Off grid island cabin

[Asnarby]

Hi all, I’m a new member of the forum but have been reading and trying to learn for a few years now.

We recently purchased a 2,000 sq ft log cabin cottage on an island in Canada. Currently it’s powered by a 4,800 watt generator and has mainly propane appliances.

-Propane stove/oven
-Propane combi fridge/ freezer
-Propane instant hot water (older unit, not enough output and maybe needs to be serviced)
- individual propane heaters in 3 bedrooms and 2 baths. One 40,000 btu propane fireplace in main room.

There’s a 220V pump with a small pressure tank around 8ft in elevation above the lake where we get our water. The cabin I would estimate is another 20-30ft in elevation from the pump and pressure tank.

I want to install solar with enough batteries to run lights, fridge, freezer and a load through a 120V dishwasher at night time. The majority of use for the cottage is from June to September, with occasional use in November, December, and April. Heating needs can remain propane and wood (if installed).

I’m trying to make a decision if I should go AC appliances, or if I should aim at doing as much DC as I can.

I am thinking a gravity tank for water use so I don’t require a lot of power at night. Maybe go DC for the pump and pump to an elevation of around 50-60ft. The cottage will be winterized when freezing conditions are present.

For hot water, I’d like to keep instant propane, but am considering adding solar thermal heat, or if it’s possible, a DC powered heat pump water heater or mini split that I could use the removed heat from the room to heat the water and get air conditioning in our bedroom.

The main question is, should I spend the extra for the efficiency or DC appliances, or should I keep things simple and run everything AC?

Thanks for any advise!

 

[LywWyr]

If it's me , I go ac devices . I think by the time you add up the additional cost of the dc devices, and the time and materials to run dc circuits to the devices, you could have just bought more solar gear.

 

[chrisski]

Keep things simple and run AC, at least for any requiring serious wattages.

High wattage DC appliances are rare or hard to find. A 1500 watt appliance would probably need to be around 48 volts to keep the amperage down to 35 to 45 amps. If you do find DC appliances, you have to think about maintenance and replacement. If you do run these at a higher DC voltage like 48 VDC, you have trouble finding smaller wattage things at 48 VDC like LEDs and USB chargers. Also, sticking with AC you can maintain the same wiring.

IMO, The amount of energy saved by going to DC is not that significant When compared to all the extra work to install the DC lines. Imagine just simply connecting an all in one with a 3000 watt inverter and hooking the generator into that and being done with that.

I have a RV build with a 3000 watt inverter and looked at replacing some AC appliances with DC and decided against it for reasons like above.

 

[740GLE]

When going with DC appliances one benefit is they are designed for crazy efficiency. Something like 2-3 times the insulation so I still think it’s worth looking at. No one says you can run a DC fridge and inverter for other 120 needs.

Unique and sunstar are great brands that does propane and DC fridges and freezers.

 

[Asnarby]

Thanks a lot for the replies! The place is wired for AC now so hearing that is exactly what I needed. I guess saving the cost for DC appliances and using it towards more panels/batteries is likely the way to go.

The one appliance I wonder if it’s still worth going DC is a heat pump from hotspot energy? https://www.hotspotenergy.com/DC-air-conditioner/

I was thinking having one of those with heat recovery going to a water tank pre instant propane hot water. Or are the losses for just running a normal AC one minimal? I would run it on hot sunny days and maybe a bit at night but for those few days that it’s crazy hot and humid I could just start the generator to top up the batteries.

Thanks again for the help. Any thoughts on a large gravity tank vs a larger pressure tank and have it in the cottage?

All the best!
Andreas

 

[740GLE]

If your going all AC, size a small 120v jet pump and pressure tank, little less hassle than a gravity tank.

If you go for a nice Low Frequency inverter it’ll have no problem driving the jet pump.

 

[Asnarby]

If your going all AC, size a small 120v jet pump and pressure tank, little less hassle than a gravity tank.

If you go for a nice Low Frequency inverter it’ll have no problem driving the jet pump.

Thanks, I was thinking of going an all in one unit like a sol-ark but maybe that’s overkill. It would future proof the place if it became more full time use.

