My DIY 60 kW 220 panel setup

[crazydane]

I don't think EG inverters support AC coupling.
How about using a battery inverter that does (preferably Sunny Island), so it can interact with your GT PV Sunny Boys?
For a split-phase system that backfeeds grid, the max system is 4x SI with 24kW of SB. Once disconnected from grid, more SB could be switched onto it for total of 48kW.

Maybe I'm not interpreting this diagram correctly then:



I would have the grid connected to the Utility input (fed from the transfer switch load side) and my house feeder to the Load output. I know that if I have solar panels connected to the MPPT inputs, those will only charge the battery and NOT feed anything back into the grid. I'm not looking for that since my Sunny Boy inverters are already feeding into the grid and maxing out what the 50 KVA transformer on the street is capable of.

I think what I'm not clear on, is exactly how the EG inverters operate over a typical 24 hour period with utility/grid present on the AC input at all times along with a more or less constant load on the AC output side. Will it just keep the batteries topped off at all times and in the event that I lose grid power, start supplying the load from the batteries? In essence function just like a giant UPS? And if it happens to be daytime, the MPPT inputs will attempt to keep the batteries charged, or at least slow down them being drained.

These are the SMA inverters I have:

Discover the Sunny Boy 3.0-US - 7.7-US | SMA America

Discover the Sunny Boy inverter 3.0-US - 7.7-US ► PV performance optimization with SMA ShadeFix ► SMA's SunSpec certified shutdown device

www.sma-america.com

Are you suggesting they can somehow interact with these:

Discover the Sunny Island 4548-US / 6048-US! | SMA America

The efficient island manager Sunny Island 4548-US / 6048-US ► Now with 20 % more power! ► Efficient, simple, flexible and durable! ► Check out now!

www.sma-america.com

 

[crazydane]

It's the hotdog/bun problem. When you have more solar, you're going to get more rigs, and then start all over again. ?

Lol, yeah. That was my plan last fall, but profits kept going up, so I kept getting more rigs. But THIS time, there is going to be a lull of a few years, right?

 

[stienman]

Just as soon as everyone is convinced the crypto market has settled down, it'll shake its tail feathers and everyone will be right back at it, kicking themselves for whatever choice they made now. There does seem to be a pretty consistent 2 year lull after every big spike, but who knows.

“The stock [crypto] market is a device for transferring money from the impatient to the patient.” Warren Buffett, paraphrased.

 

[crazydane]

Ha, I love that quote! That is so true. I've been in it since early 2017 and caught 2 waves so far and HODL'ing as much as I could and just kept mining throughout it all.

 

[Hedges]

These are the SMA inverters I have:

Discover the Sunny Boy 3.0-US - 7.7-US | SMA America

Discover the Sunny Boy inverter 3.0-US - 7.7-US ► PV performance optimization with SMA ShadeFix ► SMA's SunSpec certified shutdown device

www.sma-america.com

Are you suggesting they can somehow interact with these:

Discover the Sunny Island 4548-US / 6048-US! | SMA America

The efficient island manager Sunny Island 4548-US / 6048-US ► Now with 20 % more power! ► Efficient, simple, flexible and durable! ► Check out now!

www.sma-america.com

I'm not particularly familiar with how each of the MPP and other such inverters function. Maybe some will feed grid, if UL-1741.

Yes, a system built from Sunny Islands will control Sunny Boys. That's what I have.
There are limits on current that can pass through their relays (56A per Sunny Island), which limits how much Sunny Boy wattage can be downstream if backfeeding grid. When disconnected from grid, SB wattage can be up to 2x SI wattage.

