Renewable Energy in Cuba: Overview, Tutorial, and Recommendations (SpringerBriefs in Energy) 303137472X, 9783031374722

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SpringerBriefs in Energy Slobodan Petrovic

Renewable Energy in Cuba Overview, Tutorial, and Recommendations

SpringerBriefs in Energy

SpringerBriefs in Energy presents concise summaries of cutting-edge research and practical applications in all aspects of Energy. Featuring compact volumes of 50 to 125 pages, the series covers a range of content from professional to academic. Typical topics might include: • • • • •

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Slobodan Petrovic

Renewable Energy in Cuba Overview, Tutorial, and Recommendations

Slobodan Petrovic Oregon Institute of Technology Portland, OR, USA

ISSN 2191-5520     ISSN 2191-5539 (electronic) SpringerBriefs in Energy ISBN 978-3-031-37472-2    ISBN 978-3-031-37473-9 (eBook) https://doi.org/10.1007/978-3-031-37473-9 © The Editor(s) (if applicable) and The Author(s), under exclusive license to Springer Nature Switzerland AG 2023 This work is subject to copyright. All rights are solely and exclusively licensed by the Publisher, whether the whole or part of the material is concerned, specifically the rights of translation, reprinting, reuse of illustrations, recitation, broadcasting, reproduction on microfilms or in any other physical way, and transmission or information storage and retrieval, electronic adaptation, computer software, or by similar or dissimilar methodology now known or hereafter developed. The use of general descriptive names, registered names, trademarks, service marks, etc. in this publication does not imply, even in the absence of a specific statement, that such names are exempt from the relevant protective laws and regulations and therefore free for general use. The publisher, the authors, and the editors are safe to assume that the advice and information in this book are believed to be true and accurate at the date of publication. Neither the publisher nor the authors or the editors give a warranty, expressed or implied, with respect to the material contained herein or for any errors or omissions that may have been made. The publisher remains neutral with regard to jurisdictional claims in published maps and institutional affiliations. This Springer imprint is published by the registered company Springer Nature Switzerland AG The registered company address is: Gewerbestrasse 11, 6330 Cham, Switzerland

Preface

This book examines the energy system in Cuba and is intended to serve as a quick reference guide for anyone who wishes to learn about the topic from a concise source. The main motivation behind this book is to offer an unbiased opinion about the energy shift in Cuba, contribute to the relevant experience about renewable energy sources, and offer encouragement for the plan to increase their contribution. The analysis leads to an understanding of Cuba’s energy generation, use, distribution, transmission, and future plans. Cuba’s energy system is a unique example in the world of a system that is not only geographically isolated from neighboring countries as an island, but also has been geopolitically sequestered for nearly six decades. As such, Cuba’s energy system is an interesting case study of a self-developed system. The book originated from the author’s experience teaching renewable energy engineering for more than 20 years. While the main components of an energy education include gaining knowledge, techniques, skills, and tools of a discipline to solve technical problems, learning about diversity and contemporary professional, societal, and global issues is also important. In my years of teaching, I have discovered that the analytical rigor of teaching about designing systems, using the appropriate math, and conducting and analyzing experiments, lacks the vitality of applying that knowledge to contemporary issues and placing the acquired knowledge in the context of practical global topics. As a result, the engineering students in the program have been involved in studies of energy systems across the world. Cuba’s energy system has emerged as an interesting example of a system characterized by sequestration, heavy reliance on fossil fuels, and a fragile electrical grid prone to resilience problems, but a system with significant potential in renewable energy to achieve self-sufficiency in the future. While conducting the analysis of Cuba’s energy system, it became apparent that the text would gain significance and multi-level relevance by blending the analysis of the country’s energy system and its potential for renewable energy, with embedded tutorials for each energy generation and storage method. The book will appeal to a diverse readership, including those with a reasonable level of understanding of renewable energy and those wishing to learn the fundamentals of energy generation, storage, and specifically about renewable energy sources. Hence, the text is an v

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overview, with the central theme of Cuba’s renewable energy potential. It is a concise tutorial on all renewable energy sources, their fundamentals, and practical issues necessary for their development and implementation. The two aspects of the text are sometimes amalgamated to best explain the elements of Cuba’s energy system’s details in the context of teaching the technology basics. This combination may be attractive for a diverse audience, from energy engineering students who would apply their knowledge to review practical, complete energy systems, those interested in prospects for participating in the energy shift in Cuba, to those without substantial technical background who would benefit from the first tutorial on renewable energy sources. While there are some excellent articles on a variety of topics pertaining to energy in Cuba, some are of a narrow scope, and some have been severely dated. This book offers the latest compilation of publicly available information and a concise overview of Cuba’s energy. The collection and data access in preparation for this book have been challenging, and a variety of reasons can be offered to explain scarcity or accuracy of information. The main resources included news articles, government documents, company websites, research and journal articles, and library searches. Many resources lacked authority (i.e., not coming from original authors), relevance (severely out of date), or reliability. As a result, the author does not claim absolute data completeness or accurateness; however, the possible lack of some details is not expected to affect the main expectation from this text and the important trends. While most of the research was web-based, the writing of the book required multiple trips to the captivating country of Cuba, where it was possible to meet their wonderful people, learn first-hand about the energy delivery and the observable advantages and disadvantages, and evaluate the potential for developing renewable energy sources and energy storage. Portland, OR, USA May 2023

Slobodan Petrovic

Contents

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Energy in Cuba: Overview������������������������������������������������������������������������   1

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 Energy Generation and Consumption ����������������������������������������������������   7 Coal������������������������������������������������������������������������������������������������������������    8 Oil and Natural Gas ����������������������������������������������������������������������������������    9

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Renewable Energy Sources ����������������������������������������������������������������������  11

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Energy Storage ������������������������������������������������������������������������������������������  39

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Electrical Grid and Energy Resiliency����������������������������������������������������  45

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Conclusions and Recommendations��������������������������������������������������������  53

References and General Bibliography ������������������������������������������������������������  55 Index��������������������������������������������������������������������������������������������������������������������  59

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Chapter 1

Energy in Cuba: Overview

Abstract  This introductory chapter gives an overview of Cuba’s history of energy development and the current energy generation contributions by different sources. The recent history of energy is examined in the context of country’s plan (Revolucion energetica) for increasing the contribution by renewable energy sources by 2030. The types of renewable energy sources that Cuba is considering developing have been discussed in the context of country’s location and natural resources. The geopolitical circumstances affecting energy system design for the country have been put into the context. Keywords  History of energy in Cuba · Revolucion energetica · Fossil fuels in Cuba · Renewables in Cuba · Hydropower in Cuba · Solar PV in Cuba · Biomass in Cuba · Distributed generation The Republic of Cuba is the largest Caribbean Island with the area of 109,880 km2. It is located between the Gulf of Mexico, Atlantic Ocean, and the Caribbean Sea and only about 100 miles south of Florida. Cuba has no land borders with other countries and maritime borders with the United States, Mexico, Jamaica, Honduras, Haiti, and the Bahamas. The shape of the main island is long and narrow. It is over 700 miles long and less than 60 miles wide. The geography shows mostly the lowland and about one-­ third are the mountain and hills. An average elevation is 108 meters above sea level. The highest point is Pico Turquino at 1974 m. There are over 4000 smaller islands as part of Cuba. The population of Cuba is slightly over 11 million. Over 70% of the population lives in urban areas, and the population of the largest city, Havana, is over 2 million, almost 20% of the total population. Per capita energy consumption in Cuba is 3.855 kWh per day, which is very low compared to many other countries. Natural resources include cobalt, nickel, iron ore, copper, manganese, salt, timber, silica, and petroleum. The most important Cuban mineral economic resource is nickel.

© The Author(s), under exclusive license to Springer Nature Switzerland AG 2023 S. Petrovic, Renewable Energy in Cuba, SpringerBriefs in Energy, https://doi.org/10.1007/978-3-031-37473-9_1

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The country’s rich and turbulent history has been characterized by wars, changes in governments, and overall instability. In the last 50 years, much of the Cuban way of life, including energy, was affected by the US sanctions. The history of sanctions reveals (US Department of State) that an embargo was first imposed on the Republic of Cuba in 1962  in response to certain actions by the Cuban government. The embargo, called a “blockade” in Cuba, has been in effect since, with some changes implemented in 2017. It is not the intent of this publication to discuss the US embargo on Cuban trade, but understanding the circumstances helps in building a comprehensive outlook on the energy in Cuba. The country has faced at times devastating isolation that affected every aspect of life and economy and has also shaped the energy generation and use. The restrictions on international commerce meant that Cuba could not import and exchange goods, services, and knowledge freely as practically every other country in the world. As such, Cuba is a unique example of economy that has been developing on its own, in isolation from the rest of the world. While this has brought incredible suffering to the people of Cuba and cannot been taken lightly, it also presents itself as an ideal study example of how the modern world develops. With all basic components of life, the economic and political isolation has affected the complete energy network of the country. Unable to import and exchange technological advances in the energy generation technologies, the use of new materials for electrical power devices, modern energy storage devices, and all supporting technologies, Cuba largely remained years behind in the energy development from other developing countries. At the time of writing this text, for example, Cuba is facing one of the most severe gasoline shortages in its history. According to official Cuban news, the shortage of gasoline has been created because of noncompliance of the supply countries to deliver agreed-upon quantities. The Cuba’s daily gasoline consumption is 500–600 tons, while the current supplies provide only less than 400 tons. At the same time, the country is trying to maintain its electricity generation using several thermoelectric power plants. According to the most recent data, the crude oil is provided from the Venezuelan state oil company at an increasing rate which rose in 2023 from 40,000 barrels per day in January to 76,000  bpd in March. Still, the county struggling to secure sufficient electricity and the blackouts are regular, especially in the summer months. Cuba does not have the natural geographical conditions for development of location-dependent renewable energy sources and was, therefore, largely oriented on using fossil fuels. Over 85% of the consumed energy comes from fossil fuels, oil, and natural gas. Not surprisingly, biofuel is used as well, but to a smaller percentage. The contribution of renewables has been very low, roughly only 1%. Given the current conditions, it is nearly impossible for Cuba to follow any energy policies. However, Cuba has a master plan to grow its power generation from solar PV, wind, and hydro from less than 1% in 2014 to 10% by the year 2030. The plan entitled Revolution Energetica began in the year 2000, with a five-point plan that included energy efficiency, conservation, and introduction of renewables. The initiatives called for upgrading appliances and replacing old lightbulbs with fluorescent lightbulbs and resulted in annual electricity consumption reduction by over 3%. In

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Fig. 1.1  Pie chart depicting the expected energy mix of Cuba by 2030

addition, electricity tariff plan was introduced, and the electrical grid was decentralized to enable energy consumption closer to generation. Final goals of the plan included introduction of renewables, exploration of domestic oil and gas, and encouragement of foreign investment in building renewable energy infrastructure. By 2017, Cuba has moderately changed the energy generation mix for generating electricity and increased contribution from renewables to 4% (from the 1% reported in 2014). The plans aim to have 24% from renewables by 2030 [13]. Figure 1.1 shows the expected energy mix by 2030. Cuba does not have a large domestic fuel supply operation, although they have increased their capacity in recent decades due to geopolitical circumstances discussed in the next section [1]. As mentioned previously, the domestic oil in Cuba contains traces of sulfur that corrode equipment in power stations, leading to power plant failures and lasting blackouts [13]. Significant historical events have shaped the current Cuba’s energy system. Since its revolution in 1959, Cuba kept searching for a reliable energy supply, and during the Cold War, Cuba established close ties with former country of Soviet Union, which enabled favorable conditions for import of crude oil, which was used in fossil fuel burning power plants. The outlook with majority of energy generation remained very similar, with over 85% of overall generation still being supplied by fossil fuels. In 1991, after the collapse of Soviet Union, Cuba lost the main source energy and was plunged into a deep energy crisis. This was the time of great economic depression in general, characterized by food, oil, and gas shortages for several years. It was during this period that Cuba’s leadership started realizing that the answers for energy independence were in developing alternative energy generation sources, primarily renewables. The transition has, however, been slow, and more than 30 years later, the breakdown of energy mix (i.e., relative contributions from different sources) is showing only a slight increase in contribution of renewables. After a particularly harsh period in its history, in 2002, Cuba entered a barter agreement (i.e., a trade of goods, services, and products in place of exchanging monetary payments) with Venezuela for import of oil, in exchange for medical

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services. This resulted in crude oil imports to Cuba worth $14 B, in the period of 2003–2009 [13]. The barter agreement seems to be effective to this day, despite significant political challenges for both countries, albeit diminishing deliveries from Venezuela. In response to what appeared to be the next significant energy supply crisis, Cuba’s leadership began implementing measures to reduce reliance on foreign oil imports by drastic reduction in fuel consumption through reduced bus services, reduced air conditioning, reduced workdays for government workers, and limiting the availability of gasoline for the public. With its unique geographical position, Cuba is highly sensitive to adverse effects of climate change. Extreme weather events have become more frequent and of higher intensity. The droughts have increased in severity, and rate of occurrence and extreme weather conditions continue to worsen year after year. There are reports of obvious effects of climate change in rising sea levels and alarming report by the Intergovernmental Panel on Climate Change that Cuba stands to lose more than 3% of its land due to sea level rising by 2050. The most significant aspect of any evaluation of Cuba’s energy system is country’s determination to dramatically shift to renewables. The progress toward that goal and the targets for year 2030 may seem modest or non-existing (for some types of renewable energy), but the determination and political will appears to be strong and Cuba may be on the way to change its future for the next generation. This is a visionary and worthwhile goal that the government of Cuba and several private enterprises have taken for the benefit of Cuban people. Once energy independence is achieved, the overall Cuban economy and standard of living of its citizens will dramatically improve, which gives hope for better life for Cubans in the years to come. This monograph helps, in a small way, to raise education about the energy in Cuba and potentially open the doors for better education, investments, initiatives, and ultimately a change. In 2014, Cuba’s energy generation mix (relative percentage of contribution) included 95.9% oil-derived fossil fuels, 3.3% biomass, 0.1% solar photovoltaics, 0.5% hydropower, and 0.1% wind energy. Looking at these numbers even inexperience leader must conclude that the energy generation situation is not the brightest, especially given the fact that over 80% of the crude oil is imported, which would mean a dangerous dependence on global economic and political circumstance. It is also quite reasonable to assume that a prosperity of any country must be founded on two domestic resource capabilities, producing its own food and generating its own energy. This may sound as a narrow-vision statement in this time of great connectedness in the world, but we have also seen how global political situation changes rapidly and previous agreements and trade flows disappear overnight. In case of a country like Cuba, the effects of global political circumstances have produced maybe the only example of a country in the world that was faced with strong isolation and had undergone developments in all sectors of life with only small, sliver openings for collaborations, trade, and cooperation. Cuba is an example of a country that had some of the important aspects of a complex set of activities necessary for a country to function diminished or disabled due to economic and

