Arkansan solar farmer

[David Amon]

Hello, all.

I am new to the site, but not solar. My experience is commercial though as I manage a 180 MW solar farm.

I have recently decided to add solar to my home, but so far, the vender I have tried to deal with has left a very bad impression on the residential solar industry, basically forcing me to pay them to do nothing and just get the heck out of my life.

I've started looking at doing it myself, but the paperwork involved in getting on a net metering program makes the process a little harder than I think it should be, but without filing it they won't install a meter that runs backwards. The energy companies like to make it difficult to do DIY systems as if they don't want people pumping power back onto the grid. So far I have collected about 5 kw of solar panels, identified the roof top racking system I want and am considering using Enphase micro inverters. Just not sure if I need the IQ combiner box or not as online info concerning the equipment seems a little scarce.

[bcroe]

After a decade powering my place totally with solar, my advice is use string inverter(s), a pair as a matched set will tell you all you need to know about if the system is working properly. There are many reasons not to use micro inverters on a roof. Ground mounting panels has big advantages, but is initially more costly. If you have a lot of clouds, there starts to be a production advantage to mounting panels on both sides of an E-W facing ground mount as has been done here. Getting the permit can be a problem, there were 4 levels possible when I built. Had a local installer initially do that and install, I did a lot more after that was done. Getting 29,000kWh a year through 15kW of inverters here in northern IL shows the effectivness of these methods. good luck, Bruce Roe

[David Amon]

After a decade powering my place totally with solar, my advice is use string inverter(s), a pair as a matched set will tell you all you need to know about if the system is working properly. There are many reasons not to use micro inverters on a roof. Ground mounting panels...

Wife will not let me do ground mount as she does not want to see them. The building I plan on putting the panels on is 60 X 40 with roof lines facing East and west. Land is flat here in NE Arkansas. Clear views on both sides and I can get about 18 kW per side. Plan on installing a permanent ladder to the roof with a safety line to tie off to. Unfortunately I am limited to 25 kW as a residential customer, but once I open my event venue I might be able to claim Farm which allows up to 300,000 kw or Commercial which I have not seen limits on that.

I have fears with central inverters as my plant uses Central inverters. Now granted the voltage on a string at the plant is 1500 Vdc while in residential if you get to 500 Vdc your getting pretty high. One issue I have at the plant though is fires. I've had bad MC4 connectors melt and start a grass fire and I have also had rodents chew wires and cause a negative to positive short and start a couple other fires. Running DC long distances increase the risk. Granted 1500 Vdc is kind of the top rating for MC4 connectors in the US and I seem to remember the European code on them only allows 1200 V. Yes, we have inline string fuses, but I have yet to see one blow. A DC short prior to the combiner box is just like the arc of an arc welder and I have seen wires burn back 4 feet before finally creating enough distance between them to break the arc. With the Enphase you are running AC and if the AC shorts it trips the breaker and then the loss of an AC signal will shut down the micro inverter as it needs that AC signal to stay on.

[littleharbor2]

With nearly a half million panels at 1500 Vdc I imagine you've seen lots of strange occurrences. Do rodents get incinerated Once the chew through the insulation?

[bcroe]

