Author Topic: Panel ventilation  (Read 17308 times)

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guruji

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Panel ventilation
« on: August 18, 2010, 06:39:56 AM »
In a solar panel is it good to do ventilation to lower temperature a bit?
Thanks

Ungrounded Lightning Rod

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Re: Panel ventilation
« Reply #1 on: August 18, 2010, 10:08:40 AM »
In a solar panel is it good to do ventilation to lower temperature a bit?
Thanks

Yes.  If practical (i.e. not a floppy panel and you can build a support structure), mount it so air can circulate behind it, not just in front of it.  That lets it lose heat from both sides.

If it's not mounted facing straight up you'll get convection helping the circulation.  (Even if it's flat to a horizontal roof, a little space lets wind blow heat out from behind it.)  If you're mounting it over a roof you just need a couple inches clearance and the passage will act as a chimney.  If you're mounting it near a roof but hinged for optimum angle, mount the hinge a bit over the roof rather than right against it so air can come in under the hinge.

Most of the light the panel absorbs turns to heat in the panel so you have plenty of heat to drive convection.  When the panel gets hot its voltage drops and the resistance of its internal conductors rises, so keeping it cool is good for power generation as well as reducing deterioration.
« Last Edit: August 18, 2010, 10:11:27 AM by Ungrounded Lightning Rod »

DanG

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Re: Panel ventilation
« Reply #2 on: August 18, 2010, 11:08:53 AM »
But ventilation of the PV wafer section themselves is an absolute no - when doing homebuilt some have done pinhole vents to try to minimize or eliminate condensation forming behind glass  panels they built with an airspace but that is seen as the lessor of two evils - liquid water in the panel vs. air, fresh moisture from humidity and dirt damage over time...

guruji

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Re: Panel ventilation
« Reply #3 on: August 18, 2010, 01:25:55 PM »
DanG so in my panel you're saying no?! cause mine is built with solarcells and I did not do any holes in it but the stun connections are melting everytime with this hot summer.
Any help please?

Ungrounded Lightning Rod

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Re: Panel ventilation
« Reply #4 on: August 18, 2010, 03:53:34 PM »
But ventilation of the PV wafer section themselves is an absolute no

Yikes!  Thanks, Dan.  I didn't realize he might be talking about venting the cells themselves.  B-b

BrianSmith

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Re: Panel ventilation
« Reply #5 on: August 18, 2010, 06:05:57 PM »
I think in a standard solar panel, they thermally bond the cells to a back plate that helps keep the cells cooler.  You might be able to use a higher temperature solder as an option as well. I am assuming you are talking about the solar cell bond wires that are series connected together between the cells that are coming unsoldered?

guruji

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Re: Panel ventilation
« Reply #6 on: August 19, 2010, 05:25:41 AM »
Hi Brian yes I'm talking about the soldering between cells cause I'm losing my panel everytime because of high temperature. High temperature soldering I never heard about this. This is a special stun for soldering?
Thanks.

Clifford

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Re: Panel ventilation
« Reply #7 on: October 01, 2010, 04:22:07 AM »
There are many different types of solder with different melting points.  Typical 60/40 solder has a MP around 370 F or 188 C.  That sounds hot...  but I guess that would melt in a typical cookstove.

Wikipedia has a list of typical solder alloys & MP.

http://en.wikipedia.org/wiki/Solder

I assume electrical conductivity on the backing plate is a bit of a problem, but is there a way to bond the cells to an insulator, then to an aluminum plate?  Adding fins would be a bit excessive, but perhaps you could increase the surface area by adding a second aluminum backing plate with half punched up fins...

Or...
how many panels are you repairing?  Could you thermally bond scrap automobile radiators to the back?

My Siemens Panels have splurged some goop out from around the contacts...  something that I'm assuming that decreased their efficiency.  I don't know exactly what caused the problem, if it was heat, electricity, or both.  I could try to upload some photos of the cells later, but some (older) cells do not do well with too much heat.

tecker

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Re: Panel ventilation
« Reply #8 on: October 03, 2010, 03:42:08 AM »
Actually I don't think you can cool it off enough to counter the direct sun your going to loose some power . I t's nice to get the max from your panels and see the amperage jack up in the bright sun . I like to play around with candle power and see good performance from defused light and I worry about hale also so a sheet of plexy works in my installation

Madscientist267

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Re: Panel ventilation
« Reply #9 on: December 17, 2010, 04:35:34 PM »
Remember tho, it's a compound effect - Not only just absorbing and converting the light into heat, but the cells themselves produce additional heat when fully loaded. A flat sheet of 3/16" aluminum thermally bonded to the back side of the panel will help distribute it and gives up it's heat a little more effectively to the air. Considering doing it to mine as soon as I am convinced the corrosion isn't going to spread any further in the one panel.