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political blockade; and, to use a metaphor, Cuba is as study case of a country “frozen in time,” not being able to freely, for several decades, exchange goods, technology advancements, and even knowledge. The country did the best it could, carrying for its citizens in some areas, notably health care and education. But the constrains of the decades-long isolation and the pressures of surviving in never-ending difficult times meant that some aspects of the country’s development were neglected or simply there was not sufficient resources to implement changes. While in this generation, from 2006, the energy revolution has started (Revolucion Energetica), this opinion piece contends that it should have started much earlier with the foresight that energy and sufficient electricity is arguably more important than all other aspects of country’s economy, as it is the basis for all other essential industry such as agriculture, mining, or tourism. In contrast to energy breakdown in 2014, the energy revolution set plans in motion for year 2030 to reduce contribution of fossil fuels to 76%, while biomass generation increases to 14%, solar photovoltaics to 3%, hydropower to 1%, and wind to 6% [9, 25]. In 2020, Cuba generated just slightly less than 200 TJ of energy. These came from domestic sources such as biomass, oil, coal, hydro, as well as small contribution from renewable energy sources, such as solar and wind. At the same time, the energy supply or the consumption was over 400 TJ. Energy generation mix in Cuba has been dominated by the use of oil-derived fossil fuels, moderate use of biomass, and increasing focus on renewables (Fig. 1.1). Fossil fuel use has been dominant source of energy in Cuba and contributed to 85.6% of the total energy consumption in 2014. Additional 14% was generated from natural gas, 4% from biofuel, and 1% from renewables such as solar and wind. Cuba produces about 18,000 barrels per day of oil which satisfies about 40% of the needs and imports the rest. It is extracted offshore, along the coastline. The domestic oil is low quality, with high sulfur content and often causes power plant failures as well as air emission. Cuba also produces just over 40 billion cubic feet of natural gas. Based on the country’s plan for 2030, it is expected that the renewables will contribute with 24% to the energy mix, 6% from wind, 3% from solar PV, 14% from biomass, and 1% from hydropower. In 3 years, from 2014 to 2017, the electricity from renewables increased from 1% to 4%.

Chapter 2

Energy Generation and Consumption

Abstract  In this chapter, the most important present energy generation technologies for Cuba have been examined. These include fossil fuels such as coal and oil. The fundamentals of these technologies are presented in a form of brief tutorial that would help a reader with limited technical background gain essential knowledge and develop criteria for evaluating the energy structure of Cuba. Global current generation capacity, trends, and reserves for coal and oil have been discussed in order to better understand the planning process and energy system prospects for Cuba. Keywords  Fossil fuels · Fossil fuel origins · Fossil fuel reserves · Coal origins · Coal exploitation · Coal emissions · Oil origins · Oil exploitation · Natural gas Energy is required to sustain life. It is primarily obtained by burning fossil fuels, a process that emits harmful greenhouse gases and has devastating effects on the environment and life on earth. In addition, fossil fuel reserves are limited and the world would run out of fossil fuel such as natural gas and coal. Energy is required to maintain life on earth, and it is mainly used in form of heat and electricity. Primary energy is original energy, for example, energy of the Sun or chemical energy stored in crude oil. Final energy reaches the end user and includes electricity, steam, gas, or heated water. Effective energy is doing the required work, e.g., spinning the washing machine or radiating heat. Coal, oil, and natural gas, commonly defined as fossil fuels, are the most important sources of energy and the world depends on them. These fuels were formed many hundreds of thousands or millions of years ago and are biological materials that have acquired concentrated chemical energy through decomposition of living matter, plants and animals, under heat and pressure. The fossil fuel reserves that we are using now were formed millions of years ago, but they are not going to be replenished for another hundreds of thousands of years. Once the present reserves are used, the fossil fuels will be exhausted. As the reserves get depleted, the price of fossil fuels will increase to the point where they would no longer be competitive with other resources such as solar, wind, and biomass. The amount of reserves of fossil fuels is the critical question for the energy future of the world. It has been © The Author(s), under exclusive license to Springer Nature Switzerland AG 2023 S. Petrovic, Renewable Energy in Cuba, SpringerBriefs in Energy, https://doi.org/10.1007/978-3-031-37473-9_2

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established that the amount of fossil fuels increases after the discovery and reaches a peak after which the reserve gradually decreases until it is exhausted. This is known as a Hubbert’s Peak after the geophysicist M. King Hubbert. Fossil fuels emit harmful emissions to the environment, and they will run out one day. Although fossil fuels are still not depleted, their supplies are limited, crude oil prices are unstable, recovery costs are increasing, reserves are concentrated in a few regions of the world and not equitably distributed, and, at the same time, the world population grows steadily and requires more energy. All this and the perils of harmful emission from burning fossil fuels suggest that ways must be found to replace fossil fuels.

Coal Coal has been used for at least a few thousand years. It was the driving force for the industrial revolution, fueling steam engines that supplied power to factories and homes. The energy in coal is stored chemical energy from decomposed plants that lived hundreds of millions of years ago when earth was covered with swampy forest areas. Buried under the layers of dirt and water, the heat and pressure created chemical reactors that resulted, over the thousands of years, in coal. The amount of energy in coal depends on its composition, which depends on the age of coal. Anthracite has the highest carbon content, up to 98% and heat value of 15,000 BTUs per pound (heat value is 28 GJ/t). Bituminous coal has 45–85% carbon content and 10,000–15,000 BTUs/lbs., subbituminous coal has 35–45% carbon and heat value of up to 13,000 BTUs, while lignite has the lowest carbon content of 25–35% and heat content of up to 8000 BTUs per pound (roughly 18 GJ/t). About 500 metric tons of coal are used every year globally. The reserves of coal, at the present consumption worldwide, are about 110 years. The largest reserves are in the USA, Russia, China, and India. Cuba has no reported coal reserves, but the country consumes 2066 metric tons every year, all from imports [26]. Coal is mainly used to produce steam and generate electricity in power stations. Currently, about one third of the of the electricity in the world is generated by coal. A quick calculation shows that 2100 Mtoe (1 ton of oil equivalent = 42 Gj) or 19 EJ of energy in form of electricity is obtained from 59 EJ of coal input, which makes its 33% conversion efficiency. Besides uses to generate steam, coal is used for industrial applications such as smelting of iron ore, and 600–800  kg of a coal derivative coke is used to produce one ton of steel. About two thirds of the world’s steel is produced this way. Coal is mined from the ground by surface or deep mining. Surface mining is considered when coal is less than 70 m deep and large machines remove the topsoil to expose coal. Deep mining obtains coal from large depths, sometimes more than 300 m.

Oil and Natural Gas

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Coal is very impure fuel and its burning results in emission of CO2, SO2, and NOx, carcinogenic and mutagenic substances, and sometimes radioactive. These gases form smog and acid rain and/or contribute to global temperature increase. In addition, coal ash which is the product of burning coal contains numerous impurities such as mercury, sulfur, radioactive uranium and thorium, silicon, iron, calcium, and others. For instance, burning coal to produce 500 MW produces yearly emission of: • • • • • • • •

3,700,000 tons CO2 10,000 tons SO2 10,200 tons NOx 720 tons CO 220 tons VOCs 77 kg mercury 102 kg arsenic 52 kg lead.

Coal is used to produce steam in boilers, which flows into a turbine and spins a generator to produce electricity. There are several types of boilers, and the most advanced is the pulverized bed boiler, where very small particles of coal are fed into the burner for an efficient process. Coal can also be converted to liquid fuels, hydrogen, and other chemicals, while at the same time CO2 is captured. These processes increase the ration of H/C (hydrogen to carbon) and improve the value of coal. Coal liquefaction, for example, takes place at 370–470 °C and pressures of 50–300 bar (735–4400 psig) by reacting coal with a solvent and producing liquid fuel. Coal can also be gasified to yield hydrogen and methane gas, along with carbon dioxide.

Oil and Natural Gas Cuba produced an estimated 42,000 barrels per day (bbl/d) in 2023, which represents a decline from previous years and significant decrease from the maximum of 52,000 barrels per day. At the same time, Cuba consumes 172,000  bl/d. Cuba imports most of its oil supply from Venezuela, which provides crude oil at a heavily subsidized rate under a 2000 energy agreement. Cuba has 124 million barrels of proven crude oil reserves, which yet have to be exploited. Petroleum products are fuels made from crude oil and hydrocarbons contained in natural gas. Petroleum is formed from decomposition of plants and animals buried under layers of mud for several millions of years. Under the conditions of temperature and pressure, transformation to petroleum took place in source rock. From source rock, the petroleum was transferred into reservoirs under the impermeable top rock, called caprock. Petroleum must be first found and then extracted from the underground reservoirs. First, a gravimetric survey is performed searching for reservoirs. Next, seismic waves are generated and geophone is used to locate the petroleum reservoir.

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The final confirmation of existence of petroleum in the reservoir is obtained through drilling. The exploration is speculative and less than 15% of all wells results in actual oil. Crude oil is refined (in refineries) through the process of fractional distillation, whereby the components are separated based on different boiling points. Hydrocarbons with up to 5 carbon atoms in the chain are gases at room temperature and pressure, gasoline used as a motor fuel has 5–12 carbon atoms, kerosine has 12–18 carbon atoms, lubricants have more than 16 carbon atoms, paraffins have more than 20, and asphalt has more than 36 carbon atoms. One barrel (42 gallons) of crude oil yields 19.5 gallons of gasoline, 9.2 gallons of fuel oil, 4.1 gallons of jet fuel, 2.3 gallons of asphalt, 0.2 gallons of kerosene, 0.5 gallons of lubricants, and 6.2 gallons of other petrochemical products. Global oil production is around 90 millions barrels per day. Global production of natural gas in 2021 was 4 trillion cubic meters. Natural gas originates, similarly to crude oil, from the remains of plants and animals, in the processes under heat and pressure, and over time of millions of years. By composition, natural gas is methane, CH4. After extracting natural gas, other gases, the impurities such as ethane, propane, butane, and sulfur, are removed. After purification, clean natural gas is transported to the storage facilities or point of use through a network of pipelines. Natural gas is the cleanest of all fossil fuels. Its reserves are estimated at around 53 years.

Chapter 3

Renewable Energy Sources

Abstract  This central chapter of the text examines renewable energy technologies such as solar hydropower, solar photovoltaics, wind, bioenergy, solar thermal, geothermal, and ocean energy. Fundamentals of each technology are presented for readers with limited technical knowledge and applications of these technologies in Cuba are discussed. Current capacities, short- and long-term plans, and resource potentials for Cuba are reviewed. The contributions of each of these technologies for the future energy generation composition have been examined based on country’s geographical location and available resources. Keywords  Hydropower · Solar thermal · Solar photovoltaics · Biomass · Biofuels · Geothermal · Ocean energy · Cuba resource potential (a) Hydropower According to data from the Ministry of Energy and Mines, there are 162 hydroelectric power plants in Cuba and their total installed power is 71.9  MW.  From this number, 128 are small hydroelectric power plants providing power to homes and objects. While some countries derive a significant percentage of their electric power from hydropower, Cuba has no major rivers and gets only 1% of the total energy from 162 hydropower plants with the total capacity of 71.9 MW, which in 2019 generated 0.06 TWh. Cuba’s theoretical hydroelectric capacity is estimated to be 650 MW for large hydro and 135 MW for small hydro. Because most of the potential larger sites are located within naturally sensitive areas, the new developments will focus on small hydro projects. The small hydro has theoretical potential of 135 MW from which 56  MW is deemed economical and will be developed by constructing 74 small hydropower plants that will generate 274 GWh per year, nearly doubling the country’s current hydropower capacity. The investment for $30  M US for 34 of these hydropower plants with future capacity of 14.6 MW came from Arab Economic Development fund and also includes construction of substations and 75  km of transmission lines. © The Author(s), under exclusive license to Springer Nature Switzerland AG 2023 S. Petrovic, Renewable Energy in Cuba, SpringerBriefs in Energy, https://doi.org/10.1007/978-3-031-37473-9_3