 

[OzSolar]

If it's me , I go ac devices . I think by the time you add up the additional cost of the dc devices, and the time and materials to run dc circuits to the devices, you could have just bought more solar gear.

Totally correct. The poor reliability and lack of convenience of using DC appliances is easily offset by adding a few more solar panels and using all AC appliances.

 

[32 volt boater]

IMO off grid as much DC as possible.

What poor reliability ?

A few wires in a cabin how hard is that ?

AC motors are less efficient than DC motors. In fact, the DC motor is 30% more efficient than AC motors due to the secondary magnetic field being generated from the permanent magnets rather than copper windings.

High quality sine wave inverters are rated at 90-95% efficiency. Lower quality modified sine wave inverters are less efficient - 75-85%

Just internet copy pasted numbers not real world but they say 40%

When going with DC appliances one benefit is they are designed for crazy efficiency. Something like 2-3 times the insulation so I still think it’s worth looking at. No one says you can run a DC fridge and inverter for other 120 needs.

Unique and sunstar are great brands that does propane and DC fridges and freezers.

This forum like Edison and Tesla the current wars, but I agree DC is where its at off grid. AC was good for one thing, long distance transmission.

 

[740GLE]

Cheap inverters and cheap PV panels have people eating the added losses of going AC and skip DC loads, what’s another 3-4 panels to serve standby consumption.

Case in point, I’d much rather buy a higher SEER rated AC mini split than source a DC option with lower SEER rating.

 

[Asnarby]

IMO off grid as much DC as possible.

What poor reliability ?

A few wires in a cabin how hard is that ?

AC motors are less efficient than DC motors. In fact, the DC motor is 30% more efficient than AC motors due to the secondary magnetic field being generated from the permanent magnets rather than copper windings.

High quality sine wave inverters are rated at 90-95% efficiency. Lower quality modified sine wave inverters are less efficient - 75-85%

Just internet copy pasted numbers not real world but they say 40%


This forum like Edison and Tesla the current wars, but I agree DC is where its at off grid. AC was good for one thing, long distance transmission.

Thanks for the reply, The cabin is already wire for AC lights and plugs. I am open to some appliances that the efficiency side might help reduce the size of the battery bank I need. The fridge, pump, and heat pump are the three items I’m considering.

In Canada our battery options are a bit limited. I’m trying to decide if I should piece together a kit or buy an all in one kit that’s expandable.

I’m thinking of starting off with;
-4kW of solar panels
-10-15kW of batteries (48V). SOK 100 amp seem to be one of the best priced I could find in Canada.
- Sol-Ark 12k all in one ( this is overkill but future proofs me. Is it better to do separately though)

I’m looking at a 48V DC powered heat pump. Is there a way to wire that direct to the batteries and let the sol-ark take care of the rest? Or can the Sol-ark have 120V to load and also 48V DC to load at the same time?

Am I on the right track here?

Thanks again for the help!

 

[740GLE]

I believe you’d need to connect all DC load to the same bus of the battery, with its own over current protection.

Calculate the idle usage of that Sol-ark unit, I see 60w. Many “grid tied” units don’t care to much about idle consumption. While your speck of 4kw of PV and 10-15kwhr of storage will work, it can’t hurt to plan to add on to it later on if you find storage lacking.

 

[efficientPV]

I want to complement you on wanting to get your wife a dishwasher. There are those here who think going down to the shore and beating them on a rock or rubbing them with beach sand is what she should do. I told her I thought I had married a dishwasher and informed otherwise. I found it simpler than I had imagined.

I have very little in common with the solar world other than I have PV panels. I not only run almost everything from DC, but run it right from PV panels itself. I have about the same situation off grid. Inverter dedicated for the fridge, another 700W for kitchen appliences like disheasher, and another for the LG clothes washer which has no batteries. All the hot water is from excess PV. I kept a propane HWT for years for emergencies and finally pulled it out after never using it. Still like a gas stove.

 

[Asnarby]

I believe you’d need to connect all DC load to the same bus of the battery, with its own over current protection.

