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Thread: : Paralleling PV panels with differing illumination levels.
face picon face BY : RussellMc email (remove spam text)

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To: Whoever wants to comment.

Answer to at least 1. and 2. would be interesting.


Q: If you had PV panels which *each were evenly illuminated *but the
illumination level of each varied (eg 100%, 80%, 50% of 1 sun) and you
placed them in parallel, what would you expect the output of the low light
panels to be compared to what it would be if they were optimally loaded?
This could happen with eg panels pointing at different sky areas.

Note that, within one panel,  no cells are shaded more than any other - ie
all series strings have ~ equally illuminated strings. Only whole panels
have differing illumination levels.

Assume to make it 1/2 answerable that  the fully illuminated panel is
working at its max power point so Vout suits it perfectly and other panels
are added and the voltage does not change.
(This could happen with eg a stiff battery load or an inverter input with
feedback control etc). The arrangement is artificial but does not overly
change the answer , probably.

Assume panels behave like this. This is not meant to set specific V or I
curves but to just show general shape.
Lines are for insolation (sun energy) decreasing in 5% steps from top
(100%, 95%, 90% ...)
Blue dots are maximum power points at that insolation level.

[image: Inline images 1]

For question marked Q: at top of page:

1. What you would have said off the cuff before I asked the question.

2. What you would say off the cuff now I have asked the question.

Only if excessively keen:

3. What you would say after having done some figuring.
Here is my lonnnnnnnng answer (with summary at start).
Don't look at it until you have answered 1. & 2. above (if then).



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