Evacuated tube solar collectors
As opposed to common belief, the evacuated tube solar collector is not a new invention. The double-walled evacuated tube, or commonly known as the thermos, was invented by James Dewar, a Scottish physicist in 1893. This was used as the basic idea by L. R. Emmet, who built the first evacuated tube capable of utilizing the rays of the sun for energy. Even until today, this invention serves as the basis for many advanced researched and new inventions.
A double-walled glass tube is made up of two concentric pieces of tubing, which are melted into each other, and then the air is sucked out between them, creating the vacuum which will serve as a field of insulation. Previously to this, the outer surface of the inner tube is circularly coated with a selective coat – made up of all natural materials – which will act as the absorber. The aluminium nitrate coating is able to turn the rays of the sun into heat even in those realms which are invisible for the human eye. It’s absorbing power is really strong, which makes emission close to minimal.
The evacuated tube solar collector’s performance is the most spectacular in the winter months, when it can achieve two to three times better result than a regular flat solar collector.
Be careful however when choosing an evacuated tube solar collector, the appearance of these devices are often very similar but their inner qualities can greatly vary.
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