Panel Tilt: Any Benefit to 8° West?

[MrM1]

My present array was designed using the Midnite Solar sizing tool and pretty much maxed out 1 Classic 150 scc. Midnite Solar has assured me there is no problem over paneling the Classic 150 even doubling my present size, the excess power will just be wasted. Overpaneling will help (I believe quite a bit) in mostly cloudy days etc.

I am doubling the size of my roof top array. Presently 3s3p 285w at 2565w array.

Roof faces due south in FL at latitude 29°. Roof pitch is 22°. All panels are mounted flat on that roof, so they are pitched 22° south. This array on a good cloudless day in Oct can produce up to a max of 12 kWh per day. Average is probably 5-9 kWh per day.

Was going to add 9 more panels in a 3s3p arrangement right beside the existing array, again flat on the roof at 22° south. And bring all 18 panels 3s6p into the one Classic 150.

But I am now wondering before I install the new 9 ... If I was to mount all 9 of the new panels on that same roof at 22° south, BUT I also pitched/tilted each new series string 8° West, then those new 9 panels would catch the sun a little more as it was Going down in the west. I would space them so no shading from the sting to the west of each column. Each series string would be 40" wide x 198" long (the 198" is from roof peak to eve).

Would I get much benefit in the afternoon from having half the array tilted 8° West while still tilted 22° south like the first 9 panels?

What issues would this create if any with a single Midnite Solar Classic 150 scc?

 

[MrM1]

Basically the new 9 would look like this, each 3s sting tilted 8°West. (this pic is of morning sun and shade. By 11am whole array - old and new - is in full sun and In the afternoon those new 9 are in full sun)

 

[fafrd]

My present array was designed using the Midnite Solar sizing tool and pretty much maxed out 1 Classic 150 scc. Midnite Solar has assured me there is no problem over paneling the Classic 150 even doubling my present size, the excess power will just be wasted. Overpaneling will help (I believe quite a bit) in mostly cloudy days etc.

I am doubling the size of my roof top array. Presently 3s3p 285w at 2565w array.

Roof faces due south in FL at latitude 29°. Roof pitch is 22°. All panels are mounted flat on that roof, so they are pitched 22° south. This array on a good cloudless day in Oct can produce up to a max of 12 kWh per day. Average is probably 5-9 kWh per day.

Was going to add 9 more panels in a 3s3p arrangement right beside the existing array, again flat on the roof at 22° south. And bring all 18 panels 3s6p into the one Classic 150.

But I am now wondering before I install the new 9 ... If I was to mount all 9 of the new panels on that same roof at 22° south, BUT I also pitched/tilted each new series string 8° West, then those new 9 panels would catch the sun a little more as it was Going down in the west. I would space them so no shading from the sting to the west of each column. Each series string would be 40" wide x 198" long (the 198" is from roof peak to eve).

Would I get much benefit in the afternoon from having half the array tilted 8° West while still tilted 22° south like the first 9 panels?

What issues would this create if any with a single Midnite Solar Classic 150 scc?

There are two factors to consider in panel orientation.

First and foremost is productivity and for that, PV Watts is your friend: https://pvwatts.nrel.gov/

If peak output of your array will never exceed peak output capacity of your SCC, that’s pretty much all there is to it, but if you have over-paneled and are saturating your SCC and wasting potential energy sprite during the peak part of the day, putting enough panels on a differently-oriented roof plane to reduce / eliminate saturation can increase your total energy capture…

 

[MrM1]

Would 8° of tilt really add that much to afternoon collection, or is it just more trouble than it's worth

 

[MrM1]

There are two factors to consider in panel orientation.

First and foremost is productivity and for that, PV Watts is your friend: https://pvwatts.nrel.gov/

If peak output of your array will never exceed peak output capacity of your SCC, that’s pretty much all there is to it, but if you have over-paneled and are saturating your SCC and wasting potential energy sprite during the peak part of the day, putting enough panels on a differently-oriented roof plane to reduce / eliminate saturation can increase your total energy capture…

So your saying in my situation "every little bit helps"?

 

[fafrd]

Basically the new 9 would look like this, each 3s sting tilted 8°West. (this pic is of morning sun and shade. By 11am whole array - old and new - is in full sun and In the afternoon those new 9 are in full sun)

View attachment 73006

Are you charging at 48V or 24V with your classic 150?

If it’s 48V, even your increased array size to 5kW is not overpanelled.

If it’s 24V, 150A means peak output levels of ~3.75kW meaning your 5.13kW array is 37% overpanelled.

If that is the case, searching for a second orientation that reduces / avoids peak clipping might be worthwhile (though I suspect the added cost and complexity of having to mount panels on a tilted tacking system might negate the modest advantage you’re likely to gain).

 

[Jim Burrow]

In my opinion, there is no real power being wasted if your panels are capable of delivering much more than is required to run your load.

For example, if your arrays are capable of generating say 300 watts of power but your load only requires 100 watts, then all your array is going to generate is 100 watts. The extra 200 watts available from your pannels is not being generated, hence there is no waste of power being generated. the heat generated from your panels, neglecting sun radiation (heat energy) will only increase that is generated by the 100 watts being generated to go to the load.

The best time to test this panel heating with respect to load generated is in the morning while the ambient temperature is on the cool side. Each day when the outside air temperature is the same, increase the load power required and then measure the panel temperature.

