Hello from Utah / Midwest

[from-nibly]

Hey everyone,

I hope this isn't inappropriate but I'm at the very beginning stages of designing a power setup for a community I'm going to be building starting in the 2-4 years. There are lots of details to figure out and one of them is power. I could really use some help figuring a few things out. Any questions that you can answer would be greatly appreciated. I'm coming from an assumption that I'd be using sol-arks (cause they SEEM straighforward) but I'm open to whatever.

Background:
I'm planning on building a community of up to 10 houses. I'm trying to figure out if it makes more sense to build 1 "plant" for each house, or make a single large power plant in a central community space and distribute the power from there. The 1 "plant" per house seems straight forward enough. Get a sol-ark 15k (or whatever) and hook it up to some batteries and a propane generator, store it all in a shed (venting the generator with a fire safe exhaust, and then do normal electrical work to the house and inside the house.

The large power plant that distributes however...

Self Warning
I'm not an electrical engineer, my brother-in-law is, but he's not a civil engineer. If there are things listed below that should be reviewed/engineered by a licensed engineer please let me know, I don't want to kill myself or anyone else.

So here are the things I'm thinking about

3 phase vs 2 phase
I've heard that 3 phase is a lot easier to balance the load between houses so I think it would make sense to use 3 phase instead of single phase with all the houses/buildings I'm planning. That would probably mean using something like sol-ark 30k

Transmission lines
I've done some rough voltage drop calculations using an online calculator. All the houses should be within 500 feet of a central point where I can put the "plant".
If I use 480v step up/down transformers I should be able to span 500 feet with 2/0 AWG aluminum triplex easy peasy. Those can obviously be pretty expensive new, but I've seen a lot of pretty beefy stuff on ebay used. (is that a good way to get myself killed?)

(120v / 480v) * 125amp = 36amp, which results in a 1.26% voltage drop according to this

Voltage Drop Calculator

This free voltage drop calculator estimates the voltage drop of an electrical circuit based on the wire size, distance, and anticipated load current.

www.calculator.net

According to ugly's electrical reference 2/0 AWG should be able to handle 115 amps (way more than 36 that would be carried)

Question 1:
Am I able to use 1 huge transformer on the plant side of things, hook that up to a distribution box (with breakers) and then send individual wires to each house? Then have smaller transformer at each house to step down the voltage?

Batteries:
One big issue, is that sol-arks, can only have 1 battery bank. I've seen some stuff on this forum about using a separate charge controller for big battery banks, but I feel like I'm missing something.

I think that means that they can only have the maximum of what a single sol-ark can connect, right?

Question 2:

Does that mean I can only distribute 30kw from batteries when the sun goes down even if I have 5 30k's all hooked up?

If so what's the point of being able to hook up 5 sol-arks in parallel to each other?

Question 3:
Am I better off building/designing my own solar setup with things like victron components where everything is separate?

Generator Backup:

For generator backup sol-arks have switching built into them, but similarly to batteries I believe they have some limits.

Question 4:

Can you hook up a generator to each sol-ark when you have 5 or so connected together?


Anway sorry for the wall of text, even if I can only get some answers on a few of these questions I would be extremely greatful.

 

[Q-Dog]

Who is going to be responsible for keeping all of this running?

 

[from-nibly]

Who is going to be responsible for keeping all of this running?

I am. One of the factors in figuring this out is the difference in maintenance between a single power plant, or 10 different ones. The other thing is if something goes wrong with one of the parts, does it bring down everyone or just some of the capacity?

 

[Q-Dog]

I am. One of the factors in figuring this out is the difference in maintenance between a single power plant, or 10 different ones. The other thing is if something goes wrong with one of the parts, does it bring down everyone or just some of the capacity?

With 10 separate systems, when one fails you only have one customer/house pissed off at you.

 

[registered-bum]

The technical aspects can be relatively straightforward as basic engineering and licensing/permitting/certification processes within the AHJ (authority having jurisdiction).

Societal issues - There's an aspect of direct responsibility as well:
For the individual systems - if I as a homeowner/occupier overload my individual system, then I have the consequence of potentially no power (burned out the inverter or depleted my batteries).
For a shared system - if I used up 50% of the total system capacity - is it obvious to the community who is splurging on power vs being conservative? Social strictures and community values/culture may be a strong influences on how the 'commune' comes to own their individual responsibilities in the use of shared resources.

Who plays the heavy and has to come around and enforce rules and guidelines about abuses and excesses?
"Jim yelled at me 'cause I used too much power - dangit, I hate that Jim."

So while the engineering approach says the centralized/shared power generation is logically more efficient, the selfish human aspects may favor the individual systems.

... and yes, one of my superpowers is that I often overthink things.

 

[Mr Hairylegs]

10 separate systems, hands down.

It will be far more simple to design, install, and maintain. I am part of a family off-grid community of 5 separate homes. We went down this road of separated vs. centralized systems. A centralized system will be far more complex and expensive to build overall. You can certainly get batteries cheaper (buy a 1 megawatt or .5 megawatt battery system) to service multiple homes at a lower than average cost per watt) but by the time you add all of the needed components for voltage regulation, wiring etc. and you will be a net higher cost for construction. Maintenance will also be a bigger deal. More complex, more expensive, and if one component fails all homes get affected. You will also have to have an HOA to ensure costs are shared equitably. We opted for separated systems in the end and we are all super happy with the results.

Separate systems are the way.

 

[from-nibly]

Thanks for all of your responses. A tiny part of me wishes I knew enough to be able to see how the math works out, but I have so many other things to do to plan this community I think I'll probably just leave it here. Thanks especially to @Mr Hairylegs It's good to know I'm not the only crazy person on this forum.

Edit:
I'm going to do separate systems for each building