Electrified thermal energy storage

Electrified thermal energy storage (ETES) is a class of technologies that convert and store electricity as thermal energy for later use in heating and cooling applications. ETES can reduce the carbon emissions of heating by using low-emission renewable electricity when it is abundant. In this Review, we survey advances across ETES systems, examining how different conversion methods paired with various thermal storage media affect efficiency, scalability, cost and operational flexibility. Resistive heating coupled with sensible or latent heat storage has demonstrated market viability with costs of US$50 per kW, and can be used for both passive residential systems and active grid-balancing services. However, low energy density and non-negligible thermal losses over time limit these systems to short-duration applications, typically of days or weeks. By contrast, emerging ETES technologies that combine non-contact and/or volumetric heating technologies with latent or thermochemical heat storage could increase energy densities and storage times. These technologies could broaden ETES applications to high-temperature, long-duration uses. Possible integration routes and key research gaps are highlighted to guide the further advancement of ETES technologies for improved energy grid flexibility and resilience.