Abstract: The present disclosure is directed to an energy storage and retrieval system for the generation of power. A compressor (301) pressurizes ambient air. The pressurized air flow passes through a thermal energy regenerator (280) for thermal energy storage and retrieval and onto an expander (302) for generating mechanical power. The compressor (301) and the expander (302) are coupled to an electrical machine (304) through a common shaft (303). The regenerator (280) comprises one or more Thermal Energy Storage (TES) units which can be coupled to one another in a parallel configuration. The TES units comprise a thermal medium for the storage and retrieval of thermal energy.