Experimental demonstration of a dispatchable power-to-power high temperature latent heat storage system

The development of electricity storage solutions is crucial to support the integration of variable renewable electricity sources in electricity systems. This study experimentally characterizes a state-of-the-art full-scale electrical thermal energy storage (ETES) system in outdoor conditions. The system integrates a 600 kWh_th high-temperature latent heat storage module and a 13 kW_e Stirling engine. The heat storage module uses an 88Al–12Si metallic alloy as the phase change material to store electricity converted to thermal energy by a resistive heater in charging mode. The Stirling engine uses hydrogen as the working fluid for re-electrification (discharging). The system uses liquid sodium as the heat transfer fluid between the latent heat storage module and both the charging (electrical heater) and discharging (engine) sub-systems. Over the characterization period, the ETES prototype produced stable electricity at an average rate of 10.5 ± 1 kW for 13 consecutive hours daily with overall and power block first-law efficiencies of 23 % and 25 %, respectively. The effective storage utilization ratio varied between 0.58 and 0.94 depending on the discharge parameters. The response time was <5 s for output power regulation. The results highlight the potential of this latent heat thermal energy storage system to satisfy long-duration electricity storage applications and therefore contribute to the stabilization of electricity grids.