RUNNING HEAD: A PHOTOVOLTAIC LITERATURE REVIEW
A Photovoltaic Literature Review
Emily T.C. Fitzsimmons University of Oklahoma GEOG 4523 001: Life Cycle Analysis Dr. Travis Gliedt April 26, 2020
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Introduction Nearly 200 years ago in France, a physicist named Edmond Becquerel observed the production of an electric current by radiant energy; this is the first recorded discovery of the photovoltaic effect. Inspired by Becquerel, Augustin Mouchot, a French mathematician, registered patents for solar-powered engines. In the following decades, people around the world applied for patents for solar-powered machines. Then in 1883, Charles Fritts installed the world’s first solar cell on a rooftop in New York City; his panels consisted of selenium covered in a thin coating of gold, operating at 1-2% efficiency. For comparison, modern solar cells typically have a 15-20% efficiency conversion rate. Just five years later, Russian scientist Aleksandr Stoletov invented the first photoelectric-based solar cell, which is how modern solar cells function. Many supporting inventions occurred in the following decades, including rotating mounts and the thermal battery (Chu & Tarazano, 2019). Finally, in the 1950s, Bell Laboratories replaced the traditionally used selenium with silicon, creating a solar cell with 6% efficiency. Though still very expensive, this breakthrough is considered the first practical solar panel. The construction of Solar One, a solar integrated building at the University of Delaware, along with the surge of the environmental movement popularized solar energy, encouraging investments for research and development as well as tax incentives and subsidies (Chu & Tarazano, 2019). Since then, solar energy has been accepted and praised by many as a renewable energy source with high potential, and it is cheaper than ever before. Yet solar still faces many obstacles in the fossil fuel status quo. As of 2019, only 1.8% of utility-scale electric generation in the United States was solar-powered (What is, 2020). Regarding Oklahoma, PlanOKC, the state capitol’s award-winning comprehensive plan does not
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mention the word “solar” once in its entirety. Additionally, as a lifetime resident, I know many who not only rely on oil for their livelihoods but also have inundated themselves into an Oklahoman culture that supports fossil fuels and objects to its proven damages. For this reason, I have selected photovoltaic solar panels as the topic of this life cycle assessment (LCA) literature review, in which I will review nine peer-reviewed journal articles and one master’s thesis that relate LCAs of photovoltaic solar panels. Altogether, the present literature asserts the advantages of photovoltaic to traditional energy and compares the various subcategories of photovoltaic; however, these LCAs largely exclude the social implications of photovoltaic with could aid in its advancement and acceptance, particularly when contrasted with fossil fuels. Literature Review To guide my research, I explored other literature reviews, including ones for LCAs outside photovoltaic panels. First, I found a literature review for photovoltaic panels, which provided helpful points to search for, though the critiques differ largely from my own. This report by Gerbinet, Belboom, and Léonard emphasizes the technical aspects often excluded from photovoltaic studies at the time, such as materials, efficiency rates, and balance of system parts – all components in a photovoltaic system except for the panel itself. Though such components are essential to the system, are typically omitted from LCAs; instead, researchers tend to report on energy payback times and indicators related to energy and climate change. Gerbinet, Belboom, and Léonard also argue that most studies fixate on silicon solar panels while ignoring new and emerging panel types like those that are organically produced. They also found that most LCAs used Eco-Indicator 99 and CML. In this review, the authors do not delve into their own research methodology; they simply state that they have summarized various works, analyzing the results
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and components of each LCA, such as the system boundary, functional unit, and methodology (Gerbinet et al., 2014). Additionally, I also considered the methodology of Arcese, Lucchetti, Massa, and Valente who perform a literature review using automatic text analysis of social life cycle assessments, or S-LCAs. They proved the usefulness of this tool as their results aligned with the otherwise known conclusion that there is no one approach to S-LCAs; rather, it is highly fragmented and lacks a clear position. The authors also argue that the automatic text analysis method is conducive to research because it is easily repeated to many articles (Arcese et al., 2016). Moreover, I read literature reviews further from my focus of photovoltaics and social impacts, which helped broaden my view. One analyzed LCAs on building refurbishment; this literature review’s methodology relied largely on categorization. The authors narrowed their scope only to LCAs that comprehensively discussed building renovation and refurbishment, paying special attention to the vocabulary and content