• What are solar thermal systems made of?

    Flat plat collectors are made of metal, glass, insulating and joining materials. Typically copper, steel or aluminium is used for the absorber configuration. The sides and bottom of the collector are usually metal and insulated with mineral wool to minimize heat loss. The glass top is made of special glass to resist facture and maximise transmission of energy. In the future, a variety of materials and combinations of materials including plastics may be used to improve cost benefits ratios, higher temperature ranges and systems performance.

    Vacuum tubes collectors are made of a borosilicate glass. Mostly the absorber layer is coated on the inner tube and no metal is required. But there are also tubes with an inner metal fin absorber.

    For swimming pool heating, plastic or rubber are used to make low-temperature absorber plates.

    The solar collector is usually mounted on the roof and is connected to a circuit containing water with propylene glycol anti-freeze added. The tank is also made of metal, partly stainless steel, partly enamelled steel or copper.

  • What can solar thermal technology be used for?

    There is a wide variety of applications for solar thermal technology. The most common application is the heating of pool water, the heating of domestic hot water and space heating. Not very wide spread yet are solar cooling systems, because of the complexity of the technology and the high initial investment costs. Also, process heat applications such as in breweries or car washes, as well as in the food and textile industries, are still in their infancy. You can search for all these different kinds of applications in the filter section market sectors on the right hand side of the page.

    What is the difference between vacuum tube collectors and flat plate collectors? With flat plate glazed collectors the absorbers are fitted in a box closed by a pane of glass (90 % market share in 2009 in Europe). Vacuum tube collectors – which are the dominating technology in China (96 % market share in 2008) – have the absorber coating on the outside of the inner tube in placed within an evacuated glass tube. Generally speaking, the advantage of vacuum tubes is a higher efficiency (less space required for the collector on the roof) and higher temperatures (necessary for process heat and some solar cooling technologies).

    The disadvantage: The vacuum tubes produced in Europe are more expensive than the flat plate collectors but in some incentive schemes like in Germany they receive the same grants as the flat plate collectors. In China, some locally produced vacuum tube collectors have a poor quality performance, flat plate collectors are seen as high-quality products.


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