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Posted by Chris Hill on May 6, 2008, 12:02 pm
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Is there any good info out there on how much hazy skies have on pv
output? I've thought of messing with solar, but at certain times of
the year, a really clear day can be hard to come by.
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Posted by Anthony Matonak on May 6, 2008, 3:24 pm
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Chris Hill wrote:
> Is there any good info out there on how much hazy skies have on pv
> output? I've thought of messing with solar, but at certain times of
> the year, a really clear day can be hard to come by.
There is plenty of insolation data available from outfits like
NREL. The output of a PV cell (and panel) is fairly linear.
That is to say, if you double the light you get nearly double
the output if everything else stays the same. If you cut the
light in half then you get half the output.
Your question is, "How much does hazy skies cut down the amount
of sunlight?" and that has no exact answer because there is no
exact definition of haze.
You can always buy a little solar panel and measure the output
to see how much this varies. :)
Anthony
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Posted by Kitep on May 6, 2008, 8:41 pm
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> Is there any good info out there on how much hazy skies have on pv
> output? I've thought of messing with solar, but at certain times of
> the year, a really clear day can be hard to come by.
>
I don't know specifically what hazy days would do, but there is plenty of
information about average sunfall. I believe it's called "insolation", and
it's the number of "peak hours" of sunlight per day. For example, in
Cincinnati OH, it's 4.5. This doesn't mean we have 4.5 hours of full
sunlight and it pitch black for the other 19.5 hours, just that when you
take the total sunlight per day, it comes out to 4.5 peak-hours/day.
Then you would look at the solar panel and find its peak Watts. For
example, it might say "50 watts peak power". Multiply the 2 numbers
together. 50 x 4.5 = 225 Watt-hours/day. Divide by 1000 to get Kilowatt
Hours/day.
Of course, in summer it produces more, in winter it produces less. But
averaged over a year, a 50-watt panel would supply me with 225 Whr/day.
Nrel has a neat map showing average sunlight, but alas, I can't find my link
:(
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Posted by Solar Flare on May 6, 2008, 10:33 pm
Please log in for more thread options Mine produce 0 to 100% depending on the darkest to the lightest hazy day. A
little haze doesn't seem to affect them. Light fog gives nothing.
> Is there any good info out there on how much hazy skies have on pv
> output? I've thought of messing with solar, but at certain times of
> the year, a really clear day can be hard to come by.
>
>
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