Hi. Whoever has a flexi sat panel up on top can you tell me if you used any 'plastic cardboard' underneath? As insulation stopping the panel getting too hot. A few vids I've watched attach panel directly to pop top others put a piece of 4-5mm plastic unferneath (the type with channels of air on) . I am about to begin installing mine and this has raised a question.
Mine are directly on the fibreglass roof. It's basically plastic so I dont see how adding more plastic will help Sent from my Pixel 4 using Tapatalk
Mine are glued to the poptop directly. It was a cheap solution involving small amounts of some PU glue I had anyway . So they are only glued with thin beads, open at the sides . They do get very hot. But then the reason they get hot is the 400 watts of wasted energy each from bright sunlight. And in bright sunlight, losing a bit of power is not important. May also be down to the panels I have lose power very gradually as they get hot .. says temperature coefficient about -0.38% per degree C., max temperature 85 degrees C. So even when they are too hot to touch they are still around 70 watts out. And they recover when they cool off like all solar panels should.
Yes , how fast does the air flow have to be to change the air to actually move heat, and how big are the channels ? It may only work when you are driving or its very windy... You also may find if you dont get air flow through the channels it acts as double glazing and the solar panel gets hotter than if it were cooled by heat conduction into the poptop... some grot in the ends of the channels will not help cooling too.. In other words either a big gap as you would have with a rigid panel providing air flow using e.g. 25mm high plastic channels or no gap and conduction both work .. Of course the conduction approach makes the underside of the poptop get hot too.. Somewhere around 85C the resin in fibreglass starts to soften. Filling the plastic channels with coolant and circulating it to a radiator with a fan or using an air cooling fan could cost more energy than just letting the panels get hot. But it might work for a few more watts.. I have a greenhouse that has a 5 watt poly panel and a 12 volt PC cooling fan that has ventilated it for years, keeping it cool in summer and ventilated in winter..so it could work..
Fitting these things commercially has shown that they get hot wherever they are, the efficiency drop is allowed for but the warming of a poptop isn't, suggest you open a couple of windows or fit a low power fan to move muggy air around. As long as the coating on the pop top is suitable for exposure to normal levels of sunlight it should be ok.
However we dont usually deliberately paint the poptop matt black.....which is what an 80% loss/20% efficient solar panel represents.