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Hydroelectric power is the most important renewable energy technology, and it generates approximately 11% of the world electricity and 6% of the world’s energy, based on a 2019 data. Hydroelectricity makes about 90% of all renewables and 60% of all energy generated by renewables. Hydropower requires geographical conditions of the terrain to ensure creations of large water dams, from which water release with a significant flow and water head can be accomplished. The origin of hydropower is in solar power, which heats Earth’s oceans and evaporates 0.98 m3 of water from every m2 on earth, making the total evaporation from earth of over 500,000 km3 of water per year. The thermal energy imparted to water molecules raises them into the atmosphere. Upon cooling down the water vapor precipitates back on earth, some 78% precipitates over the oceans, while the remaining 22% precipitate on the ground at different elevations and still retain the potential energy based on its weight and elevation. Eventually, the water at higher elevation terrain flows back to the ocean level through rivers and streams, from lakes and glaciers. The overall process is called the water cycle. As the waters from higher elevations flow down toward the ocean level, turbines are installed in their path to transform kinetic energy into mechanical energy and to generate electricity in generators. The global installed hydropower capacity is 1360 gigawatts (GW) in 2021. This is 1.9% increase from 2020. It is estimated that worldwide, a yearly increase of more than 2% in available hydropower must be added as a contribution to reversing the climate change. From the available installed capacity, in 2021, 4.327 TWh of electricity was produced. This was lower than in the previous year and the first time in two decades that the amount of electricity decreased despite increased capacity because of droughts. The importance of hydroelectric power and the potential for further global increase can be put in the context with the estimate of the theoretical global capacity of approximately 52 PWh/year. A study of hydropower potential for over 11 million locations by analyzing slopes and discharge of each river in the world shows that hydropower could contribute 33% of the total global energy demand. Modern hydroelectric power plants come in various sizes; the smallest may have only a few hundred watts to almost 22.5 GW (Three Gorges Dam Yangtze River in China). The plants are classified based on the effective “head” of water (low, medium, and high), the type of turbine (impact or reaction), the capacity, or the type of dam. Hoover Dam and Grand Coulee are impoundment involving dams type of dam. Niagara Falls is a run-of-river system. A conventional hydropower plant comprises a reservoir for storing water, a penstock for carrying water to the turbine, a turbine powered by the force of the water on its blades, and a generator driven by the turbine for generating electricity. There are two types of turbines: impulse and reaction turbines. Impulse turbines have nozzles through which the water jets are imposed on curved blades and water pressure spins the turbines. These turbines are suitable for high water “head” and low water flow. The velocity of water jets can be controlled. There are three types of impulse turbines: Pelton, Crossflow, and Turgo turbine. Reaction turbines are used when the water “head” is low and water flow is high. Both the pressure and velocity of water are used to generate kinetic energy of the

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13

turbine. There are two types: Francis turbine is used for medium water “head” and flow, and Kaplan turbine is used for low water “head” and high water flow. The blades for reaction turbines have flat and slightly angled or curved blades. Despite numerous benefits, hydroelectric power has negative impact as well. Dams can collapse, silt accumulation reduces reservoir volume and affects flood control, population can be displaced (e.g., Three Gorges Dam displaced 1 million people), cultures can be destroyed, destruction of the ecosystem (e.g., salmon ecosystem), and increased methane gas production, which is a very potent greenhouse gas. (b) Wind As of 2019, Cuba had only four experimentally constructed wind farms with a capacity of 11.2 MW and generating 21 GWh annually, with plans to add 13 more [1, 2, 4]. Large and modern equipment for the wind farms posed challenges and thus required experimental developments and the implementation of testing sites for the farms [3]. Two major wind farm projects are La Herradura 1 and 2 encompassing a complex with a total of 54 turbines operating at 1.2 and 2.4 MW [3]. Total global wind power capacity was 837 GW in 2021. By 2026, it is expected that new 557 GW of capacity will be added. This means that more than 110 GW of new installations must be added each year, surpassing the current growth in 2021 of 96 GW. Globally, the electricity generation from wind power has an enormous potential to provide full electricity demand of the world. As in the case of other renewable energy technologies, energy generation from wind power has only limited predictability, as the wind depends on atmospheric and weather changes. In addition, only a part of global wind potential can be actually recovered in economically reasonable manner. The wind classification spans wind densities of about 0.05 kW/m2 in case of a mild breeze to 25  kW/m2 in case of hurricanes. The resource availability for generating wind power depends on the wind conditions, and only a small part of the overall wind potential is economically feasible. Historically, wind-powered devices have been used to mill grain and for pumping water as early as 3000 years ago. Windmills were also used in Europe, and the evidence exists from the twelfth century. In North America, windmills were used in the nineteenth century. The real breakthrough technology innovation began when the wind technology began to be used for electricity production in the late twentieth century. Electricity is produced by building wind turbines and placing them in the areas of wind speeds from the minimum required for electricity generation to maximum wind speeds that do not create structural damage to turbines. A wind turbine placed in the path of wind converts the kinetic energy of air generated by wind to rotational energy of the rotor used in a generator to produce electrical energy. The wind speeds useful for operation and generation of electricity are from cut-in wind speed of 3 and 5 m/s and up to a maximum of 25 m/s when the turbines stop spinning.

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The wind energy entering the cross-sectional area of the blades of the turbine cannot be captured entirely by transferring it to the blades because a portion of that energy is carried by the air that exits the turbine at a lower speed. If there were no air exiting the turbine, the blades would stop rotating. The component of wind energy transferred to the blades is converted into electricity, and the power generated depends on the wind speed, density of air, and the area that the rotor covers, and it can be expressed by the following formula:



PT 

1 dm 2 v1  v2 2 2 dt





(3.1)

where m is the wind mass, t is the time, so dm/dt is the mass flow, and V is the wind speed (before and after exiting the turbine). The power obtained can also be expressed using the wind speed and cross-­ sectional area that the blades cover:



PT 

1  A  v1  v2  v12  v2 2 4





(3.2)

A is the area of a circle made by rotor blades of the radius, r; and ρ is the density of air. The power of wind turbines is expressed with the power coefficient, CP, the ratio of the power generated by a turbine, PT, to the power in wind, PI: CP =

PT . PI

(3.3)

By combining Eqs. 3.2 and 3.3, the power coefficient of a turbine is expressed as: CP 

 v1  v2   v12  v2 2  2 v13

.

(3.4)

It can be seen from the equation that the power coefficient does not depend on the density of air, the cross-section, or the size of the blades. Equation 3.4 also shows that the power coefficient of a turbine is only dependent on the wind speed before and after the rotor an independent of the density of air and the cross-sectional area or the size of the blades. Most importantly, the maximum power coefficient, or efficiency limit called Betz limit, for any turbine is 0.593. Betz’s law states that a maximum 59.3% of the wind power can be converted into mechanical power. It can also be derived from the Betz limit that the maximum power is obtained from a turbine when the initial speed is reduced to roughly one third. Furthermore, the Betz limit shows, similarly to the Carnot efficiency, that there is a limit of how much of one form of energy can be converted into the other form of energy.

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15

Examination of the wind turbine power curve shows the “cut-in” wind speed, the minimum speed at which power can be produced, then increase until nominal power is reached, and finally the “cut-out” wind speed, at which it is no longer safe to have the turbine blades spin. A wind turbine would produce its nominal power when the nominal wind speed is reached, typically 2.5–4.5 m/s; and higher wind speeds do not produce higher power output, so the turbine blade rotation is slowed down to prevent mechanical damage. This typically happens at wind speeds in the excess of 20 m/s. Once the wind power curve is known, the energy can be calculated using the wind speed frequency distribution at that site. This means the number of hours per year that a wind of a certain speed blows. From the wind turbine power and the number of hours the wind of a certain speed is available, the total energy per year can be obtained by adding all energies at different wind speeds. Besides this theoretical prediction of total yearly energy, the losses must be considered. These include transmission losses, turbine down times, and reliability. The total energy can be expressed using Eq. 3.5:

E  kWh   K  vm3  A  T



(3.5)

where vm = annual mean wind speed in m/s, A = swept area of the rotor in m2, and T is the number of turbines. K = 3.2 is a factor based on typical turbine performance. If we know the amount of electricity produced for each wind speed and their frequency distribution, we can construct a theoretical graph of the electricity production for each wind speed. The maximum energy production is not at the same wind speed as maximum frequency. It can also be observed from the graph in the Fig. 3.1 that no electricity is generated for wind speeds below approximately 3 m/s. Wind speeds in Cuba average 5.7 m/s at an altitude of 80 m [9]. The country has an estimated wind power potential of 2550 MW but plans to expand to only 633 MW by 2030 [1]. In 2019, there were plans to build 13 wind farms along the northern coast [1]. As of 2019, Cuba had only four experimentally constructed wind farms with a capacity of 11.2 MW and generating 21 GWh annually, with plans to add 13 more [1, 2, 4]. Large and modern equipment for the wind farms posed challenges and thus required experimental developments and the implementation of testing sites for the farms [3]. Two major wind farm projects are La Herradura 1 and 2, encompassing a complex with a total of 54 turbines operating at 1.2 and 2.4  MW [3]. The La Herradura complex also contains a substation that is larger, more complex, and more modern compared to the national energy system [3]. Before any new wind farm project begins construction, there is a testing phase during which the wind resources in the area are evaluated, including speed and altitude, in order to select the proper equipment. Special consideration must be taken for the climate and strong winds during hurricane season [3].

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Electricity production, MWh/y

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500 400 300 200 100 0

0

5

10

15

20

Wind speed, m/s Fig. 3.1  Graph of electricity production in MWh per year for each wind speed for a hypothetical site

(c) Ocean Energy For an island nation such as Cuba, the prospects of ocean power generation would seem obvious. Oceans and seas around Cuba can be a source of large component of renewable energy to provide the country’s electricity needs. This energy would largely contribute to lowering carbon footprint and add to “blue economy” that promotes sustainable uses of ocean resources and coasts through improved economic growth and ecosystem and through advancements in shipping, cooling, and water desalination. Ocean power can be generated without any harmful emissions and does not take any land. Despite great potential, ocean power worldwide is still underutilized. The main reasons include low-energy conversion efficiency and relatively large and complex investment. The four ocean energy technologies include wave energy, tidal energy, ocean thermal energy conversion (OCTC), and energy from the differences in salinity. The theoretical potential for electricity generation from ocean energy is enormous and exceeds the total global energy demand. However, this potential must be economically justifiable, and at present the cost is still prohibitive for most situations. It is, therefore, necessary to improve the performance and decrease the cost through innovations. The global annual resource potential of ocean energy is estimated to at least 20,000 TWh of electricity, which, if exploited, could supply the total global demand for electricity. Some estimates of the ocean energy potential go as high as 80,000 TWh. The resource potential of ocean energy, in particular the ocean wave energy, varies based on wind power and frequency, and it is the highest in the areas with strong winds. The coastlines with the highest potential for wave energy are along the

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17

Fig. 3.2  The world map depicting the most favorable regions for harvesting wave power across the world [5]

continental shelf break between the coastline and the continental slope. The best locations in the world are those where low amplitude waves from deep seas turn into high amplitude shallow water waves. In addition, a location must have favorable wind speed and frequency, such as southeast trade winds, the westerlies, and the northwest trade winds dominant in the Caribbean Sea where Cuba is located. Globally, it is considered that the best areas for ocean wave power electricity generation are the Eastern Coast of Brazil, Madagascar’s Eastern Coast, and the Wild Coast at Eastern Cape of South Africa. These are very long, several hundred kilometers and therefore favorable for wave energy utilization. The distribution of favorable regions in worldwide is depicted in the world map in Fig. 3.2. By examination of the map, it appears that Cuba might be benefiting from the Northeast Trade Winds in the Caribbean. Cuba has explored possibilities for ocean energy exploitation including wave energy, energy from currents, and OTEC. There are some limited studies showing that Cuba has limited potential for utilizing wave energy including unconfirmed reports that Cuba has installed buoys, probably of the linear energy generation buoys with the annual capacity for 20,000 kWh at a cost of 30,000  USD.  However, a greater resource potential appears to be available from tidal currents that can be up over 5 km/h. There is no or scarce information regarding any projects to exploit ocean energy in Cuba. It appears that Cuba does not have and is not planning large-scale projects involving ocean energy. The origins of wave energy are from solar energy, which generates heating of air masses, creating wind, which then interacts with water to produce waves. During this interaction the energy of moving air is transferred to water, while the force, which is at first tangential to the water, forms crests and troughs. As the waves grow, more energy is transferred from air to water. While the power output from the wind and the Sun is expressed in W/m2, for example, the wave power is expressed per unit

18

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length of the coastline and can be on average around 50 kW/m. The solar power density is 1 kW/m2 and wind power for moderate wind is 5 kW/m2. A wave is characterized by several properties, the amplitude, the crest, the through, the height, the frequency, the wavelength, and the phase. The principle of operation of wave power conversion relies on waves pushing the air upward in a column and turning the air turbine, converting thereby wave energy to first to mechanical and then further to make electricity. The technology is known as oscillating water column. A different principle of operation is used in TAPCHAN (tapered channel) where waves fill an upper reservoir, giving potential energy to water, which is then released through a hydroelectric turbine, generating electricity. The concern with these wave energy exploitation technologies is an ecological impact along the coastline where the facilities are built. The length of the coastline impacted depends on the wave energy density and the amount of power required. In general, the wave energy utilization requires more area, i.e., coastline, than the proportional area used by a gas or oil power plants. Consequently, the justification for building a wave energy is that plant must show lower environmental impact than fossil fuel power plants. In terms of general environmental impact, ocean wave technologies are similar to hydropower plants, where the largest impact on biodiversity is at the boundaries between land and water, in this case the coastline where bio life utilizes the resources from both land and ocean. Cuba is particularly sensitive to ecological impact of energy technologies which is evident from the policy statements and long-term plans. The ocean power exploitation offshore has arguably less ecological impact because of the lower density of fauna in the open oceans and further away from the coastline. In addition, more favorable conditions for utilizing ocean energy exist in deeper water depths. The most known technology for generating power from waves is a device called Pelamis or “sea snake.” It is anchored to the ocean floor, with a generator comprising cylinders filled with hydraulic fluid, positioned perpendicular to incoming waves. The movement of the cylinders caused by waves creates movement of the hydraulic fluid that drives an electrical generator. Pelamis units are very large, typically over 100 m long and can produce up to 250 kW per cylinder. Another type of wave generation device is a linear wave generation buoy, which comprises a shaft anchored to the ocean floor and a free-floating cylinder attached to the shaft. The principle of operation is based on magnetic linear generation using an electrical coil. When the waves lift the coil, electricity is generated through the shaft magnet. These devices are usually placed at around 30 meters from the seabed and a few kilometers from the shore. Tidal power has its origin in the gravitational forces between the moon and the Sun, as well as centrifugal forces from the rotation of the earth. The large bodies of water such as oceans and seas are attracted by these forces and move, i.e., rise and fall, in regular intervals of 12 hours and 25 minutes. This is one half of a lunar day. The moon’s gravitational force affects, to a much greater degree, the waters on the near side of the earth. There are two bulges that water masses exhibit: one on the near side (toward the moon) because of the gravitational forces and the other on the far side toward the moon because of the centripetal acceleration because of rotation

