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

[Kirk Bailey]

 Dave,

    The paper reference was at the bottom of my original post (1), but a
quick summary of what they recommended was exactly what you mentioned -
Have two axis trackers "go horizontal" during heavy overcast instead of
continuing to track the sun to improve production!

    I'm familiar with the general tradeoffs for off-grid in terms of array
oversizing, generator usage, and load shedding:  We have had past customers
that have made it work for them, and others that couldn't and ultimately
decided to get a grid connection!

Cheers,

Kirk Bailey
kirk at abundantsolar.com

Kirk,

Can you reference your paper on this? So many variables and each location
will be different. Most dual axis
trackers can always be left flat or any angle so that does not make sense
to me.

You have to design for winter offgrid if the location is worth it. Or, alot
of hours on a genset.

Super large arrays in your area will help give you more days/hours before
you need the iron genoa.
You have to decide if it is worth the money. The home has to have the
ability to shed some loads also.



*Dave Angelini Offgrid Solar
"we go where powerlines don't"
   <http://members.sti.net/offgridsolar/>https://offgridsolar1.com/
<https://offgridsolar1.com/>  <http://members.sti.net/offgridsolar/>
e-mail  offgridsolar at sti.net <offgridsolar at sti.net>
text 209 813 0060*


On 2023-10-25 3:46 pm, Kirk Bailey via RE-wrenches wrote:

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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