Abstract: A heat transfer medium liquid circulation flow channel having a first heat exchange unit exchanging heat to a second heat exchange unit is provided, and a fixed amount of first heat transfer medium liquid circulates therein. A feed pipe couples heat source holding second heat transfer medium liquid having temperature difference from the first medium liquid to the heat transfer medium liquid circulation flow channel. The feed pipe is coupled to an inlet end side of the first heat exchange unit and a discharge pipe is coupled to an outlet end side thereof. A necessary amount of second medium liquid is supplied to the inlet end side via the feed pipe so that a detected temperature of the first medium liquid in the outlet end maintains required set temperature. The same amount of the first medium liquid as the supplied second medium liquid is discharged out of the discharge pipe.

Abstract: An underground heat exchanger has a bottomed tubular flexible bag body accommodated in an accommodation hole portion in the ground, and an outer tube accommodated in the accommodation hole portion, vertically extending along an outer surface portion of the bag body and communicating in its lower end with a lower end of the bag body. The outer surface portion of the hardening resin bag body can cover an inner wall portion of the accommodation hole portion in a closely contact state with the bag body being inflated. The bag body is hardened in the covering state, a lining tubular body formed by the hardening can form a liquid storage tank for storing a heat medium liquid in its internal space, and the outer tube is pinched between the outer surface portion of the bag body and the inner wall portion.

Abstract: An underground heat exchanger has a bottomed tubular flexible bag body accommodated in an accommodation hole portion in the ground, and an outer tube accommodated in the accommodation hole portion, vertically extending along an outer surface portion of the bag body and communicating in its lower end with a lower end of the bag body. The outer surface portion of the hardening resin bag body can cover an inner wall portion of the accommodation hole portion in a closely contact state with the bag body being inflated. The bag body is hardened in the covering state, a lining tubular body formed by the hardening can form a liquid storage tank for storing a heat medium liquid in its internal space, and the outer tube is pinched between the outer surface portion of the bag body and the inner wall portion.