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. Matt > Matt, > > 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.com >> >> >> >>> Folks, >>> >>> 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.org > > Matthew 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
