that their efficiency drops only slightly when they are hot. Modules with this type of cell are therefore especially suited for integration into buildings where there is limited rear ventilation. The very thin cell material facilitates the production of flexible modules (Figure 4.11). In such cases, the facing glass is left off, and instead the cell material, suspended in a fluoropolymer and EVA bond, is deposited onto a flexible metal foil. In the past this type of module was attached directly to roof

Solar cells and photovoltaic modules

membranes, for example, making it usable even on roofs that were structurally unsuited to standard modules, such as lightweight flat roofs. Micromorph solar cells are a combination of microcrystalline and amorphous silicon in a tandem configuration. Compared to amorphous cells, micromorph cells achieve a markedly higher efficiency. The efficiency decline that occurs in many thin film modules within the first 1000 hours of operation, known as the initial degradation, is much smaller in micromorph cells. Visually, the two technologies are barely distinguishable. Many manufacturers have made attempts to gain entry to this technology field. However, since the expected efficiency increases and production cost decreases in comparison to the rival crystalline technology have so far failed to materialise, many companies have been forced to curtail their production. Copper indium diselenide cells (CIS) Among the thin film technologies, CIS technology currently achieves the highest efficiencies at 14 %. The manufacturing process, however, is complex, and indium in particular is an expensive material. Their dark grey to black colour makes the cells optically appealing. CIS modules have a lower temperature dependence than crystalline, and lose about a quarter less efficiency (about 0.1 % per °C) when heated. In well-ventilated installations this corresponds to annual energy losses of about 0.6 %, and in less favourable applications (facades or roof integrations without rear ventilation, for instance), of 1.5 %, compared to the standard test conditions (see electrical characteristics of PV modules, page 35). The higher energy yield for red light means that more energy is produced during sunrise and sunset, which represents a slight advantage in east or west-facing installations. To improve conductivity, in some cases some of the indium is replaced with gallium (CIGS cells). Cadmium Telluride Cells (CdTe) The 13 % efficiency of the glossy dark green to black cadmium telluride (CdTe) solar cells also exceeds that of the amorphous cells. Of all the thin film technologies, the manufacture of CdTe modules once yielded the greatest cost savings. Like CIS modules, CdTe modules have a smaller dependence on temperature so that, compared to crystalline modules, they lose about a third less efficiency when heated. Since they yield more energy in the blue range of the spectrum, CdTe cells are especially useful for energy production when the sky is overcast. For more red-shifted light as at sunrise and sunset, on the other hand, the cell yields are relatively suppressed. The use of the heavy metal cadmium is somewhat controversial. Since cadmium is a waste product generated in the extraction of zinc, its further processing into the nontoxic compound CdTe can be viewed as ecologically unobjectionable. But in the case of fire, it is possible for toxic cadmium to be released into the smoke due to the high temperatures. Studies done by the Bayerisches Landesamt für Umwelt (Bavarian Department of the

Environment) found, however, that at a distance of about 100 metres from a fire the threshold value for posing a health hazard is not reached. At the end of their operational life, CdTe modules must be treated as hazardous waste and, like the products of other module technologies, should be recycled. Organic solar cells

A novel, organic type of solar cell, developed in 1991 in large part by Swiss chemist Michael Grätzel, could become the least expensive alternative to silicon-based technology in the future. While the energy conversion in solar cells to date depends on the semi-conducting p-n junction of silicon, thereby making a cell behave like an illuminated diode, an organic solar cell absorbs light via an organic dye and extracts energy from sunlight using photosynthesis, as a plant does with chlorophyll. In 2013, a maximum efficiency of 12 % was achieved with a very small 1.1 square-centimetre plastic solar cell. These organic tandem solar cells are manufactured at low temperatures of approximately 120 °C by vacuum thermal evaporation of carbon molecules, and deposited in a roll-to-roll process onto a transparent 30 centimetre-wide polymer foil substrate. The main advantage is the light weight of the plastic modules. Modules with an efficiency of 7 % are currently being introduced to the market. The main problem with organic solar cells has thus far been their long-term stability: in practical experiments their

4.11

4.12

33

Technology and systems – photovoltaics

Aluminium frame Glass cover Photovoltaic cell Absorber (metal sheet) Collector tube Rear insulation

Electricity Heat

4.13

Hybrid modules, or combined systems for PV and solar thermal energy

Power [W/m2]

In hybrid modules, solar thermal collectors are combined with PV modules (Figure 4.13). Structurally, the solar cells are located on the surface of a liquid or air-cooled absorber, with which they are thermally coupled. Since conventional PV modules convert about 16% of solar radiation into electrical energy while much of the remainder is converted to heat, hybrid collectors can certainly prove practical. The thermal part of the collector acts largely like a normal flat plate collector without selective layering. The behaviour of the PV part, on the other hand, depends strongly on the application. If hybrid collectors are operated at a uniform low flow temperature, as for example in swimming pools or heat pumps, this can result in cooling of the PV part and consequently to increases in electrical yield. Conversely, using them for

service water heating without a heat pump can have the opposite effect: the cells would be subjected to further heating and their electrical yield could drop significantly. In most cases it is advisable to separate the solar thermal and photovoltaic energy conversion processes whenever there is enough space to do so. So-called combined systems with standard dimensions are often based on proven framing systems for roof windows. As a consequence, window manufacturers offer roof windows, PV modules and thermal collectors all based on the same grid dimensions and the same window frames (Figure 4.14). In addition, for new buildings or complete roof renovations, combination systems often come factory-integrated into the prefabricated roofs. Electrical properties of PV modules

The efficiency of solar modules plays an essential role in energy efficiency. It determines the maximum electrical power that a given cell or module surface can generate from sunlight. Since the solar radiation intensity fluctuates with the weather, an irradiance of 1000 W/m2 is defined as the reference value for the determination of the efficiency.

100

50 %

180

45 % 43%

160

✺ 155 36% ✺ 134

140 ✺ 125

120

30 %

100

25 % ✺ 84

22%

80

40

35 %

✺ 105 20%

60 ✺ 40

40 %

Transparency

efficiency dropped significantly after just a few years. It remains to be seen whether the advertised lifetime of 20 years will truly be achieved, making organic solar cells suited for use in permanent building applications. According to the manufacturers’ claims, the modules have passed relevant long-term simulation tests.

4.14

15 %

15% 13%

10 %

✺ 35

10 %

20 %

20

5%

0

0 a-Si thin film

Polycrystalline

Monocrystalline Highly efficient

10 % Transparency

5 mm Spacing

3 mm Spacing

a-Si thin film 20% Transparency

Monocrystalline Semitransparent

Monocrystalline Highly efficient

Polycrystalline

5 mm Spacing

25 mm Spacing

50 mm Spacing 4.15

34

Module current and voltage Radiation intensity directly affects the current in the module. If the light intensity is halved, the current delivered by the module is also halved. The module voltage is mostly influenced by the module temperature. It increases with low temperatures and can therefore exceed its nominal value by up to 20 % in winter. Conversely, the voltage drops as the temperature rises, and the power generated by the module drops as a consequence. The behaviour of the electrical parameters is specified for specific temperatures. In crystalline modules the decline in the nominal power amounts to 0.45 % per degree of temperature elevation. On a sunny summer day the operating temperature of roof modules can easily exceed 50 °C. Nevertheless, because of the longer exposure and higher solar irradiance values, the yield of solar modules is almost 80 % higher in summer than in winter. Good rear ventilation of the solar generator supplies cooling and ensures good electrical production.

E = 1000 W/m2

4

E = 800 W/m2

3.5 3

E = 600 W/m2

2.5 E = 400 W/m2

2 1.5

E = 200 W/m2

1 0.5 0 0

5

10

15

20

25

30

35

40

45

50

VMPP range Module voltage V [V]

a

Module current  [A]

Solar panel characteristic curve The characteristic curve (also known as the current-voltage or I-V curve) of a solar module illustrates the interaction of the parameters (Figure 4.17), and shows all the operating points that can occur under standard test conditions under given loads. The MPP, or Maximum Power Point, which corresponds to the point on the curve for which the product of current and voltage is maximised, can be readily identified. This maximum power (PMPP) and its associated voltage VMPP and current IMPP are stated on the rating label of a module, in addition to two additional characteristic values: the short circuit current IS and the open circuit voltage VO. Unlike other technical devices, PV arrays only rarely operate in their nominal ranges, since standard test conditions are rarely obtained in reality. Current, voltage and power change continually throughout the day, depending on temperature and irradiance.

5 4.5

6 5 4

ϑ = 75°C ϑ = 50°C

3

ϑ = 25°C ϑ = 0°C

2

ϑ = –25°C

1 0

0

10

20

30

40

50

60

VMPP range Module voltage V [V] 4.16

b

Module current  [A]

Power In addition to radiation intensity, the solar spectrum and the cell temperature are both critical factors influencing the output power of a cell (Figure 4.16). The Standard Test Conditions (STC) used in determining the electrical performance values in photovoltaics therefore also include a reference cell/module temperature of 25 °C and a solar spectrum defined for a solar elevation of 41.8° and AM 1.5. The efficiency of a module is always a little smaller than that of the cells, since the facing glass does not transmit all the sunlight and the cell coverage of the module area is not 100 %. The efficiency of PV modules is given by the ratio of the PV output power to the solar power delivered to the module surface. Since the combined surface area of all the cells in a module is smaller than that of the module itself, the module efficiency is smaller than the cell efficiency. And since the corners of monocrystalline cells are usually rounded, modules with polycrystalline cells often have module efficiencies on par with those of monocrystalline modules.

Module current  [A]

Solar cells and photovoltaic modules

8 7 6 5 4 3 2 1 0 0

30

Monocrystalline Si Polycrystalline Si

60 CIS

90 CdTe

120 a-Si

140

160

μ-Si Module voltage V [V] 4.17

4.13 Cross section of a hybrid module 4.14 Combined system with PV modules, solar thermal collectors and roof windows; Tract house in Leverkusen (D) 2013, Caroline Wachsmann 4.15 Relationship between transparency and efficiency for various typical cell types 4.16 Irradiation and temperature dependence of PV modules a) Module current as a function of voltage and irradiance b) Module current as a function of voltage and module temperature 4.17 Comparison of characteristic curves for different module types

35

Technology and systems – photovoltaics

Thin film modules, particularly amorphous modules, have low efficiencies and a flat current-voltage curve. They are characterised by higher voltages and lower currents than crystalline modules. Connecting just a few modules in series rapidly results in high voltages, which must be taken into consideration in the layout. Compared to crystalline modules, thin film modules have a higher shading tolerance (Figure 4.18). In standard crystalline modules with four cell rows, the shading of a single cell means that only the unaffected half of the module can continue to provide energy. In the larger modules with six cell rows that are in common use now, two thirds of the module remain active under similar conditions. In contrast, because of the strip-like shape of the cells in thin film modules, the complete shading of a cell is more unlikely. The power output therefore usually drops only by an amount proportional to the shaded area. The shading of building surfaces must be taken into consideration in the design of PV installations. If a shadow is cast over a large area over an extended time interval, the location is unsuited to the installation of a solar panel, since the energy yield would be too low. The energy losses due to smaller shadows from a chimney or a lightning rod, for instance, can be minimised with simple measures. The wiring of the modules can be adapted to the shading situation, modules with bypass diodes can reduce losses, and in some cases dummy modules can be employed in order to prevent a flat installation from being visually impacted by missing sections. Simulation software makes it possible to obtain an exact visualisation of the sun’s path, enabling the documentation and careful consideration of any shadows that may impact solar installations.

Inverters as system headquarters The inverter provides the connection between the solar generator and the alternating current grid or the alternating current consumer. It converts the direct current (DC) produced by the solar generator into alternating current (AC), and adjusts it so that its frequency and voltage match that of the grid. Thanks to modern power electronics the conversion into alternating current occurs with minimal losses (about 2 – 4 %). Apart from this AC conversion, solar inverters also fulfil the following functions: • matching the operation point of the inverter to that of the PV generator (MPP tracking) • operational data acquisition and signalling • protection (overload, overvoltage, polarity reversal, insulation monitoring, etc.) • network protection and network management In grid-connected photovoltaic installations, the inverter is connected to the municipal electrical network and the electricity fed into the grid must comply with the network’s qualitative specifications. Small PV installations of up to about 40 square metres (that is, with a peak power rating of about 5 kilowatts peak) usually undergo a single-phase connection to the low-voltage (230 V) grid. Larger facilities generally feed as uniformly as possible into all three phases of the electricity grid, in most cases via central three-phase inverters. In order to supply the network with the maximum power, the inverter must operate at the maximum power point (MPP) of the solar generator. Because of the fluctuations in irradiance and temperature, the power output of the solar generator varies continually. An MPP tracker in the inverter uses voltage adjustments to match its operating point to the MPP of the solar generator. Modern inverters also allow for the monitoring of the installation through operational data acquisition and have display and communications interfaces with computers, the internet, wifi, etc. Most inverters have built-in DC and AC protective measures to prevent damage from polarity reversals, overvoltages and overload, and they also provide insulation as well as network protection features. Because of their high efficiencies of 98 %, transformerless inverters dominate the market.

Battery storage systems

4.18 Differences in efficiency response to shading between thin film and crystalline modules. Thin film modules have comparatively small efficiency losses in cases of partial shading 4.19 Self-consumption of PV electricity with a battery system 4.20 AC- and DC-coupled battery systems

36

Storage systems (Figures 4.19 and 4.20) can be classified into two types: ones in which batteries are coupled to the DC system via a direct current transformer, and ones where an additional converter connects the battery to the AC system. In DC-coupled systems a separate direct current transformer takes over the MPP tracking. In addition, the systems are equipped with a network inverter and a smart charge controller. Based on solar electricity supply and charge status, the latter determines whether the electricity from the PV installation flows to the battery or is fed

Battery storage systems

through the network inverter into the municipal grid. In a back-up system the charge controller also shuts off loads as needed. In AC-coupled storage systems the PV installation is set up like a grid-connected PV installation without a battery. The only difference is that an additional load, the ACcoupled storage system, is connected to the user circuit. An existing grid-connected installation can therefore be relatively easily retrofitted with an AC-coupled storage system. DC-coupled systems are now also being offered on a post hoc basis. The AC storage system consists of a converter with charge controller functionality and the battery bank. In the AC case, therefore, both an inverter for the PV installation and a converter for the battery system are employed.

100 % 90 % 80 % 70 % 60 % 50 % 40 % 30 % 20 % 10 % 0%

100 % 90 % 80 % 70 % 60 % 50 % 40 % 30 % 20 % 10 % 0%

4.18

Which of the two types of system is technically more advantageous is still up for debate. In principle, DCcoupled systems can achieve higher efficiencies and save manufacturing costs, since they do not require the converter. However, if high-efficiency converters are used in the AC-coupled systems, the difference in overall efficiency between AC and DC systems is small.

Day

Night

Lead-acid battery storage system

The most common and least expensive battery type to date is the simple lead-acid battery with grid plates and liquid electrolyte. Because it is used as a starter battery in cars, it is produced in bulk at low cost. A further application for which it is well-suited is as the classic solar battery. Lead-acid batteries normally have a lifetime of under 2,000 cycles and have to be maintained about every six months. The maintenance process includes checking the electrolyte level and topping it up with distilled water if necessary. Voltage and acid concentration are measured and the battery is fully charged. An advancement in the classic lead-acid battery with grid plates is the more maintenance free lead-acid gel battery. In this variation, additives thicken the acid to a gel, which is why the lead-acid gel battery has a higher discharge capacity (up to 80 %) and a higher cycle life (up to 3,000 cycles). With a 20-year operational lifetime for a storage system, the batteries have to be replaced two to three times, a fact that must be taken into account in determining its cost-effectiveness. Lead storage systems are often set up in a ventilated electrical equipment room. Operation and maintenance are relatively costly and require professional guidance.

Energy manager

Energy manager

4.19

PV generator = ~ Low voltage network 230 V, AC 50 Hz

PV inverter Battery = ~ Battery converter

Household

PV generator = = PV-DC/DC transformer

Lithium-ion battery storage system

The lithium-ion battery has some advantages over the lead-acid battery: Specifically, its markedly higher number of charging cycles, as well as a greater energy density coupled with a greater depth of discharge, make it an attractive storage option for PV installations. Lithiumion batteries tolerate more than 10,000 charging cycles, provided they are not discharged by more than half their capacity. For these batteries, it is better if they are never

DC

Low voltage network 230 V, 50 Hz

= ~

Battery = = Battery-DC/DC transformer

Network inverter Household 4.20

37

Technology and systems – photovoltaics

Solar cell material

Module efficiency

Required area for 1 kilowatt peak

Silicon high-efficiency cells Rear side contact, HIT

17 – 20 %

5 – 6 m2

Monocrystalline silicon

11 – 17 %

6 – 9 m2

Polycrystalline silicon

10 – 16 %

6 – 10 m2

Thin film Copper indium diselenide (CIS)

7 – 14 %

7 – 12,5 m2

Cadmium telluride (CdTe)

7 – 13 %

9 – 17 m2

Micromorph silicon

7 – 12 %

8,5 – 15 m2

Amorphous silicon

4–7%

15 – 26 m2 4.21

On the roof Large spacing (> 10 cm) On/in the roof Good rear ventilation On/in the roof Poor rear ventilation On/in the facade good rear ventilation On/in the facade with limited rear ventilation Facade/roof integration, no rear ventilation 0

1

2

3 4 5 6 7 8 9 10 Decrease in energy yield [%]

fully charged and discharged (full charge cycles). For use in a grid-connected PV installation, most manufacturers of storage systems quote values between 5,000 and 10,000 cycles. In solar systems, a full charge depends on the weather. While lead-acid batteries should be fully cycled as often as possible to ensure a long lifetime, the lifetime of lithium-ion batteries is prolonged by the use of partial charging cycles. This makes them better adapted to the varying energy supply of PV installations. In addition, their self discharge is 50 – 80 % lower than that of lead-acid batteries. Excessive discharges or charges exceeding the end-of-charge voltage must be avoided at all costs, since the battery can be irreversibly destroyed in these cases. For this reason, battery management systems monitor the potential difference across each individual cell. Since the operational and storage temperatures of the batteries have an effect on longevity, temperature monitoring systems are also frequently used. Smart charging management and operation at uniform temperature can prolong battery life; and some low-maintenance systems advertising a 25-year lifetime are available. The manufacturers’ claims of lifespan and cycle stability, however, are usually based on accelerated aging tests performed in the laboratory. If no guarantees are offered, such claims should therefore be taken with a grain of salt. Because of their many advantages and their decrease in price, the market share of lithium-ion systems used in stationary home battery storage grew to 80 % in 2015.

4.22

Planning and design Today’s EEG feed-in compensation is less than the price for electricity that the customer must pay. Therefore it makes sense for people who generate solar power to use as much of it themselves as they can (i.e. to maximise self-consumption). The power output of the installation should thus cover the electrical power requirements of the building, especially during sunny periods. If storage is used, the installation can be made larger. A practical installation size depends on many parameters; in addition to the projected annual yield of the installation and its seasonal and daily fluctuations, consumption patterns must also be factored in. Technical systems such as load management and storage must be considered as well. Location, integration, roof configuration, area requirements

4.21 Efficiency and area requirements of PV modules with different cell technologies. The area requirements of PV installations depend on the efficiency of the solar modules. 4.22 Losses in energy yield due to temperature, as compared to the yield of a free-standing PV array (reference values for Germany) 4.23 Installation concepts with a central inverter, string inverters, module inverters and efficiency optimisers.

38

The first step is to identify suitable surfaces on the building. Good candidates are any surfaces that are fairly contiguous and only slightly shaded, and those that do not face north. Contrary to earlier assumptions (made in the days of high feed-in compensations), east- and westfacing surfaces are also economically feasible, as these receive good irradiation in the mornings and evenings and can increase self-consumption. Though roof surfaces are naturally the first choice, unshaded facade surfaces are also possibilities.

Planning and design

A rule of thumb for crystalline modules is that 8 square metres of area correspond to a kilowatt of power. Most of the time, of course, the entire area cannot be used because roof edges, roof structures, roof windows and lightning rods, etc., require clearances. The area needed for semi-transparent modules increases in inverse proportion to the percentage of light transparency (Figure 4.21). The supporting structure must be capable of withstanding the wind and snow loads on the generator as well as its own weight, and of transferring these loads to the roof structure. In the specific roof design, the following points must be considered: • The dimensions of the modules (height, width) as well as the orientation of the mounted system (horizontal, vertical) • Clearances from the roof edges, insofar as these are required to reduce wind loads • Any expansion joints between modules • The unimpeded functionality of the roof and its structures (special attention must be paid to chimneys, roof ventilators, smoke and heat exhaust systems, fall protection anchor points, lightning rods, etc.) • The physical separation of any exhaust vents from the modules (for fire safety reasons the vents must project at least one metre above the modules if they lie within 1.5 metres of them) • A sufficient distance between the modules and any shadow-casting roof structures • The shading impact of the building surroundings • The fire-safe installation (Figure 4.38, page 51). The module surfaces present the wind with a large planar target – especially on high buildings, on which considerable wind forces come into play. The choice of mount depends on the statics of the roof. These determine whether the installation can be set up freely or must be firmly attached to the roof. In the commercial sector the statics of new flat roofs are often already “maxed out”, so that any additional loads must be distributed to the loadbearing building walls.

Roof mounting/elevated installations Free-standing installations are the most common type on flat roofs. In these, the mounting system is secured by ballast, and a penetration of the roof is not required. The ballast, consisting, for example, of a concrete base, paving slabs or the roofing substrate of green roofs, is so heavy that even for the maximum expected wind loads the installation remains firmly in place. The required weight depends on the height of the building, its location and the composition of the roofing. Increasingly, so-called aerodynamic elevation systems are being employed on roofs with limited permissible loads. These are often full-surface support systems of sheet metal or synthetic materials with back panels. The shape and mounting of these systems is such that wind forces are minimised, requiring less ballast. In addition, the modules are usually mounted at an inclination angle of less than 20°, and are outfitted with a slanted back panel and sometimes with side panels. The individual rows are often connected to one another with mounting profiles. The inclination angles of the modules and the back panels and the spacing of the module rows are all optimised by the manufacturers in wind tunnel tests and airflow simulations. These measures can reduce the ballast weight by up to 85 %. The systems must be certified to meet wind load requirements. Mounting these types of systems with an east-west orientation has some advantages. The back panel is not needed; also, more modules can be set up on a given surface area because the rows do not shade one another. Thanks to these advantages, the east-west installation counters the higher specific yield of a south-facing array with a higher absolute yield, as well as more favourable conditions for self-consumption. The most common mounting on pitched roofs is parallel to and just above the existing roof covering. For the usual roof materials such as tiles and sheet metal there are suitable mounting solutions. If the simple solutions are visually unsatisfactory, other systems are available that can be structurally and, thanks to the possibility of different colourations, stylistically well incorporated into any

PV modules with integrated inverters

PV generator

=

~

=

~

PV modules with integrated power optimisers

=

~

Generator combiner box Inverter

Municipal grid

=

=

~

~

=

=

~

~

=

~

Municipal grid/distribution to buildings 4.23

39

2.0

Usable battery capacity/annual electricity consumption [Wh/kWh]

Usable battery capacity/annual electricity consumption [Wh/kWh]

Technology and systems – photovoltaics

1.8 70%

1.6 1.4 1.2

60%

1.0 50%

0.8 0.6

40%

0.4 0.2

30% 20 %

0.0

2.0 1.8 1.6 1.4 1.2 1.0 0.8 0.6

90% 80% 70% 60% 50% 40% 30%

0.4 0.2

20 %

0.0 0.6 0.2 0.4 0.8 1.0 1.2 1.4 1.6 1.8 2.0 PV installation size/annual electricity consumption [Wp/kWh]

0.8 1.2 1.4 1.6 0.2 0.4 0.6 1.0 1.8 2.0 PV installation size/annual electricity consumption [Wp/kWh]

a

b

design. Dark anodised mounting systems with completely black modules can be combined to form very homogeneous installations that adapt seamlessly to any building.

partition the generator into sections with different numbers of modules per string, or with variations in orientation or exposure (such as shading), without incurring additional losses. In particularly small arrays or in situations in which it makes sense to equip each module with its own MPP tracker (for example, if there is significant shading, if the modules are different or if their irradiation levels vary), single-module inverters (microinverters) may be used. Since in this case every module has its own inverter, the inverter cost rises, a fact that is somewhat mitigated by the more convenient electrical wiring. However, the array is much more shade-tolerant as a consequence, and it can be easily expanded. Some firms offer separate module-level DC transformers with MPP trackers (called power optimisers) as an inexpensive alternative to module inverters. The output of these power optimisers feeds into a central inverter with no MPP tracking functionality.

