Sun hours

[bcroe]

I was just thinking about the definition of SUN HOURS. Like, with my sun rise to sunset being
10:50 hours now, the total energy hitting a given panel might be equivalent to 5 hours of perfect
sun noon. So then its 5 SUN HOURS that day, location, and alignment.

Working this backwards, harvesting 110 KWH divided by 15 KW inverter maximum (clipping)
level, gives 7.33 equivalent SUN HOURS. The idea of course is to stretch the sun day by adding
panels directly facing the rising & setting sun. Comparing this to the basic sun hours could be
a multiplying factor for the panel arrangement. Probably the factor doesn't have a name? I'm
still looking for a tool to use, to predict this factor. Bruce Roe

[Ampster]

.....
Regarding DIY, I discovered long ago that most tools would pay for themselves the first
time you used them (avoiding hired labor). ........

Yes. That is my experience. I now have a garage full of tools that I can now start giving to my son in law and my nephew who sometimes provide extra labor. Double benefit.

[bcroe]

Thanks for the comprehensive answer. My take away is that your DC to AC ratio is accomplishing your goals.

Right, when combined with multiple panel orientations.

Regarding DIY, I discovered long ago that most tools would pay for themselves the first
time you used them (avoiding hired labor). Recent example, for my first PV panel
experiment I paid $1K to have a full scale backhoe dig the 10 holes. Good work, but
the heavy machinery so messed up my grass (on a 10% grade) that by spring there was
a very serious erosion problem. I paid a landscaper $2.3K to get my grass restored.
On the latest array I used my own $3.3K mini backhoe, no erosion problem, and no
BIG DAY schedule issues. Bruce Roe

[Ampster]

Thanks for the comprehensive answer. My take away is that your DC to AC ratio is accomplishing your goals.

[bcroe]

Understood. Thank you.

So that would mean on what's about your best production day your array(s) are producing something like 155 kWh from 34.95 STC kW of PV ?

If I might test your forbearance for questions a bit more: How about a SWAG for total annual output for all the installed PV you have in terms of kWh/yr. per installed STC kW ?

You could say that, yes. The way I see it, 15KW inverters produced 155KWH mid May, because
my limiting factor is the size of the inverter plant. All the commercial applications seen here
recently state the inverter AC output capacity, with a DC/AC ratio, and I am following that approach.

Not included in that statement, is the cloudy sky performance, hard to put precise numbers on. What
I see is for clear skies, 15KW output for more than 8 hours. For rather slight clouds, output remains
saturated much of the day. For clouds starting to eliminate hard shadow lines, output is 80%. In days
the sun is not seen output may run 40 to 50% of capacity. In a rain storm output is usually in the range
of 10 to 25%. Here is my daily output curve recently. Annual output depends on the weather and
upgrades, latest is 28,500 KWH.


PV15May19.png

For a 15KW system installed here at Zip 61084, 42 deg lat, never ending clouds of varying weight, I claim other
systems will not do as well as mine. My system is not optimized for the SW desert, and designs from there perform
poorly here. Arrays I have seen:

FIXED ARRAY.

Less optimum annual angle
Huge snow removal effort required more than a dozen times each winter
Limited day hours near peak output.
Output severely limited under less than optimum sun.


DUAL AXIS TRACKER: Never used on sizable arrays.

SINGLE AXIS TRACKER, E-W Scan.

The shaft on this oft used commercial setup is parallel to the ground. At 42 deg Lat
the incident angle drops output to about 0.7. This means the DC/AC ratio
must be increased accordingly, this while keeping tracker complexity.
No compensation for weaker sun at day extremes.
Good snow rejection ONLY when used with enough ground clearance.


FIXED ARRAY WITH MULTIPLE PANEL ORIENTATION, EASY summer/winter tilt change,
snow gaps, and high ground clearance. Inverters will tolerate a high DC/AC ratio
because only some of the panels are at a most favorable sun angle at any given time.

High snow rejection, most snow would clear without manual intervention shortly.
Careful selection of tilt will provide near level output under a day of best sun,
partly compensating for weakness of day extremes.
Inverters are kept at peak output most of the day under good sun.
Under medium clouds, high DC/AC ratio produces considerably more
than a tracker, perhaps double that of a fixed array.


There are harder questions to ask. I have a lot more money in 6061 aluminum, SS hardware,
concrete, wire, Rbar, and tools, than in PV panels. Adding EASY seasonal tilt change does
increase production, at considerable cost. Combining that with easy snow control adds
some more cost. I am glad to trade initial cost, for very little snow removal efforts.

On the other side, DIY efforts provide huge savings. This is partly enhanced by scaled
down DIY tools (backhoe, trencher) available when convenient, not on a preset schedule.
Small tools help avoid erosion problems. On site materials may be repurposed for new
construction. Arrays following my land (10% grade) are way simpler than attempting a
perfectly level construction.

Bruce Roe

[J.P.M.]

That is about right, not certain some of my no name panels are fully up to their label. Bruce

Understood. Thank you.

So that would mean on what's about your best production day your array(s) are producing something like 155 kWh from 34.95 STC kW of PV ?

If I might test your forbearance for questions a bit more: How about a SWAG for total annual output for all the installed PV you have in terms of kWh/yr. per installed STC kW ?

