• Energy Research

Renewable electricity generation is intermittent and its large‐scale deployment requires some degree of energy storage. Although best assessed at grid level, the incremental energy and environmental impacts of adding the required energy storage capacity may also be calculated specifically for each individual technology. This article deals with the latter issue for the case of photovoltaics (PV) complemented by lithium‐ion battery (LIB) storage. A life cycle assessment (LCA) of a 100 MW ground‐mounted PV system with 60 MW of lithium‐manganese oxide (LMO) LIB, under a range of irradiation and storage scenarios, shows that energy payback time and life cycle global warming potential increase by 7–30% (depending on storage duration scenarios), with respect to those of PV without storage. Thus, the benefits of PV when displacing conventional thermal electricity (in terms of carbon emissions and energy renewability) are only marginally affected by the addition of energy storage.

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.

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.

AbstractThis paper provides a comprehensive assessment of the up‐to‐date life‐cycle sustainability status of cadmium‐telluride based photovoltaic (PV) systems. Current production modules (Series 6 and Series 7) are analyzed in terms of their energy performance and environmental footprint and compared with the older series 4 module production and current single‐crystalline Silicon (sc‐Si) module production. For fixed‐tilt systems with Series 6 modules operating under average US irradiation of 1800 kWh/m2/year, the global warming potential (GWP) is reduced from 16 g CO2eq/kWh in Series 4 systems to 10 CO2eq/kWh in Series 6 systems. For operation in US‐SW irradiation of 2300 kWh/m2/year, the GWP is reduced from 11 to 8 CO2eq/kWh and for 1‐axis tracking systems operating in Phoenix, Arizona, with point‐of array irradiation of 3051 kWh/m2/year the GWP is reduced to 6.5 CO2eq/kWh. Similar reductions have happened in all environmental indicators. Energy payback times (EPBT) of currently installed systems range from 0.6 years for fixed‐tilt ground‐mounted installations at average US irradiation at latitude tilt installations to 0.3 years for one‐axis trackers at high US‐SW irradiation, considering average fossil‐fuel dominated electricity grids with fuel to electricity conversion efficiency of 0.3. The resulting energy return on energy investment (EROI) also depends on the conversion efficiency of the electricity grid and on the operation life expectance. For a 30‐year operational life and grid conversion efficiency of 0.3, EROI ranges from 50 (at US average irradiation) to 70 for US‐SW irradiation. The EROI declines with increased grid conversion efficiency; for CdTe PV operating in south California with grid conversion efficiency of 49%, the EROI is about 50 and is projected to fall to 30 when the state's 2030 target of 80% renewable energy penetration materializes. Material alternatives that show a potential of further reductions in degradation rates and materials for enhanced encapsulation that would enable longer operation lives have also been investigated. A degradation rate of 0.3%/year, which has been verified by accelerated testing, is assumed in 30‐year scenarios; this is projected to be reduced to 0.2%/year in the near‐term and potentially to 0.1%/year in the longer term. With such low degradation rates and enhanced edge‐sealing, modules can last 40‐ to 50‐years. Consequently, all impact indicators will be proportionally reduced while EROI will increase. This detailed LCA was conducted according to ISO standards and IEA PVPS Task 12 guidelines. The study revealed that the choices of system models, methods and temporal system boundaries can significantly impact the results and points out to the need to include assumptions regarding these choices in the “transparency in reporting” requirements listed in the IEA PVPS Task 12 Guidelines.