Vacuum Tube Solar collector (Convert your Geyser to Solar)

Description

Vacuum tube solar collectors are made up of a single or multiple rows of parallel, transparent glass tubes supported on a frame. Each individual tube varies in diameter from between 1″ (25mm) to 3″ (75mm) and between 5′ (1500mm) to 8′ (2400mm) in length. Each tube consists of a thick glass outer tube and a thinner glass inner tube, (called a “twin-glass tube”) or a “thermos-flask tube” which is covered with a special coating that absorbs solar energy but inhibits heat loss. The tubes are made of borosilicate or soda lime glass, which is strong, resistant to high temperatures and has a high transmittance for solar irradiation.

Inside the each glass tube, a flat or curved aluminium or copper fin is attached to a metal heat pipe running through the inner tube. The fin is covered with a selective coating that transfers heat to the fluid that is circulating through the pipe. This sealed copper heat pipe transfers the solar heat via convection of its internal heat transfer fluid to a “hot bulb” that indirectly heats a copper manifold within the header tank.

These copper pipes are all connected to a common manifold which is then connected to your geyser, thus heating the hot water during the day. The hot water can then be used at night or the next day due to the insulating properties of the tank.

The insulation properties of the vacuum are so good that while the inner tube may be as high as 150°C, the outer tube is cooler to touch. This means that evacuated tube water heaters can perform well and can heat water to fairly high temperatures even in cold weather when flat plate collectors perform poorly due to heat loss.