Finally, the start of my 25kw Ground Mount grid-tie system

live4soccer7

Solar Enthusiast
Something I just realized is that Fronius is made in the US. It may not be engineered here etc..., but the new proposed solar plan for 2023+ is if 55% plus of the project's components are made in the US then you get an extra 10% tax credit on top of the proposed 30% Solar ITC. If I were to use fronius inverters AND Mission or Silfab Panels then I think I would hit 55% with those two items.

I want to have this thing functional by the end of next year, so I could just wait a couple months until I hit 2023 and put it into service in January. lol

Granted, these were just proposals and aren't set in stone. There could always be other stipulations as well.

For my own information, really. Price differences between fronius and SMA with wire included.

Fronius 15kw x 3 = $11,031
2 MPPT each x 2 sets of wire = 12 total wires x 200' (length of my run) = 2400 feet of wire.
$400/1000' of wire = $960
Total Cost = $11,991

SMA 7.7kw x 6 = $8,214
3 MPPT each x 2 sets of wire = 36 total wires x 200' = 7200 feet of wire
$400/1000 of wire = $2880
Total Cost = $11,090

This is not to mention that I don't think I can fit that many wires through my conduit and it will be a lower voltage so there will be more loss over that 200' AND if the 10% "bonus" tax credit does work out then that would definitely make up any difference in not only JUST the inverter price, but that 10% is realized on the entire system.

I'm thinking it REALLY makes more sense to go with fronius for this project.

With the fronius panels, I'll be able to run about 16 panels per string with a 450W panel or so (DC Voltage Limitation). Obviously I will check that again once I find a new panel. That would put me at 6 strings x 16 panels = 96 panels

This will make the PV wattage around 14.4kw out of the max PV/DC wattage of 18kw on the fronius units. They will stay within the optimal MPPT voltage range as well.

Anyone see anything wrong with my thinking/design on this as a rough plan ATM. I know I've been all over the place, but sometimes that's what it takes to land at the proper solution that best fits the application.
 
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live4soccer7

Solar Enthusiast
Assuming the 55% thing happens. Very rough estimates

Panels $19,000 (bluesun) 96 (43.6kw) - NON-US
Racking $15k - UniRac, Sunmodo, ironridge most likely - US
Fronius Inverters x 3 $11k - US
Other Bits and pieces in the US $5k - US

Total: $50,000
Percentage in the US: 62% (31/50)

$50,000 x .4 (total tax credits in 2023) = $20k
Total cost of system is $30k

Yes, these are extremely rough estimates and I'm sure it will end up costing even more.

I wanted to stay under $1 installed before tax credits, but I've come to the realization that that is simply not going to happen in this market.
 
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live4soccer7

Solar Enthusiast
@wattmatters Thanks! That's what I did for a quick calculation on those numbers. I think my calculations ended up at being able to do 17 panels, but I like 16 since it is an even number.

The more I think about it, I think the sunmodo rack with the earth augers is the way to go for this install. I like to two post style racking system as opposed to uniracs single post GFT setup. With the sunmodo I'll be able to skip concrete which will likely save money and lots of time. I don't think the post being in direct contact with the ground will be an issue and doing some reading that even in concrete they can have an alkaline reaction with the concrete. I'm sure is "6 one way half a dozen the other" on which will last longer. Hopefully it lasts 30 years and then as someone stated we can have a small fusion reactor sitting out in the yard. haha.

Now to get a quote for the sunmodo stuff. I have an email out of CEDgreentech, but I have yet to hear back, again. I'm thinking of just calling sunmodo and seeing if they will sell to me direct for this size install. I can provide them business information if they required to put the order under. If not, I'll have to contact a different CED that is about 4-5 hours away from me, which I really do not want to do.
 

MurphyGuy

Solar Addict
Have you done the loss calculations for the DC wiring? Standard 600 volt THHN/THWN wire isn't going to handle the 600+ volts coming from the solar panels.. You'll need high voltage wire for that... The "PV Wire" my panels are connected with is good for 2000 volts, but its only a 10ga wire.

Don't forget, you can't just use standard the popular 10 or 12 gauge PV wire that most places sell.. Since your MPPT ports are rated for 30 amps, and you're pushing 200 feet, you're going to need something in the 8ga size (1.6% loss) or 6ga (1% loss).
 

