: Paralleling PV panels with differing illumination levels.
RussellMc email (remove spam text)
On 28 April 2016 at 19:33, Justin Richards <gmail.com> justin.richards
> 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.
> â€‹Sort of, maybe.
Close to "yes in many cases"
If part of a panel becomes shaded â€‹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
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.
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