# The sun is getting stronger



## begreen (Feb 13, 2015)

And power generation is getting stronger and longer. We are gaining 2 minutes of daylight a day now. With full sun the panels are even beating the heat pump. The 12:00 red load is when my wife was taking a shower. The 6KW spike is when the heat pump briefly came on. Normally in this weather it's running at about 2KW.


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## jebatty (Feb 13, 2015)

For a brief period in early afternoon (morning was cloudy) when the sky cleared, my system was putting out nominal rated 6.5 kw. Can't wait for a couple of clear, cold days to beef up the cloudy first half of February.


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## begreen (Feb 13, 2015)

We need the sun to get higher in the sky for good long day gains. We are on the north slope of the hill and shading clips us now for all but a few hours.


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## peakbagger (Feb 14, 2015)

My house has a small mountain to the east. In the winter I can see the horizon brightening up but before it rises its behind that darn mountain and its a couple of hours before the sun makes it around the mountain. We have had a cloudy stretch so I missed which day the sun went over the mountain but its now up and over so I get a lot more sun. I don't get a lot of generation off the morning sun but every bit helps.


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## Where2 (Feb 14, 2015)

I've had some nice, smooth, well rounded PV output curves the last two days. No complaints here, other than I'd love to have another 4.4kW of PV online to over-produce at times like these. I miss these smooth output curves in summer when the summer rains come almost every day.


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## Seasoned Oak (Feb 14, 2015)

Ill say its getting stronger , i forgot to open the door to the sunporch the other day and killed my tropical lime tree. And those trees can take a lot of heat. Something over 100 degrees.


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## begreen (Feb 14, 2015)

Got a 4500W peak for about 15 minutes today before the sun ducked behind a passing cloud. This coming week is supposed to be sunny so I am hoping to see some flatter curves. Can't wait until the sun is high enough to get over the trees.


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## jatoxico (Feb 14, 2015)

Oh yeah some of the ice in my driveway melted a little a couple hours ago before it refroze, much better.


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## JustWood (Feb 14, 2015)

WTF is sun ????
Now that the lake is froze over we should get some cloud free days. We get lake effect everything. Snow, rain,clouds, water spouts,fog etc.


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## jebatty (Feb 14, 2015)

Hard to believe, but actually had very clear weather, sunrise to sunset today, with just some very thin clouds in the western sky in the later afternoon. Best production of the year so far. My system is rated at 6.5 kw nominal, 6.76 kw maximum. Would really enjoy a string of days like this, but not likely to happen, snow in the forecast tomorrow.


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## ewdudley (Feb 15, 2015)

JustWood said:


> We get lake effect everything. Snow, rain,clouds, water spouts,fog etc.


I friend was telling about a rainy weekend at a summer retreat on the Tug Hill plateau east of Lake Ontario.  He was commenting to the proprietor how nice it was that the sun came out in time for a beautiful sunset, and it looked like the weather was changing for the better. The proprietor pointed out that it was still raining and the sun was just sneaking in sideways under the clouds, a common phenomenon at that location in the evening.


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## Seasoned Oak (Feb 15, 2015)

8 degrees for a high today, passive solar room was 80 in bright sun today. HAd to bleed off some heat into the house. Hard to believe im getting solar gain when its 8 Deg outside


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## mass_burner (Feb 15, 2015)

Don't want to get off subject, but this large amount of snow is making me wonder how solar panels fare with 4+ ft of snow on them.


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## peakbagger (Feb 15, 2015)

The panels will hold up to a lot of uniform load, the racking not so much. If someone went cheap on the roof supports or skipped the roof joists they may find out where the installer saved a few bucks or did shortcuts.


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## mass_burner (Feb 16, 2015)

peakbagger said:


> The panels will hold up to a lot of uniform load, the racking not so much. If someone went cheap on the roof supports or skipped the roof joists they may find out where the installer saved a few bucks or did shortcuts.


Can you go up and take the snow off them, or are snow melters available?


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## jebatty (Feb 16, 2015)

I had to install on ground mounts because too much shade on the house roof, but very happy I did. Easy to pull the snow off with a floor broom with extension handle.


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## Where2 (Feb 16, 2015)

peakbagger said:


> The panels will hold up to a lot of uniform load, the racking not so much.


Racking and panels will both withstand plenty of load if the system designer pulls out the checkbook and pays a structural engineer. Care to calculate the down force and uplift loads applicable from a 3 second gust of 170mph (that's my local residential structure wind load criteria thanks to Hurricane Andrew)

There's a reason my array is constructed with 3 rails supporting each panel (rather than 2). My permit submittal package to the local building department included a 5 page mathematical analysis that resembles a calculus proof with structural PE stamps. I considered it a fun little exercise coming up with different rack designs to get me in the ballpark before I ever sent my structural engineer a detailed design and said "Will this work?".


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## Vic99 (Feb 16, 2015)

Here in Lowell we are the snowiest city this YTD at. 111 inches.  A hundred year event for sure.  https://www.facebook.com/MILLCITYWE...0.1424140246./915247438526296/?type=1&theater

Twelve of my twenty five panels are uncovered, a few partly covered and the rest under a few feet.  Despite strengthening the roof at the engineers request during installation, I still don't want to take any chances with snow weight. Was careful with a roof rake just to skim some snow off dormer PV panels, but still buried under two-three feet.  Too high up to do a better job and wouldn't want to risk scratching panels.

