Development of a heat storage heater for hybrid electrothermal conversion and latent heat storage

Grid-scale long-duration energy storage (LDES) is essential for decarbonizing energy systems, including power and industrial heat systems. As an economically viable LDES technology, the development of an electrical thermal energy storage (ETES) system—comprising electrothermal conversion, thermal energy storage, and optional heat engines—is progressing. A key challenge in realizing ETES is the electrothermal conversion process at the several-hundred-MW scale. This study proposes a novel heat storage heater (HSH) that combines electrothermal conversion and thermal storage functions using phase change materials (PCMs). The HSH that achieves high-temperature TES using an alloy-based PCM is a novel material that has not been reported previously. The HSH design allows for GWh-scale heat storage at high density as a several-hundred-MW class electrothermal converter, using a microencapsulated PCM (MEPCM) with a ZnO coating and a Zn–30 mass% Al (Zn–30Al) core. The system exhibited electrical resistivities of at least 9.8 Ω cm due to a conductive network formed by ZnO in the MEPCM. Upon energization, the temperature exceeded the alloy's storage temperature, and a temperature plateau was observed at 470 °C due to the alloy's melting temperature (438–512 °C). This study paves the way for designing innovative electrothermal conversion systems, such as ETES systems.