East Array + South Array + West Array ?

[inetdog]

Regarding use of two (or more) channels, keep in mind that as long as there are no partial shading issues or different string lengths, sub arrays with different orientations can be put on a single MPPT controller, since the Vmp for the two arrays will stay relatively constant over the daylight cycle while the Imp changes drastically.

[NEOH]

Regarding use of two (or more) channels, keep in mind that as long as there are no partial shading issues or different string lengths, sub arrays with different orientations can be put on a single MPPT controller, since the Vmp for the two arrays will stay relatively constant over the daylight cycle while the Imp changes drastically.

But, in this case ...
a) Imp = 8.69 amps and
b) Max amps per each Sunny Boy channel = 10 amps
therefore, I doubt that two parallel strings can be combined into one SB channel

Which is why the owner's original idea was 3 independent strings ...

South Array #1 = 10 x 275w panels on MPPT Channel A
South Array #2 = 10 x 275w panels on MPPT Channel B
South Array #3 = 10 x 275w panels on MPPT Channel C

Which is an "OK" configuration, until I informed the owner that the Inverter will clip the 6,600 Watts down to only 5,000 Watts from 10am until 2pm - Ouch !
And then I started this thread for asking for better, higher yield, array configurations ...

[inetdog]

But, in this case ...
a) Imp = 8.69 amps and
b) Max amps per each Sunny Boy channel = 10 amps
therefore, I doubt that two parallel strings can be combined into one SB channel

Which is why the owner's original idea was 3 independent strings ...

South Array #1 = 10 x 275w panels on MPPT Channel A
South Array #2 = 10 x 275w panels on MPPT Channel B
South Array #3 = 10 x 275w panels on MPPT Channel C

Which is an "OK" configuration, until I informed the owner that the Inverter will clip the 6,600 Watts down to only 5,000 Watts from 10am until 2pm - Ouch !
And then I started this thread for asking for better, higher yield, array configurations ...

And that is why the configuration of the South Array to one channel and both East and West Arrays to the second channel makes sense. The East and West arrays will peak at different times and the sum of their outputs will never be much, if any, greater than the output of either one of them at max. But if you have three input channels to the inverter, there is no reason not to put one sub-array on each channel.

[bcroe]

No concerns that wood can shrink or warp?
After I clean the snow off of my panels, I drive past with my JD Tractor with a front mounted 2 stage snow blower.
Shoots snow about 8' away and makes a perfect path in front panels for the next day

The treated wood was a quick experiment expected to last at least 5 years. Now after 6 it does not appear to
be seriously affected. On paper are plans to upgrade all the panels to tilting, 6061 aluminum/stainless/concrete
supports. My HVAC plant efficiency has improved so much, I may not put all strings back.

Its easier to run the snow blower there with 40 inch panel ground clearance. I had to upgrade to a 4WD
tractor to deal with these grades. Bruce Roe

NSsnow.jpg

[solarix]

Too bad your friend did not just buy a bigger inverter. SMA's prices came down awhile ago and the 7.7kw size now costs very little more than the smaller ones. We've adopted the policy of just selling almost everyone the big 7.7kW one as it future proofs them allowing more panels to be added on. Most people use more power as time goes on, more power when they start using solar, and more power when they buy an EV. We do your three orientation strategy all the time to max out a single 7.7kW inverter so as not to have to do a service upgrade. You can put up to 28 panels (8.8kW) in a single orientation, or up to 37 panels (11.5kW) in a dual orientation. In your friend's situation, I would put 12 panels south, and 9 panels on each wing at 45deg.

[NEOH]

And that is why the configuration of the South Array to one channel and both East and West Arrays to the second channel makes sense. The East and West arrays will peak at different times and the sum of their outputs will never be much, if any, greater than the output of either one of them at max. But if you have three input channels to the inverter, there is no reason not to put one sub-array on each channel.

What if the two arrays cause two local maxima peaks in the Power Curve?
What if the MPPT logic locks on, and tracks, the LOWER Power Peak?

The title of the thread does state "East, South & West".
And BCROE does implement a true due-East & due-West configuration.
A true East-West design has very poor winter production and needs many more panels.

