Help with Panel & Inverter Choices for a large install

[pvk427]

I have a commercial location with about 250KW/month consumption. I do not have enough roof space to cover all. Below is a sample design from a local company with 370 60-cell panels.
There are about 120 panels facing south (~95% efficiency), about 120 facing west and rest flat or facing east. This design uses SolarEdge 300w panels achieving a system size of 110KW with annual production of 146Mwh. For practical and financial reasons, I am planning to install in parts, and just have south facing panels installed.


Design 370 panels.PNG

I am seeking advice for following issues:
1. Micro inverters vs Power Optimizers(POs). Enphase costs me around $85 extra for each panel when compared to SolarEdge POs. However, I have been reading and comparing outputs on public installs. It seems Enphase produces about 10% more than POs. Am I wrong / Are Enphase worth the extra cost. I only have shading issues in few areas.

2. If I do go with Enphase IQ7+, can I choose 390W 72-cell panels. An installer quoted me that "AC Output of the IQ7+ clips power past 290Watts. While the system would work fine with the IQ7+, you’d be wasting a lot of power." Is it true. If I go with IQ7+, am I limited to 60 cell 325W panels.

3. I found a local installer who lets me provide the panels/inverters. If I buy the panels from sunpal power and get them shipped from China, my cost on the panels is about 40% cheaper than I buying from a US distributor. Has anyone bought from sunpal. Would there be any issues (warranty/quality) if I go this route.

4. Are Qcells good panels. Are they worth the extra price over fob shanghai panels. Sunpal sell both and there is about $45 price difference between these two.

Thank you for taking time to read this and any input you can provide. I appreciate all the help I can get. Thanks in advance.

[J.P.M.]

You're welcome in advance.

As for input, be careful what you ask for.

If I was an unethical installer and read what you wrote here, I'd smell solar ignorance and take you to the cleaners.

I'd suggest you do nothing more until you get yourself informed about the basics of how PV works and its potential as well as, and equally or more importantly, its limitations.

Then, with your newly acquired knowledge, re-examine your goals and consider finding find a reputable professional outfit that does solar design and installation of commercial arrays.

At least get a couple more sets of professional eyes on the R.F.P. you'll need to write up.

Welcome to the forum of few(er) illusions.

[pvk427]

Thanks for the response and caution. Of course I am ignorant about these issues. If I wasn't I would be answering questions rather than asking them

Can you kindly suggest me best resources to learn about how PV works and their limitations. I do want to learn.

Coming back, I am in the state of AR where solar isn't much popular. I don't have access to many professional installers and majority of these installers couldn't properly answer my basic questions. For instance, I know the efficiency 95% doesn't sound right, but that was local installer quoted. The quote regarding Enphase clipping is a direct quote from an installer.

If any of the experts on this forum are able to help with proper design and product selection, I am willing to pay them.

[ButchDeal]

I am seeking advice for following issues:
1. Micro inverters vs Power Optimizers(POs). Enphase costs me around $85 extra for each panel when compared to SolarEdge POs. However, I have been reading and comparing outputs on public installs. It seems Enphase produces about 10% more than POs. Am I wrong / Are Enphase worth the extra cost. I only have shading issues in few areas.

No Optimizers from SolarEdge are more efficient than micro-inverters.
Above you mentioned you were using SolarEdge PV modules 300w each, SolarEdge does not make PV modules, they make optimizers and inverters (the inverters and optimizers do not work without the other).

2. If I do go with Enphase IQ7+, can I choose 390W 72-cell panels. An installer quoted me that "AC Output of the IQ7+ clips power past 290Watts. While the system would work fine with the IQ7+, you’d be wasting a lot of power." Is it true. If I go with IQ7+, am I limited to 60 cell 325W panels.

You can but they will clip. you are not limited to 60 cell but would have to accept the clipping.

3. I found a local installer who lets me provide the panels/inverters. If I buy the panels from sunpal power and get them shipped from China, my cost on the panels is about 40% cheaper than I buying from a US distributor. Has anyone bought from sunpal. Would there be any issues (warranty/quality) if I go this route.

you would have a risk of getting import tariffs which would jack the price back up. You would have to deal with that company for any warranty issues as well.

4. Are Qcells good panels. Are they worth the extra price over fob shanghai panels. Sunpal sell both and there is about $45 price difference between these two.

Thank you for taking time to read this and any input you can provide. I appreciate all the help I can get. Thanks in advance.

QCell are fine but I would consider getting from a US distributor which is going to handle the tariffs for you. They are cheaper in bulk.

[ButchDeal]

Coming back, I am in the state of AR where solar isn't much popular. I don't have access to many professional installers and majority of these installers couldn't properly answer my basic questions. For instance, I know the efficiency 95% doesn't sound right, but that was local installer quoted. The quote regarding Enphase clipping is a direct quote from an installer.

