PURPOSE: To make a steep temperature front and attain a high COP by a method wherein there are provided a reactor capable of fixing cooling fluid and storing solid sorbent in contact with a heat exchanger; a heat source for heating thermal transfer fluid; and a source of cold heat for cooling heat transfer fluid.

CONSTITUTION: There is provided means for alternately circulating heat transfer fluid 10 through a heat exchanger 6 between a heat source 8 and a cold heat source 12, and creating a temperature front F ranging from the first segment C1 to the last segment C7 or in turn continuously crossing the segments within a solid absorbent 4. As this alternating circulation means, a first piston 14 arranged within the heat source 8 and a second piston 16 arranged at a cold heat source 12 are assembled. The piston 14 can feed heat transfer fluid of the heat source toward a heat exchanger 6 and further the piston 16 can feed the heat transfer fluid from the cold heat source 12 to the heat exchanger. A column having the solid absorbent 4 arranged therein constitutes a reactor 2 enclosing the heat exchanger 6.