Monday, Jun 19, 2023 at 11:45
Allan,
I used the "Corflute" as most know what that looks like, the actual product to use is as you suggest twin wall ploycarbonate as it has similar expansion rate to the panels.
The mounting of the panels is very important to prevent panel failure due to expansion and contract, many complain the panels didn't last long but then they also indicate they didn't mount them as advised but used their own system. Placement of the support strips is important as
well as the direction they are placed. The length of the strips is also important, if they are to long they will expand to much and stress the panel.
The reason you mount them on the strips is the construction of the strips has some "give" in it which allows them to distort somewhat as the panels expand and contract preventing stressing of the panels. Same for the double sided tape used to mount the strips, it has a flexible foam core which again allows for some movement expansion and contraction without stressing the panels . The original mounting medium used was a butly putting type high bond adhesive which again allowed for some movement. Up above it was suggested to use a silicon type adhesive to bound the panels to the roof, as long as thickness and height of the bed is used is tightly controlled and applied at sufficient spacing to allow the panels and the roof they are mounted to to expand at different rates and not stress the panels then that should work ok too. But again care needs to be taken not to form a sealed areas under the panles with the adhesive that can allow a pressure bubble to form under the panel which will stress it.
From memory the polycarbonate strips are around 10mm high, by the time you add the double sided tape to them it makes then probably around 14mm high which is probably similar to a glass panel mounted on brackets. The mounting strips a mounted across the narrow dimension of the panels so not that condusive to air flow at least in my case that is. There is gaps in the strips if mounted correctly though that would let some air flow though the main cooling affect while travelling would be from air passing over the top of the panel.
The mounting under the panel is more about preventing stress on the panel than cooling.
People say that without airflow under the panel they will overheat, look at
solar blankets, there is no airflow under the panel. I have read where people indicate their
solar blanket overheated while laying on the ground, I have used
solar blankets laying on a plastic sheet on the ground for years and haven't had one fail yet so seems luck of the draw. With my house
solar panels the angles is low, their is very little gap under the panels, there are 3 stacked together and they are on a black roof so I doubt there would be much cooling affect due to convection cooling under the panels going on there either and given the speed at which they heat up and cool down as the sun shine varies on a cloudy day I would say that is pretty much the case.
In my own setup the flexibles are mounted on a crossover vans fibreglass roof. I have the cells facing out on the edge supports so any wind blowing can "vent" under the panels. The roof also has a considerable slope on it so air flow can get going due to convection but there still wouldn't be much airflow. They have so far been there for 3 years and touch wood are still performing
well.
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