Performance of isobaric adiabatic compressed humid air energy storage system with shared equipment and road-return scheme

Abstract

• Novel isobaric adiabatic compressed humid-air energy storage system was investigated. • Water spray absorbs compression heat and controls compressed air outlet temperature. • Shared equipment and road-return scheme of energy storage/release system is employed. • Optimal system efficiency occurs at compression outlet parameters of 10 MPa/320 °C. • System efficiency reaches 72.6% and theoretic energy storage density is 17.2 kWh·m −3 . To cope with the inherent problem when intermittent renewable energies of solar and wind are connected to the grid, a novel isobaric adiabatic compressed humid air energy storage system was proposed and investigated. This system adopts a single stage dual-usage compressor-expander with synchronous rotating multi-cylinder to replace two separate multi-stage turbine type machines. The temperature of the compressed air is controlled by water spray before compression. The shared equipment with road-return stratagem of thermal oil energy storage/release system is employed. A hydro-assisted isobaric adiabatic compressed air storage system is formed with an underground cavern such as abandoned coal mine as the lower reservoir and a surface reservoir as the upper reservoir, and the nylon cloth pipe system is arranged in the underground cavern to store compressed air around water. By establishing the thermodynamic model of the system, the influences of the outlet pressure and temperature of compression on the system performance were analyzed determined respectively by the depth of the underground cavern and the working temperature of the thermal oil of the energy storage system. The results show that the round-trip efficiency varies slightly with the compression outlet pressure. Under the conditions of compression outlet parameters of 10 MPa/320 °C and the isentropic efficiencies in compression and expansion are 85%, the round-trip efficiency reaches 66.6% and the theoretical energy storage density is 16.5 kWh·m −3 .