Techno-economic analysis of a modular thermochemical battery for electricity storage based on calcium-looping.

Electricity storage is becoming one of the main challenges for the massive deployment of renewables. Thermal energy storage is gaining momentum, with molten salts-based systems being the state-of-the-art technology. As an alternative, Thermochemical Energy Storage (TCES) is a promising system that can increase the system performance in terms of energy storage density, maximum heat discharge temperature and long-term storage capacity. This work proposes and preliminary evaluates the performance of a novel modular Thermochemical Energy Storage (TCES) system based on the Calcium-Looping (CaL) process. The modularity allows its integration with multiple renewable energy sources into different high-temperature applications, including hard-to-decarbonise applications. Heat for the charging stage is provided by electrical heaters connected either to a Photovoltaic (PV) facility or directly to the grid. Limestone particles are heated, and once they reach their decomposition temperature (∼ 930 °C at 1 bar), the released CO 2 is removed from the reactor, cooled, compressed, and stored. When the stored energy discharge is required, CO 2 is supplied to the reactor to produce calcium carbonate and release the stored heat (∼ 400–875 °C). In the proposed concept, the solids remain in the reactor, and CO 2 is added or removed depending on the stage. As cases of study of the concept, energy storage systems integrated with PV plants of 0.5 and 20 MW e and grid-based storage are considered. An hourly simulation throughout the year is performed. Results show an energy density above 1 GJ/m3, higher than current molten-salt-based systems. The levelized energy storage cost is below 100 €/MWh for the grid-based storage, highlighting its potential to contribute significantly to the global energy transition. • A novel modular thermochemical electricity storage system is proposed. • The levelized storage cost ranges from approximately 85–190 €/MWh. • All analysed cases exhibit a high energy storage density (∼ 1 GJ/m3). • The implementation of an energy arbitrage strategy proves to be cost-effective. [ABSTRACT FROM AUTHOR]