PURPOSE: To permit to accumulate the rotating energy of a windmill efficiently and utilize it easily by providing a heat accumulating and releasing device consisting of a heat accumulating and emitting tank, accommodating metallic hydride, and a hydrogen reserving tank, which are communicated with each other.

CONSTITUTION: The metallic hydride in the heat accumulating and emitting tank 31 generates hydrogen when heated and the hydrogen is reserved into the hydrogen reserving tank 32 through a pipe 34a. When heat energy is necessary, the hydrogen in the hydrogen reserving tank 32 is sent into the heat accumulating and emitting tank 31 through the pipe 34b. According to this method, heat is generated by the reaction of hydrogen and metallic hydride and the heat is utilized by a heat energy utilizing device 40. Thus, the heat energy, converted from the energy of wind, may be accumulated for a long period of time without any heat loss and, further, the energy may be utilized easily in accordance with the necessity therefor.