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Assessment of the ecological lifetime of photovoltaic systems considering aging effects, end-of-life and early replacement

Herceg, Sina (2024)
Assessment of the ecological lifetime of photovoltaic systems considering aging effects, end-of-life and early replacement.
Technische Universität Darmstadt
doi: 10.26083/tuprints-00026735
Ph.D. Thesis, Primary publication, Publisher's Version

Abstract

Photovoltaic (PV) systems are crucial for a clean energy transition. Still, their massive deployment in the coming years will consume significant amounts of energy and resources. Emissions from the production of solar energy systems have been constantly decreasing in the past years. However, not only production emissions but also factors like lifetime and energy yield are decisive for the life cycle environmental impact of PV electricity. Previous Life Cycle Assessment (LCA) studies focus mainly on the quantification of primary energy and resource use during PV production, whereas their use and end-of-life phase and the regarding impact on the overall environmental performance of PV electricity are rarely investigated. For example, aging and degradation during use phase which can be strongly dependent on site-specific conditions like a corrosive atmosphere, are affecting the systems lifetime and therefore its environmental footprint. Further, the end-of-life treatment of PV modules is gaining relevance for quantifying the emissions of PV electricity due to increasing amounts of PV module waist in the coming years. Hence, to assess the emissions over the whole life cycle of a PV system it is important to also be able to quantify the aforementioned impacts since they can have a strong effect on its overall lifecycle emissions. This work aims to investigate the environmental impact of PV systems throughout their lifecycle, addressing the research gaps identified above. The influence of performance degradation, end-of-life (EoL) treatment as well as actual operational time on the environmental footprint of PV electricity and therefore the optimal ecological lifetime of PV systems is assessed using LCA methodology. Three sub-questions are explored in separate peer-reviewed journal articles: 1) The impact of different recycling approaches for PV modules, highlighting the potential for improved environmental performance with dedicated recycling technologies. 2) The influence of regionalized degradation patterns on greenhouse gas emissions from PV electricity, revealing location and temperature dependent variations in emissions. 3) The calculation of the earliest and the optimum point to maximize the ecological benefits of early PV system replacement (repowering), emphasizing the benefits of repowering when combined with recycling and increased peak power. The results show that all the mechanisms under study can significantly influence the life cycle environmental emissions of a PV system. For example, dedicated recycling can reduce CO2-emissions by up to 4%, despite the higher efforts for waste treatment. Also, using non-linear degradation rates instead of a linear degradation rate of 0.7% results in a variation of up to -4 % to +6 % in CO2-emissions per kWh of produced electricity. Moreover, in regions where climatic stressors like temperature, humidity and corrosion are high, the CO2-emissions per kWh almost double when climate-specific degradation rates are used. Finally, it could be shown that the premature replacement of PV-modules can be environmentally beneficial under certain conditions, especially in combination with dedicated recycling. By using the results from all three studies, the assessment of PV life cycle emissions is improved and, in doing so, PV deployment strategies can be optimized. Future research should focus on integrating the here presented methodologies and results, enabling site-specific quantification of PV system life cycle emissions and the development of improved end-of-life management strategies to enhance sustainability.

Item Type: Ph.D. Thesis
Erschienen: 2024
Creators: Herceg, Sina
Type of entry: Primary publication
Title: Assessment of the ecological lifetime of photovoltaic systems considering aging effects, end-of-life and early replacement
Language: English
Referees: Schebek, Prof. Dr. Liselotte ; Linke, Prof. Dr. Hans-Joachim
Date: 12 March 2024
Place of Publication: Darmstadt
Collation: IX, 47, XXXVII Seiten
Refereed: 29 January 2024
DOI: 10.26083/tuprints-00026735
URL / URN: https://tuprints.ulb.tu-darmstadt.de/26735
Abstract:

Photovoltaic (PV) systems are crucial for a clean energy transition. Still, their massive deployment in the coming years will consume significant amounts of energy and resources. Emissions from the production of solar energy systems have been constantly decreasing in the past years. However, not only production emissions but also factors like lifetime and energy yield are decisive for the life cycle environmental impact of PV electricity. Previous Life Cycle Assessment (LCA) studies focus mainly on the quantification of primary energy and resource use during PV production, whereas their use and end-of-life phase and the regarding impact on the overall environmental performance of PV electricity are rarely investigated. For example, aging and degradation during use phase which can be strongly dependent on site-specific conditions like a corrosive atmosphere, are affecting the systems lifetime and therefore its environmental footprint. Further, the end-of-life treatment of PV modules is gaining relevance for quantifying the emissions of PV electricity due to increasing amounts of PV module waist in the coming years. Hence, to assess the emissions over the whole life cycle of a PV system it is important to also be able to quantify the aforementioned impacts since they can have a strong effect on its overall lifecycle emissions. This work aims to investigate the environmental impact of PV systems throughout their lifecycle, addressing the research gaps identified above. The influence of performance degradation, end-of-life (EoL) treatment as well as actual operational time on the environmental footprint of PV electricity and therefore the optimal ecological lifetime of PV systems is assessed using LCA methodology. Three sub-questions are explored in separate peer-reviewed journal articles: 1) The impact of different recycling approaches for PV modules, highlighting the potential for improved environmental performance with dedicated recycling technologies. 2) The influence of regionalized degradation patterns on greenhouse gas emissions from PV electricity, revealing location and temperature dependent variations in emissions. 3) The calculation of the earliest and the optimum point to maximize the ecological benefits of early PV system replacement (repowering), emphasizing the benefits of repowering when combined with recycling and increased peak power. The results show that all the mechanisms under study can significantly influence the life cycle environmental emissions of a PV system. For example, dedicated recycling can reduce CO2-emissions by up to 4%, despite the higher efforts for waste treatment. Also, using non-linear degradation rates instead of a linear degradation rate of 0.7% results in a variation of up to -4 % to +6 % in CO2-emissions per kWh of produced electricity. Moreover, in regions where climatic stressors like temperature, humidity and corrosion are high, the CO2-emissions per kWh almost double when climate-specific degradation rates are used. Finally, it could be shown that the premature replacement of PV-modules can be environmentally beneficial under certain conditions, especially in combination with dedicated recycling. By using the results from all three studies, the assessment of PV life cycle emissions is improved and, in doing so, PV deployment strategies can be optimized. Future research should focus on integrating the here presented methodologies and results, enabling site-specific quantification of PV system life cycle emissions and the development of improved end-of-life management strategies to enhance sustainability.

