The production of tube collectors requires many singlesteps, which increases the price. The so-called "Sydney vacuum tube collector" is produced from two interlocked fused glass tubes according to the "thermos" principle. The absorber is insert in each tube and connected at the top of the collector. We must strictly distinguish the so-called "heat pipe" tubes, which have only a simple glass tube with an absorber. The vacuum of "Sydney vacuum tube collector" with CPC mirrors have this best thermal insulation values and high solar yields even in diffused light and low light intensity during the cold season. Small pipe diameters, little solar fluid, low power consumption of the circulation pump. In case of damage they can individually replaced easily in the field without the need to empty the hole system. Almost all of the tubes are made in China. In the production of high quality collectors the CPC mirrors, absorbers will be finally assembled in Germany. The Domain of the vacuum tube collector systems is the heating - assisted solar system with very high annual utilization rates and yields.
The vacuum tube collector is used to heat water or water-antifreeze mixtures. Evacuated tube collectors are flat plate collectors because they (coated dark) possess a flat absorber surface. This is usually embedded in a center or the insides of two glass tubes. The collected thermal energy is usually transported via a heat pipe to the upper end of the tube whre a metal heat exchanger heats the heat transfer medium. With a positive temperature difference inbetween the medium and the heat storage the pump is turned on. The insulating effect is achieved with vacuum in one tube or in the intermediate space of two concentrically arranged glass tubes, which prevents the heat transport by convection. Especially in winter vacuum collectors bring due to their very good insulation a significant greater power than flat plate collectors. Vacuum tube collectors reach comared with air-filled flat plate collectors in the same size substantially higher operating temperatures and are therefore suitable for producing industrial process heat. The absorber temperature, depending on the construction of the heat pipe can be up to 450°C.
Flat-plate collectors are cheaper because they are simple in construction and easy to manufacture. The construction consists of a thermally insulated plastic or metal bucket, in which the absorber is located. The collector is covered with a special hail-proof solar glass. Decisive disadvantage: the poor insulation of simple glass. Each modern window has a better insulation. In case of damage, the entire panel must be replaced from the roof. Large differences in quality depending on the manufacturer and construction; the best panels are very well suited for water heating. It is an cheap solar heat system if You hav ideal aligned and shade- free roof.