Off grid system for new log home

Hello diemyre and welcome to Solar Panel Talk

The size and type of batteries depends on what type of charge controller you are using along with the amount of estimated daily watt hour usage. The batteries may be FLA type or some type of Lithium chemistry. Although what I have read about the Powersafe is that they are great for telecom or UPS usage and probably do not have a high cycle rate which is not a good place to be for solar.

Thanks for the reply, it's appreciated.

So what could be the best combo inverter/charge controller and batteries?

I need around 20KW inverter and a system capable of running the entire house with heat pump.

A load that size would require a very big battery system which is going to cost you a lot of money. I think you really need to refigure your watt hour load usage before you invest in purchasing any solar equipment.

Hopefully someone that is already off grid can provide you with better data.

What would you be running that would require a 20kw inverter? Seems like a huge inverter to power an off grid log home.
.

What annual kWh load are you designing for ?

What's your location/zip ?

Hi,
it's a 3000 square feet house, I'm not sure about the kWh but we can figure out what a normal 3000 square feet house use usually?

This house will be used in summer mostly, and only on weekend during winter so I'll keep the temperature at a minimum during the week.

It will be location in Quebec, Canada.

I'm aware that I need a large battery bank.

I ordered a diesel 30kW generator to help charging battery mostly during winter.

You need a lot more specific numbers to make that work. Are you
planning to heat the cabin all winter with heat pump(s), or just air
condition it in summer? How much energy will be needed for heat
through winter? Here the amount of propane burned with known
furnace eficiency, revealed how much energy was used. That can
be converted to BTUs or KWhs as needed.

A geo thermal Heat Pump might be most efficient for you, but an
air to air HP is a lot simpler and cheaper. The latest generation are
far more efficient and way QUIETER than earlier equipment. Now
available are HPs that can run DIRECTLY from solar panels, with
AC backup input.

Some numbers at this HP only house, your cabin might be half
depending on size and insulation. The HPs are chosen to cover
the outside temp range, Coefficient Of Performance can multiply
input energy by up to 5, but may drop to 1 on the coldest days.

Energy used in a year is about 29,000 KWh, the majority for winter
heat. Daily use can hit 400 KWh. Annual solar generation is about
30,000 KWh. Since the most solar generation is in summer, a reserve
of about 13,000 KWh is needed to make it to spring. That is done
with a PoCo NET METERING contract, they are to me an infinite
capacity, 100% efficient, zero cost and maintenance, battery. Your
off grid batteries cannot claim any of these attributes.

A battery of anything like 13,000 KWh working capacity is completely
out of practical range for private owners, and probably illegal. Anyway
batteries are not good at holding a charge over several seasons. If
you just want to make it overnight, a couple orders of magnitude size
reduction is still huge. Charging and discharging batteries has losses,
expect 80% or less efficiency. Involving inverters costs some more.
Besides cost, batteries have big safety and environmental issues.

Besides HVAC, electrical needs may be far smaller. RVers have
figured it out, a bunch of small draw lights and appliances can run
on battery, a generator comes on for heavy stuff (deep well, other big
motors) and recharging when required.

These numbers are not your numbers, you need to figure yours out
with a plan, before buying equipment. good luck, Bruce Roe

I'd respectfully suggest you stop buying stuff now.

From what you write and how you write it, and IMO only, that you appear to be in need of a lot of help and/or education.
Get both and you'll probably find that your ideas are going to cost you a lot more than you may think and/or regardless of your budget may be unattainable in any practical sense.
I'm not trying to discourage you, but you don't understand what's required and you don't seem to have an organized plan.
For some examples: You don't have an estimate of what your annual or monthly electrical needs will be, and yet you're buying a generator.
Another point: Where did the 14 kW array size come from ?
What's the estimated long term annual output ?
For off grid, a reasonable estimate of the day/day insolation patterns will be very helpful if not essential for planning purposes. You'll need weather information, including likely insolation patterns to size a battery bank.
Have you ever lived off grid ?

Put the brakes on and get educated or expect to spend lots of time and money learning from your mistakes. I wish you success, but it'll be long(er) to achieve the way you're currently going about it.

Wow that is a big home for Canada. I can tell you that my current home is only 1600 sq ft and I use almost 70kWh a day due to it being in Florida with AC in it and a couple of sheds. So a quick napkin calculation would show a typical off grid solar/battery system to cost about $1500/kWh used and for me that would be about ($1500 x 70 =$105,000) which is a lot with FLA type batteries and probably more with Lithium chemistry batteries.

Thanks you for the replies it's appreciated. I came here on this forum to get help, before buying any solar system. I should've give more informations here before posting it would've easier for you.

I'm well aware it's not a simple 2kw inverter + a couple of batteries this system will be, I know it will be expensive.

So here are some more informations: No electricity compagny is near the house, so on-grid isn't a solution. The house will be our secondary house, mostly used during summer and sometimes during the winter weekends. Spring, summer and fall aren't my concern, I know the solar system will keep up (my parents also have a house next to mine and they have not problem with their solar system). My primary concern is having the house at around 50F during winter, when no one is present so nothing is going to freeze inside (when present, wood fireplaces and furnace can be used). The house will be fully automated so I will know what's going on when I'm not there.

