Voltage drop musings [RE-wrenches]

Wed May 2 12:41:38 PDT 2001

Yes and no.  PV modules are rated @ 1000w/m2 insolation and 77ºF (25C). 
That's not 77F air temp.  It's referring to the temp of the panel.  Of
course on a sunny windless day above freezing the panels are probably hotter
than 77F.  As the panel heats up above 77F it's power point voltage goes
down.  Someone please correct me but I think it is something like ~.05v per
1º C.  Now apply that factor to your average solar panel in the sun during
summer on the roof.  Lets say the panel is 144ºF (~62ºC).  37ºC x.05v/C =
1.85 volts off the power point voltage. 17 volts being the average PPV -
1.85 = 15.15 volts so that starts to hurt the power dramatically and
nullifies the value of MPPT in the summer.

The cold doesn't give extra current, it allows you to get the original
current you paid for.

Where is Bill Brooks?  He knows all these factors and can explain them a lot
better than I can.

Travis Creswell
Ozark Solar
----------
>From: hugh piggott <hugh.piggott at enterprise.net>
>To: RE-wrenches at topica.com
>Subject: Re: Voltage drop musings [RE-wrenches]
>Date: Wed, May 2, 2001, 1:23 AM
>

>I'm not a solar power person (although I have 500Wp on my roof) so I 
>am confused.  Is it the extra voltage from cold weather giving you 
>your extra current?

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