Solar panels and partial shade

[Anthony]

Hi,

I would like to install solar panels on my roof but am concerned about
the partial shade created by the large tree to the north-west of my
house (Note: I'm in the southern hemisphere - Australia). I have read
previously that amorphous panels can handle partial shading, but that
other types of panels may develop "hot spots" which cause them to
degrade if they are frequently used in partial shade conditions. Can
anyone confirm or deny this ?

I imagine as more and more households install solar panels, shading
from trees will become an increasingly important problem. Has anyone
developed a system of sparse panel cells which cover a large area, for
a reasonable cost by having cells separated by large gaps. I think this
configuration would work reasonably well in my case as there is a good
amount of sunlight which shines on the north-west facing roof and it
gets many hours of dapled sunlight each day. The tree's canopy is not
very dense, so there are lots of gaps for the sun to shine through, but
the sunlight patches move around all day.

If I were to buy small solar cells (e.g. 5cmx5cm) and wire them up
myself, is there any electronics I can use to efficiently combine the
outputs to work in dapled light, or should I just wire them all up in
parallel connected with diodes to prevent reverse current ?

Thanks,
Anthony.

[Bill Kaszeta / Photovoltaic Resources]

The basic rule is that the output current of a PV module is established by the
series cell with the lowest illumination on it.

Amorphous panels usually have long/thin cells, so the shadow of a leaf
or similar covers only a fraction of the cell, resulting in less impact than
a shadow on a square or round cell.

Modern PV modules will not fail due to hot spots because the modules
include bypass diodes that limit the possible reverse voltage across
a shaded cell.
Bill Kaszeta
Photovoltaic Resources Int'l
Tempe Arizona USA
bi...@pvri-removethis.biz

[Dave]

As indicated by the previous response there is a definate advantage with
Amorphous panels (such as Uni Solar) if they are partially shaded by a leaf
etc.

However in dapled light or on a cloudy day , any advantage may be minimal-
I'd be interested to hear from anyone having both panels in such conditions!

OzDave
www.rpc.com.au