To continuously extract refrigerant state changes due to temperature differences as power.

A pressure of a refrigerant expanded by heat applied to a heater from the outside is extracted as power by an expander, while the expanded refrigerant is cooled and liquefied. Then, the refrigerant is conveyed to the heater using a conveyor rotated by power generated by the expander to extract power continuously. The conveyor is a device that conveys a fixed amount of refrigerants between devices by rotating a rotor. The pressure and pressure difference of refrigerants on the high pressure side and low pressure side can be kept constant by controlling the rotational speed of the rotor. The mechanism is used as a heat pump, and the refrigerant on a condenser side is conveyed to the low pressure evaporator side and expanded inside the evaporator to be used as a back pressure of a compressor, thereby improving operation efficiency.