The optimum design here must use all 3 Channels:
A) South-East (8) + South (11) + South (11) or
B) South (11) + South (11) + South-West (8) or
C) South-East (9) + South (12) + South-West (9) or
D) South-East (10) + South (10) + South-West (10) = three identical Racks of 2 high x 5 wide Landscape each

Surprisingly, the difference in Total Yearly kWhr production is only 5% from best ( A & B ) to worst ( D ).

[bcroe]

What if the two arrays cause two local maxima peaks in the Power Curve?
What if the MPPT logic locks on, and tracks, the LOWER Power Peak?

The title of the thread does state "East, South & West".
And BCROE does implement a true due-East & due-West configuration.
A true East-West design has very poor winter production and needs many more panels.

The optimum design here must use all 3 Channels:
A) South-East (8) + South (11) + South (11) or
B) South (11) + South (11) + South-West (8) or
C) South-East (9) + South (12) + South-West (9) or
D) South-East (10) + South (10) + South-West (10) = three identical Racks of 2 high x 5 wide Landscape each

Surprisingly, the difference in Total Yearly kWhr production is only 5% from best ( A & B ) to worst ( D ).

You are mixing up the power curve over the day, with the instantaneous best
voltage/current operating point (MPPT). They are not in conflict. Panels operate
at near constant voltage over varying sun, for a given temp. So here, all strings
wired in parallel, the best operating voltage for the least irradiated string will be
practically the same as the best operating voltage for the best irradiated string,
which is the one the inverter will be taking its cue from mostly. That point is not
very critical, the low output strings will be near their best power even at a slightly
shifted voltage.

If your inverter has multiple inputs, each with their own MPPT input, there is
no problem between inputs, providing that each can handle the inverter
capacity.

I think any array set up for good summer operation, is going to do badly in winter
unless the angle can be changed seasonably. Here during the shortest days it
is so cloudy (once went 27 days without seeing the sun), rearranging the array
does not buy much, your results may vary. But a high DC/AC ratio does bring
in some energy anyway, if snow is kept clear. Bruce Roe

[NEOH]

30 panels x 275 watts STC = 8,250 watts total
8,250 watts x 80% = 6,600 Watts ( typical hot sunny day )
The Sunny Boy 5.0-US is rated at 5,000 watts AC output.

Initially, I thought that CLIPPING of the 6,600 PV Watts down to 5,000 Watts by the Inverter was a significant issue.
In this case, clipping by the inverter is NOT as big an issue. as I had thought.

Therefore, the BEST Design for his system is ...

10 panels per channel x 3 channels all pointed due SOUTH

a) South Array #1 on Channel #1 = 10 panels
b) South Array #2 on Channel #2 = 10 panels
c) South Array #3 on Channel #3 = 10 panels

Turning any array away from due South, towards SE or SW actually decreases the Yearly kWhr production.

[Mike90250]

.......

Turning any array away from due South, towards SE or SW actually decreases the Yearly kWhr production.

But will time of use billing be coming along anytime ? Then a west biased array helps offset that afternoon/evening cost

[NEOH]

But will time of use billing be coming along anytime ? Then a west biased array helps offset that afternoon/evening cost

Electric company does offer a Residential Time-of-Use plan = Off Peak starts 8:00pm until 8:00am M-F & all weekend
I do not know of anybody that has switched to that plan.

[NEOH]

Too bad your friend did not just buy a bigger inverter. SMA's prices came down awhile ago and the 7.7kw size now costs very little more than the smaller ones. We've adopted the policy of just selling almost everyone the big 7.7kW one as it future proofs them allowing more panels to be added on. Most people use more power as time goes on, more power when they start using solar, and more power when they buy an EV. We do your three orientation strategy all the time to max out a single 7.7kW inverter so as not to have to do a service upgrade. You can put up to 28 panels (8.8kW) in a single orientation, or up to 37 panels (11.5kW) in a dual orientation. In your friend's situation, I would put 12 panels south, and 9 panels on each wing at 45deg.

The 7.7 kW inverter costs more than a 5 kW inverter and the bigger Inverter generates more amps ...

