refrigeration for off grid homes

[MountainDon]

I've got some serious cabin (building) fever going on here. Weather is great snow is melting, but I can't get to building yet.  :'(

Not all of us are connected to the electrical power grid, and some of us even prefer that.    If you're off grid, or have simply made a conscious effort to minimize the amount of energy that goes into keeping you food and beer cold, what do you use?

Here at home (with grid tie solar) we have a 20.6 cu ft top freezer Kenmore that is rated at about 435 KwHr a year.

I am still considering/exploring my options for the cabin. That ranges from efficient 12/24 VDC (expensive!) to propane thru to something like another 120 VAC (thru a sine wave inverter) Kenmore.

And I'm also tossing about an idea to take an old refeer box, sort of build it into the wall, add several inches of insulation to it and then have my refrigeration able friend hookup a new 120 VAC energy efficient compressor unit that would be mounted remotely. Remotely as in the way commercial (grocery store and the like) refrigeration units are mounted outside, on the roof. Except I'm thinking of maybe doing something to allow the heat from the condenser coils to be vented outside when I want the interior cool, or keep the heat inside when I could use the heat, as in winter.

Anyhow, I'm interested in what choices others have made. Thanks.

[glenn-k]

We have one RV propane refrigerator - and a 1934 GE Monitor top refrigerator - much more efficient than anything on the market today - a bit small but cool.  about 200 -230 watts running - runs 2 minutes every 15 appx.  Didn't check it with the meter.  Uses sulfur dioxide refrigerant.  Has been running over 70 years and is original.

We have about an 8 cu ft Conserv (Denmark) chest type freezer - uses about the same as the GE.  Seems they have changed the name to Vestfrost now and I can't find the freezer.  We run the freezer and GE fridge 24/7 all year.

[MountainDon]

I should have stated that my first fridge in the cabin is going to be the fridge out of my tired old RV, boxed into a space that could take something like a modern day Kenmore or whatever. In the meantime I've designed a vented space for the old RV (7.5 cu ft total) fridge. I'm actually quite happy with it but DW has stated she'd like wants more space. I said , okay Someday.  

[MountainDon]

One of those with the coils on top!!! Super cool!

[glenn-k]

Yes - the entire works is on top.  In all honesty I did have to work on it - put a new cord and foam seals on it.

[MountainDon]

- put a new cord....

Woven cloth cord with a bakelite plug ?

[glenn-k]

May have been originally but it had a rotted rubber one with the wires touching when I got it.  Previous owner said that was all that was wrong - he was honest.  

This looks cool.

http://www.partsonsale.com/sundanzer.html

Chest is much more efficient if you can deal with it.

[glenn-k]

Good Google link popped up above -- I have read this guys stuff in other places - I think the archive I posted a week or so ago.

http://www.knowledgepublications.com/sunshine_to_dollars_google_adwords2.htm?gclid=CPfmg5jX-IoCFSOyYAod7ATslQ

[glenn-k]

from the archive...

Of all the refrigerators I own, my old 1928 GE MonitorTop is my favorite.
It weighs about 300 lbs and uses a very quiet low speed hermetic compressor
on top.  It's watts/cu ft is lower than any of my modern refrigerators.
Oh, and it uses sulfur dioxide as the refrigerant.  Never seems to need
charging.


John

--
John De Armond, WD4OQC               |    
Performance Engineering Magazine(TM) |  
Marietta, Ga                         |
jgd@dixie.com                        |

[glenn-k]

Don't forget this freezer.

http://www.homepower.com/files/solarice.pdf

[MountainDon]

And there's always the Icyball.  
http://en.wikipedia.org/wiki/Icyball
http://www.ggw.org/~cac/IcyBall/crosley_icyball.html

I've seen the Sundanzer. It works well, but I don't think I could get used to using what appears to be a giant camp ice chest. I'd have to make a large mental adjustment. I don't even like the chest type freezer we have when it comes for diving for my dinner.

Thanks for the knowledge publications url

[desdawg]

I have a propane refrigerator. It takes a day to cool down when first lit. I would prefer something electric after having this one. Maybe I just got a bad one. I don't leave it lit when I am not there.  So I am still using a lot of ice. A full time electric refrigerator would require more solar panels and batteries I suspect. Anyway it wasn't the answer I had hoped it would be.

[MountainDon]

...takes a day to cool down when first lit...

Thanks Desdawg. Same thing with my propane RV refrigerator. If you're using one in a remote cabin and go there for only a few days at a time you still need ice to carry you thru the cool down period.

That's why I'm leaning towards an electric of some kind and building what would otherwise be an over-sized solar system (panels plus batteries).

What do you use for your propane tanks? Does your location allow you to use a large tank and a propane delivery service?