 

[fafrd]

Would 8° of tilt really add that much to afternoon collection, or is it just more trouble than it's worth

PV Watts can give you a quantitative answer to that question - have you used it yet?

 

[fafrd]

So your saying in my situation "every little bit helps"?

I still don’t understand what battery voltage you are charging.

If 24V, a different orientation might deliver some gains, but probably not enough to justify the extra trouble / expense.

 

[MrM1]

I have not but I will on Monday when I'm at a computer.

BTW system is 24v

 

[MrM1]

VOC of my 3s stings is 117 vdc

 

[MrM1]

The classic 150 at 24v dc can provide a max of 94 amps of charge current to the battery. I have never gotten more than about 80 amps.

I have a 731ah battery bank 8s3p. Doing all it can do, the classic cannot recharge the battery on a good day when it is at 25% SOC. My loads area on average 400w per hour in the day.

But the classic can't provide 94 amps of charge AND use the excess power of the array for loads at the same time can it? It's just 94 amps max either loads or charging but 94 amps at 24v dc is all I'll get regardless of array size?

 

[MrM1]

Getting 8° of tilt will be reasonably easy. I plan to simply stack two S5 Versabrackets on top of each other bolted together on one side of the rack to create the tilt.

1 bracket hi on the West, 2 hi on the east of each panel width will give be 8° of tilt west.

I have plenty of brackets extra because ordering a box was cheaper than ordering the number I needed. So I have all the parts, just didn't know if there'd b any / much benefits

 

[fafrd]

The classic 150 at 24v dc can provide a max of 94 amps of charge current to the battery. I have never gotten more than about 80 amps.

I have a 731ah battery bank 8s3p. Doing all it can do, the classic cannot recharge the battery on a good day when it is at 25% SOC. My loads area on average 400w per hour in the day.

But the classic can't provide 94 amps of charge AND use the excess power of the array for loads at the same time can it? It's just 94 amps max either loads or charging but 94 amps at 24v dc is all I'll get regardless of array size?

My bad - I assumed your 150 had peak output current of 150A, not 94A.

So you are currently paneled at ~85% and will be overpanelled to ~170% once you’ve doubled your array.

That’s really too much overpanelling and your going to be wasting a lot of potential production.

If it was me, I’d invest in a second SCC rather than worrying about changing panel orientation (though again, PV Watts can help you figure out how much a second panel orientation an help to reduce clipping losses).

 

[MisterSandals]

Getting 8° of tilt will be reasonably easy.

To put this in perspective, the sun moves across the sky at 15 deg per hour. So 8 deg will shift the solar peak for those panels by just over half an hour.

 

[chrisski]

Looking at your picture, I would think you would see more results wise by cutting down the trees that shade the panels.

I over-panel on a much smaller scale for a solar generator. I lose so much with my panels on the ground to shading. I can be at 300 watts from a single string and a couple of cells in one of three panels get shaded, and it drops to 70 watts, or less. I have 600 watts of panels that can max at 420 watts, and I am actually adding a third string to make it 900 watts.

I can't cut down those trees or move buildings, so I need to overpanel to get a reliable output for the whole day.

The tilt you show with the lines is a bit more than 8°, probably more like 30°. My portable panels at 30° will get power a couple hours earlier in the morning and a couple hours later in the evening. Most days I hardly use any power, but the days when I do that 30° makes a huge difference.
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You've got the data though. To me it makes sense if you want the power at the end of the day. Might not be the most efficient or best way, but there are reasons to tilt the panels.

 

[12VoltInstalls]

That’s really too much overpanelling and your going to be wasting a lot of potential production.

If it was me, I’d invest in a second SCC rather than worrying about changing panel orientation

I didn’t see or maybe missed where OP is
If he’s in a seasonally cloudy region (like me here in Vermont where this time of year can be 3days+ cloudy days continuously, even a week with no sun) it’s entirely likely that he’s overpaneled 7 or 8 months but trying to compensate for The Dark Months where a few amps you get with a lot of series panel might be his goal. Dunno where he is.

Not arguing - just pointing out that ‘wasted watts’ can be subject to circumstances.

 

[fafrd]

I didn’t see or maybe missed where OP is
If he’s in a seasonally cloudy region (like me here in Vermont where this time of year can be 3days+ cloudy days continuously, even a week with no sun) it’s entirely likely that he’s overpaneled 7 or 8 months but trying to compensate for The Dark Months where a few amps you get with a lot of series panel might be his goal. Dunno where he is.

Not arguing - just pointing out that ‘wasted watts’ can be subject to circumstances.

Florida, I believe.

 

[12VoltInstalls]

Oh, the sunshine state.
So the overpaneling makes less sense.
Or cents.

 

[wattmatters]

Basically the new 9 would look like this, each 3s sting tilted 8°West. (this pic is of morning sun and shade. By 11am whole array - old and new - is in full sun and In the afternoon those new 9 are in full sun)

That's a lot more than 8° tilt. That said, the bigger the tilt the more the production is spread across the day and that's probably a good thing with off-grid when the SCC is maxed out anyway.

But if you want to consider an interesting option, have a think about putting your array in a crinkle cut arrangement, sort of like this:



These can be very space efficient arrangements if the tilt is modest since there is no real need to put space between rows (columns?).