Abstract: A two stage expansion and single stage combustor compressed air energy storage cycle that employs a heat exchanger to raise the temperature of the compressed air before it enters a high pressure expander. A combustor heats the exhaust from the high pressure expander and creates a working gas to drive a low pressure expander. The exhaust from the low pressure expander is supplied to the heat exchanger to raise the temperature of the compressed incoming air. A portion of the exhaust of the high pressure expander is cooled and employed in a cooling circuit within the low pressure expander. A starter valve in the compressed air input circuit finely tunes the incoming air during startup. The startup air flow is heated by an auxiliary duct burner until the low pressure turbine exhaust reaches operating temperature and is sufficient to heat the incoming air under normal operating conditions.