Evacuated tube collectors are the next generation in solar-thermal technology. These systems are easily sized to fit the user’s needs and can yield much higher temperatures, even on cloudy days.
Heat pipe evacuated tube collectors use a copper heat pipe attached to an absorber plate, inside a vacuum sealed solar tube. The heat pipe is hollow and the space inside is also evacuated. Inside the heat pipe is a small quantity of liquid, such as alcohol or purified water plus special additives. The vacuum enables the liquid to boil at lower temperatures than it would at normal atmospheric pressure.
When sunlight falls on the surface of the absorber, the liquid in the heat tube quickly turns to hot vapour and rises to the top of the pipe. Water or glycol, flows through a manifold and picks up the heat. The fluid in the heat pipe condenses and flows back down the tube. This process continues, as long as the sun shines.
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