Multi-objective Optimization on Thermodynamics and Economics of a Constant-pressure Pumped Hydro Combined With Compressed Air Energy Storage System

Considering the shortages of existing bulk energy storage technologies, to overcome the drawbacks of renewable energies (i. e., intermittent and fluctuation), a constant-pressure pumped hydro combined with compressed air energy storage (PHCA) system is proposed based on pumped hydro energy storage (PHES) and compressed air energy storage (CAES) technologies. Firstly, the thermodynamic model and economic model of the system were built. Then, by selecting energy efficiency and total investment cost per total output energy (ICPE) as objective functions and setting the hydrosphere ratio, the preset pressure, the pressure ratio of compressor and the efficiency of compressor as decision variables, multi-objective optimizations for systems of 1 MW, 2 MW and 5 MW were carried out, respectively. The results revealed that the system can reach a relatively high system efficiency and a relatively low ICPE when the compressor efficiency is relatively high and values of the hydrosphere ratio, the preset pressure and the pressure ratio of compressor are around 7, 4 MPa and 2, respectively. Furthermore, with the increasing of the capacity of the system, ICPE decreases rapidly. The results could provide theoretical basis for the further engineering application of this system. © 2020, Science Press. All right reserved.