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Solar electricity and heat from one element
Hybrid collector from Germany: Solar cells lie within the cover plate of an otherwise conventional flat-plate collector. Photo: Solarhybrid
The German company Solarhybrid AG has developed a hybrid collector which generates electricity and heat simultaneously from sunlight. The solar cells lie within the cover plate of an otherwise conventional flat-plate collector. The solar cells take up the visible light while the solar heating collector gets its energy from the infra-red light. The solar cells shadow the absorber to a certain extent, and according to the company the heat transfer isn`t quite enough to completely counter the shading effect. This means that a somewhat higher collector area has to be planned in than when using a straight solar thermal collector system, but you do get electricity from the photovoltaic system as a secondary product. The company brochure says that the solar thermal part of the system acts as effective cooling that helps the photovoltaic part reach an increase in efficiency of up to 25 %.
In order for the cooling of the solar cells to work in solar hybrid systems, the collector must not be allowed to go into stagnation, i.e. it must always be able to transfer heat away. According to Solarhybrid the system storage is thus designed so that the collectors can transfer heat even if the sun shines brightly the whole day. Should excess heat still be present late in the day, it is then discharged in the evening and during the night via the collector area so that the solar storage is ready to take up heat again the next day. Heat losses have to be taken.
As of the end of the year the company plans to have a thermo-generator on sale which can generate electricity from excess heat using the Seebeck effect. In the Seebeck effect, a voltage is generated between two points of a conductor which are at different temperatures. The Solarhybrid system should pay for itself within eight to twelve years through the photovoltaic tariffs and savings on fossil fuels for heating.
This text was written by Joachim Berner, a German journalist and solar thermal expert.