The future role of thermal energy storage in 100% renewable electricity systems

Abstract

Modeling tools and technologies that will allow reaching decarbonization goals in the most cost-effective way are imperative for the transition to a climate-friendly energy system. This includes models which are able to optimize the design of energy systems with a large number of spatially distributed energy generation sources coupled with adequate short, medium, and long duration storage technologies. Solar photovoltaic and wind energy are likely to become the backbone in a future greenhouse gas neutral energy system and will require low-cost, geographically independent storage technologies in order to balance their intermittent availability. As an alternative to lithium-ion batteries and hydrogen systems, thermal energy storage coupled with a power block (e.g., Carnot batteries, pumped thermal storage, etc.) could be a promising option. Therefore, the current study aims to investigate the influence of renewable generation profiles coupled with alternate storage options (i.e., Li-ion and hydrogen cavern) on the installed capacity of electric-to-thermal-to-electric systems using a 100% renewable electricity system in Germany as a case study. The analyses reveal that Carnot batteries complement established and near-future storage technologies, as they could fill the gap between daily storage such as batteries and seasonal storage such as hydrogen salt caverns. Furthermore, Carnot Batteries could offer multiple options for heat integration further increasing their potential.