MurphyGuy

Solar Addict

Yes, that would do it. However, if you have the room in your main breaker panel in the house, you might be better off just running all three inverters straight back to that panel through the same conduit. Its only 6ga wire on a 70 amp double pole breaker per inverter.

This would save you from purchasing the box and running giant 200 amp wire.. It would also mean that if/when you went off grid, you could flip all your breakers in a single box.. If you go off grid, you're probably going to need to shut down two of the three inverters.. disconnecting them with the breaker is the best way.
 

live4soccer7

Solar Enthusiast
@Murphey I think I have room in the breaker panel. I will check and see.

Let me pull some documentation on the fronius inverters real quick. My printed version is a little tough to read for some reason. This is regarding wire size.
 

live4soccer7

Solar Enthusiast
This is from the fronius documentation:

AWG 14 - AWG 6 copper direct, AWG 6 aluminum direct (AWG 10 copper or AWG 8 aluminium for overcurrent protective devices
up to 60A, from 61 to 100A minimum AWG 8 for copper or AWG 6 aluminium has to be used), AWG 4 - AWG 2 copper or alu-
minum with optional input combiner.

The current on the panels (each MPPT) would be around 11A at max. Each MPPT on the fronius units would get their own set of PV wires. 3 fronius units, 6mppts, 6 pairs of wires, 6 string series in the entire array.

I'd be going with the 2kv 10gauge wire. Let me check a loss calculator on those numbers.
 

live4soccer7

Solar Enthusiast
1631999218239.png

If I set voltage to 400 then it drops to about 1.3% and raise it to 800v it is about .65%


I think the 10awg wire will be perfect, but please do let me know if I am overlooking something here.
 

MurphyGuy

Solar Addict
View attachment 65208

If I set voltage to 400 then it drops to about 1.3% and raise it to 800v it is about .65%


I think the 10awg wire will be perfect, but please do let me know if I am overlooking something here.

I don't know the specs on your panels but I was under the impression you were going to parallel strings.. So if a panel put out 10 amps, then you'd have two strings paralleled for 20 amps, or even 3 strings for 30 amps..

I just used the specs on the inverter which say 30 amps max per channel and calculated wire based on that..

If your panels are marching single file and you're not paralleling strings, then you can just jack the voltage up to near max and use the smaller wire..

But keep in mind, during cold sunny spring days, your panels can actually put out more than their rating, so always leave 25% of fudge room on your MPPT inputs.. If your inverter has 1000 volts max, DO NOT go installing 980 volts worth of panels because it will exceed MPPT rated voltage when that special cold sunny day happens.

Also, you should check the voltage in your home's breaker panel.. While the USA is generally 240, the fact is, 240 is almost never exactly 240 everywhere.. Reading internet forums, I've seen people with voltages as high as 245 and one guy, I think his was 247 volts, and that high voltage was causing his solar inverters to trip out because the inverter couldn't raise the voltage far enough to pump in enough juice.

This isn't an issue with small systems, but yours is a large array... at least by residential standards anyhow.
 

live4soccer7

Solar Enthusiast
Thanks. With the fronius units, I do not have to parallel them. They would just be individual series. If I did the sunny boys then I would have to parallel or the amount of runs back to the inverters would get a bit ridiculous at that length.

I have accounted for the cold weather on the voltage as well. My calculations say I could go up to 17 panels without exceeding 1000v and the fronius calculator has me at 16 panels.

I COULD consider doing the SMA units (6) and then run 3 strings in parallel. I think this would be less efficient and I would lose the possible effect of getting a bonus 10% ITC for 55% of the project being "made in the US" if that passes.

Just out of curiosity, if I did the SMA units and put 3 strings in parallel for 33A at 400v it would equate to just shy of 4% loss with 10 gauge copper wire.

I think I'm definitely going at this right with the fronius units, the longer run, larger array, US made potential savings, etc....
 

wattmatters

Solar Addict
Also, you should check the voltage in your home's breaker panel.. While the USA is generally 240, the fact is, 240 is almost never exactly 240 everywhere.. Reading internet forums, I've seen people with voltages as high as 245 and one guy, I think his was 247 volts, and that high voltage was causing his solar inverters to trip out because the inverter couldn't raise the voltage far enough to pump in enough juice.
Can't say specifically about the firmware settings in USA but where I am the grid voltage dynamic power reduction (GVDPR) settings kick in above 253V, and gets pretty restrictive above 258V. Enough time above that and it will trip off. It's happened to me once a few weeks ago, I suffer from fairly high grid voltages where I am.

