Solar related Q: flex power mat? - Page 2 - Fiberglass RV


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Old 03-20-2011, 02:10 PM   #15
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These new thin-film products are interesting, but (as already pointed out), their energy density per square foot is much lower than either a mono- or polycrystalline construction panel. I do solar panel demonstrations from time to time; in one of them I display a 45-watt amorphous panel setup side-by-side with a 40-watt polycrystalline set. Not only is the polycrystalline panel set less than half the size, it puts out more power than the amorphous panels because amorphous panel output rapidly degrades once you put them out in the sun*. (More on degradation below.)

That's a real pity because, unlike crystalline panels that loose power after they hit 40C (108F), amorphous panel power production doesn't drop off until they reach 60C (140F). Crystalline panels try to get around this limit by having an air gap beneath them, which allows air to circulate and cool the panel. Even so, a crystalline panel that's collecting sunlight on a hot Arizona summer day will not put out as much energy as the same, exact panel on a sunny, temperate day on a California beach.

As for sticking an amorphous panel directly to your egg's roof, I'm not sure that's a good idea. Dark, solar-energy-absorbing panels have an air gap beneath them, which not only helps keep them cool, it also prevents the transfer of the sun's heat directly into your trailer. So, while I'm really looking forward to the next generation of self-stick amorphous solar panels for residential rooftops, I'd steer clear of those same panels when it comes to the roof of my egg.

* Late last year a German researcher found a way to prevent amorphous panel output degradation, which should male amorphous panels more competitive.
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Old 03-20-2011, 04:07 PM   #16
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I display a 45-watt amorphous panel setup side-by-side with a 40-watt polycrystalline set. Not only is the polycrystalline panel set less than half the size, it puts out more power than the amorphous panels because amorphous panel output rapidly degrades once you put them out in the sun*.
I read that the amorphous panels loose about 20% of their capability in the first few months of use. Because of that, the panel power output is rated 20% lower than actual output when new. In other words an amorphous panel rated at 40 watts will really put out 48 watts when new so that after the initial degradation the panel will actually put out 40 watts. The amorphous panel will then degrade about 1% per year after that, while the polycrystalline panel does not degrade each year.

Peter since you have both types of panels you may be able to tell us about real world operation. The ratings on the panels are for full sun at optimum angles, but in the real world there are often overcast days and full or part shade. The polycrystalline panels have their crystals in series so shade blocking even part of a panel can cut the power output almost completely. If you were so inclined, it would be great to see the the power output of your 2 panel types side by side in full sun, part sun, full shade, less than optimum angles, and with overcast conditions.
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Old 03-21-2011, 08:56 PM   #17
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* Late last year a German researcher found a way to prevent amorphous panel output degradation, which should male amorphous panels more competitive.
Peter,
If you remember where you found that article, I'd love to see a link. Amorophous panels are a hot topic here in Florida green building, with the new "within the standing seam" design. I'm (obviously) not sold on them, but I missed this article in my research.

Thanks.
Sherry
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Old 03-22-2011, 02:56 PM   #18
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Peter,
If you remember where you found that article, I'd love to see a link. Amorophous panels are a hot topic here in Florida green building, with the new "within the standing seam" design. I'm (obviously) not sold on them, but I missed this article in my research.

Thanks.
Sherry
Delft University of Technology (2010, July 8). Energy yield of cheap solar panels raised from 7 to 9 percent. ScienceDaily.

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Old 03-22-2011, 03:01 PM   #19
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Peter,
If you remember where you found that ...
Not on the same subject, but very much of interest for stationary solar:
Aalto University (2010, November 9). Easy fabrication of non-reflecting and self-cleaning silicon and plastic surfaces. ScienceDaily.
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Old 03-22-2011, 09:35 PM   #20
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Thanks, Peter
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Old 04-25-2011, 02:10 PM   #21
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>As for sticking an amorphous panel directly to your egg's roof, I'm not >sure that's a good idea.

