Sun hours

[SunEagle]

For the winter of 2016/2017, generation so far has been some 17% higher than cloudy last winter. The peak reserve
from Nov is down about 5% from the previous year, but well above the year before the heat pump was helping. Last
winter left me with a HUGE KWH surplus at April true up, so this year electric heat is being used to the max.

The propane furnace has not run at all this season; resistance heat was working pretty hard when we touched 15
degrees below zero. So far the remaining reserve is running below the excessive reserve curve, but still well above
the break even curve 2 years ago. Bruce Roe

Bruce.

Hopefully that ice storm from Jupiter doesn't hurt any of your system equipment. Good luck my friend. It looks like the winter storms are bad this year.

[bcroe]

For the winter of 2016/2017, generation so far has been some 17% higher than cloudy last winter. The peak reserve
from Nov is down about 5% from the previous year, but well above the year before the heat pump was helping. Last
winter left me with a HUGE KWH surplus at April true up, so this year electric heat is being used to the max.

The propane furnace has not run at all this season; resistance heat was working pretty hard when we touched 15
degrees below zero. So far the remaining reserve is running below the excessive reserve curve, but still well above
the break even curve 2 years ago. Bruce Roe

[bcroe]

Why re-invent the wheel.
The data you are looking for, using your method, will be dependant on your type of lanels.
The feds uses power per square meter, http://www.nrel.gov/gis/solar.html, kwm/m2/day.

How much actual power is then less than calculated for your area based on your equipment/installation.

PVWatts should tell you all you need to know, right?

I tried using standardized (SW desert) designs, and PVWatts years ago. I got to watch my inverters doing very little. A PVWatt
simulation was useless here because I couldn't control all the input variables, and it didn't understand the peculiarities of my
situation. But if you think you can give me an optimized NW IL design, I'll certainly try to evaluate it. Bruce Roe

[dennis461]

Why re-invent the wheel.
The data you are looking for, using your method, will be dependant on your type of lanels.
The feds uses power per square meter, http://www.nrel.gov/gis/solar.html, kwm/m2/day.

How much actual power is then less than calculated for your area based on your equipment/installation.


PVWatts should tell you all you need to know, right?

[bcroe]

Another test today, at least an inch of pretty wet snow followed by temps slightly above freezing. 96% of the snow had already slid
off the poorly (summer) elevated South facing panels. It seemed pretty clear to me, if snow from the upper panels had had to slide down
the lower panels to clear, there would have been FAR more snow for me to clear. But it fell through the snow gaps.

It was pretty overcast, but panels still work best with no sunlight obstructions. I spent like 7 minutes to get everything 100% clear. A
peek at the inverters revealed 5.5KW output, pretty good considering the sun was invisible; well worth the effort. Bruce Roe

[bcroe]

Holiday PV Report

Winter is really here in NW IL, the high today was 0 deg F. We have had several snow storms, the last 2 extended some 36
hours. The first morning it was very overcast, with not enough power to even light off the PV inverters. With more snow
coming I'm not cleaning the PV panels yet. I'm thinking this will be the first time in 40 months that output is 0 KWH. But then
the the sun brightened, the inverters started, and I made 3 KWH. The perfect record of SOME energy collected every day is
maintained. Same thing on the storm ending this morning, Saturday made 7 KWH.

This morning maybe 5" of very cold, light snow covered the south facing panels. One tap and it fell off the E-W panels. I went
after the S panels with a double acting steam engine stroke, push the snow off the top going up, pull it off the bottom going down.
The cold snow wasn't sticky, it just dropped through the 6" panel gap easily. 72 panels cleared in 25 minutes is certainly a speed
record here, and some of the time only using one hand. Past winters without snow gaps have taken 90 minutes.

With 3 days of decent sun coming up, the panels are delivering. I didn't check the voltage rise, but the sun cleared all trees by
noon and PV ran at the peak capability of 15KW. Even with 2 large and a couple smaller resistance heaters running in the
house, more power is generated than consumed (while the sun is high). Just look at that meter reverse arrow blinking!

Below zero, there are several big rooms I just leave the inefficient incandescent lights turned on in continuously, and they do
an EFFICIENT job of helping keep the inside in the 71 to 73 degree range.

