Comparative life cycle assessment of Rankine-based Carnot batteries and lithium-ion batteries for grid-scale energy storage

Abstract

Carnot batteries are investigated as a potential alternative to electro-chemical batteries for grid-scale electricity storage, which is a crucial element to the decarbonisation of energy systems via variable renewable energy sources. In this work, a comprehensive life cycle assessment of the construction and end-of-life phases of two Rankine-based Carnot battery system configurations is presented, comparing water and thermal oil as hot thermal energy storage fluid. Both are benchmarked against lithium-ion batteries as the most common electro-chemical battery alternative. To enhance the robustness of the analysis, uncertainties in the input parameters and life cycle inventory data are explicitly considered and analysed. The deterministic results show that the Carnot battery using water as hot storage fluid performs best in 13 of 18 environmental impact categories. For example, the climate change impact is up to 23% lower. Thermal energy storage systems are identified as the dominant contributors, accounting for more than 50% of the environmental impact across most impact categories. The stochastic results considering uncertainty show that the Carnot battery with water tends to have environmental impacts on par with lithium-ion batteries, while the Carnot battery with thermal oil tends to perform the worst.