Q:Solar panels optimal configuration

[sam ford]

hi
i have a system of 2 24v panels (110watts each) in series for a 48v
inverter
i was fooling with these one day with a current meter and noticed that
covering a small area of one panel would reduce the output of the total
by sometimes as much as 80% depending on where you covered one and not
so much by total the area covered.there didn't seem to be a lnear
relationship.in cloudy conditions this may or may not cause
irregularities in the output???
can you get more out of 2 panels in parrallel.
can you get more ot of 4 to 6 smaller panels with their total equaling
the watts of 2 big ones?
the distance to the inverter is not that great so my wiring losses
aren't great at 24v.
thanks
dick

 

[Scott Willing]

hi
i have a system of 2 24v panels (110watts each) in series for a 48v
inverter
i was fooling with these one day with a current meter and noticed that
covering a small area of one panel would reduce the output of the total
by sometimes as much as 80% depending on where you covered one and not
so much by total the area covered.there didn't seem to be a lnear
relationship.

The cells in each panel are in series. The current produced by a cell
depends on how much light falls on it. There can only be one current
running through a series string by definition. Therefore if you shade
one cell you affect the output of the entire panel, and the output of
the series string of panels. Indeed, without shunt diodes, you can
shut off the current by completely shading a single cell.

Some cell technologies incorporate integral shunt diodes. External
shunt diodes could be placed across panels, but this is more to
protect the shaded cell(s) than anything.

in cloudy conditions this may or may not cause
irregularities in the output???

Yeah, but shading from clouds doesn't have the sort of distinct shadow
edges cast by your hand, a tree or a building close to the panels, so
the whole panel surface is subjected to similar illumination levels
anyway.

can you get more out of 2 panels in parrallel.
can you get more ot of 4 to 6 smaller panels with their total equaling
the watts of 2 big ones?

No no no, don't go there. Dropping to a lower array voltage to
mitigate shadowing issues is the wrong idea.

Unless there are close objects that cast distinct shadows on portions
of the panels - you, for example - <g> I would put this issue out of
your mind. If shadows are cast at all times of the day, your panels
need to migrate to a better location.

-=s

 

[sam ford]

thanks scott
one advantage for me to drop to a paralleled 24v system is that i can put 1
cell on a tall spruce tree and get more hours of morning sun and the other on
a pole/mast i'll have to build to get more hours of the afternoon sun.
i can use what i have now for this.
i'm guessing that the total for the day would be greater???(depends on cloudy
times etc. but i would get more total hours a day from what i now can get in
the middle of my wooded site)
otherwise i have to fork out big bucks for 2 more 110watt 24v panels to stay
at 48v and to remount to this new location which create a bit of a problem
because of their extra size/weight although the extra juice could be used.
thanks