Thermodynamic performances analyses and process optimization of a novel AA-CAES system coupled with solar auxiliary heat and organic Rankine cycle

An AA–CAES–SAH–ORC system for cascade utilization of energy is proposed based on the AA–CAES–SAH system. The position of the solar auxiliary heat is rearranged, and the exhaust air of air turbine is used as heat source of the organic Rankine cycle. Energy and exergy efficiencies, conversion coefficient of electricity storage, and potential coefficient of waste heat are selected as evaluation indicators to analyze the influence of different operating parameters on the thermodynamic performances, which is then compared with those of the AA–CAES–SAH system. Maximum energy and exergy efficiencies are selected as the objective functions for process optimization to reveal the optimal operating parameters and the best thermodynamic performances of the system. The results show that the four evaluation indicators of the AA-CAES-SAH-ORC system are better than those of the AA-CAES-SAH​ system. The AA-CAES-SAH-ORC system has better thermodynamic performances when the total pressure ratio of compressor unit, the temperature of thermal conductive oil heated by solar energy, the mass flow rate of air in the energy release process, and the temperature of exhaust gas in the air turbine are lower When the compression ratio of the low and high pressure stage compressors are 9.402 and 7.871, the expansion ratio of the high and low pressure stage air turbines are 9.099 and 9.990, the maximum energy and exergy efficiencies of the AA-CAES-SAH-ORC system are 64.71% and 71.88%, respectively.