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

live4soccer7

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I bought SunPower (E20, not P17 series) after searching the topic. No one questioned their quality, only whether worth the premium.

Various panels have different degradation modes. Backsheets that fall apart are a visible one. Tedlar is a premium backsheet, possibly some others are good.

"Potential Induced Degradation" occurs with some (P-type vs. N-type) silicon panels if negative grounded so all cells higher voltage than grounded frame, other type if positive grounded. Some panels are supposed to be highly resistant, others degrade more rapidly (when dust and water make an electrode across glass surface.) SunPower discovered this when their panels were negative grounded so used a model of SMA inverter which allowed selection of negative or positive grounding. Their newer panels are supposed to be highly resistant. My plan for the future is to positive ground Sunpower, negative ground others.

Most newer inverters including Sunny Boy 7.7 are transformerless, so half the panels will be above ground and half below ground. At least that means half as much voltage. But make sure to select panels highly resistant to "PID"

Well this is certainly new information to me. Definitely something to digest and learn.

Great site that I'm putting here for reference that was in your link: https://modulescorecard.pvel.com/top-performers/
 

MarkSolar

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Ground mounting can be tough. We're on glacial till, very hard to dig in. Not sure what your soil is like but make sure you find out before you pick a mount foundation. I ended up using ground screws which worked OK, but there's no magic bullet in tough soil. We have a farm and to be honest I wish I had explored concrete ballast for the foundation, the install was really a lot of work and it was tough to get things plumbed up. I'd agree that a good way to save money is use the highest output panels you can get because ground mounting is expensive. I used Sunmodo, I was happy with the balance between cost and quality. I looked at Iron Ridge, seemed way over designed to me for a residential environment unless you're on a Carribean island in a hurricane zone.

I got my panels from CED Greentech, they have a location in Spokane if that's close to you. They had a large inventory and gave free delivery to a fairly wide area around here (Chicago). I got 425W Q-Cells for $187 delivered. They also carry most of the other stuff you'll want, including inverters, wire, connectors, etc. They're geared toward professional installers but my location was very willing to work with DIYers.
 

live4soccer7

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Ground mounting can be tough. We're on glacial till, very hard to dig in. Not sure what your soil is like but make sure you find out before you pick a mount foundation. I ended up using ground screws which worked OK, but there's no magic bullet in tough soil. We have a farm and to be honest I wish I had explored concrete ballast for the foundation, the install was really a lot of work and it was tough to get things plumbed up. I'd agree that a good way to save money is use the highest output panels you can get because ground mounting is expensive. I used Sunmodo, I was happy with the balance between cost and quality. I looked at Iron Ridge, seemed way over designed to me for a residential environment unless you're on a Carribean island in a hurricane zone.

I got my panels from CED Greentech, they have a location in Spokane if that's close to you. They had a large inventory and gave free delivery to a fairly wide area around here (Chicago). I got 425W Q-Cells for $187 delivered. They also carry most of the other stuff you'll want, including inverters, wire, connectors, etc. They're geared toward professional installers but my location was very willing to work with DIYers.
Thank you very much for the information. When did you buy our panels? What size system did you install and what other ground mount options besides iron ridge did you explore? I was also told the sunmodo is what an installer around here uses. I appreciate the specifics you shared. Again, very helpful.

edit: I just reached out to CED Greentech to see if they can do that for those panels. I'm really hoping they say yes. I feel decent about the hanwha panels and the output is high, so it should make my design a little cheaper that way (wiring from arrays to inverters and the ground mount being smaller physically.
 