Sunny Island is expensive but there may still be some stock left over from DC solar debacle at resellers. Best deals I've seen recently were from Stella Volta, bundled with Midnight Solar boxes. Two pairs in stock:

MidNite Solar MNSI6048D-ACCPL Pre-Wired AC Couple System

Shop now for MidNite Solar MNSI6048D-ACCPL Pre-Wired AC Couple System.

www.stellavolta.com

 

[crazydane]

Downloaded the manual and looked at the diagram and the connectors. So the SI doesn't actually have any MPPT input but is designed to work in a system that also contains SBs. So from looking at this diagram:



I currently have each of my 8 SBs individually connected to an Ethernet switch on my LAN. From the diagram above, it looks like I would need to get a Sunny WebBox and have the SBs and SIs communicate over the proprietary SMA com bus, is that correct?

Looking at the specs, I see the 56A max AC input rating you mentioned:


The total current output from my 8 SBs is:



So 4 SIs will almost be enough (57.35A per SI), but I think it will be close enough since not all the arrays are at the same azimuth and tilt, so it is unlikely that all 8 SBs will peak at the same time. Of course if I start adding East and West facing panels to the 7 unused MPPTs, that could change.

So instead of this:



I could relocate the generator, transfer switch and disconnect from the house down to the shop and eliminate the drone of the generator at the house when I loose the grid. Of course the generator might not even have to kick on if the outage is that too extended as I could run off the batteries connected to the SIs. I could then also transfer my 400A service from the house down to the shop. That would eliminate the voltage drop I'm currently experiencing by having all the solar generated power spanning the 200' between the shop building and the house before it hits the meter base, which determines how much power is send back to the grid for my kWh bank.

So the diagram would look something like this instead:



The big risk is that the POCO could bust me for being way over the 20 kW of PV that they allow. But it would all depend on who they send out to approve the application for moving the service.

I could start by ordering 400A service to the shop building, and once that was up and running, call to cancel the service at the house. That would probably be less risky. Worst case, I guess I could just tell them to shove it and go 100% off grid.

Hmm, lots of stuff to think about before making a move...

 

[stevensrd1]

Good job, the first step is admitting you have a problem.

Seriously though, wow... great stuff..... can't wait to see more!

Nice!

 

[Hedges]

Sunny Island does not have MPPT or PV input built in. It is primarily used to create an island grid, AC coupled to GT PV inverters, and with AC input from generator or utility grid. It will either let GT PV backfeed through its relay (no control on how much), or disconnect relay in the case of generator or zero-backfeed to grid.

It does (or did) support DC coupled SCC. You can connect any DC charging source, with a battery shunt to tell SI how much current. In that case SI has no control over the DC charging parameters. What it may or may not still support (with latest firmware) is communication by RJ-45 cable to a charge controller. "Sunny Island Charger" branded SMA and manufactured by MSTE was supported, and Midnight Classic could connect through a data interface. In that case, charge voltage was controlled by SI, and measurement was also communicated over RJ-45.

You do not need any external monitoring of Sunny Boy or anything else to make the system work. That would be optional if you want to log production, monitor from the web, or have SMA notify you in case of failure. If you want to throttle SB output to achieve zero or limited export to utility grid (not just zero export through SI relay), some external measurement and control hardware can command SB to achieve that.

SI doesn't support communication with the newer -40 and -41 model SB. Monitoring systems can obtain data from all of them. The only interaction SI would have with them is frequency shift, to control their power output when disconnected from grid.

Multiple SB with PV arrays at different angles would usually flatten power curve, but funny illumination from clouds could cause it to peak higher. You're not supposed to build something that would drive > 56A through each relay. (Configured 2phase4, which would be 4x SI wired 2p2s, current may come close to balancing but not precisely match on parallel paths. I measured 23A on one wire, 24A on the other, last time I checked.)

What I like to do is parallel two PV strings of different orientation into one MPPT. The inverter would clip output to its rating. Penalty for sub-optimum MPPT voltage is about 2% but higher utilization of SCC/inverter (more kWh/day) makes this cost-effective. With Sunny Boy, the MPPT input current is a good fit for single string of larger PV panels, might only work with two if lower amperage. MPPT inputs "A" and "B" can be paralleled, should accommodate 3 parallel strings. Input "C" can't be paralleled.

