Solar on the roof gets HOT!!!!

[TucsonAZ]

I was thinking my roof would be shaded due to all the panels and it would be cooler but man was I wrong!  I just sold the step van it was mounted on and removed all the solar, the paint under the solar was actually bubbled!  It lasted 17 years in the southern AZ heat and sun and was fine until then.  

I did not have any airflow side to side, only front to back and they were mounted only 3/4 of an inch from the roof so that no doubt was a huge part of the issue but I have learned my lesson and next time will be mounting them much higher up with a lot of airflow.  Granted, my roof was roughly 160sqft and 110sqft of that was covered in solar.

 

[LeeRevell]

Hmmm..... first I have read or heard of that possibility! You never noticed increased heat inside the van?

 

[SoulRaven]

The most miserable summer of my life was in a heavily insulated cargo van, covered with solar panels. They had about 3" clearance but the roof would get too hot to touch.

I couldn't park in the shade, or they wouldn't work. Absolute hell on Earth.

Since I prefer to park in the shade in the summer, that is just one of many reasons that I no longer use solar panels.

 

[Wabbit]

I have been trying to think of a way to deal with this. Was kinda hoping since I didn't hear it mentioned that it was just the solar panels I had been using(HF 50w cheapies). A solution that would work(I think) is a weatherproof reflextic type of layer. Haven't gotten around to researching it yet, but some ideas(most discarded) were, reflextix, mylar blanket, some type of paint, more space between panels and roof.

 

[vtwinkicker]

I was thinking my roof would be shaded due to all the panels and it would be cooler but man was I wrong!  I just sold the step van it was mounted on and removed all the solar, the paint under the solar was actually bubbled!  It lasted 17 years in the southern AZ heat and sun and was fine until then.  

I did not have any airflow side to side, only front to back and they were mounted only 3/4 of an inch from the roof so that no doubt was a huge part of the issue but I have learned my lesson and next time will be mounting them much higher up with a lot of airflow.  Granted, my roof was roughly 160sqft and 110sqft of that was covered in solar.

I saw a chart a ways back that showed the different temperatures of car hoods by color. They ranged from about 130F for white to near 180F for black. OUCH!

 

[Wabbit]

After reading a few other posts/ideas from the great and wonderful net, I am planning on a reflective type material. Will be removed when traveling. Find a couple links below, both come with grommets to secure it to roof. I am leaning towards the cheaper option. If I get 3 panels on roof, the size is about perfect and the noise from the wind flapping it around would be less than going larger(albeit more reflective, but not by much) option.

MPI All Weather Emergency Survival Blanket
http://www.amazon.com/MPI-Weather-E...lt_1&ref-refURL=http://www.cheaprvliving.com/
5x7 $29.37 w/Prime

SolaReflexx CoolTarp
http://cooltarp.com/
8x8 $109.00
8x16 $215.00

There are cheaper weather blankets, but if you can put any trust in the marketing, the other cheaper blankets touted 80% reflectivity, and the MPI 90% reflectivity.

 

[Almost There]

What will using the reflective tarp do to the underside of the solar panels?

Won't it cause a build up of heat under the panels themselves?

And won't this result in a lower productivity when the panels themselves become to hot?

NOTE that all questions are asked in total ignorance of what is on the underside of the panels or how they react to a build up of heat!

 

[Wabbit]

It would reflect it back at the panels. I was thinking the same thing, what is the impact on the panels. The renogy panels I am planning on going with have a temperature tolerance of -40f to 190f(there are efficiency losses though). I would/will monitor temps when I put this together with some type of thermometer.

And the panels I have used before do get very hot. VERY lol. Even when put out on the grass with a portable setup.

 

[MikeRuth]

Interesting comments. I don't have a reference yet as I just put the panels up on my van about a month ago.

I do know that my van sits in the sun and during the summer I would see temps inside of over 120. I never gave it any more thought as this is just typical valley summer in los angeles.

It has not got that hot yet, but on the days so far that have been rather warm, 90's I have noticed my van seems a bit cooler. This might be because it isn't that hot all day yet. It's those days were it's 100 by 10:00 am! that will be interesting.

