[RE-wrenches] Off Grid, Cloudy Days, Solar Tilt Question

[Kirk Bailey]

Hi All!


We don't do a lot of pure off-grid systems and I recently ran across
something I wanted to run by folks with more experience in this area:
Optimal array tilt for our very cloudy PNW winters!

My understanding has always been that latitude plus 10-15 degrees was the
best tilt to address our winter energy shortage. However a paper I recently
read (1), makes a compelling case for a much shallower tilt in situations
where the cloud cover is so heavy that "diffuse" solar radiation is all
that makes it through. They indicate that under those conditions a
horizontal array will produce significantly more energy than even a
two-axis tracker!

Given that the challenge in our off-grid setups always seems to be making
it through the really cloudy stretches, and that there is usually enough
energy the rest of the time, should we be installing off-grid arrays at a
shallower angle?

Anyone tried this?


Kirk Bailey

kirk at abundantsolar.com

www.abundantsolar.com


(1) Kelly, N.A., Gibson, T.L, 2011, Increasing the solar photovoltaic
energy capture on sunny and cloudy days. Solar Energy 85, 111-125.
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