C2 South City Business Centre, Tallaght, Dublin 24.
Phone: (353) 01 4031200
Fax: (353) 01 4137777
|
|
| Solarlink Evacuated Tubes |
 |
|
Evacuated Tubes and how they function
|
Solar tubes absorb solar energy converting it into heat for use in water heating. Solar tubes are also referred to as evacuated tubes, as the space between the two glass layers is evacuated to form a vacuum. Solar tubes have already been used for years in Germany, Canada, China and the UK. There are several types of solar tubes in use in the solar industry. Systemlink uses the most common "twin-glass tube". This type of tube is chosen for its reliability and performance.
Each solar tube consists of two glass tubes made from extremely strong borosilicate glass. The outer tube is transparent allowing light rays to pass through with minimal reflection. The inner tube is coated with a special selective coating, which features excellent solar radiation absorption and minimal reflection properties. The tops of the two tubes are fused together and the air contained in the space between the two layers of glass is pumped out while exposing the tube to high temperatures. This "evacuation" forms a vacuum, which is an important factor in the performance of the solar tubes.
|
To get further advice about
this topic or talk to an expert please click here
|
Why a vacuum? As you would know if you have used a glass-lined thermos flask, a vacuum is an excellent insulator. This is important because once the solar tube absorbs the radiation from the sun and converts it to heat we don't won't to lose it! The vacuum helps to achieve this. The insulation properties are so good that while the inside of the tube may be 150oC, the outer tube is cold to touch. This means that solar tube water heaters can perform well even in cold weather when flat plate collectors perform poorly due to heat loss.
In order to maintain the vacuum between the two glass layers, a barium getter is used (the same as in television tubes). During manufacture of the solar tube this getter is exposed to high temperatures, which causes the bottom of the evacuated tube to be coated with a pure layer of barium. This barium layer actively absorbs any CO, CO2, N2, O2, H2O and H2 out-gassed from the solar tube during storage and operation, thus helping to maintaining the vacuum. The barium layer also provides a clear visual indicator of the vacuum status. The silver coloured barium layer will turn white if the vacuum is ever lost. This makes it easy to determine whether or not a tube is in good condition.
|
To get further advice about
this topic or talk to an expert please click here
|
Inside a SolarLink Evacuated Tube
|
Left-to-Right Assembly Diagram of SolarLink Tubes
|
|
|
|
