Good Sam Club Open Roads Forum: Tech Issues: Solar panels vs shade cloth
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 > Solar panels vs shade cloth

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Almot

out there

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Posted: 07/02/21 08:18pm Link  |  Quote  |  Print  |  Notify Moderator

Panels won't cover your entire roof, and your walls will remain uninsulated. If you're going to sleep in there in a hot weather, there is a lot more work to be done.

valhalla360

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Posted: 07/03/21 08:44am Link  |  Quote  |  Print  |  Notify Moderator

The size of the air gap probably makes a big differrnce.

White roof material, reflects heat.
Black solar panels absorb it.

If there is a big gap, good chance the air carries the heat away before it hits the roof.
If there is only 1", good chance it concentrates and then radiates it into the roof.


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Itinerant1

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Posted: 07/03/21 09:33am Link  |  Quote  |  Print  |  Notify Moderator

Nothing scientific here 80f outside ambient with barely a breeze, using the infrared thermometer just hit these spots. 89.9f on the rv roof, 93.2f on top of panel, 94 on roof under the panel.

There is 2" space between bottom aluminum edging around the panel to rv roof and another 2" space from the bottom edging to underside of panel.

Edit: producing 55a, 749w at 10:00

I'll catch a reading later in the day when it's hot.

Looks like this.

[image]

The sun is out and suppose to be a warm one today near 95f.

* This post was edited 07/03/21 10:04am by Itinerant1 *


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mr_andyj

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Posted: 07/03/21 10:06am Link  |  Quote  |  Print  |  Notify Moderator

Your roof ceiling structure might be 1 inch thick. Those slats/frame members run side to side. Get some 1 inch thick wood and bolt them the entire length of the trailer, front to back, to the metal slats. This give you 2 inches of structure to place two layers of 1 inch foam board insulation. 1 inch will not be enough insulation! Add 2 inches.

You will add the top layer, then bolt in the wood with self-tapping screws of the right length (1 5/8ths) , then add the second layer, then add some thin venire or 1/8 plywood or paneling for the ceiling. Mark on the walls where the metal slats are and measure out to the center of the wood boards and take notes so after the ceiling goes up you know where the framework is, this helps to know where to screw in the ceiling board too.

And, yes, the panels will keep it cooler a little. The panels just physically cannot transfer al that heat across the air gap.

noteven

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Posted: 07/03/21 12:16pm Link  |  Quote  |  Print  |  Notify Moderator

I suspected there would be some temp gain via the panels.

Thanks for the temp measurements and insulation ideas.

Itinerant1

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Posted: 07/03/21 02:19pm Link  |  Quote  |  Print  |  Notify Moderator

Just a follow up. It's 97f ambient, rv roof is showing 97f, top of solar panel 101f, rv roof under solar panel is 104f and that's 4" of space so not much cooling going on.

n0arp

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Posted: 07/03/21 03:10pm Link  |  Quote  |  Print  |  Notify Moderator

I need to get a IR temp gun out and see, but there is a large difference in roof temps in similar conditions between our two rigs (by feel, when I'm up on the roof on hot days for whatever reasons). We cover almost the entire roof on each rig, but the the truck camper panels are much higher and the roof much cooler to the touch.

That being said, I do feel like it's easier to keep our fifth wheel cool with the panels on, but that is hard to quantify because of other changes we made at the same time we added them.

[image]

You can see the panels cover most of the roof, but are only about an inch or inch and a half (it's been a while since I've looked at it) off the surface. The roof is also FlexArmor, which seemed to make a difference itself, and was on there long before we added solar.

[image]

Truck camper roof - we still have the 14-5/8" tall factory rooftop AC, so the tops of the panels are 15-3/4" off the roof. Maybe one of these days I'll find a low profile unit, but it's pretty far down the priority list as we're under 13' tall.

* This post was edited 07/03/21 03:32pm by n0arp *


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Itinerant1

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Posted: 07/03/21 03:29pm Link  |  Quote  |  Print  |  Notify Moderator

I think the entire trailer contributes to heat or cold felt. Solar panels are made to produce power and never gave a thought to them shading or help cool the trailer until I turn the A/C on then they're contributing to the power to run the A/C. [emoticon]

MEXICOWANDERER

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Posted: 07/03/21 06:05pm Link  |  Quote  |  Print  |  Notify Moderator

The exterior is aluminum, and few things conduct thermally as good as aluminum. My concrete umbilical is painted OSHA white, while the roof is 3" reinforced concrete covered with tar and solid white pea gravel. The bare concrete ceiling on the inside frequently measures 111F. I audited the shade factor and came to the conclusion, due to heat transfer, the entire structure would have to be shaded.

I would have loved to have a 2-axle U-Haul enclosed trailer with side and end flaps clad plus roof clad in solar voltaic panels. Rig in shade, trailer in full sun.

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