Suggestions for whole house off-grid system?

[JBoffgrid2022]

Hello All,
I am looking for some suggestions for a design/build for a whole house off-grid system with potentially solar/DC powered cooling systems. We recently installed an EG4 6k inverter with LifePower4 battery storage at our camp and really like how the system has performed so far. If I had my preference, I'd like to stay with EG4 for the inverter and battery bank. I was leaning towards getting the 18kpv with powerpro battery banks. Of what I can gather on my own, I would need 36kw of power for the house loads plus whatever I would need for the DC cooling system. I also need to figure out how I can bring power into my house without having 90 solar panels in my front yard...Wifey said that's a no go....

I'm thinking for my solar panels I would have three groups of 30ish panels on ground mounts 150-200 feet from the house, bringing either DC or AC power underground to my main house. Obviously if I went the AC route, I would need to build a separate heated building to safely house the inverters/batteries, keeping them warm during the cold Maine winters, and if possible receive communication via wifi or ethernet (If EG4 KPV has that capability). I know AC has the ability to send power longer distances than DC can which is why I'm leaning in the direction of an outbuilding vs. inverter/battery bank inside the home.

Has anyone found a "sweet spot" for panel / string sizing for the KPV? I've been researching it and have found a few options but I'd take any advice you have at this point!

Any suggestions are welcome, thank you for all your help and advice!

 

[wpns]

I know AC has the ability to send power longer distances than DC can

You may know this, but it’s not true. Higher voltages have lower currents and less loss, so high voltage DC string voltages are your best bet for the long runs. Plus you get to keep your ESS at the house.
Just curious is roof mount is an option?

 

[JBoffgrid2022]

You may know this, but it’s not true. Higher voltages have lower currents and less loss, so high voltage DC string voltages are your best bet for the long runs. Plus you get to keep your ESS at the house.
Just curious is roof mount is an option?

Lol thank you for the tip! I would highly prefer to keep my inverters and battery banks inside my home! With high volt DC wiring, what is the distance I can go up to?
I will need recommendations on wire sizing, best grounding methods for panels/racking, and fuse sizing for the solar wiring.

 

[timselectric]

. I know AC has the ability to send power longer distances than DC can which is why I'm leaning in the direction of an outbuilding vs. inverter/battery bank inside the home.

Actually, quite the opposite.
The most efficient way to cover distance is higher voltage.
And in this case the PV voltage will be the highest.

 

[JBoffgrid2022]

Actually, quite the opposite.
The most efficient way to cover distance is higher voltage.
And in this case the PV voltage will be the highest.

Thank you Tims!

 

[wpns]

With high volt DC wiring, what is the distance I can go up to?

There’s no limit, though I’d probably draw the line at 1000 feet. Depends on your panels, string voltages and currents, and wire size. There’s a tradeoff between wire size and cost too, if you save $1K on wire can you live with 10% loss, for instance?

 

[wpns]

I will need recommendations on wire sizing, best grounding methods for panels/racking, and fuse sizing for the solar wiring.

Again, depends on the details. The 18Kpv can only capture 18KW of PV, though you can oversize the arrays to generate more power off-solar-peak. By the time you install everything you might as well maximize available panel input in case you end up paralleling another 18Kpv (each one can only product 12KW at night) and/or add more PP batteries later. Remember that the 3 MPPT inputs have different input current ratings.

Where did your 36KW requirement (plus cooling) come from?

 

[JBoffgrid2022]

Again, depends on the details. The 18Kpv can only capture 18KW of PV, though you can oversize the arrays to generate more power off-solar-peak. By the time you install everything you might as well maximize available panel input in case you end up paralleling another 18Kpv (each one can only product 12KW at night) and/or add more PP batteries later. Remember that the 3 MPPT inputs have different input current ratings.

Where did your 36KW requirement (plus cooling) come from?

I had done an estimate based on power consumption at our current house which is grid powered only. We have a 200amp service and it seems as though we don't use anywhere near 200amps at any given time which is why i stepped down to 36kw instead of the 48kw that we have now. Again, I am uncertain of the exact amount of power we would need for our new house and probably over estimated the amount of power by a large margin.

