East Array + South Array + West Array ?

[NEOH]

I am helping with the design of a Ground Mount PV system.
My friend bought a whole pallet of 275 Watt PV Panels = Qty 30.

From the PV Label ...
Voc = 38.7 volts
Isc = 9.17 amps
Vmp = 31.7 volts
Imp = 8.69 amps

And he bought an SMA 5000 watt US 240 Volt AC Grid Tie Inverter with 3 independent MPPT channels
Each channel has a 480 Volt max for MPPT, and 600 volt absolute max.
So, the first calculation we did was this ...
480 volts / 38.7 volts Voc = 12 Panels max in the Southern facing array!

Next, we calculated this ...
East Array = 9 panels x 275 Watts = 2,475 watts x 80% = 1,980 watts (net)
South Array = 12 panels x 275 Watts = 3,330 watts x 80% = 2,640 watts (net)
West Array = 9 panels x 275 Watts = 2,475 watts x 80% = 1,980 watts (net)

Total Watts of all 30 Panels = 1,980 + 2,640 + 1,980 = 6,600 Watts which is greater than 5,000 watts

So, the question is ...
"How do we calculate the ANGLE for the East & West array 'wings' with respect to the larger South Array"
We realize that for every 15 degrees, the East Array will peak 1 hour earlier and
the West array will peak 1 hour later.

Rotate the East and West arrays back 15 degrees ( 1 hour ), then at Solar Noon ...
East Array = sin(75) x 1,980 = 1,912
South Array = 2,640 watts
West Array = sin(75) x 1,980 watts = 1,912
Total watts is too high 6,464 = 1,912 + 2,640 + 1,912

Rotate the East and West arrays back 30 degrees ( 2 hours ), then at Solar Noon ...
East Array = sin(60) x 1,980 = 1,714
South Array = 2,640 watts
West Array = sin(60) x 1,980 watts = 1,714
Total watts is too high 6,068 = 1,714 + 2,640 + 1,714

Rotate the East and West arrays back 45 Degrees ( 3 hours ), then at Solar Noon ...
East Array = sin(45) x 1,980 = 1,400
South Array = 2,640 watts
West Array = sin(45) x 1,980 watts = 1,400
Total watts (input) is "OK" at 5,440 = 1,400 + 2,640 + 1,400

I am not sure we should rotate the East & West Arrays back much more, since the morning and evening sun is lower at 9am & 3pm

At 9:00AM total watts is ...
East Array = sin(90) x 1,980 = 1,980
South Array = sin(45) x 2,640 = 1,866
West Array = sin(0) x 1,980 watts = 0
Total watts from 9:00AM is 3,846 = 1,980 + 1,866 + 0

At 3:00PM total watts is ...
East Array = sin(0) x 1,980 watts = 0
South Array = sin(45) x 2,640 = 1,866
West Array = sin(90) x 1,980 = 1,980
Total watts from 9:00AM is 3,846 = 0 + 1,866 + 1,980

So, from 9:00am until 3:00pm ...
6 Hours x 4,500 Watts (avg) = 27 kWhr every sunny summer day?

Is there a better way to use all 30 PV Panels with this SMA 5kW Inverter?

[J.P.M.]

Please help me out and describe what you are trying to accomplish. What's your desired end result ?

It appears you are trying to do a PV application but are ignorant of how to go about it or what's available to help with your task.

My guess is you will need a lot more education before you can pull off whatever it is you have in mind.

Start with : " Solar Power Your Home for Dummies" and then get familiar with PVWatts.

You can get some help here but it'll go a lot faster and better for you, and you'll waste a lot less of others' time if you put some time and effort into understanding the basics. From what you write it's pretty obvious to me you have a lot to learn.

Welcome back to the neighborhood and the forum of few(er) illusions.

[bcroe]

There is a lot to be considered here, every situation will be different. The main
issues here at 42 deg lat were getting the most energy through a limited size
inverter plant, maximizing collection under clouds, and minimizing the labor to
keep the array cleared of snow. Here you see 3 single test panels set up to
answer your sort of question. These were tested at varied angles and curves
plotted. The big array is facing east, on its back side are panels facing west,
a south facing array is outside the picture.

I will come back with some curves, what is your latitude and snow situation?
Bruce Roe

Test3dir.jpg

[NEOH]

Please help me out and describe what you are trying to accomplish. What's your desired end result ?

It appears you are trying to do a PV application but are ignorant of how to go about it or what's available to help with your task.

My guess is you will need a lot more education before you can pull off whatever it is you have in mind.

Start with : " Solar Power Your Home for Dummies" and then get familiar with PVWatts.

You can get some help here but it'll go a lot faster and better for you, and you'll waste a lot less of others' time if you put some time and effort into understanding the basics. From what you write it's pretty obvious to me you have a lot to learn.

