Solar Heating
Author: Dr Kelvin Klemm
( Article Type: Explanation )
South Africa generally has clear skies and many hours of daylight throughout the year, making it an ideal country to exploit solar energy.
Solar heating can be used in a number of ways.
Solar Heating at Home
Solar water heaters can be placed on the roof of a house. If the house does not have electricity the solar water heater can be directly connected to hot water taps. Water temperatures will vary depending on the time of the day.
A solar heater can still be used if the house has electricity and can feed into the electrical geyser. A potential addition to the system is to place a storage tank in the roof connected to the solar heater so that hot or warm water can be drawn, even at night. This saves electricity in electrical heating of the water.
Other ways to use solar heating include:
- Building houses with windows or roof surfaces facing the sun so that the natural solar heat warms the house directly.
- Solar heating can also be used to heat for swimming pools.
- Solar cookers can boil water or fry and roast meat.
Imagination and ingenuity are still being used to develop other uses of the heat portion of the solar spectrum; it is a resource still waiting for optimum utilisation.
How Solar Heating Works
The sun emits a constant stream of energy towards the Earth. This energy reaches the ground at about one kilowatt per square metre at midday with unobstructed sunlight.
The natural sunlight consists of all wavelengths of the visible spectrum plus some ultraviolet (UV) at the short wavelength (blue) end of the spectrum, and some infrared (IR) at the long wavelength (red) end of the spectrum.
It is the red end of the spectrum with the infrared that carries heat, while the blue and ultraviolet is the high-energy portion. The blue and ultraviolet is the part of the spectrum that produces electricity from silicon solar cells, but it is the red and infrared part that produces heat.