of each before categorizing them appropriately. This method resulted in an organized and coherent review (Vilches, 2016). Lastly, Ferrara and De Feo’s literature review on LCAs of the wine sector practiced a method similar to that of Gerbinet, Belboom, and Léonard, focusing on the similarities in functional units, system boundaries, and other LCA components between the articles. However, I feel that the most significant part of Ferrara and De Feo’s research method was the visuals that organized and presented their findings, including an geographical scope pie charts, an comparative system boundary, graphs of environmental impact for each phase and type of wine, a scatter plot of carbon footprint for both conventional and organic viticulture, as well as an extensive table that compared each article. Overall, I felt all of these literature reviews provided
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guidance on how to perform and present my research methodology even though I didn’t use all the tenets of each. However, if nothing else, I believe I drew upon each of them in some way (Ferrara & De Feo, 2018). Methods I selected a research method most similar to that of Gerbinet, Belboom, and Léonard as well as Ferrara and De Feo because I organized my articles largely based on components of the LCA, such as the functional unit, geographical scope, and the software used. However, though my review deliberates the same topic, my critiques differed from Gerbinet, Belboom, and Léonard’s. Rather than focusing on the technical aspects of photovoltaic solar panels, my interest lies in the potential social advantages and detriments of photovoltaic cells. Unlike Gerbinet, Belboom, and Léonard, I also found that many of the articles discussed various photovoltaic materials instead of just silicon, and I found more researchers utilizing calculators outside of Eco-Indicator 99 and CML. I did not use automatic text analysis like Arcese, Lucchetti, Massa, and Valente; however, I did utilize multiple scholarly search engines, including Google Scholar and the Bizzell Library Advanced Search. When searching, I used various word strings, such as “LCA photovoltaic,” “life cycle assessment photovoltaic,” and “life cycle analysis photovoltaic.” Surprisingly, I did not find as many articles as expected. Overall, I read about twenty articles but only found eleven that really fit my need for an LCA on photovoltaic panels. In selecting the final ten, I first chose those that clearly stated their functional unit, software, calculator, database, and ISO use; I then chose the rest based on their clearness even without clarifying LCA components. Additionally, I chose to limit my final ten to articles published within the last twenty years as solar energy technology is a quickly changing field; however, I hardly found any
A PHOTOVOLTAIC LITERATURE REVIEW even that old. As a result, all of the chosen LCAs were published between 2007-2018. Figure 1. Literature Table
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Discussion Generally speaking, the articles have clear similarities in theme and attitude; however, they differ largely differ in most respects. Regarding the goal, they all seek to assess the impacts of photovoltaic systems. Most measure environmental impacts, but a few also include economic, social, or technical effects. Some also tack on the confirmation of framework legitimacy to their goals, including the life cycle sustainability assessment and life cycle sustainability dashboard discussed in Traverso, et al., as well as one made by Perez-Gallardo, et al. Moreover, there is theme in the functional units, which almost always involve either a module size or energy production (2012; 2013). The exception in this case was Kreiger’s master’s thesis, which used 1 kg of silane as the functional unit (2012). Meanwhile, the major gap in the LCAs’ goals occurs in the overall lack of social analysis; very few mention either positive or negative social impacts of photovoltaic modules, let alone analyze them. Likewise, these articles’ scopes vary widely. For one, Stylos and Koroneos study a largescale solar farm while other authors study individual panels; similarly, some compare several solar panel materials while others focus on just one type (2013). Unlike most of the LCAs, a few articles also include fossil fuel energy in their scope in order to compare renewable and nonrenewable energy. Another surprising difference in scope was insolation: Some authors chose to specify geographical scope based on the amount irradiance. For example, Mohr, et al., and Laleman, et al., both purposely used data from regions with low solar irradiance of 1,000 kWh/m2 whereas Kylili, et al., specifically discussed areas with high irradiance values (2009; 2010; 2017). On that note, geographical scope varied between studies, but there is a clear bias toward Europe. The most significant distinction in scope was the indicators used to measure impact, which ranged from a few environmental impact categories to fourteen characterization
