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Old 05-14-2021, 04:13 PM   #1
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Flexible vs. Rigid Solar Panels

Hello all!

We're evaluating our solar panel options, and I'm intrigued by the flexible Allpowers 100W monocrystalline panels. (5.56A, 18V) They only weigh 7lbs!
They're about $190 each (41" x 21"), but my thought would be that they could be rounded on the roof so that we could get sun sooner, and later, and have less weight on the bus.

BUT, do you think we'd actually be losing out on prime mid-day/overhead sun to charge the solar by having a few of the cells anchored to the edge area of the bus roof? (I don't think so, but would rather ask than assume!)

Our plan would be to drill the flexible panels into the roof with nylon washers, and be done. If we go with rigid panels, we'll have to add framing for a platform, which would be more weight for framing and for rigid panels.

It doesn't seem like many use the flexible panels. Is this because they're new-ish or more expensive?

Thank you!

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Old 05-14-2021, 04:52 PM   #2
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More expensive, almost double. They are less durable to tree and branch damage. Otherwise they are as efficient as hrd panels. Some have raised dots on the surface to promote gathering of light.
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Old 05-14-2021, 05:07 PM   #3
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Flexible panels also have a reputation for not lasting as long, although this applies to any panel that doesn't stay cool enough.

Will Prowse just did a video this week on 250W panels he found for $50 / pop, there are lots of after market/second market panels out there for very cheap that perform well.
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Old 05-14-2021, 05:24 PM   #4
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Yes.

They last only a few years at best. Also output is typically not quite as good.

Go for rigid ones, its worth it.

The SanTan solar used polycrystalline ones are stupid cheap. I just bought another batch.
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Old 05-14-2021, 07:26 PM   #5
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The flex ones do not last, even if properly installed, with no flexing
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Old 05-14-2021, 11:38 PM   #6
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I am using the flexible panels on my Crown. I am layering some 5mm foam insulation between the panels and the roof of the bus. They are being mounted lengthwise on the centerline of the bus. Each panel costs me $150 and they are rated for 200 watts. I believe the insulation will prolong the life of the panels as they will not absorb as much heat from the bus. I have a number of rigid solar panels I acquired from a couple local solar plant project that were to be taken to the landfill as the glass was broken on them. They will still work with broken glass. I have a 300 watt panel that has broken glass that I have been using for 5 - 6 years to keep my tractor batteries charged (I switch between tractors periodically) and It still works. I would think a branch falling on a rigid glass panel will break the glass (if the branch is of large size) When I lived in the Santa Cruz mountains I had a number of large branches break off of the redwood trees surrounding my house. At least one put a good dent in our pickup truck's fender. Something I learned about the solar plant reject panels was the actual cells themselves were flexible. (I attempted to remove the pieces of glass from one of the most damaged panels).


I have previously owned solar cells that thin fragile silicone (broke easily). I think the newer ones are made differently.



I researched the panels I got from the latest solar plant project and found that they were available for about $200 and are rated for 400 watts (1 x 2 meters in size), so yes my flex panels are more expensive than the rigid panels.



The curvature of a Crown bus roof isn't very much in the middle (along centerline), so I don't see much loss of efficiency from that. Flat panels need to be sun pointing or tracking for maximum efficiency and I would classify that capability as a lot to implement for a parked bus, and not possible for one going down a road.


One last thought:


I am mounting my panels using Rivnuts. I will also calk the mounting points where the bolts penetrate the roof. I am using sealed boxes with gland nuts for the wires passing through the roof. I am using stainless steel Rivnuts and stainless steel bolts.


I know I rambled on a little but these are some of my thoughts.
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Old 05-15-2021, 04:33 AM   #7
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My company started installing these solar panels on the new trucks a few years ago. They are flexible enough to match the aerodynamic curve of the sleeper and so far they seem durable enough to last 500-600k miles which is about 5 years for a commercial truck. We're not trying to make the truck electrically self-sufficient but it does keep the batteries topped up so that on sunny days the truck doesn't have to idle to keep the bunk AC running. Probably less risk of tree limb damage in our situation but aside from that they seem durable enough simply affixed with adhesive backing and taped along the perimeter. If I get a chance I'll try to get a close up picture of the installation. This attached picture shows the new truck on the right and that black area on the roof is mostly solar panel.
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Old 05-17-2021, 11:36 PM   #8
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Thank you!

Thanks, everyone! You gave us some great things to consider! As always, we have more homework to do. I appreciate you taking the time to share with us your perspective!
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