Roof-integrated installations In a roof-integrated installation the modules lie in the plane of (and partly in place of) the conventional roof covering. While the cost of installing these systems is higher in the case of refurbishment projects, in new buildings the cost can actually be lower since traditional roof materials are not needed. Rain protection of roofintegrated installations is achieved either by a waterbearing layer underneath the modules, or by layering the modules like shingles. Good rear ventilation must be provided to prevent water damage to the roof through the formation of water condensate on the back side of the modules, and to reduce temperature losses. The power output of the modules also benefits from rear ventilation. On a sunny day with an ambient temperature of 20 °C, a free-standing module operates at about 42 °C. This operating temperature is significantly influenced by the thermal conditions of the surroundings, which vary according to how the PV generator is set up. In roofintegrated modules without rear ventilation, temperatures can soar to 90 °C. Since the power output is temperaturedependent, this impacts the energy yield (Figure 4.22, page 38). In the design, the planning expert must pay special attention to the cabling access through the roof and to the attachments for the mounting of the modules. PV installation concepts

The electrical component (Figure 4.23, page 39) of the PV generator is determined by the inverter. In smaller installations, all the modules (usually between ten and twenty) are wired together in a “string” and are connected in series to a string inverter. In larger installations, several module strings are connected to an inverter. These “central inverters” are available for powers ranging from a few kilowatts to more than a megawatt. The design of the array should ensure that each string has the same number of modules and the same general orientation. If this is not possible, inverters with multiple MPP trackers are available; these make it possible to 40

4.24

Solar electricity self-consumption as design foundation

Because of the current low EEG feed-in rates, consuming generated solar electricity directly is economically preferable to feeding it into the grid. It is therefore very important that measures that increase the self-consumption rates be incorporated into the design of solar installations. The more solar electricity generation coincides with the immediate demand, the greater the self-consumption, and thus the more economical the system. Only the excess electricity is then fed into the municipal network for EEG compensation. Since electricity demand does not always occur at the same times as solar electricity generation, the power of the PV installation should be adjusted to the expected daily load. In considering the energies generated by the solar array, bought from the grid and consumed in the house, one must differentiate between the self-consumption percentage and the solar coverage. The self-consumption percentage is determined by the ratio of the generated solar energy that is actually concurrently used in the house to the total energy harvested: Solar electricity self-consumption [kWh/yr] Self-consumption = ≈ 100 percentage [%] Total solar electricity [kWh/yr]

Planning and design

Electricity generation Charging of batteries Electricity drawn from battery Electricity drawn from the grid

00:00

06:00

12:00

18:00

00:00 Time 4.25

The solar coverage or degree of self-sufficiency, on the other hand, describes what portion of the total electricity consumed in the house came from the solar installation. Solar coverage [%] =

Solar electricity self-consumption [kWh/yr] Total electricity consumption [kWh/yr]

≈ 100

Since residences usually have low electricity needs during the sunny hours of a work week, only a fraction of the solar electricity is consumed. For PV array sizes typically used for single family houses without electrical water heating (4 – 7 kilowatts peak), this fraction is usually less than 30 %. The self-consumption percentage can be raised by about 10 % if load management is employed. A simple load management system works with a load relay controlled by the solar inverter, and automatically connects certain loads (such as dishwashers, washing machines or dryers) whenever enough solar electricity is available. If a typical four-person household uses electrical water heating with sufficiently large hot water storage, solar coverage can be raised another 20 %. Using PV generators to supply instantaneous electric water heaters, on the other hand, is not very effective, because of the high power requirements and the absence of a thermal reservoir. Increasingly, load management is being augmented by programmable energy management systems. Coupled with Smart Meters and interfaces for the control of energy supply technology (possibly including room and hot water heating), these can variably and precisely optimise energy consumption and energy demand streams. They also facilitate an improved integration of storage systems. Energy management systems are often incorporated into Smart Home or Smart Building Systems, which also control and monitor other building services (sun protection, lighting, electronic devices, etc.). Experiences in the use of Smart Meters, energy management systems and timeof-use rates in model projects show, however, that both the energy savings and the time shift potential are relatively limited. In multi-family residences the available roof area per resident is smaller, resulting in less specific solar power per capita. At the same time, these residential buildings often use electricity continuously throughout the day because

of building services such as pumps, ventilators, etc., so that the self-consumption percentage increases markedly. In addition, the electrical consumption in multi-family homes is spread out more uniformly, since each household uses electricity at slightly different times. One can therefore expect a considerably higher self-consumption percentage of the generated solar energy – about 60 %. The self-consumption rate in commercial buildings is always higher, and for a seven-day-a-week operation it can reach 100 %. The solar coverage, on the other hand, is often in the range of 10 – 30 %. For accurate planning, load profiles of energy usage should be used. In the commercial sector, users with an electricity consumption of over 100 MWh or a connected load above 50 kW undergo a fifteen-minute load measurement. If the building owner or the network operators have access to these values, the load profiles can be used in the design of the facility. If the values are not available, standard load profiles can be obtained from the energy supplier. These are determined for different types of businesses and take deviations due to weekend operations into account. It is important to remember that the price of electricity for commercial use, especially for bulk consumers, is considerably less than that for household consumption. Even so, at solar electricity generation costs of about 10 cents/kilowatt-hour there is often still enough of a difference for many commercial projects to achieve costeffectiveness. Raising self-consumption with battery storage

Both the self-consumption and the coverage of solar energy can be decisively increased through the use of batteries – in single-family houses, usually by 30 – 60% (Figure 4.24). The most common battery type used for this purpose is the lithium ion battery, which stores excess solar energy and makes it available to consumers in the house when and as needed. A storage system shifts the availability of usable solar energy from the daytime into the evening or night hours (Figure 4.25). Many system vendors or specialised dealers offer standard systems with storage that are optimised for the selfconsumption of PV-generated electricity.

4.24 Estimate of household solar coverage (a) and self-consumption percentage (b) as a function of installation and battery size. The estimates are based on weather data for Kassel. A 5 kW battery inverter is assumed. The diagram can be used to estimate the self-consumption percentage of households with an annual electricity consumption of between 2,500 and 7,500 kWh. For an average annual consumption of 4,000 kWh, an installation size of about 4 kWp and a usable battery capacity of 2,000 Wh, for example, the estimate yields a solar coverage of about 40 % and a self-consumption of 50 %. 4.25 Increase in self-consumption through intermediate storage. The selfconsumption corresponds to the green and yellow areas.

41

Technology and systems – photovoltaics

The size of the battery is heavily influenced by the economic constraints (investment, price of electricity and feed-in rates) as well as the user profile and the solar coverage. A four-person household equipped with a 5 kWp installation will achieve a solar coverage of close to 60 % with a 5 kWh battery. If the storage capacity is doubled to 10 kWh, the solar coverage increases to 70 %. Even a modest-sized battery can thus double the solar coverage, which normally lies at around 30 % for a system without a battery. Any further gains, however, require a relatively high storage capacity. Under the current conditions, storage systems used in combination with PV installations can already be costeffective. In addition, certain network services can be assumed by the storage units. In this way, decentralised energy service providers manage the battery and make its capacity available to the balancing energy market. The array operator receives an additional compensation in return. Other advantages lie in the growing reliability in supply and increased grid-independence for the user. An appropriately suited storage system can also function as a backup system during power outages. PV installations for water heating and space heating support

Using solar electricity to heat thermal reservoirs used for space heating or potable water storage, or to heat the building mass itself, increases the self-consumption percentage and decreases the need for oil or gas. The effort and investment required to use PV-electricity

Combination heat storage tank

Boiler

Photovoltaic modules

Inverter

= ~

Potable water Controls Heater Heating water Load

888.888 888.888 kWh

immersion heater

kWh

Meter Network

Refrigeration system 4.26

directly in a hot water or heating tank are small. The easiest thermal storage method is represented by a hot water tank with an immersion heater. To ensure that this system draws solar energy only when it is not required elsewhere, a control unit is employed which switches on the immersion heater whenever solar energygeneration exceeds the building demand. For this, the performance characteristics of all other loads and of the solar generator must be measured and compared. The immersion heater should have continuously variable power settings and must be limescaleresistant. The incorporation of an immersion heater in combination or buffer storage tanks is also possible (Figure 4.26).

Ground source heat (collector)

Ground source heat (ground probes)

Heat from ground water

Heat from the air

4.27

42

Planning and design

Old construction (34 installations)

2.6

New construction (18 installations)

Photovoltaic modules

Battery Room temperature Controls

2.9 =

Inverter Old construction (34 installations)

Heater

= ~

~

3.3

New construction (18 installations)

3.9 Heat pump

2.0 2.5 3.0 Median coefficient of performance Outdoor air heat pump Median coefficient of performance Ground source heat pumps

3.5

4.0 4.5 5.0 5.5 Coefficient of performance Performance ranges Outliers 4.28

In considering heating support through PV electricity it is important to note that a solar installation delivers only about 20 % of its energy during heating periods, during which time other electrical loads are drawing energy as well. The use of direct electric heaters such as electric floor mats, infrared space heaters and wall heaters should only be considered in highly insulated low-energy buildings. Using solar electricity to support heating in these cases is possible and quite easy to implement. However, for the above-mentioned reasons and due to the limited storage capacity of the building, the contribution of the PV array to the overall heating needs will be relatively small. PV installations with heat pumps

An effective use of solar electricity in heating support is provided by heat pump systems. These make it possible to generate more heat than direct heaters with a lot less electricity. The following device types are classified according to heat source and heating medium (Figure 4.27): 1. Air-to-air heat pumps draw heat from the ambient air and pass it along to an air heater or air conditioner. The ambient air can be outside air, room air, or exhaust from an industrial process. 2. Air-to-water heat pumps deliver heat harvested from air to a water heating system (such as a radiator or floor heating systems). 3. Geothermal (ground source) water heat pumps draw heat from the Earth via a refrigerant circulating through a ground loop or ground probe, and transfer this heat to a water heating system. 4. Water-to-water heat pumps use ground water as well as waste water, cooling water from industrial processes or surface water (lake, river or sea) as their Type

Operation point

Minimum COP for EHPA seal of approval

Coefficient of performance of available heat pumps

Brine /water

B0 /W 35 11 – 17 %

5 – 6 m2 6 – 9 m2

4,0 … 5,0

Water/ water

W 10 /W 35

6 – 10 m2

5,0 … 6,0 (6,5)

Air/ water

A 2 /W 35

7 – 12,5 m2

3,0 … 4,0 (4,4)

Potable water tank

Load 888.888 kWh

Network

Two-way meter

Outside air or ground 4.29

heat source. The harvested heat is transferred to a water heating system. In the operation of heat pumps a flow temperature of 55 °C (hot water or heater) should not be exceeded. The efficiency of heat pumps is mostly due to the usable temperature difference between them and the heat source. The coefficient of performance (COP) represents the efficiency of the heat pump process under laboratory conditions for specific operating points, and is stated in the data sheet of the device. The coefficient of performance is not a conclusive measure of the energetic quality of the heat pump (Figure 4.30), but provides an estimate of its performance under specific, standard operating conditions. The real energy efficiency is obtained by evaluating the ratio of heat generated to energy consumed over the course of a year. This yields the annual coefficient of performance (Figure 4.28), the definitive measure of the unit’s efficiency and cost-effectiveness. A good annual COP of 4 means that the electricity consumed by the system is exceeded by a factor of four in heat produced. The efficiency of air heat pumps is usually smaller than that of water heat pumps. In addition, in air heat pumps located outside the building, the heat exchangers (evaporators) must be heated so that they do not freeze over at low temperatures. In choosing the installation site of air heat pumps in particular, noise emissions should be taken into account. Heat pumps with water as their medium typically use a hot water storage tank and a buffer or combination tank. In buildings with good insulation and a low-temperature heating system, one heat pump can cover the entire heating demand. This is referred to as monovalent operation. When low outdoor temperatures make it necessary to add an additional heat source to meet demand, the operation is known as bivalent.

4.26 Concept of a PV array used for heating support 4.27 Heat pump types 4.28 Ranges of coefficients of performance of ground-source and air heat pumps measured in a field test in new and old buildings 4.29 Concept with heat pump and battery 4.30 Coefficients of performance of heat pumps at specific standard operating points from DIN EN 14 511

4.30

43

Technology and systems – photovoltaics

Energy-efficient new construction Degree of self-sufficiency

Degree of self-sufficiency

Modernised old construction 90% 80% 70% 60% 50% 40%

90%

Heat pump

80% 70%

Heat pump Nighttime temperature reduction Smart Grid

60%

Heat pump Nighttime temperature reduction Smart Grid Battery

50% 40%

30%

30%

20%

20%

10%

10% 0%

0% 4 kWp

7 kWp

10 kWp

4 kWp

7 kWp

a

b

In a modern, well-insulated, large single-family house, the buffer storage tank is often unnecessary since the building itself provides sufficient heat storage capacity. The hot water tank is primarily operated by the heat pump. The PV array supplies the heat pump with any solar electricity that is not directly consumed, and the heat pump passes this along to the well-insulated hot water tank in the form of heat. The resulting hot water can be used even when solar radiation is no longer available. The typical self-consumption percentage for PV installations run in combination with heat pumps is 35 % for a single-family home. A critical factor in the energy-efficient combination of heat pumps with PV installations is that the heat pump’s power must be continually variable. This power regulation is achieved via the inverter by controlling the compressor speed. If the compressor operation is unregulated (that is, if it is merely switched on and off), its lifetime and the performance of the heat pump decline. In addition, the associated high instantaneous power requirements can often not be met by the solar supply. It should be possible to control a heat pump externally, something that is achieved through a Smart Grid (SG) Ready interface. SG-Ready heat pumps are easy to integrate into a regulatory network with a PV generator and an energy management system, and their use facilitates significant increases in self-consumption and solar coverage. In combination with battery storage, the operation of heat pumps can be further optimised, and the PV selfconsumption can be raised even more. In single-family houses, solar coverage of 60% is possible with this setup (Figure 4.29, page 43).

Installation, commissioning, operation and maintenance

Photovoltaic support of cooling systems

Demands for the cooling of buildings are on the rise. Reasons for this include an increased desire for comfort, and higher summer temperatures in buildings due to climate change. The temporal overlap between strong solar irradiance and the need for cooling provides a good incentive for the use of solar-supported air conditioning systems. These include PV-assisted heat pump systems, but also conventional air conditioning systems supplied with solar electricity. 44

10 kWp 4.31

After the modules are physically mounted, they are connected together in series, using built-in wiring, to form strings. If an installation consists of several strings, the individual module string cables come together in the combiner box, and are there connected to the main direct current line that leads to the inverter. The combiner box is comprised of terminals and surge protection devices, and occasionally specific PV safety devices. It must conform to Protection Class II standards and manifest a clear separation between its negative and positive sides. When mounted outside, it should have an International Protection rating of IP 54 and should be UV-resistant. Larger installations often require several combiner boxes. The electrical wiring connecting the PV modules, the combiner box and the inverter must be properly grounded and short-circuit proof. It is important to lay out the cabling in a way that provides for long-term protection of the wire insulation. Sharp edges, small radii of curvature and other stresses on the cables must be scrupulously avoided. Doubly-insulated, single core cables have proven to be an effective and practical solution; laid out separately as positive and negative lines, they provide a high degree of safety. Single-core solar cables labelled PV1-F are recognised for their UV and weather resistance, and should be used exclusively in outdoor applications. Lightning protection

As a rule, larger photovoltaic installations require lightning and overvoltage protections in compliance with Lightning Protection Class III in VDE 0185-305. If the building already has a lightning protection system, any PV generator installed on the building must be incorporated into this system. In some cases this will necessitate additional lightning rods. If a PV array is mounted on a building where no lightning protection exists, a retroactive installation of a lightning protection system is usually not required. Installation site of the inverter

In choosing the installation location for the inverter, it is critically important to comply with the placement condi-

Installation, commissioning, operation and maintenance

tions specified by the manufacturer, especially those relating to moisture and temperature. The ideal installation site for an inverter is cool, dry and dust-free. Often it is placed either next to or near the meter cabinet. If the environmental conditions allow it, the inverter can be installed near the combiner box. This reduces the length of the direct current main line and cuts installation costs. The ventilation slits and the heat sinks must remain unobstructed in order to ensure optimal cooling. For the same reason, the devices should not be mounted in close proximity to one another. The noise generated by the inverter must be taken into account when choosing its location. The device must be protected from any aggressive steam, water vapour or fine particulate dust. Ammonia vapour could, for example, develop in barns or stables and possibly damage the inverter. Larger central inverters are often placed in a separate inverter cabinet together with protection, metering and switching equipment. Outdoor inverters can be installed on the roof or elsewhere outside the building. These devices have an IP 54 rating and are designed to withstand the ambient weather conditions.

Storage systems

When installing lithium ion battery systems, it is important to comply with standard requirements, safety regulations and network connection criteria; as well as protective measures and technology, transportation and storage safeguards, building requirements and fire protection. For safety reasons the use of lithium ion batteries must involve coordinated battery management, segmentation of the cells and application-specific protective measures. The primary charging system must follow the instructions supplied by the battery manufacturer. According to manufacturer guidelines, only batteries of the same type can be electrically connected. If safety requirements are ignored – if, for example, inappropriate charge controllers are used – lithium ion batteries can overheat and cause fires. Lithium ion storage systems are available in self-contained battery cabinets and place fewer demands on their setup location than lead-acid batteries. They should never be placed in any living area or along evacuation routes, but rather in suitable basements, building services rooms or other secondary spaces. No combustibles, flammable materials, or materials with high fire loads should be stored in their vicinity.

Connection to the grid

A PV installation is usually connected to the grid network via the building’s main service panel. Connection to the grid requires conformation with usage regulation VDE 4105, as well as the stipulations of the EEG and Germany’s Energy Industry Act (EnWG: Energiewirtschaftsgesetz). The network and facility protections mandated by VDE 4105 are integrated into most inverters. The EEG allows installations generating less than 30 kW of power to use a “simplified” feed-in management, which allows a maximum effective power of 70 % of the installation’s nominal power to be fed into the grid via the network connection point. In these cases the appropriate inverter is somewhat smaller. The acceptable alternative to this is a communication device controlled remotely by the network operators that adjusts the feed-in amount, according to demand, to set points of 0, 30, 60 and 100% of the nominal power of the PV generator. These power limits, as well as further network requirements such as the provision of reactive power, are usually managed via the inverter. In larger arrays with more than 30 kW of power, the remote-controlled arrangement for limiting the power fed into the grid is mandatory. Facilities with more than 100 kW must also be equipped with a measuring device to determine, at a minimum, the 15-minute load average. For PV installations with their own electricity supply, a bi-directional meter is installed in the main service panel that records both incoming and outgoing energy amounts. The inverter communicates with this meter, and it receives a signal to limit power only if the unused electricity is being fed into the grid. In arrays with a nominal power of more than 10 kW or an energy yield of more than 10 MWh, an additional energy yield meter is needed to determine the proportional EEG cost allocation.

Acceptance inspection and commissioning

Before the PV installation can begin operations, it must pass an acceptance inspection that follows VDE 0100 Part 610 protocols and verifies compliance with DIN EN 62 446 standards. The array is tested by a licensed electrician. Since some of the work involves high voltages, the relevant technical rules for operational safety TRBS 2131 apply. The builder must record the inspection process. A notice of completion or an application to commission the array is sent to the appropriate electricity network provider, and initiates the process of connecting the photovoltaic installation to the grid. The PV installation is registered with the network provider using the network’s application form (VDE-AR-N 4105 Anh. G1), together with all required supporting documentation. Operational data acquisition

The functioning of PV arrays is automatic and, in general, hassle-free. However, in the absence of operational monitoring, interruptions or malfunctions are sometimes discovered only several months after they occur. Even though smooth functioning can be verified by checking the inverter display or the continuous operation of the electricity meter, experience shows that this kind of hands-on monitoring of the electrical yield is not reliably performed over long time periods. An annual reading of the feed-in meter is generally insufficient, since a

4.31 Degree of self-sufficiency or solar coverage of two building types with heat pumps as a function of the PV generator power; night-time room temperatures are lowered and a SG-ready interface as well as a battery are used. (Battery storage capacity: 6 kWh, annual electricity demand excluding heat pump: 4,000 kWh, living area: 140 m2) a) annual heating energy needs of 95 kWh/m2 b) annual heating energy needs of 25 kWh/m2

45

Technology and systems – photovoltaics

Frequency

Installation component

Every day

Inverter

• Check for display without error messages

Operations monitoring system (if present)

• Check for notifications, fault or failure messages

Every month

Yield monitor

• Check meter readings regularly Or verify operations via operation monitoring system

Every 6 months

Generator surface

• In case of significant contamination from leaves, bird droppings, air pollution or other sources – clean • Check if all modules, mounting components and cables are correctly attached • Check if generator surface is mechanically stressed (e.g. due to shifts in the roof truss, etc.)

Generator lockbox (if present)

• Check for insect incursions / moisture (if located outdoors) • Check fuses

Separate surge arresters (if present)

• Check after lightning storms • Verify that surge arresters are intact, viewing window is white/red

cabling

• Check for scorch marks, insulation breakage or other damage (such as chew marks from animals) • Check connections

Repeat tests and measurements performed at commissioning

• Requirement for PV installations subject to BGV A3 or TRBS 1201 • Testing according to DIN EN 62 446 and VDE 0105-100 to be performed by technician

once a year

Action

For central lightning protection and section switch

• Testing according to VDE-AR-N 4105 to be performed by technician

Every three to four years

Repeat tests and measurements performed at commissioning

• Recommended for all PV installations • Testing according to DIN EN 62 446 as well as VDE 0105-100 to be performed by technician

As needed

Modules

• Measurement of characteristic curve: thermographic test or functional analysis by expert

Generator lockbox (if present)

• Check fuses

DC wiring and contact points

• Testing (by thermography if needed) by electrician

DC safety equipment

• Check all DC and universal current-sensitive FI switches

AC safety equipment

• Check circuit breakers, AC fuses, FI switches and lightning protection 4.32

possible defect could exist for months without being noticed. And even significantly reduced yields could remain undiscovered by a cursory look at the annual statement. A comprehensive operational data monitoring system ensures that malfunctions and interruptions are flagged and quickly recognised. The owner can then take immediate measures to fix the problem and minimise potential losses. Many inverters record the pertinent operational data and thus facilitate basic monitoring of the photovoltaic array. They can register and report conspicuous errors in the array’s functions. The data can be read from a display and/or evaluated through a service programme on the computer or on the internet. The inverter, or a separate data-recording device, can perform part of the installation check automatically, but will generally recognise and flag only obvious problems like a system failure or residual currents. They can then signal the information via an audible alarm, for example, or send error messages by fax, e-mail, text or the internet. The operational data can also be downloaded to smartphones or tablet PCs, where further analysis can be done using appropriate apps. Maintenance

Technical installations that are exposed for years to wind and weather need regular maintenance. The maintenance effort required for photovoltaic arrays is generally 4.32 Recommended maintenance intervals for photovoltaic installations 4.33 Glare from a photovoltaic array

46

small. While a four-year maintenance cycle is recommended for private installations, according to the regulation BGV A 2 “Electrical facilities and equipment”, commercial PV installations must be inspected regularly. The inspections primarily serve to safeguard the safety of people and equipment. Part of the maintenance contract includes repeat testing set out in DIN EN 62 446, VDE 0100 and VDE 0105. A regular maintenance routine (Figure 4.32) performed by the operators of the array or by the installation firm helps to prevent faults and extended interruptions, optimising energy yields. Very simple things – the operations manuals (especially for the inverter) and good documentation for the installation, which should include maintenance recommendations – are very important for maintenance and upkeep. The error display of the inverter or the data monitoring system should be checked on a daily basis. In addition, the performance data should be read and verified at least once a month. Regularly inspecting the modules for dirt and debris is also important. In sufficiently inclined installations, the rain cleans the modules so that the losses in energy yield due to surface deposits are usually less than 2%. In installations that are heavily affected by soiling, on the other hand, regular cleaning of the modules can raise the solar yield by up to 10 %. The modules should be washed with plenty of water and a nonabrasive implement or device (such as a sponge), but preferably not with a detergent. They cannot be wiped dry or swept because this will scratch the surface. Professional cleaning systems that are approved by many module manu-

Requirements, standards and regulations

facturers have lately become available. In some installations, care must be taken to ensure that any plants in the building’s vicinity (such as vines) do not grow near or over the modules. Aged cable insulation or poor contacts can cause arcing and lead to fires. As a rule, such problems are caught in time by an insulation fault monitor in the inverter. This integrated safety feature shuts off the inverter and sends the error message on to the operations monitoring system. Since a small safety risk exists even after the inverter has been turned off, the operator of the installation should make every effort to locate and correct the problem as quickly as possible. To ensure that this maintenance work can be performed safely, permanent measures to prevent falls should be installed on the building.

Requirements, standards and regulations The construction and operation of PV installations are governed by numerous standards and statutory regulations. Building rights

According to the state building regulations, photovoltaic installations on roof or facade surfaces do not require a building permit. The building client and his contractor are, however, responsible for making sure that all applicable codes are followed, including the building rights, construction rules and standards, and any other requirements, in particular those concerning structural stability and fire safety. The responsibility extends to the regulations governing building products and building methods: Is the installation illegal? Could the authorities order it to be taken down again and demand a fine, to boot? The answers to these questions would be yes, for example, in the case of an installation with insufficient stability in its mounting system, especially if a public thoroughfare were endangered by this defect. Even though most PV installations do not require permits, three other procedures may apply: the exemption or notification procedure, the simplified building permit procedure or the conventional building permit procedure. The applicable building code describes the limiting cases of permit-free construction. If the building client is unsure of the status of his project, he may inquire at the building supervisory authority, or submit a construction notification to that authority. In the latter case the authority will determine, for a small fee, whether a permit application is necessary. For example, installing a PV array on residential buildings up to a certain size within a development could, according to § 30 Abs. 1 BauGB, require a notification procedure. This means that building clients cannot simply begin with the construction until they have completed a process in which they must hand in or produce certain building documents and certifications. Every building installation must conform to construction planning law. This law is set out in the building code book (BauGB: Baugesetzbuch).

