Of all the fuels available to mankind, none are any cheaper, or less finite than the sun. The main problem in harnessing the sun's energy is the fact that it is so diffuse. However, with rising fuel costs and increased ecological awareness there are now various systems which will provide a building with heat and hot water by solar means.
One method of providing space heating is to build a thick concrete wall, painted matt black for maximum ability to absorb the sun's rays. Then a glass cover, usually double glazed, is spaced off the wall by a few centimetres. Two ventilation grilles are fitted into the wall, one at low level and one at high level. The sun's rays are then absorbed through the glass by the black wall, which then slowly warms up. Also the void between the wall and the glass heats up and is convected through the high level grille into the room which is to be heated. This draws cool air into the void through the low level grille. This air is then heated in the same way, rising as it heats up until it reaches the high level grille, when the whole process is repeated. In addition, as the concrete wall gets warmer, there is a delayed heat transfer as the heat passes through the wall and into the room.
Water is heated by constructing one or more collecting panels on the roof of the building. These consist of a glass cover, over a copper sheet which is painted matt black. Under this are copper tubes filled with water. This water is heated by the sun and passes into a coil inside a hot water cylinder, heating the water in the cylinder in the same way as a standard central heating system.
At present, solar heating is still very much in its infancy and, for the foreseeable future at least, will be far less widely used than any of the fossil fuels. However, research is continuing and when technology is such that it can be harnessed and stored efficiently and without high installation costs, it may well prove to be the fuel of the future.
