Thermodynamic and economic analysis of a novel gravity‐enhanced compressed air energy storage system

Abstract

AbstractIn this paper, a novel energy storage technology of a gravity‐enhanced compressed air energy storage system is proposed for the first time, aiming to support the rapid growth of solar and wind capacity. With air storage formed by the shaft well, gravity piston, and seal membrane, the proposed system could achieve constant operating pressure, high storage efficiency, and large storage capacity. Electricity charged into this system is simultaneously transformed and stored in the thermal, pressure potential, and gravitational potential forms. The operating properties of the proposed system are simulated and analyzed with the commercial software Thermoflex V29. Results show that both the storage pressure and the well radius have essential influences on the performance of the newly proposed system. The theoretical energy storage efficiency of the proposed system is in a scope of 63.58%–65.50% with a storage pressure range of 40–100 bar. Economic analysis based on the time‐of‐use price policy in China suggests that the optimum levelized cost of storage (LCOS) happens at the storage pressure of 70 bar and a well radius of 8 m. Besides, considering different plant cost factors that reflect the total investment of a power plant, the optimum LCOS is 1.09–1.26 CNY/kWh. Moreover, the specific exergy cost of the discharged electricity is assessed to be 0.51 CNY/kWh or so, which is significantly more profitable compared with the given electricity price of 1.15 CNY/kWh at off‐peak.