A compressor compresses air in such a manner that a motor is driven by renewable energy. An accumulator tank stores the air thus compressed. An expander is driven by the compressed air. A generator is mechanically connected to the expander. A first heat exchanger recovers compressed heat. A heat medium tank that stores a heat medium. A second heat exchanger that heats the compressed air. A first pump adjusts an amount of the heat medium to be supplied to the first heat exchanger. A control device controls the first pump to adjust the amount of heat medium to be supplied to the first heat exchanger so as to maintain the heat medium, which is stored in the heat medium tank, at a predetermined first temperature.