Sun hours

[SunEagle]

Really enjoying following your solar adventures, thanks.

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

[DanKegel]

Really enjoying following your solar adventures, thanks.

[bcroe]

The first snow of the season arrived in NW ILL, half a foot of heavy wet stuff. Perfect for a snowman, not so good for solar
panels. This will test the latest snow handling experiment here.

The South facing array design isn't ideal at this time, with limited spacing between portrait mounted panel rows. And the slope
is still in summer mode, not easy to change on this design. BUT it does have gaps between rows of panels. With temps above
freezing some of the heavy snow was already trying to slide off. Note that the snow on upper panels didn't slide onto
the lower panels; it started falling through the 6" gap. With the snow depth equal to the gap size, it needed a little
encouragement to finish the trip. That is OK, the next version will have an 8" gap. One platform had a 4" gap, which did
not work well in this situation.

I got out the snow pusher and started clearing panels. Both upper and lower panels were partly clear, not a huge job. No
more pushing 10 feet of snow over 10 feet of panels. Just pull the remaining snow to the bottom of each panel and off.
When finished the snow pile in front of the array is much smaller than when all the snow landed there. Eventually I'll need
to blow it farther away, but not this time. Bruce Roe PV16D2.JPG
PV16D3.JPG
PV16D1.JPG

[bcroe]

Hard to believe, but after years the PoCo seems to have finally gotten their net metering billing together. Only 3 days this time between
when the meter was read, and the statement appeared in my mailbox. This will certainly make it easier to manage my reserve over the
winter. Too bad no one here knows how to manually read the house meter; they plug into it, and may use wireless someday.

Reserve Dec 1 is running slightly below last year, which had a huge surplus. its way above the previous year, a cold winter and I just
barely covered use. This winter I may start maintaining minimum temp in my shop electrically, this building was previously just propane.
With a better handle on reserve, maybe I'll be a little more reckless about using up all the reserve before true up 1 April. But might have
to give up bragging rights of not purchasing a KWH in years. Bruce Roe

[bcroe]

A miracle happened; the PoCo got out my monthly statement within a week of reading the meter. That had been the norm,
but after I got net metering 39 months ago, the statement would take 4 weeks and even not come at all. If this continues, it
will be a lot easier to manage my ROLLOVER energy reserve through the winter.

As the reserve nears peak, I am running about 700 KHW behind 2015, or 5%. But some 11% above 2014, probably because
of the big junk and tree clearance out of the array area. This should be much more than I need to heat the house for an
average winter; need to shunt some off to the car shop. A split mini heat pump would be good; a simple resistance unit is
more likely this year. Bruce Roe

[bcroe]

The next full scale experiment is ready for a predicted "snowy" winter. Here a 6 inch gap has been added between the upper and lower
panels. Snow will only need to slide half as far to clear a panel, and there will be only half as much snow being pushed into each pile
on the ground. That means I won't be doing so much running the snow blower to keep the pile lower than the bottom of any panels.
And pushing snow off will be a lot lighter work; possibly avoided completely on some occasions. This would work even better if the panels were turned landscape. But that would be much more difficult, and will be postponed to another phase.

Instead of removing panels, drilling new holes, then reinstalling them, I used this equipment to drill the new holes before the
panels were moved. Then it was just a matter of removing 4 bolts, sliding a panel up, and putting the bolts back. Only the upper
panels were moved.

Of course it was necessary to disconnect most of the MC4s and reroute the wires. Previously, numerous covered wires were running
between the upper and lower panels. With all nature of snow, ice, and branches falling through the gap, only 2 wires now cross it,
protected by the main aluminum supports at each side. And this was done without using any MC4 extension cords. At the same
time some sloppy earlier harness additions were cleaned up.

For safety, first a string fuse (positive) was removed, then the negative return pulled, isolating the entire 12 panel string from ground.
Then most of the rest of the MC4s were pulled to break up the circuit. Then all mechanical work could be done. Putting the string
back on line was pretty much in reverse order. Even so, a fair amount of the work was done under a full moon for safety and
to avoid loss of production. All panels appear undamaged.