Avoiding glare

Though obtaining the consent of neighbours for the installation of a solar array is not required, the neighbours do retain recourse to legal protections. Problems could develop, for example, if a facade installation produces glare due to the sunlight’s reflection off the module surfaces (Figure 4.33). The neighbour would have to prove that the glare from the array causes a serious nuisance. Customary local conditions are taken into account in these cases, meaning that in an urban setting, for instance, nuisances are considered more tolerable. The acceptability threshold for nuisance duration should be applied appropriately for the area. Furthermore, a reference document on the measurement, evaluation and reduction of light emissions published by the Federal and State Committee for Emissions Protection provides guidelines for determining the dividing line between acceptability and unacceptability [1]. Practical measures can be taken to reduce glare. Hedges or minimal changes in the orientation or inclination of the array, and even the removal of individual modules, can all provide relatively simple and inexpensive solutions to the problem. A glare report is needed to provide evidence of the problem and to plan the appropriate mitigation. A similar report is also required in cases where reflections from a PV array could adversely affect transportation (street, rail or air traffic). In normal rooftop PV installations this very rarely applies. Historic preservation

In a historically listed building, changes to the exterior are permitted only in limited form and require a special building preservation permit. This applies also to installations in the vicinity of the listed building, whenever these impact the building’s appearance. Building monuments are listed in the register of monuments and historic buildings maintained by the Lower Building Advisory Authority (Untere Bauaufsichtsbehörde). If the building is historically listed, it is advisable to communicate with the relevant building authorities in a very timely manner (Figure 4.34).

4.33

47

Technology and systems – photovoltaics

Model Building Ordinance, building regulations and building products

4.34

4.35

4.34 Refurbishment in compliance with historical preservation. Catholic Church in Heiden (CH) 2012, Alex Buob 4.35 For the attachment of PV modules to buildings using backrail systems, a national technical approval (abZ) issued by DIBt is required.

48

The Model Building Ordinance (MBO) provides a unified foundation for the building codes of the German states. In connection with PV installations, it is especially relevant when it comes to fire safety (clearance regulations) and references to building types and building products. The latter are regulated by the building rules list (Bauregelliste) of the German Institute for Building Technology (DIBt: Deutsches Institut für Bautechnik), in consensus with the building supervisory boards of the states. As of 2012, PV modules have been incorporated into Part 2 of the Bauregelliste B [2]. This rule applies to PV modules with mechanically mounted glass panels, each panel comprising a maximum area of 2.0 square metres, installed on a roof with an inclination angle ≤ 75°, as well as to building-independent solar arrays in publicly inaccessible locations. PV modules must then comply with the Low Voltage Directive 2006/95/EC and show their conformity by displaying the CE-marking. An information document put out by the DIBt [3] helps building authorities and designers manage the formal categorisation of solar technology and the identification of the applicable building ordinances. According to this document, the mechanical load tests and other tests of PV modules based on current IEC standards are not sufficient to supply the material characteristics that are necessary to prove conformity with the building code requirements, such as structural safety. For this reason, in incorporating PV modules in facades or in overhead glazing, the additional technical building regulations governing glass construction – particularly DIN 18 008-2 for linearly mounted glazing – must be followed. In standard modules, heat-strengthened (TVG) glass is usually used. In construction subject to the building code (for example, in overhead glazing or in facades) they are therefore classified among the unregulated building products and can only be utilised with a permit, test certificate or case-specific approval. Among the regulated glass products included in the Bauregelliste A, Part 1, are special glasses like cast or mirror glass, toughened glass (ESG), multi-pane insulated glass or laminated safety glass (VSG). Overhead glazing is tilted more than 10° with respect to the vertical. Thus, any protruding photovoltaic facade elements and sun protection installations must conform to the safety ordinances governing overhead glazing. Since it is a regulated building product, laminated safety glass is often used. In the past, for overhead solar modules this meant a three-layer heavyweight construction: on the bottom, two VSG panes with a PVB interlayer, topped by the solar cells in an EVA laminate and the upper glass pane. Nowadays, manufacturers also produce VSG solar modules in a two-layer construction, in which the cells are laminated with PVB foil instead of EVA. Vertical glazing departs from the perpendicular a maximum of 10°. One possibility is a facade system in which the glass panes are fixed with pressure plates. For rearventilated exterior cladding of ESG, DIN 18 516-4 applies, which, aside from linear mounting, also permits the use

Requirements, standards and regulations

of mounting clamps. The standard also allows the use of solar modules made of ESG in applications where the glass temperature will not exceed 80 °C. For these cases, special facade modules in an ESG-laminate construction are available. If the building method diverges from the acknowledged technical norms, the building client must obtain either a national technical approval (abZ) or a national test certificate (abP), or an individual approval (ZiE). These procedures are both costly and time-consuming. Consequently, unregulated building products and methods should be employed only in exceptional cases, when the cost of using building-code regulated modules and support structures exceeds the expense of obtaining the necessary certificate or individual approval. The abZ is issued by the DIBt for a five year period and is valid throughout Germany. A general national test certificate is obtained through a test centre authorised by either the DIBt or the Supreme Building Authority (Oberste Bauaufsichtsbehörde). For an individual approval, one must apply to the state Supreme Building Authority. Plastic and other PV modules without glass coverings certified according to IEC 61 215 or IEC 61 646 can be used with no size restrictions. Requirements for mounting and supporting structures

Thanks to the load reserves of most roof constructions, in general, the additional weight of solar modules and their mounting frames does not cause statics problems. Of course, the mounting system and its connections must be capable of supporting not only their own weight but also wind and snow loads safely and over the long term, and of redirecting those loads into the building, other structures, or the building site. The implementation of these requirements is governed by the list of technical building directives. Essentially, the wind- and snow load standards specified in DIN EN 1991-3 and 4 must be met in the design of the mounting system. The vendors of mounting systems often provide assistance in determining the appropriate size. The detailed system statics of the mounting system and the determination of the layout specifics (number of roof hooks, spacing of supports) can frequently make a complex individualised static analysis unnecessary. Verification is obtained via the aforementioned standards or through experimental evidence, such as load simulations on finite elements, particularly in the case of aerodynamic flat roof mounting systems. Steel and aluminium structures must conform to Eurocodes DIN EN 1993-1 and DIN EN 1999-1 as well as their applicable national addenda, and to execution standards specified in DIN EN 1090-1, 2 and 3. Since the structural safety and implementation of support structures made of stainless steel are not regulated by the currently valid technical building directives, national technical approval (abZ) No. Z-30.3-6 must be sought. Provided that the load-bearing capacity of metal constructions has been experimentally determined, their structural stability and durability require abZ certification. If, on the other hand, the load-bearing capacity has been numerically verified

on the basis of a technical building directive, such certification is not necessary. A national technical approval (abZ) is likewise required if significant sections of the mounting system consist of synthetic building components, or if the mounting supports or bracing elements of the PV module are glued. Whenever PV module connections are formed with adhesives, as in the case of backrails (Figure 4.35), an abZ must be obtained to certify their structural safety and durability. In PV facade systems, the European Technical Approval Guideline (ETAG) 002 for Structural Sealant Glazing Systems (SSGS) can be used. The application of the ETA guideline to slanted PV modules, however, leads to expensive and difficult constructions because of the high demands on facades and the associated high safety factors. For the anchoring and attachment of solar installations to the building, other structures or the foundations, or for their connection to the supporting structure, anchoring, attachment and connecting elements (bolts, dowels, anchors, anchor rails) should be used. These should conform to the technical building directives, or else should carry the CE-marking based on European technical specifications that identifies them as belonging to the fixed categories and performance levels of the Bauregelliste B, Part 1. The use of any other anchoring, attachment and connecting elements requires an abZ certification. Unregulated anchoring and attachment devices for concrete and masonry must meet European technical approval or national technical approval standards. To date, PV modules or mounting systems are only rarely glued to the roof surface or fused to the roof membrane. These so-called adhesive attachments to the roofing for the distribution of tensile forces are not yet part of the technical building code, and thus also require a building usage certification.

Glass construction regulations TRLV: The “Technical regulations for the use of linearly mounted glazing” (DIN 18 008-2) apply to PV modules that are employed either as vertical glazing with a maximal inclination from the vertical of 10° (facade), or as overhead glazing with a minimum 10° inclination relative to the vertical, and whose glass abuts other glazed modules on at least two opposite sides. TRAV: The “Technical Regulations for the use of accidental-fall-prevention glazing” (DIN 18 008-4) apply to PV modules that are used in glazing applications to prevent falls, for example in parapets. TRPV: The “Technical regulations for the measuring and implementation of point-mounted glazing” (DIN 18 008-3) apply to PV modules that are employed either as vertical glazing with a maximal inclination from the vertical of 10°, or as overhead glazing with a minimum 10° inclination relative to the vertical, and whose glass is point-mounted.

49

Technology and systems – photovoltaics

a

b

Fire protection

partmentalised in accordance with the Model Cabling Installation Guidelines (MLAR: Musterleitungsanlagenrichtlinie) (Figure 4.36). Otherwise, it is possible for the burning insulation material to spread the fire. Materials used for this must be suitable for outdoor applications. Fire walls must extend at least 30 centimetres above normally flammable materials and therefore above the upper edge of the PV generator. In normally flammable PV modules installed above the roof covering, a clearance of at least 1.25 metres to any fire walls must be maintained. Note: This separation applies equally to any building partition wall or property line. It is possible to lay cables across fire compartments as long as the cabling conforms to fire resistivity class S 90.

Fire protection concerns must be considered in the design and installation of PV arrays. The arrays must conform to the applicable fire protection requirements set out in the Model Building Ordinance, the technical fire protection regulations and the VDE norms stated in VDE-AR-E 2100. Fire protection requirements of the Building Ordinance The installation of PV arrays can in no way decrease the protective functions of roofs and fire walls. To prevent the spread of building fires to other buildings or building parts, the Building Ordinances of individual German states (LBO) and the Model Building Ordinance (MBO) specify various standards for buildings and roofs. These include, in particular, the requirement for “hard roofing” in roof-integrated solutions, as well as the utilisation of building materials classified as B 2 (“standard flammability”) according to DIN 4102 (old) or E in DIN EN 13 501 (new) in roof-mounted installations. Most PV modules with glass are categorised as class B 2 or E. In roof-integrated systems, the proof of hard roofing compliance is usually provided by the manufacturer in the form of building supervisory testing certifications. The MBO defines the mandatory spacing between materials of standard flammability and the fire walls. This is meant to prevent the spread of fire through flying sparks and heat radiation. In § 32, the MBO states that dormerlike roof structures of flammable materials must be located a minimum of 1.25 metres away from a fire wall. This logically applies to PV modules and other components of the array as well. According to the technical fire protection regulations, cables that pass through or over a fire wall must be com-

4.36 Cabling over a fire wall a) Faulty cabling over a fire wall. The fire can be spread to a neighbouring fire area by burning insulation b) Proper compartmentalisation of cabling over a firewall in a fire resistant enclosure 4.37 The most important roof variants with access points 4.38 Fire fighting accessibility in a) medium-sized roofs on buildings with an area smaller than 40 ≈ 40 m b) large roofs on buildings with an area greater than 40 ≈ 40 m 4.39 Measures for the prevention of dangerous accessible voltages to be taken in the installation of photovoltaic arrays as given in VDE AR-2100-712

50

4.36

Fire fighting requirements In some situations, gaining access through the roof into the attic space in order to extinguish a fire is unavoidable. A live electrical installation such as a PV installation could then pose a serious obstacle, especially if it spanned the entire roof surface. When both halves of a roof are covered, as is the case in east-west facing roofs, other roof access points like dormer or gable windows must be available for use (Figure 4.37). The windows must have the dimensions of an emergency egress and must be accessible to emergency crews. In the MBO, the minimum size requirements of such windows are specified as an unobstructed width of 90 centimetres and an unobstructed height of 120 centimetres. If the attic cannot be reached either by the rear roof surface or through a window, a suitably sized section of the roof must be kept clear. Emergency fire crews need a free strip only a metre wide to do their work. In roofs smaller than 40 ≈ 40 metres that lack any other access points, a one-metre-wide strip on the longer side should be kept free of obstructions. An additional centrally placed free strip is recommended for PV installations exceeding 20 metres in width. If the design calls for larger PV installations, the generator surfaces must be partitioned into sections with a maximum size of 40 ≈ 40 metres. Paths of at least a one-metre width must run between adjacent sections (Figure 4.38). Additional fire protection requirements During the day, the PV generator is subject to a voltage

Requirements, standards and regulations

of up to 1000 V that cannot be switched off, which can impede the job of the fire department in case of a fire. For this reason, regulation VDE AR-2100-712 requires that the possibility of dangerous, easily accessible DC voltages within the building during fires be avoided in the design and installation of PV arrays, so that personnel rescue and fire fighting activities can be engaged in safely. To this end, the regulation establishes several appropriate measures. These measures are listed in Figure 4.39. Apart from labelling and the establishment of contingency plans, the primary way to achieve safety is through buildingrelated means, such as placing the DC components outside the building or ensuring that cabling is fire-protected. Other technical possibilities such as the fireman’s switch, though frequently mentioned in the building ordinance, are problematic in that they do not fit into the standard classification scheme, and therefore lack testing protocols. These building-related measures are less expensive, and yield high safety benefits with minimal risk of failure.

North side

South side

West side

East side

West side

East side Roof dormer

Electrical regulations and standards

The construction of a photovoltaic array involves a multitude of electrical regulations established by various regulatory boards and facilities. The assembly and installation of PV arrays must be carried out in compliance with the existing VDE provisions, and in particular, with all applicable parts of the series of provisions VDE 0100 pertaining to electrical installations, as well as with VDE 0298-4. Special requirements for the installation of PV arrays are given in VDE 0100-712 and VDE 0126-23 (DIN EN 62 446). Lightning and overvoltage protection is covered in parts 1 – 4 of VDE 0185-305. The technical regulations governing the connection of an installation (including a PV installation) to the electrical grid are specified in provision VDE-AR-N4105.

4.37

and area rface u s m x 40 < 40 walls e ir f no a

3,5 ≈ Δh < 10 % Insignificant γv > 63° ∫ dv > 2 ≈ Δt Shaded areas (γh > 12° in easterly – southerly – westerly direction) should not be covered with PV modules or cells If needed, choose electrically inactive dummy modules, coloured / printed glass or other space fillers

Customised electrical wiring can reduce losses if needed

As a rule, cleaning is not cost-effective; check regularly for localised dirt / contamination

Few percentage points; Given in steps 3 and 4 9.4

Compared to the typical roof-top array, building-integrated PV systems are associated with higher costs. Even though inexpensive, mass-produced standard modules can often be used in the plane of the roof, a high-quality design and a meticulous on-site implementation of the connection details result in additional expenses. The stylistic aspects and structural demands of facade integration, on the other hand, often require custom-made modules. This can easily raise the module prices by a factor of 1.5 – 3 as compared to standard modules. Up until now, the mostly customised solutions and the dynamic cost development have not allowed for generally applicable pricing characteristics. The design complexity of facade integration precipitates not only the higher module costs but also a rise in the proportional budgeting of secondary construction costs, which may include such items as expenditures for planning and permits. As a consequence, building-integrated PV arrays can be seen as economical only in light of their multifunctional aspects, for example when they replace the customary roof coverings or facade cladding, or if they eliminate the need for additional sun protective measures. Even in comparison to the building components they replace, the investment costs for PV modules and the associated electrical sys-

tem technology are usually greater (Figure 9.2). The initial additional outlays relativise themselves over the lifetime of the array, however, because the production of solar electricity generates revenue. Yields

In Germany, ideally oriented, well-ventilated and essentially unshaded PV roofs generate an average of 890 – 1,020 kWh of solar electricity per peak kilowatt per year; for south-facing PV facades the range is about 600 – 700 kWh. For crystalline modules with a high cell surface density and an efficiency of 15 %, this corresponds to approximately 130 – 150 and 90 – 105 kWh/m2/year, respectively. Modules with different cell types or with customised variations in colour or partial transparency will exhibit lower specific yields proportional to their efficiencies (Figue 9.3). Given the location, surface orientation and integration situation, the average expected yield over the longer term can be estimated using regional global radiation and yield values (Figure 9.4) as well as proportional conversion factors. In building integrations where the array lacks rear-ventilation or is insulated – as in insulating glass or sandwich panels, for example – the energy yield will be reduced, since these modules are 95

Economy and ecology

100%

Self-consumption

80% Solar electricity generation

Charging of battery

60%

40% Electricity use Household Commercial

Feed-in to grid

20% Solar coverage 0%

Grid supply Midnight

Discharging of battery

Direct use 6 am

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6 pm

Midnight 9.5

exposed to higher operating temperatures, which in turn negatively impact the efficiency of solar cells. For this same reason, east-facing surfaces tend to generate greater yields than their west-facing counterparts, since by the time the sun hits the latter in the afternoon they will already have heated up. Because of competing design goals such as daylight utilisation, self-shading from the building volume itself cannot always be avoided even in new constructions. In planning mounting fixtures, roof structures and lightning protection installations, careful attention should be paid to potential shading of the active solar surface, since the hard shadows cast on modules by objects in the immediate vicinity can have especially serious consequences. A solar-geometric analysis of the surroundings makes use of the daily and seasonal progression of shadows to generate a back-of-the-envelope estimate of expected shading losses. Some cell technologies present promising advantages in the building shell. Thin film modules, for example, react less sensitively to shading, since the long, narrow cell strips are not as easily completely obscured. As long as a shadow falls perpendicularly across the cell strips, the reduction in efficiency is – up to a certain point – proportional only to the affected cell area. In addition, increases in temperature impact the efficiency of thin film modules less than for crystalline solar cells, so that in cases of poor rear ventilation the specific yields of thin film modules can end up being a few percentage points higher. Manufacturers of organic solar cells posit additional

9.5 Increase of self-consumption through the use of batteries 9.6 Effect of installation size, usage profile and battery system (here: 1 kWh storage capacity per 1 MWh electricity consumption) on the self-consumption and solar coverage percentages 9.7 Sample calculation of profitability. Assumed values: interest rate 3.0 %, operating costs €30 /kWp increasing at 1.0 %/yr, net electricity price 19 cents /kWh increasing at 2.0 % / yr, PV power degression -0.25 %/yr, EEG compensation Version 1: 12.21 cents/kWh = (12.32 cents / kWh ≈ 10 kWp + 11.97 cents / kWh ≈ 4.4 kWp) / 14.4 kWp, Versions 2 and 3: 12.27 cents / kWh. EEG tax on self-consumed electricity, starting 2017: 40 % of 6.354 cents / kWh, taken to be constant. If a high electricity usage of 40 MWh / yr is assumed, the self-consumption increases to 86 % (Version 1) and 92 % (Versions 2 and 3). 9.8 Development of the net present values of the example PV facades compared to those of various alternative facades, assuming annual electricity consumption of 20 MWh or 40 MWh

96

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1.5 2.0 2.5 PV power [kWp/MWh electricity use]

Household without battery Commercial user without battery

Household with battery 9.6

yields of up to 20 %, because for these cells efficiency actually rises for increasing temperatures up to 60 °C. Self-consumption

As a result of grid parity, profitability is influenced not only by the total annual energy yield but also by the relative rates of self-consumption and feed-in or direct marketing of solar electricity. A high self-consumption percentage is lucrative in that it maximises revenues by saving the cost of the equivalent amount of grid-supplied electricity. In the absence of a battery, self-consumption is limited to direct consumption (Figure 9.5). As the intersection between the generation and use profiles, the direct consumption depends on the type of usage. The quantity and timing of electricity demand are very different in households, schools, administrative buildings and in continuously functioning industrial enterprises. Bulk use during the day and in summer between the hours of 8 am and 6 pm (as for electric air conditioners, for example) has a positive impact on the self-consumption percentage. A heat pump that draws most of its electricity during the winter months may worsen the overall seasonal profile, but its additional electricity use increases the potential self-consumption, particularly during transitional periods. The size of the PV installation and its associated annual yield in relation to electricity usage also play a significant role (Figure 9.6). At a peak power of 1 kW per MWh (= 1,000 kWh) of annual electricity use, a PV installation generates about as much electricity as is needed in the building over the course of a year. Private households can use only about 30 % of this amount directly, while the percentage is closer to 50 % for commercial and communal users, since the bulk of their electricity demand occurs during the daytime. For larger installation power, the self-consumption percentage drops, since the disproportionately more frequent surpluses must be fed into the grid. The reverse is true for the behaviour of the solar coverage, also known as the degree of self-sufficiency. This is a measure of the fraction of total electricity use that no longer has to be drawn from the grid thanks to self-consumption. As the power of PV installations increases, the solar coverage grows at steadily decreasing rates.

Profitability of PV installations

Example: 100 m2 cold facade South-facing office building in Berlin, commissioned 1st June 2016 PV facades

PV version 1

PV version 2

PV version 3

Module type, efficiency Module surface area, power

Crystalline, near-standard, 15 % 96 m2, 14.4 kWp

Crystalline, custom module, 12 % 96 m2, 11.5 kWp

CIS BIPV, standard, 12 % 96 m2, 11.5 kWp

Yield calculation (see Figure 9.4) 1. Horizontal global radiation 2. Specific yield for roof, 30° south 3. Conversion, 90 ° south, rear-ventilated 4. Shading losses

1030 kWh/m2/yr 1,030 kWh/m2/yr ≈ 0.9 m2/kWp = 927 kWh/kWp /yr 927 kWh/kWp ≈ 69 % = 640 kWh/kWp /yr 640 kWh/kWp ≈ 95 % = 608 kWh/kWp /yr 8752 kWh/yr =ˆ 88 kWh/m2/yr

7,002 kWh/yr =ˆ 70 kWh/m2/yr

Self-consumption Net electricity cost savings, 1st year EEG tax on self-consumed electricity

67 % =ˆ 5,895 kWh/yr € 1,120/yr € -150/yr

73 % =ˆ 5,145 kWh/yr € 978/yr € -131/yr

73 % =ˆ 4,285 kWh/yr € 978/yr € -131/yr

Feed-in amount EEG compensation

33 % =ˆ 2,857 kWh/yr € 349/yr

27 % =ˆ 1,857 kWh/yr € 228/yr

27 % =ˆ 1,857 kWh/yr € 228/yr

Net total revenue, 1st year

€ 1,319/yr

€ 1,075/yr

€ 1,075/yr

Investment costs for PV facade Operating costs for PV facade, 1st year

41,306 € € 432/yr

€ 67,842 € 346/yr

€ 35,059 € 346/yr

Alternative facades Investment costs Operating costs

ETICS € 10,000 € 400/yr

Back-ventilated curtain facade, fibre cement /glass € 28,639 € 220/yr

Back-ventilated curtain facade, composite resin € 38,112 € 340/yr

Yield Annual electricity usage

7,002 kWh/yr =ˆ 70 kWh/m2/yr

20 MWh

9.7

scription price of 19 cents per kilowatt-hour, and after the EEG tariffs and the tax due on the self-consumed electricity are subtracted, the self-consumption scenario initially shows only a slight income advantage over a full feed-in scenario with an EEG compensation of less than one cent per kilowatt-hour. However, due to anticipated electricity price developments, this advantage grows at an increasing rate over the course of subsequent years of operation. When contrasted with an inexpensive thermal insulation system, even near-standard modules deployed on a minimally shaded south-facing facade prove to be uneconomical. Compared to alternative cold facades with glass or fibre cement cladding, the standard/near-standard PV amortisation period lies between 7 and 14 years, while expensive custom modules fail to achieve a positive cost-benefit balance even when contrasted with high-quality facade coverings.

Net present value [€/m2]

Both self-consumption and solar coverage percentages can be increased through the implementation of energy management systems. Whenever possible, such systems use weather predictions to shift the operations of large electrical loads to times during which solar electricity surpluses occur, so as to better match usage profiles to generation profiles. Household appliances such as washing machines and dishwashers offer limited opportunities in this regard. A further option lies in the managed charging of electric cars. The greatest potentials, however, are found in the load management of industrial processes as well as in the solar-optimised operation of electric heat pumps for thermal use and, where applicable, the storage of solar electricity for the building heat supply. On the production side, a combination of east and westfacing arrays and the utilisation of facades can smoothe out the solar electricity generation profile. A further increase in self-consumption and self-sufficiency is achieved through the use of batteries, which absorb surpluses and store them temporarily for later on-site use after sunset. Single-family houses and plus-energy buildings, both of which exhibit a relatively low self-consumption percentage due to the proportionately high PV power output, are especially good candidates for batteries. In these cases, batteries are so near to being economical that their integration into the system reduces the net positivity of the PV array’s balance sheet but does not shift it into the red.

