Air gap underneath a solar panel?

[monkeyodeath]

Mounting a big ol' 305W solar panel to the top of my hardshell RTT and I'm wondering how much space I should leave beneath the panel and the roof for adequate cooling.

The panel is residential and has a plastic frame with a pretty tall standoff (4" or so). Figuring I'll want to cut it down a bit but not sure how far to go. I'd like to keep the panel cool (it's gonna spend a lot of time in hot places), but would also not like a giant windsail dragging my truck down.

Any thoughts?

 

[shade]

I've seen as low as 1" recommended, with the knowledge that less cooling will decrease output. I'd be concerned about the possibility of overheating the shell of your RTT, so keep an eye on that.

 

[monkeyodeath]

Shell is aluminum (Bundutop) so I don't think that's a huge concern.

Wondering if it might help if I fabbed up a little fairing for the front of it, just to keep some of the wind forces under control.

 

[john61ct]

Ideal is a tilting rack setup, get as close as you like for aerodynamics

then tilt it up to get almost double the watts out of it, depending on the season and your latitude

 

[Joe917]

We have 1 1/2 inches under our 315 watt glass panels, works well.
As for tilting set ups they are more trouble than they are worth.

 

[dreadlocks]

Ive got about 11in under mine.. aero is over-rated

Do whatever works for you, just dont let other stuff on the roof shade it..

 

[john61ct]

tilting set ups they are more trouble than they are worth.

Maybe if you have a big roof.

But when space is very limited, doubling your Ah/day solar production can pay for itself in reduced genset runtime very quickly.

Even more so if it allows you to boondock fulltime without ever buying one.

 

[rruff]

doubling your Ah/day solar production

Only if you are over 40deg latitude in winter. If so then tilting is a good idea. If you head south for the winter, I wouldn't bother. In summer you will actually get more with the panel flat.

It's good to remember that you need to orient your vehicle towards the sun if you want to tilt. And for either case you need to park in the sun. IMO it makes more sense to forget about tilt and bring a portable panel for when there is too much shade.

 

[john61ct]

Well fair points in there, we could go back and forth into the weeds on much of it, but most importantly

I just thought the opinion I responded to was very much an over-generalisation.

 

[Alloy]

Ideal is a tilting rack setup, get as close as you like for aerodynamics

then tilt it up to get almost double the watts out of it, depending on the season and your latitude

We are at 49 degees North.

Tilting will double the output Oct-March but not the duration.

With portable panel(s) set perpendicular to the sun twice a day we get 2-3 more hours Spring/Fall and 1-2 hours in the winter.


A 4" airgap will provide 2.5% more output vs. 1 1/2" airgap. There is little gain over 4".

 

[Alloy]

Shell is aluminum (Bundutop) so I don't think that's a huge concern.

Wondering if it might help if I fabbed up a little fairing for the front of it, just to keep some of the wind forces under control.

Won't hurt the aluminum but it will affect glues caulking on the aluminum.

 

[john61ct]

eponysterical

 

[rayra]

i'd allow for some ventilation or crossflow of the space under the panel, with the height mattering less.

I'd also thought to cut down the side height of the aluminum framing of my folding panel, but figured a way to craft the mounting frame on the roof deck so that the panel frame height didn't matter much. So then I drilled a lot of large holes in the sides of the frame so the panel can breathe some in the mount.

There's about a 3/16" gap between the sides of the panel frame and the mount frame and the vent holes are in that gap area.

I relocated my controller off the panel back into the vehicle, so it isn't cooking on my roof.