MarkSolar

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Thank you very much for the information. When did you buy our panels? What size system did you install and what other ground mount options besides iron ridge did you explore? I was also told the sunmodo is what an installer around here uses. I appreciate the specifics you shared. Again, very helpful.

edit: I just reached out to CED Greentech to see if they can do that for those panels. I'm really hoping they say yes. I feel decent about the hanwha panels and the output is high, so it should make my design a little cheaper that way (wiring from arrays to inverters and the ground mount being smaller physically.
I bought my stuff in June and I got things fired up in July. I installed 10kW of panels on a Fronius Primo 7.6kW inverter. I'm backfeeding through my service panel, so that limited me to 7.6kW. I looked at a bunch of ground mount options, including making it myself out of treated posts and unistrut from Home Dumpo. One expensive part in the end is attaching panels to the ground mount in a way that won't damage the edge of the panels and provides a unified ground on the whole installation. Those mounting clamps only fit the proprietary T channel that comes with whatever system you buy and they act like WEEBs to make the electrical path continuous. I could have mounted them on a wood frame, but that would mean digging post holes for concrete which is almost impossible around here. The uplift on ground mounts can be very high, so whatever you put in the ground has to be well thought out. The availability of ground screws is what finally swayed me to go with a vendor that would provide ground screws with their system. I also looked at APA, they carry ground screws as well. One advantage of Sunmodo is that it's trivial to adjust the height of the vertical mounting posts because they telescope into the ground screws. If you have to trim all the tops of the verticals after you mount them, that can be a lot of work. I looked at a number of other ground mount companies, but in the end since CEDGreentech was a distributor for Sunmodo I decided to go with them. Here's a picture:
Panel Installation.jpg
 

live4soccer7

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I bought my stuff in June and I got things fired up in July. I installed 10kW of panels on a Fronius Primo 7.6kW inverter. I'm backfeeding through my service panel, so that limited me to 7.6kW. I looked at a bunch of ground mount options, including making it myself out of treated posts and unistrut from Home Dumpo. One expensive part in the end is attaching panels to the ground mount in a way that won't damage the edge of the panels and provides a unified ground on the whole installation. Those mounting clamps only fit the proprietary T channel that comes with whatever system you buy and they act like WEEBs to make the electrical path continuous. I could have mounted them on a wood frame, but that would mean digging post holes for concrete which is almost impossible around here. The uplift on ground mounts can be very high, so whatever you put in the ground has to be well thought out. The availability of ground screws is what finally swayed me to go with a vendor that would provide ground screws with their system. I also looked at APA, they carry ground screws as well. One advantage of Sunmodo is that it's trivial to adjust the height of the vertical mounting posts because they telescope into the ground screws. If you have to trim all the tops of the verticals after you mount them, that can be a lot of work. I looked at a number of other ground mount companies, but in the end since CEDGreentech was a distributor for Sunmodo I decided to go with them. Here's a picture:
View attachment 60575
Fantastic information yet again. I feel like I might be getting somewhere now. A panel supplier, ground mount setup that you're suggesting and one I was already considering, etc... How do you like the primo inverter? I was originally looking at SMA Sunny boy, but I'd just need so many of them. haha. If CED comes through with close to the same panel pricing as you then I'm thinking of doing somewhere between 30-40kw. That would put me at 5 7.7kw sunny boys or 2-3 primo inverters.

I would like to keep the possibility of battery backup in the future, so I'm not sure which would be the better option or if there is another better option all together out there. I don't really want to go with a super cheap chinese inverter that will likely go bad prematurely.
 

wattmatters

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854
That would put me at 5 7.7kw sunny boys or 2-3 primo inverters.

I would like to keep the possibility of battery backup in the future, so I'm not sure which would be the better option or if there is another better option all together out there.
Fronius have much larger capacity inverters but they are all 3-phase.

I don't think they sell their hybrid inverters in the USA. That would have helped as there are a couple of compatible batteries which connect into the hybrid inverter.

