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2022 | Buch

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Sustainable Solar Electricity

verfasst von: Antonio Urbina

Verlag: Springer International Publishing

Buchreihe : Green Energy and Technology

Enthalten in: Springer Professional "Wirtschaft+Technik" , Springer Professional "Technik" , Springer Professional "Wirtschaft"

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Über dieses Buch

This book provides a detailed life cycle assessment of photovoltaic technologies in order to analyse the environmental and socioeconomic impacts that a large deployment of solar photovoltaic systems will produce in the near future.

Including both commercial and emerging technologies, the book presents the energy and materials requirements to manufacture solar electricity power systems at the order of the TeraWatt scale deployment as is envisaged by the International Renewable Energy Agency (IRENA) for the near future. It discusses current manufacturing practices and how these may be adapted in the future including:

reuse and recycling of components and materials; raw material supply chains to the manufacturing factories; and end-of-life procedures including recycling and landfilling of modules.

The environmental and socioeconomic impacts of solar energy are analysed in detail, providing recommendations for standardization and regulations in order to make photovoltaic technologies, both current and emerging, a really sustainable alternative for the supply of “greener” electricity.

Inhaltsverzeichnis

Frontmatter

Introduction

Frontmatter

Chapter 1. Scenarios for Solar Electricity at the TeraWatt Scale

Abstract

The energy transition is accelerating the deployment of new renewable energy capacity. In particular, photovoltaic installed cumulative capacity reached 760.4 GW_DC at the end of 2020, with 139.4 GW_DC installed in a single year despite the economic shock produced by the COVID19 pandemia. On the contrary, part of the public economic expenditure approved to boost the economic recovery is being invested in building new renewable energy capacity. The different scenarios envisaged by the International Energy Agency indicate a strong increase in the share of solar electricity in future energy production worldwide; in particular, the Net Zero Emissions by 2050 scenario points to reaching almost 5 TW of photovoltaic cumulative capacity in 2030 and surpassing 10 TW in 2040. This colossal growth will require the annual manufacture of millions of solar photovoltaic modules and a diversification of photovoltaic technologies in a market dominated by crystalline silicon technology. Although solar radiation is a inexhaustible renewable energy source, the future demand of raw materials and the energy required to manufacture the photovoltaic cells and the environmental impacts of production and operation of photovoltaic systems demands a detailed sustainability analysis of solar electricity.

Antonio Urbina

Chapter 2. Photovoltaic Technology

Abstract

The photovoltaic effect, observed experimentally for the first time in 19th century, required the development of the concept of “light quanta” (photons) and quantum theory to be explained theoretically. Furthermore, its practical application was only possible after the use of semiconductors and a deep understanding of solid state physics that was achieved in the first half of 20th century. The first solar cell to reach a power conversion efficiency higher than 5% was fabricated in 1954: it demonstrated the feasibility of generating solar electricity at large scale for power applications. The fundamental steps of photocurrent and photovoltage generation are explained in this chapter at an introductory level with a practical approach oriented to define the operational parameters that characterize the output of photovoltaic cells and modules; the common basic structure of any photovoltaic cell is described and the differences between the main technological families are presented (crystalline silicon, thin film, III-V, and emerging organic and hybrid technologies).

Antonio Urbina

Chapter 3. Assessment of Sustainability

Abstract

The concept of sustainability is broadly used but lousily defined. Sustainability comprises several dimensions and it is still subject of many academic discussions. Nevertheless, less ambitious approaches enable the possibility to quantify the environmental and socio-economic impacts of any product or service. A powerful and well defined tool (regulated by ISO14040 and ISO14044 standards) is Life Cycle Assessment: its methodology and main phases (definition of functional unit and scope, life cycle inventory, impact assessment and interpretation) are explained in this chapter with a focus on the assessment of energy technologies, and including a summary of the most used Life Cycle Impact Assessment methodologies that are currently available. A broader approach towards life cycle “sustainability” assessment requires the inclusion of tools to evaluate socio-economic impacts, such as life cycle costing and total cost of ownership, levelized cost of the produced energy or product environmental footprint that are also presented in this chapter.

