Market-based optimization of the energy-to-power ratio of a latent thermal energy storage unit-based Carnot Battery

The volatile electricity generation from renewable energies creates the need for electricity storage technologies which, unlike the pumped hydroelectric energy storage established to date, are not tied to geographical conditions. The emerging technology of pumped thermal electricity storage (PTES) is one such alternative. PTESs belong to the group of Carnot Batteries. Using a price-taker approach with perfect daily foresight, this study determines the achievable contribution margin of a 5 MW generic storage in the German day-ahead market by exclusively exploiting daily price spreads. Based on real data from various phase change materials, the investment costs for PTES with a latent thermal energy storage (LTES) unit can be determined as a function of their energy-to-power ratio (E/P-ratio). By comparing the achievable contribution margins and investment costs, the most economical E/P-ratio can be identified. The result is a cost-optimal E/P-ratio that depends on the year, the round-trip efficiency (electricity to electricity), the coefficient of performance, and the power-related purchased equipment cost. For this purpose, both historical and future years were examined, whereby an agent-based market model was used to simulate the future electricity price time series. ... mehrOxalic acid dihydrate proved to be a promising phase change material for all round-trip efficiencies investigated. It turned out that, under the assumed boundary conditions, no PTES enables an economically attractive operation at round-trip efficiencies between 30 % and 70 %. The configurations closest to an economically attractive operation have E/P-ratios of at least 4 h related to the charging duration at half discharging duration.