Long-duration thermo-mechanical energy storage: - Present and future techno-economic competitiveness

The extent to which long-duration energy storage (LDES) will support grid decarbonisation by enabling large penetration of renewable generation is subject to the achievement of suitable technical and economic performance. This study investigates the potential of established and novel thermo-mechanical energy storage (TMES) technologies to meet LDES targets, benchmarks TMES current and future techno-economic performance and highlights critical research developments. Results justify the priority of ensuring low storage costs over high roundtrip efficiency for LDES, thus endorsing novel concepts based on thermochemical energy storage. Besides adiabatic compressed air energy storage, novel TMES using metal oxidation/reduction and CaO hydration/dehydration reactions can potentially already meet the 20 USD/kWh cost target at 200 h duration, with current technology performance. The need for suggested and wide-ranging enhancements at material, device and system level is discussed, which may lead to TMES costs below 14 USD/kWh – competitive with long-duration solutions like hydrogen for covering the energy balancing needs of future low-carbon energy systems.