Abstract: A method of operating a compressed air energy storage (CAES) system includes operating a compressor train of the CAES system, thereby compressing air. The method further includes, while operating the compressor train: inter-cooling a first portion of the compressed air; further compressing the inter-cooled first portion; after-cooling the further compressed first portion; supplying the after-cooled first portion to a storage vessel; supplying a second portion of the compressed air to a combustor; combusting the second portion; and operating a turbine train of the CAES system using the combusted second portion.