On 27/05/2019 21:52, misterroy wrote:
A friend of a friend is putting in a loft extension, with new dormer
windows. The new window will cast a shadow on part his neighbour's
photo-voltaic array. The neighbour seems to know his stuff, but part
of what he is saying sounds strange.

As best as I can remember, the panel nearest the dormer will drop in
efficiency, by say 20%. This bit I understand, due to the shade. (The
neighbour has built a model and used a torch to help his estimates).

However, according to the neighbour, this is not the end of his
losses. Because one panel is at 80% efficiency, the others have to
drop their efficiencies too.

The neighbour is taking his loss on the chin and not hassling, but
how can shade on one panel effect the efficiency of every panel?

It limits the maximum current flow through the weakest link in the
chain - the panels are in series so one in shade limits them all.

--
Regards,
Martin Brown