I've been thinking of drilling my 100W hard panel frames for airflow and lightness

[NPhil]

They will ride on top of a minivan, low on the roof when the vehicle is in motion or in need of a degree of stealth, optionally lifted and tilted when parked where maximum power production is my priority. Today I tested a Reflectix-type barrier between the panels and the roof, which seemed effective at lowering the amount if IR coming off the back of the panels and being absorbed by the roof of the vehicle, which I assume will decrease the heat load in the cabin. But now I think I will need to remove more heat from the back of the panels in another way than radiation. Another design goal is to keep an unusual amount of complexity up there light, and not too tall. There will be additional structure supporting the panels, since they have to tilt as a unit, and there are some sliding panels underneath.

I'm also curious about bending the rigid panels, since the front panel and rear panel will meet a curved roof at an angle, and the aerodynamics will be much more easily done if the panels can at least meet the curve of the roof halfway. The reason I think this may be possible is that one of my test panels was purchased at a discount and has a kink in the frame which visibly bends the glass. I've been testing with it more many months, it produces well enough, as far as I can tell.

 

[rodrick]

bending a panel puts stress on the glass it may not break right away but it Will most likely when vibration from the vehicle’s movement or expansion and contraction from temperature changes starts to add more stress, I don’t think it will end well

 

[NPhil]

bending a panel puts stress on the glass it may not break right away bit it Will most likely when vibration from the vehicle’s movement or expansion and contraction from temperature changes starts to add more stress, I don’t think it will end well

That does seem likely. Still, it's interesting how visibly that glass is bent, with no sign of cracking. It doesn't ride around on the vehicle at this time, but I have been handling it, to remove and stow it most every night, and unstow and set on the vehicle most every morning, for about a year.

 

[Supervstech]

That does seem likely. Still, it's interesting how visibly that glass is bent, with no sign of cracking. It doesn't ride around on the vehicle at this time, but I have been handling it, to remove and stow it most every night, and unstow and set on the vehicle most every morning, for about a year.

I'd guess a bend isn't causing any issues, but bending back and forth would certainly cause failure.

 

[HarryN]

You might be surprised at how little people actually notice things on top of a mini van.

This is a 2000 Dodge mini van that I used to have. Those are 2 each, 140 watt panels, roughly 26 x 58 inches.

In this area, it is so common for people to have ski racks and other stuff on vehicles that most people didn't even notice.

It looks really obvious in the photos but since it is sort of eye level for some reason people didn't seem to observe it.

As far as cooling - the shade plus air gap actually reduces the heat load on the roof, but the air gap is important.

 

[HarryN]

To be honest, 100 watts of solar is more or less a trickle charger. It is more or less not worth the effort IMHO. Solar on a van becomes useful at 300 - 400 watts.

 

[Supervstech]

To be honest, 100 watts of solar is more or less a trickle charger. It is more or less not worth the effort IMHO. Solar on a van becomes useful at 300 - 400 watts.

Who posted in this thread about a single 100watt array?

 

[HarryN]

Who posted in this thread about a single 100watt array?

I may have misunderstood the title that talks about 100 watts. Perhaps he has multiple. My mistake.

 

[HRTKD]

No way would I introduce a bend to my rigid panels. A bent panel is under stress. Hit a hard bump and the glass could shatter since it's already stressed.

 

[NPhil]

To be honest, 100 watts of solar is more or less a trickle charger. It is more or less not worth the effort IMHO. Solar on a van becomes useful at 300 - 400 watts.

I'm using 100W hard panels because I can fit four of them on the minivan roof without hanging out on the edges like the Dodge in the photo above, with four more flexible panels to be added underneath, they will slide out when the vehicle is not in motion (that part is more complicated, I've been designing it in my head for a while).

 

[NPhil]

No way would I introduce a bend to my rigid panels. A bent panel is under stress. Hit a hard bump and the glass could shatter since it's already stressed.

I could argue that this isn't my exact situation. I already have a panel with a bend, and it is a fairly sharp kink in one spot on the long edge. I'm thinking of smoothing it out into a (comparatively) gentle curve. I guess I should wear safety glasses at all times while doing that, anytime I am near it afterward, and, any time other people are near, they could wear safety glasses I hand out the way theaters used to hand out 3D glasses.

 

[sailingharry]

I could argue that this isn't my exact situation. I already have a panel with a bend, and it is a fairly sharp kink in one spot on the long edge. I'm thinking of smoothing it out into a (comparatively) gentle curve. I guess I should wear safety glasses at all times while doing that, anytime I am near it afterward, and, any time other people are near, they could wear safety glasses I hand out the way theaters used to hand out 3D glasses.

It's not a safety concern. I shattered a rigid panel on our boat, and while the glass rained down for weeks (months?), none of the pieces were sharp and none were over the size of a peanut. So, it is potentially a financial risk (who wants to buy a new panel!), but no safety risk.

But, on the bend. I had a boat with plastic windows. Everyone said that the cabin side curved, and glass wouldn't work. I put a 1/2" bend in a 30" long (by 6" wide) tempered glass window, and 5 years later I sold the boat with the windows still looking good. Not sure how much more would work....