With Flex panels, yes there is some output drop but not as much as you would expect, not like half. You have to way the options of some loss in performance versus aesthetics and slightly less power lost. In 160F on an Airstream I've seen about a 20-25% power loss with the flex modules. So if you live in area or RV typically in an Area where it can get say 90-100 degree's at some point during the day this is probably going to happen. So if you know that you can always say 2 x 100's watt flex modules up there to make up for your losses. Alternatively you go with rigid panels, which on an Airstream definitely are not as aesthetically pleasing. Yet these too will have some power loss, because unless it's windy and the air is moving it doesn't matter what's up there its going to heat up.
Thanks for the input!
Having spent time on my roof with a measuring tape I know what could fit where.
Living in CA the heating issue is a concern. I am planning to paint my roof panel white to help control interior temps.
The way I am leaning at the moment is toward flexible 100w panels in 3's, with one straddling the Centerline and one each side. These will be mounted on aluminum frames and curved to match the roof. The outer 2 will have tilt mounts. I was thinking that this would help the panel furthest from the sun to avoid shading and increase "gain" and aid cooling a little.
Seriously thinking about incorporating some solar water heating into the frame of the center mounted panel too if it could work.
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My name is Steve.... and I am an Alumaholic!
Working in my Garage is like playing TETRIS with Tools!
If you are going to frame the flexible panels why not use rigid panels to begin with?
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MICHAEL
Do you know what a learning experience is? A learning experience is one of those things that says "You know that thing that you just did? Don't do that."
If you are going to frame the flexible panels why not use rigid panels to begin with?
The #1 is aesthetics... but it gets deeper than that.
SOB with flat panels on the roof is fine... but on the curved roof of our Airstream they will be pretty visible... and lets face it, the #1 reason we bought an AS is the way it looks!
Another point is one of durability... mounted to the roof, you can walk on them in theory, but I have a concern about rivets being behind a panel!
I am leaning toward frame mounting as I want to be able to tilt the outer ones to minimize shading and maximize output, and the frame will only be maybe 1/2 thick, so visually it would look better.
Mounted on my frame idea I might be able to, but if not I can tilt them up out of the way for roof or panel maintenance
I understand and respect Lewster's comments about the downsides of flexible panels... but for now I am prepared to accept the shortcomings in trade for the advantages.
My calculations based on panel size and available space says in theory I have space for 12x 100w panels and 3x 50w panels without encroaching on the end wraps. I would have to move the TV antenna for that. The reality is that I would probably never go that far, and 600w is where I will stop.
Just another thing to point out is that because of the extreme heat some of you experience...I'm in the North West so we don't get that hot, and at least not for very long, but you should leave I'd say about 1/4 of an inch in between the panels from each other as they can expand and contract with the heat. If they are butted up next to each other the center panel might bubble up when they expand.
2014 25' FB International
2007 20' Safari SE
2005 19' Safari
Qualicum Beach
, British Columbia
Join Date: Sep 2004
Posts: 1,096
Renogy recommends at least a half inch air gap for best performance. Going to work on doing that as soon as we can find a home to work out of. Right now the 3 100w Renogy panels are doing just fine flat on the canopy roof but I think they will improve with some air space.
2015 27' FB International
nanoose bay
, British Columbia
Join Date: Jun 2015
Posts: 11
Quote:
Originally Posted by lewster
Flex solar panels, while a great idea, are not quite ready for prime time. We have been testing some from various makers, and have found several problems:
• the panels get extremely hot as they are bonded to the roof and have no way for cooling air to flow under the panels
• due to the extreme surface heat, the panels tend to cup in a concave fashion ever so slightly, capturing morning dew and the associated dirt....they are extremely hard to clean when this happens.
• the biggest problem, which is also heat related, is panel over heating. As solar cells heat, they loose efficiency. With no way to cool down, they can reach surface temperatures of up to 160ºF, which can reduce the output by as much as 50%, making your 100 watt, $600 flex panel essentially a 50 watt, $600 flex panel. That 1000 watt output specification was measured at 'standard test conditions, or STC, which is a lab figure calculated at 77ºF and assuming 1000 watts/sq. meter. Not a real world measurement!
•*as stated above, real cost per watt output is still several multiples of flat mono crystalline panels.
As I said, when the construction and cooling problems are mitigated, they will be a great panel........JUST NOT YET!
Hi, can you recomend a panel sytem for our 27' FB international ? its a new 2015 and is pre-wired for solar i am told. Thanks, Murray
Please send an e-mail to : lew@gorge.net for any further specifics.
Thanks!
Lew Farber
RVIA/RVDA Nationally Certified Master Tech
Master Tech Energy Systems, Inc.
AM Solar Certified Installation Center
Lifeline Batteries**Magnum Inverters
541-490-6357
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lewster
Solar Tech Energy Systems, Inc.
Victron Solar Components and Inverters, Zamp Solar Panels, LiFeBlue and Battle Born Lithium Batteries, Lifeline AGM Batteries
Has anyone else noticed that Grape Solar has discontinued their 100w 5mm thick flexible panel? This is the panel that AM Solar was selling, I think. I've noticed many 100w flexible panels are not for sale anymore, unavailable or discontinued. What's going on? Anyone have the inside track?
I also noticed AM Solar has put several traditional panels on inventory clearance. Are we due for a new/better panel soon?
Has anyone else noticed that Grape Solar has discontinued their 100w 5mm thick flexible panel? This is the panel that AM Solar was selling, I think. I've noticed many 100w flexible panels are not for sale anymore, unavailable or discontinued. What's going on? Anyone have the inside track?
I also noticed AM Solar has put several traditional panels on inventory clearance. Are we due for a new/better panel soon?