Welcome back to the neighborhood and the forum of few(er) illusions.

It would be better for you, if you learned some manners.
I clearly know more than the basics and that is why my friend asked me for help.
This is NOT your standard configuration.

Do you not understand the simple question ...
"... Is there a better way to use all 30 PV Panels with this SMA 5kW Inverter? ..."

Reply, if and only if, you have you have some applicable knowledge.

[NEOH]

There is a lot to be considered here, every situation will be different. The main
issues here at 42 deg lat were getting the most energy through a limited size
inverter plant, maximizing collection under clouds, and minimizing the labor to
keep the array cleared of snow. Here you see 3 single test panels set up to
answer your sort of question. These were tested at varied angles and curves
plotted. The big array is facing east, on its back side are panels facing west,
a south facing array is outside the picture.

I will come back with some curves, what is your latitude and snow situation?
Bruce Roe

BCROE,

Thank you, for the reply
40 degrees North Latitude
This is a Ground Mount, so snow can be ( will be ? ) removed, as needed.

The other option that we are considering...

12 panels SOUTH on the "A" MPPT Channel input
12 panels SOUTH on the "B" MPPT Channel input
0 panels on the "C" MPPT Channel input
This wastes 8 of the purchased PV Panels.
11 panels x 275 Watts x 80% = approx 2,500 watts on each MPPT channel input.
I need to run the math on this configuration

After looking at you photo, I realized that we could do ...
12 panels facing EAST on the "A" MPPT Channel input
12 panels facing WEST on the "B" MPPT Channel input
0 panels on the "C" MPPT Channel input
Wasting 6 panels.
I need to run the math on this configuration

There appears to be many options ...
None of which are your "Standard Configuration"

I want to maximize the Watt-Hours produce for my friends system, using what he bought / owns.

[J.P.M.]

Reply, if and only if, you have you have some applicable knowledge.

I believe I have more applicable knowledge with respect to your situation than you are probably aware of or are capable of understanding or absorbing, but I won't be replying further to this thread.

Good luck in your future endeavors.

[bcroe]

In the ideal situation your panels will collect the most energy facing south, 180 deg. But
here the unclouded part of the day can be earlier hours, leaving poor output mid day. Often
clouds will drop output, but I have partly compensated by using a very high DC/AC setup.
Clouds do not care so much what direction the panels face, but all facing south would waste
output (and overload the string inverters). So the experiment is to keep the inverters busy
for a lot more hours per day but not overloaded. The 2013 attempt managed to produce this
curve, inverters running full power for 8 hours, as opposed to just mid day.


NScurJn17.jpg


That result was not really optimized, esp relative to snow, so the test panels
were set up in 2016. A look at the position of the rising and setting sun showed
it to be average about straight E-W, more to the north in summer, more to the
south in winter. The tests were with straight E-W panels as close enough to
quickly reach full power in summer, without huge loss of winter production.
This will be impacted by latitude, and by the degree of larger DC/AC.

The next curve shows the 3 test panel relative output over a sunny day. The tilt
here was 61 deg from flat. Other angles were tried, to get a near flat a curve over
the day. Note the instantaneous sum of the E and W panels (1 and 3) is so close
to flat, hardly any south facing input is needed to bring up the middle, at least for
this month.


PVm17Jn16.jpg


The conclusion was that for a high DC/AC ratio (previously chosen to
compensate for clouds) at this latitude, I could collect the most energy with
most panels facing E-W, and a lesser number of S facing panels. The same
simple string inverters were shared by all panels. The curves may not be as
good in winter, but those months are so cloudy it is less important.

As for snow there is a sticky on exactly how I handle that. The last array design
is optimized for production in warmer months and for snow rejection in that
season. This with tilt changed twice a year, very easy to do. What little snow
sticks will soon be melted by the first good sun, or is very easily removed. Bruce Roe


24Rear.JPG

[NEOH]

In the ideal situation your panels will collect the most energy facing south, 180 deg. But
here the unclouded part of the day can be earlier hours, leaving poor output mid day. Often
clouds will drop output, but I have partly compensated by using a very high DC/AC setup.
Clouds do not care so much what direction the panels face, but all facing south would waste
output (and overload the string inverters). So the experiment is to keep the inverters busy
for a lot more hours per day but not overloaded. The 2013 attempt managed to produce this
curve, inverters running full power for 8 hours, as opposed to just mid day.


That result was not really optimized, esp relative to snow, so the test panels
were set up in 2016. A look at the position of the rising and setting sun showed
it to be average about straight E-W, more to the north in summer, more to the
south in winter. The tests were with straight E-W panels as close enough to
quickly reach full power in summer, without huge loss of winter production.
This will be impacted by latitude, and by the degree of larger DC/AC.

