A newbies DIY solar install

[jk96]

Going 540', I would consider upsizing the conductors to reduce losses, but more than that, I would think about DC.

If you have no shade, you might want to consider running the DC back to the house, and converting it there, if you can arrange your DC to be as high as possible for your inverter input, but below, 600V. (I think that is from a common insulation limit on wires, but there is also an NEC burial limit for depth, as in you have to deeper if at, or over, 1000V.) You will have lower power loss in the transmission. (Loss goes as current squared times resistance, so doubling the voltage quarters your losses) I would check your local codes and AHJ to be sure.

I'm not a solar expert, but that's the advice we were given, and it made sense to me.

YMMV

All the best,

Peter

That was my initial thought. Run DC back to the house and then pickup the invertors there. If I do that is there any benefit other than looks to having the invertors mounted inside on the basement wall vs on the outside of the home. I know there can be some invertor loss with heat buildup but not sure how much of a concern that is. House wall with service and invertors is east facing.

 

[IXLR8]

Which is going to have the higher currents, the DC or the AC. That should answer your question. If DC currents are going to be higher, inverters at the solar panels, if AC currents are going to be higher, inverters in the house. You want to minimize your losses.

 

[ponytug]

These days most inverters are so efficient that I don't think it makes much of a difference where you locate them. If it were me, I would put them outside on your east facing wall, as I don't see any need to have them protected from weather or temperature.

It would also simplify any future expansion of batteries, transfer switches, more solar...

All the best,

Peter

 

[ning]

Currently working through the application for our electric coop for the approval to grid tie the solar before I finalize the purchase. One question I have for those who have done a ground mount system before is the location of the invertors and auto shutdown box? Did yours go at the panels or house? For my installation it looks like the sequence would be panels to rapid/auto shutdown box to invertors to manual disconnect to utility. Panel location is about 540 feet from the house and invertors are outdoor rated. With that said would it be better to locate the invertors & shutdown box indoors for better efficiency out of the heat? My electrical service enters the house into a utility room in the basement where my electrical panel is located. Just thinking it may be best to also place the shutdown modules and two invertors on the basement wall as well as opposed to outdoors on the house. Would make for a cleaner install as well without all of the components on the outside of the house.

I set something up something similar last year (DIY; purchased from a licensed electrician and paid him for some consulting here and there).

The trench from my ground mount to my shop, where the service entrance is, is about 600'.
My system has 10kW of panels; with the inverter action happening at the array, the cables are running 240V, a maximum of 40A.

With 4/0 Aluminum, I've got a maximum voltage drop of 1.55%. I "sized up" on the cable because if we add an electrc car or two, I may end up adding another 5kW of panels to run on the same cables; 60A on 4/0 for 600' gives 2.32% drop. "Sizing up" probably added $200 which is cheaper than an empty conduit to pull a cable later and much less effort.

My system uses a microinverter for each panel tied to a box at the ground mount; the 4/0 aluminum goes from that box to the switch in my shop (actually, there's a junction box at the end of the trench where the cable hits the shop, and it goes to #4awg through the shop at that point - the #4 for 40' is a negligible voltage drop and it's WAY easier to handle through the bends necessary in that building - and a much smaller conduit). The microinverters together with the main control brains handle rapid-shutdown; there's no separate box for it (all components are Enphase other than the panels).

That switch functions as a microgrid interconnection device (it'll automatically disconnect the grid if it senses bad things or absence, and will regulate the output of the microinverters).

As far as I know, it's not sufficient to have "integrated inverters on the solar panels" (microinverters; typically not integrated to the panel but often attached one to one at the panel) to be able to run solar without the grid. There has to be some intelligence to throttle the solar production to the load. It's possible that this only works with batteries to serve as a buffer.

