Fourth experiment was just an air gap. I made a makeshift frame from 20mm x 20mm extrusion. The panel is spaced roughly 20mm off the roof of the camper.
Overall, inside there’s a 10 degree F difference between the untreated and treated panels, and a 12 degree F difference between the treated area and the roof. This is basically in the same ballpark as all the others.
However on the front face the difference is significant. The solar cell is reading approx 134 deg, a difference of 19 degrees between the two panels. This is as good or better than all other methods in terms of keeping the panels cool, which increases efficiency and panel life.
At this point, I am feeling some mild regret at buying flexible panels, because I’m probably just going to have to build a frame for them no matter what. When I feel like this I usually have to recall my priorities:
- Lowest possible weight.
- Good efficiency.
- Good aerodynamics.
All these goals can still likely be achieved with these panels. It’s just more work and more time. Given that the Beef Bars that I ordered are heavy (for good reason) a minimalist lightweight extrusion frame can still be a winner. And I can design some kind of treatment on the front to keep it from impacting aerodynamics too much. At 20mm square, there’s also room to conceal the cable mess under the extrusion, which could be a win for aesthetics and durability, too.
I don’t plan to cover the entire roof with panels. One thought that came to mind is that it might be possible to laminate a reflective barrier material on the inside of the tent toward the hinge. I’d have the top third for light, and the bottom third for solar. I have some Reflectix arriving this weekend.
Lessons learned:
- Adding solar does not necessarily make the roof cooler.
- In fact, in my configuration it makes things hotter.
- Coroplast supports are not a very effective solution.
- An air gap of 20mm/1 inch significantly cools the panel.
- These measurements are a huge time investment because you have to wait for heat soak.
- The camper is going to need fans inside to be a comfortable working environment.