[bcroe]

So that would be 2.33*15 = 34.95 STC kW of PV ?

I'm not trying to be rude and I appreciate you don't owe me anything much less an answer, but it was supposed to be a simple question.

That is about right, not certain some of my no name panels are fully up to their label. Bruce

[J.P.M.]

I am running a 6 year old set of panels, rated 2.33 DC to AC ratio into 15KW inverter plant. It is arranged
for the dual modes of emulating tracking under best sun, and boosting output under clouds. Bruce

So that would be 2.33*15 = 34.95 STC kW of PV ?

I'm not trying to be rude and I appreciate you don't owe me anything much less an answer, but it was supposed to be a simple question.

[bcroe]

Bruce:

I forgot and I'm too lazy to root around for an answer: How many STC kW of PV do you currently have installed ?

Thanx, J.P.M.

I am running a 6 year old set of panels, rated 2.33 DC to AC ratio into 15KW inverter plant. It is arranged
for the dual modes of emulating tracking under best sun, and boosting output under clouds. Bruce

[J.P.M.]

Managed 155 KWH even with some rather minor clouding, I think a record here for May. Cutting some
trees added a bit, but there is still room to move some panels for a better combination of orientations.
Took half a year to get 2 strings exactly right, guess it could be done by 2024.

In any case 10.33 GHI/day is pretty good, is there any other arrangement (not in orbit) that can do that
at 42 deg lat? Still waiting for warmer nights to attach test points to string 12. Bruce Roe

Bruce:

I forgot and I'm too lazy to root around for an answer: How many STC kW of PV do you currently have installed ?

Thanx,

J.P.M.

[bcroe]

Managed 155 KWH even with some rather minor clouding, I think a record here for May. Cutting some
trees added a bit, but there is still room to move some panels for a better combination of orientations.
Took half a year to get 2 strings exactly right, guess it could be done by 2024.

In any case 10.33 GHI/day is pretty good, is there any other arrangement (not in orbit) that can do that
at 42 deg lat? Still waiting for warmer nights to attach test points to string 12. Bruce Roe

[bcroe]

Just like April 2018, the 15KW inverter plant today managed 151 KWH in best sun. That would be
10.07 GHI/day I believe. A clamp on meter check noted, the 2 newest strings with identical sun
differed in output by nearly 10%. That is enough for me to wonder if there is a panel section being
bypassed. I may add some taps and check it out later. If 1/3 and 2/3 tap connections are brought
over to the combiner box, I can check the voltage of each group of 4 panels in the string of 12.
Finding something, taps are moved to increase resolution of the suspect section. Later.
Bruce Roe

[bcroe]

Last night I and 100 of my neighbors attended another county meeting on zoning a 20MW solar
plant, right in the middle of AG and residential, in direct conflict with the COMPREHENSIVE PLAN
of every governing body in the area, based on a loophole in the regulations and the presence of a
major substation to the nearby Byron Nuke. The solar co brought 5 representatives for a
presentation, which I thought was vague and glanced over most details. All pictures were of
a different type system than proposed, and incomplete.

The meeting lasted 6 hours 40 minutes. There was a petition against it signed by literally half
the residents of the village and nearby area. At the end it took about 8 minutes for the 20MW
proposal to be voted down unanimously.

There are a number of smaller 4MW proposals going, it remains to be seen if this is a trend.
Bruce Roe

Update a month later. A member of the county board (who I also have worked with in LIONS)
proposed a 6 month MORATORIUM on any industrial scale solar in our rural AG setting. The
county is to prepare a whole set of guidelines (like other counties) to deal with zoning requests,
instead of the questionable arrangement that had been passed a year or so ago (proposed by
WHO?) to grease the skids. Obviously there has been a lot of behind the scenes stuff, the
moratorium passed 21 to 1. This does not mean no industrial solar ever, but it sure puts the
brakes on what was happening before.

I got to know a lot of neighbors better. Bruce Roe

[bcroe]

Solved another reoccurring problem on the back solar acre. Getting wiring trenched in has meant
renting/transporting a machine, or hiring someone. Both of those have been a hassle, and digging
by hand is less acceptable every year. I finally bought this absolute bottom price unit, which does
not even include self propulsion. The hand cranked winch I added here probably works even
better. It seems pretty rugged, and that little Honda engine works just fine. Bruce Roe

Trench2.JPG

[bcroe]

A proposal for a 20MW solar installation was not well received, in this rural,
zoned AG area. My schedule shows 10 meetings to attend, I am part of the opposition.
Bruce Roe

Last night I and 100 of my neighbors attended another county meeting on zoning a 20MW solar
plant, right in the middle of AG and residential, in direct conflict with the COMPREHENSIVE PLAN
of every governing body in the area, based on a loophole in the regulations and the presence of a
major substation to the nearby Byron Nuke. The solar co brought 5 representatives for a
presentation, which I thought was vague and glanced over most details. All pictures were of
a different type system than proposed, and incomplete.

The meeting lasted 6 hours 40 minutes. There was a petition against it signed by literally half
the residents of the village and nearby area. At the end it took about 8 minutes for the 20MW
proposal to be voted down unanimously.

There are a number of smaller 4MW proposals going, it remains to be seen if this is a trend.
Bruce Roe