The next curve shows the 3 test panel relative output over a sunny day. The tilt
here was 61 deg from flat. Other angles were tried, to get a near flat a curve over
the day. Note the instantaneous sum of the E and W panels (1 and 3) is so close
to flat, hardly any south facing input is needed to bring up the middle, at least for
this month.



The conclusion was that for a high DC/AC ratio (previously chosen to
compensate for clouds) at this latitude, I could collect the most energy with
most panels facing E-W, and a lesser number of S facing panels. The same
simple string inverters were shared by all panels. The curves may not be as
good in winter, but those months are so cloudy it is less important.

As for snow there is a sticky on exactly how I handle that. The last array design
is optimized for production in warmer months and for snow rejection in that
season. This with tilt changed twice a year, very easy to do. What little snow
sticks will soon be melted by the first good sun, or is very easily removed. Bruce Roe

BCROE,
Thank You for the graphs.
We are trying to maximize the Yearly kWhrs produced using 30 x 275W PV Panels and one 5 KW Inverter.

"... Multiple Arrays, pointed in multiple directions ..." <= Yes that is exactly what I was describing in message #1.

In your Sine Wave Graph ...
Your sine wave #1 is my proposed South-West Rack with 9 panels
Your sine wave #2 is my proposed South Rack with 12 panels
Your sine wave #3 is my proposed South-East Rack with 9 panels
You used two (2) sine waves ( East & West only ), while I propose using three (3) sine waves
Adding up all three (3) of my sine waves should produce nearly constant Watts Output from 9AM until 3PM, without any clipping


Owner's original idea
================
South Array #1 = 10 panels on MPPT Channel A
South Array #2 = 10 panels on MPPT Channel B
South Array #3 = 10 panels on MPPT Channel C
It is an "OK" configuration but the Inverter will be clipping the 6,600 Watts down to only 5,000 Watts from 10am until 2pm = LOW Yield !
Assuming ...
4 hours at 100% = 4 x 5,000 = 20.0 kw ( He lost a whopping 6,600 whrs = 1,600 x 4 due to clipping ! )
2 hours at 70% = 2 x 4,620 = 9.24 kw
2 hours at 50% = 2 x 3,300 = 6.60 kw
Estimate Daily Total = 36 kwhr


My idea ( per message #1 )
=====================
South-East Array ... 9 panels on MPPT Channel A = 1,980 watts x 6.4 hours = 12.6 kwhr
South Array ...........12 panels on MPPT Channel B = 2,640 watts x 6.4 hours = 16.9 kwhr
South-West Array ... 9 panels on MPPT Channel C = 1,980 watts x 6.4 hours = 12.6 kwhr
Where 6.4 Solar hours = 4 x 100% + 2 x 70% + 2 x 50% ( same as above )
Estimated DailyTotal = 42 kwhr = 12.6 + 16.9 + 12.6 <<< This prevents the loss of the 6,600 watts due to clipping !
This design barely exceeds the MAX Watts of the Inverter, which maximizes the yield from the 30 Solar Panels
Also, this design is better than above, for days that are just sunny in the morning, or just sunny in the evening
I call it "Opportunity" PV Solar.
Nearly constant PV Watts generated from 9AM until 3PM

BCROE "East - West" idea
=====================
He is installing a very simple Fixed Ground Mount.
I don't see how an East-West only design can have a higher Yearly kWhr production vs "SE + South + SW"
I don't think we gain anything by greatly exceeding the Inverters Max Watts and then CLIP the Inverter for 8 hours = he loses watts
You have enough Solar Panels to "max out" your inverter for 8 Hours, he does not, that is a huge design difference.
To "max out" a 5KW Inverter for 8 hours, he would need 23 Panels facing East and 23 Panels facing West = 46 Panels
He only has 30 Panels.
Please explain how "East + West only" can generates more Yearly kWhrs vs "South-East + South + South-West" ?

I have winter ( Dec - Jan - Feb ) data for my system
I will check to see how many Daily PV Hours an "East + West" setup might lose.


EDIT:
My kWhr PV Production for Dec & Jan is ~45% of June.
I remove all snow from my Solar Panels, as needed.
So, winter production is much lower but not insignificant.

[SunEagle]

Why not install the full amount of panels the inverter can accept on 2 channels (I presume that is 11 panels per channel or 22 total) and the rest (8 panels) install either on the East or West side whichever gets more days of good sunlight.

Putting the majority of your panels facing South will not over load the inverter yet should yield the highest output compared to a portion at 3 different compass headings.

Unfortunately with the weather patterns not being consistent every day, a fixed array will get you a mixer of good days of production and not so good days.

[bcroe]

BCROE,
Thank You for the graphs.
We are trying to maximize the Yearly kWhrs produced using 30 x 275W PV Panels and one 5 KW Inverter.

He only has 30 Panels.
Please explain how "East + West only" can generates more Yearly kWhrs vs "South-East + South + South-West" ?

