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These top of the range solar
panel heat collectors are suitable for heating domestic
hot water even in the winter! also known as a vacuum hot water
panel.
One unit is adequate for an
average household (3-4 people), and it is modular, so you can
add more if required. A single panel is sufficient for a 200
litre cylinder, but you can fit 2 or more for high water usage,
or for heating swimming pools or underfloor heating.
Every house should have one,
with an overall efficiency of almost 80%, they are much more
efficient than electric photovoltaic solar panels (efficiency
of 7-15%).
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 ie pyrex) with
a 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, of the sun light's energy hitting the tube's
surface, 93% is absorbed, whereas only 7% is lost through
reflection and re-emission.
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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