Experimental and analytical investigation of near-isothermal pumped hydro-compressed air energy storage system

There is a global endeavor for decarbonization where the compressed air energy storage system has a critical role toward this goal. The efficiency of a conventional compressed air energy storage (CAES) technology is limited by low utilization of thermal energy and variable operating conditions. Therefore, a pumped hydro compressed air energy storage system (PH-CAES) is introduced in the present research and analyzed by using experimental and theoretical analysis. For the performance analysis of PH-CAES system, the main components and the whole system are precisely analyzed from thermodynamic points of view. The results show that the PH-CAES operates under a near-isothermal conditions, the polytrophic exponent n of air is 1.07 and 1.03 in power generation phase and energy storage phase, respectively, the experimental roundtrip efficiency and energy density of constant-pressure PH-CAES are 51% and 0.33 kWh/m(3), respectively. Moreover, achieving high system round-trip efficiency is dependent on components of system with high individual efficiencies. When the efficiency of hydro turbine generator units is 90%, the round-trip efficiency of PH-CAES can reach 63%.(C) 2022 Elsevier Ltd. All rights reserved.