Since Tesla won't sell their solar shingles/panels up here, I got two quote from other solar shingles compagnies. This is where the 14kW comes from.

The second quote proposed:

-Solar shingle installation on south east roof :158 units
-System capacity: 15.8 kW DC
-Estimated about 17000 kWh electricity generation at the 1st year.
-Installation L.F. : 472 linear feet
-Solar shingle roofing area: 1075 SqF

-Inverter: 6 x 120-240V 3500 watts, total: 21kW
-Battery storage: 4 x 9.6kWh, total: 38.40kWh

I know it might be not enough to keep the house from freezing during winter, that's why I ordered a 30kW diesel generator. I know it's more than enough to power all of the house and also to charge the batteries. Tank is 320 gallons.

Like Bruce Coe wrote, I was thinking about getting a geothermal heat pump but when after getting informations about the air to air heat pumps, it seems that air to air are now way better than they used to be.

I have no information about the insulation of the cabin, all I know the logs are 14'' diameter from white pine. This is a new built, so I assume it will be well insulated.

A few comments

Log cabins may be well insulated, but they are infamous for drying out, settling and ending up with high infiltration losses. The testing is usually done when the building is brand new so the infiltration losses are not in place yet. Plan on a very large increase in heating demand as the building ages. The modern polymer chinking systems have improved things but it is still an issue. They company that built the place and sold you on the concept will be long gone before this is issue.

My guess is Quebec province is not a great place for an air to air heat pump for primary heat as the performance drops substantially in cold weather. They are great supplemental heating sources but when it goes below 0 degrees F they are no better than electric baseboard and running resistance heat off batteries is generally not recomended. You possibly may want to get a liquid cooled diesel with heat recovery to use for heating in cold temps. Geothermal heat pumps are far more expensive to install due to low ground water temps but if installed correctly they put out a lot more heat in very cold conditions. They are complex and do need maintenance so if the cabin is in a rural area make sure there are a couple of sources of reliable service. The few installations in my relatively rural area are in high end vacation homes and the service is typically coming from service firms a couple of hours away at $100 an hour travel time.

Roof mounted PV in snow zones is a problem for winter production. When you need it most, its likely that the panels will be locked in with snow. Its one of the rare cases where tracking solar arrays may make sense as they self clear far faster than a fixed roof mount. Note they still will get "frozen" in with snow on occasion. There several near me in Northern NH and with the wrong snow conditions, I have seen them vertical with a layer of snow stuck on them for up to three days after a storm. All Earth Renewables builds them in Vermont and even they tend to underestimate snow piling off the panels, I have seen a few of them where snow built up for a few hours on the array in a heavy snow storm, then the snow slides down and makes a lump of snow that then stops the tracker in its place, usually pointing in less than optimal position. Unless someone has a snowblower and lot of time, getting one going again with snow pack is major effort as the snow is usually layers of hardened crust.

Unless you like being a "guinea pig" stay away from solar shingles, to date no company has come up with a long term reliable system. The companies who tried are either bankrupt, or just closed down the divisions. Tesla is on its third redesign and had been selling them as loss leader for years until they finally started selling them for substantial cost increases. Their current design has a separate water proof membrane under the shingles, all the shingles do is provide UV protection to the membrane. They use and injection molded plastic system for much of the shingle structure S, and plastic in hot environments tends to degrade and get stiff then fracture prone. Stick with galvalume metal roofing with snow brakes where you need them. Strongly consider pole mounts with adjustable angles or consider a wall mount vertical array under an overhang for part of the array. With snow on the ground, the vertical panels if not blocked by snow (meaning mounted well up off the ground) put out over rated capacity in cold temps due to sun reflecting off the snow.

In general, what you are proposing is a complex system that really needs to be designed by a pro, you will not save a lot of money DIY as rework you will inevitably need to do is going cost more than doing it right the first time. Do yourself a favor, build a separate power shack to house the generator and batteries, I have run into several off gird and formerly off grid folks who all start their stories about "after the fire". In most cases they burned there house down, with a separate power shack it can burn to the ground yet the house structure is saved assuming it does not get water damage from burst pipes (various plastic piping systems can reduce this damage but not eliminate it. Install far more fuel storage than you think for the diesel as it may be running for weeks in winter.

I have a 30 x 30 cabin with big porch totally off grid. I have a 14k Kohler backup generator (a 12K would work). This is not a primary residence. I have 1200 watts of solar panels. I'm using 6- 12v/200ah Li batteries in series for a 24 volt system. Also using a Magnum 4000/24v inverter. I use the Gen. for Ac use (a must) and for battery recharge in emergency cases if no sun. Everything is a trick. No absolutes. My system is 10 years old. I replaced my FLB this year with Li batteries. The Li recharge very fast (about 2 hours). So far I like them and recommend. I have 2 /110 window units and the Gen. pulls them with no trouble in the summer. Again, we don't use the cabin as much as we should but it is great for holidays and fishing. Everything is propane based from stove, heat (gas logs) to Gen. I have a 200 gal propane tank which I refill 1 time a year. My water well is 140 deep with a 220v submersible pump. Hope this helps. I recommend thinking of a way to keep your batteries above 40 in the winter. If you can house them in the cabin area would be great. You can use that room heat to protect from freeze. I'm dealing with that now. My battery bank is in another storage building non heated. Good luck!