Design question

Hi,

I have a solar panel here that I thought I could fiddle around with (being
bored and all). What I want to do is fit some mirrors around it and
concentrate about 4 times as much sunlight on the same surface area of the
panel. I thought maybe I could save money on buying 4 panels...has anyone
tried this?

Anyway, I was thinking of getting out my ruler and working out the angels on
paper, but is there any software (free if possible) where i can design
something like this without too much complexity?

Thanks in advance!
Joe,

 

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.

 

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...

 

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%.

 

Hi Joe & Average;

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:
http://www.solar-trackers.com/concentrator2.htm

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

--
Home of the $35 Solar Tracker Receiver
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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

 

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.

 

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.

 

What are you trying to say?

 

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

 

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