A coupled design methodology concerning complex off-design operation for compressed air energy storage systems

The volatility and intermittency of the renewable energy and the varied air pressure in air reservoir cause the CAES system to operate under complex off-design conditions. However, little attention is paid to the impact of complex variable operating conditions on system design in previous study, that is the reason why the actual system efficiency is relatively low in the whole process. In order to solve above issues, this paper proposes a new coupled design methodology (CDM) concerning complex off-design operation of CAES system. The compression process, expansion process, and the entire system is optimized with the CDM and the proposed probability-load (PL) factor. Through the CDM process, the average mass flow ratio of the compression process is decreasing while the actual mean back pressure increase under the specific power load curve, with the exergy efficiency increasing by 0.63 %. The average mass flow ratio of the expansion process is increasing, and the efficiency increases by 1.32 %. Meanwhile, in the compression process (or expansion process) design, no matter how the design parameters change, with the increase of input power (or output power) in a certain range, the efficiency increases firstly and then decreases. Eventually, the energy storage efficiency of entire system increases by 2.36 % with the proposed CDM.