New solar install.... - Page 4 - Fiberglass RV


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Old 09-23-2011, 12:20 PM   #43
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Bought a Solar Panel

My plan is to purchase two 40 watt solar panels. I bought the first one today, planning to test it before I buy the second. The testing is with hopes of resolving the issues of temperature many of you have mentioned.

It's a 40 watt panel that weighs 4.4 lbs and is about 2.5 x 1.5 feet and a 0.1 inches thick.

I paid $212 including shipping, a little higher than more traditionally manufactured panels but I was interested in low weight and small size.
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Old 09-24-2011, 03:13 PM   #44
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Originally Posted by cpaharley2008 View Post
You are right, my word choice was wrong, maybe an irreversible mistake would have been a better choice. I think that the panels attached directly to the fiberglass with VHB not only would cause the panels to deteriorate quicker but the fiberglass underneath may also suffer some sort of damage. Jim Palmer, the builder of the EggCamper and fiberglass manipulator told me several times that fiberglass is porous. I think the tape would also suffer and somehow become absorbed into the glass when faced with the high temperatures created under the solar panels. The temperature must be relieved somehow and it will take the easiest egress. Either back up thru the panel or down thru the roof. IMHO
The UniSolar panels that were referenced previously are peel and stick, they are designed to be attached directly to a surface so they should not deteriorate quicker because they are directly attached, they were never supposed to have an air space under them. They are not attached with VHB tape. If VHB tape causes an issue with fiberglass because of porosity and gets absorbed into the fiberglass as suggested, that may be an issue for those people that have used VHB tape to install rigid solar panel mounting brackets.

In the link below in post #3 they mention that they have been using UniSolar panels for 7 years on their 4x4 all terrain campers and consider them "first choice every time" if space permits. It looks to me that their campers are made from fiberglass and are very well made. They are used in Australia, many times in the hot sun of the desert. Lots of interesting solar panel discussion in the link.

Stick on solar panels for camper shells?

The web site for the 4x4 all terrain campers.

4x4 Motor Homes
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Old 09-24-2011, 03:41 PM   #45
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Quote:
Originally Posted by cpaharley2008 View Post
Jim Palmer, the builder of the EggCamper and fiberglass manipulator told me several times that fiberglass is porous. I think the tape would also suffer and somehow become absorbed into the glass when faced with the high temperatures created under the solar panels. The temperature must be relieved somehow and it will take the easiest egress. Either back up thru the panel or down thru the roof. IMHO
While the gelcoat might be stained by the tape, gelcoat is thick and a light sanding with fine grit paper and then a polishing will restore it's appearance.

You could say that gelcoat is porous. It would take many years with a hull in the water for gelcoat and the fiberglass underneath to absorb water. A fiberglass camper would dry out quicker than water could ever be absorbed. One season in Arizona would have it about as dry as it would get.

Boats get heavy with age because water is absorbed, and these are sitting in the water. If water can drain away, it will not be absorbed.

I don't think this would matter.
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Old 09-24-2011, 06:14 PM   #46
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I just read that whole thread at expeditionportal.com. It's great information, even though I don't understand it all.

My question is, in light of the following quote from that thread, would excessive heat buildup under a stick-on panel on a fiberglass trailer still be a serious concern?

Quote:
Given solar panels are relatively dark they are good heat absorbers. Having your solar panels above the roof by a couple inches allows for an air gap. Not knowing numbers, roughly 1/2 the heat gained by the solar panel will be radiated up and 1/2 will be radiated down. That halves the source heat for heat gain for the section of roof shaded by the solar panel. That means an easier to keep cool interior.

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Old 09-24-2011, 06:43 PM   #47
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Stick down panel

I bought a panel and plan to place it directly on the roof to test it. It is a tenth of an inch thick. When I've used it I'll report on its function on the roof.
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Old 09-24-2011, 07:28 PM   #48
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I'll look forward to hearing your results. I do like the idea of stick on panels if they won't cause problems.

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I bought a panel and plan to place it directly on the roof to test it. It is a tenth of an inch thick. When I've used it I'll report on its function on the roof.
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Old 09-24-2011, 08:16 PM   #49
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Originally Posted by Sharon G View Post
I just read that whole thread at expeditionportal.com. It's great information, even though I don't understand it all.

My question is, in light of the following quote from that thread, would excessive heat buildup under a stick-on panel on a fiberglass trailer still be a serious concern?
Upon reading the tread, my interpretation regarding placing the panels directly onto the fiberglass vs. mounting them above the roof:
Mounting above the roof would add extra "drag" (less gas milage).

Mounting above the roof would alleviate heat concerns

Placing panels directly on fiberglass would add minimum drag.

Placing panels directly on fiberglass may generate heat retention, which would heat up the cabin and compromise energy efficiency.

Placing panels directly on fiberglass may compromise the gelcoat and compromise the structural integrity of the panels.
Does this all sound right?
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Old 09-24-2011, 08:29 PM   #50
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solar panels directly onto the fiberglass vs. mounting them above the roof:
Mounting above the roof would add extra "drag" (less gas milage).

Mounting above the roof would alleviate heat concerns

Placing panels directly on fiberglass would add minimum drag.

Placing panels directly on fiberglass may generate heat retention, which would heat up the cabin and compromise energy efficiency.