This data pertains to Flex Energy's PVL solar mats (manufactured by Uni-Sol). The normal operating cell temperature of this thin-film product is 50C to 70C (with no back ventilation) and the maximum Recommended Roof Temperature is 85C (185F). Putting them on an RV roof should not pose any problem at all. I have two such mats on my Class C.

>The polycrystalline panel set less than half the size, it puts out more >power than the amorphous panels because amorphous panel output >rapidly degrades once you put them out in the sun*.

I'm certainly no expert, but research indicates that the reverse is true. Polycrystalline products become less efficient (as much as 20% less efficient than a PVL mat at normal operating temperature) as the temperature rises whereas PVL products do not. Indeed, in daily use the PVL mats will generate power for longer than a crystaline panel because they have an exceptional tolerance for low light levels and shade - so they will keep generating long after crystalline panels have stopped. According to Mount Union College in Ohio the mats remain 80% efficient even under two inches of snow. So there are cases where you might have a higher rated crystalline panel that actually generates less power than a lower rated PVL mat on a daily basis given a broad range of weather conditions - like those that we experience in the real world

There's simply too many benefits from a PVL product to ignore, especially if you're RVing or Overlanding.

Julian
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Old 04-25-2011, 07:28 PM   #22
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All true, but I think you're missing what I was saying. I think one of the liabilities of surface-mounting an adhesive-backed solar panel directly to a fiberglass trailer's shell is not that the solar panel's efficiency suffers as it heats up, but that the trailer's occupants suffer as the panel absorbs the Sun's heat energy and transmits it into the trailer. An amorphous solar panel may work really well at 185F, but I get distinctly grumpy at temperatures over 100F.

Ditto panel size. After their first few hours exposure to sunlight (Google up Staebler-Wronski effect and look here to see why this may become less of a factor in the future), amorphous panels have been 7-8% efficient at converting solar energy into electrical in direct sun; crystalline panels are 16-21% efficient, so you need less than half the panel size to obtain the same generating capacity.

It all adds up, in my mind, to thinking that amorphous panel installations may wind up being the better application for large, fixed roofing structures that don't interface directly into living spaces, but not the best choice for the tiny roof of our trailers that are right on top of us, or for portable solar panel arrays that we move to a sunny spot when we set our trailers up.

YMMV

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Originally Posted by jlgothard View Post
>As for sticking an amorphous panel directly to your egg's roof, I'm not >sure that's a good idea.

This data pertains to Flex Energy's PVL solar mats (manufactured by Uni-Sol). The normal operating cell temperature of this thin-film product is 50C to 70C (with no back ventilation) and the maximum Recommended Roof Temperature is 85C (185F). Putting them on an RV roof should not pose any problem at all. I have two such mats on my Class C.

>The polycrystalline panel set less than half the size, it puts out more >power than the amorphous panels because amorphous panel output >rapidly degrades once you put them out in the sun*.

I'm certainly no expert, but research indicates that the reverse is true. Polycrystalline products become less efficient (as much as 20% less efficient than a PVL mat at normal operating temperature) as the temperature rises whereas PVL products do not. Indeed, in daily use the PVL mats will generate power for longer than a crystaline panel because they have an exceptional tolerance for low light levels and shade - so they will keep generating long after crystalline panels have stopped. According to Mount Union College in Ohio the mats remain 80% efficient even under two inches of snow. So there are cases where you might have a higher rated crystalline panel that actually generates less power than a lower rated PVL mat on a daily basis given a broad range of weather conditions - like those that we experience in the real world

There's simply too many benefits from a PVL product to ignore, especially if you're RVing or Overlanding.

