Roll-bond panels are produced by screen printing the channel pattern on an aluminium sheet with a separating ink, rolling it together with another aluminium sheet at high pressure and high temperature and finally inflating the channels with pressurized air. Due to this process it is not possible to use pre­coated aluminium sheets, because the selective coating would suffer damages during the rolling process. Therefore it is necessary to apply the selective coating after the roll-bond absorbers have been built, which is only possible with a batch coating plant. Batch coating plants which can apply sputtered coatings on glass panes already exist. One aim of the BIONICOL project is to adapt such a plant of an industry partner in order to be able to coat the roll-bond absorbers.

2.2. Development and testing of appropriate heat transfer fluids

Roll-bond solar absorber were already built in the seventies and eighties, but then vanished from the market. One reason for this was the fact that corrosion occurred in some of the absorbers. Therefore one of the most important tasks within the project is the development and comparative examination of a tailor-made inhibited glycol based heat transfer fluid. The intended experimental work comprises ASTM D 1384 related corrosion tests as well as the investigation of solar fluids operated under varying field test conditions. Moreover, it is also planned to carry out corrosion tests of fluids in a closed cycle with roll-bond panels in an early stage of the project.