Residential heat pump experiments — II

EARTH SEEMS to be superior to air or water as a source for heat pumps. Its ambient temperature is higher and less variable than outdoor air, and its use does not involve problems of accessibility or recirculation such as would accompany the use of surface or underground water. However, little factual information has been available on the heat transfer characteristics of the earth, particularly as a heat source. Also, some investigators were apprehensive that prolonged heat withdrawal or absorption would have adverse effects upon the long-term temperature levels in the earth.