PV December Record

[jebatty]

Dec 27, 2017, set a one day record for December in my system: 36 kWh for the day. And the sun is only at 19 degrees over the horizon. The one day record for a single day during any year was 89 kWh. This single Dec day was 40% of the all-time daily record and 62% of the highest daily average for any month, which occurs in July. A bit amazing the effect on winter PV of clear, cold, and dry winter air with ground cover snow-bounce in a northern latitude of 46.9 degrees. Bursting my own bubble: Dec is the lowest kWh production month of the year.

 

[peakbagger]

Out of curiosity do your inverters have enough head room to prevent clipping on these cold winter days?.

I realize that economics are better to undersize inverters on grid tied systems even though they clip on cold winter days but its still painfull to see the flat line especially in Dec with short days and in my area a lot more cloudy days. No subsitute for hours of daylight whihc are pretty darn slim this time of year near 45 degrees latitude

One of my arrays is buried in snow on second floor roof and I expect will be off line until the next warm up.

 

[jebatty]

do your inverters have enough head room to prevent clipping on these cold winter days?.

Maximum peak kW usually occur during the mid March to late April time period. My panels are rated at 265W for 26 panels and 270W for 20 panels. The micros are rated at 250W, 260W maximum output, and 265W maximum usable. During the peak kW days, total output will hit 11,900W to about 12,200W, or about 260-265W/panel. There are brief periods when clipping occurs on one or more panels, but only once did I see a straight line output for the whole system for a period of time. Output for the system was greater than 265W/panel in that instance. I wouldn't normally notice one or a few panels clipping.

 

[peakbagger]

I forgot you have micro inverters, Clipping is more of an issue with string inverters as the voltage and wattage swings due to panel temp is higher with a string.

A blue sunny day with some puffy clouds with snow on the ground can really confuse things when the cloud edge effect combines with snow reflection to crank the insolation well over standard.

I hope to get exposure to some large commercial installations, one old and one new this year so I can see how the big systems deal with it. One should end up with a large AC coupled storage battery and the other may use a DC coupled storage battery. The code now allows up to 1500 peak volt strings on commercial systems so I expect the equipment is going to be a lot different.

 

[Brian26]

You should look into setting up your panels on the pvoutput website. The amount of data is awesome. I even have the actual temperature that my inverter is running at logged in there.

I had a peak yesterday of 4.292 on my 5.4 KW system. I am in the negative though the last few weeks as I have had family staying over and usage has been high. I do have around 1000kwh in credits so am still ahead.

Here is my 12/29 data from pvoutput.

https://pvoutput.org/intraday.jsp?id=60553&sid=53905&dt=20171229