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Fortschritte bei transparenten Wärmedämmaterialien

: Platzer, W.; Wittwer, V.

Deutsche Gesellschaft für Sonnenenergie e.V. -DGS-, München:
7. Internationales Sonnenforum 1990. Tagungsbericht. Rationelle Energieverwendung und Nutzung erneuerbarer Energiequellen im regionalen und kommunalen Bereich. Bd.1
München: DGS-Sonnenenergie-Verlags GmbH; Sonnenenergie-Verlags-GmbH, 1990
Internationales Sonnenforum <7, 1990, Frankfurt>
Fraunhofer ISE ()

Four fields of material development can be identified. If one uses granulated aerogel with different mean sphere diameters, the heat conductivity scales approximately linearly with this diameter, whereas transmittance measurements show a markedly reduced value below 3 mm, but minor variation of transmittance above 3 mm diameter. From results of an optmisation of rectangular polycarbonate honeycombs, a new material has been produced which, in spite of some limitations due to the production process, shows a 10 precent decrease in thermal conductance when compared to the previous design. The solar characteristics of the materials are identical. Capillary structures produced from different plastics, which may withstand higher temperatures than the usual ones, have been investigated. Some materials, in particular a special PMMA capillary, showed very good performance, whereas others have difficulties in reaching sufficiently high solar transmittances. The production of glass capillary plat es is difficult. Nevertheless a plate of 40 mm thickness has been manufactured. The performance still has to be improved.