• Energy Research

This paper presents a detailed life-cycle assessment of the greenhouse gas emissions, cumulative demand for total and non-renewable primary energy, and energy return on investment (EROI) for the domestic electricity grid mix in the U.S. state of California, using hourly historical data for 2018, and future projections of increased solar photovoltaic (PV) installed capacity with lithium-ion battery energy storage, so as to achieve 80% net renewable electricity generation in 2030, while ensuring the hourly matching of the supply and demand profiles at all times. Specifically—in line with California’s plans that aim to increase the renewable energy share into the electric grid—in this study, PV installed capacity is assumed to reach 43.7 GW in 2030, resulting of 52% of the 2030 domestic electricity generation. In the modelled 2030 scenario, single-cycle gas turbines and nuclear plants are completely phased out, while combined-cycle gas turbine output is reduced by 30% compared to 2018. Results indicate that 25% of renewable electricity ends up being routed into storage, while 2.8% is curtailed. Results also show that such energy transition strategy would be effective at curbing California’s domestic electricity grid mix carbon emissions by 50%, and reducing demand for non-renewable primary energy by 66%, while also achieving a 10% increase in overall EROI (in terms of electricity output per unit of investment).

© 2023 The Authors. Published by Elsevier Ltd on behalf of International Solar Energy Society. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/). This document is the Accepted version of a Published Work that appeared in final form in Solar Energy. To access the final edited and published work see https://doi.org/10.1016/j.solener.2023.04.001 As announced in the European Green Deal, it is critical to decarbonise the European Union energy system in order to reach climate objectives by 2030 and 2050. According to the REPowerEU plan, photovoltaics (PV) is expected to play a major role in this. Therefore, it is crucial to ensure that newly installed PV modules in the EU are affordable and competitive on the one hand and environmentally friendly on the other. Bearing in mind that the environmental hotspots for PV modules mainly occur during the manufacturing phase, the aim of the paper is to develop a fully-fledged and adapted methodology for calculating the carbon footprint of PV modules, with particular regard to the manufacturing and shipping phases, following a cradle-to-gate approach based on the Product Environmental Footprint Category Rules for PV modules. The implications of requirements for the carbon footprint of PV modules, under the existing legal framework of the Ecodesign Directive, are also discussed.

AbstractPerovskite photovoltaics reached record efficiencies in the laboratory, and if sustainably commercialized, they would accelerate a green energy transition. This article presents the development of life cycle inventory material and energy databases of four most promising single‐junction and three tandem scalable perovskite systems with assumptions regarding scalable production validated by industry experts. We conducted comprehensive “ex ante” life cycle analysis (LCA) and net energy analysis, analyzing their cumulative energy demand, global warming potential profiles, energy payback times, and energy return on investment (EROI). LCA contribution analysis elucidates the most impactful material and process choices. It shows that solution‐based perovskite manufacturing would have lower environmental impact than vapor‐based methods, and that roll‐to‐roll (RtR) printing offers the lowest impact. Among material choices, MoOx/Al has lower impact than Ag, and fluorine‐tin‐oxide lower than indium‐tin‐oxide. Furthermore, we compare perovskites with commercial crystalline‐silicon and thin‐film PV, accounting for the most recent developments in crystalline‐Si wafer production and differences in life expectancies and efficiencies. It is shown that perovskite systems produced with RtR manufacturing could reach in only 12 years of life, the same EROI as that of single‐crystalline‐Si PV lasting 30 years. This work lays a foundation for sustainability investigations of perovskite large‐scale deployment.

California has set two ambitious targets aimed at achieving a high level of decarbonization in the coming decades, namely (i) to generate 60% and 100% of its electricity using renewable energy (RE) technologies, respectively, by 2030 and by 2045, and (ii) introducing at least 5 million zero emission vehicles (ZEVs) by 2030, as a first step towards all new vehicles being ZEVs by 2035. In addition, in California, photovoltaics (PVs) coupled with lithium-ion battery (LIB) storage and battery electric vehicles (BEVs) are, respectively, the most promising candidates for new RE installations and new ZEVs, respectively. However, concerns have been voiced about how meeting both targets at the same time could potentially negatively affect the electricity grid’s stability, and hence also its overall energy and carbon performance. This paper addresses those concerns by presenting a thorough life-cycle carbon emission and energy analysis based on an original grid balancing model that uses a combination of historical hourly dispatch and demand data and future projections of hourly demand for BEV charging. Five different scenarios are assessed, and the results unequivocally indicate that a future 80% RE grid mix in California is not only able to cope with the increased demand caused by BEVs, but it can do so with low carbon emissions (<110 g CO2-eq/kWh) and satisfactory net energy returns (EROIPE-eq = 12–16).

