[Power] SA

[Richard Smith]

>> 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