As you have drawn it, when grid goes down generator would be the only thing powering house. It would also feed SI, recharging batteries. The only thing SI provides battery backup power to is Solar Sub Panel.

On the output of SI you should have Solar Sub Panel (as you do.) That can also serve as Critical Load Panel, e.g. alarm and communication. Only small things that battery can carry through the night, even if only about 10% charge remains, after grid fails and sun has set.

Connect a "Load Shed" relay, from either Critical Loads Panel or from AC wires between SI and Critical Loads Panel. That relay feeds "Important Loads Panel", the things you want to power from battery & PV, such as your house, well pump, A/C. Leave off excessive loads like electric central heating. SI has control relays (two each), and mine uses default load-shed at 70% DoD (for lead-acid.) If battery gets low, and generator was not started to recharge, the house gets disconnected but critical loads and SB remain powered. After sun comes up, it recharges a bit (to 50% DoD) before reconnecting house.

A second stage of load shed is also available. I plan to use that for A/C and laundry, at a higher SoC like 20% DoD.

If you look into Limited Export options, you should be able to use CT on utility wires to measure and keep export < 20kW, through commands to SB. That may be Data Manager and a 3rd party meter. I haven't tried it. I use the (obsolete) Sunny Web Box.

It is best to keep the grid, if only as a generator. It is cheaper and more reliable than gas/diesel generators.
If you do go off-grid (or grid as generator only), 3-phase is an interesting option. 3-phase also works on-grid, but off-grid SMA has "Multi-Cluster", multiple 3-phase islands combining their power to one large island grid. I'm playing with a 3-phase setup, connected to my split-phase grid by only one 120V SI.

 

[crazydane]

Ah ok, I had my drawing above all messed up then. This would be more ideal I believe:



That way, the Shop and House sub-panels are going to take what they want before any excess solar production is pushed through the SIs back into the grid, so WAY less than 54A x 4. Too bad about the communications, but since the SIs regulate the frequency and that SBs sync to that to regulate the power, I should be fine, right?

I could always kill the breakers for some of the SBs if I loose power during the middle of a bright sunny day, so not produce an excessive amount of power that I can't consume. That would keep the frequency from going too high and maybe keep everybody happier?

I would add a load shedding relay to kill the PDUs hanging off the Shop sub-panel, so that in the event I lost power, the mining rigs would go down, which would account for 80-90% of the load at night.

The transfer switch is fully automatic and can be programmed to transfer source on its own, or be controlled externally. I can do generator warm up and cool down, set trigger points, etc:





In my case, I'm not using any of those features, but instead controlling it from the controller on the generator, which is the DSE unit:



It has even more features and functions than the ASCO transfer switch. The main reason I got the DSE, it that particular unit has an Ethernet interface, so I can control from anywhere on my LAN, or via VPN from remote.

So I'm quite certain that between the generator and transfer switch, I can accommodate having the master SI control when the generator needs to run to replenish the batteries.

I agree that I would want to keep my grid connection unless the POCO and/or county inspector gives me a really hard time. I'm not too worried about the POCO, but if they require the new meter base to be inspected before they will connect the power, then I think I'll have issues.

Since I had 400A service at the shop building before, maybe they will let it slide. I'll see if I can chat with them and get a feel for what their expectations are. Perhaps one possibility would be to get a commercial account instead of a residential one, but I suspect the base meter charge will be much higher.

If I add East/West facing strings to my 7 unused MPPT inputs, you're saying I would be better off doing, say 12 facing East and 12 facing West parallel them up, and then connect to input A or B? In my current install with all 60 cell panels, I like to aim for 400V in each string to maximize efficiency.

So having 12E+12W in parallel on input A or B will be better than 12E and 12W on inputs C on 2 difference inverters?

 

[ArkRob]

That pole barn looks exactly like a project I have in mind.