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19

of the earth and the moon. So, the tides in a way follow the moon’s rotation around the earth. Consequently, there are two tides each day on every shore on earth. The power can be extracted from the tides by utilizing shallow waters near the shores to create a significant rise of up to 3 m. And, if the topography is characterized by a narrow passage or a tapered estuary, the tides can be even 15 m. The energy extraction is then accomplished by placing low dams (or barrages) across the entrance to estuaries. The most known tidal barrages are Severn bore in England and Hooghly in India, with tidal rises of 10–15 m. After the rise, water gains potential energy, which is released through a hydroelectric turbine, producing electricity. For an economic justification, the tidal variation must create a large water head between the high and low tides. As in hydropower plants, the power depends on the water head, the volume of water, gravitational acceleration, and efficiency factor (Eq. 3.5):

P    1000  Q  g  H E

(3.5)

The global built capacity for tidal power is over 500 MW, mainly due to two largest power plants, the Rance in France and Sihwa Lake in South Korea, which produce combined 1000 GWh of electricity. There are three schemes to generate power from a tidal barrage: low-head turbines, tidal stream turbines, and combined type. The ocean thermal energy conversion (OTEC) relies on the temperature gradient between the water at the ocean surfaces and water at a depth of about 1 km. The minimum temperature difference for practical energy generation is 20 ° C, which can be utilized in tropical and subtropical areas. The warmer water is used to vaporize a working fluid, forming vapor that expands and drives a turbine generator, generating electricity. The vapor then exchanges heat with the lower temperature water and is condensed. The best efficiencies of OTEC systems are roughly 7%. However, we keep in mind that world’s oceans contain 4000 times more energy than the global demand and even at very low efficiency large bodies of water can generate significant portion of the demand. The global potential for OTEC is the largest in the regions along the equator, as shown in Fig. 3.3. There are two types of OTEC power plants: closed and open cycle. The plants can be attached to the sea floor or placed on moving ships. In closed scheme the working fluid, usually ammonia, is vaporized using warm surface water, and after powering the turbine generator, the vapor is condensed using the cold water at a depth. In the open cycle type, the working fluid is water. In conclusion, Cuba has some potential for exploiting ocean energy, but there are very few records of actual projects or installed capacities, and visual observation of the coastline in many areas did not reveal any operations. (d) Biomass Cuba has installed generating capacity from biomass of 5870  MW and the total production capacity for electricity production of 1.76 billion kWh [24], which would be 2.7% of the country’s electricity production. The global capacity for using biomass to generate energy is reported to be nearly 150 GW in 2022. In 2016, biomass generated 56.5 EJ of primary energy or about

20

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Fig. 3.3  The global potential for OTEC technology [6]. Darker areas indicate higher potential for OTEC

70% of all renewable energy. In addition to vast availability, biomass use to generate energy is not intermittent and unpredictable as other renewable energy sources, which is an important advantage. The leading countries in using bioenergy are China with around 34 GW, followed by Brazil, the USA, and India. Cuba has an important part of its energy generated by biomass, and it uses 25 million metric tons annually (data from 2021), ranking it 91st in the world. The government’s energy plan for 2030 includes biomass capacity of 755 MW [7]. The first biomass plant with the capacity of 60 mW was built in Ciego de Avila, and its first boiler became operational in 2020 [8]. Additional 18 biomass power plants are expected to be built. Cuba has not been very aggressive in developing biofuels based on a concern that growing crop for biofuels may compromise the food crops. As a result, ethanol production, for example, did not increase at all between 1991 and 2016 and stayed at 1.81 thousand barrels per day [10]. In 2017, an industrial-scale biodiesel plant began operation in the Granma province [8]. The fuel is obtained from oil of the Jatropha curcas flowering plant, and the plant is expected to reduce the reliance on imported fuel by 26% [10]. Biomass has been used from the early history of mankind to produce heat and lighting. The types of biomasses included primarily wood in the ancient times, and then coal was used particularly used in large quantities since the beginning of the industrial revolution primarily for heating. Liquid fossil fuels such as kerosene were used lighting. The amount of traditional biomass used, or the energy produced from biomass, is impossible to accurately measure everywhere in the world. It is only roughly estimated that globally traditional biomass provides 10% of the energy and over 60% of the renewable energy. Only 10% of the biomass used is provided from new

3  Renewable Energy Sources

21

engineered biomass sources and processes, while the majority can be still described as simply burning wood and other biomass. Bioenergy is a the most used form of renewable energy in the world. Because of the nature of using biomass, for example, wood or animal dung, the quantities of heat or electricity from biomass are often underreported. Biomass is a term to describe organic materials, such as animal or plant materials, which can be used to generate energy by burning them to make heat. Or they can be used in combustion reaction that creates steam used in turbines to produce electricity. Biomass can also be converted through several process pathways to gaseous or liquid biofuels for transportation purposes. Biomass combustion to generate electricity or heat results in CO2 as a product of reaction, similar to burning of fossil fuels (coal, oil, or natural gas). However, the amount of emission is lower because of the lower amount of carbon present in biomass. Biomass, unlike fossil fuels, can be regenerated relatively fast. There are three types of biomasses: solid, liquid, and gaseous. Biomass forms biosphere, a layer on earth that is essential for maintaining the atmosphere and its perpetual regeneration is driven by the energy of the Sun. About 0.64% of the total 2000  kWh/m2 of solar radiation on earth is converted to chemical energy in the plants through the photosynthesis process, and this energy can theoretically be converted to heating or electricity. While it is evident that the global potential of biomass is enormous, it is very important to define the energy balance and demonstrate that the bioenergy is truly renewable. The main question is if the consumption of biomass, including its derivative biofuels, is less or equal to the rate of formation of new biomass from solar energy, through the process of photosynthesis. This would demonstrate if biomass can be considered truly renewable and environment friendly and if the CO2 emissions from utilizing biomass are less than generated in the natural processes of decay. Simply, bioenergy is sustainable and renewable form of energy if the utilization is equal to or less than the production of new biomass. To further explain the conceptual difference between using fossil fuels and biomass for energy generation, it is important to define that biomass is the organic material created in a recent past, from months to several years, while fossil fuels have been formed from biological materials millions of years ago. While both biomass and fossil fuels (coal, oil, natural gas) are chemical combinations of hydrogen and carbon, therefore called generally hydrocarbons, fossil fuels are not renewable on the timescale of importance for humankind while biomass is. It is also obvious to most readers that the reserves of fossil fuels that have been accumulating in the ground for millions of years are being nearly depleted in only a few hundred years. The distinction between renewable biomass and biomass from fossil fuels is in the age of the material. However, there are also materials that have partially decomposed, such as peat. Peat is a plant material that has not fully decayed in acidic and anaerobic conditions, and it is mainly wetland vegetation. Peat is not considered a material for bioenergy that is renewable because it would take hundreds of years to replenish.

3  Renewable Energy Sources

22

The biomass controversy regarding CO2 emission is a subject that needs to be carefully evaluated. The argument in favor of considering biomass explicates that CO2 is generated when biomass is converted, but the same amount of gas had been absorbed from the environment earlier in the photosynthesis reaction, which makes bioenergy carbon neutral. This is the case if the exploitation is rational and it doesn’t exceed the rate of regrowth, globally and locally. This argument extends as well to justify the use of biofuels, for example, ethanol or biodiesel instead of fossil fuels. Biomass burns in the presence of oxygen to produce thermal energy, which is then further converted to mechanical energy and to electricity. The oxidation of carbon and hydrogen containing materials creates CO2, H2O, and heat. The simplest hydrocarbon is methane or natural gas, which is oxidized to water or carbon dioxide, with the release of energy (Eq. 3.6):

CH 4  2O2  2H 2 O  CO2  Heat

(3.6)

The heat energy released to the surroundings is the difference between chemical energy of reactants and products. Methane and other hydrocarbons can also be oxidized in an electrochemical reaction used in fuel cells, and the energy will be released in form of electricity. Another group of organic compounds containing carbon, hydrogen, and oxygen is carbohydrate, such as sugar or glucose. Glucose oxidation also produces CO2, water, and heat (Eq. 3.7):

C6 H12 O6  6O2  6H 2 O  6CO2  Heat

(3.7)

The reverse reaction is between carbon dioxide and water, and it is an endothermic reaction requiring energy, which is provided by the photons of sunlight. The reaction is called photosynthesis reaction (Eq. 3.8):

6H 2 O  l   6CO2  g   C6 H12 O6  aq   6O2  g 



(3.8)

The reaction also needs a pigment, chlorophyll, which absorbs photons and enables the reaction. The energy content of selected carbohydrates and hydrocarbons is shown in Table 3.1. Table 3.1  Energy content of selected hydrocarbons and carbohydrates

Fuel source Natural gas (methane) Petroleum Coal Charcoal Dry wood Straw Green wood

Giga-Joules per ton (GJ/ton) 55 48 28 30 18 15 6

3  Renewable Energy Sources

23

The energy in crops varies based on type and conditions of farming. The efficiency of converting Sun’s energy to chemical energy in plants is very low, below 1%, and to generate significant amounts of energy, large areas of land are needed. There are two types of energy crops: forestry crops and agricultural crops. Forestry crops such as willow and hazel are used to generate heating and to produce steam that drives electric generators. These crops are fast-growing, and they are harvested every few years. The yields are roughly 10 tons per hectare. Agricultural crops are grown both for food and energy. Examples of agricultural crops that are used for dual purpose are sugar cane and rice. The bagasse from sugar cane is used for energy production, while starch and sugar are used for food or fermented into ethanol, which is used as an additive to gasoline. Through the process of transesterification, agricultural crops, such as canola, mustard, soybeans corn, and sunflower, can be also used to produce oil. Another type of biomass are the waste products such as residue, animal, and crop waste, as well as municipal solid waste. The forestry residues can be converted to biofuel; temperate crops, such as wheat, corn, and barley, can annually generate a billion tons of waste and are used to generate electricity and heat; and tropical crop waste, such as from rice and sugar cane, generate approximately same amount of energy as from temperate waste. For instance, the residue from sugar and ethanol production, called bagasse, can be burned to produce energy; and rice residues are converted to gas (i.e., gasification process), which is burned to produce energy. Animal wastes, such as manure or sewage, are usually used as fertilizers but also can produce methane gas, which is burned to generate power. Municipal solid waste (MCW) is used to produce low-energy content biogas in anaerobic decomposition reaction. All biomass is first prepared before it is used to generate energy. It starts with drying to remove moisture. Then it is shredded or grinded and densified by preparing pellets or briquettes. When prepared, biomass can be directly burned to generate heat or converted through thermochemical, chemical, or biological processes into biogas or biofuels, which are then used to generate heat, mechanical energy, or electricity. Cuba has its own specific type of biomass – the waste product from processing sugar and rice. These are called bagasse and marabou. While some countries secure significant portions of their overall energy from biomass, such as India (40%) and China (20%), in 2014, Cuba had less than 4% of total energy supplied from biomass. However, the country’s plan for 2030 calls for 14% total energy in the form of bioenergy, from which 755  MW would come from sugar cane biomass, 47  MW from cane biomass, and 27  MW from biogas [9]. Eighteen more biomass plants have been proposed, all in the vicinity of sugar mills. Two plants with combined capacity of 20 MW are under construction: one in the Matanzas province, and the other is in Villa Clara province [10], while a 50 MW plant was planned to be built in Artemisa province [10]. A map of Cuba’s biomass plants is shown in Fig. 3.4 [10]. The program started in 2020, and in one of the plants, over 2000 tons of marabou have been used to generate steam in a boiler and 1550 MWh of electricity [8]. The plant is expected to generate 122 t of steam per hour when fully operational and

24

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Fig. 3.4  Map showing the locations and sizes of biomass-fired power plants planned for construction in Cuba by the year 2030 [8]

provide 8  MW of power to run the sugar mill while the remaining power, about 50%, will be supplied to the electrical grid. At the full capacity, the plant will be processing over 2000 tons of bagasse every day. When fully functional, the biomass facility will substitute about 100,000 barrels of crude oil every year, which will in turn reduce emission of carbon dioxide by over 3000 tons. A waste biomass from rice processing can also be used to produce energy, and Cuba is building one such plant near Enrique Troncoso mill. The heat produced by the plant will be used in the drying process for rice, while a portion will be used to generate 2.4 MW of electricity [8]. (a) Solar Thermal At the time of writing this text, Cuba had 3.8 MW installed solar thermal capacity, all in form of over 10,000 rooftop solar water heaters. The 2030 Energy Plan does not specifically include any expansion of this capacity [11], but there are estimates that additional 200,000 square meters of rooftop panels will be installed for water heating. It was estimated about 15 years ago that 80% of Cuban population had hot water electrical heaters, which poses significant load on the electrical consumption, especially during the peak hours. As a result, introducing solar water heating has potential to reduce the consumption of electricity. The energy of the Sun can be converted to heat or electricity. On a global scale, solar heating provides significant portion of overall energy. Solar radiation originates

3  Renewable Energy Sources

25

in the core of the Sun where nuclear fusion reactions between the isotopes of hydrogen, deuterium, and tritium produce heavier helium atom (Eq. 3.9):

2 1

H  31 H  42 He  01 n

(3.9)