If you are talking a few inches, sun melts most snow off panels within a day.  If you get several inches + and the roof pitch isn't steep, maybe not.  On my 28 degree pitch, no worries.  On my 58 degree, as I said above.

Solar gain in winter is not very much anyway . . . . Sure panels max out with cold temps and fresh snow albedo, but day lengths are so short, doesn't matter that much.  I have the added problem of trees.  Nine months a year no problem, but for about three in winter, sun is low enough that they affect my production, even without leaves.  Fortunately I have microinverters so a whole string isn't killed.


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## begreen (Feb 16, 2015)

Snow is not the issue at this time of year for us. Trees are. We get a solid 3 hrs of production right now if it's sunny. Trees block the rest. We'll see when they stop being such an issue. It looks like the sun will be above a couple large firs soon.


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## jebatty (Feb 17, 2015)

To show the impact of shading on my system, here is a comparison of Dec 20, 2013, the shortest day of the year, and Feb 14, 2015. I am virtually free of shading by Feb 14. Except that there may have been a few very wispy clouds, both days had clear sky. The differences: first, sun zenith on Dec 20 was 19.67* and on Feb 14 was 29.8*; second, the morning dips in both graphs show the effect of shading; third, both graphs show just a bit of shading in the very late afternoon. Production above 500 watts was about 6 hours on Dec 20 and about 8 hours on Feb 14.

Kwh production on Feb 14 of 38 kwh was 220% of the 17 kwh production on Dec 20. My all time high kwh production so far has been 48 kwh, 280% of the production on Dec 20 and 126% of the production on Feb 14.


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## peakbagger (Feb 17, 2015)

I have a standard plastic roof rake that I use to rake my panels. As long as its plastic you will not scratch standard glass panels. Solar panels are made with tempered glass.  It takes a lot of abuse to damage a panel as long as you make sure to keep anything metallic away from the panel.

Yesterday was a clear cold day with steady wind, I generated about as much power as I do on a typical sunny day. The inverter was clipped for about 2 hours. Summer generation is more consistent as lately only 1 in three days is sunny but the bonus from increased sun intensity from the snow reflection and cold temps really does make a difference.

Unfortunately my 2nd story roof panels are out until we have some warm sunny days to melt them off.


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## georgepds (Feb 17, 2015)

For a somewhat longer view.. here is the 2 year perfomance of my 4.5 kw system ( is was 2.5kw  until ~6/13). You can see the energy/day rise and fall with the  season


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## begreen (Feb 17, 2015)

jebatty said:


> To show the impact of shading on my system, here is a comparison of Dec 20, 2013, the shortest day of the year, and Feb 14, 2015. I am virtually free of shading by Feb 14. Except that there may have been a few very wispy clouds, both days had clear sky. The differences: first, sun zenith on Dec 20 was 19.67* and on Feb 14 was 29.8*; second, the morning dips in both graphs show the effect of shading; third, both graphs show just a bit of shading in the very late afternoon. Production above 500 watts was about 6 hours on Dec 20 and about 8 hours on Feb 14.
> 
> Kwh production on Feb 14 of 38 kwh was 220% of the 17 kwh production on Dec 20. My all time high kwh production so far has been 48 kwh, 280% of the production on Dec 20 and 126% of the production on Feb 14.



Nice. We have a lot more shading issues until the sun gets high enough to get over the tall trees.


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## jebatty (Feb 23, 2015)

Clear, below 0F temps, and fabulous PV production. My  inverters are rated at 250 watts, 260 watts maximum, and yesterday for 2 hours output was over 250 watts/panel, peaking at 6680-6690 watts system output. Total for the day was 43 kwh. Cold and clear weather to continue.


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## peakbagger (Feb 23, 2015)

On the first day in about a month with above freezing conditions and some melting, I got my extension ladder out and scraped off my shallow angle roof array to get it back on line. it was fairly warm out so I didn't set any records for production but its nice to get it contributing again. Tuesday is supposed to be sunny but real cold and windy so I expect I will see some good production. This array is on a oversized inverter so it doesn't clip so I can watch what it peaks out at. The angle isn't optimum for this time of year but I still managed to peak at its rated load with 40 degree temps. Now if the snow could back off for a bit I might be able to keep it clear.


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## begreen (Feb 23, 2015)

10 days later we are already making progress with shading as the sun rises higher over some trees.


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## jebatty (Feb 24, 2015)

The cold, sunny February is turning into a great month for PV. Only 35 kwh to go to meet Feb target kwh.


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## begreen (Feb 24, 2015)

Decent!


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## valuman (Feb 24, 2015)

jebatty said:


> The cold, sunny February is turning into a great month for PV. Only 35 kwh to go to meet Feb target kwh.
> View attachment 154452


I'm curious about your system monitoring. Is it from the inverter manufacturer, or a third party setup?


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## jebatty (Feb 27, 2015)

Aurora, the micro manufacturer, collects data from the array via its Concentrated Data Device (CDD), which also sends real time screen data to my computer. Aurora then provides access to a wealth of data collected by it, including such things as reports individually on the performance of each microinverter. All of the data may also be downloaded from Aurora in CSV files for use by spreadsheet, graphing, or other programs and for analysis, and the website for my plant also may be programmed to provide automatic downloads by email attachments.


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