Julian
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Old 04-25-2011, 08:02 PM   #23
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amorphous panels have been 7-8% efficient at converting solar energy into electrical in direct sun; crystalline panels are 16-21% efficient, so you need less than half the panel size to obtain the same generating capacity.
YMMV
I think we all agree that under ideal conditions the crystalline panels are significantly more efficient. While both panel types with the same rating will put out the same amount of power under those ideal conditions, the amorphous panels have advantages in hot weather, in cloudy weather, in both part and full shade, earlier and later in the day and at less than optimum angles. They will put out usable power under many conditions when the the crystalline panel will not produce. The total amount of power produced in a day from both panel types with the same rating may not be the same. The amorphous panel daily output may be larger in the real world and that is really all that matters, not just peak output. I would not enjoy setting panels up each time I camp and then adjusting the angle for optimum several times during the day.
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Old 04-25-2011, 08:22 PM   #24
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I think we all agree that under ideal conditions the crystalline panels are significantly more efficient. While both panel types with the same rating will put out the same amount of power under those ideal conditions, the amorphous panels have advantages in hot weather, in cloudy weather, in both part and full shade, earlier and later in the day and at less than optimum angles. They will put out usable power under many conditions when the the crystalline panel will not produce. The total amount of power produced in a day from both panel types with the same rating may not be the same. The amorphous panel daily output may be larger in the real world and that is really all that matters, not just peak output. I would not enjoy setting panels up each time I camp and then adjusting the angle for optimum several times during the day.
Ditto for me, which is why I chose two Flex Energy Power Mats. Though, in fairness to Peter, I'm in a Class C motorhome and have enough creature comforts (2 AC units amongst them) to ensure that I don't bake in the RV The mats are to help with dry camping as I've plenty of experience with my batteries running flat (both house and engine) when I was out in the bundu! A colleague has just put 10 solar mats on his fifth wheel and will be sending me the data from his shakedown trip. His mats will be able to provide 680 Watts and are coupled to a bank of ten 110amp 6Volt batteries and a 3000W inverter. Nothing quite like being prepared!

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Old 04-27-2011, 04:30 PM   #25
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As far as the solar panel adding heat to the trailer, that is a function of the flex mat format rather than a difference between amorphous and crystalline materials. Amorphous panels are available as a flex mat and also as a rigid panel with a metal frame that can be mounted the same way as the crystalline panels. If heat gain with a flex mat is a concern, the flex mat could be mounted on some flexible foam and then the foam glued on the trailer roof.

Big rectangular frames mounted a few inches off the roof really kill the aerodynamics of the smooth rounded egg shaped trailers.
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Old 04-27-2011, 04:54 PM   #26
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Big rectangular frames mounted a few inches off the roof really kill the aerodynamics of the smooth rounded egg shaped trailers.
That was another deciding factor. I get a lot of in transit vibration in my RV - in spite of rear air bags - so frame mounting anything on the roof is doomed from the outset - and would probably cause long term damage to the roof. The mats are able to tolerate this vibration much better than panels. Although my RV wasn't exactly aerodynamic to start with the mats will have a negligible wind drag impact. The only raised element of the install is the ABS wire connection box which sits a couple of inches above each mat.

On a slightly related tangent can anyone recommend a good brand of (warm) LED bulb. I'll be switching out all the bulbs in the RV to reduce the load when dry camping. I'd like to try a couple of different brands for review purposes.

Julian
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Old 04-28-2011, 04:56 PM   #27
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That was another deciding factor. I get a lot of in transit vibration in my RV - in spite of rear air bags - so frame mounting anything on the roof is doomed from the outset - and would probably cause long term damage to the roof. The mats are able to tolerate this vibration much better than panels. Although my RV wasn't exactly aerodynamic to start with the mats will have a negligible wind drag impact. The only raised element of the install is the ABS wire connection box which sits a couple of inches above each mat.

On a slightly related tangent can anyone recommend a good brand of (warm) LED bulb. I'll be switching out all the bulbs in the RV to reduce the load when dry camping. I'd like to try a couple of different brands for review purposes.

Julian
superbrightleds- warm light- you can not tell the difference
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Old 04-28-2011, 05:30 PM   #28
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superbrightleds- warm light- you can not tell the difference
Many Thanks,

Julian
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