It can be calculated based on the famous Einstein’s equation, E = mc2, that enormous energy, 6 × 1014 J for every kg of H2, is released in nuclear fusion reactions as very tiny part of the total mass, 0.7%, on the left side of the equation is converted to energy. As over four million tons of hydrogen is consumed in this reaction per second, the total power output from the Sun is 3.9 × 1026 watts. The released energy is first conducted from the core of the Sun to the surface and from there emitted into the space in all directions. When a very small, 2 billionth part of the solar radiation arrives at the Earth’s atmosphere, its power density is 1367 W/m2, and after passing through the atmosphere it is attenuated to around 1 kW/m2 at the Earth’s surface. The electromagnetic radiation coming from the Sun is composed of a range of wavelengths, which depend on the temperature in the outer layers of the Sun from where the radiation emanates. Solar light of certain wavelengths is absorbed in the atmosphere, and the resultant intensity (i.e., flux of photons per surface area) at the Earth’s surface changes (Fig. 3.5). Humankind had intuitively developed methods to capture solar heat from the ancient times. The first evidence of using solar heat goes back thousands of years in Mesopotamia where smooth surface golden bowls were used to concentrate sunlight and start fires. In the sixteenth century, Leonardo Da Vinci worked on the design and

Fig. 3.5  The spectrum of solar irradiance, i.e., the power density of solar radiation as a function of wavelength

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Fig. 3.6  Solar thermal collector classification

made models of a 6-km-diameter concave mirror on the side of a mountain to capture high temperature in materials in the focal point some 4 m high. Solar thermal energy coming from the Sun can be converted to heat using solar thermal collectors and used to make steam, which is used to generate electricity. Solar thermal global capacity has been declining for several years, but it grew by 3% in 2021 and was 522 GWth. There are two basic categories of solar thermal collectors, active and passive, and each category has several variations (Fig. 3.6). Solar thermal systems are used for space heating and cooling, for district heating, and to heat domestic hot water. Globally, solar thermal can meet 60–90% of the hot water demand and 25–40% of the heating demand. However, the most significant energy generation is accomplished by generating process heat and then electricity. A solar thermal system generates approximately 500–1000  kWh/m2/year, has expected lifetime of 20 years, and has potential to replace 15–30 gallons of crude oil per m2 of panel surface. The energy generated has cost of $0.04–0.10/kWh. Passive solar thermal systems include design of buildings to efficiently absorb heat and maintain it. The specific methods used comprise greenhouses, Trombe walls, and daylighting. Greenhouse captures heat, which can be subsequently used for building ventilation systems, accomplishing energy savings. A Trombe wall is constructed from a large thermal mass, a glass, and an air gap. The heat is stored during the day in the thermal wall and slowly released into the building. Window glazing prevents radiated heat escape from the building.

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27

Active solar heat systems heat a fluid, such as water, pump it to tanks, and use it to heat swimming pools, for domestic hot water, or to distribute heat in buildings. The systems can be non-concentrating and concentrating. Non-concentrating systems include flat plate collectors and evacuated tube collectors. Concentrating systems are parabolic trough collector, linear Fresnel collector, central receiver systems with dish collector, and central receiver system with distributed reflectors. In a parabolic trough, solar energy is focused onto a tube carrying a fluid and heating the fluid as high as 400  °C.  The heating fluid then flows through a heat exchanger, heating water to a superheated steam, driving conventional turbine generator to produce electricity. The efficiency of energy conversion from solar energy to electricity is approximately 10%. Parabolic troughs can be positioned on Sun-tracking stages to follow the Sun movement and increase the power throughout the day. Tracking systems can be one- or two-axis. Power tower is a large solar thermal power plant comprising thousands of tracking mirrors called heliostats, which concentrate sunlight on a central receiver positioned on a tower. The heat generated in the receiver is used to heat water and produce steam for a turbine. Solar chimney is a tall tower, built on the top of a greenhouse, that allows hot air, heated by the Sun, to be collected inside a base and create flow of air toward large roof based on temperature difference. This enables inserting a wind turbine into the base and generating electricity. Efficiency of the solar chimney of up to 25% is possible and depends on the height of the tower. The wind turbine continues operating at night as well because the temperature difference is maintained, so the air flow continues. Heat produced with a range of solar thermal technologies can be stored for a long time in molten salts. Heat storage in molten salts, which are readily available, nonflammable, and cheap, has been long associated with solar thermal technologies on a large scale, in hundreds of MW, and there were numerous examples of such projects. The salts are typically heated during the day to over 500 °C, and heat is released during the night. An example of a power plant including a solar thermal tower and heliostats using molten salt heat storage is shown in the Fig. 3.7. (b) Solar PV Solar PV (photovoltaic) technology converts solar energy directly to electricity. Global solar PV capacity in 2021 was 940 GW and was ranked eighth among all energy generation technologies with 1% contribution to global energy. The solar resource is many thousand times larger than the present energy demand on Earth. While there are other methods to capture and convert solar energy to usable energy, heat, mechanical energy, or electricity, solar photovoltaic systems are the most appealing due to its simplicity, no emissions, large range of sizes, minimal maintenance, cost advantages for remote locations, and long lifetime. Cuba currently has 84 solar photovoltaic parks and 227 MW capacity, which is 2.37% of daily electricity produced [14]. In 5 years, from 2017, Cuba has acquired over 60 new solar PV parks and increased its total capacity from 37 to 227 MW. Despite declared capacity, most of the plants are underperforming, and the

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Fig. 3.7  Molten salt thermal energy storage [12]

analysis that was conducted shows that most of the plants require revision to improve the efficiency. Distributed solar PV is also receiving attention and it is intended to install 10,000 solar panels for homes and schools. By the year 2030 and a milestone goal, Cuba expects to operate 191 solar parks and reach a capacity of 700 MW, which will produce 1050 GWh per year. It is projected that this would replace 240 million tons of oil. The plans are underway with 17 more solar PV parks being designed to deliver 100 MW of capacity and located in Matanzas, Artemisa, Mayabeque, and Pinar del Rio. The country is following a sound planning that includes considerations for locations not interfering with the areas suitable for farming and being in the proximity of transmission and distribution lines, and mounting that can withstand winds of 150 km/h winds, known to occasionally hit Cuba. The main component of a PV system is a PV (photovoltaic) module, which comprises several single solid-state photovoltaic cells, usually 36. Besides the module, a PV system includes inverters, charge controllers if battery storage is included, wire, switches, disconnects, mounts, and other components. There are two types of PV systems: standalone and grid connected. The effectiveness of using solar PV depends on the amount of solar radiation available in a year, i.e., irradiation or insolation expressed in Wh/m2. Cuba has high solar potential and gets a large amount of solar irradiance with an average of 223.8 W/m2 and 5.4 kWh/m2 daily.

3  Renewable Energy Sources

29

Single PV solar cells are made mainly from semiconductor silicon. The two main technologies use monocrystalline and polycrystalline silicon, which have more than 90% of the market. Monocrystalline silicon solar cells are the most efficient of all, but also expensive, while polycrystalline cells are dominating the market because of good efficiencies and lower cost than monocrystalline. The first step in fabrication of crystalline silicon solar cells is purification of the raw material sand. After the impurities are removed, silicon is solar cell grade pure and polycrystalline. From that point, polycrystalline and crystalline cells are manufactured in different ways. Mono or single-crystal silicon cells are fabricated by melting the polysilicon material in a quartz crucible at high temperature and slowly performing crystallization on a single crystal seed, yielding a large, single crystal cylinder called an ingot, which is subsequently cut into round wafers. Next, wafers are processed using processes known in the semiconductor processing industry to create a pn-junction, a material property inside the cell that is necessary for converting solar electromagnetic energy into electrical current. Single cells are further processed by adding metallic contacts, antireflection layers, and other properties and fabricated into completed cells. Finally, single cells are assembled into modules (or panels), electrically connected, usually in series to increase voltage, protected by encapsulation, tested, and made ready for use. The module size depends on the size of single cells and their number and ranges from a few watts to about 500 W. Polycrystalline silicon solar cells are directly processed after silicon purification by melting it in a crucible and allowing it to solidify, without creating completely uniform crystalline structure. A solid block of polycrystalline silicon is first cut into so-called bricks and then into square wafers. From there, the processing is very similar to monocrystalline silicon solar cells. First a pn-junction is formed inside the cells, metallic contacts, and antireflection coating is added, and single cells are encapsulated into modules. Polycrystalline silicon solar cells and modules have a few percent lower efficiency for converting solar energy into electricity than monocrystalline because of the disrupted crystalline structure and presence of so-called grain boundaries between the areas of crystallinity, which contribute to lower efficiency (Fig. 3.8).

Fig. 3.8  Schematics of the different crystalline structures of silicon, from left, monocrystalline, polycrystalline, and amorphous

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The crystallinity determines the material efficiency for converting solar light photons to electricity. When photons of light penetrate the solar cell, they travel until they collide with atoms of silicon and generate an electron-hole pair. The negatively charged electrons and positively charged holes are drawn in the opposite directions by the pn-junction. The boundary between two types of silicon material, n-type silicon and p-type silicon, is called a pn-junction and has properties that create an electrical field, which separates the two charges. The two types of silicon are created through doping of intrinsic silicon with phosphorous for n-type and boron for p-type. When electrons created by photons (i.e., light) travel toward the top contacts, they experience less resistance and better chance to pass through an ordered single crystal cell. In the polycrystalline silicon, there is a greater probability that electrons will collide at the phase boundary with other atoms and recombine without generating electrical current. The losses are inversely proportional to the degree of crystallinity of material. The third type of silicon, the amorphous silicon, is prepared into solar cells in a different manner, by chemical vapor deposition of a thin film from silane gas. The efficiency of amorphous silicon cells is significantly lower than for crystalline cells, but amorphous technology is considerably cheaper. Because of the thin design, these cells are flexible and lightweight. They are made by depositing thin films on a flexible substrate. The other types of thin film solar cells are made from a compound semiconductor gallium arsenide, CuInSe2, CuInGaSe, and CdTe. Additional types of solar cells include electrochemical (dye sensitized) solar cells, polymer solar cells, and nanocrystalline solar cells. To better understand the construction of a silicon solar cell, a schematic of a cross-section of a cell is revealing several layers, some thicker than the others, and it should be noted that the solar light enters the cell from the top (Fig. 3.9). The “pyramid-type” layers on the top side of the cell reveal the most efficient design used to minimize the reflection of solar light from the surface and improve efficiency. When photons of light enter the cell from the top, they first pass through

Fig. 3.9  Schematic cross-section of a silicon solar cell

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31

the pyramid shape layer then through n-type silicon, and at the boundary between n-type and p-type silicon, they most likely achieve collision with the atoms of silicon and produce electron-hole pairs. Then, electrons travel upward and are collected in the front metallic contacts as current. The general principle of operation and construction is very similar for all types of solar cells, including thin-film solar cells. Note that some advanced types of solar cells have very different design and the mechanisms of operation. Single-silicon solar cells have voltage of approximately 0.5 V and typical short circuit current less than 10  A (current depends on the surface area of the cell). Except for some small portable applications, higher voltage is necessary for the application, and for that reason, single cells are combined into arrays of cells and packaged as larger devices called PV panels or a modules. In most cases, single cells are electrically connected in series to increase the voltage, while the current stays the same. For instance, one of the solar PV applications is for standalone electrical systems with battery storage, and the primary requirement from a solar PV module is to charge a 12-V battery. For this, a 36-cell in series modules have become the standard for many decades. A typical module is shown in Fig. 3.10. A solar PV cell is characterized by voltage and current. As the load changes, the operating point of a solar cell changes through the range of values, from short circuit current, Isc, to open circuit voltage, OCV.  The short circuit current is directly proportional to the intensity of the solar light, which is the flux of photons. Each photon of a wavelength shorter than a critical wavelength for a particular solar cell material generates one electron. Only a fraction of the incoming photons is successful in creating an electron in a solar cell. Therefore, since the number of electrons depends on the number of incoming photons, the short circuit current is proportional to the intensity of the solar light (Fig. 3.11). As the intensity of light increases, the current increases proportionally, e.g., if the short circuit current for 1000 W/m2 is 5 A, then the ISC for the irradiance of 500 W/ m2 will be 2.5 A. The open-circuit voltage, VOC, also increases with an increase in irradiance, but logarithmically.

Fig. 3.10  Solar PV module comprising 36 cells

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Fig. 3.11  Current voltage dependency for a solar PV cell at different solar intensity

Fig. 3.12  Solar PV power curve

The general shape of the curve is always the same, with the current starting at Isc, very slowly declining as the voltage increases and then sharply dropping to zero current at the open circuit voltage. After the knee of the curve, the current drops rapidly to zero and intersects the voltage axis. This is the maximum voltage for the cell and it is not producing any power. Besides current and voltage, the power can be expressed in the graph (Fig. 3.12). Power is the product of voltage and current (P = I × V) and can be shown in the same graph as it is the product of voltage and current. The maximum power point is at the “knee” of the current voltage curve. At that point the current is slightly lower than Isc. After the knee of the curve, a small increase in voltage causes rapid drop in current. The reasons that the power from a solar cell is not a product of Isc and OCV

3  Renewable Energy Sources

33

are that losses occur because of the resistance to flow of electrons in the cell and in the contacts and terminals, which causes voltage drop. This is called series resistance. Another type of resistance is called shunt resistance and refers to leakage current through the silicon device whereby electrons travel through defects and imperfections from manufacturing process and recombine with positively charged holes without creating electrical current. The defects and imperfections are a result of imperfect fabrication process steps and impurities or crystalline lattice imperfections. While the series resistance should be as low as possible to minimize voltage drop, the shunt resistance should be as large as possible to minimize leakage current. If there were no resistance losses, the total power from a solar cell would be the product of Isc and OCV, geometrically it would be the surface area of the rectangle with sides made of current and voltage, and the shape of the current vs voltage curve would be flat line, at Isc. However, since there are resistive losses as described above, the actual practical shape of the current vs voltage curve does not completely fill the rectangle and is suppressed down to the extent of the losses. To describe the actual solar cell performance, another useful parameter used is the fill factor (FF), the ratio between IPmax × VPmax and Isc × Voc (Eq. 3.10): FF 

VmaxP  I maxP . VOC  I SC

(3.10)

It should be obvious that a larger FF means that the cell has low resistive losses and is preforming better, while a more suppressed curve means that the resistive losses are higher and the performance is worse. Fill factors of around 0.8–0.9, or 80–90%, are common for silicon solar cells. This indicates that the resistive losses can commonly be in the range of 10–20%. It should be noted that this should not be confused with the overall efficiency of a solar cell, which is much lower and refers to the ratio of generated power and the total power of the solar light shining on the cell (Eq. 3.11):





PmaxP , EA

(3.11)

where E is the solar irradiance, i.e., power, and A is the surface area of the solar PV module. For instance, if PmaxP = 320 W and irradiance is 1000 W/cm2 (standard test conditions) and module surface area is 1.6 m2, the efficiency is 0.2 or 20%. There are two main types of applications for solar PV systems: standalone or off-grid and grid- (or utility) connected. Standalone systems are used for locations that are typically far from the electrical grid and provide power for lighting, refrigeration, water purification, and water pumping. They contain additional components such as battery energy storage, charge controller, inverter (in case there are AC loads), wire, switches, breakers, etc. These systems are of great importance for developing countries. Examples of a small standalone systems are shown in Figs. 3.13 and 3.14.

