[RE-wrenches] Sola-ark cold morning

[Mac Lewis]

Hi Dana,

What type of batteries?  What battery mode?

If you have Lithium batteries with communication enabled, there are certain
modes that the BMS is running the charging show.  I've seen the Sol-Ark
throttle back charge as instructed by the BMS under these circumstances.
A quick check of this would be to start the generator and see if it's on
the battery management side or PV only side.

It seems like you are way below the MPPT upper limit if Im looking at the
correct QCell spec sheet.

As far as the temperature theory.  You can have temps on surfaces below
ambient.  This can happen in two ways that I am aware of: radiation and
evaporation.  The radiation effect occurs because the cold night sky (very
cold) is exchanging heat with a surface.  This is why you can get ice on
lakes above 32F.  It's very complex to model this but I doubt you could
come close to lowering the temperature far enough to drive the Voc out of
the MPP range.

Also, there will be competing heat exchange trying to drive that
temperature back to ambient.  For example if you had a lot of wind in a
clear cold night, the convection heat exchange from the wind would actually
warm up the surface.

Evaporation (or any phase change) can drop an object's temperature below
ambient as well.  It will pull latent thermal energy from objects in order
to change the phase of the molecules.  This actually has a stabilizing
effect on temperature typically because it takes a lot of energy to change
phase.  This is why people use large water barrels in greenhouses to
release latent energy to prevent freezing.

Please let us know what you find out.

Thanks!

On Sun, Dec 4, 2022 at 6:22 AM Dana Orzel via RE-wrenches <
re-wrenches at lists.re-wrenches.org> wrote:

> Hey Now All Wise ones!
>
>
>
> An of gird client emailed yesterday that his Solark had been accepting
> only 350 watts of a 4KW input from the array. The modules are Q-cell 325
> watt 2 strings of 7 modules.
>
>
>
> Sunrise, full sun, no clouds so no edge of cloud effect, negative temps @
> -6˚F, he waited all day with no improvement or change in the charge rate
> consistent 350watts input & then same thing next morning. Negative temps &
> full sun & 350watts solar input.
>
>
>
> He turned the Solark off for 10 minutes & then turned it back on & 4KW
> charge input returned. The Solark did not turn off or deliver any alarm or
> warning.
>
>
>
> My initial thought was over-voltage spike, we designed for a -25˚F
> scenario & 110 PSF snow load. Beefy!
>
>
>
> I did not ask if it was windy additionally. Could this contribute to a
> colder array temp? I have always been of the impression that wind chill did
> not affect metal or glass that it has to do with moisture being driven off.
>
>
>
> Thoughts & suggestions?
>
>
>
>
>
>
>
> Dana Orzel                              Great Solar Works, Inc.
>
> *C - 208.721.7003                       dana at solarwork.com
> <dana at solarwork.com>*
>
> Idaho Contractor - # 028765         Idaho PV # 028374
>
> www.greatsolarworks.com            www.solarwor.com
>
> *"Responsible Technologies for Responsible People since 1988"  *
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-- 



Mac Lewis

*"Yo solo sé que no sé nada." -Sócrates*
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