[Ground vs roof mount: My house is in trees and doesn't have enough good roof for 10kW, let alone a future extra 5kW. Also, the roof is OK for now but would need replacement before you'd do something serious like put solar on it. I also wanted to be able to easily clean the panels, and not have crap fall on them from trees all the time; my ground mount is in the middle of a field with great sun in the winter and even better in the summer. Ground mounts can be pointed and tilted exactly how you want them trivially (once), vs panels are pointed where the roof points on a house roof. Ground is probably easier to DIY, but it's definitely more expensive, and typically you need more panels to get the same kW as a ground mount because of direction and heat... and I already didn't have enough room on the house (2-story house)]

 

[ning]

That was my initial thought. Run DC back to the house and then pickup the invertors there. If I do that is there any benefit other than looks to having the invertors mounted inside on the basement wall vs on the outside of the home. I know there can be some invertor loss with heat buildup but not sure how much of a concern that is. House wall with service and invertors is east facing.

There's good reason to use microinverters (one inverter per panel, at the panel), especially if there's shading or damage on one panel, the entire system can be affected otherwise. There's more up-front cost, but you'll likely get more out of your array overall with them (and the whole thing is more fault-toleratant as well). Some systems (like the enphase ensemble w/ battery & microgrid) require them.
Google "advantages of microinverters", the first few links should all show pros & cons (the con is pretty much just cost).

 

[Wood_Butcher_Dav]

Going on my second year for my 9.2KW system. This is what I know - Have 24 panels on two series circuits which will produce around 500v DC each. These feed the one inverter which feeds a meter base the 240 VAC then feeds main circuit panel in garage. The inverter and meter base are under lean-to on out side of garage. Not sure of Fronius model number. There is some noise/hum when the inverter is operating. My electric co-op is same way costs me around $.13 to buy and $.03 to sell back.
May need electrician to do final hook up, The Co-op also wanted there own solar meter.
Might want to check if there are any State grants for solar. Illinois Shines program save me an additional 40%.

Dave

 

[bmaverick]

These days most inverters are so efficient that I don't think it makes much of a difference where you locate them. If it were me, I would put them outside on your east facing wall, as I don't see any need to have them protected from weather or temperature.

It would also simplify any future expansion of batteries, transfer switches, more solar...

All the best,

Peter

Other than a near lighting strike that takes things out quickly outdoors. Been there already with that even. Blew the lightning arrestor several hundred feet away too.

 

[jk96]

Other than a near lighting strike that takes things out quickly outdoors. Been there already with that even. Blew the lightning arrestor several hundred feet away too.

Made a quick phone call to my installer who is now out of solar but did our business 8 years ago. He says the long run should be AC.

 

[Williy]

Big houses have big electric bills. 4,500 sq/ft finished space, 2 fridges, 2 freezers, 3 kids, washer/dryer that runs non stop, etc etc. System will cover all summer usage and with summer credits may cover winter as well. Even in the swing months when air/heat is not used I average about 65 kwh/day

I have 9 250 watt panels, 4 batteries L16's 4k inverter run frig, computer, tv lights and in summer run two window a/c units and use induction cookers to cook with. e bill was just under $300 now in low $40 range
the two a/c units use together 9.2 amps and together put out 12,000 btu's get an a/c unit from walmart just a 5000 btu unit draws 15 amps. Will be expanding system and will not be grid tie cost too much for nothing
and you from what I have been told can't add power to the power company lines when the power goes out
its a health hazard for the workers.

willy

 

[ning]

can't add power to the power company lines when the power goes out
its a health hazard for the workers.

In California you can't grid-tie without an automatic shutdown or disconnect any more.

In addition, the "smart" meters that most people have won't "run backwards" if you're grid-tied and have excess production and the meter isn't configured for net metering - the utility will charge you for the over production as if it was a draw on the grid (ie if you're producing 5kW and using 1kW, that 4kW extra will count against you)... and you can't get configured for net metering without the disconnects.

(as opposed to the old fashioned meters that weren't digitally and would literally run backwards if you overproduced... and potentially endanger linesmen)