Off grid solar 5x10Kw Networked Design Ideas

[magnet creek]

I am looking for some help in designing an off grid system for 5 off the grid Cabins. All the Cabins will individually have 10kW solar with an 10kW Growatt inverter and LifePo4 20kWh battery storage.
I was wondering if it would be possible to "network" the cabins, so that they would share solar and battery power. So if one cabin gets used more, it uses power from neighboring cabins that are not used or have better solar production. The cabins are relatively close to each other.
Any ideas for such a system design would be welcome; I am especially interested in the "power management" aspects.

 

[Texican]

how close is each cabin ?

 

[magnet creek]

The cabins are fairly close together 60'-100'

 

[timselectric]

Too far for battery voltage to travel.
AC coupling is the only viable option. Which means possibly different AIO's.

 

[Rocketman]

I have no idea how to do it automatically…

But it would not be hard to do manually. My thoughts are with Victron Quattro investors, they have two inputs, have one of those inputs set at like 15 amps input, that input cable plus an output circuit wire both run to a distribution point, where they all go.

Then if cabin 1 needs more power and cabin 3 has extra, plug the power 3 into the power 1 circuit and set a manual timer or just leave on.

I am sure it could be done automatically- but I have no idea how.

 

[sunshine_eggo]

I am looking for some help in designing an off grid system for 5 off the grid Cabins. All the Cabins will individually have 10kW solar with an 10kW Growatt inverter and LifePo4 20kWh battery storage.
I was wondering if it would be possible to "network" the cabins, so that they would share solar and battery power. So if one cabin gets used more, it uses power from neighboring cabins that are not used or have better solar production. The cabins are relatively close to each other.
Any ideas for such a system design would be welcome; I am especially interested in the "power management" aspects.

Networking not viable as presented.

Other options:
6th structure containing all 5 cabin power systems feeding AC to the 5 cabins.
The entire power system in one cabin feeding AC to the 5 cabins.
Two power systems every other cabin and feeding AC to a second cabin (with 5 cabins, one would be standalone).

The only way to actually network them is to connect the inverters via a data cable, and I strongly doubt the data cable can be 60-100'.

 

[Shimmy]

6th structure containing all 5 cabin power systems feeding AC to the 5 cabins.
The entire power system in one cabin feeding AC to the 5 cabins.
Two power systems every other cabin and feeding AC to a second cabin (with 5 cabins, one would be standalone).

This is pretty much the reality. It is possible to do what you want to do "natively" with a supplemental controller, but it would not be reliable or nearly as effective as you might hope.

The controller would need to evaluate battery state, load, and PV for each cabin centrally, and adjust grid support levels based on that, but adjusting values at more than 5second intervals is impossible. You would likely be limited to "centralizing" about 60% of the power and the balance would need to be responded to real-time by the local inverter (you need to make sure that the power put into the "grid" is fully consumed somewhere).

There might be a permutation with a 6th system doing the grid forming or grid sinking, but it isn't going to be easy.

 

[magnet creek]

Thanks for the ideas.
The "problem" with the "6th structure", some kind of central power hub is that it is static. A static infrastructure is great if you know exactly what you are building (which I do not). would love for the network to be agile. you start with 2 cabins and keep adding cabins that would all have a shared AC infrastructure. That way the system grows as the project grows.
It seems like a AC coupled system is the way to go to a certain extend . Something like this but with multiple (cabin) sites tied together on the AC side?
Maybe I should look at systems the public utility companies use for networked (vs radial) design power distribution....

 

[Rocketman]

Just build the “power shed” in the middle - with each cabin getting its power from the power shed. Make the power shed big enough for the final project.

Use modular equipment that can be added upon. Then all cabins are on on a big battery and inverter.

Design the system now as if all cabins were built, then pare it back down to your first cabin.

Adding a cabin… run 120v wires from power shed to cabin, and Solar wires from cabin back to power shed. Need a new mppt? Add it? Need more inverter power - another another. Need more batteries? Add them. You may find as you add cabins you don’t need everything.

 

[OzSolar]

AC Coupled is likely the only way to go.

Just in case you haven't already seen this from SMA

 

[Shimmy]

If you can't centralize things, I would go for a hybrid (grid forming) inverter with battery at the first cabin, and then microinverters on the other cabins as time goes on. Then, you add off-grid inverters with small batteries in each of the other cabins (no connection to the PV). That gives you distributed generation during the day from day 1, and the local batteries (when added) gives you local generation at night. You can't share battery capacity beyond the grid-forming battery, but just a small battery in each cabin will limit "stranded" capacity some.

Expecting more than that will be a challenge.

 

[magnet creek]

Thanks for the ideas. So basically the advice is to Create one Power hub that feeds a Split phase grid to the individual cabins and the cabins each have there own PV's/ Batteries with ~1/2 reserve. I'll look into the idea of increasing a cabin (site) in the middle somewhere that acts as a power hub and runs the grid to the other cabins. I have been thinking about adding Hydro as well (I have a creek on the property with about 300' of head. So increasing the size of the PV's and Batteries on the "power shed" and connecting Hydro there may be the best option. I could also install one (larger) generator there to act as central backup, as opposed each cabin having a separate small generator.

 

[Shimmy]

Definately a single generator at your "hub" location.

Personally (as I said above), I would use microinverters for the solar in the remote cabins just tying into the "grid", and the local hybrid inverter would just have a battery attached. The microinverters can easily "follow" the main inverter with frequency response. The local inverter can easily follow the load between its input AC and battery. Without two independent AC/DC converters it gets hard

The only non-standard thing you need to add is something to automatically schedule the charging of the remote cabins' batteries when the main battery is approaching full charge. It might be possible to do with native voltage and frequency "grid" settings, but that would be really complicated to troubleshoot and commission.

 

[magnet creek]

Maybe a power switch like the Enphase Enpower power switch could be configured to help distribute the load ? I am sure it is normally set up to act as a "binary" controller, i.e. if there is no power from the grid it switches to battery use. I am not sure if anybody makes a programmable version of this for 100% Off grid. Maybe this could work: https://moeshouse.com/products/moes...r-wind-system-ats?_pos=2&_sid=0025afd31&_ss=r
@Shimmy, I am curious to hear why you feel so strongly about the remote cabins using Microinverters as opposed to Hybrid inverters. ?

 

[magnet creek]

Below is the design I can up with. 1 "powerhub" with 8kW Solar, 50kwh Lifepo4 Batteries, 2kW Hydro and 500W wind. The Powerhub will for the grid that feeds 6 Cabins that each have 6.5 kW solar and 20kWh Lifepo4 and a 10kW hybrid converter. Curious to hear what you think.
PS It was suggested that I use Microinverters ilo Hybrid inverters but I am unclear what advantage that offers and I am unfamiliar with how to make those charge the batteries for the individual cabins....

 

[brucenolan]

SMA sunny island microgrid watch here:

 

[Shimmy]

The advantage of the microinverters is that they can charge the main batteries. Your cabin solar will be stranded if the unit is unoccupied which was not one of your design objectives.

Avoiding having battery capacity being stranded is harder for a distributed microgrid; you size it small to minimize the impact.

Wind has no economic payback at a sub-20kW scale. Micro-hydro is supposedly economically viable for off-grid, but I have no personal experience.