(660h) Environmental Sustainability Assessment of Emerging Renewable Energy Technologies | AIChE

(660h) Environmental Sustainability Assessment of Emerging Renewable Energy Technologies


Khalifa, S. - Presenter, Drexel University
Decarbonizing the global economy, particularly energy generation sectors, is a top priority to curb impending consequences of anthropogenic global warming. Rapid deployment of renewable energy (RE) technologies, such as solar photovoltaics (PV), wind turbine generators and battery storage, is critical to provide low-cost, reliable, and sustainable energy source to reach net-zero carbon pledges by worldwide governments (e.g., Paris accord). This rapid growth in RE systems deployment will not only bias demand to specific material supply chains (e.g., Aluminum, Copper, Silicon, Glass, Lithium) but will also create an emerging waste stream at the end of technology useful lifetime that needs treatment. As research efforts grow to develop high performing, low-cost technology designs, it is equally important to understand the implications of such technology designs on the environment and human health to ensure long-term environmental, social, and economic sustainability.

In my doctoral thesis, I use sustainability assessment tools such as process-based life cycle analysis (LCA; attributional and consequential), dynamic material flow analysis (DMFA) and risk assessment (RA) to quantify the environmental and human health impacts of emerging solar PV technologies to meet projected electricity demand. In LCA, I combine detailed understanding of PV module designs and operation with process modelling and scale-up concepts to build cradle-to-grave life cycle inventories for conducting industry-relevant environmental impact assessments. LCA results span a wide range of impact categories including life cycle carbon emissions, cumulative energy demand, human health toxicity, land change, acidification potential, water use and various other damage categories. DMFA is a powerful tool to quantify material stocks and flows in their cradle-to-cradle life cycles over time and thus overcomes the static temporal limitation of traditional LCA methodology. DMFA can provide insights into systemic material waste reduction, raw material conservation and opportunities to transition into a circular value chain instead of take-make-use-dispose linear model. Risk and exposure assessment can reveal information about exposure limits of different chemicals during the fabrication of PV modules and thus could provide useful feedback to build engineering controls, size ventilation systems and plan manufacturing capacities to ensure labor workplace safety. Each sustainability assessment tool provides tailored feedback to different stakeholders to enable more sustainable decisions around technology deployment and to ensure long-term supply chain resiliency and security.

I used sustainability assessment tools to evaluate emerging issues for solar PV technologies including state-of-the art perovskite photovoltaic modules and end-of-life of most deployed crystalline silicon photovoltaics. The first research question I answered was related to assessing the environmental impacts of chemical precursors that could be used in perovskite photovoltaic module fabrication. Prior LCA literature based on laboratory scale reported outsized environmental impacts of high performing perovskite alloys, raising concerns over their commercial potential. By employing rigorous process synthesis, design, scale-up and integration, we found out that the climate change, cumulative energy demand and human toxicity are all similar for all candidate precursors and therefore perovskite formulation should be chosen based on their efficiency and stability. These findings were published in ACS Sustainable Chemistry and Engineering Journal as a first author. This work also won the best student presentation award at the 2020 AIChE Engineering Sustainable Development Conference and was nominated to best paper award in 2021 IEEE Photovoltaics Specialists Conference.

Another research question I answered is about assessing the circularity potential of end-of-life crystalline silicon solar photovoltaic modules. I designed open-source sustainability framework that quantifies the stocks and flows of PV materials in their cradle-to-cradle life cycles based on PV electricity generation from 2000-2100. The Photovoltaic Dynamic Material Flow Analysis (PV DMFA) model incorporates design, operational, temporal, and spatial parameter space that allows users to capture the evolution of PV technology with time and identify opportunities to reduce material waste and promote symbiosis between EOL recovery systems and PV manufacturing and module assembly stages. We used PV DMFA to study PV glass and aluminum frames which account for about 85% of the PV module weight. Our results indicate that the soaring PV demand is likely to require flat glass manufacturing capacity expansions many times the existing capacity to meet projected electricity demand. We found out that minimally intrusive recycling techniques (e.g., thermal, or mechanical/thermal) could retain PV glass sheet purity and increases their chances for closed loop recycling. We also found out that initial deployment parameters, particularly those related to system reliability and performance, can have a sizeable impact on life cycle resource efficiency. This work is sponsored by the National Renewable Energy Laboratory (NREL) and was nominated to best student presentation award in 2021 IEEE Photovoltaics Specialists Conference. As of now, first authored journal article is pending release upon completion of peer review process. PV DMFA software will also be released as open-source tool for the public to evaluate their scenarios of interest.

Conducting ex-ante sustainability assessments for emerging technologies require careful process planning, scale-up and deep understanding of proxy industrial practices to generate industry-relevant impact assessment results. Combined with detailed hotspot and uncertainty analysis, results could overcome data availability limitations commonly experienced due to technology immaturity or business-sensitive cases.

In my postdoctoral training, I hope to apply my doctoral research skills to a new relevant problem in a similar field or potentially learn new relevant experimental or modelling skills. I have enough flexibility to dive into unknown problems with limited data and be engaged in open-ended challenges. I hope that my postdoctoral training will prepare me for a career in energy and environmental research to be able to partially contribute to tackling global warming.

Research Interests: My research interests span a wide range of sustainability topics including conducting life cycle assessments, resource efficiency modelling, and designing processes tailored for renewable energy system technologies (e.g., fabrication lines, recycling, and material reclamation processes). I have strong interest in solar photovoltaic technologies particularly in the areas of module reliability and failure analysis, systems engineering, recycling, and PV value chain. I also have potential interest in wind turbine blades and electric vehicle (EV) batteries. I envision my postdoctoral training will continue my current path of conducting sustainability and circularity assessment studies for renewable energy technologies and/or learn new analysis and experimental techniques within solar PV field to quantify and understand their energy yield, system durability, system/component reuse/repurposing and their ability to withstand harsh weather conditions in the field.

Keywords: Life cycle assessment, Solar photovoltaics, Circular economy, Renewable energy technologies, Decarbonization, Supply chain sustainability.


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