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Fig. 3.13  Example of a standalone PV system

Fig. 3.14  Example of a standalone system

Grid-connected PV systems are used to lower individual location electricity consumption from the grid. The electricity produced is exchanged with the grid and used when the user has a demand. Besides solar PV panels, a system has additional components (Fig. 3.15). In summary, Cuba has considerable potential for efficient use of solar PV technology, and the country has aggressively started an era of solar photovoltaics,

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35

Fig. 3.15  Schematic of a grid-connected PV system

expecting to replace a significant part of the energy generation with this elegant and effective technology. (c) Geothermal Cuba currently has no geothermal energy generation. However, as part of long-­term plans, geothermal generation has been considered. Cuba has hot water springs indicating geothermal activity, and so far, the resource has been used not for generating heat or power, but instead it has been used to promote medicinal tourism. The program advertised as thermal tourism and called “Ruta del Agua” has been promoted as health tour packages and coordinated with the ministry of tourism [21]. The main areas where the hot springs have been located include San Diego de los Baños, San Vicente, San Miguel de los Baños, Elguea, Ciego Montero, La Cotorra, and the Ciego Montero near Cienfuegos [21]. The fact that Cuba has abundance of hot water springs indicates considerable heat flux to the surface and presence of favorable geography for harnessing larger amounts of heat. Geothermal energy is the internal heat energy of the earth that can be directly used to provide heat and to generate electricity. Geothermal energy is hugely underused in the world, so it is not surprising that it has not received much attention in Cuba. Earth’s internal heat was developed from the kinetic and gravitational energy when the planet was formed about 5 billion years ago. This energy is not being replenished. About 50% of heat is created from the radioactive decay of long half-­ life radioactive isotopes Thorium 232, Uranium 238, and Potassium 40. The heat created in these two processes flows toward the surface and can be captured at the surface for power generation. Geothermal heat flow to the surface is on average 60 mW/m2. This is quite low for any practical use; however, the heat flow is much larger, about 300 mW/m2 at the boundaries between the tectonic plates. At some

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locations on earth, geothermal heat spontaneously escapes to the surface at high rate. The locations on earth are mainly along the so-called Ring of Fire, a stretch of earth’s surface along the Pacific Ocean basin susceptible to volcanic activities and earthquakes. Geothermal heat is considered a renewable energy because of the very large amount contained in the core of the earth, which is many times larger than the needs of the humanity. However, for a specific location where geothermal heat is collected, there might be a point in time when the resource is exhausted and not regenerated or regenerated too slow on the scale of a human lifetime. There are three classes of geothermal heat: low enthalpy with temperatures less than 100  °C, medium enthalpy heat with temperatures 100–180  °C, and high enthalpy heat with temperatures in the excess of 180 °C. High enthalpy locations are suitable for electricity generation, while medium and low heat resources can be used to directly capture heat, for example, in district heating, greenhouses, pools, etc. For instance, hot water from geothermal sources can be utilized through a heat exchanger for heating hot water for a city. To understand the heat flow through the surface, a formula can be applied that involves surface area, thermal conductivity, and temperature (Eq. 3.12):



Q

kA  Thot  Tcold  d

.



(3.12)

where Q = amount of heat flow, k = thermal conductivity, A = surface area, T = temperature, and d = depth. For instance, if the temperature is 60 °C at a depth of 2 km, the surface temperature is 10 °C, and the thermal conductivity of the rock is 2.5 W/ m°C, the flow rate is calculated to be 0.0625 W/m2. While obtaining low and medium enthalpy heat for residential or industrial heating or for hot water supply can be very effective and whole cities can be heated like that (e.g., Reykjavik, Iceland), the more attractive option is to extract and capture high enthalpy heat and use it to generate electricity. This goal can be accomplished by drilling into the ground to reach underground reservoirs to obtain hot water or steam from rocks that are deep or dry heat. The heat obtained from geothermal sources must be at least 150 °C to be used in conventional steam turbines to produce electricity. The heat heats water, creating steam, which is used to spin a turbine, run a generator, and produce electricity. The steam can then be condensed after it passes through the turbine, or alternatively the exhaust can be discharged into surrounding. Many geothermal resources do not contain water, but hot, dry rock. In that case, a fluid must be pumped underground between hot rock, where it gets heated and brought back to the surface as hot water (Fig. 3.16). The other geothermal power plants include dry steam power plant, flash steam power plant, and binary cycle power plant. There is very little environmental impact or inconvenience in utilizing low and medium enthalpy geothermal sources for heat and hot water. The exploitation of high enthalpy heat for power generation, however, may lead to concerns regarding

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37

Fig. 3.16  Schematics of the hot rock extraction principle

site preparation, noise, disposal of drilling fluids, long-term gaseous pollution from gases released from the drilling, ground subsidence, and even potential trigger of the seismic activities. The polluting gases that can be released include CO2, H2S, SO2, and CH4, along with nonpolluting gases such as H2 and N2. One of the most dangerous and toxic gases is H2S, and modern plants are required to provide for their removal, i.e., scrubbing. It should be understood, however, that the quantities of these gases are much less than when burning fossil fuels. The plant construction for geothermal hot water collection on the surface can be challenging because of high corrosivity of water, which contains high amounts of silica, chlorides, carbonates, as well as heavy metals. To prevent release of pollution or corrosive liquids to the surrounding, geothermal plants are typically made as closed-cycle systems. Another potential opportunity for Cuba is developing and using the concept of ground source heat pumps, which transfers heat from a colder body to a hotter body. The source of heat to heat the ground is not geothermal, but the Sun. This process cannot take place without an external input of energy; otherwise, the laws of thermodynamics would be violated, as heat moves in a spontaneous process from high-temperature spot to low-temperature spot. Heat pumps are very efficient for both heating and cooling; their operation is consistent with criteria for renewable energy, although the electrical energy to drive the pump may not come from renewable energy sources. Since a heat pump transfers heat from colder body to warmer body, while using electricity, it is obvious that a refrigerator is a type of a heat pump. For all heat pumps, we can measure the coefficient of performance (COP), which is a measure of heat produced to the amount of energy, i.e., electricity, used to produce the heat or pump. In the case of cooling, the COP defines the decrease in heat energy per unit of energy used (Eqs. 3.13 and 3.14): COPheating 

Qheat . Eelectric

(3.13)

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COPcooling 

Qcool . Eelectric

(3.14)

Based on the laws of thermodynamics, COP cannot exceed the inverse of the Carnot efficiency and COP ranges from 2 to 5. At first, this may seem a violation of the first law of thermodynamics since it appears that energy is created out of nothing; however, the heat is not created, it is only moved from one place to another, and because of that, COP can be so high, corresponding to efficiency of 500%, the term which is avoided to prevent confusion. Majority of heat pumps are air-source heat pumps and use outside air as a thermal heat sink to release heat during the summer and from which it is drawn during the winter. However, outside air is not an ideal heat sink as it is too warm during the summer when the heat must be released into it and too cold during the winter when heat must be drawn from it. The temperatures in Cuba are not that low in winter, but they are high in the summer and the rest of the year and would require a heat pump to draw heat from the hot air, which is not very efficient because the heat sink should be ideally cold. These conditions in Cuba are inconvenient for heat sink temperature and would reduce the efficiency of air-source heat pumps. However, an alternative is to use geothermal heat pumps (GHP) to take advantage of ground as a colder heat sink, as the ground temperature 2–3 m below the surface remains constant during the year, despite surface temperatures varying greatly. Hence, geothermal heat pumps use earth as a thermally stable and consistent heat sink and buried pipes to exchange heat between the ground and the inside. There are open- and closed-loop systems (Fig. 3.17).

Fig. 3.17  Schematics of open and closed geothermal heat pumps providing heating and cooling for a house [22]

Chapter 4

Energy Storage

Abstract  In the context of Cuba’s shift to more renewable energy sources for its future energy generation mix, energy storage becomes a critical component for the overall energy system of the country. After a general classification of the energy storage technologies, the two most promising energy storage methods, batteries and fuel cells, are discussed in more detail in this chapter. Fundamentals are presented to explain the differences between these technologies, and the most important battery and fuel cell systems are explained, including their advantage and disadvantages. Keywords  Energy storage · Batteries · Lithium batteries · Fuel cells · Hydrogen · Solar-hydrogen cycle Cuba has been significantly dependent on fossil fuel imports, and the country is rightfully shifting toward renewable energy sources for the future. However, renewable energy is intermittent and unreliable, i.e., it is not always available when there is demand. The solution is in developing energy storage capacities that would be replenished, i.e., charged in case of batteries, during the times when renewable energy generation such as solar or wind is available and later used for applications at the time of the demand. There are very little records of energy storage capacities in Cuba. There are no large energy storage facilities such as pumped hydro or compressed air energy storage and no hydrogen production through electrolysis plants. The use of batteries is evidently limited to single users, and no large battery storage facilities have been reported. The energy storage seems to be in the infancy in Cuba, and only scarce articles or reports on the prospects and benefits appear in the open sources [15]. There is however a promising report that state-owned power generator entity (NTPC) is soliciting global bids on behalf of Unión Eléctrica de Cuba (UNE) for 1150  MW of grid-connected solar PV and 150  MW/150  MWh battery energy storage system (BESS) projects in Cuba. Energy storage methods can be classified based on the type of energy stored as mechanical, including pumped hydro, compressed air, and fly wheel; electrochemical © The Author(s), under exclusive license to Springer Nature Switzerland AG 2023 S. Petrovic, Renewable Energy in Cuba, SpringerBriefs in Energy, https://doi.org/10.1007/978-3-031-37473-9_4

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40

including batteries, fuel cells, and electrochemical double layer supercapacitors; thermal, including storage heaters and phase change materials; and electrical systems such as superconducting magnetic energy storage and supercapacitors. Other classifications are bulk energy storage and distributed (i.e., small scale) and based on the relative amount of energy and power, high-power or high-energy systems. The performance characteristics of energy storage systems can be measured and analyzed based on many factors, some of them are energy density, specific energy, specific power, cycle life, charge/discharge time, safety, and cost. Energy density is a property expressing the amount of energy stored per unit of volume, while specific energy is the amount of energy per unit of weight. These are the most important characteristics of energy storage technology for portable or motive applications, such as electrical vehicles, but are less critical in stationary or utility applications. Energy storage methods are compared based on duration of energy delivery and size, as shown in the Fig. 4.1 in the same graph. The relative positions of the energy storage methods on the graph should indicate general characteristics or application areas, but technology reach is not fixed or limited, and the areas on this, or similar graphs, certainly overlap, meaning that sometimes similar performance can be obtained from different systems. Each technology also depends on the specific subtype, for example, there are several dozen types of Li batteries and on the manufacturer or even a production lot. The general, high-level conclusions from this graph should be that the large-size, long-­ duration technologies are pumped hydro and compressed air energy storage, while short-duration, high-current devices are supercapacitors and some type of flywheels. In between are all other methods, including various types of batteries and fuel cells. And while Cuba currently does not have any recorded large energy storage, it is useful to provide a short overview of the available technologies. Pumped hydro energy storage (PHS) is based on pumping water using available electricity, typically

Discharge time

Hours

Metal-air batteries

Pumped hydro Flow Batteries

Fuel Cells

CAES

Batteries

Minutes

Supercapacitors Second W

kW

Flywheels SMES MW

GW

Power Fig. 4.1  Energy storage method relative comparison based on discharge duration and power

4  Energy Storage

41

during the night (e.g., from wind energy) to a reservoir at a higher point and releasing it through a turbine during the time of demand, typically during the day. The energy storage capacity of pumped hydro plant is based on the potential energy of water in the upper reservoir. The turbines are similar to turbines used in hydroelectric power stations, or they can be bidirectional, i.e., they can be used to pump water up and to generate electricity on the way down. Because of its large size, PHS provides more energy storage capacity than all of the other methods combined, although the number of facilities globally is very small. Compressed air energy storage is another large-scale energy storage, and there are only two known large facilities in the MW range globally. Recently, new technologies have been developed for smaller-scale operation. The method involves using a compressor to pump and compress air in the underground storage and releasing it during the demand. The released air expands while being heated, and that expansion drives a turbine and runs a generator that produces power. The underground storage is a terrain requirement, typically in limestone caverns or unused salt mines, and because of that, compressed air energy storage is possible only where the geographical conditions permit it. A conceptual diagram of compressed air energy storage facility is shown in Fig. 4.2. Batteries, fuel cells, and electrolytic supercapacitors are electrochemical energy storage devices. These devices are based on electrochemical principles and have two electrodes immersed in electrolyte and charge being transferred ionically in the electrolyte [16–19]. On one electrode, the anode, oxidation reaction takes place, e.g., hydrogen oxidation; while on the cathode, a reduction reaction takes place,