Steve
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Ungrounded Lightning Rod

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Re: Panel ventilation
« Reply #10 on: December 17, 2010, 07:45:49 PM »
Remember tho, it's a compound effect - Not only just absorbing and converting the light into heat, but the cells themselves produce additional heat when fully loaded.

The cells produce the SAME heat, and more, when they're NOT loaded.  It's just inside the semiconductor (from recombination of electrons and holes) rather than resistive losses in the surface coatings and interconnect wiring.

The "more" is the power that WASN'T delivered to the outside load - maybe minus a bit from a few of the infrared photons from the extra electron-hole recombinations that managed to escape rather than being recaptured and thermalized.

Madscientist267

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Re: Panel ventilation
« Reply #11 on: December 20, 2010, 05:12:51 PM »
Touche, but the point was there - there's extra heat being made by the cells. Good point tho...

Steve
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How much magic smoke it contains does !

Ungrounded Lightning Rod

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Re: Panel ventilation
« Reply #12 on: December 21, 2010, 03:47:03 PM »
Touche, but the point was there - there's extra heat being made by the cells. Good point tho...

Basic point is that they get hotter when not feeding a load than they do when feeding one.

And in the worst case they only get as hot as if you left 'em sitting in the sun with no electrical connection.

picmacmillan

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Re: Panel ventilation
« Reply #13 on: January 07, 2011, 08:44:07 AM »
here is a photo of one of the panels i built years ago..we had(like dang stated) some vent holes as moisture built up in the panel from the sun etc..one thing if you do use holes for venting, is make them small enough so tiny bugs, spiders etc cant take up residence in you're  panel...
    another thing i did(not sure if it made any difference) was that i put some silica sand(the little packets you get in you're box when you buy new power tools) in the panel to absorb some moisture..i do think that stuff has a saturation point though? i was just testing it to see if it helped..take care, and good luck on youre project...pickster

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rain1224

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Re: Panel ventilation
« Reply #14 on: March 28, 2012, 07:16:12 PM »
To lower temperature? I always think that it will increase the temperature.

MaryAlana

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Re: Panel ventilation
« Reply #15 on: March 29, 2012, 01:43:32 AM »
You want silver solder for higher temps.

Bruce S

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Re: Panel ventilation
« Reply #16 on: March 29, 2012, 07:44:02 AM »
To lower temperature? I always think that it will increase the temperature.
Please explain your statement a little deeper. Not following what you're trying to say.
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richhagen

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Re: Panel ventilation
« Reply #17 on: March 29, 2012, 02:49:31 PM »
Wow, melting the solder, I've not had that problem on the two panels I have soldered.  I would worry about the EVA scorching at temperatures hot enough to melt the solder.  The first panel I built was an attempt at a sealed air space, which did not work satisfactorily.  I took that one down after water built up inside.  The solder junctions were still in tact though.  The second was laminated in a small laboratory vacuum oven.  I heated it a little too warm and gas bubbles formed in the laminate on that one though.  I have used it for various temp stuff but generally for no more than a week at a time, but again, the solder connections have not melted or failed.  I used common 60/40 solder on both panels.
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synovialbasher

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Re: Panel ventilation
« Reply #18 on: August 27, 2012, 07:23:04 AM »
I think it mostly depends on what area you're in. If you live in a humid climate with frequent rainfall, then I wouldn't try to ventilate it. Instead, if you can, use z-brackets that keep the panel slightly off the surface in which it's mounted. That will increase air circulation under the panel. If it's a significantly dryer climate, then it probably wouldn't hurt to ventilate the panel. Moisture and bugs could easily be an issue, but it all depends where you are.

eco007

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Re: Panel ventilation
« Reply #19 on: September 23, 2013, 04:01:03 AM »
In the New Jersey we use a solar chimney as a passive solar ventilation system composed of a vertical shaft connecting the interior and exterior of a building. As the chimney warms, the air inside is heated causing an updraft that pulls air through the building. To increase the performance we use glazing and thermal mass materials.

dnix71

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Re: Panel ventilation
« Reply #20 on: September 23, 2013, 02:10:45 PM »
This guy sprayed a mist on his panels, but the improvement wasn't much more than the energy cost to raise the water.
He got about 10% better output while misting.

http://tlug.webs.bailey.homelinux.net/solar/