Thermo-economic analysis for a novel grid-scale pumped thermal electricity storage system coupled with a coal-fired power plant

Combining pumped thermal electricity storage with existing thermal power plants can be a promising technical route for developing large-scale grid energy storage technologies for stably consuming renewable power. In this paper, a novel pumped thermal electricity storage system coupled with a supercritical coal-fired power plant is designed based on cascade heat storage. The thermodynamic analysis shows that the round-trip efficiency of the integrated system can reach 0.53-0.56 under 60-100% output load, for a practical design with a recuperation temperature of 280 degrees C and compressor outlet temperature of 500 degrees C. An economic analysis is performed and indicates this design can achieve a payback period of around 4 years considering a moderate charging electricity price of 3 ¢/kWh and a long storage period of 12 h. Further decreasing the recuperation temperature and increasing the compressor outlet temperature can reduce the system investment cost and LCOE, while it requires technological advancement of molten salts working at a wider temperature range and more robust compressors. In comparison to the integrated system with conventional two-tank storage, as well as other storage systems like vanadium redox flow batteries, the current design has a more attractive cost and can be scaled up in future multienergy applications.