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Old 08-17-2011, 11:38 AM   #15
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I haven't really noticed that the panel output starts to degrade till quite a bit hotter, in my off the grid home with better monitoring, up to about 105 F outside temp, the panels will still output at full voltage.

On the other hand, Jan and Feb are even more fun to watch them put out amazing amounts of power on a bluebird day when it is below freezing. I have seen my 2.2Kw array put out almost 4Kw and well over 60A at times.

This is just from watching the numbers in a day to day off the grid solar only home. I am also seeing similar but smaller numbers on the trailer.
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Old 08-17-2011, 12:10 PM   #16
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I have noticed that the older panels put out a lot more than rated. Some of the newer china panels output are overrated
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Old 08-17-2011, 12:40 PM   #17
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I don't think it is age, I would stay away from "most" of the China panels. I tend to buy Evergreen made in the US. If you know of a China made panel that is great quality I would like to hear about it.
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Old 08-17-2011, 01:16 PM   #18
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No china that I know of. I'm always willing to pay the premium for USA / German / etc... quality.
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Old 08-17-2011, 02:09 PM   #19
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Looks like evergreen is moving to China
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Old 08-17-2011, 03:07 PM   #20
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Depending on the panel types the voltage itself may not lower much but the total power output HAS to drop with heating - What type panels are you using?

I should've specified panel types - thin-film PV panels losses with heating are quite a bit less (-0.2%/C), its physics of the expansion of the mono/poly crystaline silicon with heat that makes the exchange of electrons less easy so output drops. Solar water heaters can and do make steam (sometimes too easily) so its not a great stretch that the PV wafers in the panels itself can reach 100C.

Count any sun at 100%: Panel sees 8-14% escaping in reflection or from glass surfaces (both inner & outer) and reflected away from wafer surface, then subtract energy converted to electricity 12-18% so already the 1000w per square meter sunlight means 68 to 80 percent of sunlight converted to heat - 680 to 800 watts heat having to be dissipated. (hot?)

Heat is exchanged three ways - convection, conduction and radiation.

The smooth outer surface of a PV panel is not a lot of area to bleed off heat into air, if the panels are getting a breeze that is a plus.

The glass and plastic of the PV panels actually are on the insulation side of the heat Conduction equation, some heat is carried away into the supporting frame work but very little.

So Radiation is where most of the PV waste heat is dumped - panels up away from any reflector that could bounce the Infrared back at the panel, and also not 'shining' on another panel to add to its heat load is best-effort design. That is the bad thing about panels on a travel trailer, to keep them aerodynamic and strong you're loosing by having the RV shell bounce the heat right back at the panels.

Something else is the rated power output, some OEM's are +/-5%, +10/-5% etc. so straight out of the box you could be dropping watts, but then normal aging also drops wattage so if the OEM ships low* output panels the likelihood of them having a warranty issue on them is higher. I believe Evergreen is minus zero tolerance on new panel output but that is likely advertising spin since their panels may suffer a little faster output loss over time versus other silicon foundry methods so its really just covering their own bases... BUT their 10-year limited warranty on materials is kind of rare in the Industry.

I have a mix of panels - some Sharps, Photowatts, Schott Solar and some Sun Electric 'house' brand. Most are ancient but the Sun Electrics are newer surplus German wafers with 21-23% conversion efficiency cells that are usually only sold 'in-house' by a packaged system installer (dark, almost black square cells w/ beveled corners and no front mounted conductor traces). If I had to start fresh I think the wafer efficiency and cheap price would win any argument which cells to buy as long as the panels did NOT have to be UL listed. I think they still have them and will mention German made cells but its been a while since I've followed them...
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Old 08-18-2011, 09:16 PM   #21
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Ok well a little design time now that the shell is back on the frame and the wind wont carry it away....

I am planning on using two of the IronRidge XRS rails per row with custom aluminum cross bars to limit the flex in the array.

There will be a street side row and a curb side row running the full length of the shell.

Rather than use the "L" mounting feet I am going to use an L extrusion mounted the length of the shell and then bolted into the XRS rail at multiple locations. This will dissipate any point load on the shell.

http://www.civicsolar.com/sites/defa...ail_System.pdf

I have used the heavy aluminum piano hinge before in creating tilt systems and this may be an option as well for a tilt on site system
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Old 08-19-2011, 03:52 AM   #22
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I think I like the idea of flush mounting the extrusion rail. I'm assuming there aren't any issues of catching debris or trapping water.
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Old 08-19-2011, 07:57 AM   #23
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Quote:
Originally Posted by UAPachyderm
I think I like the idea of flush mounting the extrusion rail. I'm assuming there aren't any issues of catching debris or trapping water.
My biggest concern is not trapping any air.
I will have a lot of variable surface area moving down the road at 60mph. Don't want to turn it into a wing.
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Old 08-19-2011, 09:00 PM   #24
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Quote:
Originally Posted by Darkspeed

My biggest concern is not trapping any air.
I will have a lot of variable surface area moving down the road at 60mph. Don't want to turn it into a wing.
Lewster installed a spoiler/air dam on the front edge of his ... but a fly behind Airstream might save you on tires. 
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Old 08-19-2011, 10:00 PM   #25
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Originally Posted by UAPachyderm View Post
Lewster installed a spoiler/air dam on the front edge of his ... but a fly behind Airstream might save you on tires. 
Braking, however, could get REALLY exciting!
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Old 08-19-2011, 11:00 PM   #26
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I flat mounted mine with AL angle. Losing a 40 lb panel or four @70 really seems like a bad idea.
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Old 08-19-2011, 11:41 PM   #27
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Moving down the highway straight line shouldn't be a problem - crosswinds and turbulence from semi-rigs & underpasses might give all the stops a good rattle though.

On a continuous rail like the IronRidge XRS I think a larger footprint bracket or reinforcing plate matching the shell rib would provide equal or better bracing and allow water to drain... and maybe a little Stuka dive bomber sound effect in a strong cross wind

Wondering about the piano hinge - will they exist on both sides or wobble adjust from the center or such?

For a small maintainer panel I'd love to pirate the television antenna pivot mechanism idea to put a radome (radar dome) type azimuth and elevation adjuster for a single 40 or 50 watt panel.... manual, not tracking (yet)
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