T. Muller*. W. Wagner, R. Hausner, AEE INTEC, Gleisdorf, Austria,

M. Kohl, S. Herkel, Fraunhofer ISE, Freiburg, Germany,

B. Orel, National Institute of Chemistry, Ljubljana, Slovenia,

K. Hofler, TB fur Bauphysik, Graz, Austria

* Phone: +43 3112 5886 16, Fax: +43 3112 5886 16, email: t. mueller@aee. at

Coloured absorbers are a major demand of architects for the design of fagade integrated solar thermal collectors. But coloured absorbers have shown an inferior thermal performance compared to selective coatings of state-of-the-art collectors so far. Within the project Colourface selective colour coatings have been developed and ageing tests of the coatings have been performed. Four colours have been chosen as absorber coatings for test collectors. The colours were blue, green, auburn and grey. The efficiency of these test collectors was measured using the dynamic collector test method according to EN 12975-2. The blue and green coloured absorbers have shown thermal performances comparable to black solar varnish coated absorbers. The auburn coating showed less absorptivity but also less emissivity than blue and green resulting in a slightly lower efficiency curve. The efficiency of the grey coated absorber was the lowest of all tested collectors as it was expected. Seven wall constructions that are commonly used in Austria and Germany have been investigated to find out whether the direct integration of collectors into the wall is possible without harming the building materials or. Finally, two pilot systems — a newly constructed two-family house and a retrofit building — have been realised with fagade collectors. Temperatures and relative humidities in the collector and inside the wall construction have been monitored and analysed. The results of the project are presented in this paper.

Development of Paints

Thickness insensitive spectrally selective (TISS) paints have been developed by KI, the National Institute of Chemistry in Ljubljana, Slovenia. Several compositions of low-emitting pigments, coloured low-emitting pigments and black absorbing pigments have been screened with respect to their spectral selective properties in combination with a good colour effect. Finally three colours (blue, green, auburn) with absorptivity values of a > 0.8 and emissivity values of є < 0.5 have been selected to be used for test collectors and two pilot systems. Additionally, the colour grey was chosen as a fourth colour since architects see a high application potential for this colour.

Testing of Paints

The testing of the selectivity of the colours has been performed by Fraunhofer ISE in Freiburg, Germany. Absorption and emission values before and after ageing tests have been measured for all colour samples. Temperature tests were conducted at 178°C. Condensation tests were performed with a sample temperature of 40°C. Both tests were repeated with exposure of the samples to UV radiation. Only the samples which have shown no significant changes after the tests have been selected for the coating of the test collectors and the collectors for the pilot systems.