Solar Evacuated Tubes
Evacuated tube solar hot water panels
These are the top-of-the-range solar panel heat collectors which are suitable for heating domestic hot water, swimming pools etc - even in the winter! One unit is adequate for an average household (3-4people), and it is modular, so you can add more if required.
A single panel is sufficient for a 200litre cylinder, but you can fit 2 or more for higher water usage, or for heating swimming pools or underfloor heating. This high tech unit concentrates the sun's energy at the tip of the copper 'heat tube' - like a solid state magnifying glass!
The vacuum tube solar panel has been around for over 10 years, and has proved to be reliable and dependable. The vacuum tubes consist of a double wall glass tube (made from strong borosilicate glass i.e. Pyrex) with a space in space in the centre which contains the heat pipe. The sun's radiation is absorbed by the selective coating on the inner glass surface, but prevented from re-radiating by the silvered innermost lining. This is in effect like a one-way mirror which has been optimised for infra-red radiation. In fact it is very efficient, 93% of the sunlight's energy hitting the tube's surface is absorbed, whereas only 7% is lost through reflection and re-emission. Because the presence of the vacuum wall prevents any losses by conduction or convection, just like a thermos flask, the system will work even in very low temperatures, unlike traditional flat plate collectors.
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