Investigation of the volume impact on cascaded latent heat storage system by coupling genetic algorithm and CFD simulation

•CLHS has advantages on heat storage performance compared to the non-cascaded system.•Volume distribution has a significant impact on the performance of CLHS system.•An optimization method of PCM volume distribution for CLHS has been developed.•The exergy is recommended as performance optimization indicator.•The charged energy, exergy and entransy increase by 13.79, 14.85 and 14.45%.