Sun hours

[DanS26]

I made a snow pusher pretty much like that one. This winter will be testing the gap between upper
and lower panels, to see if the snow will drop through after being pushed only half as far.

They look pretty close to the ground at one end. Here those would be blocked by snow before
long. As it is I still have to run the snow blower in front later in the winter. I think you made
them perfectly straight and level. The ones I built follow the hill, which means they are not level
from end to end. But they are straight, because I used a laser to align things. Bruce Roe

After much trial and error I have determined this method is the best and fastest way to remove snow from my arrays.

1. Push the top 2/3 of the top row off the back. Yes, I'm pushing the snow upward and backwards.
2. Now pull the 1/3 of top row down over the next two rows.
3. Third pass to clean off the bottom row.

Using my new and improved snow broom assembly, it is fast and efficient.

[bcroe]

[ATTACH=CONFIG]8100[/ATTACH] I clean the snow off with this.

I made a snow pusher pretty much like that one. This winter will be testing the gap between upper
and lower panels, to see if the snow will drop through after being pushed only half as far.

They look pretty close to the ground at one end. Here those would be blocked by snow before
long. As it is I still have to run the snow blower in front later in the winter. I think you made
them perfectly straight and level. The ones I built follow the hill, which means they are not level
from end to end. But they are straight, because I used a laser to align things. Bruce Roe

[harleydee]

sun

Nice snow sweeper. Thanks for the pictures.

I would be intrest in this as I got my first quote out of 7 so far that mentioned sun hours

[SunEagle]

I clean the snow off with this.

Nice snow sweeper. Thanks for the pictures.

[DanS26]

IMG_0671.JPG

I clean the snow off with this.

[DanS26]

Dan that 72 panel array sounds huge. Have you posted any pictures of it?

IMG_0087.JPG

Front array 36 Kyocera 235 Black panels and the rear array 36 Kyocera 245 Blue panels.

[SunEagle]

I have two arrays of 36 panels each. Each array has 3 strings of 12 panels each. Each array is configured into 4 rows of 9 panels wide.

I am now on the third wiring method. Initially the wiring method was top to bottom.....the thinking being that snow would slide to bottom rows thus exposing the the top rows to produce at full power. Since I pull the snow it was not really needed since all rows are exposed by my effort.

Next wiring effort was to wire the strings so that all the string lengths were equal to the combiner boxes. Thus the voltage loss on each string length would be equal. Not sure if it made any difference but it sounded electrically elegant.

Then I got the bright idea that if I wired the strings left to right in blocks I would follow the shading across the arrays as the sun rose. Thus maximizing production in the mornings. So I have stuck with this method.

Now Bruce you come along with your lightning strike voltage loop theory.......hmmmmmm.

Dan that 72 panel array sounds huge. Have you posted any pictures of it?

[DanS26]

I just want to hear any wisdom on the subject. I have a 65' radio tower 200' away (300' from
the house), but it hasn't been hit by lightning yet. I have the same, 6 strings of 12 panels facing
south. And wired in blocks so shade will only affect an end. However there are more strings
facing east and west. Bruce Roe

Only a matter of time until that tower is struck. You are wise to be concerned about voltage gradients affecting your solar system.

I too am concerned about lightning since my location has been struck multiple times and lost much electronics and appliances. That was over ten years ago when my electrical system was your basic 1950's farm electrical system......two wire system with multiple neutral ground bonding all over the place and multiple unconnected ground rods. It all came to a head when my wife would be shocked by touching the washing machine and standing on the concrete basement floor in bare feet. The shock was in time with the electric fence charger.

Then I got serious. Completely rewired the farm to 2011 NEC specs. Modern three or four wire system as required and unbonded the neutrals except in the main disconnect. Had some close strikes since then but no damage.

My arrays are ~250 ft from the house and each has a ground ring around the array. Each ring has four rods and bonded to each other. Probably overkill since each array has ten 3" galvanized steel posts encased in concrete 4 feet deep.

