piclist 2016\04\28\045335a >
Thread: : Paralleling PV panels with differing illumination levels.
www.piclist.com/techref/index.htm?key=paralleling+panels
face picon face BY : RussellMc email (remove spam text)


On 28 April 2016 at 19:33, Justin Richards <KILLspamjustin.richardsEraseMEspamgmail.com>
wrote:

> Does this imply that two separate arrays, one facing East the other West
> (due to limited roof realestate) could be connected in parrallel without
> the need for a dual tracking inverter with only a small performance hit.
>
> ​Sort of, maybe.
Close to "yes in many cases"

If part of a panel becomes shaded ​then either
- the max current for all cells in the same series string is the current
that the shaded cell generates
- or if the shaded cell has protection diodes then for N cells in series
and 1 shaded cells thyen
current max is as before but
Vpanel_now  = Vpanel x n/(n-1) - 1_diode_drop

For panels illuminated evenly but at 2 different levels.

Working through my stack exchange answer, for 100% and xx% illuminations,
down to about xx >= 50% it looks fairly benign.
For ery low xx  it can still be remarkably good.
In my 2nd examples, for 20% insolation the 20% panel makes 79% of the
current it would at optimum but at aboyt 43/39ths the voltage so power drop
is
79% x 43/39 = 87% of the power it would otherwise make.

This is if the 100% panel still works at the old MPP.
Odds are the combination has a different Vmp and the end result will be
BETTER than calculated above.

As xx insolation falls there comes a point that Voc is <= the operating
voltage of the 1st panel and you get nothing.
In my SE answer that occurs at about 5% insolation (bottom line shown is
10%) so you don't lose much.


Russell
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Subject (change) : Paralleling PV panels with differing illumination levels.

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