The new Gen24 inverters are pretty cool and can provide battery-less backup (while there is sufficient PV output) but I don't see them on the Fronius USA website. Might be worth checking in with Fronius to see if/when they plan on offering hybrid models in the US. The largest hybrid single phase model is 6kW.
 

live4soccer7

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Is it possible to add batteries with the Primo down the road or does the inverter HAVE to support that. I'm sorry for my ignorance on this one.
 

wattmatters

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Is it possible to add batteries with the Primo down the road or does the inverter HAVE to support that. I'm sorry for my ignorance on this one.
Not directly to the Primo. To do that (no matter the brand of inverter) it would need to be a hybrid inverter. Fronius have hybrid inverters but not in the US AFAIK.

You can certainly add batteries, pretty much as much as you like (to a point), they'll just need to be AC coupled / have their own inverter.

When designing a future battery system you'll need to take a few things into account, in particular what features you expect of the battery system.

What is its main purpose? Reducing grid imports vs grid outage protection or both? The solutions vary depending on which you are looking for.

In your case there's no financial benefit in storing energy, indeed it will cost you money to charge and discharge a battery because there are losses in the battery charge-discharge round trip, energy that could have been exported instead for a 1:1 credit.

So I can only assume you want something for outage coverage.

Then it's a matter of specifying what your backup power should cover, e.g. which appliances are deemed critical/necessary to operate during outages, how much power they will use, and for how long do you want to be able to provide coverage for? There are various solutions to suit different scenarios and depending on what you want it can get a bit complicated.

Options include:
- Grid tied battery system
- Grid tied battery system coupled with grid tied PV system which can self isolate from the grid and operate independently (this is one for the pros)
- Off-grid battery system which can supply power to the premises via a transfer switch. Battery can be charged via grid power or with an off-grid PV array and/or generator.
- Forget about a battery and just have a generator for backup, with power supplied to premises via a transfer switch.

When I started out on my power backup journey, I progressed from small loaner generator and extension cords, to having a power inlet connected to a transfer switch in my main circuit board into which I could connect my 3kW Yamaha inverter generator. More recently I built an off grid battery/solar system which now feeds the same transfer switch, which supply up to 4kW, while the pre-loved sealed lead acid batteries can keep us going for 6-8 hours on battery alone (going to double that soon) and longer because of the 2.2kW off-grid array feeding that system as well. And it can also accept a generator input. 2 hours of generator operation will provide enough charge for 8 hours of backup.

I used pre-loved stuff to build most of it except for the all-in-one inverter and connection components necessary. My 11kW grid tied system goes off line during grid outages (as it should). Grid tied batteries are just not financially viable for us, even though my grid import tariff is 2.5 times my solar PV feed in tariff - it's still not even close to enough of a tariff differential for a grid tied battery to make sense.
 

Hedges

I See Electromagnetic Fields!
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Mar 28, 2020
Messages
8,365
Fantastic information yet again. I feel like I might be getting somewhere now. A panel supplier, ground mount setup that you're suggesting and one I was already considering, etc... How do you like the primo inverter? I was originally looking at SMA Sunny boy, but I'd just need so many of them. haha. If CED comes through with close to the same panel pricing as you then I'm thinking of doing somewhere between 30-40kw. That would put me at 5 7.7kw sunny boys or 2-3 primo inverters.

I would like to keep the possibility of battery backup in the future, so I'm not sure which would be the better option or if there is another better option all together out there. I don't really want to go with a super cheap chinese inverter that will likely go bad prematurely.

Do you have 3-phase? If so, a number of larger inverters available, including from SMA. But some are higher voltage, would need transformers if you have 120/208Y

If your grid-tie inverter has the UL-1741SA feature "Frequency-Watts", then it should work with Sunny Island (or other) battery inverters that use frequency shift to control their output.

I used Unirac ULA mounts.


If you split your 25kW of panels into two arrays with 90 degree angle between them (e.g. 10:00 AM and 4:00 PM sun), the peak output will be about 0.7x has high, about 17.5kW. Power curve will be more broad, more hours production. Total watt hours produces will be something less than if all oriented South, so over-paneling a bit more would be good.
 

live4soccer7

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Messages
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Not directly to the Primo. To do that (no matter the brand of inverter) it would need to be a hybrid inverter. Fronius have hybrid inverters but not in the US AFAIK.