An EGC connects the combiner boxes at the arrays to the inverters at the house. Of course that is for personal protection and probably would do little to protect from lightning. I believe the theory is that the resistance in the length of the EGC would make a strike go to ground fast at the array or the house before jumping above ground and damaging equipment.

Lastly I rely on multiple SPD's all over the place, even one on the pole transformer, under the meter, in all sub panels and combiners, both inverters and all detached structures. 18 at last count and does not include the SPD's at point of use.

[inetdog]

I just want to hear any wisdom on the subject. I have a 65' radio tower 200' away (300' from
the house), but it hasn't been hit by lightning yet. I have the same, 6 strings of 12 panels facing
south. And wired in blocks so shade will only affect an end. However there are more strings
facing east and west. Bruce Roe

For the overall leads exiting the array at the same point, the wiring method in between should not have a large effect on the induced voltage in the loop of wire that connects the panels within the array.
Just out of superstition I would look at the arrangement that
1. Had the lowest possible total length of wire, but
2. Had the + and - leads running next to each other whenever possible if there are any long runs.

[bcroe]

I have two arrays of 36 panels each. Each array has 3 strings of 12 panels each.
I am now on the third wiring method.

I got the bright idea that if I wired the strings left to right in blocks I would follow the shading across the arrays as the sun rose. Thus maximizing production in the mornings. So I have stuck with this method.

I just want to hear any wisdom on the subject. I have a 65' radio tower 200' away (300' from
the house), but it hasn't been hit by lightning yet. I have the same, 6 strings of 12 panels facing
south. And wired in blocks so shade will only affect an end. However there are more strings
facing east and west. Bruce Roe

[DanS26]

I was wondering about considerations for the order of wiring a string of PV panels?
I understand perhaps stringing a row, dropping to a second row, and stringing back
to the beginning. Or stringing every other panel in a single row, then stringing back
on the other panels to the beginning.

I have strings of 12 panels here, on 2 ground mount platforms of 2 high and 3 across.
The installer connected one platform in a rectangle, 3 across the top and then down
to 3 back across the bottom. The other platform is a zig zag; bottom to top, across
and then back to bottom, across and then back to top. Perhaps this was to get both
feed points as far east as possible. Some strings are fed from the east, but a string
with the feed between platforms is wired the same.

i was thinking about voltage induced in the big loops by a near lightening strike. If
my 2 platforms were wired exactly the same, the voltage induced in the wiring of
the two platforms would add up and be seen at the inverter. If the panel wires
were crossed on the second platform, clockwise current in one would be
counter clockwise current in the other. Voltages induced in the two platform
loops would be reversed and tend to cancel.

This came up when I put a "snow drop" gap between upper and lower rows of
panels. The rectangular pattern had 2 wires crossing the snow gap, which I
can protect from ice & snow by tying them under the vertical supports. The zig
zag pattern had 4 wires, 2 with no nearby supports. My thought is to eliminate
the zig zag and the 2 extra wires crossing the gap. Bruce Roe

I have two arrays of 36 panels each. Each array has 3 strings of 12 panels each. Each array is configured into 4 rows of 9 panels wide.

I am now on the third wiring method. Initially the wiring method was top to bottom.....the thinking being that snow would slide to bottom rows thus exposing the the top rows to produce at full power. Since I pull the snow it was not really needed since all rows are exposed by my effort.

Next wiring effort was to wire the strings so that all the string lengths were equal to the combiner boxes. Thus the voltage loss on each string length would be equal. Not sure if it made any difference but it sounded electrically elegant.

Then I got the bright idea that if I wired the strings left to right in blocks I would follow the shading across the arrays as the sun rose. Thus maximizing production in the mornings. So I have stuck with this method.

Now Bruce you come along with your lightning strike voltage loop theory.......hmmmmmm.