Alternative Abstract:
Alternative abstract Language

Der weltweite Ausbau der Photovoltaik (PV) Kapazitäten ist ein wichtiger Bestandteil der Wende hin zu einer klimafreundlicheren Energieversorgung. Dennoch wird der massive Einsatz erneuerbarer Energietechnologien in den kommenden Jahren große Mengen an Energie und Ressourcen verbrauchen. Die Emissionen aus der Produktion von Solarenergiesystemen sind in den letzten Jahren stetig gesunken. Allerdings sind nicht nur die Produktionsemissionen, sondern auch Faktoren wie Lebensdauer und Energieertrag entscheidend für die Umweltwirkungen der nutzbaren elektrischen Energie. Bisherige Ökobilanzstudien konzentrieren sich hauptsächlich auf die Quantifizierung des Primärenergie- und Ressourcenverbrauchs während der Herstellung der PV Module, wohingegen die Nutzungs- und die End-of-Life-Phase, sowie die diesbezüglichen Auswirkungen auf die Gesamtumweltleistung von PV-Strom selten untersucht werden. So wirken sich beispielsweise Alterung und Degradation während der Nutzungsphase, die stark von standortspezifischen Bedingungen wie einer korrosiven Atmosphäre abhängen können, auf die Lebensdauer und den Gesamtertrag der Systeme und damit auf den ökologischen Fußabdruck der elektrischen Energie aus. Da in den kommenden Jahren immer mehr PV-Module ihr Lebensende erreichen werden, gewinnen das Recycling und die Verwertung der Module an Bedeutung für die Quantifizierung der Emissionen von PV-Strom. Um die Emissionen über den gesamten Lebenszyklus einer PV-Anlage zu bewerten, ist es daher wichtig, auch diese Auswirkungen zu quantifizieren, da sie die Gesamtemissionen über den Lebenszyklus stark beeinflussen können. Diese Arbeit zielt darauf ab, die Ökobilanz von PV Anlagen über ihren gesamten Lebenszyklus zu untersuchen und damit die oben genannten Forschungslücken zu schließen. Der Einfluss von Degradation, Behandlung am Lebensende sowie der tatsächlichen Betriebszeit auf den ökologischen Fußabdruck des erzeugten Stromes und damit die ökologisch optimale Lebensdauer von PV-Systemen wird mittels Life Cycle Assessment (LCA) bewertet. Die Thematik wird dabei in drei separaten Zeitschriftenartikeln untersucht: 1) Die Auswirkungen verschiedener Recyclingansätze (End-of-Life-Management) für PV-Module, wobei das Potenzial für eine verbesserte Umweltleistung durch spezielle Recyclingtechnologien hervorgehoben wird. 2) Der Einfluss regionaler Degradationsmuster auf die Treibhausgasemissionen von PV-Strom, wobei orts- und temperaturabhängige Unterschiede in den Emissionen identifiziert werden. 3) Die Berechnung des frühesten sowie des optimalen Zeitpunkts für einen Austausch von PV-Modulen (Repowering) zur Maximierung der ökologischen Vorteile, wobei die Vorteile des Repowerings in Kombination mit Recycling und erhöhter Anlagenleistung hervorgehoben werden. Die Ergebnisse zeigen, dass alle der untersuchten Mechanismen über den gesamten Lebenszyklus der Systeme einen erheblichen Einfluss auf die Emissionen von PV-Strom haben können. So können beispielsweise durch gezieltes Recycling die CO2-Emissionen, trotz eines höheren Aufwands für die Abfallbehandlung, um bis zu 4% gesenkt werden. Auch die Verwendung nichtlinearer Degradationsraten anstelle einer linearen Degradationsrate von 0,7% in der Berechnung führt zu einer Veränderung der CO2-Emissionen um bis zu -4 % bis +6 %. Außerdem verdoppeln sich in Regionen mit hohem klimatischem Stress, die CO2-Emissionen pro kWh, wenn klimaspezifische Degradationsmuster in der Berechnung berücksichtig werden. Schließlich konnte gezeigt werden, dass das Repowering von PV-Modulen unter bestimmten Bedingungen ökologisch vorteilhaft sein kann, insbesondere in Verbindung mit spezialisiertem Recycling. Die Ergebnisse aller drei Studien tragen dazu bei, die Bewertung der Lebenszyklusemissionen von PV-Anlagen zu verbessern. Auf diese Weise können Strategien für den Ausbau von PV-Anlagen optimiert werden. Künftige Forschungsarbeiten sollten sich auf die Integration der hier vorgestellten Methoden und Ergebnisse konzentrieren, um eine standortspezifische Quantifizierung der Lebenszyklusemissionen von PV-Strom und die Entwicklung verbesserter Strategien für das End-of-Life-Management zur Verbesserung der Nachhaltigkeit zu ermöglichen.

German
Status: Publisher's Version
URN: urn:nbn:de:tuda-tuprints-267359
Classification DDC: 500 Science and mathematics > 500 Science
600 Technology, medicine, applied sciences > 624 Civil engineering and environmental protection engineering
Divisions: 13 Department of Civil and Environmental Engineering Sciences
13 Department of Civil and Environmental Engineering Sciences > Institute IWAR
13 Department of Civil and Environmental Engineering Sciences > Institute IWAR > Material Flow Management and Resource Economy
Date Deposited: 12 Mar 2024 12:47
Last Modified: 14 Mar 2024 11:01
PPN:
Referees: Schebek, Prof. Dr. Liselotte ; Linke, Prof. Dr. Hans-Joachim
Refereed / Verteidigung / mdl. Prüfung: 29 January 2024
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