The article on geothermal heat pumps ("How using geothermal heat is an all-round winner," Jan. 1, p12) totally misses the point. It is not necessary to dig up an acre of land to heat a house with a heat pump. Heat can be extracted from the air.
Heat pumps that use air as their low-temperature source have been around for years. Their efficiency is lower if the outside temperature is below freezing, but in warmer weather, their efficiency is comparable to geothermal heat pumps. Initial cost is slightly higher than that of normal refrigerated air conditioners.
Air conditioners are heat pumps that can only pump heat out. Heat pumps can heat or cool a building. The main reason that a heat pump costs more than an air conditioner is that the outside coil must have a defrost cycle. Also, the compressor runs approximately twice as frequently as an air conditioner's compressor and compressor life is therefore half as long.
Until recently, heat pumps were more expensive than burning natural gas. If power for heat pumps comes from natural gas, then the cost savings are minimal. However, if power comes from coal or nuclear power plants, then heat pumps can be cheaper.
Homes that use electric resistance heating can usually save money by switching to an air-cycle heat pump, even if there is no cooling requirement.
An exception to this is in some parts of Europe, where electricity is much cheaper at night than during the day. In these countries, electricity is used at night to heat bricks. Air is then blown across the bricks during the day, when electricity is expensive.
Are your eyes glazed over yet? None of this is simple. Anyone who tries to make energy policy seem simple by holding up an energy-saving lamp is lying. Correct policy requires understanding how all the alternatives work and what people do under different circumstances.
William Ernest Schenewerk