More amps = bigger wire = more $'s
More amps = bigger Circuit Breakers = more $'s
More amps = bigger AC Disconnect = more $'s
Bigger wire = bigger conduit = more $'s
More amps = bigger electrical panel in his barn = more $'s ( cannot de-rate Main CB )
Bigger panel in barn = bigger underground wire to the barn = more $'s

The 7.7 kW Inverter only increases yearly kWhr production by 4% - 5%.

All three (3) PV Arrays, of 10 panels each, pointing due South appears to be the BEST Layout for maximum Yearly kWhr production

I maximized the "Yearly kWhr Production" value, what parameter do you maximize to select "South-East + South + South-West" as better?
Is it based on a Time-of-Use plan = changing price of electricity ?

[J.P.M.]

But will time of use billing be coming along anytime ? Then a west biased array helps offset that afternoon/evening cost

That also depends to some extent on the distribution of clear skies as f(time of day). For example, a climate dominated by days of lots of sun before noon and/or little afternoon sun can skew an array orientation optimized for highest annual possible array revenue in NEM applications as much as a lopsided T.O.U. rate schedule.

Looks like for NEOH, his schedule will have little impact on optimal array orientation.

[Markyrocks69]

The 7.7 kW inverter costs more than a 5 kW inverter and the bigger Inverter generates more amps ...

More amps = bigger wire = more $'s
More amps = bigger Circuit Breakers = more $'s
More amps = bigger AC Disconnect = more $'s
Bigger wire = bigger conduit = more $'s
More amps = bigger electrical panel in his barn = more $'s ( cannot de-rate Main CB )
Bigger panel in barn = bigger underground wire to the barn = more $'s

The 7.7 kW Inverter only increases yearly kWhr production by 4% - 5%.

All three (3) PV Arrays, of 10 panels each, pointing due South appears to be the BEST Layout for maximum Yearly kWhr production

I maximized the "Yearly kWhr Production" value, what parameter do you maximize to select "South-East + South + South-West" as better?
Is it based on a Time-of-Use plan = changing price of electricity ?

Majority of these items would allow future expansion for pennies compared to the big picture. I'd personally want to oversize the wires anyways. Really not much money difference between 30-40amp breakers.... why would you need a bigger panel in the barn over 10 amps? If you only have a 100 amp panel in there that's basically full your probably screwed without a tap either way....

[nwdiver]

I maximized the "Yearly kWhr Production" value, what parameter do you maximize to select "South-East + South + South-West" as better?
Is it based on a Time-of-Use plan = changing price of electricity ?

I had a ground mount in the spring that was somewhat similar but larger. We were limited to ~15kW due to export constraints so we installed 22.77kW on (2) 7.7kW SMA inverters. 11 345w panels per channel. One aspect I didn't fully consider is that facing the array west or east decreases the angle south => acts to increase summer generation at the cost of winter generation. However there's a ~27kW system I also helped with next door and the 22.77kW system is producing more energy at 5pm than the 27kW due to the West facing panels.

If you expect net metering to be around for awhile then 100% South. If you want to increase self-consumption then maybe angle a couple slightly west.

Array.jpg


Screen Shot 2019-08-08 at 4.20.03 PM.png

[bcroe]

The 7.7 kW inverter costs more than a 5 kW inverter and the bigger Inverter generates more amps ...

More amps = bigger wire = more $'s
More amps = bigger Circuit Breakers = more $'s
More amps = bigger AC Disconnect = more $'s
Bigger wire = bigger conduit = more $'s
More amps = bigger electrical panel in his barn = more $'s ( cannot de-rate Main CB )
Bigger panel in barn = bigger underground wire to the barn = more $'s

The 7.7 kW Inverter only increases yearly kWhr production by 4% - 5%.

All three (3) PV Arrays, of 10 panels each, pointing due South appears to be the BEST Layout for maximum Yearly kWhr production

I maximized the "Yearly kWhr Production" value, what parameter do you maximize to select "South-East + South + South-West" as better?
Is it based on a Time-of-Use plan = changing price of electricity ?

Use what works best for you. There are a few reasons that is different from what is
best for me. One is, my DC:AC ratio is much higher than yours, to make power under
clouds. Another is, many days here I have seen a clear sky at -20F causing panels
facing the sun to produce close to their rating. So I do not want them to all be facing
the sun at the same time. Bruce Roe