How much Solar energy with only vertically or horizontally mounted solar panels?

sunshine_eggo

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One optimization that I am considering now, in the case of the vertical walls, is to put
the solar panels horizontally instead of vertically, so it would be more easier to incline
them, like 10" away from the wall, looking a little bit like the shutter of a window.

The inclination for a 10" base and 39" high triangle would be about 15 degrees.

For the purposes of computation, they are an 85° tilt from horizontal.

I could then have 8 panels on each of the east and west side of the stairways cabin,
and may be 8 flat panels on top of the stairways cabin, or a total of 24 panels.

For the elevator cabin, I could have then install 2 panels on the east, south, and west
with the same inclination of 15 degree and 2 panels on the roof. or a total of 8 panels.

So the total would be 32 panels, with
- 10 panels flat,
- 10 panels east and west with an inclination of 15 degrees,
- 2 panels on the south with an inclination of 15 degrees.

1637418430979.png

Assuming 240W panels. Those are 60 cell, so you can fit 3 in series on a 150V controller, and that's the desired config. That makes your array combination a little tricky and may necessitate multiple charge controllers.

Fall short Nov-Jan and produce far more in the spring/summer months.
 

12VoltInstalls

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Fall short Nov-Jan and produce far more in the spring/summer months.
Pardon my intrusion. Reading this with interest. (Don’t want to hijack)
So unless powerco payback is possible - am I correct reading that the first (prior) chart (where everything per month sums at ~20kWh) to say that while the annual daily need is accommodated with vertical panels, but with the 15-degree tilt panels it is not though the annual total production is higher?
 

sunshine_eggo

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Pardon my intrusion. Reading this with interest. (Don’t want to hijack)
So unless powerco payback is possible - am I correct reading that the first (prior) chart (where everything per month sums at ~20kWh) to say that while the annual daily need is accommodated with vertical panels, but with the 15-degree tilt panels it is not though the annual total production is higher?

No. The first run was an arbitrary 2000W south and 1600W flat, East and West.

The second iteration had many changes - angles and wattage... only 480W on the South with 2400W on Flat, East and West.

The South vertical panels have the largest influence on winter production.

Shown here together...



1637377839881-png.72928


6800W

1637418430979-png.72968


7680W with much higher non-winter production due to placement and orientation.

The 15° from vertical really kicks up the summer production on the E/W panels.
 
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@sunshine_eggo thank again for the additional results.
Thank you for your guidance and for putting me on the good track.
I need now to get familiar with the Solar Irradiance tool.

I think that providing additional tilting to the panels is the way to go. From your
recommendation I will try now to get at least 4 south panels with some inclination.

Since the wind is mostly blowing from the west, only the edge of the south panels
will be exposed but I imagine that there would be still some turbulences.

This installation will be more difficult than just bolting the panels against a wall,
but this seems to be worthwhile. I need to find now some information
on how to build some solar panels holding systems.

I noticed also some kits specifically design for holding securely
the solar panels while allowing adjusting their inclination.
 

Hedges

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With 16 panels, I might consider 4 on each of four faces (East, West, South, Horizontal). Those four groups in parallel into one MPPT.
Either 4s4p, or 2s8p.
East and West vertical (or slight tilt) won't contribute as many Wh, I'd guess half as much, even in Summer.

PV panels seeing ambient light but no direct sun seem to have Voc about equal to Vmp of the ones with direct sun, so not stealing current.
Inverter or SCC doesn't have to be as large as if all panels oriented one direction.

"off grid", but offset utility bill? So you can still get power from the grid when needed?

Batteries are usually not cost effective. I think grid-tie zero export (current transformers around grid feed wires to measure) with no batteries could be the best way to go. Batteries only if you need power when the grid is down.
 

sunshine_eggo

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All three scenarios (two prior and new):


1637470837130.png


(Note the last, I did not update the angles on the panel side, but those are just labels)

Last one is like the prior with the following changes:
South is tilted to 60° from horizontal (30° from vertical) - optimal for winter
South is doubled from 480 to 960W
East and West are changed to 45°, which is close to optimal.

As you can see, your production goes WAY up, and the only month you fall short of 20 is December.

Note that with the spreadsheet, each iteration takes me about a minute. I just enter the array into PVWatts, replace the numbers in the "Hours" column for that array and tweak the power if you're changing panels.
 
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All three scenarios (two prior and new):
...
Thank you for adding the optimal case.

Something I was interested with was to compare the performance of the panels for each of the different cases.
To do that, I calculated the average yearly energy performance for each of the left columns and found the following:

- The South-85 is 20 % more efficient that the South-Vertical
- The South-60 is 57 % more efficient that the South-Vertical

- The East/West-85 is 11 % more efficient that the East/West-Vertical
- The East/West-45 is 56 % more efficient that the East/West-Vertical

- The South-60 is 15 % more efficient that the Flat-Horizontal
- The East/West-45 is just 8.3% less efficient that the Flat-Horizontal

Note: This is a yearly average, there is less efficiency variations in the summer than in winter.

