It’s been a while since the last update, I know. The truth is that this project didn’t turn out quite as planned. The collector is producing a lot more heat than what I expected, so much that it’s damaging the PV panels. I’ve recorded a collector temperature in this video that’s in excess of 100°C (212°F). The main issue is that the EVA film is melting, and both it and the cells are running down the inclined array when it heats up.
I’ve gone back to the drawing board and redesigned the system with an uncovered configuration, meaning that the PV panels won’t be enclosed in glass as they are now. This will help them to operate quite a bit cooler and prevent damaging the encapsulant – the waste heat from the PV panels will still serve to preheat the air stream entering the collector. The centre portion of the array will simply be a flat thermal collector (I may add louvred screen or heat pipes later) that will finish heating the air stream before it’s diverted back into the house. The new PV panels also have a 20 mil UV stabilised polycarbonate glazing to prevent the EVA film from ‘running’, just in case the temperature of the new uncovered panels rises above the film’s melting point during the hot summer months. I will probably place one new panel inside of the covered flat thermal collector portion, just to see how well it holds up to the heat with the polycarbonate glazing protecting the EVA film. More updates coming soon!