Placing panels directly on fiberglass may compromise the gelcoat and compromise the structural integrity of the panels.
Does this all sound right?

Yes you have it right.

Those are the various thoughts. I have had solar panels on the roof of a another trailer, not fiberglass, and they did get hot, but I really can't say that it had much effect on the temperature inside the trailer, at least nothing I noticed. This time I'll measure it.

I am concerned about aerodynamics and appearance.

Hopefully we'll shortly have some answers.
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Old 09-24-2011, 08:50 PM   #51
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Originally Posted by Jane P. View Post
Upon reading the tread, my interpretation regarding placing the panels directly onto the fiberglass vs. mounting them above the roof:
Mounting above the roof would add extra "drag" (less gas milage).

Mounting above the roof would alleviate heat concerns

Placing panels directly on fiberglass would add minimum drag.

Placing panels directly on fiberglass may generate heat retention, which would heat up the cabin and compromise energy efficiency.

Placing panels directly on fiberglass may compromise the gelcoat and compromise the structural integrity of the panels.
Does this all sound right?
Mounting above the roof would add extra "drag" (less gas milage).True
Mounting above the roof would alleviate heat concerns If there are heat issues, an air gap would reduce the heat transfered to the roof.
Placing panels directly on fiberglass would add minimum drag True
Placing panels directly on fiberglass may generate heat retention, which would heat up the cabin and compromise energy efficiency. Mounting the panels directly on the roof would heat up the roof less than if that part of the roof was painted a dark color. The amorphous type of panels do not get the compromise in energy efficiency at high temperatures that the other two types (poly and mono) get.
Placing panels directly on fiberglass may compromise the gelcoat and compromise the structural integrity of the panels There was speculation that this could be a problem. I never saw anyone say what the running temperature was an the back side of a panel and compare that to the max allowable temperature of the fiberglass roof
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Old 09-24-2011, 09:15 PM   #52
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Placing panels directly on fiberglass may compromise the gelcoat and compromise the structural integrity of the panels There was speculation that this could be a problem. I never saw anyone say what the running temperature was an the back side of a panel and compare that to the max allowable temperature of the fiberglass roof[/QUOTE]

My crystaline solar panel reached 150F between the panel and roof. They sat about an inch off an aluminum roof.
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Old 09-24-2011, 09:19 PM   #53
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Placing panels directly on fiberglass may compromise the gelcoat and compromise the structural integrity of the panels There was speculation that this could be a problem. I never saw anyone say what the running temperature was an the back side of a panel and compare that to the max allowable temperature of the fiberglass roof


My crystaline solar panel reached 150F between the panel and roof. They sat about an inch off an aluminum roof.[/QUOTE]

That is one way to "cook" an Egg.
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Old 09-25-2011, 02:01 AM   #54
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I would not be terrible worried about the temperature of one small flexible solar panel. On the other hand, if you wanted to reduce heat and generate power, I like the idea of covering a roof with solar panels with a gap for air flow. That would be useful in a hot sunny climate.

Another option would be to stretch an awning over a roof. I've been in plenty of hot boats in the Caribbean where an awning made it more bearable. Like the attic of a house, or a third floor as a buffer, it makes sense.

I don't like tents, but some have merit. I like modern prestretched and woven materials, shrink wrap structures and PVC and dome structures. A large dome with good air flow would make a nice sun awning for a TV and camper in a long term location like a snow bird in Arizona.

In any case, using rigid solar panels as a sun awning serves two purposes--blocking heat and generating power. Run a small fan on low for cooling and perhaps the increased efficiency of the lower temperature would compensate for the fan draw. That would be an interesting experiment. One thing I learned building computers is even a small fan makes a big difference in a high heat environment.
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Old 09-25-2011, 08:59 AM   #55
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My crystaline solar panel reached 150F between the panel and roof.
I found some references that said fiberglass made with polyester resin is good up to 100C (212F) before the strength starts to deteriorate. The temperature limit is based on the formulation of the resin, with some types of resin, 300F or more is allowable.

From the the link to the 4x4 campers, the UniSolar panels (amorphous type) have been directly applied to the roofs and used successfully for at least 7 years. They are considered the 1st choice every time by the camper manufacturer.

There are plenty of fiberglass campers and boats that have been painted dark colors and I have not heard of fiberglass or gelcoat deterioration due to heat from the sun because of the color. The fiberglass under a stick on solar panel would heat up even less than the fiberglass under dark paint because some of the solar energy is drawn off in the form of electricity and the solar cell thickness would provide more resistance to heat flow than a thin layer of paint would provide.
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Old 09-25-2011, 09:10 AM   #56
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UniSolar panels (amorphous type) have been directly applied to the roofs and used successfully for at least 7 years. They are considered the 1st choice every time by the camper manufacturer.

UniSolar was my first choice however the 68 watt panel, the smallest I found for sale is much too long for a Scamp 16. Though the energy density (solar efficiency) is lower, it has other positive attributes. The only issue for me was it's physical size.

I looked at UniSolars 31 watt panel but never found one for sale. I also read an article where a guy cut a 68 watter in half to get it to fit but that's not for me.

Soon enough we'll have the first of our two 40 watters and installation can begin.
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