To meet a demand for a heat storage device storing cold in winter until summer and storing heat in summer until winter, and a demand for an air conditioner utilizing the cold for air-conditioning in summer and the heat for heating in winter.

The heat storage device comprising a heat storage material containing a latent heat storage material and soil, and a heat exchanger, is buried in the ground where temperature hardly changes all the year round. Material with a melting temperature higher than an underground temperature and with a solidifying temperature lower than the underground temperature is used as the latent heat storage material. In summer, the latent heat storage material is melted with hot outside air, and the outside air is cooled to about the underground temperature to air-condition the interior of the room. In autumn, the temperature of the latent heat storage material gradually falls toward the underground temperature but is higher than the solidifying temperature, thereby keeping the latent heat storage material in the melted state. In winter, the latent heat storage material is solidified with cold outside air while warming the outside air up to about the underground temperature, and the outside air is led into the room to assist heating. In spring, the temperature of the latent heat storage material gradually rises toward the underground temperature, but is lower than the melting temperature, thereby keeping the latent heat storage material in the solid state.

COPYRIGHT: (C)2007,JPO&INPIT