One more experiment will be adding a mechanical vibrator to the back support of some panels. The idea is to try and shake the
snow off, adjusting the frequency and intensity. Bruce Roe

[bcroe]

I repaired the MC4s on the test panel; I'm one of the guys who solders things. The array is some 500' from the house, but it has
outdoor AC outlets for tools. After a good run, today is so dark and rainy, I'll be lucky to get 30 KWH. Maybe its a good day to see
just how much different orientations tend to equalize out under strong overcast. Clamp on DC ammeter....

Also there is an attempt to move some of my DIY panel stuff on to another experimenter. On Eb*y, we shall see. So far a place to
recycle PV panels hasn't been found, but this could develop into a huge problem one day in some areas. Bruce Roe

[bcroe]

Its been a couple months since the summer solstice, first experiments on panel placement
vs daily output curve. The setup should be checked perhaps every couple months through
the Dec solstice, to check loss of performance. On Aug 23 the extremely rare "clear NW
ILL day" needed for measurements came along.

Of course there never is a perfectly clear day in NW IL. A couple tiny wisp clouds did drift
by; measurements were postponed until they were well clear of the sun. I think perhaps
a single recording was influenced by an invisable bit of cloud; a few percent out of line.

This time my E and W facing curves managed to cross at exactly solar noon as they should.
The chart said solar noon was only about 30 seconds off the CST hour. The curves looked
to me, to be more like the same as those of 17 June, than different. The E and W were
added together to see how flat the total output of a dual direction array would be.

In Oct the next measurement set should demonstrate the practicality of of a single max sun hours
design. If a good compromise setting can be found for 8 months, the short and rarely clear
winter days might be ignored. For the dominant cloudy days at the end of the year, the
alignment won't matter anyway.

Recall the test output device is just a measurement of current through a shunt. The
potential mppt power will have a very similar curve. However, I had just finished the East
facing panel useful curve, when an MC4 connector burned out. My test equipment has
the MC4 latches ground off for more convenient configuration changes. This connector
apparently had started coming apart. Or maybe earlier damage had prevented them
fully mating in the first place; maybe some moisture got in there. In any case things got hot,
and oxidized, and got hotter, and failed completely. That will need replacement before
the next test run. Bruce Roe

[J.P.M.]

Huh. Fun fact: http://www.gamechangesolar.com/downloads/2-11.pdf says one of their large projects used bifacial panels.

Re water ballast: better check the water level periodically.

The sort of implied idea that bifacial panels are different from non bifacial panels with respect to wind loading and design is misleading. Either bi or mono facial panels will require the same design considerations for wind, or for that matter seismic, loadings.


As for the website, it's a bit thin on details. As such, to me anyway, it looks like the bucket design seems to use mass as the main and only way the issue of overturning moment is addressed, with static friction between the ground and the base (buckets) being the only reactive force against shear forces induced by either wind or seismic loadings. Without knowing more details, I'm not sure I could make such a system work - at least not in CA. Without some anchorage, there isn't much, if any resistance for lateral movement from either sudden events or simple and constant creep, especially on non level ground. I note most of their advert. stuff is for projects in the northeast.

[SunEagle]

Interesting. Thanks for that bit of info.

[DanKegel]

Huh. Fun fact: http://www.gamechangesolar.com/downloads/2-11.pdf says one of their large projects used bifacial panels.

Re water ballast: better check the water level periodically.

[SunEagle]

Hey. I just found a website about a company that does ground mount system (large ones) on top of former land fills. They use either a precast ballast or pour in place ballast that will also allow the racking to be aligned if the ground is not level but can be tilted for different panel aiming.

They are called GameChange Solar.

[SunEagle]

With an array 10' high, I guess footers would have to have a pretty big footprint. Bruce

Or made of very heavy material like concrete or containers filled with water.

[bcroe]

I believe I have seen some type of flat roof rack mounting that used weighted "footers" that sat on the roof surface where additional weight like sand bags could be added. I would think ballast or rock would work the same as long as it met "up lift" wind load calculations.

With an array 10' high, I guess footers would have to have a pretty big footprint. Bruce

[SunEagle]

Is there any such thing a a ballasted ground mount? Was thinking about another trial mount here. There are a dozen tons of rock
piled up here from previous foundation digs. Bruce Roe

I believe I have seen some type of flat roof rack mounting that used weighted "footers" that sat on the roof surface where additional weight like sand bags could be added. I would think ballast or rock would work the same as long as it met "up lift" wind load calculations.