There is a weather station set up not too far from the OP's zip code that reports hourly GHI data. Because the locations are different and the correlation between GHI and energy generation is not particularly straightforward, there are limitations to this approach. The PVOutput.org comparison is probably a better and more user friendly comparison. However, for what its worth, here is a plot of the daily GHI vs the daily energy generated, from 11/1 to today. Over time, if the correlation drifts in ways that can't be explained seasonally or by panel tilt, it could be an indication of a change in performance in either the weather station, or the PV array.
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Do you mean the CSI EBPP calculator? According to the documentation, it is a repackaged version of PVWatts that allows specific equipment to be selected. The text that matters:
When I set the current version of PVWatts to the CSI default derate (16.3%) and match the inverter effeciency to what is used by CSI, the results come out almost identically. The new version of PVWatts uses a lower default derate (14%), which they have indicated is a better fit to real world data the results have been compared against.While this calculator relies on industry-standard assumptions, and is driven by NREL’s PV Watts v. 2 calculator, there may be other factors that affect the output of your PV System.
The CSI equipment database is comprehensive, better than what comes packaged by NREL in SAM. Maybe there is a way to update it...Leave a comment:
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here's a source that break down by month
Here's a source that break down by month and by specific equipment, shading etc. Its the CA state calculator.Leave a comment:
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The arrangement of 2 strings of 12 is likely; 3 strings of 8 is possible. If you have have a combiner
box, you can observe the arrangement, and make measurements there. Your FRONIUS has the facility
to fuse strings and DC disconnect internally. If you see 4 or 6 wires approx 10 gauge coming into it,
those are from your strings. The wires might be labeled, or can be traced to the + and - terminals
visible on the left when the lower door is opened, and the cover removed.
The criteria for clamp on comparisons, is the strings must be identical and in good sun. I'd measure
the + wires here. My FRONIUS 6.0 has bus bars below the + and - inputs, with single heavy wires
going to a remote combiner. Bruce RoeLeave a comment:
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The typical connection for this system would be two parallel strings of 12 panels in series. That inverter appears to only have a single MPPT, so if all of the panels do not see uniform radiation, it may handle it less efficiently than inverters with separate MPPT for each string.Leave a comment:
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Honestly, I don't know. I have a single FRONIUSs IG Plus 6.0-1UNI with 24 250W Solarworld panels....I'm not sure the number of "strings" or other details. I don't really have any easy way to test anything on the 2nd story roof, but I have easy access to the inverter. What is the typical hookup for this equipment? Would I benefit from asking any specific questions regarding strings etc?
The most suspicious detail at this point is how low my "peak" output has been since the first week on November; only 1 day with a peak over 4kW (just barely) since Nov 19th. I'll have to keep an eye on the production numbers as it gets sunny...Leave a comment:
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solar14.JPG
This is my output for 92656 on a 6.5 KW system.
You can see how weeks 2 and 3 under performed weeks 1 and 4.
Weather made a big difference in the weekly output.
watt.JPG
The only thing that jumps out at me is for these dates, you had sunny conditions and averaged about 15 KwH's per day. For these same dates, I also had sunny conditions, but averaged 28 KwH's per day. A considerable difference.
watts2.JPGLeave a comment:
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Days with very good sun are best for troubleshooting. I use a clamp on DC ammeter to compare
identical strings, which should have nearly identical output. A bad string shows up immediately;
finding the exact fault takes longer. How are your panels connected? Bruce RoeLeave a comment:
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Im in San Diego and have a 7.6kw AC system that generated 699kw hrs for this past month of November. Last year I generated only 643kw hrs. I think the PV watt estimate was 738kw hrs. Had a lot of cloudy days here on the coast so I'm not surprised on the output. I overproduced from April through Sept of this year so I guess I can't complain. My first year generating I was 238kw hrs under the PVwatt estimate, we'll see how the second year add's up when April 15 of 2015 comes around. So far so good.Leave a comment:
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By looking at the graph of your system vs. the 7kW in your area, I don't see any difference to worry about.....
My 7.1kW SW 245 with 23 deg tilt only produced 701kWh during Nov 2014. I bet lots smaller system outperform me but I think I'm on the track comparing with few system in my area.Leave a comment:
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You need more time to see what your "normals" should be. After about 6 months, if my 7.755 kW DC did not produce between 32-45 kWh on a sunny winter day, i would be worried. On rainy days, I'll get maybe 5-10 kWh. Likewise on cloudy days, if I do not see a 7-7.5 kW instantaneous peak value, particularly if I get almost exactly 1/3 or 2/3 of that value, I know I have a faulty string since I have 3 strings. You can see my PV Output here:
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I found a 7kW system in a neighboring city (6 mi away) that tracks quite well with my efficiency...Makes me feel more like bad conditions than bad equipment. It's just hard to swallow 488 kWh for a month from a 6kW system in Southern California!
The system is called "Miles Away" if you are familiar with picking comparisons in pvoutput and want to see the data yourself.
For those who asked, I'm in Southern California, zipcode 93021
TNTArray2014.12.05compare.jpgLeave a comment:
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