Life cycle environmental hotspots analysis of typical electrochemical, mechanical and electrical energy storage technologies for different application scenarios: Case study in China

With increasing capacity of energy storage implemented into the power system services, a growing interest in evaluating the environmental impacts of energy storage systems (ESSs) has been sparked. In the present work, a comprehensive life cycle environmental hotspots assessment model for alternative ESSs was developed, including lithium iron phosphate battery (LIPB), vanadium redox flow battery, compressed air energy storage (CAES), supercapacitor and flywheel energy storage. A detailed life cycle inventory for the considered typical ESSs in China was provided to ensure the validity of the comparative assessment. It was indicated that the environmental impacts of ESSs were significantly dependent on technical solutions and grid application scenarios, including energy time-shift, frequency regulation, photovoltaic self-consumption, and renewable energy support. The results ranged from 26 to 702 kg CO2 eq/MWh for global warming potential (GWP), 0.1 to 1.2 kg PM2.5 eq/MWh for fine particulate matter formation, 0.1 to 3.0 kg SO2 eq/MWh for terrestrial acidification, 11 to 146 kg oil eq/MWh for fossil resource scarcity, and 0.0005 to 0.0122 kg N eq/MWh for marine eutrophication. LIPB emerged as a promising solution, while the environmental competitiveness of CAES increased in renewable-based power systems. It is advisable to prioritize the deployment of ESSs with minimal environmental footprints in the manufacturing process, such as CAES, despite the constraints imposed by relatively limited round-trip efficiencies. Moreover, the influences of the round-trip efficiency, depth of discharge, cycle frequency, and electrical grid emissions factor on the results were discussed. Particularly, the GWP of ESSs under the energy time-shift and frequency regulation scenarios decreased by approximately 3%-7% with a 1%-pts increase in the round-trip efficiency. Overall, the results could help manufacturers make informed decisions on energy storage materials selection. Besides, decision makers are recommended to consider multiple environmental impact indicators in devising future energy storage strategies.