Could I talk you into taking some more details and photos of that?

 

[crazydane]

@ArkRob Sure. So the rails that the panels are attached to are 10' sections of superstrut.



I used regular flat brackets to connect to struts together:



The panels are attached via cone nuts and stainless 1/4" bolts with insulated washers on the panel side:



The rails of superstrut are bonded together and run into the ground on the inverters.



And I have East, West and South bracing on the tall side:



As has been pointed out earlier, I might have issues with rot at the base of the 6x6 posts being set directly in cement like they are.

I used 3/8" backer rod between the panels and siliconed the gaps as I installed the panels. I get a few drips during heavy rain, but it has held up well over the last 2 years since I installed it.

If I do any more pole barns like this, I would see if I could locate something like this to seal the gaps:



I don't need 200 meters of the stuff, which is the minimum order quantity from Alibaba. If anyone knows a good source for that molding, I'm all ears.

Let me know if you have any other questions and I'll be happy to try to answer them.

 

[fromport]

The panels are attached via cone nuts and stainless 1/4" bolts with insulated washers on the panel side:

View attachment 111152

The rails of superstrut is bonded together:

Afaik the NEC wants you to bond the panels to the rails and make that all grounded.
Why did you choose to insulate the panel frames from the unitstrut?

 

[SilverbackMP]

@ArkRob I used 3/8" backer rod between the panels and siliconed the gaps as I installed the panels. I get a few drips during heavy rain, but it has held up well over the last 2 years since I installed it.

If I do any more pole barns like this, I would see if I could locate something like this to seal the gaps:

View attachment 111156

I don't want 200 meters of the stuff, which is the minimum order quantity from Alibaba. If anyone knows a good source for that molding, I'm all ears.

Let me know if you have any other questions and I'll be happy to try to answer them.

Why not just use regular barn metal for a roof and use the mounts designed for that? It’s what I was planning for something similar…and then decided I don’t trust panels being on any roof in the country ($6k of mouse chewed wire damage on one my vehicles. And they are a constant battle with the other vehicles. Decided I don’t want equipment under high voltage DC).

 

[crazydane]

The panel frames are making direct contact with the superstruts. But yeah, the NEC would probably not consider that enough. All the panels have pre-drilled holes in the frame that I could use to ground them all, but with 60 panels, that would be a huge pain. I used 1/4" stainless steel EPDM bonded sealing neoprene rubber washers to prevent a metallic reaction between the panel aluminum frame and the stainless steel. I forget where I picked up that would be a bad idea. Been a couple of years.

 

[crazydane]

Why not just use regular barn metal for a roof and use the mounts designed for that? It’s what I was planning for something similar…and then decided I don’t trust panels being on any roof in the country ($6k of mouse chewed wire damage on one my vehicles. And they are a constant battle with the other vehicles. Decided I don’t want equipment under high voltage DC).

I'm cheap and didn't want the additional expense of a 22' x 48' metal roof, plus the panel hardware that I would then also have to get. furthermore, I would not have been able to get to the wiring which was a huge pain on my shop mounted panels when I was running micro inverters. Having direct access to the panel wiring like I do on my ground mount arrays, is a big plus to me.

I have been lucky and not had any issues with rodents, but I have cats that likes them, so maybe that's why.

 

[SilverbackMP]

I'm cheap and didn't want the additional expense of a 22' x 48' metal roof, plus the panel hardware that I would then also have to get. furthermore, I would not have been able to get to the wiring which was a huge pain on my shop mounted panels when I was running micro inverters.

I have been lucky and not had any issues with rodents, but I have cats that likes them, so maybe that's why.

Yeah the micro inverter part makes a lot of sense.

I was going to go with a full on equipment shed with less slope on the roof to get it a little more room to get cabbed utility size tractors or big mini exs inside and room for assorted attachments. Still might, but I am paranoid about fire.

We have lots of owls, plenty of snakes, and Boston terriers, but they don’t seem to make a dent.