Based on consumption of our current house we use 100kwh a day on the summer months and only 40kwh in the winter.

 

[MisterSandals]

current house we use 100kwh a day on the summer months

100kWh / 24h = 4166W continuous around the clock! What are you powering?

 

[MisterSandals]

100kWh / 24h = 4166W continuous around the clock! What are you powering?

In Maine lets say you have 4h of usable solar in the summer. And will assume your power usage is the same rate at all times:

20h running off battery x 4166W = 83320Wh of batteries needed just to get thru 1 night.

83320Wh / 51.2V battery = 1627Ah of 48V batteries (this is a LOT)

Solar for 100kWh in 4 hr = 25000W of solar operating at 100% efficiency.


The solar numbers for winter are worse but the usage numbers are significantly lower too.

 

[JBoffgrid2022]

100kWh / 24h = 4166W continuous around the clock! What are you powering?

I'm sorry, 100khw for the day. 100/24hrs = 4166kw / hr
My thought was this high amount of consumption would only be happening during the summer months when power from the sun would be able to supply power during the day without any battery storage needed. Over night, I would need at the worst case scenario 40kwh of battery storage.

 

[MisterSandals]

I'm sorry, 100khw for the day. 100/24hrs = 4166kw / hr

No, 100kWh / 24h = 4.166kW (which is 4166W as stated)

kW/h is nonsensical. Well a rate (kW) per time period (h) is an acceleration...

 

[JBoffgrid2022]

No, 100kWh / 24h = 4.166kW (which is 4166W as stated)

kW/h is nonsensical. Well a rate (kW) per time period (h) is an acceleration...

Yes, you're absolutely right. 4.166kW x 24hours = 100kWh
Also keep in mind, on my first post I had mention I'm hoping to install a more efficient cooling method than plugging in 6 12K BTU AC units
That is why I have been using 100kwh per day at our current house

 

[MisterSandals]

Yes, you're absolutely right. 4.166W x hours = 4,166kWh

No.
4.166W x 1,000,000 hours = 4166kWh but not sure this applies to anything?

 

[JBoffgrid2022]

Math was never my strong suit..... hahahahaha

 

[MisterSandals]

83320Wh / 51.2V battery = 1627Ah of 48V batteries (this is a LOT)

Just looking at the cost:

Looks like 100Ah 48V EG4 is $1300 x 17 = $22,100
If you want to account for any cloudy days, add $25k more than this for each day of autonomy.

How many EG4's can be put in parallel?

 

[rhino]

There are people like Steve_S on here who lives a lot further north than you and has everything inside a super insulated power shed he built. Also remember the 18kPV can get really loud so if you do put it in your house you want to make sure the noise will not be an issue.

 

[timselectric]

How many EG4's can be put in parallel?

Batteries?
Communicating = 64
Non Communicating = 10 million.

 

[JBoffgrid2022]

There are people like Steve_S on here who lives a lot further north than you and has everything inside a super insulated power shed he built. Also remember the 18kPV can get really loud so if you do put it in your house you want to make sure the noise will not be an issue.

I was planning to put the inverters and battery bank in the basement...Well away from my ears

 

[JBoffgrid2022]

Batteries?
Communicating = 64
Non Communicating = 10 million.

Here is a quote I got recently from Sig. Solar. I need to modify the panel types though. I am thinking I will use two different types of panels for the three MPPT inputs.

 

[timselectric]

$50k makes my wallet cringe.

 

[rhino]

Here is a quote I got recently from Sig. Solar. I need to modify the panel types though. I am thinking I will use two different types of panels for the three MPPT inputs.

You realize you'd have 9 MPPT inputs when you have 3 18kPVs, right?

$50k makes my wallet cringe.

After tax credit will at least drop to $35k.

 

[rhino]

What are you going to be using for mounting structures?

 

[timselectric]

After tax credit will at least drop to $35k.

Still too expensive for me.
But I'm a cheapskate. lol

 

[JBoffgrid2022]

$50k makes my wallet cringe.

I'm weighing the costs of installing this system vs. paying the utilities company to bring in poles or underground wires. So far, my $40-50k solar costs are a LOT less than our local utility company which came in at close to $90k, plus I would have to pay for the cost of using the power.