Ping Larry
 

On Tue, 27 Jan 2009 22:11:33 +0000, Larry wrote in
:

If you look at the cells on a heavily loaded panel, notice how brown they
get overheating in the noonday sun so quickly? That should answer your
above question. ANYTHING you can do, like DISCONNECT (read that series
open circuit regulators) an unneeded solar panel in the hot hot sun to GET
THE CELL TEMPERATURE DOWN is always a GOOD thing. The way to get the heat
down is to LOWER, not raise, the cell current. That part of the cells that
don't have any current going through them never seems to change from that
blue silicon color to that brown, scorched-earth look. It's the CURRENT
that fries them. Shunt regulators simply drive up the cell current, which
drives up the cell HEATING until the cell fails....making the cell salesmen
simply smile. Shunt regulators are for suckers.....
...
All solar chargers on boats seem to suck....about like those boat fans
buzzing away over your bunk....cheap crap. But, I'd never use a shunt
controller as it fries the cells in a hot sun at low latitudes. They all
turn BROWN where the current flows!

I've never seen a solar cell fried in the sun unloaded......even in the
Iranian desert mountains.

Turning brown is caused by UV, weathering and environmental heat, not
heating from load, and has a relatively small effect on power output (on
the order of 5-10%). See:
* http://www.freepatentsonline.com/6114046.html
* http://www.faqs.org/patents/app/20080276983
* http://www.wipo.int/pctdb/en/wo.jsp?...A=WO2005006451
* http://www.patentstorm.us/patents/54...scription.html
More modern cells are more resistant to this kind of discoloration.
Keeping the cell under load isn't an issue.

--
Best regards,
John Navas, publisher of Navas' Sailing & Racing in
the San Francisco Bay Area http://sail.navas.us/

Ping Larry
 

John Navas wrote in
:

Turning brown is caused by UV, weathering and environmental heat, not
heating from load, and has a relatively small effect on power output (on
the order of 5-10%). See:


If that were true, each whole cell would turn brown, not just the center of
the cells where the conductors are directing the current through it. The
current through the cell resistance adds a lot of heat to a cell generating
power.

Case in point, there are solar panels all along our local interstate now
over 10 years old. They are lightly loaded for their size only generating
enough power to charge some gelcells and power the roadside webcam and its
upload server. The cells have not discolored from 10 years in the HOT
South Carolina sun that I can detect.....as they have low current in them
except for in the first morning light until the gelcells recharge from
running the cam all night in the dark.

The panel on Lionheart is 1988 and is nowhere near a charger for the
massive monster house batteries banks' 1400 AH and loads. It spends all
its time completely saturated. The part of the cells where the heavy
current goes through them has turned them all a very light brown so you can
hardly recognize them as solar cells any more. They still generate a few
amps like that but nowhere near what they should.

Cap'n bought a new panel to replace it. But, alas, he didn't have time to
install it and forgot the panel was laying on top of the old panel when his
guests showed up for a harbor cruise. He forgot the new panel, a really
nice one, was loose. When the boat heeled, the new panel slid over the
side into the harbor mud in 50' of channel. It's best not to mention
replacing the old solar panel, even today. If you mention it, make sure
you do so as you're stepping onto the dock for the last time headed home
for a couple of weeks.....(c;]

Glad it wasn't me involved in that one.....

Ping Larry
 

On Sun, 01 Feb 2009 21:30:21 +0000, Larry wrote in
:

John Navas wrote in
:

Turning brown is caused by UV, weathering and environmental heat, not
heating from load, and has a relatively small effect on power output (on
the order of 5-10%). See:


If that were true, [SNIP]

It is true, as shown by my supporting citations.

Typical solar panels convert only about 20% of captured solar energy
into electricity. The other 80% is wasted as heat. Thus if even half
the power of the solar cell were converted into additional heat, it
would only increase heating by about 12% (10 ÷ 80), which isn't terribly
significant.

If you have any real evidence (citations) to the contrary, then by all
means post it.

--
Best regards,
John Navas, publisher of Navas' Sailing & Racing in
the San Francisco Bay Area http://sail.navas.us/

Ping Larry
 

John Navas wrote:
On Sun, 01 Feb 2009 21:30:21 +0000, Larry wrote in
:

John Navas wrote in
:

Turning brown is caused by UV, weathering and environmental heat, not
heating from load, and has a relatively small effect on power output (on
the order of 5-10%). See:

If that were true, [SNIP]

It is true, as shown by my supporting citations.

Typical solar panels convert only about 20% of captured solar energy
into electricity. The other 80% is wasted as heat. Thus if even half
the power of the solar cell were converted into additional heat, it
would only increase heating by about 12% (10 ÷ 80), which isn't terribly
significant.

If you have any real evidence (citations) to the contrary, then by all
means post it.

The funny thing is, that a loaded solar array is cooler than
an unloaded one.
The unloaded one absorbs heat, the loaded one less, because you
convert to electricity, and use it.
So by loading it , you remove heat.
Not all of it, because part of the energy is lost as heat.