You can certainly add batteries, pretty much as much as you like (to a point), they'll just need to be AC coupled / have their own inverter.

When designing a future battery system you'll need to take a few things into account, in particular what features you expect of the battery system.

What is its main purpose? Reducing grid imports vs grid outage protection or both? The solutions vary depending on which you are looking for.

In your case there's no financial benefit in storing energy, indeed it will cost you money to charge and discharge a battery because there are losses in the battery charge-discharge round trip, energy that could have been exported instead for a 1:1 credit.

So I can only assume you want something for outage coverage.

Then it's a matter of specifying what your backup power should cover, e.g. which appliances are deemed critical/necessary to operate during outages, how much power they will use, and for how long do you want to be able to provide coverage for? There are various solutions to suit different scenarios and depending on what you want it can get a bit complicated.

Options include:
- Grid tied battery system
- Grid tied battery system coupled with grid tied PV system which can self isolate from the grid and operate independently (this is one for the pros)
- Off-grid battery system which can supply power to the premises via a transfer switch. Battery can be charged via grid power or with an off-grid PV array and/or generator.
- Forget about a battery and just have a generator for backup, with power supplied to premises via a transfer switch.

When I started out on my power backup journey, I progressed from small loaner generator and extension cords, to having a power inlet connected to a transfer switch in my main circuit board into which I could connect my 3kW Yamaha inverter generator. More recently I built an off grid battery/solar system which now feeds the same transfer switch, which supply up to 4kW, while the pre-loved sealed lead acid batteries can keep us going for 6-8 hours on battery alone (going to double that soon) and longer because of the 2.2kW off-grid array feeding that system as well. And it can also accept a generator input. 2 hours of generator operation will provide enough charge for 8 hours of backup.

I used pre-loved stuff to build most of it except for the all-in-one inverter and connection components necessary. My 11kW grid tied system goes off line during grid outages (as it should). Grid tied batteries are just not financially viable for us, even though my grid import tariff is 2.5 times my solar PV feed in tariff - it's still not even close to enough of a tariff differential for a grid tied battery to make sense.
Yeah, I may go generator then down the road if "rolling blackouts" become a frequent thing. I'm not doing the solar system for those reasons. It was more of an after thought.
 

live4soccer7

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Messages
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Do you have 3-phase? If so, a number of larger inverters available, including from SMA. But some are higher voltage, would need transformers if you have 120/208Y

If your grid-tie inverter has the UL-1741SA feature "Frequency-Watts", then it should work with Sunny Island (or other) battery inverters that use frequency shift to control their output.

I used Unirac ULA mounts.


If you split your 25kW of panels into two arrays with 90 degree angle between them (e.g. 10:00 AM and 4:00 PM sun), the peak output will be about 0.7x has high, about 17.5kW. Power curve will be more broad, more hours production. Total watt hours produces will be something less than if all oriented South, so over-paneling a bit more would be good.
Unfortunately, I do not have 3-phase at my location. I wish I did.
 

MarkSolar

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Mar 3, 2021
Messages
189
How do you like the primo inverter? I was originally looking at SMA Sunny boy, but I'd just need so many of them. haha. If CED comes through with close to the same panel pricing as you then I'm thinking of doing somewhere between 30-40kw. That would put me at 5 7.7kw sunny boys or 2-3 primo inverters.
I'm happy with Fronius. I only chose it over the SMA because Fronius has a higher input current which allowed the string configuration I had. As I recall it also has a slightly wider operating and tracking voltage. CEDGreentech would have been able to offer a bit bitter discount on SMA, the Fronius was just a better fit for my config. Call me old fashioned but the other thing I liked about the Fronius is it has a cooling fan, I like heat sinks that are cooled by a fan. However the fan could be annoying depending on where you put the inverter. Ours is on the barn wall so it's no worry. But if you put it in the garage and you happen to have your workshop out there, I think it might bother you.

