PURPOSE: To prevent the outside equipment from being damaged by the heat of compressed air and effectively utilize energy by introducing the compressed air discharged from a compressor into a strage tank through an heat accumulator when the outside equipment is at the temperature where the equipment may be damaged by the heat of the compressed air.

CONSTITUTION: When the temperature detected by a temperature detector 28 is over a prescribed value, the compressed air discharged from a compressor 8 is introduced into a heat accumulator 12 through a piping 25, and the heat of the compressed air having a high temperature is transmitted to a heat storage material in the heat accumulator 12. During this time, the compressed air in a storage tank 9 is supplied into the outside equipment through a piping 23, three-way solenoid valve 22, piping 18, heat transmission pipe 15, and a piping 17, in accordance with the use of the compressed air in the outside equipment. Therefore, the outside equipment is prevented from being damaged by the heat of the compressed air, and energy can be utilized effectively.