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Topic ClosedSolar wiring, chase through to roof?
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Motor7 View Drop Down
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Posts: 196 		Direct Link To This Post Topic: Solar wiring, chase through to roof?
    Posted: 20 Jul 2019 at 7:22am
There are 6 grommet holes on the solar panel. I'm going to caulk a line of Eternabond on the leading edge and the two ends, then screw it down using a stainless fender washer and stainless screw through each grommet. I will also pre-drill each hole to prevent the fiberglass from cracking/ splintering. I am not going to caulk the whole perimeter of the panel because I want any water trapped under it to escape.

I decided to screw and glue the panel down after reading several accounts of those only glued or taped flying off on the highway in high winds.
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offgrid View Drop Down
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Posts: 5290 		Direct Link To This Post Posted: 20 Jul 2019 at 8:08am
I used to design and perform reliability testing on solar modules. I'm not a fan of "flexible" solar modules because they really aren't. The cells are silicon crystal which is of course a brittle rigid material.  If you're interested in my other concerns with this type of product I posted on it last year, so I won't repeat those here. 

All I'll suggest here is that if there is any other place where you can mount the module that is on a flat roof surface you'll be better off as that will keep the cells from being under continuous bending stress. Just a friendly suggestion, not trying to start an argument Smile
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Posts: 196 		Direct Link To This Post Posted: 20 Jul 2019 at 8:49am
OG, I hear ya and I agree. But, for aerodynamics and weight reduction I wanted to try one. As for a flat surface, here isn't one except between the a/c and the sidewall which is about 25 inches wide and the panel is 26.5" wide. The roof space on the 176T is very limited, so I'm just going to have to go with what I have.

 Leaving for Manitoba next week and the 'pod will be in a field at a classic rock fest for over a week with no hookups. I just want to keep my 2 6v's topped off and run a 12v fan on me at night. When I get back I will find a spot on the backside of the roof for a smaller panel, maybe a 100 watt. 

Also, my pod lives in an enclosed shed when not on the road, so the panel(s) will not be getting beat up by the weather/sun 365. 
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offgrid View Drop Down
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Posts: 5290 		Direct Link To This Post Posted: 20 Jul 2019 at 9:28am
Roger that. its not like it won't work, its more a matter of longevity. Since you're now planning to use fasteners, you might want to minimize the adhesive to make it easier to replace down the road if need be. 

The 179 has a big space behind the a/c, I plan on using that for a 350-ish watt module. 
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podwerkz View Drop Down
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Posts: 966 		Direct Link To This Post Posted: 20 Jul 2019 at 10:10am
You might want to insert a sheet of coro-plast under the panel. It should help with the heat build-up.

Also, I found that on my r-pod, the trim strips that run from side to side on the ceiling, inside the trailer, are also 'covers' for the open C-channel aluminum frame. Double check yours of course, but that will give you an idea about where you can drill. On mine, there is 12v wiring inside those channels.

By the way, the rock festival sounds cool....gotta link for that?
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Posts: 5290 		Direct Link To This Post Posted: 20 Jul 2019 at 12:32pm
Originally posted by podwerkz

You might want to insert a sheet of coro-plast under the panel. It should help with the heat build-up.


That will help reduce the temperature of the fiberglass roof by adding insulation between the heat source (the sunlight on the solar module) and the roof. Under full sun on a windless day a direct mount solar module can run around 70-80 degrees above ambient temp, that's pretty darn hot.  

But it won't help the module itself run any cooler, the airflow through the tiny little holes in the coro-plast is pretty minimal. Now, if you worked up a way to flow water through the holes in the coro-plast (or used say EPDM rubber solar pool heater tubing under the module) that would cool the module effectively and provide hot water as well. Roughly speaking the 6 gal water tank would pick up about 20-25 degrees an hour under full sun conditions from a 160 watt size module. An RV mounted PV/Thermal solar system, sounds like a fun project LOL
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Posts: 196 		Direct Link To This Post Posted: 20 Jul 2019 at 12:43pm
Podwerkz, here ya go:


Here is the long explanationEmbarrassed:

My wife is from Minnedosa & we have a house there. The first festival there was something like 25 years ago and called RockFest. They had some heavy hitters on stage, Billy Idol, Alice Cooper, Boston, Def Leppard, Jerry Lee Lewis, Pat Benitar, Joan Jet, Sammy Hagar, and many more. The site on Lake Minnedosa grew to a crowd of 20,000 over the years, and things kinda got out of control. Then the management got greedy, bands didn't get paid and the whole thing collapsed. 

Around 10 years ago a committee of volunteers re-organized the defunct festival and named it "Rock In The Fields" and it's all non-profit. It has slowly grown to a crowd of around 5,000 which is as big as they want it to get. My wife and I volunteer at the site along with friends and family. In return we get free entrance passes and a place to camp. I help with the set up and break down of the site, so we arrive almost a week ahead the kick-off. We have three stages up and running each day, so it's never a dull moment. 
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podwerkz View Drop Down
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Posts: 966 		Direct Link To This Post Posted: 20 Jul 2019 at 1:18pm
Originally posted by offgrid

That will help reduce the temperature of the fiberglass roof by adding insulation between the heat source (the sunlight on the solar module) and the roof. 

But it won't help the module itself run any cooler, the airflow through the tiny little holes in the coro-plast is pretty minimal. 

Yes, the main benefit is for reduced heat transmission into the roof. That's the reason for doing it. 

But, expansion and contraction of the panel itself is also mitigated somewhat with the coroplast, and there should be less stress on the adhesives (or fasteners) and the underlying roof structure.

All you have to do it lay a flat palm on a flexible panel in full sun on a hot day...trust me on this...it wont take you very long to pull your hand away!
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podwerkz View Drop Down
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Posts: 966 		Direct Link To This Post Posted: 20 Jul 2019 at 2:43pm
Motor....dang that looks like a really great time up there!

Too bad they didn't have their people contact my people...it's in early August, and in conflict with Sturgis! 


Oh well... maybe next year!

{edit: Woodstock 50 appears to be circling the drain....a lousy lineup of bands, conflicting schedules with Sturgis, and legal and financial issues means it may not happen}

Have you heard of MusicFest at Steamboat Springs, Colorado? The bands aren't posted yet but it always a great lineup of Texas country, rock and roll, etc.


This one is on my bucket list also....but I'm NOT a snow-skier so I will just have to sit in the lodge, drink hot toddies and watch the cute snow bunnies...

Which would not be all bad.

Wink
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Posts: 5290 		Direct Link To This Post Posted: 20 Jul 2019 at 2:52pm
Originally posted by podwerkz


All you have to do it lay a flat palm on a flexible panel in full sun on a hot day...trust me on this...it wont take you very long to pull your hand away!

I did some of my early work on solar module performance in Phoenix, where I regularly saw module temps approaching 100C/212F. At that point not only do you really want to avoid touching them but you'll be significantly degrading the lifetime of the plastics in the solar module and, worse, in your rPod roof. The electrical performance will drop by about 30% as well. 
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