Thermo-conversion of a physical energy storage system with high-energy density: Combination of thermal energy storage and gas-steam combined cycle

Electrical energy storage (EES) systems are of great significance for the widespread use of renewable energy and peak shaving of power grids. The EES system with high-energy density is one of the current research hotspots. In this paper, a novel type of EES system with high-energy density, pressurized water thermal energy storage system based on the gas-steam combined cycle (PWTES-GTCC), is presented. The proposed system could achieve the coupling of thermal energy storage (TES) and gas-steam combined cycle (GTCC) through the cracking reaction of methanol. In discharging process, methanol is cracked after absorbing thermal energy, and the cracked gas is burned to drive GTCC for generating electricity. By constructing the thermo-dynamic model of the system, performance of the system and each component are discussed in detail. The results show that the energy storage density of the proposed system reaches 36.5 kWh/m³, and it is the most sensitive to the temperature of the high-pressure water with a sensitivity coefficient of 5.7. Furthermore, the efficiency of the PWTES-GTCC is expected to reach 53.1% as the efficiency of the GTCC and the electrical efficiency of the pressurized water thermal energy storage (PWTES) achieve 55.4% and 42.6%, respectively. These three efficiencies are most sensitive to the inlet temperature of the gas turbine.