Now we operate a different voltage environment here (230V is the single phase standard / 400V 3-phase), so it was more as a comment to say the Fronius inverters in general are quite capable of adjusting settings to match local grid voltage conditions with some tweaking of settings in the admin panel. Usually the local power distributor will have recommended small scale generation GVDPR voltage settings to apply (or the maximal allowable).
 

MurphyGuy

Solar Addict
Thanks. With the fronius units, I do not have to parallel them. They would just be individual series. If I did the sunny boys then I would have to parallel or the amount of runs back to the inverters would get a bit ridiculous at that length.

I have accounted for the cold weather on the voltage as well. My calculations say I could go up to 17 panels without exceeding 1000v and the fronius calculator has me at 16 panels.

I COULD consider doing the SMA units (6) and then run 3 strings in parallel. I think this would be less efficient and I would lose the possible effect of getting a bonus 10% ITC for 55% of the project being "made in the US" if that passes.

Just out of curiosity, if I did the SMA units and put 3 strings in parallel for 33A at 400v it would equate to just shy of 4% loss with 10 gauge copper wire.

I think I'm definitely going at this right with the fronius units, the longer run, larger array, US made potential savings, etc....
The SMA units have a maximum MPPT input current of 10 amps, and considering most 350 to 400 watt panels are sitting right at that 10 amp limit, you can not parallel panel strings.

I also think for your setup, the Fronius is a better choice.. that 200 foot distance is really the deciding factor in this. It normally wouldn't be, but the price of copper has gone through the roof and you'd have to run some big wire to push 180+ amps without significant losses.
 

live4soccer7

Solar Enthusiast
@MurphyGuy Thank you for confirming my belief. I am definitely no expert, but I'm accustomed to looking at things technically as I have an engineering background.

Is there any preference to having panels in portrait or landscape?

I'm going to do 48 panel arrays (3 x 16 series). I can do:

4 in landscape x 12 panels OR
2 portrait x 24 panels

The array, physically, is the just about the exact same either way. I was thinking portrait would be better because if you have to remove a panel then it would be much easier instead of it being "buried" in the middle somewhere and having to remove 1 or two other panels to get to it. I doubt I'll have to remove any panels, but it's about the only thing I can come up with other than the "route" that they will be wired in series. I could maybe come up with a more efficient way if they were in landscape that would use a little less wire.
 

MurphyGuy

Solar Addict
@MurphyGuy Thank you for confirming my belief. I am definitely no expert, but I'm accustomed to looking at things technically as I have an engineering background.

Is there any preference to having panels in portrait or landscape?

I'm going to do 48 panel arrays (3 x 16 series). I can do:

4 in landscape x 12 panels OR
2 portrait x 24 panels

The array, physically, is the just about the exact same either way. I was thinking portrait would be better because if you have to remove a panel then it would be much easier instead of it being "buried" in the middle somewhere and having to remove 1 or two other panels to get to it. I doubt I'll have to remove any panels, but it's about the only thing I can come up with other than the "route" that they will be wired in series. I could maybe come up with a more efficient way if they were in landscape that would use a little less wire.

Panel orientation is a personal choice so far as I know. I think the only real consideration there is the physical height of the array as the higher it is, the more wind its going to catch. Other than that, I don't think it matters.

Over a 200 foot run, an extra 5 feet of wire at the array because you like one orientation over another, isn't going to mean squat.

As far as replacing a panel in the middle, the only real challenge is unscrewing the clamps because you have to get to those from the top. In my case, I have a farm tractor and I built a wood platform. My wife lays down on it with her head and shoulders hanging off the far end, and I can lift her up and drive her to the clamp screws.

I'll tell you something I noticed a year after I had the system.. we were gawking at internet pictures where storms would come through and destroy solar farms.. and I noticed something strange.. In many cases, the solar structures are mostly undamaged but the panels were blown away and all busted up. I thought that was a bit odd.