0 -100 -200 -300 -400 -500 -600 -700

Example

Figures 9.7 and 9.8 give examples of the cost-effectiveness of PV facades for mid-level module costs as well as the cost-effectiveness of possible alternative solutions. For a three-storey office building, two potential values for the annual electricity usage are entered, yielding different self-consumption percentages. For an assumed sub-

-800 2016

2021

2026

2031

2036

Back-ventilated curtain facade, fibre cement/glass ETICS Back-ventilated curtain facade, composite resin PV version 1 PV version 1, High electricity usage 40 MWh/yr PV version 2 PV version 2, High electricity usage 40 MWh/yr PV version 3 PV version 3, High electricity usage 40 MWh/yr 9.8

97

Economy and ecology

Irradiation of roof, 45° south

Existing buildings

Irradiation of facade, 90° south

EnEV 2016 Passive house Solar yield, facade 90° S Solar yield, roof 45° S Heat energy needed for heating water Heat energy needed for space heating

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System costs

For single-family houses the gross installation prices lie in the range of about €850 to €1,000 per m2 of collector surface, and for mid-sized installations of 20 – 100 m2 they typically vary between €500 and €850/m2. A onetime retrofit in an existing building will cost approximately 10 % more. Yields

90 75 60 45 30 15 0 -40

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Inclination angle [°]

In contrast to photovoltaics, solar thermal installations cannot feed their surpluses into an existing nationwide public network. Any solar heat that exceeds the selfconsumption needs of the building is thus unusable and unprofitable. This leads to a strong interdependence between the generated heat and the heat demand profile, and to fundamentally different yield potentials for systems used for water heating versus those intended for space heating support, for example. Since the demand for hot water remains essentially constant throughout the year, water heating dovetails much better with the generation profile of solar collectors than does space heating (Figure 9.9). Systems meant purely for water heating therefore achieve high yields as a function

98

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of collector area, but can contribute in only limited ways to overall heating needs. In comparison to water heating installations, combination systems in residential buildings require a collector surface at least two to three times larger in order to produce sufficient solar heat during the heating season. In summer, this signifies unusable surpluses. The excess production in turn reduces the utilisation rate, the yield and, ultimately, the cost-effectiveness of the installation. On the other hand, solar coverage increases, since most of the heat demand – about two thirds in new buildings that comply with the Energy Saving Ordinance (EnEV) – comes from space heating. A further enlargement of the collector area would only raise the solar coverage by minor amounts, unless the storage tank capacity were increased significantly in order to allow some of the summer’s surplus heat to be used in winter. In determining the size of the collector surface, the architect must strike a balance between high efficiency on the one hand and significant replacement potential of conventional heating energy on the other (Figure 9.11). The desired solar coverage must be agreed upon and set as a design goal by building client and architect together. Small installations of private-sector building clients are generally laid out so as to maximise coverage. Commercial investors, on the other hand, make profitability a priority. This results in smaller collector areas with greater yields, since as the utilisation (the heat demand per

Yield [%] 105–100 100–95 95–90 90–85 85–80 80–75 75–70 70–65 65–60 60–55 50–55

Inclination angle [°]

As the size of a solar thermal system increases, its specific costs per square metre of collector area decrease.

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Profitability of solar thermal installations

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90 75 60 45 30 15 0 -90 -60 West

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90 East 9.10

Profitability of solar thermal installations

Max. yield per m2

Maximum consumption coverage

– Cost-benefit optimum Solar coverage fraction

suited to combination installations, which achieve up to 86 % of the energy yields of optimally oriented roof installations. In water-heating installations this number is 75 %. For increasing solar coverage these percentages grow for combination installations and decrease for hot water systems. The shading analysis follows the same procedure as for photovoltaic installations, though the criteria here are less stringent – the efficiency of partially shaded collector fields is reduced in proportion to the drop in incident radiation and can be offset with larger surfaces. However, certain unfavourable plumbing layouts can cause unnecessary losses to occur; for example, if the heat transfer medium were to flow serially through the collectors, it could heat up in a sunny portion of the field only to cool down again in a shaded region. Heat production cost

One of the the characteristic values describing the profitability of a solar installation is the heat production cost. This describes how much it costs overall to generate one kilowatt-hour of usable heat, and thus allows comparisons with other heating supply systems. Using the annuity method, the initial investments and all future or annually recurring costs over the lifetime of the installation, taking into account rates of return and price increases, can be converted to an average annual figure and compared to the yearly energy revenue. Any applicable subsidies, as well as the cost savings due to the replacement of roof and facade components by building-integrated collectors, should be subtracted from the investment total. Running expenses consist of the costs of the electricity required to run the pumps and of the maintenance and repair work. Because of the proportionately lower investment costs and generally higher yields of large installations, the solar heat production costs for these are usually lower than for small installations. Large systems for water heating reach the cost-effectiveness threshold already at 8 – 10 ct/kWh. Because of their modest yields, unglazed air collector facades can only preheat outside air, but they do this at very attractive heat prices of only few cents per kilowatt-hour since they cost little more than conventional facade systems. In the sample calculation given in Figure 9.12 (page 100), the compactly installed combination system (Version 1) for an apartment building turns out to be economically viable (assuming market-based estimates for capital and running costs) if the energy prices for the conventional

9.9 Monthly heat demand and typical solar yields from roof and facade collectors for a water heating b water and space heating 9.10 Proportional annual energy yield according to DIN V 18 599 for variously oriented collector surfaces with respect to the south-facing 45° optimum. The values vary according to solar coverage. a installations used for water heating b combined-purpose installations 9.11 Qualitative relationship between utilisation factor and coverage fraction used in determining the size of the collector area

−

Coverage fraction Utilisation factor

+

square metre of collector surface) increases, so does the yield. For existing buildings, smaller solar coverages are better suited depending on the energetic conditions of the building shell. If the insulation standards are poor, with proportionately high wintertime heat requirements, only a small solar contribution will be economically feasible. The temperature levels during heat transfer also influence the yield. Surface heating systems such as floor, wall or ceiling heaters allow for greater yields than radiators, since solar collectors can transfer usable heat to systems operating at low temperatures even during periods of moderate solar irradiation, and generally reach higher efficiencies under these conditions. The factor that has the greatest influence on achievable energy yields is the amount of solar irradiance on the collector surface, which is determined by the location, inclination, orientation and possible shading of that surface. The largest annual yields are generated by south-facing collectors. Since only the heat that is actually used counts as yield, the optimal inclination angle varies by type of use. For cooling purposes, high summer energy harvests are important; in middle and southern Europe these are achieved with a 20° inclination angle with respect to the horizontal. For water heating the ideal angle is about 45°, which efficiently covers the essentially flat demand over the entire year. The collector surfaces of combined-purpose installations are optimised for the low solar elevations during the radiation-poor heating periods, resulting in a 60° tilt. The steep collector surfaces also produce less surplus heat during summer. If the orientation deviates from due south, the yield decreases (Figure 9.10). The collector plane can be raised to achieve the same solar coverage and yield as for an optimum orientation. For the compactly sized systems designed to heat water, only a few percentage points in yield differentiate the south-oriented collector surfaces from those facing south-east or south-west. The yields of combination systems, however, suffer more from such deviations. Orientations facing due east or west are to be avoided. In residential buildings with their typical evening usage, a south-west orientation is preferable to south-east. This effect is magnified for vertical surfaces such as facades. Facade collectors are especially well

Collector area + Utilisation factor of the solar energy system 9.11

99

Economy and ecology

Example: collector facade of an apartment building, for water heating and space heating support Design goal

Version 1: high efficiency

Version 2: extensive substitution

Solar coverage Collector area

25 % 50 m2

50 % 160 m2

Investment costs Facade cost savings (thermal insulation system) Subsidy 1) Remaining investment ∫ annuity Operating costs (maintenance, repair) Usage costs (auxiliary energy for pumps)

€ 38,250 € -5,000 € -15,300 € 17,950 ∫ € 1,031 € 340/yr ∫ € 378 € 96/yr ∫ € 134

€ 93,600 € € -16,000 € € -37,440 € € 40,160 € ∫ € 2,306 € 832/yr ∫ € 926 € 197/yr ∫ € 275

Specific yield Annual yield Solar heat production costs

344 kWh/m2/yr 17,200 kWh € 1,543 /17,200 kWh = 9.0 cents/kWh

220 kWh/m2/yr 35,200 kWh € 3,507/ 35,200 kWh = 10.0 cents/kWh

Savings in final energy Conventional energy costs (averaged over 25 years) Savings in energy costs (annuity) Amortisation period Revenue

22,933 kWh/yr 12,4 cents/kWh € 2,057/yr 17.8 yrs 6.5 % per yr

64,933 kWh/yr 12,4 cents/kWh € 4,677/yr 19.9 yrs 5.3 % per yr

Existing building modernisation Investment costs Remaining investment Solar heat production costs

Version 1 a € 42,075 € 20,245 ∫ € 1,163 9.7 cents/kWh

Version 2 a € 102,960 € 45,776 ∫ € 2,629 10.9 cents/kWh

Cost-effectiveness for tenants: compensation of rent increase through energy savings Increase in rent (excl. heating costs, all tenants combined) Operating costs of solar installation Savings in energy costs Change in rent (incl. heating costs)

€ 1,518/yr € 513/yr € -2,057/yr € -26/yr

€ 3,433/yr € 1,201/yr € -4,677/yr € -43/yr

Cost-effectiveness for landlords: refinancing of remaining investment 2) through rent increases Amortisation period 17.3 yrs Revenue 8.4 % per yr 1) 2)

17.3 yrs 8.4 % per yr

17.3 yrs 8.4 % per yr

Financing example: “Premium” KfW programme for renewable energies with a 40 % repayment bonus, as of 06/2016 Financing example: 10-year loan at 3 % interest 9.12

heating system it replaces rise by at least 2.3 % per year. In Version 2, which has high solar coverage, the somewhat lower costs per unit area cannot compensate for the reduction in efficiency. Nevertheless, the investment remains profitable as long as conventional heating costs grow at an annual rate of 3.2 % or more. For an assumed annual increase of 5 %, the two installations generate rates of return of 6.5 % and 5.3 % per year, respectively. In the modernisation of existing buildings (Versions 1a and 2a), landlords can shift up to 11 percent of the investment costs to the net annual rent. If they limit themselves to a refurbishment increase of 7.5 %, they themselves still benefit overall from the use of solar energy, while their renters break even because the increase in net rent is balanced by their energy savings. Due to the large uncertainties inherent in choosing an appropriate interest rate and predicting the energy price developments over a 25 year lifetime, calculations of profitability can yield only rough estimates.

9.12 Sample profitability calculation for two different south-facing flat plate collector facade designs in Berlin. Assumptions: heat energy demand for water and space heating 70,000 kWh /yr, interest rate 3.0 %, service life of the solar installation 25 years, operating cost increases of 1.0 % /yr, usage costs 2.0 % of the usable solar heat yield, gross electricity price 28 cents/kWh increasing at 3.0 % /yr, initial conventional energy costs 7 cents/kWh increasing at 5.0 % /yr, annual utilisation factor of the heat generator 75 % 9.13 Ranges of the sizes, annual yields and heat production costs of solar thermal roof installations (unsubsidised) 9.14 Estimates of energy payback periods for roof and facade-integrated PV arrays with different cell types in Central Europe (efficiencies given in %)

100

Ecological assessment In their operation, solar installations require no fuels and produce no direct emissions, toxic waste or noise. The systems are not completely free of negative environmental effects, however, since their manufacture consumes energy and resources. In solar thermal installations, the auxiliary electricity used in the operation of circulating pumps and the energy management systems during their active phases must also be considered. A comprehensive ecological audit therefore requires a look at the complete life cycle, taking into account the ecological rucksack of the up and downstream processes ranging from the extraction of raw materials to the recycling phase. The method most suited for this is known as life-cycle assessment. In this assessment, all the energy and material inputs and outputs along the process and transportation chains are identified and used to calculate indicators for their environmental impact. For solar energy systems, the decisive values are mainly the energy amortisation period and the specific CO2 emissions. The effect indicators depend linearly on yield (minus the auxiliary energy required for operation). For this reason, the geographical location, the orientation and inclination – and for solar thermal systems, the solar coverage – are of critical importance. Extensive environmental impact studies exist for gridconnected PV systems. Thanks to the fast-paced market and technology developments, however, these always amount to snapshots of production standards that are already outdated. Since the manufacture of the silicon wafers, solar cells and modules represents such a large fraction of the entire energy and material costs, increases

Ecological assessment

Installation type, purpose

Coverage of heat energy demand Hot water

Overall, new building

Overall, existing building

Yield, flat-plate collector (evacuated tube collector: ≈ 1.2)

Price of solar heat (evacuated tube collector: ≈ 1.2)

Water heating 10 – 20 % 4–8% (passive house: 25 – 30 %)

300 – 350 kWh/m2/yr

15 – 20 cents/kWh

25– 35 % 50 %

6– 9 % 12– 15 %

3– 5 % 6– 8 %

450 – 550 kWh/m2/yr 350 – 450 kWh/m2/yr

10 –14 cents/kWh 12 – 17 cents/kWh

1–2 families, standard 1–2 families, ambitious Apartment building Seasonal storage Solar heat networks

60 % 60 % 60 % > 60 %

15 – 30 % 30 – 45 % 14 – 30 % > 50 % 5 – 50 %

10 – 20 % 20 – 40 % 8 – 20 %

250 – 300 kWh/m2/yr 200 – 250 kWh/m2/yr 300 – 400 kWh/m2/yr 280 – 350 kWh/m2/yr 350 – 550 kWh/m2/yr

18 – 26 cents/kWh 22 – 30 cents/kWh 13 – 18 cents/kWh 21 – 24 cents/kWh 5 – 15 cents/kWh

Unglazed absorbers

30 – 35 %

150 – 400 kWh/m2/yr

10 – 15 cents/kWh

Air collector installation Facade, unglazed

15 – 50 %

70 – 360 kWh/m2/yr 60 – 400 kWh/m2/yr

3 –74 cents/kWh 3 –15 cents/kWh

Small installations (1–2 families) Large installations a) goal: high efficiency b) goal: extensive substitution

60 %

Combination installations

5 – 50 %

20 – 50 % < 50 %

9.13

in efficiency – and, for crystalline cells, decreases in wafer thickness and kerf losses – play an important role. As in the past, continued technological advances will further reduce the environmental impacts of solar electricity. In terms of the CO2 footprint of crystalline modules however, the increasing relocation of production facilities to China, where a high percentage of electricity is derived from burning coal, has cancelled out the positive trends from concurrent technological advances. Building-integrated photovoltaics, particulary in facades, have thus far been insufficiently analysed. Unfavourable irradiation and temperature conditions for these installations frequently decrease yield. On the other hand, the costs saved on module frames and support structures, as well as by the replacement of other types of building components, can be listed as credits. Consequently, the results of life-cycle assessments cover a broad range. Energy balance

The energy payback period describes the time it takes for a renewable energy system to generate the amount of energy required in its manufacture, operation, disassembly and recycling. After this time period, the system has a net positive energy balance. The balancing process is based on primary energy. PV yields, for example, are assessed using the primary energy factor for feed-in electricity specific to the state in which the array is located, even if some of the electricity is actually selfconsumed. PV installations with thin film modules, despite their smaller efficiencies and the greater mounting and wiring costs associated with their larger surface area requirements, amortise faster than those with crystalline modules, since significantly less energy is used in the manufacture of thin film cells. For ideally oriented arrays with crystalline modules, the energy payback period in Central Europe lies between 1.9 and 3.0 years. For thin film modules, it is about 0.9 to 1.3 years (Figure 9.14). These time spans lengthen to 1.3 – 4.5 years for south-oriented facades and 1.6 – 5.7 years for east or west-facing arrays. If one includes a credit reflecting the primary energy savings for the substituted building components, the amortisation periods can be shortened by 1 – 50 % (up to 0.9 years), depend-

ing on module type and building component material. In locations in southern Europe where irradiation levels are higher, the energy costs are recouped faster. The solar thermal sector reports energy payback periods in Germany of 1.5 to 2 years for water-heating installations and 2 to 4 years for combined-purpose installations. In facade systems, this time span can increase to up to 5 years. The differences between flat plate and evacuated tube collectors are small, since the somewhat higher yields of the evacuated tube collectors are compensated for by the higher energy demands of their manufacture. Emissions

Since fossil-fuel production of electricity and heat releases large amounts of climate-damaging greenhouse gases into the atmosphere, the CO2 equivalent represents the central environmental indicator for the energy sector. This single value encompasses the total emissions of climateimpacting gasses for a given process. The amounts of carbon dioxide, methane and nitrous oxide released are weighted according to their individual greenhouse effects. A comparison of the CO2 equivalent for lifecycle emissions and the energy generation during the operational lifetime of a system yields its specific emissions. For solar electricity produced by a PV installation in Central Europe, these are on the order of 20 to 197 g CO2-eq/kWh (Figure 9.15, page 102). Since the feed-in or self-consumption of the PV electricity displaces electricity from the municipal Polycrystalline Si 14.1 % Monocrystaline Si 14.8% CdTe 11.9 % CIGS 11.7% 0

1

2 3 4 5 6 Energy payback period [years]

PV roof, south PV roof, east/west PV facade, south PV facade, east/west Credit for roof covering/facade cladding 9.14

101

Economy and ecology

Monocrystalline silicon 14.8 %

Raw materials and recycling

CdTe 11.9 % Germany Austria Switzerland Poland Slovakia Slovenia Czech Republic Hungary 0

500

1000 1500 CO2 footprint [g CO2-eq/kWh]

PV roof, south PV roof, east/west PV facade, south PV facade, east/west Grid electricity mix (2010)

9.15

grid, the specific emissions value can be approximated by calculating the emissions avoided through the reduced use of grid electricity. The latter emissions values, in turn, depend on the electricity mix used at the location of the installation. The bottom line in most European countries reveals clear reductions in the environmental burden. As the renewable energy fraction of the electricity mix grows in future, this relative savings effect will decrease. Analogously, typical solar collector installations in Germany have specific emissions in the range of 20 – 60 g CO2-eq per kWh of generated heat, which corresponds to emissions reductions of 240 to 320 g CO2eq/kWh as compared to gas and oil furnaces [1]. Toxic substances

Depending on cell type, various heavy metals with special human toxicities are found in solar modules. In crystalline silicon modules, the 1 – 7 grammes of lead per square metre are a result of the fact that most manufacturers still employ leaded tin solder. Thin film modules with CdTe solar cells contain cadmium – typically less than 10 g/m2 – while CIS solar cells contain about 4.5 g/m2 of selenium and, depending on the manufacturer, small amounts of arsenic and cadmium. These substances, however, are not released into the atmosphere during operation. Even fires pose no elevated risk to humans or the environment [2]. On the other hand, since they displace grid electricity generated by nuclear fission, solar installations represent a reduction of the environmental burden in terms of radioactive waste, especially in countries that depend heavily on nuclear power. The potential for material toxicity in the solar thermal sector is limited to the anti-freeze used in the heat transfer medium and to the collector insulation. Products featuring the “Blue Angel” eco-label are guaranteed to use anti-freeze that does not contain climate-damaging halogenated hydrocarbons, and environmentally friendly insulating materials that were not foamed using objectionable propellants and that do not outgas toxic substances at maximum collector temperatures. 9.15 Greenhouse gas emissions of PV arrays compared to those of electricity drawn from various national grids 9.16 Consideration of solar installations within the scope of EnEV and EEWärmeG requirements

102

Silicon, the basic material used in most of the solar cells produced world-wide, is available in almost unlimited quantities. The silver used in the contacts of silicon cells will be increasingly replaced by copper. This essentially reduces the demand for potentially critical raw materials to tellurium and indium for CdTe and CIS thin film modules. Recycling of production wastes as well as of defective or worn-out modules makes it possible to recover valuable raw materials, while simultaneously improving the energy balance of PV systems. As a rule, the bulk of a PV module’s mass consists of glass. This is as readily recycled as the support structure, the aluminium frame (if present) and the copper in the wires and contacts. Recycling methods have now been developed that can recover silver and silicon, and that remove the semi-conducting coating of thin film modules from the crushed glass with little loss. Technically it is possible to reuse 95 % of the recycled materials in new solar modules or other products [3]. The EU Waste Electrical and Electronic Equipment (WEEE) Directive requires manufacturers to take back PV modules free of charge and to recycle at least 85 %. The task before the industry now lies in ramping up the logistics for collection systems and processing facilities of sufficient capacity to handle the huge volumes of module waste that are anticipated beginning in about 2030. The simple construction of solar thermal installations and their use of easily reusable materials such as copper, aluminium, and glass (wthout the rubber seals) allow for good recyclability. However, no special disposal mechanisms exist. Manufacturers whose collectors bear the “Blue Angel” eco-label are obligated to take back the building components and ensure that they are earmarked for reprocessing.

Energy certification and green building labels The plan for the buildings of the future is to make them climate-neutral and to supply them with 100 % renewable energy. In this context, wiewing building-integrated solar energy systems as individual measures, is increasingly moving into the background. The goal of an economical and ecological assessment instead lies in finding the most practical combination and layout of a comprehensive overall system. The legal requirements take this into account insofar as they assess the building shell and the installation technology together. Thus far, regulatory authorities have dealt only with energy demand during the service life of the installations. In light of the growing awareness of the need for sustainability, the building industry, on its own initiative, is developing comprehensive evaluation procedures to recognise environmentally and user-friendly buildings. Their requirements exceed those of the statutory minimum standards and comprise the entire life cycle. Through this comprehensive approach, sustainability certification offers a way to appreciate the multifunctional aspects of building-integrated solar systems.

Energy certification and green building labels

EnEV calculation with no solar energy system Generation Transformation Transport · fP

Adjustments for photovoltaics

Adjustments for solar thermal systems

Requirements, EEWärmeG

Transformation Storage Distribution Transfer 100%

· fP

Overall efficiency of building services

≥ 15 % fP = 0

Primary energy

Final energy

End use energy

Heat demand for hot water Space heating demand Non-residential building: energy demand for lighting and air conditioning to be added

Primary energy

Final energy

Primary energy

Heat demand, building services Electricity demand, building services Qualifying solar yield Non-qualifying solar yield

Final energy

15% 0% Final energy

Primary energy demand, heat supply Primary energy demand, electricity supply

9.16 Legal requirements and new standards

In Germany, the Energy Saving Ordinance (EnEV) implements the targets set by the European guidelines for the overall energy efficiency of buildings. New constructions must adhere to strictures setting upper limits for heat losses through the building shell and for primary energy requirements. The latter takes into account the overall efficiency of the heating system and, through the prime energy factor, the upstream production chain of the energy suppliers. In these assessments, solar thermal systems are considered part of the equipment technology and improve the primary energy balance, since the primary energy factor for solar energy is fP = 0. Photovoltaic electricity can be subtracted from the total energy requirements if it is generated and consumed in the building itself. This simultaneously reduces the primary energy needs of the building. Solar energy installations therefore allow the owner to counterbalance moderate levels of thermal insulation in the building shell with the use of renewable energies (Figure 9.16). In photovoltaics, the maximum amount of solar electricity that qualifies as deductible is the amount for which a concurrently occurring building services electricity demand exists. The monthly PV yield must be set against the monthly building services electricity needs. In residential buildings, only the electricity requirements for space and water-heating are considered relevant. For boilers, only the auxiliary energy (i.e. the electricity for the heating pumps) counts, so that the qualifying PV yield is limited. The electricity requirements of heat pumps, on the other hand, are included, so that here a PV installation can significantly lower the primary energy demand. In non-residential buildings, the scope of relevant energies is expanded to include those required for lighting and air conditioning, which raises the deduction potential of solar electricity. Electricity used for household appliances, office machines or production facilities, however, is considered fundamentally irrelevant to the building proper, even it is self-consumed solar electricity.

In the currently emerging plus-energy standards, such as that of the Effizienzhaus Plus defined by the construction ministry, the scope of qualifying energies used in the balancing process will have to broaden to include household consumption. The active- plus building standard, currently in development, goes beyond this to incorporate the issues of energy management and electric mobility as well. At the same time, the active- plus approach casts its net to encompass life cycle, user wellbeing and architectural quality. This includes an informative assessment of whether solar technology has been well integrated into the architecture in a manner that allows for it to be upgraded over time. According to the Renewable Energy Heat Act (EEWärmeG), new constructions are obliged to cover their heat energy demands in part with renewable energies, or alternatively, to to implement additional energysaving measures. In the case of solar thermal energy, the minimum coverage is set at 15 %, which is usually already achievable with installations used for water heating. This coverage threshold is considered to have been reached in residential buildings if the collector area measures at least 0.04 m2 for every m2 of floor space as defined by the EnEV. In larger apartment buildings with more than two residential units, 0.03 square metres of collector per square metre floor area is adequate. Other options for proving that the building meets the 15 % coverage requirement are to compute the solar yield using standard values or to run a simulation calculation. These methods show that collector surfaces that are smaller than the minimum applied across the board are often fully sufficient. Notes [1] IINAS GmbH: Globales Emissions-Modell Integrierter Systeme (GEMIS), Version 4.9. Darmstadt 2014. Solar installation: own extrapolation using GEMIS 4.9 [2] Bayerisches Landesamt für Umwelt: Berechnung von Immissionen beim Brand einer Photovoltaik-Anlage aus Cadmiumtellurid-Modulen. Augsburg 2011 [3] Hahne, Axel; Hirn, Gerhard: Recycling von Photovoltaik-Modulen. BINE Projekt-Info 02/10. Eggenstein-Leopoldshafen 2010

103

Built examples

Roland Krippner

Building-integrated solar technology in detail The examples on the following pages illustrate exemplary integrations of solar technology installations into buildings. The selection includes solar thermal collector roofs and facades as well as photovoltaic arrays in the building envelope. A few buildings even feature combinations of different solar technologies (thermal and photovoltaic) and integration styles, as the matrix on the right shows. The invisibly located PV arrays on the flat roofs of two of the buildings are not considered. Of the range of building types presented, one third are residential (single-family and apartment buildings), while the remaining two thirds are not. While office and educational buildings, a research institute, a museum and a convention centre dominate the latter category, all projects underline the fact that photovoltaics and solar thermal systems can manifest design-defining effects, even in special building types. The bulk of the buildings are new constructions, but the two examples from Darmstadt and Romanshorn illustrate strategies for the refurbishment and extension of post-war buildings and historically significant building ensembles. The question of structural integration presents a differentiated picture. In a third of the examples, architects opt for “additive” solutions in which the photovoltaic array is visibly separated from the roof or facade surface. Half of the examples feature implementations of structurally and technologically ambitious concepts ranging from passive houses to zero and plus-energy houses to buildings that are fully self-sufficient. The first solutions showcased in this chapter are solar thermal flat plate collectors (or solar absorbers, in the case of the single-family home in Glattfelden) integrated into (single-slope) roofs. Though in one case the solar 104

installations are laid out on a single south-facing surface (Glattfelden), covering the entirety of an east-west oriented gable roof (as in the office and residential building in Darmstadt) is also possible. In the kindergarten in Deutsch-Wagram, in contrast, the collectors are integrated into the skylight area, while the PV modules are incorporated into a glazed canopy. The next set of projects feature photovoltaic roofs. In each of the office buildings, standard modules were employed – monocrystalline modules with aluminium frames in Kasel and frameless thin film glass shingles in Kemptthal. In the museum in Herne, the PV generator is mounted separately from the roof covering, making it possible for the array to be somewhat larger than the roof surface beneath. The treatment of solar facades begins with presentations of an integrative solution using flat plate collectors (apartment building in Bennau) and two cold facades with rear-ventilated photovoltaic modules. While the residential and commercial building in Romanshorn illustrates how facade design can be attractively achieved through the use of standard modules, the architects of the daycare centre in Marburg opted instead for custom-made modules. The common feature among the final three projects is photovoltaics that are employed in various combinations with glass facades. The education centre in Niesetal boasts a warm facade with PV modules in the double-glazing, while the PV array in the convention centre in Lausanne is mounted in front of the building’s glazed southwest facade. The Centre for Photovoltaics in Berlin-Adlershof features a sun-shading solution with fixed horizontal, slanted PV louvres that were mounted into a separate steel structure.