 

[fromport]

The panel frames are making direct contact with the superstruts. But yeah, the NEC would probably not consider that enough. All the panels have pre-drilled holes in the frame that I could use to ground them all, but with 60 panels, that would be a huge pain. I used 1/4" stainless steel EPDM bonded sealing neoprene rubber washers to prevent a metallic reaction between the panel aluminum frame and the stainless steel. I forget where I picked up that would be a bad idea. Been a couple of years.

Each panel frame and the array mounts should be tied together electrically for ground.
Code requires a connector to any part that is "mechanically separate" and that means you aren't supposed to rely only on mounting bolts/clips to make the conductive connection.

I have been using put these kind of things between the panel and rails :

https://www.yanglinxm.com/stainless-steel-solar-panel-grounding-earth-clips_p39.html

 

[crazydane]

Those are very cool clips! Not sure I can apply those after the fact since I already installed the panels. Loosing each pair of adjacent bolts and slipping one of those under the frames is going to be much more involved than just running short jumper cables between the frames. But for any future superstrut based arrays, I'll definitely do something like that.

All my regular ground mounted arrays are using Ironridge hardware and afaik, the bolts that tie the panel frames to the aluminum rails don't require additional hardware. These are what I used for those:



I did just call in a workorder with the poco to have new 400A service installed at the shop building. Cost is $8.17 per foot regardless of 200A or 400A service. They will give me a meter base and I have to dig the trench, which is fine since I have a backhoe with a narrow 6" bucket. The run from the pole to where I want to new meter base is right around 150', so about $1,250 total, which isn't too bad.

 

[AntronX]

If you decide to go offgrid look into used EV battery packs on ebay. Some model 3 packs can be had for <$100/kWh.

 

[Hedges]

Diagram looks functional now. The issues and missing things I note are:
Load-shed relays where needed.
Shouldn't have more than 26 kW of SB connected to SI, while on-grid.
Is generator transfer switch instant? Or can it provide 5 seconds "off" time on output before connecting to other source?

That way, the Shop and House sub-panels are going to take what they want before any excess solar production is pushed through the SIs back into the grid, so WAY less than 54A x 4. Too bad about the communications, but since the SIs regulate the frequency and that SBs sync to that to regulate the power, I should be fine, right?

I could always kill the breakers for some of the SBs if I loose power during the middle of a bright sunny day, so not produce an excessive amount of power that I can't consume. That would keep the frequency from going too high and maybe keep everybody happier?

Frequency shift by SI will only happen when disconnected from grid. Under those conditions, SB wattage can be 2x SI wattage, according to SMA. I don't know if that is a hard limit, or depends on how fast loads are added and turned off.

When connected to grid, SB wattage is limited to 56A at 120V per SI. I don't know if export limit, implemented by Speedwire, is fast enough to comply with that. Preferable I think to limit connected SB to that number.

You could use manual interlocked breakers to move a sub panel with SB from direct on grid to on SI.
Any transfer of a grid interactive inverter (SB or SI) between two AC sources (e.g. generator/grid, or SB transfer grid/SI, must have 5 seconds "off" time, to avoid connecting out of phase while inverting.

A relay in SI can be programmed to show when on-grid. That, and possibly "generator" vs. "grid" signal, could be used to control a relay enabling/disabling the path from interlocked breakers to SI.

If I add East/West facing strings to my 7 unused MPPT inputs, you're saying I would be better off doing, say 12 facing East and 12 facing West parallel them up, and then connect to input A or B? In my current install with all 60 cell panels, I like to aim for 400V in each string to maximize efficiency.

So having 12E+12W in parallel on input A or B will be better than 12E and 12W on inputs C on 2 difference inverters?

Separate MPPT for each string will provide highest production. Paralleling two different orientation strings on one MPPT will reduce production, maybe 2% if no issues of heavily shading one string. But could save you maybe 20% in cost through higher utilization of inverter.