Monday promises to be quite sunny, so as about the shortest day of the year, I should make one last power curve measurement
on the test panels. Then there will be a complete half year set of curves to contemplate for the rest of winter. Perhaps, leading to
some drastic changes. There are 3 more trees back there not likely to survive 2017. 2 years ago they were trimmed, but they
just grew right back. No coming back this time, and I can't claim these trees were in the fence line. I'm getting more
dispassionate about this. Bruce Roe

[bcroe]

i thought PVOutput had input limits. How do you get around that on those high production days?

I don't do anything. A quick look under efficiency shows a 0.050 KW system generating 5.387KWH (108 sun hours), so I guess they
don't have limits. Next one down is about 20 sun hours, then they get back to reality. In theory a tracker could about match me. Bruce

[DanS26]

i thought PVOutput had input limits. How do you get around that on those high production days?

[bcroe]

I look for systems around the Midwest that are 15kW or greater and do some long time frame comparisons with my system. My system is Steamboat Landing Solar #128 of 25,503.

A couple of years ago a moderator here, I believe his name was "russ" contended that most people do not report correctly on PVOutput, mainly over report. I disagreed and so I'm always on the lookout for systems that do not conform to the norm or their stats and ratios are abnormal.

Sometimes in the summer inverters here are essentially pegged for 10 hours (9.8 sun hours best) and I do a comparisons. There
were a few listings with impossible numbers (can the sun shine 200 hours a day?). Don't know if they are still there. Bruce Roe

[DanS26]

I look for systems around the Midwest that are 15kW or greater and do some long time frame comparisons with my system. My system is Steamboat Landing Solar #128 of 25,503.

A couple of years ago a moderator here, I believe his name was "russ" contended that most people do not report correctly on PVOutput, mainly over report. I disagreed and so I'm always on the lookout for systems that do not conform to the norm or their stats and ratios are abnormal.

[bcroe]

Bruce, liked your snow pics. Has not reached southern Indiana yet, but our day will come.

Quick question.....your PVOutput.org site "SUN HOURS" indicates a 60 panel array at 15,000 watts.....from the pics your arrays are much larger? I count 72 south facing panels and 40 east/west panels. I'm confused since it really messes with your efficiency ratings.

DANS26, Yes it DOES mess with my efficiency ratings. Your counting is pretty good, it may change again, and the panels
aren't all the same size. The rest of the plant is fixed at 15KW, the peak I can get to the meter is 14.7.

Those numbers are the original design before it changed. Since its now quite different from a "classic SW desert" design,
dealing with NW IL conditions, with panels that can never all receive direct sun at the same time, just what is it? I would
say panels are the cheapest part of the system and its very good at maximizing the plant use for this area; some would say
its a terribly inefficient use of PV panels. The numbers listed let the efficiency be calculated in a way more consistent with
the design intent and conditions here; the KWH are accurate.

I didn't know anyone actually looked at my PVOutput. Sometimes I see a system around my latitude with more inverter
but less panels than me and wonder how they compare. If its cloudy or the sun is poor at mid day I will collect more energy;
if its sunny all day I will collect less than the other system. Bruce Roe

[DanS26]

Bruce, liked your snow pics. Has not reached southern Indiana yet, but our day will come.

Quick question.....your PVOutput.org site "SUN HOURS" indicates a 60 panel array at 15,000 watts.....from the pics your arrays are much larger? I count 72 south facing panels and 40 east/west panels. I'm confused since it really messes with your efficiency ratings.

[DanKegel]

Just be honest and say you miss the nice white stuff.

no lie! taking train to minneapolis for xmas, will get my fill then.

[bcroe]

If those are vertically oriented panels in your last pic, on the left, what kind of production are you getting on sunny days? It looks like you would get quite a bit of reflection off the snow.

Of course those panels are near vertical and facing the eastern rising sun. Mounted on the other side are mirror image panels
facing the setting sun. Reflection of the sun off the snow does help. When the array is reconstructed (using the same panels),
the tilt will be much simpler to change seasonably. The panels will be landscape mounted with 8" gaps. The orientation
arrangement is still under consideration.

Severe overcast that day severely limited production, but the dispersed light pretty much put all panels of any orientation to work.
5 to 20% was about it, but it would be half that without the extra panels. At least the plant still had something to do, it all adds up.

Next time might be a little lighter snow, below melting temps. In the past 90 minutes were needed to clear the panels; need to
measure any time savings. This time certainly reduced the muscle required, and the amount of snow blowing of piled up snow.
Bruce Roe

[littleharbor]

If those are vertically oriented panels in your last pic, on the left, what kind of production are you getting on sunny days? It looks like you would get quite a bit of reflection off the snow.