I wonder now if I should convert the Flat panels into South-60 panels, to favorise the winter over summer.
Since the Flat longer edges are facing south, I would need then to raise the other side edge by 35" to get the correct tilting.

See the following example: _/|__/|__/|__/|__/|__/|_
 

sunshine_eggo

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Thank you for adding the optimal case.

Something I was interested with was to compare the performance of the panels for each of the different cases.
To do that, I calculated the average yearly energy performance for each of the left columns and found the following:

- The South-85 is 20 % more efficient that the South-Vertical
- The South-60 is 57 % more efficient that the South-Vertical

Noon sun is the most intense. Sunrise and sunset have very little energy to be had.

The sun at the lowest point on the horizon at 35°N latitude is about 60° from horizontal.

- The East/West-85 is 11 % more efficient that the East/West-Vertical
- The East/West-45 is 56 % more efficient that the East/West-Vertical

Veritcal captures more sunrise, less high noon.
85 captures less sunrise, more high noon.
45 captures even less sunrise but even more high noon.

Again, high noon is where it's at.

- The South-60 is 15 % more efficient that the Flat-Horizontal
- The East/West-45 is just 8.3% less efficient that the Flat-Horizontal

Note: This is a yearly average, there is less efficiency variations in the summer than in winter.

I wonder now if I should convert the Flat panels into South-60 panels, to favorise the winter over summer.
Since the Flat longer edges are facing south, I would need then to raise the other side edge by 35" to get the correct tilting.

See the following example: _/|__/|__/|__/|__/|__/|_

60° is better than flat UNLESS the panels closer to the sun are shading the panels behind them, and that's very likely in your scenario. In this case. the shaded panels will perform very very poorly. You'd need to work out the geometry. Rather than having 6 rows as you've sketched, maybe you could fit 3 rows across that same distance, and that might very well shift you to better winter/reduced summer.
 
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60° is better than flat UNLESS the panels closer to the sun are shading the panels behind them, and that's very likely in your scenario. In this case. the shaded panels will perform very very poorly. You'd need to work out the geometry. Rather than having 6 rows as you've sketched, maybe you could fit 3 rows across that same distance, and that might very well shift you to better winter/reduced summer.
I plan to make some full size mockup with some cardboard to have a better idea of the framing need and possible shading,
something to avoid by all means. I read about a case where the mast of a TV antenna was creating noticeable degradations.
 
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In the 3rd scenario, the hours labels are correct. I did not update the labels in the watts group. The numbers are correct.

The 960W was in response to you saying you would add additional South facing panels.
So there is:

2400 W = 6 x 400 W
2000 W = 5 x 400 W
1600 W = 4 x 400 W

But I wonder about:

960 W = 2.4 x 400 W ?
480 W = 1.2 x 400 W ?
 

sunshine_eggo

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At some point you indicated that you were limited to panels of a size typical of the 240W panels from SanTan, so iterations 2 and 3 have been multiples of 240W starting when you indicated 32 total panels, 10, 10, 10 and 2, which is the second iteration.
 
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At some point you indicated that you were limited to panels of a size typical of the 240W panels from SanTan, so iterations 2 and 3 have been multiples of 240W starting when you indicated 32 total panels, 10, 10, 10 and 2, which is the second iteration.
You were right, the smaller unit is about 7' high compare to the larger one which is about 9' high, so the larger panels were too tall.

I made some cardboard mockup of the (77" x 39") and the (65" x 39") solar panels to have a good overview of this project.

I realise now that inclining the panels will be a major work, because I would like to avoid having the bottom of the panels touching the roof.

So I would have to keep the panels vertical and directly bolted to the walls.

For the smaller unit, I can install 2 small south panels, 2 small east and west panels, and 2 large flat panels on the roof, or a total of 8 panels.

For the larger unit, I can install 6 large east and west panels, and 6 large flat panels on the roof, or a total of 18 panels.

See below the solar power production using the spreadsheet that you provided: (Thank you a lot BTW, this make the calcultion so easy) !!!

San Francisco Treat! Uni 1&2 - Vertical Only .jpg

In winter, the solar production
- for the smaller unit is around 6.3 kWh, and
- for the larger unit is around 19.2 kWh,
with a total of 25.5 kWh.

There is only a slightly product increase in the Summer because of the use of vertical panels, but there is no additional need anyway.

For the smaller unit, the MPPT needs to handle the 4P (2S South, 2S Flat, 2S East, and 2S West).

I wonder if it would be preferable to use two separate MPPT for the larger unit, to split the load,
or if a single MPPT sould be sufficient to handle the 6P (2 x 3S Flat, 2 x 3S East, and 2 x 3S West) ?
 

sunshine_eggo

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You were right, the smaller unit is about 7' high compare to the larger one which is about 9' high, so the larger panels were too tall.