I am not presenting a cookbook method to the ideal solution, just showing some ideas
that worked for my latitude, snow, cloud, and inverter limits situation. Note in particular
that designing to minimize snow impact will require a more complex mount with easy
variable tilt. My first winter I was out at sunrise nearly 2 dozen times to get the snow
off, each time taking more than an hour. The redesign reduced those efforts by 80%,
make your decision and be prepared to live with it.

Your variables are all different from mine, your best solution will also be different. I
am not claiming which is best for you, however I bought panels to do the job. I am
pushing out ideas that might be overlooked, and later long regretted.

Guess I will throw out one more idea. Panels may be mounted landscape, portrait,
or any angle between, the sun does not care. My solar area is on a 10% grade,
some 6.3 degrees. I have seen people move all kinds of dirt, build embankments,
and so on to get an array perfectly level. The arrays I built are laser straight, but
they follow the land. The yellow level here shows just how much slope I have.
good luck,
Bruce Roe


TiltPV3.JPG

[NEOH]

Why not install the full amount of panels the inverter can accept on 2 channels (I presume that is 11 panels per channel or 22 total) and the rest (8 panels) install either on the East or West side whichever gets more days of good sunlight.

Putting the majority of your panels facing South will not over load the inverter yet should yield the highest output compared to a portion at 3 different compass headings.

Unfortunately with the weather patterns not being consistent every day, a fixed array will get you a mixer of good days of production and not so good days.

Yes, you are correct ...
South Array #1 on Chan A = 11 Panels x 275W x 80% = 2,420 Watts
South Array #2 on Chan B = 11 Panels x 275W x 80% = 2,420 Watts
SE or SW Array on Chan C = 8 Panels x 275W x 80% = 1,760 Watts

I was so focused on keeping the system symmetrical, that I never considered this option
He has a huge flat farm, clear East & West horizons
Would the South-East PV Array be cooler in the morning vs the hotter South-West PV Array in the evening?
Therefore, potentially more watts in the morning vs evening?

[SunEagle]

Yes, you are correct ...
South Array #1 on Chan A = 11 Panels x 275W x 80% = 2,420 Watts
South Array #2 on Chan B = 11 Panels x 275W x 80% = 2,420 Watts
SE or SW Array on Chan C = 8 Panels x 275W x 80% = 1,760 Watts

I was so focused on keeping the system symmetrical, that I never considers this option
He has a huge farm, clear East & West horizons
Would the South-East PV Array be cooler in the morning vs the hotter South-West PV Array in the evening?
Therefore, potentially more watts in the morning vs evening?

Only you and your friend can determine which is the better focus. Sometimes there could be fog in the morning or clouds in the afternoon. It all depends on where the array is located and they type of weather you get.

Still since the 8 panel array is the smallest the output affected by clouds or fog is much smaller then the 22 panels facing South.

[NEOH]

I am not presenting a cookbook method to the ideal solution, just showing some ideas
that worked for my latitude, snow, cloud, and inverter limits situation. Note in particular
that designing to minimize snow impact will require a more complex mount with easy
variable tilt. My first winter I was out at sunrise nearly 2 dozen times to get the snow
off, each time taking more than an hour. The redesign reduced those efforts by 80%,
make your decision and be prepared to live with it.

Your variables are all different from mine, your best solution will also be different. I
am not claiming which is best for you, however I bought panels to do the job. I am
pushing out ideas that might be overlooked, and later long regretted.

Guess I will throw out one more idea. Panels may be mounted landscape, portrait,
or any angle between, the sun does not care. My solar area is on a 10% grade,
some 6.3 degrees. I have seen people move all kinds of dirt, build embankments,
and so on to get an array perfectly level. The arrays I built are laser straight, but
they follow the land. The yellow level here shows just how much slope I have.
good luck,
Bruce Roe

Wow, that is a nice Ground Mount
My friend does not have the skill set to build a Ground Mount like yours.
I have read about East-West facing PV Panels installations = no shading.
https://www.pv-tech.org/editors-blog...t-solar-design
Maybe I was missing a key element of the East-West design and so I posted my concerns.
An East-West design can certainly fully utilize an Inverter at 100% Power, for many, many hours.

[bcroe]

My friend does not have the skill set to build a Ground Mount like yours.

He might be able to build this cheap, simple 2 sided array. This version has disadvantages
of fixed tilt, requiring unshaded area on both sides, being too close to the ground to clear
all snow accumulation, and perhaps a 10 year life. Bruce Roe

DSCN0721.jpg

[NEOH]

He might be able to build this cheap, simple 2 sided array. This version has disadvantages
of fixed tilt, requiring unshaded area on both sides, being too close to the ground to clear
all snow accumulation, and perhaps a 10 year life. Bruce Roe

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