Antonio Urbina

Life Cycle Assessment of Solar Electricity

Frontmatter

Chapter 4. Production of PV Modules

Abstract

The manufacturing processes of the different photovoltaic technologies are presented in this chapter: Crystalline silicon solar cells (both mono- and multi-crystalline), including silicon purification and crystallization processes; thin film solar cells (amorphous silicon, cadmium telluride, chalcopyrites and kesterites); III-V solar cells, and emerging solar cells (organic, dye-sensitized, perovskites and others). The fabrication steps from cells to modules are also presented. The broad range of industrial processes are analysed with the aim to facilitate the compilation of life cycle inventories in the manufacturing phase of a broader life cycle assessment, including the use of materials that are embedded in the final cells and modules, the use of substances that are used in the manufacturing process and importantly, the energy consumption of every process. The challenges for an increased sustainability of all manufacturing steps of well established commercial technologies and emerging technologies are discussed from the point of view of the efficient use of materials, improved processes and recovery and reuse of substances in the manufacturing lines.

Antonio Urbina

Chapter 5. The Limits of Raw Materials Embedded in PV Modules

Abstract

The materials used to fabricate solar modules and ultimately to produce solar electricity with all photovoltaic technologies are listed. Silicon, the base material for the most extended photovoltaic technology with a market share higher than 90% that is expected to remain high, is the most abundant material on Earth’s crust and it is taken as a reference for the evaluation of abundance of other elements. Nevertheless, other materials also embedded in silicon solar modules may pose a risk: silver or tin are used for interconnections and are materials subject to supply and demand tensions; other technologies, such as cadmium telluride face a higher risk due to the scarcity of tellurium. III-V technologies and emerging technologies strongly rely on the use of indium, a strategic element that is required for the manufacture of transparent conducting oxides in the electronic industry and reliable alternatives to indium are being developed. Other issues related to the use of toxic substances in the cells processing points to strong requirements for health and safety for workers in the factories. The limits to massive solar electricity deployment that may arise from the use of materials are analysed in this chapter.

Antonio Urbina

Chapter 6. The Energy Balance of Solar Electricity

Abstract

The production of solar electricity requires the investment of a certain amount of energy, either during the manufacturing phase of the photovoltaic systems or during the operational and end-of-life phases. The energy balance throughout the whole life cycle is a critical parameter for the evaluation of the sustainability of solar electricity. In this chapter, the embedded energy, i. e. the energy required to manufacture the photovoltaic systems are presented for all photovoltaic technologies; between 3.93MJ/W\(_p\) and 4.62MJ/W\(_p\) are required for mono-crystalline and multi-crystalline silicon manufacture, similar for thin film technologies and an even broader range from 2.9MJ/W\(_p\) to 5.7 MJ/W\(_p\) for organic and hybrid technologies. In all cases, the embedded energy per peak power depends on power conversion efficiency and it is subject to strong variations. The next step is the calculation or measurement of the electricity produced by an operational photovoltaic system, taking into account environmental conditions of the geographical location where the system is operating; the final balance is expressed as energy pay back time which ranges between a few years for commercial silicon technologies with lifetimes of 25 years to a few months for emerging organic and hybrid technologies with much shorter lifetimes.

Antonio Urbina

Chapter 7. Impacts of Solar Electricity

Abstract

The life cycle assessment of photovoltaic technologies includes the important step of impact assessment of all the contributions of the life cycle inventory (materials or energy embedded in the modules and required for the manufacturing processes). Depending on the impact assessment methodology, different categories can be analysed, the focus is on commercial technologies comprising more than 99% of current market (crystalline silicon and thin film) that are analysed in detail with the same methodology (ReCiPe) in fifteen categories and more broadly compared with other energy technologies. Despite crystalline silicon solar cells being the dominant technology with more than 90% of market share, either already commercial thin film or emerging technologies may provide the same electricity (considered as a functional unit of life cycle assessment) with lower environmental impacts. Size dependant impacts are becoming important and creating certain social alarm due to land occupation in competition with other land uses, a section analyses land occupation and alternative solutions to conventional large PV plants such as agrivoltaics. Finally different results for life cycle assessment of emerging organic and hybrid technologies are presented.

Antonio Urbina

Chapter 8. Recycling and End of Life of PV Technologies

Abstract

The end of life of photovoltaic systems will require adequate strategies at a global level when the massive amount of modules that have been deployed in recent years reaches the end of its operational life and will have to be dismantled and treated as electronic waste. According to estimations, up to 800 thousand tonnes in 2020 and more than 7 billion tonnes in 2030 of PV modules will reach its end of life. Different options can be considered: reuse of modules that still deliver enough power, recycling of modules and recovery of parts or materials, land-filling, or a combination of them. Techniques to recycle silicon and thin film modules are already available and implemented in several recycling plants, but still with low capacity and low percentage of recovered materials. Improved techniques, regulations and logistics for end of life of PV systems and further research and development are strongly needed. These advances may lead to a feedback from recycling strategies to original manufacture lines that should incorporate “design for recycling” approaches that reduce end of life impacts and maximizes materials and components recovery.

