Evacuated tube collectors:
Above - Vacuum glass tubes efficiently transfer the heat energy from the sun onto black metal plates inside where water is passed through the system to pick up thermal heat energy.
Evacuated tube collectors also use the sun’s energy to heat water. The water flows through a pipe, which is located inside a glass tube. A vacuum separates the pipe carrying the water from the outer glass tube. A vacuum is an empty space that does not contain air. Air is a conductor of heat and the vacuum acts as a heat barrier (the vacuum prevents the heat from escaping to the surrounding air and being wasted.)
The water pipe (central core) has a treated dark, heat absorbent surface which is also designed to further minimise heat loss. Evacuated tube collectors can heat water to 150 degrees Celsius.
For more information about evacuated tube collectors, go to:
 http://www.solarserver.de/lexikon/vakuumroehrenkollektor-e.html
 Next Section >> Parabolic dishes.
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