Thanks, Don,
Performance predictions such as from PV Watts VASTLY underestimate PV
production in our area. For example, PV Watts estimates 940 kWh/kW for
a 4:12 pitch at 180˚, whereas such systems are actually producing up
to 1300 kWh/kW (as measured by a renenue-grade production meter). We
have to set the derating factor to nearly 100% in order for the
predictions to match.
I assume that is partly due to coarse irradiance data (not accounting
for higher irradiance for our location in the rain shadow of the
Olympic Mountains), but also due to our clear, cool, windy summers,
good natural washing, and (perhaps) dispersed distribution of
irradiance.
I want to know if the opposite is true: Do performance predictions
OVERESTIMATE PV production in areas with historically high irradiance,
but significant soiling and temperature issues.
Thanks,
-Kelly
Kelly Keilwitz, P.E.
Whidbey Sun & Wind
Renewable Energy Systems
ke...@whidbeysunwind.com
360-678-7131
On Jun 9, 2010, at 8:59 AM, i2p wrote:
On Jun 9, 2010, at 8:22:12 AM, "Kelly Keilwitz, Whidbey Sun & Wind" <ke...@whidbeysunwind.com
> wrote:
Thanks, Joel
How about PV systems away from the coast, in a hotter, dustier
location, like Bakersfield, Fresno, Sacramento, Palm Springs,
etc........?
In central CA we do a little better. I casually monitor several
systems in this area and expect around 1500-1600 kwh/kw. per year.
Don Loweburg
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