Design question

I tried this with a thin film panel, but I would not try it with a silicon cell panel. The panel gets too hot and the EVA film used to encapsulate the cells can turn brown. I do not know of any software, but a good calculator and some trig should do the trick.

I've always thought trying to concentrate the sun onto a panel with mirrors or lenses is a bad idea, the panel will get a lot hotter than normal, and we all know that a solar panels output drops as it's temperature rises,

4 more panels would be a better bet i rekon.

Concentration causes heat, discoloration, and lessens the lifespan.

--
Steve Spence
Dir., Green Trust, http://www.green-trust.org
Contributing Editor, http://www.off-grid.net
http://www.rebelwolf.com/essn.html

That may work in the winter when temps are low but in 95f+ temps I would not try it. As stated below there is a good posibility you could damage your panels.

Joe KI4ILB What makes solar panels work? It is the smoke... If you let the smoke out of them, they quit working...

(being

the

anyone

angels on

It worked fine in the summer with an ICP 5 watt 12" x 12" panel. However, the front glass got so hot that when I tried to clean it off with a damp towel, the temperature difference caused a crack in the glass. Will not do that again.

A good trick is if you can get 4x the normal wattage without decreasing the lifespan by 75%.

--
Steve Spence
Dir., Green Trust, http://www.green-trust.org
Contributing Editor, http://www.off-grid.net
http://www.rebelwolf.com/essn.html

Yes, I have investigated and experimented with this a bit. However, 4X seems a bit high. 2X seem quite doable in cool weather.

See a commercial manufacturer:

I have contacted most manufacturers. The warrantees basically don't say you can't use concentration. They do say you can't over heat the panels. The criterion is discoloration of the encapsulant.

If you are careful and check the panel temperatures 2X concentration may be a good choice. Of course concentrators require solar tracking. So in addition to the higher power output due to concentrating you also increase the energy per day due to tracking.

An even greater concentrating method is to use 3 or 4 heliostats that feed light onto a north facing, (south facing for our friends down south ), PV panel. These heliostats are controlled with a temperature sensor on the panel. When it gets to hot some of the heliostats back off.

This kind of a system is ideal the further north and colder the climate.

Maybe not.

Duane

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Very difficult.

You get only the current for the least illuminated cell, so even light is required, but hard to obtain.

The cells with the highest illumination will be the hottest and will be damaged more than the others.

There is a reason you do not see this being done.

Bill Kaszeta Photovoltaic Resources Int'l Tempe Arizona USA snipped-for-privacy@pvri-removethis.biz

No, I got 2x, I did not feel like tracking the sun by hand.

You might double the output of a horizontal panel under an inch of water in a greenhouse polyethylene duct to make a draindown solar collector with a mirror above it. The plastic and water layers only reduce the solar intensity by about 6%, since the refractive indexes are close to each other, and this arrangement allows collecting the other 85% of the solar heat as well as 15% electricity.

For more concentration, try an approximate non-tracking linear parabolic reflector (3-4 flat segments) instead of a mirror above.

Nick

Joe,

Do what I do, mount them by the shore of a small lake. Now that's bright. Using my photo light meter, point towards land and I get 250th @ f4.5. Toward the lake I get 1000th @ f22.

I started a thread a while back about concentrating light and quickly came to the same conclusion; tracking the sun will produce more than concentrating the light.

I can see you know nothing about PV panels.

My panels increase output almost 25% by hitting them with a garden hose.

Stop spamming the NG with your silly bulletin board advertising.

max, and risk causing

panels. And if you have

will cause scratches in

--------------------

--------------------

going to try some

the lake water

is a weekend place)

pole, drop a bag of

switch. Using a misting

on once in a while

panels enough to

now is do I mist the

windex every week on

Maybe not, with a fixed linear parabolic reflector.

Nick

Same here. Even though I have the panels on a South exposure, they get peak power well into the afternoon because of the SW-W expanse of water. Especially when it freezes.

--
derek

them

in the US knows

believes you own a pv

cooling with water,

installed it

Carrizo quad-lams were used in a concentrating setup of some sort. I suspect some real figures are available if you dig deep enough. I have a set of these that were taken out of service. They are discolored, but other than that, they work fine.

Nick's idea of having a panel under an inch of water seems like a solution to the heat build-up, as long as the water can be circulated off and kept cool over the panel. One of the benefits of solar is the "install it and forget it" aspect. A system like this might be fine for a huge installation with a dedicated staff, but for home use, the system will eventually run dry of water or not be maintained (due to vacations - illness - job duties - laziness), and fail.

For more widespread use rather than experimental, you'd have a ballcock that tops the water up, a small deioniser (low feed rate needed) and plastics that would survive long term. So no maintenance.

The panels should be quite happy sitting in the DHW @ 65C, or a separate deionised circuit @ 70C.

The plastic cover of the unit can be light scattering to give good evenness of illumination, if necessary, with some loss. This would avoid light holes due to insects, birdshit, passing birds etc.

Finally, in the event of pump failure, the panels are protected by boiling. A whistle (with insect mesh and filter) would let anyone around know it was malfunctioning, while the water boiling would save the panels from significant damage.

I dont know how much concentration could be done this way. But I bet a trough of water etc could work out much cheaper than more panels in some cases.

Not sure what the metallisation on the panel would think of hot deionised water, maybe the panel would need gold flashing.

NT

While this may seem like a good idea, remember that temnperature adversely affects solar panels. The hotter they are, the less efficient they are. Also, with too much heat, life span will be decreased, and if they are warranteed, this will likely viod you warranty.

The increase of power output may not be enouh to make it worth messing with, and you would have to have a moving tracker to keep the mirrors at the correct angle, complicating things still further.

Doug

Average Shmo wrote:

I don't see that as inevitable. No moreso than other draindown systems.

Why deionize?

I measured a 6% intensity loss with an inch of water and TWO layers of

0.006 inch 5 cents/ft^2 cloudy greenhouse polyethylene film duct with a 4-year guarantee. An approximate linear parabolic reflector with 2 or 3 flat planes can help avoid hot spots.

Under 2-3 suns, they might be OK for a month or two dry.

The film duct would sit on top of the panel with water between the films and no water touching the panel face.

Nick