Off grid cabin interior Alaska setup advice

DIY
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1

Hi, I was wondering if you could help me out on my solar setup? I’m planning an off grid log cabin build in interior Alaska with a solar system and a backup diesel generator. The backup diesel generator will be used only to recharge the batteries of the 48v battery bank. Yes, there will be a wood stove.

I will be ordering 60 AIKO STELLAR 2N+78 (AIKO-A805-GRH78Dw) 805W each solar panels total nominal power output of 48,300 watts (48.3 kW).

I will be ordering 6 Coremax 48v 400ah LiFePo4 20 kwh battery storage System for a total of 120kWh usable storage.

The backup diesel generator will be a Equipment Source Inc ESI Alaska KPG-06 Arctic Re-Air enclosure diesel generator with a 500 gallon tank.

I need your professional advice on what inverters and MPPT controllers you recommend to fully exploit this system during winter months and also during summer months to avoid clipping and wasted energy and to try to create as much full autonomy as possible from the diesel generator and go the longest intervals without having to recharge the batteries.

Total Daily, Monthly, and Annual Energy Use

Load Daily (kWh)
Refrigerator 0.575
Freezer 0.375
Well Pump (Grundfos + Shurflo) 1.500
Water Heater (Toyo OM-122DW) 0.027
Lighting (LEDs) 2.500
Washing Machine 0.203
Electronics (Starlink, laptops, phones) 0.300
System Standby (Cerbo, MPPT, etc.) 0.100
Total 5.58 kWh/day

  • Monthly average:

    5.58×30 = 167.4 kWh/month

  • Annual total:

    5.58×365 = 2,036.7 kWh/year

  • There will be no clothes dryer, HVAC, electric stove/oven. But, I would like a over built solar system to power through the long dark winter months in interior Alaska and to try to get at least 20+ straight days autonomy of battery use before the diesel generator kicks in if that’s possible to be as independent from the diesel generator as possible to save as much money as possible, also less pollution. What do you recommend for inverters and MPPT controllers? I would like a inverter/s that have a very low idle draw. I’ve thought about the EG4 and Sol-Ark but their inverters have a very high idle draw, their daily idle draw is higher than the daily kwh of the refrigerator and freezer combined.

I’d like a system that can sync up with the diesel generator with auto-start and automatically turn the block heater on when the batteries drop to 30%, and the generator turns on to recharge the batteries when the batteries drop to 20%. (Gives the generator enough time to warm up before it turns on to recharge the batteries.)

I will be having built a underground insulated ICF root cellar at least 10 feet under ground that will also be heated with solar powered air heater at 75 degrees from Artica Solar. It will be fully independent from the battery bank. Over the root cellar will be a multi-purpuse utility shed to house the diesel generator. The batteries and inverters will be down in there in the heated insulated root cellar…

What do you recommend for a setup?

2

What is the peak load?
Will the system be one, split or three phase.

Generally:
cover peak load by a MultiPlus 2 (MP2)
Use RS450/200 (10 kWp) to charge battery from PV.
Use a small Fronius for direct usage of AC-PV.
Use Ekrano GX or Cerbo GX as control system.
The Victron control center support auto generator start/stop.
Use Lynx Distributors for DC busbar.

Couple check your battery’s BMS can communicate with Victron and can be stacked.
Maybe go vir bigger batteries with 16 or 32kWh each pack.

Use MPPT Calculator - Victron Energy to calculate best string configuration with your panels and Victron MPPT/RS.

Prefer daisychaining with VE-CAN over VE.Direct.

Plan some vertical wall-mounted south directed panel that are protected from snow and get light refracted from snow.
Think about automated snow removal.

3

Thanks for the reply…

The peak load is around 3,370W

split-phase (120/240V) 48v battery bank.

Can only one MultiPlus inverter and only one RS450/200 MPPT controller handle the 48kw solar output without clipping and wasting it? If not, how many would I need ?

Should I separate the AC loads from the DC loads on different inverters? Meaning, the higher output appliances (washer machine, refrigerator, freezer, water pump, water heater) put on the main AC inverter. And, the smaller electronic loads (Starlink mini, laptops, smartphones) put on the DC to DC inverters - 2 Victron Orion-Tr Smart 48/12-30A (360W) Isolated DC-DC Converter ORI481238120 (720W in total) in parallel operation and load balancing to distribute devices evenly across both converters to avoid overloading ?

