Author Topic: Boosting P V output with mirrors ?  (Read 8076 times)

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petect

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Boosting P V output with mirrors ?
« on: October 25, 2010, 09:40:46 AM »
With thermal panels the results are predictable. I could even notice a clear boost of the output from my window-mounted warm air panels when there was a coating of snow on the ground. What about P V's?  Would directing some additional light onto PV panels be an effective way to boost their output, especially during the winter or when panels are mounted in less than perfect locations?             ( obviously over doing it wouldn't be good.)  Providing a reflective surface to direct  more light on the panels should be a whole lot less expensive than buying additional panels to boost output. This seems pretty basic, and I'm sure it's been tried many times, but I have never heard of anyone doing it. Sometimes what seems obvious isn't - and that's why I ask.
Pete

dnix71

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Re: Boosting P V output with mirrors ?
« Reply #1 on: October 25, 2010, 10:05:35 AM »
Yes, but you should exceed the light/heat limits of the panels. In a high latitude area that might work okay, but nearer the tropics you'll scorch the panel.

You can get a sunburn at the beach even under an umbrella from reflected light, so your panel could get a sunburn the same way.

There have been experiments with special cells and concentrators like the "Solar Ball" in Australia, but I don't know of any commercial success with it.

Nil

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Re: Boosting P V output with mirrors ?
« Reply #2 on: October 25, 2010, 12:26:03 PM »
Reflectors were used before at the old Carrizo/ARCO solar plant in the early 1980's. The panels appear to have been made with a plastic substrate that turned brown faster in the strengthened light. It is said that the color change did not really affect the output of the panels, I have 36 of these old panes that are as old as me... in 27ish years they degraded from 35w per to ~30 watts even after their initial hard abuse.

It seams easily possible to increase the output of your panels this way, just try not to overdue it.

here are a couple links I have about the Carrizo's

http://geoimages.berkeley.edu/GeoImages/BainCalif/Cal400/photovol.html
http://ludb.clui.org/ex/i/CA4965/
http://www.otherpower.com/otherpower_solar_used.html

good luck

DamonHD

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Re: Boosting P V output with mirrors ?
« Reply #3 on: October 25, 2010, 01:20:06 PM »
Even on a small scale mirrors can boost output, eg see:

http://www.earth.org.uk/note-on-solar-PV-for-diffuse-light.html

Note that some PV is designed to be used with concentrations of up to hundreds of times/"suns", eg some of the multi-junction ~40% efficient devices.

Rgds

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petect

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Re: Boosting P V output with mirrors ?
« Reply #4 on: October 29, 2010, 11:21:02 AM »
Thanks Guys

Damon
That's an interesting site.

I don't think I would actually try to use mirrors, and would especially  avoid any reflected light that is concentrated. But it seems like some increase in output could be achieved by using flat panels covered with metal foil, or painted with gloss white paint aimed at the PV cells, at a very low cost.

Pete

Beaufort

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Re: Boosting P V output with mirrors ?
« Reply #5 on: October 29, 2010, 12:06:07 PM »
If nothing else, mount some reflective panels on the East and West sides of the array to gather more morning and afternoon sun.  This way the reflectors don't hit the panel with reflected light when the sun is directly overhead.  I know that hand tilting the panels to follow the arc of the sun can increase output to 30%, and the cost of a few cheap mirrors or mylar is way less than an automatic tracking system. 

This may be OT, but can solar panel output increase by keeping the temperature of the panels lower?  I've always thought about making a panel into a hot air collector just by adding another layer of glass.  The heat benefits are clear, but I've been curious about any increase in PV output by taking the heat away.  It seems silly that we're putting PV panels up on a roof and absorbing that heat energy without using it.

Bruce S

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Re: Boosting P V output with mirrors ?
« Reply #6 on: October 29, 2010, 12:50:19 PM »
If nothing else, mount some reflective panels on the East and West sides of the array to gather more morning and afternoon sun.  This way the reflectors don't hit the panel with reflected light when the sun is directly overhead.  I know that hand tilting the panels to follow the arc of the sun can increase output to 30%, and the cost of a few cheap mirrors or mylar is way less than an automatic tracking system. 

This may be OT, but can solar panel output increase by keeping the temperature of the panels lower?  I've always thought about making a panel into a hot air collector just by adding another layer of glass.  The heat benefits are clear, but I've been curious about any increase in PV output by taking the heat away.  It seems silly that we're putting PV panels up on a roof and absorbing that heat energy without using it.
Beaufort.
Certainly not OT. There was a discussion on here this past summer about just this subject.

Not sure an extra layer for glass would be a good idea , however what the test done now has validity has I've seen google ads for them.
Heat IS the big draw back and lowers the output of Solar PVs. So removing the heat build up the way they did it ( ran glycol through back mounted tubes) helped keep the rated output up as close as possible.

Somoa has a setup that uses specific angled reflectors, maybe he'll jump in here with the great pics he has.

Cheers
Bruce S

 
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GaryGary

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Re: Boosting P V output with mirrors ?
« Reply #7 on: November 04, 2010, 10:41:59 PM »
Hi,
There are some links to projects that use reflectors to increase PV output here:
http://www.builditsolar.com/Projects/PV/pv.htm#Tracking
See the ones on "Arhimedes", "Low cost tracking ridge concentrator", and the paper on PV pumping that makes use of reflectors.

I think its likely that commercial panels will hold up to some extra reflected light in that they have to stand being installed where there might be a snowfield or reflective roof surface.

Gary





Clifford

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Re: Boosting P V output with mirrors ?
« Reply #8 on: November 22, 2010, 05:11:20 AM »
Assuming you have a glass face, then it should hold up to the sunlight.  But the cells may not.

Anybody know if the typical silicone cells generate significant power in the UV an IR bands?  If not, one should probably shield for UV and IR.

Heat dissipation would certainly be an issue with too a concentrated system.  I've been looking at the Sanyo Bifacial panels, and they specifically say not to install mirrors to the back face.

The triple junction cells actually are rated to have better efficiency with concentrated power than without.  I think they are kind of out of reach from most home users, but I think they are typically sold with a little tiny solar cell and a lens concentrator in front, and a solar tracking system.    It is likely the standard silicone cells would also have efficiency improvements with concentrated power (other than the heat issue).

There was a discussion on this BBS a while ago about vertical mounted panels with a piece of stainless mounted horizontally below (with hinges/springs) to act as a mirror.  The idea was that it would be easier to maintain, and keep free from ice and snow.  Passive with the "tracking".

I don't know if it was ever tested, but the theory sounded good.

oscar11

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Re: Boosting P V output with mirrors ?
« Reply #9 on: September 03, 2015, 11:25:31 AM »
If you don't exceed the capacity of the panel then degeneration shouldn't be a problem, right? So at noon the reflection ratio is 1:1, at 9am maybe it's 2:1, and at 6am maybe it's 4:1.  If there's a week of cloud cover and your batteries are getting low break out the reflector. According to that guy the ratio appears to be 5:1. And if you want to get really crazy what's the ratio under a full or half moon?

dbcollen

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Re: Boosting P V output with mirrors ?
« Reply #10 on: September 03, 2015, 12:35:26 PM »
SILICONE cells? new technology? do they come in a tube?  ;D ;D ;D silicone is a rubber like substance, solar cells are made of silicon

oscar11

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Re: Boosting P V output with mirrors ?
« Reply #11 on: September 04, 2015, 11:46:18 PM »
A full moon is about 100000:1.   A very overcast day is about 1000:1.   A cloudy day is 100:1 Possible not practical.