A heat exchanger system comprising: ---Relay fluid storage barrel: made of thermal conductive material to be integrated or combined, installed, in whole or in part placement into natural thermal energy body in vertical or downward oblique manner, wherein the relay fluid storage barrel includes at least one first fluid inlet and at least one first fluid outlet for fluid entering and leaving to perform fluid exchange function; wherein the first fluid inlet is installed in the relay fluid storage barrel at a position higher than that of the first fluid outlet, or vice versa, to prevent the fluid at lower part within the relay fluid storage barrel from stagnation; ---thermal energy exchanger installed inside the relay fluid storage barrel and having independent flow paths for fluid passing through, to perform heat exchange with the fluid in the relay fluid storage barrel the independent flow path having a second fluid inlet and a second fluid outlet, wherein the thermal energy exchanger is directly constituted by a thermal conductive structural body to enable thermal energy exchange between the relay fluid storage barrel and the thermal energy exchanger; ---Control device for controlling a pump, for pumping fluid in the system; and characterized by an ---External conduit made of a thermally conductive material, the external conduit being situated around the relay fluid storage barrel, wherein the external conduit is separated from the relay fluid storage barrel by a space that is filled with conductive materials in at least one of colloidal state, liquid state, and solid state, the external conduit having a diameter which is bigger than the external diameter of the relay fluid storage barrel and a length which is longer than that of the relay fluid storage barrel. ---Relay fluid storage barrel: made of thermal conductive material to be integrated or combined, installed, in whole or in part placement into natural thermal energy body in vertical or downward oblique manner, wherein the relay fluid storage barrel includes at least one first fluid inlet and at least one first fluid outlet for fluid entering and leaving to perform fluid exchange function; wherein the first fluid inlet is installed in the relay fluid storage barrel at a position higher than that of the first fluid outlet, or vice versa, to prevent the fluid at lower part within the relay fluid storage barrel from stagnation; ---thermal energy exchanger installed inside the relay fluid storage barrel and having independent flow paths for fluid passing through, to perform heat exchange with the fluid in the relay fluid storage barrel the independent flow path having a second fluid inlet and a second fluid outlet, wherein the thermal energy exchanger is directly constituted by a thermal conductive structural body to enable thermal energy exchange between the relay fluid storage barrel and the thermal energy exchanger; ---Control device for controlling a pump, for pumping fluid in the system; and characterized by an ---External conduit made of a thermally conductive material, the external conduit being situated around the relay fluid storage barrel, wherein the external conduit is separated from the relay fluid storage barrel by a space that is filled with conductive materials in at least one of colloidal state, liquid state, and solid state, the external conduit having a diameter which is bigger than the external diameter of the relay fluid storage barrel and a length which is longer than that of the relay fluid storage barrel.