Single-family house, Glattfelden (2013) Mirlo Urbano Architekten, Zurich Office and residential building, Darmstadt (2007) opus Architekten BDA, Darmstadt Office building, Kemptthal (2007) kämpfen für architektur, Zurich Office building, Kasel (2009) Architekten Stein Hemmes Wirtz, Kasel Museum of Archaeology, Herne (2003) v. Busse Klapp Brüning Architekten, Essen Apartment building, Bennau (2009) Grab Architekten, Altendorf Daycare centre, Marburg (2014) opus Architekten BDA, Darmstadt Residential and commercial building, Romanshorn (2012) Viridén + Partner, Zurich Education centre, Niestetal (2010) HHS Planer + Architekten, Kassel Convention centre, Lausanne (2014) Richter Dahl Rocha & Associés, Lausanne Centre for Photovoltaics, Berlin (2009) HENN, Berlin

page Kindergarten, Deutsch-Wagram (2009) Architekturbüro Reinberg, Vienna

Building-integrated solar technology in detail

106 108 110 112 114 116 118 120 122 124 126 128

Building shell

Roof

Facade

Building type

Residential building

• Single-family house

• Apartment building

Office /administrative building

Educational building

Research institute

Cultural building

Event venue

New construction / refurbishment

New building

Existing building

Solar technology

Solar thermal energy

• Solar absorber

• Flate plate collector

Photovoltaics

• Standard module

• Custom-made module

Type of construction

Additive

Integrated

Sunshading

Energy standard

Low-energy building

Passive building

Zero-energy building

Plus-energy building

Energy self-sufficient building

105

Built examples

Kindergarten Deutsch-Wagram, A 2009 Building client: Community of Deutsch-Wagram Architect: Architekturbüro Reinberg, Vienna

The main entrance and all the secondary rooms of this single-storey kindergarten lie on the north side of the building, which is positioned at the northern edge of the property. A hallway illuminated by a row of skylights provides access to the classrooms along the south facade. These have large windows that look out onto the garden. The walls and ceilings of the new construction consist of cross-laminated timber panels. In the room interiors the wall surfaces are plastered with clay, and acoustic elements filled with sheep’s wool and

placed on the undersides of the common room and hallway ceilings provide sound damping. The outer walls are insulated with rock wool and clad in horizontal larch boards. A filigree awning of slightly slanted PV modules, supported by steel pillars, serves as shading for the south facade. The flat roof is extensively planted and covered in zinc sheeting. Alternating with narrow glass panes, four collector fields are arranged on the approximately 30° incline of the skillion roof surface. The solar collectors are mounted a

aa

a

106

directly onto the substructure. Together with the metal roof they form the water-bearing layer. The fields are dimensioned to correspond with the standing seam and consist of collectors of two different sizes. They maintain gaps at the roof edges and at the vertical bands of windows so that the collectors appear to form a thin layer on top of the roof surface. In this kindergarten, active solar technology has been incorporated into an ambitious overall energy concept in a stylistically and structurally exemplary fashion.

Kindergarten in Deutsch-Wagram

1 2

3

2

3

4

5

Site plan, scale 1:3,000 Cross section · Ground floor plan scale 1:500 Vertical section of roof / facade scale 1:20 1 titanium zinc sheet ridge cap 2 recess for cabling 3 thermal solar collector 4 sheet metal roof construction: titanium zinc sheet 25 mm OSB panel 50 mm battens /rear ventilation vapour permeable underlay 25 mm MDF panel 2≈ 200 mm rock wool insulation 120 mm cross-laminated timber vapour barrier 15 mm plasterboard panel 5 snow guard tube 6 wall construction: titanium zinc sheet 10 mm double-layer seal 25 mm OSB panel 120 mm timber frame construction /rock wool insulation 200 mm rock wool insulation

6 7

Solar installation technical data Type of integration

9

7

8 9

vapour barrier 100 mm cross-laminated timber panel 15 mm plasterboard panel flat roof construction: plant substrate, including 100 mm drainage layer filter fleece 5 mm root barrier membrane and separation layer 10 mm welded doublelayer seal 400 mm tapered EPS insulation vapour barrier 200 mm cross-laminated timber panel 15 mm plasterboard panel timber-framed triple glazing lateral titanium zinc sheet verge cover

8

4

integrated into pitched roof, rear-ventilated

Supporting structure Timber battens Installed power

13.66 kWp (PV)

Installation size

30 m2 + 2,700 l tank (ST) 106 m2 (PV)

Exposure

South, 30° (ST), south, 15° (PV)

Anticipated energy yield

7,750 kWh/year (ST) 16,390 kWh/year (PV)

Modules

Sonnenkraft IDMK12-AL / Sonnenkraft IDMK50-AL (ST) ertex solar, polycrystalline (PV)

Number

12 (ST), 34 (PV)

Dimensions

122.7 ≈ 101.5 cm / 245.2 ≈ 205.8 cm (ST)

107

Built examples

Single-family house Glattfelden, CH 2013 Building client: private Architect: Mirlo Urbano Architekten, Zurich Building services and building physics: Raumanzug, Zurich

The desire at the outset of the design process for this single-family house in Glattfelden was to have its energy needs met through renewable and local sources. While PV modules deliver the electricity for the house, solar absorbers and a wood-fired tiled stove cover the heat demands for hot water and space heating. A central distribution system regulates all the heat-generating components. The clearly partitioned timber facade and the gently kinked energy roof lend this new building a self-confident air. Its roof references the saddle roofs of the local area with their structurally required sprockets and utilises the different slants for an optimal orientation of the solar technology. The southeast-facing pitched roof features a solution that has been realised here for the first time: crystalline glass-glass photovoltaic modules, stainless steel solar absorbers with a selective coating and frameless skylights, all incorporated into a roof-integrated PV mounting system. The individual building components are matched in format and colour to ensure a uniform appearance. The heights of the solar thermal systems and the glass panels are coordinated as well, and their scale-like overlapping arrangement lends the surface an additional lightly structured effect. In this way, the architects achieve an elegant combination of solar thermal and photovoltaic installations with the two integrated skylights.

108

Single-family house in Glattfelden

5

2

7

1

3

4

5

6

Site plan, scale 1:2,000 Cross section · Plan of rooftop solar installations, scale 1:200 Vertical sections of roof / facade scale 1:20 1 sheet metal roof construction: 0.5 mm stainless steel roofing plain bearings 5 mm polyester batting (sound insulation) 27 mm tongue and groove timber formwork 40/60 mm battens / rear ventilation vapour-permeable underlay 22 mm diagonal formwork 60/260 mm construction timber 260 mm mineral wool insulation 27 mm three-ply panel

2 3

4

5 6 7

stainless steel sheet ridge cap stainless steel solar absorber, selective coating, black chrome solar roof construction: thermal solar collector / monocrystalline photovoltaic module 40/60 mm system battening / rear ventilation vapour-permeable underlay 22 mm diagonal formwork 60/260 mm construction timber 260 mm mineral wool insulation 27 mm three-ply panel skylight: stepped-edge triple glazing snow guard stainless steel sheet edge channel

Solar installation technical data Type of integration

integrated into pitched roof, including skylights

Supporting structure

PV modules, unglazed thermal solar collectors and skylights, all installed on SOLRIF in-roof mounting system

Installed power

7.6 kWp (PV), 14.6 m2 (ST)

Installation size

14.6 m2 (ST)

Exposure

Southeast

Anticipated energy yield

8,000 kWh/yr (PV) Solar thermal coverage: 70 % of domestic hot water and 10 % of space heating needs

Modules

SunPower (PV), with SOLRIF XL frame; Energie Solaire stainless steel solar absorber AS with SOLRIF frame

Number

33 (PV)

109

Built examples

Office and residential building Darmstadt, D 2007 Building client: Anke Mensing, Darmstadt Architect: opus Architekten, Darmstadt Energy concept: inPlan, Pfungstadt PV designer: opus Architekten, Darmstadt BUSO, Berlin

Construction work done on existing buildings places increased demands on the integration of solar technologies, especially in the cases where concerns about visual continuity or historic preservation are an issue. This office and residential building in Darmstadt represents an exemplary approach to the problem by occupying a gap between the late 19th century buildings on the block perimeter with a glazed new construction featuring office spaces and a stairwell. The neighbouring building was raised from its original two-storey height, and its facade, apart from the glass band under the eaves, was matched to the existing building row. The east-west orientation of the building allows for the full-surface use of solar technology on both halves of the saddle roof. The street-facing east side is fitted out in equal parts with PV modules and solar collectors for water heating and space heating support. The western half is used entirely as a PV generator. The architects took a very exacting and meticulous approach to incorporating the solar technology. The collectors and the PV modules are colour-matched to the surrounding roof surfaces and appear as a separate functional layer owing to the detailed design of the roof edges. In the treatment of the ridge and eaves, the designers took into account the differing structural demands of solar thermal and photovoltaic panels. To ensure proper rearventilation of the photovoltaics, the eaves overhang was clad in canted perforated sheet and the ridge fitted with a ridge vent. 110

Site plan scale 1:1,500 Attic floor plan scale 1:250 Cross section scale 1:250

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Office and residential building in Darmstadt

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3 Vertical sections of roof /facade, scale 1:20 1 100 mm solar roof, rear-ventilated photovoltaics, insulated solar thermal panels 60/60 mm battens waterproofing 22 mm OSB panel 240/80 mm timber purlin on 4 notched HEB 140 steel frames insulation 240 mm mineral wool vapour barrier 40/60 mm counter battens alternating with 60 mm mineral wool insulation 2≈ 12.5 mm smoothed plasterboard panel

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70 mm solid timber sprocket HEB 140 steel profile triple glazing with aluminium frame 25 mm exterior plaster 200 mm mineral wool insulation 175 mm brick masonry 15 mm interior plaster floor construction: 22 mm oak strip parquet 35 mm screed separating layer 10 mm footfall sound insulation 200 mm hollow brick ceiling inlaid in HEB 140 steel frame 15 mm interior plaster

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Solar installation technical data Type of integration

Roof-integrated, rear-ventilated (PV) Insulated (ST)

Installed power

8.64 kWp (PV) 5 kWth (ST)

Installation size

72 m2 (PV) 24 m2 (ST)

Exposure

East-west, 32.5°

Anticipated energy yield

7,500 kWh/yr (PV) 5,000 kWh/yr (ST)

Modules

Solea (monocrystalline), custom-made frameless glass-film-modules

Number

72

Dimensions

100 ≈ 100 cm

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Built examples

Office building Kemptthal, CH 2007 Building client: Marché Restaurants Schweiz, Kemptthal Architect: kämpfen für architektur, Zurich Energy planner: Naef Energietechnik, Zurich Photovoltaics: Beat Kämpfen, René Naef (Design) SunTechnics Fabrisolar (Implementation) The Marché International Support Office is the first office building in Switzerland with a zero energy balance. Its compact, unpretentious volume was designed according to the principles of passive solar architecture. A distinctive mixture of customary timber construction, innovative PCM technology and photovoltaics characterises both support structure and building shell. Insulation thicknesses based on passive house standards minimise the heat losses of the building, whose structural framework is built entirely (with the exception of the two concrete stairwells) of pre-fabricated solid wood panels. Half of the predominantly glazed south facade is comprised of multi-layered special glass, which functions as translucent insulation, protection against overheating and, thanks to an incorporated phase change material (PCM) of salt hydrate, thermal storage. The facade construction provides a thermally and visually pleasing interior and offers excellent workplace ambience. The entire surface of the skillion roof is dedicated to electricity generation and delivers 100 % of the required electrical energy. The installed array consists of anthracite-coloured, standard glass-glass thin film modules. The architects succeed in creating an unobtrusive but exceedingly elegant detailing of the roof and its edges. The small-structured scalelike overlaps in the modules result in a well-balanced, aesthetically convincing structured roof surface that sets a new standard. 112

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Office building in Kemptthal

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5 Site plan, scale 1:2,500 Cross section · Ground floor plan scale 1:400 Vertical section of roof / facade scale 1:20 1 thin film photovoltaic modules 2 wall construction: 25/90 mm Douglas fir formwork 30 mm rear ventilation / battens black underlay 15 mm HDF panel 80/40 mm battens alternating with 80 mm glass wool insulation 225 mm ribs alternating with 225 mm glass wool insulation

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2 ≈ 35 mm triple-ply panel floor construction: underlay 280 mm cellulose insulation 30 mm triple-ply panel 160/40 mm ribs alternating with 160 mm glass wool insulation 30 mm triple-ply panel vertical awning Triple glazing in timber frame, Ug = 0.5 W/m2K 40/120 mm larch handrails on 80/40/8 mm steel L profile 40/40 mm larch grate on 240/80 mm squared timber

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Solar installation technical data Type of integration

Integrated into skillion roof, rear-ventilated

Supporting structure

Timber battens and counter battens

Installed power

44.6 kWp

Installation size

485 m2

Exposure

South, 12°

Anticipated energy yield

40,000 kWh/yr

Modules

First Solar frameless thin film glass-glass module

Number

649

Dimensions

120 ≈ 60 cm

113

Built examples

Office building Kasel, D 2009 Building client: private Architect: Architekten Stein Hemmes Wirtz, Kasel and Frankfurt /Main Energy planner: Architekten Stein Hemmes Wirtz, Kasel and Frankfurt /Main Anlagenbau Brisch, Waldrach

The “Plus-Energy House” in Kasel near Trier is being used by its own architects as an office building, though it can be converted as needed into an apartment house. The two-storey building has a saddle roof and a gable front and conforms to the passive house standard. Its energy concept is supported by the generation of solar electricity. In their use of oak and slate in both the interior and exterior, the architects have relied on regional materials. The primary construction is a solid timber building with 30 to 36-centimetre thick cellulose insulation. In addition to the solid wood panels, a slate wall inside the structure functions as a thermal storage mass. The large, mostly fixed-pane windows consist of frameless triple glazing; on the southeast side of the building they are rotated out of the plane of the facade like bay windows. The northwest-facing side of the roof is clad in small-scale copper elements, while the southeast half is completely covered with a PV array. Forty vertical-aspect rectangular, framed standard modules with efficiencies of over 18 % produce 8,500 kilowatt-hours of electricity a year. The rear-ventilated installation is mounted above the water-bearing layer and terminates flush with the roof edges. This results in an understated roof appearance with a harmonious incorporation of the photovoltaics, which also allows for size adaptations. Conceptually as well as structurally, the building exemplifies a successful merging of modern regional architecture with contemporary solar technology. 114

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Office building in Kasel

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Site plan, scale 1:2,500 Cross section · Upper floor plan scale 1:200 Vertical sections of roof / facade scale 1:20 1 roof construction: copper shingle roof covering 22 mm formwork 220 mm rafters roof membrane 22 mm OSB panel 360 mm timber I-beam / cellulose insulation 22 mm OSB panel rafters 2 monocrystalline PV module with steel support structure 3 window element: copper cover profile 20 mm plywood 40 mm vacuum insulation 20 mm plywood 4 triple glazing 5 wall construction: 20 mm oak wood panel 140 mm rear ventilation water-proofing 35 mm vapour-permeable, waterproof fibreboard 300 mm timber I-beam / cellulose insulation 85 mm cross-laminated timber

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Solar installation technical data Type of integration

mounted onto pitched roof, rear-ventilated

Supporting structure

Support structure of steel profiles to maintain separation from water-bearing layer

Installed power

9 kWp

Installation size

50 m2

Exposure

Southeast, 45°

Anticipated energy yield

8,500 kWh/yr

Modules

Conergy SPR1151155 WHT-I (monocrystalline)

Number

40

Dimensions

158 ≈ 79 cm

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Built examples

Museum of Archaeology Herne, D 2003 Museum building client: Westfalen-Lippe Regional Council, Münster PV array building client: Herne Public Utilities Architect: v. Busse Klapp Brüning Architekten, Essen

The new museum construction in Herne connects the neo-Gothic Kreuzkirche and the neighbouring culture centre to form a green “culture garden”. The entrance is located at street level, while the lower-lying central exhibit spaces in the basement are arranged around sunken inner courtyards. Two big orthogonal halls, boasting twice the ceiling height to accommodate large objects and special exhibitions, project one storey above the terrain. A towering saw-tooth roof construction provides for predominantly natural lighting. Each saw-tooth portion is glazed on three sides. The fourth surface, facing either south-west or south-east and inclined at 30°, has a photovoltaic array installed above the metal roof covering. The polycrystalline modules are mounted in vertical aspect and project beyond the roof edges by about half an element’s width at verge and ridge. A total of 330 frameless glass-glass modules, 4 ≈ 0.94 metres in size and delivering a combined peak power of 100 kilowatts, were installed in triple-row arrangements. The light, canopy-like construction elegantly separates the photovoltaics from the roof covering, ensuring an effective rear-ventilation of the modules and reducing the influx of heat into the exhibition spaces. From the material standpoint also, the shimmering blue PV modules contrast attractively with the reddishbrown colour of the sculpturally structured brick facades, as well as with the grey metal surfaces and the often extensively glazed building openings. 116

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Museum of Archaeology in Herne

Site plan, scale 1:2,000 Longitudinal section · Basement level floor plan, scale 1:1,000 Vertical section of roof, scale 1:20 1 20 mm frameless glass-glass photovoltaic module 140 mm insulated sandwich panel IPE steel profile in the bay 180/90/10 mm steel L profiles as edge beams 2 point mounting for photovoltaic modules 3 insulation glazing in post-andbeam facade 4 HEA 200 steel profile 5 internal dimming system, aluminium venetian blinds 6 grate 7 indirect luminaire

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Solar installation technical data Type of integration

Roof-mounted, surface extended

Supporting structure

Supporting structure of steel profiles

Installed power

100 kWp

Installation size

1,119 m2

Exposure

South 32°, west 32°

Anticipated energy yield

60,000 kWh/yr

Modules

Frameless glass-glass modules, bifacial cells

Number

330

Dimensions

400 ≈ 94 cm

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Built examples

Apartment building Bennau, CH 2009 Building client: Sanjo Immobilien, Altendorf Architect: Grab Architekten, Altendorf Energy concept and heating, ventilation and sanitation design: Amena, Winterthur

The apartment building “Kraftwerk B” in Bennau comprises seven residential units and is one of the first constructions to meet the Swiss MinergieP-Eco building standards. In addition to sustainability and the lowest possible energy usage, living quality and maximum flexibility in the use and possible conversion of the building were central aspects of the design. The primary structure of the compact building volume consists of a loadbearing reinforced concrete core and a building envelope of prefabricated, highly insulated timber elements. The southwest-facing roof and facade surfaces are almost exclusively dedicated to the utilisation of solar energy. The entire area of the pitched roof, as well as that of the skillion roof of a neighbouring building on the street, is covered with a homogeneous PV array. The frameless, wide-aspect thin film modules overlap slightly like scales and are mounted on a timber support structure. The southwest facade features a clear, horizontally partitioned grid pattern in which full-height openings and solar thermal flat plate collectors alternate. Two thirds of the generated heat is used for floor heating and hot water production, while the remaining third is delivered to a neighbouring building. The apartment building in Bennau exemplifies the large-scale integration of solar technology, especially in its collector facade. The distinct grid pattern, varied subtly by a slight offset between storeys, results in an aesthetically and functionally harmonious solution. 118

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Apartment building in Bennau

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Site plan, scale 1:1,000 Cross section · Ground floor plan scale 1:400 Vertical section of roof / facade scale 1:20 1 60 mm Ø collector distribution pipe 2 60 kg/m3 rock wool insulation 3 wall construction: 6 mm prismatic ESG cover 42 mm absorber /air layer 60 mm rock wool insulation 8 mm OSB panel backing 15 mm gypsum fibreboard kraft paper wind proofing 40/360 mm timber ribs alternating with 360 mm cellulose insulation 15 mm OSB panel vapour barrier 60 mm battens / insulation (plane of installation) 15 mm gypsum fibreboard 10 mm clay plaster 4 100/45 mm framing timber 5 triple-glazing in a timber frame, Ug = 0.5 W/m2K 6 floor construction: 15 mm oak floor boards 85 mm heating screed separating layer 20 mm footfall sound insulation 20 mm insulation 200 mm reinforced concrete

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Solar installation technical data Type of integration

Facade: integrated, no rear-ventilation (ST); roof: integrated (PV)

Supporting structure

Battens, counter battens, timber (roof); Framing timber with cover trim (facade)

Installed power

23 kWp (PV)

Installation size

146 m2 (ST) 220 m2 + 41 m2 on neighbouring building (PV)

Exposure

Southwest 90° (ST) Southwest 42.7° (PV)

Anticipated energy yield

30,000 kWhth /yr (ST) 32,000 kWh/yr (PV)

Number

20 on facade 198 on roof 45 on neighbouring building

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Built examples

Daycare centre Marburg, D 2014 Building client: City of Marburg Architect: opus Architekten, Darmstadt Energy concept: ee concept, Darmstadt

The City of Marburg has constructed a day care centre on the Vitosareal, located in the south of the city. The centre’s location in the park, its connection to the historic buildings in the vicinity and the gentle eastward rise of the local topography were all important design parameters. Furthermore, the building was to be the first day care centre in Germany to meet the “Efficiency House Plus” energy standard. The result is a building that is distinctive on the outside as well as in its interior design. While the ground floor

is built in the massive construction style, the upper storey and roof are light timber frame constructions. Both the roof and the facade of the “folded” building are optimised with regard to natural lighting and to activation of the exterior surfaces. The active solar surfaces face southward, while the glazing on the northern side is primarily designed to admit daylight. Six bands of photovoltaic modules, oriented to the south with an inclination of 17°, determine the characteristic sawtooth-like roof construc-

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tion. This structure continues vertically on the southwest facade, whose opaque surfaces are likewise fully utilised for generating electricity. The wide-aspect, rearventilated glass-glass modules are arranged in a taut grid pattern. The monocrystalline cells and dyed metallic brazing tapes cause the inner structure to recede in favour of a homogeneous surface effect, and the resulting impression from a distance is one of a perfectly detailed, part black and part transparent glass facade.

