We are developing a novel renewable energy system that can meet multiple heating and cooling demands of a building. This system consists of a water loop to which ground heat exchangers, a unique sky-source heat pump, and water-source heat pumps for various applications are connected. The outdoor panel of the sky-source heat pump is a refrigerant evaporator in the solar-source and air-source operation, and can be switched to a condenser in the nocturnal-radiator operation. These operational modes restore soil temperature either by adding heat to or subtracting heat from the ground on a daily basis, allowing the ground heat exchanger to be closely packed and compact. A prototype system showed high COP possibilities in space heating, air conditioning, and hot water supply. This paper explains the concept of the system and describes some test results of the experiment.