Regardless of what some specific representatives of certain solar companies say, there have been many problems with flex panels. The excessive heat of direct mounting is one. Their significant reduction of peer at low light/azimuth conditions is another. Surface scratching and durability are another. Significant reduction in total wattage output well below the STC ratings and also well below regular hard panels yet another. Renogy had a big recall of their flex panels and Grape Solar refunded many of the panels they sold!
How do I know???????????? DIRECT EXPERIENCE (and some inside trade information)!!!!!
As I have stated in other threads (maybe even this one!!). I replaced 5 AM Solar GS-100 panels on the roof of my service van last year with 5 of Grape Solar's 100 watt Photo Flex panels early last Fall. Since the Sprinter has raised ribs on the roof, the flex panels were bonded to the top of the ribs with SikaFlex 221. This provided about 5/8" of free space below each panel for ventilation while the van was in motion.
After a week, the panels started to seriously sag into the valleys of the van and had to be removed as then no longer were flat and were collecting rain and dew, leaving a dirty residue when the moist evaporated which cause a further decrease in overall panel output and efficiency.
My solution to the sag was to mount 3 pieces of .080 aluminum sheet to the top of the ribs cut to the exact size of the 5 panel array, then bond the flex panels to the aluminum. This allowed the panels to take the flat shape of the aluminum and still had the cooling space below.
After all of these steps for proper installation, the flex panels were simply NOT UP TO PAR compared with the output of the GS-100 panels of the same rating and physical size.
After a year's use with the same charging hardware (Blue Sky 3024iL controller and iPN-PRO remote) charging a 200 amp/hour lithium pack, I experienced SIGNIFICANT REDUCTIONS in charging amperage to the batteries and increased length of time to recharge. With the GS-100 panels, I would see up to 35 amps into the batteries on a clear, sunny day at peak sun in summer. The Photo Flex panels have never given me over 22 amps in the same situations.
In addition, I regularly saw 18-19 VDC coming from the GS-100 solar array and never over 14.5VDC from the flex panels, as shown by the iPN-PRO remote. YMMV, but the flex panels are being removed at my next opportunity for 5 new GS-100 panels.
Anyone want a great deal on 5 mildly used Grape Solar Photo Flex panels???????????????????
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lewster
Solar Tech Energy Systems, Inc.
Victron Solar Components and Inverters, Zamp Solar Panels, LiFeBlue and Battle Born Lithium Batteries, Lifeline AGM Batteries
Since we are discussing flex panels, I recently had the opportunity to do a 400 watt solar upgrade, 300 amp/hour lithium battery and Magnum MS-2012 inverter/charger upgrade to a new Interstate Grand Tour. This rig had Airstream's new '100 watt solar panel upgrade'.
It should be obvious from the photos that due to the sloppy installation, the fact that there is a huge valley in the middle of the panel (similar to what I initially experienced on my own Sprinter), the fact that one corner is actually SHADED from the TV antenna and that sealant is overlapping sections of the outer cell borders, that Airstream would have been better off leaving the 50 watt glass panel on the Interstates, as they probably had more usable output than this panel with it's 'interesting' installation characteristics!!!
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lewster
Solar Tech Energy Systems, Inc.
Victron Solar Components and Inverters, Zamp Solar Panels, LiFeBlue and Battle Born Lithium Batteries, Lifeline AGM Batteries
It takes some planning, but one can get a lot of 100 watt non-flexible panels on an Airstream roof despite the vents, skylights and air conditioners.
We have five on the roof of a 2015 23D and eight on the roof of our 2014 31' Classic. Since we have replaced the original WineGard crackup batwing antenna with a WineGard Razar on the Classic, we could probably fit two more 100 watt panels on the roof of the Classic. We did replace the stock plumbing vent covers with low profile versions that are under a panel.
We replaced the Fantastic fans with Maxxfan 7000K units on the 23D so when they are closed, the top of the lid is about even with the top of the panel and casts no shadows. We will be replacing the Fantastic fan and shroud on the Classic for the same reason and ease and flexibility of operation.
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TV - 2012 Dodge 2500 4x4 Cummins HO, automatic, Centramatics, Kelderman level ride airbag suspension, bed shell
Looks like a nice install, congratulations.
The older airstreams seem to have more curve in the roof, which means more visibility and mounting issues.
I read Lewster's post on the warping issues, and having handled these flexible panels, I am not surprised they warped!
They should be mounted better than that.
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My name is Steve.... and I am an Alumaholic!
Working in my Garage is like playing TETRIS with Tools!
I was over working on my rig yesterday, and decided to put my 30w unit up on the roof to boost my battery while I worked.
Before I connected it to my battery(directly with no charge controller), I checked its output... It was reading 21v.. Is that normal/OK?
__________________
My name is Steve.... and I am an Alumaholic!
Working in my Garage is like playing TETRIS with Tools!
That's a pretty common Open Circuit voltage but it really does need a charge controller between it and the battery unless you are gonna sit and stare at the voltage, disconnecting it when it passes 14 volts. (I've done that when I was in a pinch)
Not sure if there is a thread for this already.
Last year, we installed the Renogy 100 Watts 12 Volts Lightweight Monocrystalline Solar Panels and now they have been recalled.
Anyone else have these solar panels?
What would you recommend replacing them with that is still a flexible panel?
(Yes, we like them. They worked great for us. We just have two). Thanks.
Flexible solar panels have been characterized in this discussion thread as losing efficiency over time due to heat build-up caused by being mounted directly on surfaces (in this instance trailer roofs) without airspace behind to allow air circulation/convection to cool the panels. This is the first time I have read of actual fire risk, but fires may have occurred when they are mounted on a readily combustible surface such as wood.
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Marty Womer
Old Orchard Beach, Maine
Trailer name: Quarantina
2019-2022 President, Northeast Mountaineers Airstream Club
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