A thermal power plant of the type in which excess energy produced by the plant during off-peak load periods is used to produce compressed air which is then accumulated in a storage tank. The compressed air is withdrawn from storage during peak load periods and delivered to a hot air turbine for generation of additional energy. A heat exchanger is incorporated in he compressed air line leading from the storage tank to the hot air turbine and steam is supplied to the heat exchanger for heating the compressed air prior to delivery to the hot air turbine. Heating steam can be produced by electrically heating water in a storage tank or it can be constituted by bleeder steam taken from an auxiliary steam turbine facility, or it can be taken from a steam storage tank.