HEAT PUMPS FOR HEATING

There will be some technical changes, of course: We don't need the refrigerator housing any more, but we may need a lot more evaporation coils to give us a bigger capacity, and the condenser coils inside the house should be distributed as heaters, not as a necessary nuisance hidden away behind the refrigerator; but the principle remains the same.

Such a heat pump has a number of significant advantages over, say, a furnace. For example, a single system can be so built that it heats in winter and cools in summer: By switching a few valves and reversing the direction of flow of the working fluid, the heat can be pumped out of the house instead of into it. A furnace, on the other hand, can never become an air conditioner. As an air conditioner, a heat pump (in the absorption version) can also be run directly by solar energy, since no more than heat is needed to evaporate the ammonia.

She economics of heat pumps has been obscured and obfuscated by the Commoner Lovins second law fetish. The decisive difference between a heat pump and a furnace is that what the former brings into the home is the heat contained in the air surrounding the house, whereas the latter brings in the chemical energy stored in oil or gas. If the former method had always been more advantageous and economic, the free market would not have overlooked it, for its aggressive entrepreneurs are, fortunately, greedy enough not to miss a chance when it offers itself. Now that rising fuel prices are beginning to make heat pumps competitive, they are not overlooking them.

The physics of heat pumps sometimes confuses people. Do they not contradict the second law of thermodynamics? No: That law says that work must be expended to cool a body below the temperature of its environment, and this is the ease here - the compressor uses up energy in order to cool the evaporation coils below the air temperature outdoors.

How come the outdoors never gets any cooler while the indoors warms up appreciably? Heat is proportional not only to temperature, but also to mass (a cold swimming pool contains more heat than a spoonful of boiling water). Outdoors, a lot of air drops bv alninst nothing in temperature; indoors a small amount of air gets a lot warmer. It is heat, not temperature, that is conserved by the law of the conservation of energy.

The energy used up by the compressor (or heater, in the case (of absorption systems) is smaller in practice) two to three times smaller than the heat supplied by the whole system, is that right a violation of the law of conservation of energy? No: The energy that is three times larger is not being created (or even converted) by the compressor; it is merely being transported by it. A railroad engine, too, uses up 100 times less energy than is contained in the coal it is hauling, but that is obviously not a violation of physical laws.