I made some cardboard mockup of the (77" x 39") and the (65" x 39") solar panels to have a good overview of this project.

I realise now that inclining the panels will be a major work, because I would like to avoid having the bottom of the panels touching the roof.

So I would have to keep the panels vertical and directly bolted to the walls.

For the smaller unit, I can install 2 small south panels, 2 small east and west panels, and 2 large flat panels on the roof, or a total of 8 panels.

For the larger unit, I can install 6 large east and west panels, and 6 large flat panels on the roof, or a total of 18 panels.

See below the solar power production using the spreadsheet that you provided: (Thank you a lot BTW, this make the calcultion so easy) !!!

View attachment 73176

In winter, the solar production
- for the smaller unit is around 6.3 kWh, and
- for the larger unit is around 19.2 kWh,
with a total of 25.5 kWh.

There is only a slightly product increase in the Summer because of the use of vertical panels, but there is no additional need anyway.

For the smaller unit, the MPPT needs to handle the 4P (2S South, 2S Flat, 2S East, and 2S West).

Since you're mixing panels, you will likely need an MPPT for each panel type due to the fact that the 2S 400W will likely have different Vmp than the 2S 240W.

I wonder if it would be preferable to use two separate MPPT for the larger unit, to split the load,
or if a single MPPT sould be sufficient to handle the 6P (2 x 3S Flat, 2 x 3S East, and 2 x 3S West) ?

For the larger unit, you're just dealing with so much potential wattage, you may need 2X controllers; however, since your arrays will never see maximum output, one might suffice:

2400*3 / 48 = 150a - few charge controllers offer over 100A.
 

Bluedog225

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A lot to digest here. I’m surprised that vertical panels even come close to flat (horizontal) panels in terms of production (If I am reading this correctly).

I’ve got a tall (30’) structure with a flat roof. Some east or west facing panels on the vertical walls could stretch my production curve substantially. Will dig in a little.
 

sunshine_eggo

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A lot to digest here. I’m surprised that vertical panels even come close to flat (horizontal) panels in terms of production (If I am reading this correctly).

I’ve got a tall (30’) structure with a flat roof. Some east or west facing panels on the vertical walls could stretch my production curve substantially. Will dig in a little.

It's all about angles of incidence.

Flat panels at ~35° N latitude see a ~60° angle of incidence with the sun on the longest day in winter. This results in about 50% of the solar being available. A vertical panel at the same location will only have a ~30° angle of incidence with the sun and gets about 85% of the sun's available energy.

Please note that the numbers in the hours columns also factor in San Francisco weather. Your results would be different.

You can simulate various individual arrays at https://pvwatts.nrel.gov/ for your exact location and average weather.
 

Hedges

I See Electromagnetic Fields!
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So I would have to keep the panels vertical and directly bolted to the walls.


I wonder if it would be preferable to use two separate MPPT for the larger unit, to split the load,
or if a single MPPT sould be sufficient to handle the 6P (2 x 3S Flat, 2 x 3S East, and 2 x 3S West) ?

Roof eaves normally overhang walls a couple feet, so wall mounted panels need to be enough below the eaves to avoid shading until angle of sun is such that you don't mind having power production cut off. If eaves stick out 2', then 2' below eaves would be a 45 degree angle and presented area/power would have dropped to about 0.7x of peak when that occurs. Maybe 4' below eaves would be desirable. (If that was a flat panel clipped by shade when sun hits at 45 degrees, 0.7x might be about correct. But on wall when sun strikes it horizontally, sun is just above the horizon and not as intense, and below the horizon of course nothing. So sun striking at 45 degrees and steeper angle is a bigger part of your production.)

Since you're mixing panels, you will likely need an MPPT for each panel type due to the fact that the 2S 400W will likely have different Vmp than the 2S 240W.

With series strings of panels, you may be able to mix brands on an MPPT if the strings add up to similar Vmp. I do that with 12V, 24V, 36V panels.

A lot to digest here. I’m surprised that vertical panels even come close to flat (horizontal) panels in terms of production (If I am reading this correctly).

I’ve got a tall (30’) structure with a flat roof. Some east or west facing panels on the vertical walls could stretch my production curve substantially. Will dig in a little.

Might be close on average year round, various results depending on whether you're at the equator or in Alaska. At some latitude they would be the same. But peaks occur in different months, which doesn't matter for net metering but does matter for zero-export; needs to match or remain under your daytime consumption to maximize use.
 

GLC

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I plan to use a 48 V battery system, as I need to store about 10 to 20 kWh of solar energy.

I noticed that some solar inverters are limited to 150 V, but I believe that some chargers would accept about 250 V,
which would allow then to put all of the 4 panels in series to lower losses, since I will have at least 300 ft of wiring?

Does having solar panels not producing any solar energy has any effect on the others panels, or is it better to use separate inverters?
When you say "solar inverters limited to 150 volts", are you meaning solar controllers?
 
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