You might think about doing your install in stages. Do one inverters worth of panels and see what you learn. If I had it to do over there are some things I'd do differently based on what I learned the first time.
 

MPRanger

Beefield, GA 30461
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May 21, 2021
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Location
Beefield Georgia
With the way my grid tie works, time of day is irrelevant. I know how much power I use and it will not go down. With the federal solar incentive and WA's sale tax exemption for solar, it is wisest IMO to go as large as I can afford and am allowed to by the utility company. I'll use the power. If not all of it in the first year or two, I will increase my consumption as well as the years come.
I thought perhaps you were doing a complete system including batteries. Building a battery bank depends on the 26 hours you are not getting max solar production each day. If you are using 25kW during the 6-8 daylight Jowers you are in a small percentage of residential users in America.
 

live4soccer7

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Our grid tie is a 1:1 import/export, so production time and usage time do not matter in my case.
 

live4soccer7

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I'm happy with Fronius. I only chose it over the SMA because Fronius has a higher input current which allowed the string configuration I had. As I recall it also has a slightly wider operating and tracking voltage. CEDGreentech would have been able to offer a bit bitter discount on SMA, the Fronius was just a better fit for my config. Call me old fashioned but the other thing I liked about the Fronius is it has a cooling fan, I like heat sinks that are cooled by a fan. However the fan could be annoying depending on where you put the inverter. Ours is on the barn wall so it's no worry. But if you put it in the garage and you happen to have your workshop out there, I think it might bother you.

You might think about doing your install in stages. Do one inverters worth of panels and see what you learn. If I had it to do over there are some things I'd do differently based on what I learned the first time.
I'm hoping to hear back from CED today on the 425w panel pricing. I don't think the fan will be a bother. The inverters will be outside under an eve near my heatpump which pretty much runs all the time anyways.
 

live4soccer7

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@MarkSolar This will be my first solar install and possibly last unless I add more down the road or help a friend. Any tips? I want to do it all at once so I can get it installed and take advantage of all the incentives which help with the cost at the end of the day.
 

wattmatters

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854
Any tips?
Add consumption monitoring.

Fronius have a meter which is integrated with their system. It will need a data cable to connect to the inverter (well the data manager card inside the inverter - make sure your inverter has one - it's standard where I am but the US product range is different).

You'll also want either a strong wifi signal at your inverter or run a data cable from your router to the inverter.


The meters they use in the US have a different form factor to ours but functionally the same from a data POV.
 

wattmatters

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My grid tied system was installed by an accredited solar PV installation company (they have to be by law here), so much of the thinking was done by them after I outlined a range of things I wanted, although I have also done a lot of thinking since.

One thing I would add is to check the MPPT current and voltage limits for your chosen inverter(s) as this will determine the panel configuration you can run. Fronius inverters often have different current limits for each MPPT and so array configuration needs to account for that. Some current clipping is fine, so it's not something to completely avoid as it usually only happens at times of best solar conditions and is more than made up for at other times.

Fronius have an excellent configuration tool to help with this:

I've no idea what local regulatory requirements you have for high voltage DC set up, so get to know them. Here rooftop installs (I know yours is ground mount) may not exceed a coldest local temperature Voc of 600V. There's talk of raising that to 1000V but for now we have to factor in this additional constraint. We also have some dumb regulations about where DC isolators must be placed (by law we have to have DC isolators on the roof - which ultimately become a fire hazard).

So really it's just a case of knowing your local regulations on these things so you comply and are safe. High voltage DC at current is scary stuff and unlike AC it presents very hard circuit to safely break.
 

live4soccer7

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Thank you again for the great information. I will have to apply for permitting for the local install, at which time I will also find out about additional things that may need to be done. This will be the final step before actually beginning to purchase things. I am still waiting to hear back from CED. I want to get an idea cost based on what they say so that I can then make a plan and submit it to the local county for permitting.
 
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