On a hunch, I took the torque wrench and socket back out to the array and started checking all the fasteners I could reach.. almost every single one of them was under-torqued by almost 50%.
I think that after a while, those fasteners loosen up due to the teeth on the clamps settling into place on the soft aluminium. Back onto the platform she went and re-torqued every clamp down to specs.
I checked them again in another year and they were all fine.. Lesson learned.. you need to go back to your array in a year and check them. And yes, make sure you use a torque wrench.. I bought a 1/4 drive unit from Home Depot, trained my 130lb wife how to use it, and then put her on the "platform of death" to go flying from bolt to bolt again.

Also, you're probably already doing it, but if not, make sure you reference the mounting instructions for your panels. There are specs for the rail spacing for both orientations. Its a pretty wide spec, but I suggest you do the math and hit it right in the middle.

Here's photo of the "Platform of death".. My wife still talks about her experience flying like Superwoman. LOL
 

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Hedges

I See Electromagnetic Fields!
What batteries do you use with your SMA off grid? I find that a limiting factor, as the SMA's need seperate everything, and specific batteries. $800 just for web connectivity? Midnight solar MPPT? Shunts? CT's? Why so complex?

SMA Sunny Island needs particular BMS for lithium. Some commercial batteries are compatible. REC makes a compatible BMS you can use for DIY.
If using FLA or AGM, any work; just program parameters.

Very simple, just not cheap. 2x Sunny Island wired 2s, one to four Sunny Boy. For grid-backup, also have a load-shed relay (not a necessity if you do DC coupled PV). At almost 150 lb per inverter and per battery, I like the modularity for a large system. If small enough to manhandle, then an all-in-one could be OK.

SMA Sunny Boy Storage uses particular 400V batteries. It is primarily a peak-shaving PowerWall, but with addition of a transfer switch & transformer, can do grid-backup.

I think SMA ought to bring out "Sunny Boy PV Storage", with each of three inputs able to take either battery or PV string. But haven't seen that yet.
 

Sanwizard

Photon Sorcerer
Why does it seem like Voltronics is leading the way from a simplicity, flexibility, and cost standpoint for hybrid inverters?
I wish there was an innovative American designed and made product that was able to compete with them. I would pay a premium just for the jobs they created here. Tesla is WAY over priced, and uses chinese cells.
 

live4soccer7

Solar Enthusiast
Panel orientation is a personal choice so far as I know. I think the only real consideration there is the physical height of the array as the higher it is, the more wind its going to catch. Other than that, I don't think it matters.

Over a 200 foot run, an extra 5 feet of wire at the array because you like one orientation over another, isn't going to mean squat.

As far as replacing a panel in the middle, the only real challenge is unscrewing the clamps because you have to get to those from the top. In my case, I have a farm tractor and I built a wood platform. My wife lays down on it with her head and shoulders hanging off the far end, and I can lift her up and drive her to the clamp screws.

I'll tell you something I noticed a year after I had the system.. we were gawking at internet pictures where storms would come through and destroy solar farms.. and I noticed something strange.. In many cases, the solar structures are mostly undamaged but the panels were blown away and all busted up. I thought that was a bit odd.

On a hunch, I took the torque wrench and socket back out to the array and started checking all the fasteners I could reach.. almost every single one of them was under-torqued by almost 50%.
I think that after a while, those fasteners loosen up due to the teeth on the clamps settling into place on the soft aluminium. Back onto the platform she went and re-torqued every clamp down to specs.
I checked them again in another year and they were all fine.. Lesson learned.. you need to go back to your array in a year and check them. And yes, make sure you use a torque wrench.. I bought a 1/4 drive unit from Home Depot, trained my 130lb wife how to use it, and then put her on the "platform of death" to go flying from bolt to bolt again.

Also, you're probably already doing it, but if not, make sure you reference the mounting instructions for your panels. There are specs for the rail spacing for both orientations. Its a pretty wide spec, but I suggest you do the math and hit it right in the middle.

Here's photo of the "Platform of death".. My wife still talks about her experience flying like Superwoman. LOL
Thank you for the tips! That's a fine look array!

I was just thinking about the way you wire them to reduce the amount of wire used for the sake of having to buy less wire. haha. The voltage drop with the setup I'll be running is minimal.
 
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