HI Sky,
I sure hope the data doesn't take a few more decades!
jay
peltz power
On Sep 12, 2008, at 8:26 PM, Sky Sims wrote:
August makes a good point. There really isn't much solid info on the
topic of dissimilar orientations.
In the experiments I've conducted using different orientations and
tilts
on the same strings the production almost exactly matches the average
projected production across the orientations and tilt.
In regard to using mix matched modules in parallel strings I haven't
seen any noticeable difference in performance either. Of course this
is
an advanced technique and requires an awareness of string voltages and
amperages in order to avoid excessive power clipping. The biggest
problem with using different manufacturers panels with each other
appears to be more bureaucratically driven rather than performance
based.
What I mean to say is that because the manufacturers are unlikely to
provide a written endorsement allowing you to use their panels in the
same string with someone else's, you may have trouble with a
bureaucrat
requiring that endorsement.
There is a lot of rumor floating around about how important it is to
use
the same panels and the same orientations and tilts. And I agree it is
important, but there may be circumstances that over ride those rules.
I've had many systems where for esthetic or available space reasons a
panel or 2 in a string of modules was put at an entirely different
tilt
and orientation. I've played quite a bit with it and haven't noticed
any
reduction in performance that would warrant the elimination of what
might be 10 to 30% of the string or perhaps even the entire string.
However with inverters like enphase coming to market it becomes easier
to ensure that every panel in a string is at the same orientation and
tilt.
I always recommend the best tilt and orientation possible but sites
and
circumstances coupled with other details specific to the site
sometimes
force us to go with less than optimal string placement practices. A
healthy well rounded understanding is important and I don't feel that
the industry has done enough to create that understanding yet. Best
practices have certainly been promulgated but the context has not been
fully explained or explored yet.
Inverter reps and installation reps and panel reps have made many many
representations based on their best guesses and in some cases what
they
have seen first hand. We the implementers are the guinea pigs, get
used
to it. Thankfully the kinks are getting worked out.
Perhaps in another couple decades when things settle down we'll have
properly documented studies of mix matched panels, orientations and
tilts. Of course by then things will be so completely different that
it
wont matter any way.
My 2 cents,
Sky Sims
Ecological Systems
http://www.ecologicalsystems.biz
220 County Road 522
Manalapan, NJ 07726
732-462-3858 toll free)866-759-7652 fax)732-462-3962
-
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