Derating 24v Solar Panels?

MrWizard wrote:

jrnymn7 wrote:
red,

Does it not go without saying, as Isc goes up, so does Imp? If using pwm, available panel current would go up as the panel warms. If using mppt, the power curve shifts in favour of higher current, lower voltage. The mpp goes up and to the left on the knee, correct?

As solar radiance goes up voltage and current rise
As the panel heats up voltage and current drop
The best solar is on top of a cold mountain on a clear day
Second best is a cool clear spring day with panels pointed directly 90° with Sun
Warming does Not increase output, cooling does
Try this test take a panel and controller connect to a battery on a 90° day, point into sun read the panel voltage come back an hour later, load or no load the panel voltage will be less, now without removing the meter take a cool wet rag and wash the the panel face
Watch the voltage climb back up
Remember MPPT works with difference between battery charge level and panels , the lower the difference the less MPPT gain

Please see page 5 of 5, Temp Comp

For the 24v panels I'm considering...Temperature coefficients of Isc: +0.06%/

Although it's a much smaller coefficient than that of Voc, it is positive, not negative/inverse.

I have seen well over 9a Isc from my 12v/140w poly's, with an Isc rating of 8.37, on a mild day, pointed.