 

[ccbreder]

3/4 inch is not much clearance.

 

[Wabbit]

...I did not have any airflow side to side, only front to back and they were mounted only 3/4 of an inch from the roof...

3/4 inch is not much clearance.

I did not see that clearance when I read that. Thanks for pointing that out ccbreder. I am planning on a larger clearance of around 4 inches or so. That 3/4 inch was prob the issue, but the space underneath my poly solar panels was still quite hot, even inches away. Any real world experience with vehicle roofs, clearance, and temps would be appreciated. It's quite possible that at a few inches clearance, this isn't an issue.

 

[Willy]

With my rigs I generally seek out the sun and they're nice 'n cool regardless of how hot it is. The roof is often near covered with solar, but is sno-coated white and I'll have my skookum fan setup evacuating air from inside against the bottom of my panels.. which cools both the roof and my solar. ..Willy.

 

[LeeRevell]

Bob has had the concept of a plywood sheet above the roof and under the panels. Shades the van and provides a mount for the panels. That's what I am planning to do.

 

[gypsychic]

https://vanlivingforum.com/showthr... it isn't very stealthy for a conversion van.

 

[TucsonAZ]

Oh, I noticed the heat inside, if it was sunny and even in the 60s outside the inside of the van was in the 90s quickly even with a two 100 plus cfm push/pull fan system. I also had a white roof and part way into my trip I pulled up the panels and added 1" of rigid foam insulation under the panels (I was closer to an inch of clearance at the frames, the glass was a full two inches from the roof) which had little to no impact. I had about 7 inches of space between banks of panels and in the early hours that area was far cooler to touch than under where the panels were mounted.

Some type of radiant coating on the roof would be a huge help I'm sure but this next time I'm getting the panels up higher with full airflow for sure.

 

[SoulRaven]

https://vanlivingforum.com/showthr...the opposite if I want the sun in the winter.

 

[SternWake]

My Kyocera framed panel has a junction box, which made it so that I could not mount it too close to the lightly insulated fiberglass roof.  It has at most 1.5 inches on the back half and 1/2" on the leading edge

Also with the curved surface of the roof, when air passes over the flat panel, it causes more air to flow underneath too.  I've also painted the panel frame white to make it somewhat less conspicuous.

Anyway, when I take temp readings with my IR gun on the lightly insulated  ceiling, it is coolest under the framed panel, hottest under the unisolar stick on panel, and unshaded open white roof is closer to the shaded temps.

My black glass conversion van windows are the biggest heat source in my Van, not the roof, and I predominately park in full sun whenever possible. However being near the ocean means the temperatures rarely get extremely hot, although it is forecast to get to near 90 today, but will be very dry too.

I keep surfboards strapped to my ceiling, and if it were to get too hot, the wax would melt and drip onto everything below and make a terrible mess.  A white exterior and adequate ventilation have made this a Non issue.  Even the surfboard under the stick on Unisolar panel does not have the wax melt.  it does get soft, but is not an issue.

 

[Canine]

Build a 6" plywood box on top of the van with an angled front.Put hinges and latches on one or both sides and mount your panels on top.That way you also have extra storage for long cumbersome things or things like extension cords or any of the other things we have to keep moving to get to something else.

 

[MikeRuth]

Build a 6" plywood box on top of the van with an angled front.Put hinges and latches on one or both sides and mount your panels on top.That way you also have extra storage for long cumbersome things or things like extension cords or any of the other things we have to keep moving to get to something else.

That's actually a focus of mine, might even go 8" if it seems reasonable. 
I think I could store a lot of stuff there that only needs to be accessible occasionally. 

 

[Wabbit]

Build a 6" plywood box on top of the van with an angled front.Put hinges and latches on one or both sides and mount your panels on top.That way you also have extra storage for long cumbersome things or things like extension cords or any of the other things we have to keep moving to get to something else.

If I don't get a high top, this seems like a great idea. Now to think on it and figure out a way to access the whole space that is created.

That's actually a focus of mine, might even go 8" if it seems reasonable. 
I think I could store a lot of stuff there that only needs to be accessible occasionally. 

I think you should get right on this...lol. If you do, I would really appreciate how it went and all that.