Calculate the idle usage of that Sol-ark unit, I see 60w. Many “grid tied” units don’t care to much about idle consumption. While your speck of 4kw of PV and 10-15kwhr of storage will work, it can’t hurt to plan to add on to it later on if you find storage lacking.

I think I’ll add batteries in the future. There’s just so many options and routes a person can take that it makes it very hard to decide. The way route is just going all AC but it would likely require more battery back up because of efficiency losses. I have lots more reading to do I think.

 

[32 volt boater]

The best thing is to get two dishwashers and put an end to almost all dish handling.

One is for clean dishes and you keep taking them out and using them and putting them in the dirty dishwasher until its full then turn it on now they are all clean so the other one thats almost empty now is where the dirty dishes go until its full.

 

[740GLE]

I think I’ll add batteries in the future. There’s just so many options and routes a person can take that it makes it very hard to decide. The way route is just going all AC but it would likely require more battery back up because of efficiency losses. I have lots more reading to do I think.

With that said, the propane fridges are known to last decades and unless your are sick of hauling around propane (doesn’t sound like it if you still plan on using it for heat) I’d keep it around until you have a decent sized PV system in service for at least a season and can judge it’s output and capabilities. It’d stink to have 7 cloudy days and come back to a rotted fridge/freezer, sounds like trips to the store to restock aren’t that easy

Our 10cuft unique fridge goes almost two full seasons (Memorial Day to Oct) on two 100lb tanks, heating and propane lights use way more than the fridge. It’s very predictable how much the fridge uses for propane, cloudy days on the other hand . . . .

 

[Asnarby]

With that said, the propane fridges are known to last decades and unless your are sick of hauling around propane (doesn’t sound like it if you still plan on using it for heat) I’d keep it around until you have a decent sized PV system in service for at least a season and can judge it’s output and capabilities. It’d stink to have 7 cloudy days and come back to a rotted fridge/freezer, sounds like trips to the store to restock aren’t that easy

Our 10cuft unique fridge goes almost two full seasons (Memorial Day to Oct) on two 100lb tanks, heating and propane lights use way more than the fridge. It’s very predictable how much the fridge uses for propane, cloudy days on the other hand . . . .

That’s a good point, maybe I should try it for a full season. I need to get someone to come service it as it hasn’t been used in about 5 years other than when I used it for 8 days this summer. It worked, but one day I looked and it stopped for some reasons. We have an 8month old crawling around on the floor and the thought of propane building up low is a big concern.

 

[740GLE]

The propane valve in the fridge should be like modern pilot light with a flame detector, kills propane if no pilot light.

I think the only thing needed is to make sure the fridge flue is cleaned. Ours came with big pipe cleaner for such a thing.

A CO detector is a nice thing to have, also if you’re in the great white north, the fridge should be plumped for both fresh air and exhaust, us rednecks in the US haven’t adopted that standard yet (not like anyone needs to inspect my backwoods handy work).

 

[Asnarby]

The propane valve in the fridge should be like modern pilot light with a flame detector, kills propane if no pilot light.

I think the only thing needed is to make sure the fridge flue is cleaned. Ours came with big pipe cleaner for such a thing.

A CO detector is a nice thing to have, also if you’re in the great white north, the fridge should be plumped for both fresh air and exhaust, us rednecks in the US haven’t adopted that standard yet (not like anyone needs to inspect my backwoods handy work).

Haha thanks for the info. There is an intake and exhaust for it. We also have a CO detector but it’s only on when the generator is turned on at the moment (we only used the place for a week).

 

[740GLE]

Our unfinished off grid camp isn’t on an island but is a 4hr drive away, and biggest thing I’ve learned is to plan slow and try and do one major project a year. Live with how it is and think about projects to improve on it.

First year was a propane fridge and outdoor shower, lol

Last year was plumbing and septic which was such a huge improvement over an out house and portable shower, lol.

We also have a little one, currently 10mo old, and the number of weekend we travelled this year vs previous years is counted on one hand. Apparently kids require lots of stuff and time, it makes it harder to work on projects.

This year we’re getting it spray foam insulated, next year I hope to have more electrical wiring completed in hopes of having more than just my 1500w inverter and 50w panels.