基于CO2卡诺电池技术的长时储能系统优化设计

Abstract CO 2 -based Carnot battery systems are a promising solution for large scale, long duration energy storage, as they combine high round-trip efficiency with the absence of geological constraints, also enabling the storage of both hot and cold thermal energy. In this work, the optimal design criteria for a CO 2 -based Carnot battery are discussed, focusing on configurations where heat exchangers are shared between the charging and discharging phase (i.e. hot storage, cold storage and recuperator) and employing a hot storage based on a sensible solid medium. The system design and performances are modelled in MATLAB, investigating the round-trip efficiency, the energy density and the system footprint across a wide range of operative conditions and adopting realistic assumptions for the plant components performance. The optimized results, obtained from hundreds of simulated cases, demonstrate that with moderately low cycle maximum pressures (around 150 bar) and low cycle maximum temperatures (below 130 °C), the battery can already achieve a round trip efficiency over 55 %, reaching maximum values greater than 60 % for low cold storage temperatures (−30 °C). Differently, the energy density largely benefits from increasing the maximum pressure up to 250 bar, thanks to larger temperature variation in the hot thermal storage. Under these conditions, the system footprint is lower than 20 m 2 /MWh el , with energy densities as high as 11 kWh el /m 3 for a cold storage temperature of 0 °C.