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How do you test a solar panel in winter? - Page 2

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Posted by Jakthehammer on February 2, 2008, 8:46 pm
 

Sorry too, I did't think your comment was bad, it was not quite clear,
that's all, better forward voltage is the same as less voltage drop.  Yes
they may not be able to handle large current, the easiest way to find out
is to look at the size of the diode.  Usually larger diodes (stud type)
handle much higher current.





Posted by Al Forster on February 2, 2008, 3:12 am
 

You're mostly correct, but it's bypass diodes not blocking diodes. A
module with no bypass diodes with one shaded
and many unshaded cells will only output the current of the shaded
cell (under short-circuit conditions or at least, beyond the "knee
voltage"). In the worst case, the current generated by the other cells
can be dumped through the shaded cell, sometimes generating enough
heat to cause that cell to crack. Some manufacturers use bypass diodes
to alleviate this effect, but usually for strings of four or more
cells (i.e. not for each cell). Blocking diodes are most generally
used to prevent current flowing back from charged batteries through
the solar modules (eg at night), or for parallel-string systems where
current from a "good" string could dissipate in a "bad" string.


Schottky diodes have a lower forward voltage drop than silicon power
diodes, so they're often used for (forward) bypass diodes. Schottky
diodes are not generally used for (reverse) blocking diodes due to
their high reverse leakage current (compared with silicon diodes).

Al


Posted by =?iso-8859-1?Q?Roland_M=F6sl?= on February 1, 2008, 6:49 pm
 
Winter is the best time to test a solar panel

Compere it with other PVs under cloudy weather.

http://live.pege.org/2005-house-plan/photovoltaic-compare.htm


--
Roland Mösl
http://car.pege.org  cars and traffic
http://live.pege.org  building and live
http://www.pege.org  


Posted by mike on February 1, 2008, 10:54 pm
 Roland Mösl wrote:

Thanks for the input.
Most interesting thing about that page is that the
"super" panel is 2.5x the size and puts out 1.7x the amps.
Sure, it works better at low light.  Good choice if you live
in dark climate, but it's not really an apples to apples comparision.

Wouldn't it be better and smaller to use two of the small panels
in series in winter and parallel in summer?  Or just be done with it
and use electronics to maximize power output in any light?

When people pull "shady" comparisions like that, I wonder else
they're not telling me...

--
Return address is VALID!

Posted by =?iso-8859-1?Q?Roland_M=F6sl?= on February 2, 2008, 5:28 pm
 
Tell us where You live and what application You have.

When it comes to power an off grid application in winter,
I am only interested in the performance at cloudy weather
conditions.


--
Roland Mösl
http://car.pege.org  cars and traffic
http://live.pege.org  building and live
http://www.pege.org




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