4

Hello!

Many LFP battery manufacturers specify a minimum State of Charge (SoC) of 10%, some even recommend 20%, for a longer battery life.
Your usable range will be ~100 kWh.
100kWh / 5,5kWh/day = ~18 days from battery

5

First, when the batteries get to 30%, the block heater on the diesel generator will turn on to warm it up before it starts to recharge the batteries. The when the batteries drop to 20% the generator turns on to recharge the batteries with auto-start.

1 Like
6

How many fully dark days in the winter you have at your location? 60-70…

7

December has the shortest days in Alaska…

“In key interior locations like Fairbanks, the shortest day of the year features approximately 3 hours and 40 minutes of daylight — with sunrise around 10:50 AM and sunset by 2:41 PM. This makes it one of the darkest periods in the U.S. outside of the Arctic Circle. Even though the sun is above the horizon for only a few hours, civil twilight extends the usable light slightly before sunrise and after sunset, but true daylight remains minimal. For off-grid living, this means direct solar energy collection is only feasible for a narrow window each day, typically between 11:00 AM and 2:00 PM, when the sun is at its highest and most effective angle.”

For example, Fairbanks sees:

  • December average: ~4 hours of daylight

  • January average: ~4–5 hours

  • February average: ~7–8 hours

8

OK, then you reach the 20+.

9

Thank you.

I have some questions about the specific MPPT controllers and battery storage, specifically these two below…

Victron Energy SmartSolar MPPT RS 450V DC 200 amp 48-Volt Tr Solar Charge Controller…

Victron SmartSolar MPPT 250/100-Tr VE.Can

I’m going to have around 48.3kw solar array and 120kwh of battery storage. Is that a mismatch and is the battery storage capacity too small? Does it need to be closer to 200 - 250kwh battery storage to avoid clipping?

Which MPPT controller is best suited for my specific setup?

I asked chatGP and it says that 6 to 8 Victron SmartSolar MPPT 250/100-Tr VE.Can or…

3 Victron Energy SmartSolar MPPT RS 450V DC 200 amp 48-Volt Tr Solar Charge Controller.

I’m very confused.

10

The sum of MPPT max. charge currents must match the battery stack max. charge limits to get all the power from the PV panels and to prevent clipping.

The tech. specs. of the MPPT RS 450V DC 200 says max. DC output power 11520W, so chatgpt’s 3 is to small. You need at least 4x RS450/200.

4x 200A charge current are 800A to the battery stack. On the website of COREMAX is written 400A continous discharge current for a single 200kWh battery module. I cannot find the charge current limits. I take 50%, 200A. You have 6 batt. modules so 1200A charge current is allowed (or more), it the batteries are stackable.
Your battery stack is great enough for the max. power of the PV array. But I did not known if the battery BMS is supported by Victron. You have to check it before.

For a split phase 120/240V you need two MPs. 3000er would be enough for your max. loads, but I would take 5000er, as power reserves or the future. And the 4kW charge power of your ESI Alaska KPG-06 diesel generator.

11

4x RS450/200 is roughly around $7,760 dollars. That’s more than the 60 solar panels. What makes Victron setups so expensive is their requiring a lot of MPPT’s. That’s what really jacks up the price. I hope someday they make inverters that have built-in MPPT’s like the ones below…

I’ve thought about going with either EG4 12000XP Inverter V2 (IV-15000-XP-IN-01) or Sol-Ark 15K-2P-N (Limitless 15K-LV) with their built-in MPPT’s. But, the problem with them is their extremely high low idle draw. Just one of their inverter’s low idle draw has a higher daily kwh than the refrigerator and freezer combined.

Victron really needs to reform their inverter/MPPT offerings and combine them into one unit like the EG4 and Sol-Ark but, with low idle draw. More people would buy Victron if they did that.

12

You don’t need to charge the batteries to their full current…
Although, 50kW will not charge 120kW at their full charging current.
And the day is short.
You need as many MPPTs to cover those 50kW of solar. 4 x 450/200 or 8 x 250/100 in your case.