[bcroe]

Panel wiring order

I was wondering about considerations for the order of wiring a string of PV panels?
I understand perhaps stringing a row, dropping to a second row, and stringing back
to the beginning. Or stringing every other panel in a single row, then stringing back
on the other panels to the beginning.

I have strings of 12 panels here, on 2 ground mount platforms of 2 high and 3 across.
The installer connected one platform in a rectangle, 3 across the top and then down
to 3 back across the bottom. The other platform is a zig zag; bottom to top, across
and then back to bottom, across and then back to top. Perhaps this was to get both
feed points as far east as possible. Some strings are fed from the east, but a string
with the feed between platforms is wired the same.

i was thinking about voltage induced in the big loops by a near lightening strike. If
my 2 platforms were wired exactly the same, the voltage induced in the wiring of
the two platforms would add up and be seen at the inverter. If the panel wires
were crossed on the second platform, clockwise current in one would be
counter clockwise current in the other. Voltages induced in the two platform
loops would be reversed and tend to cancel.

This came up when I put a "snow drop" gap between upper and lower rows of
panels. The rectangular pattern had 2 wires crossing the snow gap, which I
can protect from ice & snow by tying them under the vertical supports. The zig
zag pattern had 4 wires, 2 with no nearby supports. My thought is to eliminate
the zig zag and the 2 extra wires crossing the gap. Bruce Roe

[bcroe]

The electric bill came; here is the latest energy reserve buildup for winter.
Despite even more clouds
than last year, I'm well above 2014. The heat pump gets most of the credit; usage here is quite small
(due to earlier conservation efforts) except when the heat goes on. Most of what the PV generates
is going to reserve, but that will change soon. If the winter is actually the predicted warmer, there
might be a big surplus. Bruce Roe

An update; energy reserve for winter heat is peaking about now, 2000 KWH or 16% higher than last
year. The unseasonably warm weather has kept generation in the black for some extra days.

Energy generated since annual reset 1 April is almost exactly the same as last year, 19,600 KWH.
That despite more clouds, probably aided by removal of some shade. However the weather and the
new heat pump have reduced consumption in the interval. Its interesting how much things can
vary from year to year. If we have the predicted mild winter, I will be doing some electric heat
in another building. Bruce Roe

[inetdog]

The draw is only around 2A once they get started, not the 12A on the plate. Getting them
driving a panel platform remains in the future. Bruce Roe

Most likely the 12A is when working against the maximum rated force.

[bcroe]

Pv snow gap & linear activator

Its getting late, but I may yet manage to get my south facing panels vertical for this snow season. The
24 braces to hold them are done; the issue is how to raise & lower each platform having two braces.

I ordered a couple linear actuators with a 52 inch stroke (about enough) and a 5000 lb capacity (overkill).
They run on 24 VDC, should be able to fine control them with adjustable voltage.

But they haven't arrived yet, so the mechanical design is still in doubt. Worst case the whole thing will
fall on me. IREA tour this Sat. Bruce Roe

Today was the setup for another snow experiment. I have panels 2 high, meaning snow must
slide a long way to be cleared off 2 panels, and the pile of snow gets pretty big while clearing and
at the bottom. On one support of 6 panels I moved the upper panels 4" higher and the lower panels
2" lower for a 6" gap between them. Snow will only need to slide half as far, in half the quantity
before falling through the gap.

On the next support of 6 panels, I just moved the upper for a gap of 4". This winter will be the
test: does the gap work and how big should it be? Did it in the afternoon, had just enough sun
time left to make sure all were still working properly.

I did get the linear activators unpacked and they run; take about 10 minutes at 18V to run 52
inches. I suppose that means 180 volt minutes for 52 inches: 7.5 minutes at 24V or 15 min at
12V. The draw is only around 2A once they get started, not the 12A on the plate. Getting them
driving a panel platform remains in the future. Bruce Roe