Техническое чтение для энергетиков. Бухарова Г.П. - 13 стр.

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about 8,000 million kilowatt hours of electrical energy at a cost of 0.04 d. (less than-y
cent) per kilowatt. In short, the peaceful uses of atomic energy are vast and tempting
– but we must stop squandering it on weapons of mass annihilation.
SOLAR ENERGY
We know that all the energy mankind has ever used comes from the sun, with
the exception of nuclear energy. If we took all the world's reserves of coal, oil, and
natural gas and burnt them up at the same rate at which we receive the sun's energy,
our whole supply would last less than three days. Yet we are only now beginning to
use that vast and almost inexhaustible source of energy in the sky directly.
The most primitive device for catching and trapping the heat of the sun is the
gardener's greenhouse. Its modern off-spring is the solar water-heater, usually a coil
of pipes placed in a shallow box on the roof of a house, embedded in black concrete
(black accepts the sun rays more easily, white reflects them) and covered with a glass
pane. The water circulating in the pipes is heated by the sun and then pumped into a
hot-water tank from which the household takes its supply. In Florida alone, more than
50,000 homes get their hot water in this way, and in Israel it has become general
practice to install solar water-heaters in new rural houses.
A more complicated but also more efficient device is the heat pump. It is, in
fact, a refrigerator in reverse. It picks up as much heat as it can get either from the
atmosphere, the soil, or from water (a river jar a lake); this amount of heat, which is
of course rather small in winter, is made to act on a liquid with a very low boiling-
point so that it changes into a gas. The gas is then compressed by means of a pump
and goes into a condenser coil, where it changes back to a liquid, thus setting its heat
free; this can be made to heat the house or to provide hot water. Many heat pumps
can be switched to reverse action so that they cool the air in summer.
Various types of 'solar houses' have been designed by engineers and architects,
especially in America, where many thousands of them have been built. In these
houses, some medium is used to store the heat of the sun and release it gradually as
required. Water is a good medium for the purpose, but Glauber's salt (hydrated
sodium sulphate) is even more efficient. It melts at a temperature of 90° F., taking in
a large amount of heat which it releases again when it turns back into crystals.
Twenty tons of the salt in the cellar of the solar house have been found to be
sufficient to keep the rooms comfortably warm in winter–with heat collected in the
summer!
Another interesting medium is gravel, incorporated in the walls of the house,
which it keeps warm on sunless days; by means of a small ventilator, hot air from a
heat collector on the roof is circulated through the gravel, which releases its
accumulated heat at an even rate.
These efforts at utilizing the heat of the sun show that the engineers are well
aware of the great possibilities of solar heating but also of its limitations. Many
countries, especially in what we call the moderate zones (to say nothing of the cold
regions), do not enjoy enough sunshine to make a solar house worth building, while

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