Great article on performance calculations in the previous issue of Solar Pro, pp24. I made a quick & dirty spreadsheet that we use to plug in measured values on site to give us a ballpark during checkups.
-Glenn Burt -----Original Message----- From: re-wrenches-boun...@lists.re-wrenches.org [mailto:re-wrenches-boun...@lists.re-wrenches.org] On Behalf Of Phil Schneider Sent: Tuesday, March 17, 2009 1:02 PM To: RE-wrenches Subject: [RE-wrenches] voltage drop from online data? 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 _______________________________________________ List sponsored by Home Power magazine List Address: RE-wrenches@lists.re-wrenches.org Options & settings: http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org List-Archive: http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org List rules & etiquette: www.re-wrenches.org/etiquette.htm Check out participant bios: www.members.re-wrenches.org _______________________________________________ List sponsored by Home Power magazine List Address: RE-wrenches@lists.re-wrenches.org Options & settings: http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org List-Archive: http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org List rules & etiquette: www.re-wrenches.org/etiquette.htm Check out participant bios: www.members.re-wrenches.org