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factors in one LCA. Despite all scope’s differences, however, there is a key theme in these studies’ system boundaries, all of which are either cradle-to-gate or cradle-to-use excepting Traverso’s work, which is gate-to-gate (Traverso et al., 2012). Notable gaps in scope include the lack of studies for locations outside of Europe and the United States as well as the little comparison to fossil fuel data. I found no themes or gaps regarding the calculators or software used; these included IMPACT 2002+, Eco-Indicator, ReCiPe, CML, IPCC, GaBi, SimaPro, USETOX, and others. However, there is a clear theme for databases: Nearly all the selected works used EcoInvent as the database. Additionally, several LCAs were limited by characterization factors – which tend to concentrate on energy and greenhouse gas emissions or economic indicators – as well as the constant changes in technology due to innovation. Kreiger also points out limitations in obtaining data for inputs from certain countries in the EcoInvent database, which would have affected most of these authors (2012). Furthermore, the authors commonly assume efficiency and losses, resource origins, system measurements, system lifetimes, product disposal methods, and transportation distances. Propositions In reviewing the literature, I found three major gaps. First, I found that the LCA literature on photovoltaics had a severe gap in the disposal of solar panels. Only the work by Kreiger thoroughly considered the end-life of solar panels, and she even restricted herself to a cradle to gate system boundary (2012). Even so, she had several great ideas involving recycling silane gas and post-consumer plastic by reinserting them back into the photovoltaic manufacturing process. If more intelligent minds examined the disposal and possible recycling of photovoltaic units, not only could potentially toxic waste be diverted from landfills but the need for virgin materials
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would be reduced. As the extraction and refinement materials is agreed to be extremely destructive – even for a renewable energy – this would vastly improve solar energy production. Secondly, to my surprise, though the LCAs acknowledge that solar is less impactful on the environment than traditional energy sources, very few of them actually contrast the photovoltaic data with fossil fuel data. Rather, most of the LCAs compare different types of photovoltaic panels based on materials and design to determine which type of solar cell is best. Clearly, sustainability professionals know that solar energy is better than coal or oil, but as scientists, we should still provide clear evidence for those who overwhelmed with opinions and incomplete truths. Lastly, hardly any of the LCAs included the social implications of photovoltaic solar cells. Most concentrated on the environmental or economic aspects, which are always necessary and important; however, true sustainability follows a triple-bottom-line. Examinations of photovoltaic sustainability should, therefore, include environmental health, economic well-being, and equity, especially as the endorsement of solar energy relies on sustainability. In particular, the literature has a massive gap in public health influences, which is one of the solar energy’s greatest advantages. Overall, researchers should refocus photovoltaic LCAs to include social implications from cradle to cradle with the goal of convincing those who presently stand with nonrenewable energy to support solar. Many of the current LCAs already include the energy payback time, which is a necessary tenet of this persuasion; however, they should also account for the public health influences of photovoltaic cells in production, use, and disposal, including both negative and positive effects for a full picture. In order to support this transition to solar, all LCAs should also compare the triple-bottom-line effects of solar to those of fossil fuel energy sources so that
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people can realize the disadvantages of the fossil fuel economy compared to future possibilities in renewable energy. Conclusion Just as the literature reviewed has limitations, I have my own as well, including the inaccessibility to some reports as well as the constraints of just one person performing all the research and writing. In summary, though LCA literature illustrates clear advantages of a variety photovoltaic panels, the literature still contains major gaps, most important of which is the largely absent discussion of social benefits and detriments of photovoltaic cells, which could aid in its acceptance and advancement. Solar energy faces a formidable opponent in fossil fuel because of those exploiting coal, oil, and those dependent on them, but LCAs are a potentially powerful tool in educating and empowering everyday citizens and researchers on solar power. By conducting LCAs, we can learn about the necessary resources and byproducts of energy technologies to discover which has the least detrimental inputs and the most beneficial outputs for people, nature, and the economy. Already, the LCAs considered in this literature review create an inclusive and edifying picture, but I recommend that future research address the gaps discussed above: broader geographical scope, a full cradle-to-grave or cradle-to-cradle system boundary, consistent comparison with fossil fuel, and social implications. It is time for the next historical breakthrough of solar energy.
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