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Daycare centre in Marburg

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Site plan, scale 1:2,000 Cross section · Upper level floor plan scale 1:400 Vertical section of roof / facade scale 1:20 Horizontal section of facade scale 1:20 1 solar roof construction: black monocrystalline photovoltaic modules (VSG) 80/80 mm battens plastic sheet seal 21 mm formwork 360 mm spars /cellulose insulation vapour barrier 18 mm OSB panel 28/60 mm timber frame covered with acoustic felt fleece padding 35/20 mm pine battens

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plastic sheet seal wall construction: black monocrystalline photovoltaic modules (VSG) vertical and horizontal aluminium support structure plastic sheet seal (PE) 15 mm OSB panel 320 mm timber studs / mineral fibre insulation vapour barrier 18 mm OSB panel 38 mm block plywood fleece padding 35/20 mm pine battens ventilation flaps for night-time cooling aluminium louvres

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Solar installation technical data Type of integration

Roof and facade, integrated

Supporting structure

Aluminium / timber supporting structure

Installed power

52.32 kWp

Installation size

304 m2 (Roof) 81 m2 (Facade)

Exposure

South (roof) Southwest (facade)

Anticipated energy yield

38,500 kWh/yr

Modules

ertex solar (monocrystalline)

Number

354

121

Built examples

Residential and commercial building Romanshorn, CH 2012 Building client: EcoRenova, Zurich Architect and energy planner: Viridén + Partner, Zurich Photovoltaics: Hollinger Solar, Bubendorf

This 1960s residential and commercial building not only underwent a comprehensive refurbishment, but was also expanded to accommodate additional flats. Thanks to greater compactness, good insulation and a new air-water heat pump heating system, the energy requirements of the building dropped by 70 % despite the significant increase in floor space. The large-scale employment of photovoltaics in the building shell turns the building into a plus-energy house with a computed energy surplus of 7 %. Installed on the flat roof are a photovoltaic array with a peak power of 26.3 kilowatts and 69 square metres of solar thermal collectors. Rear-ventilated, suspended constructions in front of the south and west-facing facades incorporate 53 kilowatt peak power monocrystalline PV modules. The facade is characterised by a uniform grid of wide-aspect rectangular elements, which run continuously along the parapet level and whose height is coordinated with that of the bands of windows. The modules, whose polygonal cells lend the exterior a fine-structured appearance, are of the readily available standard variety and fully cover all wall and balcony parapet surfaces. In order to match the dimensional tolerances of the building shell and its window openings, the balconies were equipped with a type of moulding of light metal facing, into which sun shading is integrated at the lintels. The building in Romanshorn beautifully exemplifies how even complex existing facades can be complemented with active solar technology to create a coherent overall concept. 122

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Residential and commercial building in Romanshorn

Cross section · Upper level floor plan, scale 1:400 Vertical and horizontal sections of facade, scale 1:20 1 terrace floor construction: 40 mm cement stone panels 110 mm slab supports two-ply polymer bitumen membrane seal EPS insulation 40 –100 mm 1.5 % gradient 140 mm PUR insulation vapour barrier 180 mm reinforced steel ceiling suspended ceiling 15 mm plasterboard 2 PV fixing clamp 3 7/350 mm facade anchor for steel profile system mount 4 new building wall construction: 35 mm monocrystalline photovoltaic modules 45 mm rear ventilation house wrap waterproofing 280 mm mineral wool insulation

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150 mm masonry 10 mm interior plaster stove-enamelled aluminium frame venetian blind floor construction: 10 mm parquet 45 mm anhydrite screed separation layer footfall sound insulation 25 mm mineral fibre 20 mm polystyrol insulation 180 mm reinforced concrete ceiling suspended ceiling 15 mm plasterboard existing building wall construction: stove-enamelled aluminium sheet 50 mm rear-ventilation sealing sheet 280 mm mineral wool insulation 280 mm reinforced concrete outer wall 50 mm cork insulation 10 mm interior plaster

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Solar installation technical data Type of integration

PV facade, integrated, cold facade; PV + ST: rooftop

Supporting structure

Facade: PV rails on 350 mm RSD7 system mounting

Installed power

53 kWp (PV, facade), 26 kWp (PV, rooftop)

Installation size

295 m2 (PV, facade), 110 m2 (PV, rooftop), 69 m2 (ST, rooftop)

Exposure

South and west

Anticipated energy yield

48,000 kWh/yr (PV) 35,000 kWhth/yr (ST)

Modules

Sanyo HIT-H245E01, HIT- H250E01

Dimensions

161 ≈ 86 cm

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Built examples

Education centre Niestetal, D 2010 Building client: SMA Solar Technology, Niestetal Architect: HHS Planer + Architekten, Kassel Energy planner: energydesign braunschweig

The seminar and education centre in Niesetal is one of the first energy self-sufficient non-residential buildings in Germany. Since the property lies in the flood plain of the nearby Fulda River, the building rests on several distinctive, slightly canted pillars. White aluminium alloy panels and an extensive glass facade characterise the building shell. Photovoltaic elements are integrated into the gently sloped south facade, whose polygonal contour follows the path of the sun. The semi-transparent, monocrystalline glass-glass modules incorporated into the postand-beam construction reduce the heat influx into the access hallways and simultaneously cast the interior in an agreeable half-light. The surface density of the cells varies depending on sightlines and shading requirements. Overall, the facade array, which functions as a widely visible design element, achieves a peak power output of 31.7 kilowatts. The roof features an installation of standard monocrystalline PV modules with a total peak power of 58.7 kilowatts. A building-wide automation system optimises the energy consumption of the building in real time. A battery buffers any consumption peaks that may occur. The “Solar Academy” is designed to accommodate approximately 600 events a year. It serves as a model for energy efficiency and solar technology in educational buildings, and beyond this represents a flagship project for electricity supply that is independent of the municipal grid.

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Education centre in Niestetal

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7 Site plan, scale 1:5,000 Cross section · View from the south · upper level floor plan scale 1:750 Vertical section of roof / facade scale 1:20 1 accessible grate 2 roof construction: 65 mm monocrystalline photovoltaic modules 340 mm rear ventilation waterproofing 250 mm mineral wool insulation vapour barrier 200 mm reinforced concrete ceiling plasterboard suspended ceiling with acoustic insulation plaster

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galvanised IPE 120 steel profile construction foil calcium silicate plaster base panel on 50/550/1 metal angle monocrystalline glass-glass photovoltaic modules in post-and-beam construction foyer floor construction: 22 mm parquet 79 mm screed with floor heating separating layer 45 mm insulation 370 mm reinforced concrete ceiling 220 mm mineral wool insulation fleece 125 mm aluminium support structure/rear ventilation 3 mm aluminium alloy panel

Solar installation technical data Type of integration

South facade with roof glazing in post-andbeam construction and pressure plates, warm facade (glass facade), additive rearventilated rooftop array

Supporting structure

Reinforced concrete

Installed power

31.7 kWp (facade), 58.7 kWp (roof)

Installation size

310 m2 (facade)

Exposure

Southeast and southwest

Anticipated energy yield

8,500 kWh/yr

Modules

Schüco (monocrystalline)

Number

154 (facade), 162 (Roof)

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Built examples

Convention centre Lausanne, CH 2014 Building client: École Polytechnique Fédérale de Lausanne (EPFL) Architect: Richter Dahl Rocha & Associés, Lausanne Photovoltaics: Richter Dahl Rocha & Associés with Catherine Bolle (design) Solaronix, Aubonne (implementation)

The newly built SwissTech Convention Centre is part of an expansion of the EPFL campus. The building features a roof with crystallike planes, covered with aluminium shingles and projecting up to 40 metres beyond the building face. The interior encompasses an open foyer with building-height glass facades, seminar rooms and a multi-functional conference hall for up to 3,000 people. While large-scale glass facades often appear as monotonous, smoothly reflective surfaces, the architects in this case opted for a different approach: the west facade of the building boasts the largest solar array of dye-sensitised solar cells to date. The cells, also known as “Grätzel cells”, were developed in the early 1990s and patented in 1992 by the chemist and EPFL professor Michael Grätzel. A total of 300 square metres of glass-glass modules, with solar cells in yellow, green and red hues, are installed on the outside of the glass facade. The full-height glass louvres consist of individual aluminium-framed panels, each of which encompasses four 50 ≈ 35 centimetre cells. The louvres are affixed at slightly varying angles and at varying distances from the plane of the facade. The additive PV facade not only functions as a solar shade, but produces appealing lighting effects in the foyer. In combination with a light facade construction, the cell technology opens up new design possibilities, particularly for glass facades. 126

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Convention centre in Lausanne

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Site plan, scale 1:10,000 Cross section · Ground floor plan scale 1:1,500 Horizontal and vertical sections of facade, scale 1:20 1 steel facade support 2 14 mm insulated glazing + 17 mm SZR + 8 mm insulated glazing, held laterally by pressure plates

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anodised aluminium cover 50/50/5 mm steel tubing glass-glass solar panels framed in anodised aluminium, each 2,100 ≈ 410 mm panel consisting of 4,350 ≈ 500 mm modules with 13 strip-like 2-cm-wide Grätzel cells

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Solar installation technical data Type of integration

Additive facade

Supporting structure

Additional steel construction on post-andbeam facade

Installed power

3 kWp

Installation size

280 m2

Exposure

Southwest

Anticipated energy yield

2,000 kWh/yr

Modules

Solaronix electrochemical thin film (Grätzel dye) solar cells, Glass-glass modules framed in aluminium

Number

1400

Dimensions

35 ≈ 50 cm

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Built examples

Centre for Photovoltaics Berlin, D 2009 Building client: WISTA-Management, Berlin Architect: HENN, Berlin

The new 8,000-square-metre Centre for Photovoltaics and Renewable Energies in Berlin-Adlershof offers emerging enterprises the opportunity to rent production, laboratory and office spaces in a variety of different configurations. Located adjacent to the ground floor foyer are workshops and partitionable production halls as well as a canteen. The upper storeys house physics and chemistry laboratories in addition to offices and conference rooms. Functioning as a central element, the building-high atrium features sightlines to all levels and a sculptural winding staircase with a solid balustrade, which links the individual storeys to one another. The flat roof is equipped with surfaces for photovoltaic experiments that can also be rented by firms. Arranged in the overhead area of the extensively glazed entry facade are horizontal photovoltaic louvres, whose installation required an Individual Approval (ZiE: Zustimmung im Einzelfall). Each of the approximately 1.90 ≈ 0.70 metre unframed monocrystalline glass-glass modules is fastened to a horizontal steel tube with edge clamp mountings and three metal braces. In addition to electricity generation and partial shading of the foyer, the photovoltaic array also has a symbolic function. It is a visual representation to the public, as well as to the employees of the facility itself, of the research activities that occur within its walls.

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Centre for Photovoltaics in Berlin

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10 Site plan, scale 1:10,000 Longitudinal section, scale 1:1,000 Ground floor plan scale 1:1,000 vertical section, scale 1:20 1 precast concrete element facade cladding 2 200 mm long M16 stainless steel pressure screw 3 facade panel anchor 4150/150/6.3 mm steel tubing (incl. top and base plate) 5 HEA 140 steel girder, connection to main girder via top plates 6 HEA 260 steel girder with rigid connection to facade supports 7 sharp-edged hollow steel profile ¡ 300/100 mm consisting of 300/30 mm and

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100/15 mm flat steel sheets HEA 240 steel girder 40 mm sheet steel sandwich panel 2≈ 140 mm insulation 8 mm + 6 mm double glazing with aluminium frame, motordriven ventilation flaps aluminium post-and-beam facade with inserted steel tubing 12 mm + 8 mm double glazing photovoltaic module (4 mm TVG + 2 mm EVA foil + 6 mm TVG), 710 ≈ 1,870 mm format, rigidly mounted on steel tubing sharp-edged hollow steel profile ¡ 300/60 mm consisting of 300/30 mm and 60/15 mm flat steel sheets

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Solar installation technical data Type of integration

Facade, additive (stationary sun shading)

Supporting structure

Steel construction

Installed power

23.94 kW

Installation size

186 m2

Exposure

South 50°

Anticipated energy yield

20,488 kWh/yr

Modules

Solarwatt M180-44 GEG LK (Monocrystalline) glass-glass module

Number

140

Dimensions

187 ≈ 71 cm

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Appendix

• • • • • • • •

Acknowledgements Authors Index of illustrations Literature Regulations, guidelines, standards Glossary Subject index Register of companies and individuals

Authors

Acknowledgements The completion of a publication of this type would not have been possible without the participation of a great many people. Firstly, we wish to thank the Bavarian Association for the Promotion of Solar Energy (SeV – Solarenergieförderverein Bayern e. V.) and its executive board members Dr. Bruno Schiebelsberger, Prof. Dr. Gerd Becker and Walter Weber, who took up the topic early on and have followed and expanded it over the ensuing years. Without the financial support of the Bavarian Association for the Promotion of Solar Energy this book could not have been completed. The publication represents a progress report of sorts of the extensive projects of the SeV. The association has sponsored six competitions since the year 2000 and has organised two workshops on building-integrated solar technology: “Photovoltaics – technology and architecture” in 2003 and “Building-integrated photovoltaics (BIPV) – technology and architecture” in 2004. In July of 2009, the travelling exhibition “Building-integrated solar technology – architecture and solar energy” was first shown at the university then known as the Georg-SimonOhm-Hochschule in Nuremberg. Since then (and including its updated and expanded versions of 2012 and 2014) it has been seen in over 80 venues in 10 countries. As an accompaniment to the exhibition, the brochure “Buildingintegrated solar technology – solar energy and architecture: from the competitions of the SeV” was published in 2009. The present book brings these activities together and supplements and deepens them by involving recognised experts on the topic. The publication also represents an amalgamation of many years of effort in the field of building-integrated solar technology for the editor, beginning in February of 1995 with his stint as research associate for Prof. Thomas Herzog, in the Department of Design and Building Construction II at the Technische Universität München, and extending to current teaching and research subjects at the Technische Hochschule Nürnberg. The editor’s collaboration with the Bavarian SeV started with a sponsored

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study project on the “Use of photovoltaics in existing buildings” in 2001 and intensified steadily through his participation in workshops and as a jury member in the “Architecture and solar electricity – building-integrated photovoltaic arrays” competition of 2005. In 2007, the editor became a member of the Bavarian Association for the Promotion of Solar Energy and has been involved in supervising the activities in the field of “building-integrated solar technology” ever since. Christian Schittich, who was editor-in-chief of DETAIL until September of 2016, has been following the competition events of the Bavarian SeV for years. His involvement initiated its successful partnership with the Institut für internationale Architektur-Dokumentation (Institute for International Architecture Documentation). Fabian Flade played a significant part in the success of this project. From the outset he was involved in its conceptual development, using his indefatigable energy and passionate engagement to form the organisational and substantive intersection between the authors and the publishers, and acting always as a constructive and critical comrade-in-arms. The collaboration with the authors developed very constructively, opening a great many new perspectives on the topic. Jakob Schoof and Jana Rackwitz from the DETAIL editorial staff were invaluable driving forces with regard to the structure and contents of the book and are responsible for its graphic design. In a follow-up to a Masters seminar in the summer semester of 2015, a team of Masters students at the Department of Architecture of the Technische Hochschule Nürnberg, Simon Axmann, Annika Ludwig, Fabiola Tchamko und Ka Xu, performed the editing work on the projects section with great enthusiasm. To them all and to their colleagues we herewith extend our heartfelt thanks. Prof. Dr. Roland Krippner, September 2016

Roland Krippner 1960 Born in Frankfurt am Main 1976 –1980 Vocational training as machinist 1982 –1987/1989 –1993 Studied architecture at the Gesamthochschule Kassel 1988/89 Civilian service, Hesse State Office for Historic Preservation, Marburg branch since 1989 Publishing activities 1993 –1995 Employed at Bureau for Architecture and Urban Development (BAS), Kassel since 1995 Freelance work as architect (R&D projects), technical author, lecturer 1995 – 2006 Fesearch associate /assistant, Department of Building Technology, Prof. Dr. (Univ. Rome) Thomas Herzog, TU Munich 2004 Awarded Dr.-Ing. degree at the TU Munich 2005/06 Lectureship at the Fachhochschule Salzburg 2006/07 Research fellow, Department of Industrial Design, Prof. Dipl.-Des. Fritz Frenkler, TU Munich 2006/07 Visiting Professor, Environmentally Conscious Design and Experimental Building, University of Kassel seit 2008 Professor, Construction and Technology, Technische Hochschule Nuremberg Georg Simon Ohm Gerd Becker 1948 Born in Ihringshausen / Kassel 1970 –1975 Studied electrical engineering / energy technology at the Technische Universität Munich 1975 –1980 Research associate in the field of electrical energy supply, Universität der Bundeswehr Neubiberg, awarded doctorate in 1981 1981–1988 Director of load distribution at IsarAmperwerke AG 1988 – 2014 Professor, Electrical Energy Technology and Renewable Energies, Munich University of Applied Sciences. Conducted numerous projects in the field of electrical energy supply and renewable energies since 2014 Freelance consultant and expert for renewable energies and their integration into the grid

Authors

Ralf Haselhuhn 1964 Born in Berlin 1986 –1991 Diploma studies in electrical engineering, Technische Universität Dresden 1992 –1993 Correspondence course, “Energy Consultancy and Management”, Technische Universität Berlin 1991–1995 Engineer for Energy Consultancy and Design since 1995 Designer, expert and consultant at the German branch of the International Solar Energy Society (DGS) in Berlin, specialising in photovoltaics, batteries, renewable energies and energy efficiency 2000 – 2010 Lectureship for photovoltaics, HTW Berlin since 2003 Chairman of the national Technical Committee for Photovoltaics, German Solar Energy Society since 2014 Director of the German Solar Energy Society, Berlin-Brandenburg regional association Participation in expert panels: Committee on DIN-VDE norms pertaining to photovoltaics and batteries, BSW specialist groups, Intersolar Award /ees Award, conference advisory board of the OTTI symposia on “Photovoltaic Solar Energy”, among others Publications: DGS guidelines “Photovoltaic Installations”, book Photovoltaics – Buildings supply electricity, expert articles and conference contributions, expert opinions in the area of legislation and guidelines on photovoltaics, among others Seminar and conference chairman for photovoltaics at Haus der Technik Berlin and at the VDE-Verlag Claudia Hemmerle 1976 Born in Kaufbeuren 1996 – 2000 Studied and received degree in Environmental Technology/ Renewable Energies, FHTW Berlin 2001 – 2007 Project engineer, expert consultant, advisor and author, German Solar Energy Society, Berlin as well as lecturer at the Solarschule Berlin 2005 – 2015 Participation in the Committees on Norms DKE AK 373.0.2 “Building-integrated PV modules” and CENELEC “Photovoltaics in buildings” 2007 – 2013 Research associate, TU Dresden, Institute for Building Construction 2014 – 2015 Research engineer, German Solar Energy Society, Berlin 2015 Awarded doctorate, TU Dresden, Department of Civil Engineering, Dissertation: “Photovoltaik in der Gebäudehülle. Wertung bautechnischer Anforderungen” since 2015 Post-doctoral fellow, TU Munich, Centre for Sustainable Building Beat Kämpfen 1954 Born 1980 Completed architecture studies at ETH Zurich 1982 Awarded Master of Architecture, University of California, Berkeley /USA; majoring in solar architecture and ecology 1984/85 Design associate, ETH Zurich 1985 – 1995 Office partnership Meister und Kämpfen 1995 – 2009 Office Beat Kämpfen – Kämpfen für Architektur, Zurich since 2010 kämpfen für architektur ag, Zurich 2005 – 2016 President of the Forum for Energy, Zurich Committee work for Swissolar, Zurich Multiple prizes for energy-efficient building in Switzerland

Tilmann E. Kuhn 1967 Born in Waiblingen 1996 Physics degree, University of Heidelberg 1996 –1999 Research associate, Projects in Solar Energy, Freiburg 1999 – 2004 Research associate, Fraunhofer Institute for Solar Energy Systems (ISE), Freiburg since 2004 Director of working group for solar facades, Fraunhofer ISE 2016 Awarded doctorate of physics at National and Kapodistrian University of Athens, Dissertation: “Design, Development and Testing of Innovative Solar-Control Facade Systems”

Publications: guidebook “Photovoltaik – Solarstrom vom Dach” for the Stiftung Warentest, expert in radio broadcasting and TV as well as print and online media. Regular contributions to trade journals, active as consultant, e.g. in the training of photovoltaics experts at the TÜV Rheinland Akademie Since August 2016 engaged in “Manager Training” at the photovoltaic manufacturing firm SolarWorld in Bonn

Christoph Maurer 1982 Born in Waiblingen 2003 – 2008 Studied physics and received degree at Eberhard Karls University, Tübingen 2003 – 2005 German studies and intermediate examination at Eberhard Karls University, Tübingen 2008 – 2011 Research associate, Fraunhofer Institute for Solar Energy Systems (ISE) as recipient of a grant from the German Academic Scholarship Foundation 2008 – 2012 Awarded Doktor-Ingenieur degree at Karlsruhe Institute of Technology (KIT) with a major in Building Physics & Technical Development (Prof. Wagner), Dissertation: “Theoretical and experimental analysis and optimization of semi-transparent solar thermal façade collectors” since 2011 Team leader, Solar Thermal Facades, Fraunhofer ISE since 2016 Subtask leader, “Performance characterisation of solar envelope elements” in SHC Task 56 of the International Energy Agency (IEA) Georg W. Reinberg 1950 Born in Vienna 1970 –1978 Architecture studies and degree, TU Wien 1976 –1977 Architecture studies at Syracuse University/USA; Master of Architecture (Fulbright scholarship) 1978 –1986 University associate at the Institute for Architectural Strategies, TU Wien (Prof. Schweighofer) 1983 –1990 Joint venture Reinberg, Treberspurg and Raith since 1984 Own civil engineering firm since 1986 Lectureships at TU Wien and various international universities since 1997 Visiting Professor, Danube University Krems (Solar Building – Future Building Solutions) since 2006 Sole owner and CEO of the architecture firm Reinberg ZT GmbH since 2014 Lecturer for residential construction at the University of Applied Sciences, Vienna (Green Building Solutions) since 1984 More than 800 publications on the subject of solar architecture Thomas Seltmann 1972 Born in Weißenburg, Bavaria Independent photovoltaics expert, lecturer and author (following an education in electrical engineering, business and journalism) Professional experience in design, assembly, installation, marketing and sales of PV installations For over 20 years, involved in research on technical, economic and legal issues related to solar electricity installations

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Appendix

Index of illustrations The authors and publishers would like to extend their sincere thanks to all individuals who have participated in the completion of this book by making their photographs available, by granting permission to reproduce images and by providing pertinent information. Photographs for which no photographer is credited are architects’ pictures or working photos, or are taken from the archives of DETAIL magazine. Despite our best efforts we were unable to identify the owners of some of the illustrations; however, their copyright is ensured. We ask that we be notified of any claims in these cases. The numbers refer to the figure numbers.

Title Convention centre in Lausanne Photo: Richter Dahl Rocha & Associés architectes SA, CH–Lausanne Prologue 0.1 René Schmid Architekten AG, CH – Zurich Introduction and history 1.1 Deppisch Architekten, D – Freising 1.2 FS-Architekten, Paul Schröder Architekt BDA, D – Darmstadt, formerly Funk & Schröder 1.3 Wolfram Janzer, D – Stuttgart 1.4 Verena Herzog-Loibl, D – Munich 1.5 Jochen Helle, D – Dortmund 1.6 Anja Blees, D – Aachen 1.7 Rolf Disch SolarArchitektur, D – Freiburg 1.8 Universitätsbauamt Erlangen 1.9 Gehrlicher Umweltschonende Energiesysteme, D – Haar 1.10 PMP Architekten GmbH, D – Munich 1.11 Jordi Miralles, E – Barcelona 1.12 Manfred Hegger, D – Kassel 1.13 Jens Willebrand, D – Cologne 1.14 Leon Schmidt, D – Darmstadt 1.15 HFT Stuttgart 1.16 Daniele Domenicali, I – Imola 1.17 Glaswerke Arnold GmbH & Co. KG, D – Remshalden 1.18 Croce & Wir, A – Graz 1.19 Bruno Klomfar, A – Vienna 1.20 Nabo Gaß, D – Wiesbaden 1.21 Hufton + Crow, GB – London 1.23 Jakob Schoof, D – Munich Buildings as catalysts for energy transformation 2.1 Planerwerkstatt Hölken – Berghoff, D – Vörstetten 2.2 Zooey Braun, D – Stuttgart 2.3 SolaRoad Netherlands 2.4 Matthias Koslik, D – Berlin 2.5 zillerplus Architekten und Stadtplaner, D – Munich Physical and geometric principles 3.1 Gerd Becker, D – Munich 3.2 Gerd Becker, D – Munich 3.4 http://rredc.nrel.gov/solar/spectra/ am1.5/ (as of 12 September 2016) 3.5 Gerd Becker, D – Munich 3.6 Rainer Vallentin, D – Munich 3.7 after Schwaiger, Walter; Alber, Andreas; Albrecht, Christian: Technologie des ökologischen Bauens. Quoted from Daniels, Klaus: Low Tech Light-Tech High-Tech. Bauen in der Informationsgesellschaft. Basel / Boston / Berlin 1998, page 56 3.8 after Hegger, Manfred et al.: Energie Atlas. Munich 2007, page 21, figure A 1.8 3.9 Gerd Becker, D – Munich

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Technology and systems – photovoltaics 4.2 René Schmid Architekten AG, CH – Zurich 4.3 Widmann Energietechnik GmbH, D – Neuenstadt 4.4 Ralf Haselhuhn, D – Berlin 4.5 Stark, Thomas: Wirtschaftsministerium Baden-Württemberg (Ed.): Architektonische Integration von PhotovoltaikAnlagen. Stuttgart 2005, page 21 4.6 Data sources: Green, Martin Andrew; Emery, Keith et al.: Solar cell efficiency tables (Version 1– 39). In: Progress in photovoltaics: research and applications 1993 – 2012. Hoboken, New Jersey (USA) 1993 – 2011; National Renewable Energy Laboratory (NREL), Golden, Colorado (USA) 4.7 after Weller, Bernhard; Hemmerle, Claudia; Jakubetz, Sven; Unnewehr, Stefan: Photovoltaik. Munich 2009, page 11 4.8 Photos: 1 – 4: Technische Universität Dresden, Stefan Unnewehr; Photo 5: Odersun AG, Frankfurt / O.; Photo 6: Konarka Technologies, Inc. / Photo: Christopher Harting 4.9 AIG Gotha GmbH Architekten + Ingenieure, D – Gotha 4.10 BDM Architectes, F – Bordeaux 4.11 Ackermann und Partner, Architekten BDA, D – Munich 4.12 Assar Architects, B – Brussels 4.13 after ISFH / BINE 4.14 Caroline Wachsmann, D – Leverkusen 4.15 Ertex Solartechnik GmbH, A – Amstetten 4.16 – 4.18 DGS Guidelines for Photovoltaic Installations 2013 4.19 after HEAT Wärmesysteme, D – Weilheim / Teck 4.20 after Institut für Stromrichtertechnik und Elektrische Antriebe (ISEA), RWTH Aachen 4.21 DGS Guidelines for Photovoltaic Installations 2013 4.22 Ralf Haselhuhn, D – Berlin 4.23 after Weller, Bernhard; Hemmerle, Claudia; Jakubetz, Sven; Unnewehr, Stefan: Photovoltaik. Munich 2009, page 27 4.24 SMA Solar Technology AG, D – Niestetal 4.25 Nedap N.V., NL – Groenlo 4.26 Volker Quaschning, University of Applied Sciences (HTW), D – Berlin 4.27 Viessmann Werke GmbH & Co. KG, D – Allendorf (Eder) 4.28 Fraunhofer Institute for Solar Energy Systems ISE, D – Freiburg 4.29 Volker Quaschning, University of Applied Sciences (HTW), D–Berlin 4.30 Fraunhofer Institute for Solar Energy Systems ISE, D – Freiburg 4.31 University of Applied Sciences (HTW), D – Berlin 4.32 DGS Guidelines for Photovoltaic Installations 2013 4.33 Ralf Haselhuhn, D – Berlin 4.34 Alex Buob AG Dipl. Architekt HBK /SIA, CH – Rorschacherberg 4.35 Sunfilm AG, D – Großröhrsdorf 4.36 a Ralf Haselhuhn, D – Berlin 4.36 b OBO Bettermann GmbH & Co. KG, D – Menden 4.37, 4.38 DGS Guidelines for Photovoltaic Installations 2013 4.39 after VDE AR-2100-712

