PURPOSE: To improve room-heating capacity by operating room cooling and room heating by use of solar heat and combustion heat and by recovering the heat discharged from a Rankine-cycle engine.

CONSTITUTION: The solar heat collected by solar-heat collector 1 and the combustion heat discharged from burner 3 are sent to heat storage tank 4 and stored for use duting the night. By this stored heat, Rankine-cycle engine 10 is driven and refregerator 17 is operated. By, this, the heat pump refergeration cycle works and heat is discharged from heat exhcanger 19 on the room interior side, and thereby room heating can be operated in winter and room cooling in summer. Further, at the time of room heating, by operating change-over switch valve 15, the heat discharged from Rankine-cycle engine 10 can be added to heat exchanger 14 of heat pump cycle on the room exterior side