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| Solar panel BP | Evacuated tube collector |
Solar Collectors
There are a variety of ways to collect solar thermal energy which can be used for heating water, space heating, daylighting, cooking and focussed through collectors to provide high temperature heat to operate turbines to generate electricity.
In passive solar heating the solar radiation will pass through glass panels to heat the space behind them. This could be a conservatory, a greenhouse, a swimming pool etc.
Although the amount of heat is dependant on the Sun, there is a benefit from direct gain within the house through the heating of internal areas within the house.
Active solar heating collects solar radiation from a collector, typically mounted on a roof.
Flat plate water collectors are standard throughout the world. They have an absorber plate designed to collect the heat from the Sun. The plate can be made of a variety of materials with high absorptivity and a high thermal conductivity. It is also common for the plate to have a black surface to prevent solar radiation from reflecting off the plate. The absorbed solar radiation heats water being pumped through the device.
Collectors without a glass cover can raise water to 10oC whilst those with a glazed cover can raise water to 50oC.
Evacuated tube collectors are comprised of glass tubes which have a vacuum inside them and a metal strip which acts as the absorber. An array of tubes are plugged into a pipe containing water. The water can be raised to temperatures of 150oC.
Parabolic trough collectors consist of a curved length of reflective surface which focuses the solar radiation onto a glass tube containing water which runs down the centre of the collector. The water can be raised to temperatures of 150oC.
Point focus collectors consist of a parabolic collector with a mirrored dish which focuses the solar radiation onto a glass tube in the center of the dish which contains a flow of water. The water can be raised to temperatures in excess of 100oC. One additional feature of a point focus collector is that it can track the movement of the Sun for maximum heat collection.
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