Fig. 4.2  Diagram of a hypothetical compressed air energy storage plant

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e.g., oxygen reduction. In these devices, chemical energy is directly converted to electricity. Beyond basic principles, these devices are different. Batteries contain fixed amounts of active mases on the electrodes, anode and cathode. Secondary or rechargeable batteries can be reused after delivering power and exhausting their capacity, by recharging them. Fuel cells, on the other hand, rely on continuous supply of reactants to electrodes to produce power. There are also some hybrid devices, metal-air batteries where one electrode is a classical battery electrode, the anode, while the cathode is similar to a fuel cell cathode and open to the surrounding as reactant oxygen is supplied from air. A flow battery has reservoirs of active substances in solutions, which are circulated into a cell. The amounts of reactants are fixed, as in case of batteries, but the solutions are fed into the electrodes as in fuel cells [19]. Electrochemical supercapacitors don’t have reactants but use large surface area electrodes to absorb charge, which is discharged at the time of demand. They are characterized by high currents and rapid discharge. Batteries have active masses on their electrodes, or in solutions in case of flow batteries, and their capacity or amount of energy that they can provide to a load depends on the chemical nature of active materials and their amounts. In primary batteries, the reactions are not reversible, and the battery cannot be recharged or used again after discharge. Secondary or rechargeable batteries can be recharged multiple times. The most important characteristics of batteries are energy density (capacity per unit weight or volume), discharge current, cell voltage, self-discharge rate, charging time, cycle life, shelf life, temperature impact, environmental impact, and cost. The relative importance of these characteristics depends on the application requirements. For use in either utility applications as energy storage for renewable energy or in off-grid solar PV systems, the most important characteristics of batteries are cycle life, efficiency, safety, and cost. The most important rechargeable battery systems are lead-acid, nickel-cadmium, nickel-metal hydride, and lithium-ion. Their characteristics are shown in the Table 4.1. Fuel cells are also electrochemical devices that operate on continuous supply of fuel and oxygen. The most common fuel is hydrogen, but other fuels such as methane, methanol, and ammonia can also be used. There are five types of fuel cells, based on the type of electrolyte they use and the temperature of operation (Table 4.2). Table 4.1  Main properties of four rechargeable battery systems Battery type Lead acid (LA) Nickel-cadmium (NiCd) Nickel-metal hydride (NiMH) Lithium Ion (Li-ion)

Voltage (Volt) 2.0 1.2 1.2 4.0

Anode Pb Cd Metal hydride Li (C)

Cathode Lead oxide Nickel oxide hydroxide Nickel oxide hydroxide Lithium cobalt oxide

Electrolyte Aqueous sulfuric acid Aqueous potassium hydroxide Aqueous potassium hydroxide LiPF6

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Table 4.2  Characteristics of fuel cells Fuel cell technology Alkaline Fuel Cell (AFC) Proton Exchange Membrane Fuel Cell (PEMFC) Phosphoric Acid Fuel Cell (PAFC) Molten Carbonate Fuel Cell (MCFC) Solid Oxide Fuel Cell (SOFC)

Efficiency, % 50–60

Operating temperature, °C 60–90

Polymer membrane, such as Nafion

50–60

50–80

Concentrated H3PO4

50–55

160–200

Li2CO3/Na2CO3

60–65

620–660

ZrO2/Yt2O3

55–65

800–1000

Electrolyte used 35–50% KOH

Application areas Space traction Space portable Dispersed power Power generation Power generation

The use of fuel cells is envisioned in the context of a larger concept of hydrogen economy. For the country of Cuba, with great potential for renewable energy generation, a comprehensive energy system relying on renewable energy technologies, such as solar PV, coupled with energy storage will achieve maximum results. The electricity from solar PV can be used directly to electrolyze water and produce hydrogen, which would be first stored and then used in fuel cells at the time of demand. This concept, called solar-hydrogen cycle, would ensure completely clean energy generation, storage, and use, but it would be viable only if the cost of producing hydrogen is low or zero. Hydrogen is not available freely in nature and must be produced first before use in fuel cells. Hydrogen production from fossil fuels, i.e., methane or natural gas, is inexpensive but produces CO2 and is not an optimal solution. However, hydrogen production from electrolysis of water, powered by electricity from a solar PV, for example, is the ideal combination. The electricity can of course be supplied from other renewable energy sources such as wind, hydropower, ocean energy, or bioenergy. The solar-hydrogen cycle starts and ends with clean water, and it doesn’t produce any emission. Hydrogen is subsequently stored and distributed to the point of use through a network of pipelines. For further information on energy storage, in particular electrochemical energy storage, batteries, fuel cells and hydrogen, consult the references [16], [18], and [19].

Chapter 5

Electrical Grid and Energy Resiliency

Abstract  In this chapter, an overview of Cuba’s electrical grid, its components, and condition are discussed. The partition between centralized and distributed energy generation and the implications on the electrical grid are explained. The resiliency of the electrical grid and the factors affecting it, such as hurricanes, earthquakes, draughts, and wildfires, are analyzed. The outcomes and aftermath of some of those occurrences have been presented, in order to recommend improvement for a more resilient electrical grid and to reduce the frequency of power disruption. Keywords  Electrical grid · Cuba electrical grid · Power disruption · Blackouts · Hurricanes in Cuba · Flooding in Cuba · Electrical grid resiliency Cuba’s electrical grid is extensive and covers nearly 95% of the country with 2833 km of 220 kV lines and 4188 km of 110 kV lines. The country made significant improvement since 1959 when only 50% of homes had electricity, and by 1990, 95% of the homes were covered. However, the grid is very old and fragile. The transmission losses are high and reach close to 20%, which is similar or lower compared with other countries in the Latin America and the Caribbean. The main reason for transmission losses is bad technology used to mount conductors, as shown in examples below (Fig. 5.1). Unfortunately, the entire system is outdated and needs repair (Fig. 5.2). The energy planning in Cuba has been directed toward distributed generation because of the frequent damage to the infrastructure due to hurricanes, and the country invested $1.2 B to build 2.5 GW of distributed generation capacity. This is an impressive 42% of the total generation, which puts Cuba in the second place globally, only after Denmark. The distributed generation capacity comprises 1280 MW of diesel generation, 540 MW of fuel oil motors, 5.29 MW of combined heat and power, and 69 MW of renewable energy sources. The resiliency of Cuba’s energy system has been greatly improved with distributing the generation, and natural disasters are now less likely to catastrophically impact the country because each affected plant contributes less to the grid. Smaller units can also be repaired faster and connected back to the grid. However, distributed © The Author(s), under exclusive license to Springer Nature Switzerland AG 2023 S. Petrovic, Renewable Energy in Cuba, SpringerBriefs in Energy, https://doi.org/10.1007/978-3-031-37473-9_5

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Fig. 5.1  Example of Cuba’s electrical grid components

generation is located closer to populated areas and brings emission closer to homes. Cuba’s distributed generation systems are located all over the country, for example, Havana has 85.6 MW from 56 diesel generators, Mariel has 147 MW from 11 fuel oil generators, and Moa has 174.6 MW from 20 fuel oil generators [20]. Electricity rolling blackouts are a normal fact of life in Cuba. To a large extent, they are caused by geopolitical circumstances beyond Cuba’s control. However, one must wonder if the reliance on oil for power from the early 1960s and agreements with Soviet Union and later similar agreements with Venezuela have reenforced country’s dependence on fossil fuels and created inevitable setbacks because of the lack of alternatives. It is evident that Cuba is trying to make a shift to renewable energy source, but the dramatic change is not coming soon enough. In addition to simple and continuous dependence on importing crude oil, the age and vulnerability of the electric grid has precipitated in sometimes preventable failures of the grid as transmission lines break by reaching its lifetime or from weather elements such as hurricanes. The power plant failures due to the burning of sulfur rich oil can also not be neglected [1]. It may be well advised to explore technologies for sulfur removal and further use. The catastrophic meteorological conditions are probable in Cuba. There is evidence of global warning in Cuba. The average temperature increased 0.9° from 1951 to 2010. The occurrences of dramatic climate events, such as drought, have increased indicating climate variations. There are no records that electrical grid reliability and resiliency have been systematically applied in Cuba. It is important to review the basics before considering appropriate metrices to evaluate these categories for the energy and electrical grid

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Fig. 5.2  Example of Cuba’s electrical grid components

in Cuba. There are several developed, mature metrics that can be used determine reliability and develop a clear plan for improvements. Reliability metrics include generation and transmission systems and distribution systems. As in most other countries, the oversight of reliability at the distribution level is handled by the state regulatory agency.

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Fig. 5.3  Overview of events that can cause disruption of power systems. The relative time of warning and recovery time are given on axis [23]

Many different causes are responsible for disruption of the power systems. The causes of disruption of the electrical service in Cuba are characterized by how much warning can operators get about the disruption in order to take protective action and what part of the system will remain operational after the disruption ends. To consider the actions for improving system reliability, we will overview the events that can cause disruption (Fig. 5.3). The most serious danger to Cuba are the hurricanes. The warning time is typically several days, but the trajectory, i.e., landfall position and intensity predications, is always changing. Hurricanes can have impact on power systems first through the effects of wind and rain, storm surge, and flooding as a result of precipitation. The tropical cyclones are expected to become more intense and more frequent because of the climate changes.Cuba is susceptible to natural disasters, primarily hurricanes that last typically from June till November. The intensity of hurricanes hitting Cuba is increasing, most likely because of the warmer sea temperature and natural climate variations (Fig. 5.4). In 2017, one of the strongest hurricanes in 80 years, with winds up to 250 km/h and huge ocean swells, devastated Cuba, causing substantial infrastructure damage. The financial impact of the damage was estimated at more than US $13 B.  The ocean swell flooded the streets of the capital Havana (Fig. 5.5). In total, the flooding affected 158,554 dwellings, 980 health institutions, 2264 schools, 466 poultry farms, 95,000  hectares of cropland, 246,707 landlines, and 537 km of roads [15]. After Hurricane Irma, many areas were left without power for several days (Fig. 5.6).

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Fig. 5.4  Frequency and intensity of hurricanes that reach the intensity 3 or greater, on the Golf coast. Dark line is the 5-year average [24]

Fig. 5.5  Residents in Havana after Hurricane Irma

But only weeks after the disastrous storm, the country’s main electrical generator had been restored [16]. Figure 5.6 shows downed telephone lines after the strong winds of the hurricane. Earthquakes can cause significant damage to distribution poles, transmission towers, substations, and generators. In fossil fuel power plants, there is a risk of loss of fuel, particularly in pipelines. Earthquakes come without warning, but their impact wave propagates slowly, giving a few seconds warning that could provide enough time to de-energize the critical components of energy system and reduce the damage. More advanced warning and better automation of the control systems would further improve the chances to save components and prevent damage.

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Fig. 5.6  Downed telephone lines in the Villa Clara province after Hurricane Irma

Furthermore, the technology advancements produce new materials and designs for electrical power systems, such as more durable ceramic and nonceramic insulators, flexible electrical connectors, and advanced materials for towers. The restoration after an earthquake may take from minutes to weeks, depending on the level of damage. If substations and transmission equipment get damaged, the restoration may take weeks or months. Earthquakes are possible in Cuba, particularly near the city of Santiago, in the Eastern part of the country. The city suffered devastating earthquakes in the past, in 1624, 1678, 1766, and 1852. This part of the country is positioned along a tectonic dislocation, a linear zone of disturbed rock strata, with a combination of folding and faulting disturbance, nearly 1250 miles long, stretching from the southern coast of the east end of the island and forms the northern boundary of the Bartlett Trough, a depression that in one part reaches a depth of 3506 fathoms, or about 6.5 km. A physical attack can be a serious concern and can cause significant physical damage to transformers and other equipment, namely, parts for substation and transmission equipment, as well as high-voltage circuit breakers. While Cuba is generally a safe country and generation facilities are well protected, examples of physical attacks on electrical grid have been reported from Colombia, Iraq, Peru, Thailand, and Afghanistan substations and transmission facilities. Droughts have increased in Cuba in the last decade, and there is a significant level of confidence that they will intensify due to increased evaporation. They can have multiple implications for power systems, primarily by impacting hydroelectricity generation and reduction in water availability to cool power stations. During the droughts and elevated temperatures, the power systems get stressed, which increases probability of hardware failure. Wildfires have been quite common in Cuba, with about 80 wildfires burning just in 2023 probably as a result of climate change. The wildfires have been propagating

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toward Santiago de Cuba. The impact by wildfires is typically not catastrophic but can cause serious damage to substations and transmission systems. The power flows may need to be redirected to avoid affected parts of the country. By controlling the vegetation around the power system’s equipment, the vulnerability can be reduced although fire spread sometimes is hard to stop and wildfire manages to go over significant barriers. The restoration of power systems after a wildfire typically takes days or weeks.

Chapter 6

Conclusions and Recommendations

Abstract  A summary of Cuba’s energy system analysis concludes the text. The evaluation of the country’s plans to increase energy generation contribution from renewable energy sources is supported by findings of this study and general recommendations are presented for development of energy storage capacities that are essential in an energy system largely dependent on the renewable energy generation. The main goal of the book, to emphasize the importance of reduced reliance on fossil fuels, is underscored at the conclusion of chapter. Keywords  Energy system in Cuba · 2030 energy vision · Biomass in Cuba · Solar PV in Cuba · Wind in Cuba · Distributed generation in Cuba Cuba presents a unique model for studying how an isolated economy has developed its energy system. The country has made some impressive, sensible changes in the way energy is generated and distributed. Most remarkable have been the shifts toward distributed generation and renewables. While at present a large majority of country’s energy generation comes from fossil fuels, oil and gas, the energy “mix” may look different in a few years when a larger component of renewable energy, in form of solar photovoltaics, wind, small hydro, and biomass, is added. Cuba has additional potential that deserves exploration in ocean energy and geothermal energy. Cuba lacks significant capacities and planning to develop energy storage capacities that will support addition of renewable energy generation. Developing battery storage capabilities as well as hydrogen generation, through electrolysis, storage, and use in fuel cells, would be rational. Ultimately, Cuba must work toward reducing reliance on foreign fossil fuels and must strive toward achieving energy independence for the future generations of its citizens. In addition, the country should develop measures to improve the condition of its electrical grid and improve its resiliency.

