Justin Richards wrote:
> One thing we could not agree on however, was my suggestion to face some E=
ast
> and some North. He ended up getting some national head honcho on the phon=
e
> wanting to bet $500 that the inverter would sense the worst case panel an=
d
> track it. I kept stating that the tracking inverter only "sees" the array=
 as
> a single power source and it will load it to achieve maximum power transf=
er.
> Both the installer and the gambler refused to accept this quoting x years
> installing etc and that it would track the worst panel.

I don't recall whether you described how your panels are wired.

Keep in mind that with series-connected panels, the total voltage is the su=
m
of the individual panel voltages, but the current through the string is
limited to the current of the least-illuminated panel. This may be what the
vendor was referring to.

Panels (or strings of panels) wired in parallel need to have a blocking dio=
de
on each panel (or string); otherwise the better-illuminated panels will dum=
p
their current into the less well-illuminated panels. With blocking diodes,
MPPT gets a bit tricky, because there may be multiple local maxima in the
power vs. voltage curve of the system as the higher-voltage panels get load=
ed
down to the point where lower-voltage panels begin conducting. It depends o=
n
how well the panels are matched, both in terms of manufacture and illuminat=
ion.
In the worst case, only the highest-voltage panel will be supplying all of =
the
current.

-- Dave Tweed
--=20
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