Technology and systems – solar thermal energy 5.1 after Hegger, Manfred et al.: Energie Atlas. Munich 2007, page 114, B 4.19 5.2 after www.energiewelten.de: HEA – Fachgemeinschaft für effiziente Energieanwendung e. V., D – Berlin 5.3 after ifeu-Institut, D – Heidelberg 5.4 Paradigma Deutschland GmbH, D – Dettenhausen 5.5 Grammer Solar GmbH, D – Amberg 5.6 Viessmann Werke GmbH & Co. KG, D – Allendorf (Eder) 5.7, 5.8 after Hegger, Manfred et al.: Energie Atlas. Munich 2007, page 120, B 4.38 5.9 Christian Richters / Banz + Riecks 5.10 after Hausladen, Gerhard; Tichelmann, Karsten: Ausbau Atlas. Munich 2009, page 116, B 4.27 5.11 after www.aee.at/publikationen/zeitung/ 2008-04/images/08_2.gif (as of 12 September 2016) 5.12 revised, after: Fisch, Manfred Norbert: Manuskript zur Vorlesung Solartechnik I, ITW Uni Stuttgart. Stuttgart 2007 5.13, 5.14 Christoph Maurer, D–Freiburg 5.15 Pistohl, Wolfram: Handbuch der Gebäudetechnik. Planungsgrundlagen und Beispiele. Volumes 1 and 2. Düsseldorf 2009 5.16 EnerSearch Solar GmbH, D – Waiblingen 5.17 Bernard Thissen / Energie Solaire S.A., CH – Sierre 5.18 Philippon-Kalt Architectes Urbanistes, F – Paris 5.19 Institut für Baukonstruktion, Lehrstuhl 2, University of Stuttgart 5.20 Roland Weegen, D – Munich Integration of solar installations 6.1 Andreas Keller, D – Altdorf 6.2 Viessmann Werke GmbH & Co. KG, D – Allendorf (Eder) 6.3 Jourda Architectes, F – Paris 6.4 Richie Müller, D – Munich 6.5 Jens Passoth, D – Berlin 6.6 Verena Herzog-Loibl, D – Munich 6.7 Caroline Wachsmann, D – Leverkusen 6.8 Roland Krippner, D – Munich 6.9 Rolf + Hotz Architekten, D – Freiburg 6.10 Patrick Pfeiffer, D – Konstanz 6.11 De Angelis Mazza Architetti, CH – Lugano 6.12 Roland Krippner, D – Munich 6.13 TU Munich, Prof. Thomas Herzog, Roland Krippner 6.14 Rolf Disch SolarArchitektur, D – Freiburg Designing and building − photovoltaics 7.1 grab architekten AG, CH – Altendorf 7.2 Willy Kracher, CH – Zurich 7.3 Swiss Solar Prize 2015 7.4 Beat Kämpfen, CH – Zurich 7.5 kämpfen für architektur ag, CH – Zurich 7.6 kämpfen für architektur ag, CH – Zurich 7.7 Beat Kämpfen, CH – Zurich 7.8 Zeljko Gataric, CH – Zurich 7.9 kämpfen für architektur ag, CH – Zurich 7.10 Miloni Solar AG, CH – Baden-Dättwil 7.11 kämpfen für architektur ag, CH – Zurich Designing and building – solar thermal energy 8.1– 8.4 Georg W. Reinberg, A – Vienna 8.5, 8.6 Architekturbüro Reinberg ZT GmbH 8.7 TU Graz, Institut für Wärmetechnik, working group Solarthermie und thermische Gebäudesimulation

Literature

Literature 8.8 Architekturbüro Reinberg ZT GmbH 8.9 Georg W. Reinberg, A – Vienna 8.10 – 8.13 Architekturbüro Reinberg ZT GmbH 8.14, 8.15 Rupert Steiner, A – Vienna 8.16 Pez Hejduk, A – Vienna 8.17, 8.18 a Architekturbüro Reinberg ZT GmbH 8.18 b Rupert Steiner, A – Vienna Economy and ecology 9.1 Claudia Hemmerle, electricity prices from BDEW Bundesverband der Energie- und Wasserwirtschaft e. V. (2015) 9.2 Claudia Hemmerle, from BKI Baukosteninformationszentrum Deutscher Architektenkammern (eds.): BKI Baukosten Positionen Neubau 2016, Cologne 2016, as well as from market research and information from manufacturers 9.3– 9.4 Claudia Hemmerle, D – Munich 9.5 Claudia Hemmerle, from data by the research group “Solar storage systems” of the HTW Berlin and the BDEW Bundesverband der Energie- und Wasserwirtschaft e. V., Berlin 9.6 Claudia Hemmerle from data by the research group “Solar storage systems” of the HTW Berlin and from the Reiner Lemoine Institute, Berlin 9.7– 9.9 Claudia Hemmerle, D – Munich 9.10 Claudia Hemmerle, data from DIN V 18 599, Parts 5 and 8 (2011) 9.11– 9.13 Claudia Hemmerle, D – Munich 9.14 Claudia Hemmerle, data from de WildScholten, Mariska: Energy payback time and carbon footprint of commercial photovoltaic systems. In: Solar Energy Materials & Solar Cells, Volume 119, 2013, pages 296 – 305, and El Khouli, Sebastian; John, Viola; Zeumer, Martin: DETAIL Green. Nachhaltig konstruieren. Munich 2014, as well as from independent extrapolations 9.15 Claudia Hemmerle, data from de Wild-Scholten, Mariska: Energy payback time and carbon footprint of commercial photovoltaic systems. In: Solar Energy Materials & Solar Cells, Volume 119, 2013, pages 296 – 305, and de Wild-Scholten, Mariska; Cassagne, Valérick; Huld, Thomas: Solar resources and carbon footprint of photovoltaic power in different regions in Europe. In: 29th European Photovoltaic Solar Energy Conference. Amsterdam 2014, as well as from independent extrapolations 9.16 Claudia Hemmerle, D – Munich Built examples page 106 Rupert Steiner, A – Vienna page 107 Georg W. Reinberg, A – Vienna page 108f. Mirlo Urbano Architekten, CH – Zurich pages 110f. Eibe Sönnecken, D – Darmstadt pages 112f. Willy Kracher, CH – Zurich pages 114f. Linda Blatzek, D – Trier pages 116f. Architekten Brüning Rein GmbH & Co. KG, D – Essen pages 118f. grab architekten AG, CH – Altendorf pages 120f. opus Architekten, Darmstadt pages 122f. Viridén + Partner AG, CH – Zurich pages 124f. HHS Planer + Architekten AG, D – Kassel pages 126f. Richter Dahl Rocha & Associés architectes SA, CH – Lausanne pages 128f. H.G. Esch, D – Hennef

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erzeuger und Stromgenerator. In: Schittich, Christian (ed.): Gebäudehüllen. 2., expanded edition. Munich /Basel / Boston / Berlin 2006, pages 46 – 59 Pawley, Martin: Theorie und Gestaltung im zweiten Maschinenzeitalter. Bauwelt Fundamente, Bd. 106. Brunswick / Wiesbaden 1998 PwC – PricewaterhouseCoopers Aktiengesellschaft (ed.): Energiewende-Outlook: Kurzstudie Wärme. Eine Untersuchung verschiedener Strategien zur Sicherstellung einer erfolgreichen Energiewende im Wärmebereich. Frankfurt a. M., January 2015. http://www.pwc.de/de/energiewende/assets/ pwcewokurzstudiewaerme2015.pdf (as of 11 August 2016) Schwarzburger, Heiko: Energie im Wohngebäude. Effiziente Versorgung mit Strom und Wärme. Das Gebäude. Berlin 2014 Sick, Friedrich; Erge, Thomas (eds.): Photovoltaics in buildings. A Design Handbook for Architects and Engineers. International Energy Agency; Paris, France / Solar Heating & Cooling Programme, Task 16. London 1996 Urbanek, Axel: Fünfzig deutsche Sonnenhäuser. Ausgeführte Solaranlagen aus den Jahren 1974 bis 1978. Gräfelfing 1979 Weber, Helmut: Integration von Solaranlagen in Gebäuden. In: DBZ – Deutsche Bauzeitschrift, 25. Jg., 2/1977, pages 207– 208 Technology and systems – photovoltaics DIBt – Deutsches Institut für Bautechnik (ed.): Bauregelliste. Bauregelliste A, Bauregelliste B und Liste C. Ausgabe 2015/2. Berlin, 6 October 2015. https://www.dibt.de/de/Geschaeftsfelder/BRL-TB.html (as of 12 August 2016) DIBt – Deutsches Institut für Bautechnik (ed.): Hinweise für die Herstellung, Planung und Ausführung von Solaranlagen. Berlin Juli 2012. https://www.dibt.de/en/Departments/Data/ Hinweise_Solaranlagen_Juli_2012.pdf (as of 12 August 2016) Haselhuhn, Ralf: Photovoltaik – Gebäude liefern Strom. BINE Fachbuch. Published by FIZ Karlsruhe – Leibniz-Institut für Informationsinfrastruktur. Stuttgart 2013 Henze, Andreas; Hillebrand, Werner: Strom von der Sonne. Photovoltaik in der Praxis. Techniken, Marktübersicht und Anleitung zum Selbstbau. Staufen bei Freiburg 2002 Hirn, Gerhard: Solarzellen mit Laser bearbeiten. Neues Verfahren zur Kontaktierung der Zellrückseite steigert Effizienz von Siebdrucksolarzellen. Published by FIZ Karlsruhe – LeibnizInstitut für Informationsinfrastruktur. BINE Projektinfo 08/2015. Bonn 2015 Konrad, Frank: Planung von Photovoltaik-Anlagen. Grundlagen und Projektierung. Wiesbaden 2007 Mertens, Konrad: Photovoltaik. Lehrbuch zu Grundlagen, Technologie und Praxis. Munich 2015 Wesselak, Viktor; Voswinckel, Sebastian: Photovoltaik – Wie Sonne zu Strom wird. Technik im Fokus. Berlin / Heidelberg 2016 Technology and systems – solar thermal energy Arkol-Forschungsprojekt/Fraunhofer-Institut für Solare Energiesysteme ISE (coordinator): Flexible Fassadenkollektoren für solare Architektur. BMWi-research project, running time: since 1 January 2016. https://arkol.de/de (as of 14 August 2016) Cappel, Christoph; Kuhn, Tilmann E.; Maurer, Christoph: Verfügbare Komponenten und Systeme fassadenintegrierter Solarthermie.

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Schabbach, Thomas; Leibbrandt, Pascal: Solarthermie. Wie Sonne zu Wärme wird. Technik im Fokus. Berlin 2014 Weyres-Borchert, Bernhard; Kasper, BerndRainer: Solare Wärme. Technik – Planung – Hausanlage. BINE-Fachbuch. Published by FIZ Karlsruhe – Leibniz-Institut für Informationsinfrastruktur. Stuttgart 2015 Designing and Building / Integration of solar installations Amt der Vorarlberger Landesregierung / Energieinstitut Vorarlberg (eds.): Solaranlagen planen und gestalten. Ein Leitfaden zur Errichtung von thermischen Solaranlagen und Photovoltaikanlagen. Bregenz / Dornbirn, June 2013. www.langen.at/Energie_und_ Umwelt/Leitfaden_zur_Errichtung_von_thermischen_Solar-_und_Photovoltaikanlagen (as of 12 August 2016) Auer, Falk: 25 Jahre Sonnenenergie. Ein Rückblick auf die ersten drei Ausgaben des DGSMitteilungsblatts. In: Sonnenenergie, 26. Jg., 1/2001, pages 14 –16 Bayerisches Landesamt für Denkmalpflege (ed.): Solarenergie und Denkmalpflege. Munich, November 2012 Busse, Hans-Busso v.; Müller, Helmut F. O.; Runkel, Susanne: Photovoltaik. Integration einer neuen Technologie in die Architektur. Photovoltaics. Integration of a new Technology in Architecture. Research report. Universität Dortmund, Fakultät Bauwesen, 1996 Deutsches Kupferinstitut (ed.): Architektur & Solarthermie. Darmstadt 2002 DGS – Deutsche Gesellschaft für Sonnenenergie, Landesverband Berlin Brandenburg e. V. (ed.): Photovoltaische Anlagen. Leitfaden für das Elektro- und Dachdeckerhandwerk, Fachplaner, Architekten, Ingenieure, Bauherren und Weiterbildungsinstitutionen. Berlin 5/2013 DGS – Deutsche Gesellschaft für Sonnenenergie, Landesverband Berlin Brandenburg e. V. (ed.): Solarthermische Anlagen. Leitfaden für das Elektro- und Dachdeckerhandwerk, Fachplaner, Architekten, Bauherren und Weiterbildungsinstitutionen. Berlin 9/2012 Hagemann, Ingo B.: Gebäudeintegrierte Photovoltaik. Architektonische Integration der Photovoltaik in die Gebäudehülle. Cologne 2002 Hermannsdörfer, Ingrid; Rüb, Christine (eds.): Solardesign – Photovoltaik für Altbau, Stadtraum, Landschaft. Berlin 2005 Herzog, Thomas; Krippner, Roland; Lang, Werner: Fassaden Atlas. 2., revised and expanded edition. Munich 2016 Hullmann, Heinz (ed.): Photovoltaik in Gebäuden. Handbuch für Architekten und Ingenieure. Stuttgart 2000 Humm, Othmar; Toggweiler, Peter: Photovoltaik und Architektur. Die Integration von Solarzellen in Gebäudehüllen. Basel / Boston / Berlin 1993 IdE – Institut dezentrale Energietechnologien gemeinnützige GmbH (ed.): SolFood. Leitfaden zur Vorplanung solarer Prozesswärme. Machbarkeitsabschätzung und Vorauslegung solarthermischer Prozesswärmeanlagen. Edited by Schmitt, Bastian; Lauterbach, Christoph; Vajen, Klaus. Kassel, March 2015. www.ide-kassel.de/fileadmin/user_upload/ images/projekte/SOLFOOD/SolFood_Leitfaden_Vorplanung.pdf (as of 12 August 2016) Klima- und Energiefonds (ed.): Solare Systeme im Objektbau. Ein Leitfaden zu Planung, Umsetzung und Betriebsführung. Vienna 2011. www.klimaaktiv.at/publikationen/erneuer-

bare-energie/solar_objektbau.html (as of 12 August 2016) Krippner, Roland; Plankemann, Dagmar: Zwischen Typologie und Denkmalschutz. Arbeiten zum Photovoltaikeinsatz im Gebäudebestand. In: 17. Symposium Photovoltaische Solarenergie. OTTI Technologie-Kolleg. Kloster Banz / Staffelstein, 13. –15 March 2002. Conference Proceedings. Regensburg 2002, pages 197– 202 Krippner, Roland: Architektonische Aspekte solarer Energietechnik. In: Wolfgang Schölkopf (ed.): Endbericht SOLEG. Solar gestützte Energieversorgung von Gebäuden. Würzburg 2002, pages 3.12-1– 3.12-29 Krippner, Roland: Energietechnik und Baukultur gehen Hand in Hand. Integration von Solarfassaden in den Gebäudebestand. In: B+B Bauen im Bestand, 38. Jg., 4/2015, pages 10 –14 Krippner, Roland: Ökologie vs. Ästhetik? In: DBZ – Deutsche Bauzeitschrift, 48. Jg., 9/2000, pages 114 –118 Krippner, Roland: Solartechnik in Gebäudehüllen. In: Detail Green, 1/2012, pages 53 – 57 Krippner, Roland: Zwischen Gebäudetypologie und Denkmalschutz. In: Bauhandwerk / Bausanierung, 21. Jg., 3/1999, pages 43 – 46 Krippner, Roland: Zwischen Teilvorfertigung und Universal-Baukasten – Zur Geschichte des Systembaus in Deutschland. In: Nerdinger, Winfried u. a. (eds.): Wendepunkte im Bauen. Munich 2010, pages 18 – 27 Lorenz, David: Problemfall Bestandsimmobilien? In: Immobilienwirtschaft, 5/2008, page 13 Lüling, Claudia (ed.): Energizing architecture. Design and photovoltaics. Berlin 2009 Moewes, Günther: Solar, defensiv oder beides? In: Detail, 37. Jg., 3/1997, pages 292 – 296 Munari Probst, Maria Cristina; Roecker, Christian: Architectural integration and design of solar thermal systems. Oxford /New York / Lausanne 2011 Neumann, Werner: Klimaschutz und Denkmalschutz. In: Denkmalpflege & Kulturgeschichte, 1/2009, pages 2 –7 Rexroth, Susanne (ed.): Gestalten mit Solarzellen. Photovoltaik in der Gebäudehülle. Heidelberg 2002 Roberts, Simon; Guariento, Nicolò: Gebäudeintegrierte Photovoltaik. Ein Handbuch. Basel / Boston / Berlin 2009 Solares Bauen. Special issue of the journal “Sonnenenergie”. Berlin, October 2002 Stark, Thomas: Aktive Solarenergienutzung. In: Jan Cremers (ed.): Atlas Gebäudeöffnungen. Munich 2015, pages 190 –197 Weller, Bernhard u. a.: Photovoltaik. Detail Praxis. Munich 2009 Economy and Ecology Bayerisches Landesamt für Umwelt – LfU (ed.): Berechnung von Immissionen beim Brand einer Photovoltaik-Anlage aus Cadmiumtellurid-Modulen. Edited by: Beckmann, Jürgen; Mennenga, Anke. Augsburg, November 2011. www.lfu.bayern.de/luft/doc/pvbraende.pdf (as of 13 August 2016) Hane, Axel; Hirn, Gerhard: Recycling von Photovoltaik-Modulen. In: BINE projektinfo 02/10. published by FIZ Karlsruhe – Leibniz-Institut für Informationsinfrastruktur. Bonn 2010 Hemmerle, Claudia; Jakubetz, Sven: Zukunftsstrom aus historischen Mauern. In: eta green, 01/2010, pages 16 –19 IINAS – Internationales Institut für Nachhaltigkeitsanalysen und -strategien (ed.): GEMIS –

Regulations, guidelines, standards

Regulations, guidelines, standards Globales Emissions-Modell integrierter Systeme. Version 4.9. Darmstadt 2014. www.iinas.org/gemis-download-de.html (as of 13 August 2016) Kaltschmitt, Martin; Streicher, Wolfgang; Wiese, Andreas (eds.): Erneuerbare Energien. Systemtechnik, Wirtschaftlichkeit, Umweltaspekte. Berlin 2013 Quaschning, Volker: Erneuerbare Energien und Klimaschutz. Hintergründe, Techniken und Planung, Ökonomie und Ökologie, Energiewende. Munich 2013 Wagner, Ulrich: Potentiale und Kosten Erneuerbarer Energien. In: Technik in Bayern. Nachrichten aus Technik, Naturwissenschaft und Wirtschaft, 6/2005, page 12

Act for the development of renewable energy sources (Renewable Energy Sources Act – EEG 2014: Erneuerbare-Energien-Gesetz) Act on Electricity and Gas Supply: Energy Industry Act (EnWG 2016: Energiewirtschaftsgesetz) BGV: Employers’ Liability Insurance Association Regulations (Berufsgenossenschaftliche Vorschriften) BGV A2 Electrical facilities and equipment BGV A3 Testing of electrical facilities and equipment BGV C22 Construction work Building Rules List of the German Institute for Construction Technology (DIBt): (Bauregelliste des Deutschen Instituts für Bautechnik) Building Rules List (Bauregelliste) B Part 1. 2015 DIN 4102 Fire behaviour of building materials and elements. 2016 DIN 18 008-2 Glass in Building – Design and construction rules – Part 2: linearly supported glazings. 2010 DIN 18 008-3 Glass in Building – Design and construction rules – Part 3: Point fixed gazing. 2013 DIN 18 008-4 Glass in Building – Design and construction rules – Part 4: Additional requirements for barrier glazing. 2013 DIN 18 015-1 Electrical installations in residential buildings – Part 1: Planning principles. 2013 DIN 18 015-2 Electrical installations in residential buildings – Part 2: Nature and extent of minimum equipment. 2010 DIN 18 015-3 Electrical installations in residential buildings – Part 3: Wiring and disposition of electrical equipment. 2016 DIN 18 516-4 Back-ventilated, non-loadbearing, external enclosures of buildings, made from tempered safety glass panels: requirements and testing. 1990 DIN EN 410 Glass in building - Determination of luminous and solar characteristics of glazing. 2011 DIN EN 673 Glass in building – Determination of thermal transmittance (U value) – Calculation method. 2011 DIN EN 1090-1 Execution of steel structures and aluminium structures– Part 1: Requirements for conformity assessment of structural components. 2012 DIN EN 1090-2 Execution of steel structures and aluminium structures– Part 2: Technical requirements for steel structures. 2012 DIN EN 1090-3 Execution of steel structures and aluminium structures– Part 3: Technical requirements for aluminium structures. 2012 DIN EN 1991-3 Actions on structures – Part 3: Actions induced by cranes and machinery. 2010 DIN EN 1991-4 Actions on structures – Part 4: Silos and tanks. 2010 DIN EN 1993-1 Design of steel structures – Part 1-1: General rules and rules for buildings. 2014 DIN EN 1999-1-1 Design of aluminium structures – Part 1-1: General structural rules. 2014 DIN EN 12 975-1 Thermal solar systems and components – Solar collectors – Part 1: General requirements. 2011 DIN EN 13 501 Fire classification of construction products and building elements. 2010 DIN EN 14 449 Glass in building – Laminated glass and laminated safety glass – Evaluation of conformity / Product standard. 2005 DIN EN 50 583-1 (VDE 0126-210-1) Photovoltaics in buildings – Part 1: BIPV modules. 2016

DIN EN 50 583-2 (VDE 0126-210-2) Photovoltaics in buildings – Part 2: BIPV systems. 2016 DIN EN 61 730-1 (VDE 0126-30-1) (IEC 61730-1) Photovoltaic (PV) module safety qualification – Part 1: Requirements for construction . 2012 DIN EN 62 446 (VDE 0126-23) Grid Connected Photovoltaic Systems – Minimum Requirements For System Documentation, Commissioning Tests And Inspection. 2013 DIN EN ISO 10 077-1 Thermal performance of windows, doors and shutters – Calculation of thermal transmittance – Part 1: General. 2010 DIN EN ISO 10 077-2 Thermal performance of windows, doors and shutters – Calculation of thermal transmittance – Part 2: Numerical method for frames. 2015 ETAG 002 Structural Sealant Glazing Systems. 2003 Federal Building Code (Baugesetzbuch BauGB). 2015 IEC 61215 Terrestrial photovoltaic (PV) modules – Design qualification and type approval. 2006 IEC 61646 Thin-film terrestrial photovoltaic (PV) modules – Design qualification and type approval. 2009 LAI – Guidelines for noise action planning. 2012 Low Voltage Directive 2014/35/EU Model Building Ordinance (MBO: Musterbauordnung). 2012 Model directive for fire-safety requirements in circuitry. (Model Wiring Systems Directive MLAR (Muster-Leitungsanlagen-Richtlinie)). 2005 National General Building Approval (Allgemeine bauaufsichtliche Zulassung (abZ)) No. Z-30.3-6 Products, connections and building components of stainless steel. 2014 Technical regulations for operational safety (Technische Regeln für Betriebssicherheit) TRBS 1201 Inspections of equipment and installations requiring monitoring. 2012 TRBS 2131 Electrical hazards. 2007 VDE 0100-610 Erection of low-voltage installations, Part 6: Verification. 2008 VDE 0100-712 Low-voltage electrical installations – Part 7-712: Requirements for special installations or locations – Photovoltaic (PV) systems. 2016 VDE 0105 Operation of electrical installations. 2014 VDE 0105-100 Operation of electrical installations, Part 100: General requirements. 2015 VDE 0126-210-1 (DIN EN 50583-1) Photovoltaics in buildings – Part 2: BIPV modules. 2016 VDE 0126-210-2 (DIN EN 50583-2) Photovoltaics in buildings – Part 2: BIPV systems. 2016 VDE 0185-305 Protection against lightning VDE 0185-305-1 General principles. 2011 VDE 0185-305-2 Risk management. 2013 VDE 0185-305-3 Physical damage to structures and life hazard. 2016 VDE 0185-305-4 Electrical and electronic systems within structures. 2011 VDE 0298-4 Application of cables and cords in power installations – Part 4: Recommended current-carrying capacity for sheathed and nonsheathed cables for fixed wirings in and around buildings and for flexible cables and cords. 2013 VDE-AR-E 2100-712 Measures for the DC range of a PV installation for the maintenance of safety in the case of firefighting or technical assistance. 2013 VDE-AR-N 4105 Low voltage generation – Technical minimum requirements for connection and parallel operation of generating plants at the low-voltage network. 2011

