The Heat Pump
The heat pump, we are told, is a magical gadget that can be used to heat a house in winter and cool it in summer, depending upon the direction the pump is run. By use of a heat pump, University of Alaska scientist Hans Nielsen is seeking to prove that it is possible to pump enough heat out of the ground to heat a house all winter, even in Alaska.
Each summer, according to Professor Nielsen of the Geophysical Institute, enough heat is absorbed by a quarter-acre of soil to heat a moderate-sized house all winter. The problem is to transfer the energy stored in the ground into the house. Since the temperature of northern soils is normally within a few degrees of the freezing point and the desired temperature of the house is near 68°F (20°C), this transfer sounds impossible. However, it is quite possible if one employs a heat pump, the principle of which has been known for 150 years.
To demonstrate how the heat pump works we need only think about how refrigerator works, since a refrigerator is a heat pump. When it operates, the food inside the refrigerator gets colder and the room in which the refrigerator sits gets warmer.
In the refrigerator heat pump an electrically driven pump compresses freon vapor to high pressure and to a temperature higher than room temperature. The freon passes to condensor coils exposed to the room where heat is given off to the air outside and a part of the freon condenses to the liquid state (the coils are usually on the back of the refrigerator). The now somewhat-cooler freon gas and liquid mixture passes through a restrictive valve into passageways inside the refrigerator. Extreme cooling accompanies the expansion and evaporation occurring as the freon leaves the valve, so the temperature drops to perhaps -40°F. Since the freon is so cold, it can extract heat energy from the food in the refrigerator. The house is made warmer by an amount determined by how much heat is taken from the food plus the electrical or other energy used to drive the compressor pump.
The heat pump proposed by Professor Nielsen operates exactly the same way. In thinking it through, we only need mentally to replace the food in the refrigerator with the ground outside the house. Furthermore, when the house gets too hot in summer, the heat pump can be reversed to put energy back into the soil to supplement that heat it will receive from the sun.
