Patent ID: 7412838

Claim:
A heat pump employing CO 2 as a refrigerant comprising: a CO 2 circulation path, a compressor for compressing the refrigerant, a gas cooler for cooling the compressed refrigerant to produce hot water, expansion means for allowing the refrigerant to be depressurized and expanded, a heat exchanger for allowing the refrigerant to exchange heat with natural water, an evaporator for allowing the expanded and depressurized refrigerant to be evaporated by receiving heat from cold water, and a first stopper valve and a second stopper valve, wherein the expansion means comprises a first expansion valve and a second expansion valve, wherein the first stopper valve and the first expansion valve are provided in parallel with each other downstream from the compressor in the CO 2 circulation path, wherein the heat exchanger is provided downstream from the first stopper valve and the first expansion-valve, wherein the second stopper valve and the second expansion valve are provided in parallel with each other downstream from the heat exchanger, wherein the evaporator is provided downstream from the second stopper valve and the second expansion valve, and wherein opening and closing of the first stopper valve and the second stopper valve allow switching between a heating/hot-water supplying mode, where heated water is supplied from water heated in the heat exchanger by heat exchange with the refrigerant and a cooling/cool-water supplying mode, where cooled water is supplied from water cooled in the heat exchanger by heat exchange with the refrigerant.