Sunpower Flexible Solar panels and roof layout

sprint2freedom

2008 NCV3 170ext
I'm so thankful that it's not the 170EXT. Would have been properly hosed. Wondering if the gaps underneath won't be a plus. I have no intention of putting any weight on it. As long as I get them tight onto the ribs hopefully it will work? I saw someone do that recently. Granted it's on a Transit but same idea: https://www.instagram.com/p/BG7COBSHIYB/?taken-by=gratefulpursuit
As others have mentioned, consider the weight of snow.. around 1.25 to 1.5 lb per inch deposited per square foot of roof area. Four inches of snow on your 46 sqft of panels would thus weigh 230 to 276 lbs.

The Transit appears to have flat roof ribs. The ribs on a Sprinter roof are domed so the contact patch would be smaller and uneven..

An air gap underneath is a plus for shading the van in the summertime, however flexible panels will only have a gap above where there are channels in the roof. Where there is direct contact between the roof and the panels, you'll have thermal bridging that conducts the heat directly into the van. Framed panels will provide better shading.
 
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9th.Life

New member
My approach is 2x 200w SunPower Flex panels fixed on top of polycarbonate roofing sheets, edged to close off the side gaps. Panels will be joined together using the Polycarbonate sheet joiners resulting in a single 400w array joined together. I will then use VHB to marry the panels/poly to the roof ribs. There is a slight overhang (see attached image), here I'll use a spacer (maybe some kind of plastic) to keep it flush with the recess in the roof. The polycarbonate will be positioned horizontally, so that water flows to the sides of the roof down the stock roof edge water canals.

The idea with this approach has 2 major benefits, first, the corrugated polycarb creates a air gap between alum panels and van roof. This will preserve the longevity of the flex panels. Two, this particular polycarb from Suntuf acts as a UV shield, so in the peak of our Australian summers, it should keep the van much cooler! And three (bonus), no unnecessary weight added to the van with rigid panels and alum angles. But really, only time will tell how this goes...

Note: These products are from Bunnings in Australia, but I'm sure you can find them at Home Depot or similar if you're overseas.

Flexible panels: https://www.ebay.com.au/itm/332516663770

Polycarbonate Sheet: https://www.bunnings.com.au/suntuf-sunlite-10mm-x-2-4m-clear-twinwall-polycarbonate-roofing_p1010589

Joiner: https://www.bunnings.com.au/suntuf-3m-x-8mm-solar-grey-sunlite-polycarbonate-joiner_p1010479

End: https://www.bunnings.com.au/suntuf-3-0m-x-8mm-solar-grey-sunlite-end-cap_p1010594

I have a blog that covers all my DIY installs of my 144" Sprinter here:

https://9th.Life
 

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Midwestdrifter

Engineer In Residence
Seems like a good approach. The twinwall/corrugated panels will provide some strength, and still allow for removal, and ease of mounting.
 

HarryN

Well-known member
Nice blog.

Instead of polycarbonate, which is a thermal insulator, consider to use a sheet of aluminum (aluminium).

The Al will help spread the heat, reflect back the sunlight, etc.

Heat is the real killer and you have plenty of it there.
 

arrbee

Member
We just installed genuine Sunpower flex panels on our rack, pretty decent price from Boss Watt.

Former since you get what you pay for (or generally much less) with the Chinese Amazon/eBay versions...latter since this should hopefully provide a more stable frame and some protection (given fairing up front), plus air flow.
 
Just a heads up...flexible solar panels have coatings which will degrade much more rapidly than rigid panels. The degradation modes are twofold : self-degradation (just being outside from UV) & external (impacts, small scratches, dirt,scuffs, etc). The coatings are much softer than rigid modules. This will result in reduced performance and/or cell failure. If you have the option, always go with solid panels and provide adequate airflow. Many flexible modules will experience cupping (individual cells) - mfr does not matter. There are two types of top layers used by flexible solar modules : PET and ETFE. PET has a life of up to 5 yrs (typically 3-5). ETFE is supposedly good for 5yrs + -> however, many within the industry have reported that ETFE has not lasted as long as hoped.
 
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arrbee

Member
Ah well, somebody has to be a guinea pig for failures so the rest can benefit. ;)

Airflow not an issue for us, flex panels are mounted on a roof deck. Reason for going flexi though was thin and light - though yes, this usually equates to more vulnerability.

That said, wouldn't a rigid panel be more itself more susceptible to cracking i.e. hail, truck-propelled gravel, etc?

PS What's cupping?
 

israndy

2007 LTV Serenity
I went with flexible as that allowed the install to happen w/o installation issues. I already had a pipe going thru the roof on the RV that was unused, so I got a combiner box and mounted that over the pipe and then spray glued the panels to the roof. If you are following in my footsteps I did also put a paint protection film down first, so when I do remove the panels I don't take the fiberglass roof with them. The panels are out of the wind and generate enough power to keep the batteries filled almost daily. I don't get the same charge I did in 2012-2013 when I first installed them, and a plastic film did flake off a year or more ago. Panels are not coming apart in any way.

The thing is, they are still going strong. I may not get 30 years out of them, hopefully when they do fail there will be some super cheap or super cool replacement for them. As I was one of the first people to do this I spent over $800 on 300 watts of flex panels, but have more than paid that back in not having the RV plugged in. The convenience of not having to plug and unplug alone was worth the expense, but the batteries have not needed replacing as they are always topped up. I keep the chassis going with a Trik-L-Start sending some of that solar charge to keep the starter battery ready too. Very happy with my setup.

-Randy
 

autostaretx

Erratic Member
PS What's cupping?
Look at a tree's leaf that's fallen and is now drying out...

See the curling? (kind'a like "cupping" your hand)

The dark material of solar cells locally captures and holds heat better than the white spaces between... leading to accelerated "aging" of the encapsulating (top and bottom) plastic.

Rigid panels differ in quality, too ... the best have tempered glass as the top layer, others have plastic. Each have differing resistance (or consequences) to UV, abrasion (sand blasted as you're driving) and impacts. Plastic can dent where tempered glass may shatter (but it takes a lot to do that).

--dick
 

Cattmando

New member
I've already got my flexible panels and looking at attachment option on my Freightliner Sprinter. The aluminum panels make sense. More expense. :(
 

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