Hanergy/Global solar CIGS

[TwilightZone]

I bought 6, 100w Hanergy powerflex cigs panels to install on my epdm rv roof. They have a 10 year to 90%, 25 year to 80% warranty. But I'm still concerned about directly bonding them down, though thats what they're intended for. Failure, and heat transfer to the living space are my 2 biggest concerns. But unless I can find some "less than permanent " method to attach them, I guess I'll have to just stick them on. There are no grommet holes, or other means of attachment. Opinions are welcome..

Global Solar | Flexible Solar Panels

Global Solar produces light weight, flexible solar panels for residential and commercial structures, and mobile, and recreational uses.

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[TwilightZone]

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[nwredneck253]

i would also be concerned at the heat breaking down your epdm rv roof

 

[TomKady]

Here is one suggestion: all solar panel output degrades in higher temperatures and conducting heat into your EPDM roof is also, uh, not great, so…create an air space between them! ANY AIR SPACE is going to do a lot for you because it cuts way down on heat conduction and instead allows panel heat to re-radiate into the airspace below it, which transfers that heat into air that can remove Btu’s and keep your roof cooler (maybe- that’s a testable theory which will vary with conditions really). Heat is transferred by 1) radiation, 2) convection (i.e. movement of heat/cooling in air; 3) conduction (via contact between materials). On a 75deg F sunny day, the surface of a monocrystalline panel may reach 140-150 deg F (personal observation & measurement). Why? Anti-reflection coating and nature of the materials of construction mainly - in designing solar panels we accept some heat increase in order to trap max useful wavelengths of light and get IR with that decision. If you look at my member image, you’ll see a BIG airspace between my panel layer and waterproof roof layer - for your RV, you can’t go that big because, well driving vs. stationary and I used big ass helical anchors to get min 4 kips uplift resistance per anchor, then weighed it down with a 15’x20’ shed on C12x25x24’ beams, etc. while an RV can get blown over. The physics tell us your panels need 1) a backer sheet to adhere to - I suggest a thin sheet of stainless or anodized aluminum; 2) multiple physical connection points, so that implies a larger area of metal so you can connect along edges outside of panel footprint; 3) air space in between your metal sheet supporting the panel and your EPDM roof; 4) an EPDM compatible stand off (these are really common when I build commercial solar projects - check out OMG as one vendor I know is good; 5) a fairing (or fairings) to avoid a lot of turbulence and uplift when driving (which is basically a sustained 55-75 MPH wind in a generally known direction you can control for, somewhat). The good news is that some thin film panels have tested at lower degradation of V per degree of heat increase and your panels are conformable (“flexible” is really not a good idea for any solar panel, period - conform it and leave it bent the one time). The bad news is that instead of keeping your roof cool, just adhering them to it will make it hotter by collecting more IR and conducting it to your roof. To avoid that, convection is your friend, but getting it is a racking project you probably didn’t count on… .
FWIW, my basis for the above: study of solar since 1988, start up of advanced holographic solar technology company and manufacture of solar panel pilot lines and designs, training from Ph.D optical scientists and assisted them in DARPA project to design “flexible” military use solar panel, patents in solar panel racking, also building science training on heat transfers & 35 years construction experience - not bragging on it, just saying the physics don’t lie - you need an airspace and anything is better than nothing. Hope it helps!

 

[TwilightZone]

Thanks, that's a well thought out reply that I'm sure took a moment of your time. And I agree with it. Here are my problems. These panels require certain specific inverters when bonded to metal. Of course they're not what I have, want, or need. Also, weight is crucial, I'm trying to avoid any bit I can.. My gvwr is too low to add much. That's why I bought the lightweight panels.

 

[TomKady]

I have a solar mounting company because it is a problem I like solving - you’re welcome on the time, no worries at all.
If I were designing for myself and just cheap and functional, maybe this addresses your issues:
1) mount the panels to good quality polycarbonate sheet - not super heavy and not metal, still gets you some real estate beyond the panels themselves for attachment area. Maybe you can get large enough sheets to mount multiple panels one sheet of PC to avoid extra attachment points - 3 panels per sheet? I don’t know the area of the panels vs. available sheet vs. available continuous areas (no penetrations or shading equipment) on your roof.
Noteworthy consideration: Unless the roof area is flat, you need to mount the underlayment (PCarb sheet) and then adhere the panel - gluing them together and then bending creates shear stress in your solar panel worth avoiding.
1) B). There is a version of this used in greenhouses called Polygal, one example: https://www.interstateplastics.com/...&vid=20210701170056-4p&kitoptionpk=7253&qty=1. That material basically has air channels built right into it and downside is it is not dead flat on either surface and only bends in one direction and then, not much; but one option for a pretty direct mount with some air convection under your panel and some ability to bond 100% of solar area to substrate then mechanically attach a removable connection to the substrate which you will be happy for if you have the eventual damage to a panel.
2) In the case you are using a solid sheet of polycarbonate sheet (better for conforming in two directions is one reason to, also dead flat surface to support and adhere your solar panel) A similar polyethylene channeled product is used for sign making and a metal wire holder is stuck into the bottom of the channels to hold up the sign - these are everywhere and easy to just stop and pick up along roadsides - free! Unless it is a contractor sign in front of one house, these have usually been placed illegally, esp if nailed on a utility pole. Collect a stack of these and you have cleaned up some litter! Or you can buy a larger unprinted piece at a sign making shop. Cut into strips and use high quality tape like Gorilla duct tape along the edges parallel to the channels or at least sand off anything sharp along all edges. These are now spacers through and around which some air can flow but in any case, any less area of these separating the polycarbonate from the EPDM and you have reduced conduction a lot and introduced some airspace under your substrate.
3) you have to be savvy about how to attach to or through the EPDM. I’d want to clamp and glue some rigid sections of aluminum along the edges of the poly carb for at least 50% of the total perimeter, glue my spacers to 50% of the area of the back of the polycarbonate sheet and lay on the roof, then attach the aluminum to the EPDM in enough spots to hold it down. I’d add a low profile aluminum fairing on the roof 1.5” away from the edge of the polycarbonate sheet edge to flow air over it when moving, wider than leading edge and probably along the sides as well.
There is a lot to that 1,2,3, but all feasible and as lightweight as it gets, as much airspace as possible, no metal touching the solar panels glued as mfgr instructs and best of all, provides shade to your roof and still removable when a tree branch falls on a panel needing replacement. Sorry we’re (probably) not neighbors and if this isn’t helpful.
Good luck!