Solar Energy in the Home & Solar Heating

When one hears about solar energy the mind immediately thinks about solar panels and photovoltaic cells - the conversion of solar power into electricity. However, we must not overlook the fact that some of the Sun's energy falls upon Earth in the form of heat, and there have been several big steps taken to harness some of this energy. I will try to give a cross section of some of the ways in which we make use of Solar Heating.

Perhaps the most widely known of Solar Heating applications are those used domestically, and this is in several different forms. Passive solar heating makes use of the direct radiation effect on materials used in the structure of the house - walls, tiles etc. These gather heat during the day and dissipate it into the house during the evening. Special solar blinds that prevent heat from passing out of the house can be used to cover windows. Active solar heating relies upon the sun heating an intermediary fluid, usually in a solar panel. This fluid is then pumped through a heat exchanger from which a further pump directs heat into the house, usually by means of hot water radiators. Solar heating of domestic water is carried out in the same two ways.

The other common domestic use of solar heating is in swimming pool heating. Pool water is circulated through black plastic pipes made into panels and usually set onto the roof of the house. This is an effective way of increasing the length of the swimming season.

On a commercial level there are several systems in use. Trough collectors concentrate the Sun's heat by means of parabolic reflectors onto a pipe containing oil. This heated oil is pumped through a heat exchanger where water is turned into steam, which, in turn, drives a turbine to make electricity.

Power Towers concentrate the Sun's heat by means of a heliostat (a vast bank of mirrors all concentrating the Sun's heat into a small area) onto a tall tower where it is absorbed by molten salt. The salt is pumped through a heat exchanger where, as in the above example, water is turned into steam to drive a turbine. A solar oven operates in the same way both domestically and on a commercial scale. The domestic solar oven can reach about 200º Centigrade, whereas the solar furnace can attain temperatures of around 33,000º Centigrade.