[desdawg]

I am back in there a ways so I use 2 100# cylinders with an automatic changeover regulator made by Sherwood. I actually have four cylinders so I can keep a couple of spares. I just haul them to town and get them filled.
I recently inherited a 120 gallon tank and a Generac that runs on propane.  I don't have it installed yet. I don't know how I will get that tank filled. I may get a transfer hose made up and wind up dumping 100# cylinders into it. So many projects, so little time.

[MountainDon]

I'm planning on using the portable tanks as well as the propane truck won't come up my road. I have 3 - 40# from other uses and will likely get a 100# or two after I see how fast we use the propane up. Those auto changeover valves are great.

[littlegirlgo]

I had a serval propane fridge for several years at my last off grid place. It was a good size for us about 10 cubic ft. Now being in an apartment ( just till July - yeah!) my refridgerator seems ginormous and very inefficient. I plan on going with the Sundanzer. I want to get away from fossil fuels where I can and it can run off a 100 wt panel which makes it cheaper to install. I figure I need all the bending at the waist I can get! I looked at the Sun Frosts but they are out of my price range. I have friends that have one and love it.

[JamesTheLess]

I am not advocating the Sundanzers because I haven't really looked at all the issues and options,
but the charts they provide and the following costs might form a bench mark for off-grid planning.

My guess is that the smaller size and relatively higher cost for size of these units is justified in off-grid applications where energy costs might be $0.50/kw-hr, but I haven't really looked at propane options.

http://www.earthsolar.com/pdf/sundanzer.pdf

Daily Energy Use with typical opening and content turnover.
165 Litre Fridge = ~ 0.14 Kw-hr/day @ ~38F inside and ~78F room
225 Litre Fridge = ~ 0.18 Kw-hr/day @ ~38F inside and ~78F room
165 Litre Freezer =~0.42 Kw-hr/day @ ~10F inside and ~ 70F room
225 Litre Freezer = ~0.54 Kw-hr/day @ ~10F inside and ~ 70F room

Note that frozen food lasts longer at 0F than 10F but efficiency drops significantly.
Keeping the freezer in a colder room helps keep effiency up and energy loss down.
Above units are top loading, which might seem awkward for fridge but saves energy.
Typical opening etc seems to add about 50% to energy cost of freezers and 100% to fridges.

Assuming $0.50 per Kw-hr in off-grid situation, cost of above units simply stretched over 10 years.
165 Litre Fridge = $838 + $0.07/day = $0.30/day = $110/year
225 Litre Fridge = $927 + $0.09/day = $0.34/day = $126/year
165 Litre Freezer = $838 + $0.21/day = $0.46/day = $160/year
225 Litre Freezer = $927 + $0.27/day = $0.52/day = $192/year

I think I would go for the larger size and then maybe add extra insulation on the inside if I didn't need the space. I think putting blocks of ice on the bottom on top of some slabs of foam might be a good way to fill up some space so you don't have to dig around or let as much cold air out and warm air in. The ice might also help maintain a constant temperature if you had it on a timer or something for load management purposes. Anyhow, for generally planning purposes I think you can consider something like as little as 0.60 kw-hr/day in winter and perhaps 0.80 kw-hr/day in summer. You should have more energy in summer if your solar. If you are on wind power you might consider shutting down the freezer in the summer, or relocating it to a cold room.

My overall goal if off-grid would be to keep my average energy use down to 6 kwh/day, which even at $0.50/kwh would still be only about $100/month, not counting appliance costs. So if I could get by with these somewhat small top loaders the fridge and freezer might represent about 10% of my energy use.

By comparison, for drying clothes I would like to think I could get by with something like the Thor:
http://www.thorappliances.com/comparison/index.php

It uses only 1.4 kw-hr for a wash/dry, using 115v. I think if I kept the use down to 1-2 loads per day and used the clothes line for the sheets and towels then laundry might be kept down to 30% of my energy use, perhaps 50% if it runs off an inverter. The neat thing about a combination washer/dryer is you could do a load on a timer while you are out so it could either be set to run off the inverter during peak sun to reduce charging and discharging losses, or perhaps time it to run when the generator is charging the batteries if that could be put on a timer also.

Lighting use is higher in winter, which is not so bad with wind power but compounds the problem of using solar modules in the North. This problem can be mitigated considerably with hybrid LED flourescent lighting and using candles and oil lamps if you stay up late on winter nights. In December we have about 8 hours of daylight, so I think we could get by on 10 hours of lighting averaging 50w, which is plenty but still only 500 kw-hr/day even in December. When things like laptops and televisions are on lighting can be reduced, but I think the combination of lighting, laptops, television could be kept under 300 kw-hr/day year round on average, and 600 kw-hr/day in December, or 10%.