If any of the experts on this forum are able to help with proper design and product selection, I am willing to pay them.

There are several efficiencies. The inverter which micros are around 95-96% SolarEdge is 98.5-99%
Then there is the PV module efficiency which is going to be more like 17-21% with much higher costs for the higher efficiency PV modules.
This solar efficiency is basically the area to production ratio. So getting higher efficiency PV modules does not produce more but you sometimes can fit more on the roof since they are a little smaller.

[J.P.M.]

Thanks for the response and caution. Of course I am ignorant about these issues. If I wasn't I would be answering questions rather than asking them

Can you kindly suggest me best resources to learn about how PV works and their limitations. I do want to learn.

Coming back, I am in the state of AR where solar isn't much popular. I don't have access to many professional installers and majority of these installers couldn't properly answer my basic questions. For instance, I know the efficiency 95% doesn't sound right, but that was local installer quoted. The quote regarding Enphase clipping is a direct quote from an installer.

If any of the experts on this forum are able to help with proper design and product selection, I am willing to pay them.

You're welcome.

I'd start with "Solar power Your Home for Dummies". Although it's mostly for residential, it's a decent primer for the basics. A slightly dated but still useful and free snoop, it's available as an online download. Or, an updated ed. at bookstores or Amazon for ~ $25.

Another "dummies" tome: "Photovoltaic Design and Installation for Dummies" by Ryan Mayfield. Also a bit dated but I think still maybe a free pdf download.

Another: "Solar Electricity Handbook 2017 Edition", Michael Boxwell. ". Free online.

That ought to get your feet wet and also help you to ask questions you already have the answers to which is a good way to find out who's B.S.'ing you. The Enphase quote you reference may/may not be correct. Your knowledge quest will help you to decide the veracity of the statement on your own.

For more stuff Google is your friend: Google "Solar power pdf books".

Knowledge is power. Get some of the first and you won't get screwed while trying to get some of the second via alternate energy sources.

After all that look into something called PVWatts on the net. It's a user friendly model mostly for residential solar applications that can be a useful learning tool. Read the help/info screens a couple of times and make a few runs for a feel/dart throw of what's a possible annual output per installed STC PV kW for an application in your area.

Come back here after the reads and ask questions to help fill in any knowledge gaps your efforts create. Your knowledge quest will put real meat on those questions' bones and make the answers you get more meaningful as well.

Good luck.

[Mike90250]

Does your location require a rapid shutdown system (micro or optimizer) or can you use a plain string inverter and skip the rapid shutdown gear ? Since this is a commercial install, and the RS is mostly for residential rooftop installs.

[pvk427]

Does your location require a rapid shutdown system (micro or optimizer) or can you use a plain string inverter and skip the rapid shutdown gear ? Since this is a commercial install, and the RS is mostly for residential rooftop installs.

All I can find out for now are:
- Disconnect inter-tie within 10 cycles of a service interruption or fault.
- When the operating frequency of the Net Metering Customer's Net Metering Facility deviates from the 60 Hz base, the Net Metering Customer shall automatically disconnect the Net Metering Facility from the distribution delivery system with 0.16 seconds.

Here is the specifications for my site (https://www.entergy-arkansas.com/use..._standards.pdf)

[Mike90250]

Good "- Disconnect inter-tie within 10 cycles of a service interruption or fault." That is a simple Grid tie system, in my eyes, not a de-energize at the panel level. So if you don't have shade on your roof, it's likely you dont need the module level inverters/optimizers They add nothing in good, full sun.

Now the question is, who's going to install it and train you to monitor it ? Larry with a ladder, or Chuck with a truck ? Replace a dud panel in 4 years? You have lots' o panels. Eventually, I'd expect one or 2 to go bad.

Your local code inspector has the final say, but in my eyes, you don't need rapid shutdown.

[ButchDeal]

All I can find out for now are:
- Disconnect inter-tie within 10 cycles of a service interruption or fault.
- When the operating frequency of the Net Metering Customer's Net Metering Facility deviates from the 60 Hz base, the Net Metering Customer shall automatically disconnect the Net Metering Facility from the distribution delivery system with 0.16 seconds.

Here is the specifications for my site (https://www.entergy-arkansas.com/use..._standards.pdf)

Arkansas is under NEC 2017 so you would have NEC 2017 rapid shutdown.
That document is about NET Metering you need to look at your state electric code which will be enforcing the rapid shutdown.

[J.P.M.]

pkv427:

You're out of your depth. If you don't want to learn what's required, hire a professional for their advice, experience and expertise. Getting bits/pieces here will not get you what is needed.

[cobratom]

Maybe start off with your current service coming into the building? Single Phase? Three Phase? High voltage? Are you metered before or after the transformer? Do you have a secondary transformer in the building stepping down say a 480V service to 208/120?
These are all factors that are important starting points.