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Matt, You're right, it is 4.5% different. I'm not sure which buttons on the calculator I used to get 1.1%. Kent Osterberg m...@solar-energy-solutions.com wrote: Kent, Can you help me understand the 1.1%? I had figured over 4% and allowed that 1-2% may be voltage drop (though it is quite literally 12' of 10 awg between the last enphase and the meter).In a state with a semi-active SREC market all our systems are installed with a revenue grade meter. I see similar variations on almost every string inverter installed. I don't think this detracts from potential Enphase value, I just don't see that this is an area where the Enphase product stands out. MattMatt, The Enphase and revenue grade meter are in disagreement by less than 1.1% in the system you are describing - that's good agreement! According to the Enphase white paper, the wiring loss in the Enphase cabling between the first and 9th inverter is 0.6%. That only applies to the last inverter and the average loss for the system will be less, but it shows that the ac wiring loss is a significant part of the discrepancy. Also, even the revenue grade meter is not perfect - typically ±0.25% when new. Kent Osterberg Blue Mountain Solar m...@solar-energy-solutions.com wrote:Mark, We have nine Trina modules on our roof with Enphase. Enphase says the array has produced 2,680 kWh to date. The revenue grade meter 12 feet away says 2,564. Until I hear otherwise I am reluctant to consider Enphase reporting precise. It seems to be similar to what I would expect from a string inverter. I would be delighted to hear more anecdotes confirming your observations. Regards, Matt Matthew Partymiller Solar Energy Solutions LLC (859) 312-7456 m...@solar-energy-solutions.comFolks, Has anyone used Enphase monitoring data to get warranty replacement on new modules with sub par yield? I have several interesting questions stemming from access to Enphase module level monitoring data. Looking at data from a larger site (80 modules) with no shading issues, instant power production indicates a high degree of uniformity in panel power (Sharp NU-U240F1 and D380) easily within 1%. So what can we now say about the precision and accuracy of this monitoring data? It seems the old school thinking for string inverters was all the monitors were 5% off and reporting 5% more power than actual. Based on the data that I am looking at, it seems the microinverter meters must be fairly precise and possibly fairly accurate as well. Uniformity of module performance must also be fairly high. In any case, this data clearly shows a single module that is not performing as well as it's cohorts. For power levels above 50% of STC, it averages 9% less power than all other modules in the system. So off to Sharp for a warranty replacement? Yes, but, what if I am 5% low on the report from my inverter meter and 5% lower on my power from this one module? What if the module gets back to Sharp and they say it is within spec, now the costs are all mine? Interestingly enough, access to this monitoring data is making more work for me as an installer. With a string inverter, I would monitor power production readings monthly and be happy so long as yields were higher than what I projected when I designed and bid the job. Pretty much fire and forget. Now I am spending time on evaluating this data and doing the work to change out the module under warranty and so forth. I am going to end up putting in quite a few hours into this for what: to recapture 10% of 1/80 of total system yield….0.0013%. I am not complaining, just musing over this interesting evolution. Mark Frye Berkeley Solar Electric Systems 303 Redbud Way Nevada City, CA 95959 (530) 401-8024 www.berkeleysolar.com_______________________________________________ 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.orgMatthew Partymiller Solar Energy Solutions LLC (859) 312-7456 m...@solar-energy-solutions.com _______________________________________________ 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 |
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