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?
ta

On Mon, 27 May 2019 13:52:56 -0700 (PDT), 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?
ta

The current through the shaded cell will be reduced by the shade. As
all the cells are in series the entire system suffers from reduced
output.

There are 2 common solutions; use micro-inverters or optimisers for
each panel.

Some systems have more than one array running in parallel

On Monday, 27 May 2019 21:52:59 UTC+1, 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).

Another relevant question is whether the PV owner actually has a right to light for his panels. Did he buy an easement when he set up the panels? I am guessing not. In which case I dont' see why it is the dormer-builder's problem.

To cite an obvious example: you can't prevent a building being built simply by setting up an array of panels that will be shaded by it.

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

On 27/05/2019 23:23, Martin Brown wrote:

It limits the maximum current flow through the weakest link in the
chain

Why should it?

Bill

On Monday, 27 May 2019 21:52:59 UTC+1, 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?
ta

The other thing to note is that shading 20% of a panel drops its output by much more than 20%, for the same reason.


NT

Well there is something in the back of my mind about the way the panels
work together and when the system switches from supply to grid etc. If the
whole is measures by output of everything then in effect there will be a
drop in efficiency as the system will not look at them individually but as
a whole.


It might of course be that the panel in question could be relocated to
preserve the status quo, it will much depend on orientation and when shadows
are cast. I don't think I'd be so charitable about losing what small power
I'm making to such an extent, I'd suggest compensation might be needed.
Brian

--
--
From the sofa of Brian Gaff -

Blind user, so no pictures please!
Today is Yesterdays Tomorrow.
"misterroy" wrote in message
...
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?
ta

On 28/05/2019 03:39, Bill Wright wrote:
On 27/05/2019 23:23, Martin Brown wrote:

It limits the maximum current flow through the weakest link in the
chain

Why should it?

The current is produced by light creating free electrons. In the shade
the silicon is almost an insulator. The maximum current that the thing
produces is limited by the panel that can provide the smallest current.

Without photoelectrons to move the rest just heat up a bit more and make
the voltage across the weakest panel higher. The panel in shade behaves
like a resistor preventing a higher current from flowing.

It isn't unlike the situation where you put a mixture of used and unused
batteries in a torch. The weakest one limits performance greatly.

--
Regards,
Martin Brown

On 28/05/2019 03:39, Bill Wright wrote:
On 27/05/2019 23:23, Martin Brown wrote:

It limits the maximum current flow through the weakest link in the
chain

Why should it?

Bill
Good question aqnd one that had been botrehring me

https://www.pveducation.org/pvcdrom/...cted-in-series

....and other sources imply that by and large PV cells are current
sources and thats why series connecting them is a Bad Idea.

OTOH series connecting them makes inverters more efficient and means
less wires flying around the roof, so its a Good Idea.

Really PV are just pants anyway so who cares?


--
Future generations will wonder in bemused amazement that the early
twenty-first centurys developed world went into hysterical panic over a
globally average temperature increase of a few tenths of a degree, and,
on the basis of gross exaggerations of highly uncertain computer
projections combined into implausible chains of inference, proceeded to
contemplate a rollback of the industrial age.

Richard Lindzen

On Tuesday, May 28, 2019 at 8:36:37 AM UTC+1, Brian Gaff wrote:
Well there is something in the back of my mind about the way the panels
work together and when the system switches from supply to grid etc. If the
whole is measures by output of everything then in effect there will be a
drop in efficiency as the system will not look at them individually but as
a whole.


It might of course be that the panel in question could be relocated to
preserve the status quo, it will much depend on orientation and when shadows
are cast. I don't think I'd be so charitable about losing what small power
I'm making to such an extent, I'd suggest compensation might be needed.
Brian

--
--
From the sofa of Brian Gaff -

Blind user, so no pictures please!
Today is Yesterdays Tomorrow.
"misterroy" wrote in message
...
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?
ta

Thank you all.