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Appendix

Glossary absorber The part of the thermal collector whose purpose is uptake of solar energy. Usually made of aluminium or copper sheet metal, it heats up when irradiated by sunlight. The term is also commonly used for uncovered solar collectors, which are mainly used for the heating of swimming pools. accumulator Rechargeable, usually electrochemical device for storing electrical energy. active (indirect) use of solar energy Employment of technological means to absorb, distribute and, where applicable, store solar energy. additive mounting Describes the process in which the solar installation is placed on the building so that it is separate from the water-bearing layer. air collector Solar collector in which air acts as the heat transfer medium instead of a liquid. amorphous silicon (a-Si) Non-crystalline silicon with a disordered atomic structure used in the manufacture of thin film solar cells. annual coefficient of performance (COP) Value denoting the energy efficiency of heat pumps. It describes the ratio of the delivered cooling or heating power (heat) to the input power (e.g. electrical energy) of a heat pump over the course of a year. The annual COP provides a benchmark for the overall efficiency of a heat pump for an annual cycle. base load Minimum energy usage threshold that is not crossed during a defined time interval. If the base load is exceeded, peak load supply systems are employed to cover the additional usage. buffer tank Water-filled heat storage tank of a heating system that helps to bridge the time interval between energy generation and energy use. building-integrated solar technology Structural as well as aesthetic incorporation of photovoltaic modules and /or solar thermal collectors into the building shell. calorific value Quantity describing the usable heat energy released in the combustion of a material. coefficient of performance (COP) Quantity used to assess the efficiency of heat pumps and refrigerators. In the context of heat pump processes, the quantity describes the ratio of the delivered heating power to the input (e.g. electric) power (including auxiliary energy) under standard conditions. A COP of 2.0 means that the pump delivers twice the energy (in form of heat) as is required to operate the pump. The value is useful only in an evaluation of the efficiency of a device, and cannot be used for the overall energy assessment of an entire system. combination storage tank Heat tank of a heating system that is used to store heat for use in both domestic water and space heating. There are “tank-in-tank” systems

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as well as systems with an auxiliary potable water station, in which the water is heated using the flow-through principle. copper indium diselenide, copper indium disulfide (CIS), copper gallium diselenide (CiGS) Semiconducting materials for thin film solar cells, optionally alloyed with gallium. degradation Decrease in the efficiency of solar cells due to aging and/or commissioning (initial degradation). degree of self-sufficiency Value that describes to what degree a household is able to supply itself with energy from its own solar installation. diffuse radiation Portion of global radiation that is undirected due to scattering during its passage through the atmosphere. direct (passive) use of solar energy Employment of specific, structural means to collect, store and distribute irradiated solar energy without the use of technological installations. direct radiation Portion of global radiation that passes through the atmosphere unscattered, striking the Earth’s surface in a straight line and capable of casting hard shadows. dye (-sensitised) solar cell Nano-structured solar cell based on the semiconductor titanium dioxide and an organic dye. energy [J or kWh] A physical quantity that describes the stored work of a system. Energy can be neither created nor destroyed, but can only be stored, transported or converted from one form (e.g. electricity, radiation) to another. Its utility can decrease during transformation or transport, since energy conversion does not function in arbitrary directions. energy payback period, energy amortisation Time span over which an energy generation system delivers as much energy as was required in its manufacture. After the energy payback period a system will manifest a positive energy balance.

end use energy The energy that is actually used by the end consumer. To get to this stage the final energy must usually be converted, incurring losses in the process. Types of end use energy are heat, cold, light, motion or sound waves. End use energy forms the basis for the German Energy Saving Ordinance (EnEV) calculation of the primary energy demand. EU Energy Performance of Buildings Directive (EPBD) (2010/31/EU) European Union directive passed in June of 2010 whose purpose is a Europe-wide reduction in the energy consumption of buildings. The implementation of this directive is set out by federal and state laws (German Energy Saving Orinance, EnEV). evacuated tube collector Type of solar collector that contains nested glass tubes which enclose a vacuum. The absorber – which takes different forms – is located inside the outer tube. feed-in compensation Remuneration received by solar installation owners from the network operators when they feed the electricity they generate into the municipal grid. In Germany, the Renewable Energy Sources Act (EEG) determines the minimum rates. final energy (J) The amount of energy that remains available to the end user at the point of consumption (e.g. electricity, wood pellets, heating oil or district heat) after all the conversion and distribution losses have been subtracted. The final energy is usually used as the basis for the calculation of energy costs. final energy demand Qf [kWh/year] The energy required to supply the usage energy (e.g, heating, domestic hot water, lighting, etc.) of a building. The final energy demand is calculated according to EnEV, which takes into account losses occurring during transfer, distribution, storage and conversion in the building. final energy usage [kWh/year] In contrast to the final energy demand, this is an actual energy amount measured at the building. It takes into consideration usage patterns and climatic fluctuations, for example.

energy source In its original sense, a naturally occurring raw material that can be used in chemical or nuclear processes to extract and convert its stored energy to usable forms (biomass, fossil and fissionable fuel). In common usage it is also used to describe renewable sources such as solar, geothermal, wind, or hydrological energy.

flat plate collector Type of solar collector with a smooth, flat absorber.

efficiency The ratio of output power (use) to input power (expenditure) under standard conditions. While efficiencies are theoretically limited to below 100 %, in practice (e.g. for condensing boilers) the stated values can exceed this limit. The input power is based on the calorific value of the fuel, as well as that of the condensation heat of the exhaust gas flow that is also utilised in the conversion process.

global radiation Sum total of the direct, diffuse and locally reflected radiation that strikes a horizontal surface on the Earth.

electricity generation costs Costs that are incurred in the conversion of a different form of energy into electricity.

flow (supply) temperature Temperature of the heat transfer medium (usually water) in the circulation system after it leaves the heat generator (see return temperature).

grid-independent (stand-alone) installation Electricity supply system that is not connected to the municipal electricity network, as opposed to a grid-connected installation. grid parity Situation in which the cost of generating electricity from renewable sources equals the price of conventionally sourced electricity.

Glossary

heat pipe Type of heating pipe that functions as a heat exchanger.

photovoltaics Means of converting sunlight into electrical energy.

indirect (active) use of solar energy Employment of technological means to absorb, distribute and, where applicable, store solar energy.

power [W] A quantity with the unit Watt (W) that describes energy used per unit time, i.e. the work done in a given time period. The electrical power is given by the product of current and voltage. In photovoltaics the instantaneous power generally lies below the maximum possible (rated) power output.

integrated installation Form of installation in which the solar energy system forms the water-bearing layer of the roof or facade. inverter Electrical device whose main function is the conversion of the direct current produced by the solar array into conventional alternating current. kilowatt-hour (kWh) Unit of energy. 1 kWh = 3,600 Ws = 3,600 J microcrystalline silicon (μc-Si) Silicon with a very fine crystal structure that is used in thin film solar cells. micromorph silicon (a-Si / μc-Si) Combination of amorphous and microcrystalline silicon in thin film solar cells. monitoring Describes all forms of systematic data acquisition, observation or tracking of an operation or process via technological means or through other forms of surveillance. monocrystalline silicon Homogeneous, high-quality silicon consisting of a single crystal (unlike polycrystalline silicon), which is cut into thin wafers to be used in the manufacture of solar cells. MPP charge controller Device used to match the optimal operating point of the inverter to the given maximum power point (MPP) of the solar generator. In the case of solar arrays this optimum operating point is not constant, but depends on ambient conditions such as radiation intensity, module temperature and solar cell type. nanoscrystal solar cell Type of solar cell on a nano-structured semiconductor substrate that can be produced quickly and with little energy in an inexpensive printing process; examples include dye-sensitised, organic or CIS nano cells. operating point A particular point on the characteristic curve of a technological device, determined by system properties and external conditions, at which the device functions. organic solar cell Nano solar cell on a substrate of semiconducting plastics or polymers. passive (direct) use of solar energy Employment of specific, structural means to collect, store and distribute irradiated solar energy without the use of technological installations. peak wattage (Wp) The unit of peak power in the maximum power point (MPP), usually determined under standard test conditions.

regions of a single semiconductor crystal, the p-type and n-type regions. solar collector Apparatus designed to extract energy from sunlight for purposes of water heating and/or cooling. solar constant Quantity describing the average of the intensities of orthogonally incident solar radiation at the outer edge of the Earth’s atmosphere over the course of a year. Its value is 1367 W/m2.

primary energy (J) The energy contained within the naturally occurring energy sources on Earth (e.g. coal, oil, natural gas, as well as sunlight, wind, water and the ground). In the conversion of primary energy to the end use energy consumed by the user, losses occur in transformation and transmission processes.

solar coverage The percentage of the entire energy demand of a building that is supplied by the solar energy system.

primary energy demand Qp [kWh/year] In computing the primary energy demand of a building according to the EnEV, the final energy demand must be determined first. The conversion losses are taken into account via the primary energy factor fp. The relationship between final energy demand Qf and primary energy demand Qp is given by Qp = Qf · fp.

solar (thermal) fluid Typically a water-glycol mixture used to convey heat from the solar collector to the storage tank.

primary energy factor fp [–] Constant of proportionality between the non-renewable primary energy used (including losses incurred during production, distribution and storage) and the final energy delivered. The primary energy factors used in the EnEV 2016, for example, are 1.1 for oil and natural gas, 1.8 for electricity and 0.2 for wood. The lower the primary energy factor, the more efficient the energy production from the corresponding primary energy sources. PV generator Modules connected together to form the field that is the energy-producing part of a PV installation. PV module Pre-assembled unit comprising several electrically connected solar cells that consists (depending on type) of a cover panel, composite material, solar cells, back panel, frame and wiring connectors. PVT collector Combination of photovoltaic (PV) and solar thermal (T) elements in a collector for the simultaneous conversion of sunlight into electricity and heat. reflection In optics, the bouncing of light rays off of an interface between two media of different optical density. The magnitude and type of reflection are influenced by the incident angle, polarisation and wavelength of the light, as well as the surface consistency and the characteristics of the materials. return temperature Temperature of the heat transfer medium (usually water) in the circulation system immediately before it enters the heat generator (see flow temperature). semiconductor p-n junction An interface between two differently doped

solar thermal energy Means of converting sunlight into usable thermal energy.

space heating demand QH [kWh/year] Calculated value denoting the amount of energy that must be delivered to a building during the heating period to cover heat losses and ensure that the interior temperature remains constant at the desired value. It is computed by subtracting solar and internal gains from transmission and ventilation heat losses. stratified tank Special variety of buffer storage tank. Nozzles on the side of the tank allow water (the heat transfer medium) to be stored and extracted in a temperature-dependent manner so that the water forms layers inside the tank (hot on top, cold on the bottom). Because of the resulting large temperature differentials that can occur within the tank, different heat sources (e.g. boilers, solar thermal collectors) and different heat flow circuits (e.g. floor heating, domestic hot water) can be connected to it. thermosiphon systems Simple solar thermal systems that do not require pumps but rely instead on gravity to circulate the water. Water is heated in the collector, expands and rises to the tank, which is located higher up. Cooler water flows back into the collector to be re-heated. Since these assemblies have to be protected from freezing, they are usually found only in warmer countries. thin film technology The deposition of thin solar cells a few microns thick of amorphous, microcrystalline of micromorph silicon as well as of cadmium telluride, copper indium diselenide/disulfide or copper gallium diselenide onto glass panels or flexible substrates (transparent or opaque foils) by means of various coating processes. vacuum deposition A process in which surface molecules of a material are evaporated in a vacuum and then deposited in thin layers on substrates. Such processes are physical (evaporation, sputtering) or chemical (thermal deposition, polymerisation). yield The usable energy supplied by a solar installation in a given time period.

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Appendix

Subject index absorber 52ff., 56, 58ff., 78, 82f., 89, 108 abZ (see National Technical Approval) AC coupling 37 Active Plus building standard 103 active use of solar energy 8, 10f., 19, 24, 72,75ff., 79, 81f. additive integration 64f., 68ff., 126 administrative building 96 air collector 12, 52f., 56, 59, 61f., 69, 82, 99 air mass (AM) 25 amorphous solar cell 31ff. ancillary construction costs 95 anti-freeze substance 53, 61, 83, 102 anti-reflection coating 31, 58 apartment building 18, 29, 41, 77, 79, 84, 90f., 94, 96f., 99, 108 Architecture Prize for BuildingIntegrated Solar Technology 9, 13ff. balustrade battery storage system

71, 77 18, 37f., 41f., 45, 73, 76, 93ff., 124 Bauregelliste (see Building Rules List) biogas cogeneration unit 29 bivalent operation 43 brine circuit 85 building energy demand 56, 77, 82, 85 building permit 47 Building Rules List 48f. building-integrated photovoltaics (BIPV) 6, 95f., 100 building-integrated solar technology 6, 7, 8ff., 13, 19, 22, 58, 64ff., 73ff., 78f., 86f., 89, 92, 99, 102f., 106, 108, 110, 114, 118, 120, 124 cadmium telluride (CdTe) solar cell 31, 33, 102 characteristic curve 35f. charge controller 36f. CIGS module 17, 33 CIS solar cell 31, 33, 102 cleaning 47 climate-conscious construction 80 CO2-equivalent 101 coefficient of performance (COP) 43 cold (rear-ventilated) facade 14, 79, 97 combination installations 84f., 99f. commercial building 17, 29, 77 commissioning 45, 88 concentrator 60 conservatory 81 construction law 47 Construction Products Directive 56 cost-effectiveness 41, 75f., 83f., 89, 91ff., 98ff. custom-made module 8, 11, 30, 75, 78, 94f., 116 DC coupling 37 declination 24 degradation 33 dehumidification 55, 62 depreciation 94 diaphragm expansion vessel 61 direct (immediate) use 96 direct marketing 93, 96 direct use of solar energy 8, 81 domestic water heating 34, 41, 98f. double glass module 30 drain back system 83 dummy module 67, 75, 78f. dye-sensitised solar cell 17f., 67, 75, 95, 126 eco-label “Blue Angel” 102 ecological balancing 100 EEG (Renewable Energy Sources Act) 21,92 EEG feed-in compensation 38, 40, 92ff., 96f. EEG tax 93, 96f. EEWärmeG (Renewable Energies Heat Act) 103 efficiency 30ff., 35, 57ff., 63, 75ff., 82, 94ff., 99

138

efficiency house plus 103, 120 electric heating rod 42 electric mobility 21, 93, 97, 103 electrical heating 43 electricity consumption 97 electricity mix 100, 102 electricity subscription price 97 emissions 101f. emissivity 53f. encapsulation 30 Energieeinsparverordnung (EnEV) 103 energy management system 41, 93, 97, 103 energy payback period 101 energy roof 9, 14ff., 78, 108, 112 Energy Saving Ordinance (EnEV) 103 energy self-sufficiency 15f., 18, 21f., 28f., 40, 76, 96f., 124 energy storage 29 energy transformation 20ff., 76 energy yield 27, 40, 81f., 99 EU Energy Performance of Buildings Directive 6, 9, 23, 103 EU Waste Electrical and Electronic Equipment (WEEE) Directive 102 European Solar Prize 13 evacuated tube collector 10f., 17, 52f., 56ff., 61, 67, 82, 87 event centre 16, 124, 126 existing /old building 65 existing building inventory 65f., 78f., 94, 100, 110, 122 exposure 26, 108 exterior wall 69f. External Thermal Insulation Composite System (ETICS) 97 facade facade integration

73, 120, 120, 122, 124, 126 65ff., 75ff., 79, 84, 86, 89, 91f., 94, 97, 99, 122 feed-in into electrical grid 92, 96 feed-in management 45 fire protection 39, 49ff. flat plate collector 9f., 52f., 56, 58f., 67, 82, 86, 118 flat roof 39, 49, 60, 69f., 86, 94 flexible PV module 17, 32f. frameless module 30, 71, 74, 118, 128 Fresnel collector 60 full (charge) cycle 38 generator junction box 44f. glare protection 47, 56, 58ff., 63 glass construction regulations 48 global radiation 25ff., 95 Grätzel cell 75, 126 gravity break 61 greening of buildings 68 grey energy 59 grid parity 93, 96 grid-connected photovoltaic (PV) array 28, 36, 75, 100 ground regeneration 55, 62, 85 g-value 56, 60, 63 heat demand 98f., 103 heat exchanger 60f., 83 heat generation costs 99f. heat meter 87, 91 heat pump 29, 34, 43f., 55, 62, 78, 89, 93f., 96f. heat transfer medium 52ff., 56ff., 60ff., 102 heating support 42f., 54, 62, 81, 83, 98 heatpipe 82, 89 high-efficiency solar cell 31f. historic monument preservation 22, 48, 65, 77, 88, 110 hot water collectors 82 hybrid module 34, 53, 78 hydraulic system 77, 87, 99

inclination angle indirect use of solar energy Individual Approval (ZiE) ingots installation insulation inverter kindergarten

26 8, 81 48f., 63, 128 31 44f., 50f., 92 84, 86ff. 36f., 40, 45ff., 77 106, 120

lead gel / lead-acid battery 37, 45 life cycle assessment 92ff. lifetime 34, 37f., 92 lightning and overvoltage protection 44, 51 lithium-ion battery 37f., 45 load management 41, 76, 97 load profile 41, 84, 96ff. local solar heating supply 22, 55, 85, 89, 91, 94 low-energy building 85 low-temperature heat 62, 76 maintenance market incentive programme market premium maximum power point (MPP) media facades micromorph solar cell Minergie-P-Eco mobility Model Building Code module current module inverter module voltage monitoring monocrystalline silicon cell

46f., 86 94 93 35f., 40 68 33 118 21 48ff. 36 40 36 88f. 30f., 95f., 114, 120, 122, 124, 128 monovalent operation 43 mounting system 39, 49, 68ff., 77, 89f. multifunctional building shell 12, 56, 60, 95, 103 museum 116 National Technical Approval (abZ) 48f., 63 near-zero-energy building 9 network expansion 93 new construction 65, 103 non-residential building 65, 94, 103, 124 non-return valve 61 office building operator models organic solar cell overhead glazing

110, 112, 114, 128 93 18, 31, 33f., 75, 96 48, 70, 106, 128

passive house 72, 76, 84f., 91, 112, 114 passive use of solar energy 8, 24, 72f., 75, 77, 81f., 86f., 90f., 112 PERC solar cell 32 phase-change materials (PCM) 73, 112 photovoltaic (PV) array 11, 24, 28, 38, 46, 68, 92f., 96, 114, 128 photovoltaic (PV) facade 11 photovoltaic (PV) module 30, 34, 36, 38, 40, 48, 62, 67, 94, 101f., 106, 108, 110 photovoltaics 6, 28ff., 75, 81, 86f., 89, 103 pitched roof 69, 74, 86, 90, 108, 110, 112, 114, 118 plus-energy house 11, 76, 97, 103, 114, 122 polycrystalline silicon cell 11, 30ff., 34, 67, 95f., 116 post-and-beam (stick system) facade 70, 124 power limiting 45 power optimiser 40 power specification 88 primary energy 101, 103 process heat 63, 82f., 85, 94 prosumer 22f. PVT collector 34, 53

Subject index

rear ventilation

40, 56, 58, 63, 70f., 74, 77f., 81, 86f., 95f., 110, 114, 116, 120 recycling 102 reflection 25, 53 Renewable Energies Heat Act (EEWärmeG) 103 renewable energy 20ff., 66, 102f. Renewable Energy Sources Act (EEG) 21, 92 research institute 128 residential building 65, 77, 79, 122 residential station 91 return temperature 90f. roof 73, 86 roof integration 65f., 68f., 75, 77, 108 roof window 108 roof-integrated installation 39, 50, 64, 69f., 108 roof-top installation 39, 69, 86f., 94f., 99 sawtooth roof 116, 120 seasonal sun protection 56 self-consumption 18, 38, 40ff., 44f., 75, 93f., 96ff., 103 shading 27, 36, 68, 77, 81, 86, 95, 99, 106, 124, 128 silicon 30ff., 102 simulation 27, 36, 49, 58, 63, 81, 84 single-family house 14, 19, 41, 44, 62, 77, 83f., 96ff., 108 sizing 64, 67, 84f., 98 skylight 106 small business regulation 93 smart grid 44 smart home /smart building 41 smart meter 41 solar building 6, 8, 18 solar cell 30f., 96, 102 solar constant 25 solar cooling 44, 55, 94, 99 solar coverage 40ff., 44, 64, 84f., 94, 96ff., 103 Solar Decathlon 15ff. solar energy 24, 72f., 79f., 86, 102 solar house 9ff., 21 solar irradiation 24, 26 solar pipes 44, 77, 86f., 89ff. solar spectrum 25, 35, 58 solar storage tank 54f., 60ff., 83ff., 88, 89, 98 solar thermal collectors 34, 52ff., 57, 61, 75, 81ff., 88f., 98ff., 102, 106, 110 solar thermal energy 6, 9, 12, 24, 52f., 73, 86f., 89, 92, 94, 98, 101ff. solar yield 40, 95f., 98ff., 103 sorption wheel 55, 62 specific annual energy yield 85 stagnation 63, 87 stand-alone (grid-independent) photovoltaic (PV) array 28 stand-alone system 28f., 124 standard module 8, 30, 48, 68, 71, 74, 88, 95f., 122, 124 standard test conditions (STC) 33, 35 state building regulation 47, 100 steam flow direction /steam pressure differential 86 stratified tank 61 string 30, 77 subsidy 92ff. sun path diagram 24f., 27 sun protection 12, 14, 28, 69ff., 95, 126 surface heating system 54, 99 swimming pool heating 53, 55, 62, 83 Swiss Solar Prize 13 synthetic module 34 system construction 68 tandem solar cell tax tenant's electricity tender

Thermally Activated Building System (TABS) 54, 56, 62, 90 thermosiphon system 62f., 83 thin film solar cell 29, 31ff., 36, 67, 74, 94ff., 101, 112, 118 tracking PV array 11, 12 transmission 53 transparency 12, 56, 59, 61, 71, 95, 124 triple solar cell 32 U-value

54, 56, 63

ventilation valve vertical glazing volume flow wafer warm facade water heating wiring

62 48 62 31, 100 11, 70f. 41f., 54, 62 81, 83ff., 87 36, 87ff., 91, 96

zero-energy building ZiE (see Individual Approval)

73ff., 112

32ff. 93f. 93 88, 93

139

Appendix

Register of companies and individuals Ackermann und Partner Architekten 17, 32, 67 AIG Gotha 32 Allmann Sattler Wappner Architekten 14, 67 Alt, Franz 9 Austria Solar 88 Banz+Riecks Architekten 17, 55 Bavarian Association for the Promotion of Solar Energy 6, 13, 23 BDM Architectes 32 Bonfig, Peter 14, 71 Brullet i Tenas, Miquel 11, 13 Bundesverband Solarwirtschaft 88 von Busse Klapp Brüning Architekten 17, 116 Buob, Alex 17, 49 Cucinella, Mario

14

Daniels, Klaus DeAngelis Mazza Architetti Deppisch Architekten Dietrich l Untertrifaller Architekten Disch, Rolf

9 15, 71 9, 15 71 11, 13, 71

École Polytechnique Fédérale de Lausanne (EPFL) 75, 130 Feinhals, Georg Foster, Norman Frei, Ivo FS Architekten Funk und Schröder von Garnier, Friedrich Ernst Gaß, Nabo Giselbrecht, Ernst Goetzberger, Adolf Grab Architekten Grätzel, Michael Graf, Architekturbüro

11 20 17, 59 11 17 17, 18 16 21, 23 72, 118 33, 126 16, 17

Haller, Fritz 68 Harder Haas Partner 78 HBH, Architekten 13 Hegger, Manfred 12, 16, 18, 124 HENN 128 Herzog, Thomas 10, 14, 18, 67, 71 HHS Planer + Architekten 12, 16, 18, 124 Hölken & Berghoff Architekten 21 Hostetter & Partner 12 Hotz, Theo 12 in situ, Baubüro Ito, Toyo

18, 75 17f.

Jenni Energietechnik Jourda Architectes Jourda + Perraudin Jung, Ingenieurbüro

85 17, 67 12 85

Kämpfen, Beat Kaufmann, Hermann Koolhaas, Rem Kramm & Strigl Architekten Krippner, Roland

14, 72, 75ff., 112 17 19 11 71

Lichtblau Architekten Lorenz, Peter

15, 107 62

Månsson Dahlbäck Arkitektkontor Miloni, Reto Mirlo Urbano Architekten

17, 65 78 17, 112

opus Architekten Philippon-Kalt Architectes Piano, Renzo PMP Architekten Präg, Christof

140

14, 114, 124 61 17 13 13

Puccetti, Paolo

10

Raymond, Eleanor 9 Reinberg, Georg W. 82, 85, 87, 89, 91, 106 Resch, Michael 14, 65 Richter Dahl Rocha & Associés 17, 126 Riemer Planung 29 Rolf + Hotz Architekten 14, 68 Rougé, Jean François 17 Schaudt Architekten Schempp, Dieter Schilling, Bernhard Schmid, René Schmidhuber Schumacher, Ernst Friedrich Sobek, Werner Solarenergieförderverein Bayern e. V. Stein Hemmes Wirtz Architekten

11 19 10 6,16, 29 18 9 21, 23 6, 13, 23 114

Taut, Bruno Telkes, Maria

67 9

Unterrainer, Walter Urbanek, Axel

12 9

Viridén + Partner Vitruvius Volz, Tina

79, 105, 122 64 14, 65

Wachsmann, Caroline Weller Architekten Wild, Arnold Wolf, Eckard Wortmann Architekten zillerplus Architekten und Stadtplaner

35, 68 29 18, 68 12 17 23