13

You may also want to look for HV DC inverters… They are more efficient for such high power.
From Victron… you may have to wait for Multi HS19… 1-2-… years.
They’ve assigned the name, product ID (0xA480), but only shown it on fairs for the last 2 years…
Probably the certification and paperwork and …
19 rack mountable 3phase Inverter/Charger with x4 MPPT Solar Charge Controllers 800VDC, 32kWp solar array.

14

Thank you, I’ll look into HV DC inverters. Do you have any recommendations of which brands I should seek out?

That Victron Victron Multi HS19 (0xA480) looks real interesting. I wonder how much it will cost?

15

Im pretty sure you cant avoid that, and to be honest i dont fully understand why you are concerned about it.

Your daily PV energy produced needs to match the daily consumption. Since winter is the time of lowest PV production, you need to setup your system for that. But then its unavoidable that you will have way too much potential PV energy in the summer. But thats not an issue, the MPPTs will simply limit the output power once the batteries are full.

Using the MPPT calculator you can only use six in series on a 450 MPPT, the seventh one would already overshoot on input voltage at low temperatures. Since you bought 60 you would need ten tracker inputs in total.

You should consider hooking up part of the panels to an AC PV like a Fronius.

16

Then 3 x 450/200 is enough, because 450/200 have 4 MPPTs.
So 4 x 3 = 12 trackers, enough for 60 panels.
No need for Fronius.

Am I wrong?

But because 6x800w is 4800W, beyond the W capacity of a tracker, then you can put 5 panels on a tracker and then you’ll have 4000W per tracker (limit) and 4kW x 12 trackers = max 48kW solar.
Well, in fact 34.5kW, because the total power on 4 trackers is 11.5kW…

17

I dont think that you would have to worry about the individual power capacity of the trackers here, i doubt the panels can reach their full power in the winter, and in the summer theres more than enough energy output even when being limited to the tracker power limits

18

If we can try something else for a minute…

Let’s start from scratch. Forget about the 60 panels and 120kwh battery storage. I haven’t bought the 60 panels yet or the battery banks.

What’s the best setup for my specific needs? If you could design my solar system from the ground up what would you do? I’m open to new ideas and all options.

My requirements are for interior Alaska in the winter months to go at least 20+ straight days of autonomy from the battery without the diesel generator turning on to recharge the batteries. Those days include cloudy days and snowy days too. Low idle draw.

19

I have consumption similar with yours. 4.5kW of solar, on 20kW of battery.

Battery:
I discharge to min. 30%, for allowing a small reserve.
In this conditions, on cloudy days, it lasts for about 3 days, without using grid, considering that during day, even cloudy, the panels still produce to supply the normal/average consumption of the house.
So, in your case, for 20+ days, you need at least 150kW of battery, less if you discharge towards 10-20%. But those 30% are conservative.

Panels:
On cloudy days, they are still producing 5-10% of their capacity. Let’s say 5%. 5% of 800 is 40W. 60 x 40w = 2.4kW.
In two hours you should, ideally, recharge what you’ve consumed the whole day.
Adding the house consumption during day, I believe in 4 hours (minimum in December) you’ll be good for the next day, even on cloudy.
Snow is another mater as it blocks totally the sun and you won’t get the same figures.
So, if you get 3 x 450/200 with 5 panels per tracker you consume the whole lot of 60 panels.

Inverter:
If you choose for the inverter the Multi RS 450/100, then you’ll also have there 2 trackers, so another 10 panels, 8kW, total 56kW.
The inverter is high efficiency, low noise, OK for your consumption and peak load.

This is my reasoning. Yours may differ.

LE:
Ups… split phase… 2x120V. Multi RS - no good, only 240V.
You’ll end up with MP2 range, with a little bigger idle draw, because you’ll have 2, less efficient, more noise.
Some will say, handles the power peaks/surges more easily, but it’s not your case.

20

I’m thinking about your Alaska system…

The fundamental question regarding the dimensioning of your ESS is how much additional cost you are willing to invest in order to bridge the PV-weak days with a very large battery and a significantly oversized PV array for a comparatively moderate daily consumption.

If we assume:

And, NO snow at the pv panels!

Why such a huge battery storage system when the PV generates almost the entire daily requirement?

“Saving” the PV energy from autumn into winter using a huge battery costs a lot of money, far more than using a diesel generator for this purpose.