[Power] SA

[Ed McNierney]

Thanks; and extra thanks for the data (and rules of engagement would be a big help, too).  I wasn't at all intending to suggest the temperature would be a problem, but rather to correct an apparent impression that heat was good.  Having the real data's much better!

	- Ed


On Feb 25, 2010, at 12:15 PM, Richard Smith wrote:

>>> In South Africa, when the XOs (1.0) had some charge, the panels would
>>> hold the charge at a constant level, not charging or discharging.
>>> 
>>> When the XOs were completely dead, the panels would not charge the
>>> laptops even on an extremely hot, sunny day.
> 
> 
>> Remember that while "sunny" is good for solar panels, "extremely hot" is not.  Solar panels work better at low temperatures rather than high ones.
> 
> My apologies but I'm going to use this as an example.  The above
> response is the type of post that I would rather NOT see on this list.
> While the above is indeed a  true statement its not useful because it
> has no qualifiers on it any may lead one to thing that a "extermely
> hot" day will not produce solar power.  Extremely hot for a human is
> not the same as extremely hot for a solar cell.
> 
> I'm working on a "Rules of engagement" document for this list
> outlining the types of responses I want to to see.
> 
> a-Si panels (which we have) have a temperature decline in efficiency
> by 0.15-0.25%/°C  I'll have to request exactly what  ours is from the
> manufacturer but lets use .25% as worst case.  STC for the cell is 25
> degC.  So even if the cell temperature was 100 degC you are only
> talking about a 20% in output capacity at STC of 1000W/m^2 (called 1
> sun). So the 10 W would be come 8W.  Still enough to charge the
> battery.   One would assume that a sunny day in Africa would reach 1
> sun.
> 
> And according to here:
> 
> http://genohm.eu/index.php?option=com_content&view=article&id=32&Itemid=28
> 
> They list that a-Si generally performs better in this regard and that
> surface temp is usually air temp + 25C and that at a surface temp of
> 60 degC there was no loss in output over STC.
> 
> Granted the above is from people trying to sell you thin film PV so it
> may be skewed but I've only found supporting documents rather than
> conflicting.
> 
> So I don't think that extremely hot is an issue here.
> 
> -- 
> Richard A. Smith
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