Thermo mechanical energy storage for sector coupling: Literature overview, technology categorization and key performance indicators

Kurzfassung

The large-scale integration of renewable electricity is reshaping global energy systems, accelerating the transition away from fossil fuels while introducing challenges linked to variability and system balancing. Addressing these challenges requires advanced energy conversion and storage technologies that can balance supply and demand across multiple energy vectors. This paper reviews the role of thermo-mechanical energy storage (TMES) in enabling sector coupling (SC) - the coordinated integration of electricity, heating, and cooling - as a strategy to improve system flexibility and efficiency. In addition to TMES, partial configurations such as high-temperature heat pumps and organic Rankine cycles coupled with thermal energy storage (TES) are examined. Integrated systems are categorized based on their charging, storage, and discharging components, and their applicability across various temperature ranges and end-use sectors is discussed. The review finds that power-to-heat solutions, exceptionally resistive heating combined with TES, are the most mature, with several commercial-scale deployments already operating in industrial and district heating contexts. By contrast, power-to-heat-to-power and heat-to-power technologies remain at the prototype or demonstration stage, but offer strong potential for multi-energy provision and increased system flexibility. Research gaps are identified in underexplored areas, such as cold integration, simultaneous cogeneration, and applications requiring extremely high or extremely low temperatures. Beyond the technology overview, the paper introduces a novel Key Performance Indicator (KPI) framework to evaluate the effectiveness of TMES for SC. Unlike traditional round-trip efficiency, which overlooks non-electric outputs, the proposed KPI framework accounts for heating and cooling services, enabling fairer comparison with conventional benchmarks such as combined heat and power units, electrochemical batteries, or stand-alone heat pumps. Results show that while TMES underperform against Li-ion batteries in civil applications, they outperform fossil-based CHP plants in industrial contexts, highlighting their competitive advantage in large-scale, multi-vector energy hubs. By combining technology categorization with a new performance assessment tool, this work aims to support future research, demonstration, and deployment of integrated energy conversion and storage solutions in both civil and industrial sectors.