© The Author(s), under exclusive license to Springer Nature Switzerland AG 2023 S. Petrovic, Renewable Energy in Cuba, SpringerBriefs in Energy, https://doi.org/10.1007/978-3-031-37473-9_6

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References and General Bibliography

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15. T.  Morales, V.  Oliva, L.  Velazquez, Hydrogen from Renewable Energy in Cuba, Energy Procedia, Volume 57, 867–876, 2014. 16. Petrovic, Kurzweil, and Garche, “Electrochemical Energy Storage”, McGraw Hill, 2022. 17. E.  Hossein and S.  Petrovic, “Renewable Energy Crash Course  – A Concise Introduction”, Springer, 2021. 18. Slobodan Petrovic, “Electrochemistry Crash Course for Engineers”, Springer, ISBN 978-3-030-61561-1, 2020. 19. S. Petrovic, “Battery Technology Crash Course”, Springer, eBook ISBN 978-3-030-57269-3; Hardcover ISBN 978-3-030-57268-6, 2020. 20. Michael Panfil, Daniel Whittle, and Korey Silverman-Roati, “The Cuban Electric Grid”, Environmental Defense Fund, 2017. edf.org/electricity-in-cuba. 21. https://www.cubabusinessreport.com/the-­ruta-­del-­agua-­thermal-­tourism-­in-­cuba/ 22. Mary H. Dickson and Mario Fanelli, “What is Geothermal Energy?”, Istituto di Geoscienze e Georisorse, Pisa, Italy 2004. English translation available at: http://users.metu.edu.tr/mahmut/ pete450/Dickson.pdf 23. http://nap.nationalacademies.org/24836 24. (A) The National Atlas and USGS (2005) and (B) UCS (2016) at www.ucsusa.org. (A) The National Atlas and USGS (2005) and (B) UCS (2016) at www.ucsusa.org. 25. World Energy Handbook, S. Petrovic, ed., Springer, 2023. 26. https://www.worldometers.info/coal/cuba-­coal/

General Bibliography World Energy Handbook, S. Petrovic, ed., Springer, 2023. M. Panfil, D Whittle, K Silverman-Roati. The Cuban Electric Grid: Lessons and Recommendations for Cuba’s Electric Sector, Environmental Defense Fund, October 2017. Accessed on: July 7, 2020. [Online]. Available: https://www.edf.org/sites/default/files/cuban-­electric-­grid.pdf International Hydropower Association. 2018 Hydropower Status Report: Cuba, IHA, June 2018. Accessed on: July 7, 2020. [Online]. Available: https://www.hydropower.org/ country-­profiles/cuba A. Alawsat. Wind power, potential in Cuba, Energy Central News, August 22, 2019. Accessed on: July 7, 2020. [Online]. Available: https://energycentral.com/news/wind-­power-­potential-­cuba L.  Herrera. Unique features of Cuba’s wind farms, Granma, March 6, 2019. Accessed on: July 7, 2020. [Online]. Available: http://en.granma.cu/cuba/2019-­03-­06/ unique-­features-­of-­cubas-­wind-­farms J. Pedraza, Solar Energy in Cuba: Current Situation and Future Development, Journal of Solar Energy Research Updates, June 2019. A.  Sanchez, Cuba’s First Biomass-Fired Power Plant Inaugurated, Power Magazine, June 30, 2020. Accessed on: July 7, 2020. [Online]. Available: https://www.powermag.com/ cubas-­first-­biomass-­fired-­power-­plant-­inaugurated/ R.  Rivas, Using waste from rice processing to generate energy, Granma, August 27, 2019. Accessed on: July 7, 2020. [Online]. Available: http://en.granma.cu/cuba/2019-­08-­27/ using-­waste-­from-­rice-­processing-­to-­generate-­energy M. Frank, Death of Castro could free Cuba to produce biofuels, Reuters, December 1, 2016. Accessed on: July 7, 2020. [Online]. Available: https://www.reuters.com/article/us-­cuba-­castro-­ethanol/ death-­of-­castro-­could-­free-­cuba-­to-­produce-­biofuels-­idUSKBN13Q5O6 Knoema, Cuba – Fuel ethanol production, World Data Atlas. Accessed on: July 7, 2020. [Online]. Available: https://knoema.com/atlas/Cuba/topics/Energy/Renewables/Fuel-­ethanol-­production Advanced Biofuels USA, Biodiesel Plant Opening up in Eastern Cuba, Advanced Biofuels USA, February 8, 2017. Accessed on: July 7, 2020. [Online]. Available: https://advancedbiofuelsusa. info/biodiesel-­plant-­opening-­up-­in-­eastern-­cuba/

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Y. Zhao, Power Shift in Cuba: Seven Reasons to Watch the Renewable Energy Sector in the Post-­ Fidel and Trump Era, Renewable Energy World, February 10, 2017. Accessed on: July 7, 2020. [Online]. Available: https://www.renewableenergyworld.com/2017/02/10/power-­shift-­in-­cuba-­ seven-­reasons-­to-­watch-­the-­renewable-­energy-­sector-­in-­the-­post-­fidel-­and-­trump-­era/#gref B. Epp, Cuba: Solar Water Heating Could Reduce Pressure on Power Grid, Solar Thermal World, March 22, 2016. Accessed on: July 7, 2020. [Online]. Available: https://www.solarthermalworld. org/news/cuba-­solar-­water-­heating-­could-­reduce-­pressure-­power-­grid T. Morales, V. Oliva, L. Velazquez, Hydrogen from Renewable Energy in Cuba, Energy Procedia, Volume 57, 867–876, 2014. M.  Barona, M.  Giraldo, S.  Marini, Biohydrogen as an Alternative Energy Source for Cuba, Association for the Study of the Cuban Economy, November 30, 2013. Accessed on: July 7, 2020. [Online]. Available: https://www.ascecuba.org/asce_proceedings/ biohydrogen-­as-­an-­alternative-­energy-­source-­for-­cuba/ E.  Loveday, Cuba shows interest in hydrogen vehicle technology, Autoblog, June 8, 2011. Accessed on: July 7, 2020. [Online]. Available: https://www.autoblog.com/2011/06/08/ cuba-­shows-­interest-­in-­hydrogen-­vehicle-­technology/ Argus Media, Cuba hit by wave of blackouts, Argus Media, July 18, 2019. Accessed on: July 7, 2020. [Online]. Available: https://www.argusmedia.com/en/ news/1942483-­cuba-­hit-­by-­wave-­of-­blackouts Earthstar Geographics, Impacts of Hurricane Irma on Cuba, ESRI. Accessed on: July 7, 2020. [Online]. Available: https://www.arcgis.com/apps/MapJournal/index.html?appid=2cc58eca2e 9c40c98c9a8fb0d4d6a5e3#:~:text=Hurricane%20Irma%20is%20the%20strongest,place%20 causing%20houses%20to%20flood. R.  Jervis, “I’ve lost everything.” Cubans face damage from Hurricane Irma, USA Today, September 10, 2017. Accessed on: July 7, 2020. [Online]. Available: https://www.usatoday. com/story/news/world/2017/09/10/cuba-­sees-­devastation-­hurricane-­irma/651125001/ M.  Whitefield, 100,000 Cuban homes slammed by Hurricane Irma await repairs months later, Miami Herald, January 15, 2018. Accessed on: July 7, 2020. [Online]. Available: https://www. miamiherald.com/news/nation-­world/world/americas/cuba/article194517349.html Reliefweb, Cuba: Hurricane Irma – Emergency Appeal Final Report, Reliefweb, December 12, 2019. Accessed on: July 7, 2020. [Online]. Available: https://reliefweb.int/report/cuba/cuba-­ hurricane-­irma-­emergency-­appeal-­final-­report-­mdrcu004#:~:text=Hurricane%20Irma%20 made%20landfall%20in,8%20to%2010%20September%202017.&text=Hurricane%20 Irma%20caused%20a%20total,cyclonic%20event%20in%20Cuba's%20history. Rico, Over 70% of Cuba’s Power Restored After Hurricane Irma, Q Costa Rica, September 15, 2017. Accessed on: July 7, 2020. [Online]. Available: https://qcostarica.com/ over-­70-­of-­cubas-­power-­restored-­after-­hurricane-­irma/ Water Power Magazine, Cuba takes up Hydro Plan, Water Power Magazine, Januray 1, 2003. Accessed on: July 7, 2020. [Online]. Available: https://www.waterpowermagazine.com/ features/featurecuba-­takes-­up-­hydro-­plan/ R. Fujita, C. Scarborough, J. Diaz. Proceedings of the International Workshop on Clean Ocean Energy, Environmental Defense Fund, April 2008. Office of Energy Efficiency and Renewable Energy, How do wind turbines survive severe storms?, Energy.gov, June 20, 2017. Accessed on: July 7, 2020. [Online]. Available: https://www.energy. gov/eere/articles/how-­do-­wind-­turbines-­survive-­severe-­storms A.  Awasthi, A.  Shukla, M.  Manohar, C.  Dondariya, K.  Shukla, D.  Porwal, G.  Richhariya, Review on sun tracking technology in solar PV system, Energy Reports, Volume 6, 392–405. November 2020. G.Q. Lu, C.Y. Wang, T.J. Yen, X. Zhang, Development and characterization of a silicon-based micro direct methanol fuel cell, Electrochemica Acta 49 (2004) 821–828. A.  Bieberle-Hutter, D.  Beckel, U.P.  Muecke, J.L.M.  Rupp, A.  Infortuna, L.J.  Gauckler, Micro-­ Solid Oxide Fuel Cells as Battery Replacement, MST News, April 2005.

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A.  Michelen. Detailing MEMS Fabrication Techniques, Industrial Electronics, My 7, 2017. Accessed on: July 7, 2020. [Online]. Available: https://electronics360.globalspec.com/article/8638/detailing-­mems-­fabrication-­techniques#:~:text=Besides%20the%20techniques%20 introduced%20in,%2C%20wafer%20bonding%2C%20and%20others Renewable Energy World, La Revolucion Energetica: Cuba’s Energy Revolution, Issue 2 Volume 12, April 9, 2009. Accessed on: July 7, 2020. [Online]. Available: https://www.renewableenergyworld.com/2009/04/09/la-­revolucion-­energetica-­cubas-­energy-­revolution/#gre National geographic. Royters. https://education.nationalgeographic.org/resource/continental-shelf/# Y. Zhao, Power Shift in Cuba: Seven Reasons to Watch the Renewable Energy Sector in the PostFidel and Trump Era, Renewable Energy World, February 10, 2017. Accessed on: July 7, 2020. [Online]. Available: https://www.renewableenergyworld.com/2017/02/10/power-shift-in-cubaseven-reasons-to-watch-the-renewable-energy-sector-in-the-post-fidel-and-trump-era/#gref J. Pedraza, Solar Energy in Cuba: Current Situation and Future Development, Journal of Solar Energy Research Updates, June 2019. https://sustainabledevelopment.un.org/content/documents/13097Cuba.pdf https://www.worlddata.info/america/cuba/energy-consumption.php

Index

B Batteries, 28, 31, 33, 41–45, 55 Biofuels, 2, 5, 20–23 Biomass, 4, 5, 7, 19–24, 55 Biomass in Cuba, 4, 5, 23, 24, 55 Blackouts, 2, 3, 48 C Coal emissions, 9 Coal exploitation, 9, 22 Cuba electrical grid, 33, 51 Cuba resource potential, 16, 17 D Distributed generation, 47, 48, 55 Distributed generation in Cuba, 47, 48, 55 E Electrical grid, v, 3, 24, 33, 47–49, 52, 55 Electrical grid resiliency, 48, 49 Energy storage, vi, 2, 28, 33, 41–45, 55 Energy system in Cuba, v, vi, 3, 4, 47, 55 F Flooding in Cuba, 50 Fossil fuel reserves, 7 Fossil fuels, v, 2–5, 7, 8, 10, 18, 20–22, 37, 41, 45, 48, 51, 55

Fossil fuels in Cuba, v, 2–5, 20, 21, 41, 45, 48 Fuel cells, 22, 42–45, 55 G Geothermal, 35–38, 55 H History of energy in Cuba, 3 Hurricanes in Cuba, 13, 47, 48, 50, 51 Hydrogen, 9, 21, 22, 25, 41, 43–45, 55 Hydropower, 4, 5, 11, 12, 18, 19, 45 Hydropower in Cuba, 11–13, 18, 19, 45 L Lithium batteries, 42, 44 N Natural gas, 2, 5, 7, 9–10, 21, 22, 45 O Ocean-energy, 16–19, 45, 55 Oil exploitation, 18 P Power disruption, 50

© The Editor(s) (if applicable) and The Author(s), under exclusive license to Springer Nature Switzerland AG 2023 S. Petrovic, Renewable Energy in Cuba, SpringerBriefs in Energy, https://doi.org/10.1007/978-3-031-37473-9

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60 R Renewables in Cuba, 2–5, 12, 55 Revolucion Energetica, 5

Index Solar-hydrogen cycle, 45 T 2030 energy vision, 24

S Solar photovoltaics, 4, 5, 27, 34, 55 Solar PV in Cuba, 2, 5, 27, 28, 31–34, 41, 44, 45 Solar thermal, 24, 26, 27

W Wind in Cuba, 2, 5, 16, 17, 41, 45