Seawater represents a potential resource to ensure sustainable availability of water for population and irrigation purposes, especially in some areas of the world. Desalination processes allow the production of fresh water, but they generate also brine as waste product. Sustainable brine management should be identified to ensure proper disposal and potentially resource recovery. This experimental study showed that emerging technologies such as Microbial Desalination Cells (MDCs) may provide a valuable contribution to the sustainability of the seawater desalination sector. In this paper, we report results on lab-scale desalination brine treatments applying MDCs, which allow energy savings, resource recovery, environmental impact minimization, and reduction of the organic load in municipal wastewater. Our results showed that MDCs’ treatment allows the removal of approximately 33 g of salts (62% of the total)—including chlorides, bromides, and sulphates—from 20 mL of brine within 96 h. The MDCs, according to the source of energy and the presence of mature biofilm at the anode, spent 7.2 J, 7.9 J, and 9.6 J in the desalination process, with the higher amount of energy required by the abiotic system and the lesser by the MDCs fed with just wastewater. Our approach also showed environmental and energy reductions because of potential metal recovery instead of returning them into marine environment. We quantified the avoided life cycle of human and marine eco-toxicity impacts as well as the reduction of cumulative energy demand of recovered metals. The main benefit in terms of avoided toxicity would arise from the mercury and copper recovery, while potential economic advantages would derive from the recovered cobalt that represents a strategic resource for many products such as battery storage systems.

AbstractThis paper provides a comprehensive assessment of the current life‐cycle sustainability status of crystalline‐based photovoltaic (PV) systems. Specifically, single‐crystalline Si (sc‐Si) and multicrystalline Si (mc‐Si) PV systems are analyzed in terms of their environmental and energy performance, providing breakdown contributions and comparisons with estimates published 6 years ago. Results clearly show the significant environmental improvement in the sc‐Si PV system production—mainly at the wafer stage—for which the impacts have been reduced by up to 50% in terms of carbon emissions and 42% in terms of acid gas emissions. The life‐cycle cumulative energy demand is estimated to be approximately 48% lower (for sc‐Si) and 24% lower (for mc‐Si) than previously reported estimates. Energy payback times of currently installed systems range from 1.3 (for c‐Si PV) and 1.5 years (mc‐Si PV) for fixed‐tilt ground‐mounted installations at low irradiation (1000 kWh/m2/year), to 0.6 years at high irradiation (2300 kWh/m2/year). The resulting energy returns on investment—expressed in terms of primary energy—range from 22 (at low irradiation) to 52 (at high irradiation) for sc‐Si PV systems and from 21 to 47 for mc‐Si PV systems. Furthermore, we examine the effects of cleaner electricity grids and grid efficiency improvements on these environmental and energy indicators.

For new technologies, such as perovskite solar cells (PSC), life cycle analysis (LCA) offers a fundamental framework for examining potential environmental, energy and health impacts and mitigation options before large-scale commercialization and for guiding improvements in development and production that further reduce their environmental footprint. However, credible LCA studies require actual process-based material, energy and emissions data, which may not exist before the technologies are commercially produced. Thus, the perovskite LCA literature is based on linear extrapolations of laboratory data. In this paper we critically reviewed the PSC LCA literature, explain the reasoning for a wide divergence of results, and determined which data apply to scalable industrial production, materials and processes. Our investigation probed into the formulation of each layer of a PSC device, and its potential for industrial scale fabrication. We found that electricity use is the main contributor to reported LCA results, explaining the large difference, ranging from 7.78 kWh to 1,460 kWh/m2, among various studies. Subsequently, we identified and discuss methodological errors in some of these estimates. In terms of life-cycle toxicity most of the reviewed LCA studies do not attribute any major overall toxicity impact to the presence of lead in the PSC devices. We also reviewed and critiqued studies describing "worst-case" scenarios of accidental release of lead into the environment, and, in spite of statements in those studies, we found them to be inconclusive. Finally, we discussed end-of-life (EoL) management options for resource recovery and for minimizing environmental impacts.