Antonio Urbina

Chapter 9. Balance of System (BoS) and Storage

Abstract

All the components of a photovoltaic system that are not photovoltaic modules are considered “Balance of System” (BoS) components. From a life cycle assessment perspective, BoS is becoming an important contributor to impacts, both environmental and economic, with an increasing share of impacts compared to the contribution of modules. In this chapter, an overview of all required BoS components for an operational photovoltaic system and its life cycle assessment are presented: mounting sytems, cabling, regulators, inverters, transformers; for roof-top or ground systems, for DC or AC electricity supply. Although most new installed capacity is grid connected, electricity storage is becoming a key component, for stand alone systems, but also for grid stabilisation when renewable sources are the main electricity suppliers to the grid. Two sections are devoted to a brief presentation of electricity storage and an introduction to life cycle assessment methodology for batteries (in some cases including a second life) and results of impacts for lithium ion battery technologies, the most broadly used today for photovoltaic systems which include electricity storage.

Antonio Urbina

Beyond Life Cycle Assessment: Socioeconomics and Geopolitics of Solar Electricity

Frontmatter

Chapter 10. Socioeconomic Impacts of Solar Electricity

Abstract

This chapter presents the socioeconomic impacts of solar electricity and therefore goes beyond conventional life cycle assessment methods with the aim to advance towards a more global sustainability assessment, including future employment opportunities. The cost of solar electricity is an example of a steady learning curve, reaching costs below 1 USD per Watt of nominal power at system level since 2019 (both for silicon and for thin film technologies), with average learning rates in the past fifteen years of 31% for crystalline silicon and 29% for thin film technologies respectively. This impressive path has pushed down the cost of the produced solar electricity to prices that are already cheaper than grid electricity, reaching an average cost of 0.057 USD/kWh in 2020. Any investment in research for the improvement of already good parameters (power conversion efficiency, lifetimes or higher recyclability) needs to be lower than the marginal economic benefit that can be achieved with the obtained technical improvement, which is usually low, posing a risk for future technological advancement of well established technologies.

Antonio Urbina

Chapter 11. Standardization and Regulations for PV Technologies

Abstract

Three regulatory frameworks are presented in this chapter. First, an overview of active international technical standards related to photovoltaic technologies or to life cycle assessment methodologies. The International Organization for Standardization and the International Electrotechnical Commission are the two organizations which provides the main framework for standardization of photovoltaic technologies; other regional (European Union) or local (United States of America, United Kingdom, Japan) provide additional standards that are also presented. A second section is devoted to an overview of the regulatory frameworks for recycling and end of life of photovoltaic modules; a few standards are devoted to this important issue and only the European Union with the Waste Electrical and Electronic Equipment (WEEE) directive provides a regulatory framework in this regard, with other countries lagging behind, although with interesting proposals in the make. Finally, ecolabelling, ecodesign and approaches for Green Public Procurement policies and how they are applied to photovoltaic technologies are presented and analysed.

Antonio Urbina

Chapter 12. Solar Electricity and Globalization

Abstract

Access to energy and human development have a strong correlation; initial access produces a steep increase in the Human Development Index (HDI), requiring around 40GJ/year per cápita to achieve a “decent standard of living”. Rural electrification in developing countries with stand-alone photovoltaic systems has been an important contributor to guarantee full electrification in several countries, but many, specially in sub-Saharan Africa, still require an important effort since more than half of the population (on average) lacks access to electricity, with still ten countries having access lower than 20%. Although most of new photovoltaic capacity has been installed in countries with 100% electrification in grid connected photovoltaic systems, the demand for stand-alone and minigrid systems remains high and requires support policies that go beyond conventional market approaches. This task, together with the urgent need for climate change mitigation where solar electricity will be an important contributor demands new approaches for the quantitative study of sustainability that are complementary to standard Life Cycle Assessment studies. Global challenges require global policies and decision making that should be assisted by up-to-date scientific knowledge including risk assessment of the geopolitics of photovoltaics, where China is playing and central role.

Antonio Urbina

Backmatter

Titel: Sustainable Solar Electricity
verfasst von: Antonio Urbina
Verlag: Springer International Publishing
Electronic ISBN: 978-3-030-91771-5
Print ISBN: 978-3-030-91770-8
DOI: https://doi.org/10.1007/978-3-030-91771-5