Shock, deformation, solidness and corrosion tests of laser-welded absorbers are all described in the “mirotherm absorber fact book”. This book can serve as a best practice resource for testing standards of new absorber and collector panels in the sector. Photo: Alanod
It ought to be the rule in any industrial sector to comprehensively test products that are new to the market – especially when you would like the products to enjoy a long lifetime. The recently published “mirotherm absorber fact book” (see attached document) shows in an impressive way how a new product in the solar thermal sector, like a laser welded aluminium absorber, was tested. The authors of the documentation, the coating specialists from the German Alanod-Solar GmbH & Co. KG, filled more than 40 pages with testimonials and examples of deformation, solidness, corrosion or outdoor tests, all conducted by the solar thermal industry. They intend to reassure the quality and durability of aluminium laser-welded solar thermal absorbers in their customers’ own words. But besides that, this book can serve as a best practice resource for testing standards of new absorber and collector panels in the sector.
The most important quality tests for laser-welded aluminium absorbers are shock tests, during which the testers will heat the absorber to the desired temperature between 100 and 220 °C and rapidly cool it down several minutes later with cold tap water flowing through the pipes. The overall results were positive. “After 20 cycles between 220 and 20 C° and 1,000 cycles between 100 and 60 °C, the welding between aluminium sheet and copper piping has remained largely intact,“ the researchers of the Swiss institute SPF, whom the German manufacturer Wagner & Co Solartechnik GmbH contracted to do the testing, stated in their test report. But they also found a significant bending or curving of the absorber, which could lead to problems, depending on how the installer mounts the absorber on the collector casing. The same institute carried out another series of shock tests on behalf of the Austrian collector manufacturer Greenonetec. The results were promising, too: “The integrity of the laser-welded joint is not affected in any way by thermal shock, even after 2000 cycles.”