For openers you should decide on the amount of energy you want to collect per year, then try to build a system to that. My panels are 500 ft from the house where nobody can see them. Size is to maintain 2 buildings with heat pumps year around, and all electrical needs. With a lot of cloudy days, it is possible to compensate with E and W facing panels as used here. Say your permit is for 10kW of AC output. 10kW of panels facing the rising sun will bring inverter up very early. 10kW of panels can be on the same mount facing west. Since only one set is active, both can be wired in parallel in a string system, to a single inverter. As the sun moves E to W, output will gradually shift from the E panels, to the setting sun facing panels. This becomes more adventageous on cloudy days, because with dispersed light all panels become active. The normally small cloudy production will be doubled. This will not work with near flat mounting, panels need to be elevated some 60 degrees from flat to avoid noon overload. Not practical with micro inverters. Panels facing straight E or W works very well here at 42 deg latitude, because the sun rises quite a bit to the south mid summer, and about the same amount to the north mid winter. Check yours. I would like to post a picture, but do not see how with the new software. Fuses will not help with failing MC4 connectors, because panel current is not enough to blow a fuse, even with a short. A fuse is primarily to keep multiple strings from all feeding back to a single string that has shorted (never had one in over 1400 panel years). Another owner here may tell you of having zero MC4 failures by uising NO OX. String wiring along panels has not been a great problem, I did have one deer killed when he bit it. Some 70 ft of buried conduit handle my longer DC runs. I would never recommend 1500V operation (is it legal?) in a residential system. Here strings are limited to 720 series cells, either 12 X 60 cell panels or 10 X 72 cell panels, they all play together well. That gives operation near 320V summers, 420V mid winter, entirely manageable. Several failures over a decade were all in bad wiring connections, none in any danger of arcing or a fire. Do understand, DC string wiring is FAR simpler to a combiner box, than what is required for AC and micro inverters with triple as many connection potential failure points. Also the energy losses are much easier to control at higher voltage, you really ought to go through the numbers for either option. Maintaing % loss requires the square of the amount of copper with voltage reduction, since you need less voltage drop at higher current. The idea of lots of AC connections oudoors means a lot of hadrware, sounds like inviting failures. Keeping the inverter(s) out of the sun and weather is going to be more reliable. good luck, Bruce Roe

[David Amon]

With nearly a half million panels at 1500 Vdc I imagine you've seen lots of strange occurrences. Do rodents get incinerated Once the chew through the insulation?

Most of the time the rodents get mostly vaporized, but as evidence of rodent chewing on other wires will indicate the area is a hot spot for rodent damage. I have spent over $100,000 dollars with Terminix this year alone to kill off the rodents with bait boxes and the rodent activity has significantly decreased over the 2000 acres.

This was not a fun day. It ended up back feeding 5 of the combiner boxes and melting them down as well. The fire company had to respond and I am still dealing with company insurance to getting an RCA completed and start repairs.

Reduced INV FIre.jpg

[bcroe]

E-W Picture

[littleharbor2]

Most of the time the rodents get mostly vaporized, but as evidence of rodent chewing on other wires will indicate the area is a hot spot for rodent damage. I have spent over $100,000 dollars with Terminix this year alone to kill off the rodents with bait boxes and the rodent activity has significantly decreased over the 2000 acres.

This was not a fun day. It ended up back feeding 5 of the combiner boxes and melting them down as well. The fire company had to respond and I am still dealing with company insurance to getting an RCA completed and start repairs.

Reduced INV FIre.jpg

YIKES!! That definitely looks expensive.

[DanS26]

Most large electrical installations have retorquing programs that require EVERY connection to be periodically tested. Just wondering if that is part of your job description.

But back to your home installation.......I use silver conductive grease sparingly on every connection which is torqued to proper specs. Do not confuse with dielectric grease which has completely different electrical characteristics. Never had a connection failure in over 13 years on a 23kW system.

https://www.amazon.com/dp/B09VYD5C4S?psc=1&ref=ppx_yo2ov_dt_b_product_detail s

[David Amon]

Most large electrical installations have a retorquing programs that require EVERY connection to be periodically tested. Just wondering if that is part of your job description.

https://www.amazon.com/dp/B09VYD5C4S...roduct_details

You are correct that are PM program involves retorquing of electrical connections and a lot of the array has to be retorqued on an annual basis or after a significant wind event. Right now, my site has only been in commercial operation for 7 months. Those PM's will be starting to pop up in about another 4 months or so. The larger issue is we have had some issues with corporate strategy and since the plant has been operational I have been the only full time, Technician, Electrician, manager, scheduler, operator, and administrator on site. A lot of my time is spent on NERC and FERC though as well. So right now I spend a fortune on contractors until I can get corporate to staff the site correctly.

[DanS26]

Dollar wise and pound foolish.