[RE-wrenches] voltage drop from online data?
Phil Schneider
phil at CEsolar.com
Tue Mar 17 10:02:09 PDT 2009
Wrenches,
I was looking at some of our web-based monitored systems this morning to
check in on some performance numbers, and this question came up.
I can see a measured DC array voltage on-line (as measured at the inverter),
and I have cell temp information so I can calculate the theoretical
temp-adjusted Vmp (based on module nameplate). When I look at the
difference between theoretical and measured, it seems that this can largely
be attributed to voltage drop in the DC wiring between array and inverter.
Am I missing other factors that would lead to this difference between
theoretical and measured? Power-point tracking errors, Vmp tolerance and
module mis-match, cell temp accuracy are a couple that come to mind. I
realize that field measurements at different points in the system would give
me more information from a scientific standpoint, but in this age of remote
monitoring I make sure we understand it's utility.
Phil Schneider
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