Solar Collector
Solar collectors absorb heat from the sun's rays. They can be used to effectively heat and cool buildings. The most common type of collector for space heating is a flat plate designed to absorb both radiation falling directly on it, as well as radiation scattered by the atmosphere.
Collectors are usually panels of aluminium, copper, or steel. The panels are usually painted black. The black colouring inhibits reflection and encourages absorption. Insulation is placed behind the collector to prevent heat loss.
The collector is covered with glass or plastic. This layer allows short-wave radiation – or light – to enter the collector. As the radiation passes through the glass or plastic, it is transformed from short-wave radiation to long-wave radiation – or heat. Long-wave radiation cannot pass through the glass or plastic back into the atmosphere. Therefore, the heat is trapped within the collector. Collectors are usually placed at an angle to maximise the amount of radiation falling on them.
A transfer agent (air or water) is circulated through the collector and becomes heated. As it leaves the collector and travels through the heating ducts of a house, it warms the air inside the house or brings hot water to sinks, tubs, and appliances. With solar collectors, storage is a problem: great amounts of heat must be stored for nighttime use and for use during cloudy days.