I am not sure about the other 40%. 40% of 6 kw-hr is about 2400 watt-hours, but that would get used up pretty fast if you wanted to cook a roast or heat any hot water. 2400 watt-hours is about 8000 BTU, which would be only 10 gallons of hot water. So I think I would have to go wood/solar for my hot water, but I might be able to run a microwave oven or a stove burner or a toaster or toaster oven now and then, one at a time while nothing else is going on. Its more an issue of the peak power and the impact on inverter capacity and battery discharge efficiency. If I limited such appliances to 1200 watts and 1 hour in total per day that 2.4 kw-hr would be 20% of my 6 kw-hr/day.

As far as water pumps and stuff like that, depends on location but I would like to use a combination of well water and rain water and use the rain water for hot water at 60 gallons/day with not too much pumping with an atmospheric system. The cold water might be an issue depending on the depth of the well, and if it was deep it might get more interesting, but for rough planning if I consider 250 gallons x 100 feet head for all my water management needs that would be 200,000 ft-lb = ~ 75 watt-hr/day or 1.25%. Again it is more an issue of dealing with the issue of peak power.

Overall I thing my 6 kw-hr/day budget would be something like:
35% Washer/Dryer (Condensing Combi 115v)
20% 1 hour per day of 1200w 115v appliances
20% battery losses
15% Fridge/Freezer (Top Loading 12v type)
10% Lighting/Laptops/Television

[desdawg]

One of the problems with a propane refrigerator is the recovery time. When you open the front door the cold air "drops out" and the refrigerator has to recover from that. Mine looks like a standard refrigerator with the upper and lower door like a freezer door but does not have a freezer compartment. Beverages etc. can be kept in the upper compartment so you have smaller higher door to open when you want a cold drink. Of course when you are preparing a meal the main door is opened. This is an alternative to the chest type refrigerator. But I am still not all that pleased with this refrigerator.

[glenn-k]

Nice posting, JamesTheLess.  Welcome to the forum.

We probably use around 12 to 15 kwh per day leading a rather unthrifty solar life.  We try to conserve fairly well but still lead rather normal lives as if we were on grid.  We pump around 500 gallons or so of water per day  with average 300 + feet of head for the garden.

[MountainDon]

We probably use around 12 to 15 kwh per day leading a rather unthrifty solar life.  We try to conserve fairly well but still lead rather normal lives as if we were on grid.

Glenn, you're living breathing proof that to be energy (electric) independent doesn't mean to have to live in a dark cave.   :-?  Oh. You do...     You know what I mean; you don't have to do crazy things to be off grid. .... Ah! You do that too.

Anyhow 12 - 15 KwH a day is not bad, considering all the water pumping and everything as normal situation. Here in town we average 16 KwH lowest month up to 30 KwH during the hottest month of the year (A/C load). We sell about 6 or 7 KwH a day to the utility company; so the metered result has us paying for about 9 KwH low to about 23 KwH high use monthly.

The grid tie doesn't really pay for itself in a cost effective way; but I do have the comfort and luxury of having power when the rest of my street does not. It's also my feel good energy thing.

I'm still puzzling over my cabin regrigerator choices tho'  

[glenn-k]

I guess I haven't paid close enough attention - I didn't realize you were set up with solar at your main residence.  That is great.

If the county lady hadn't told me it was mandatory to hook up if it was available, I could be grid tied too. :-/

[MountainDon]

We had a totally unexpected windfall a few years back and decided to put in some solar electric. We've had solar water preheater system and a solar hotair system since '85 (last year of the old tax credits). Due to the power company regs at the time it could not be installed with batteries to cover you in an outage.   What kind of baloney was that! That was one of my reasons to go into it, as we suffered through many outages. Today the power co. reliability is much better, tho we had 2 weather related outages last year plus one contractor caused outage.

We got around the backup power thing by installing a simple grid-tie only, having it approved and then making changes. We were fortunate to have the co-operation of the equipment supplier. Now, after a lot of re-wiring work I did, we have an automatic transfer switch for when the grid fails. When the grid fails backup power is automatically switched to a power panel that supplies a few select circuits; furnace (high efficiency DC fan), the refrigerator and the freezer, the microwave, at least one light in each room and garage, the TV and stereo and a couple other outlets and my front yard light (just to make sure the neighbors realize I have power.  

I've only got 4 - 6 volt AGM batteries (220 amp/hr at 24 VDC) but it's enough for most emergencies. If we'd need more juice because of a long outage I can always fire up the Yamaha 2800i which is relatively quiet; not as silent as the newer inverter gensets, but much much quieter than the typical construction grade genset.

It is enjoyable, like on a day like today; bright sunny skies, no need for heat or A/C. The meter's running backwards   as the only loads are those pesky phantom loads; TV waiting for the remote to say "on", microwave clock, illuminated doorbell button and so on.

[glenn-k]

Yard light (just to make sure the neighbors realize I have power.  

You think like me.

Sounds like a great system.

I try to keep my phantom loads mostly going too - microwave clock - cell phone chargers left in - 4 million power supply transformers for phones - phone battery chargers - computers - printers - print server (pulls 60 watts) - wireless router for wireless DSL - lighted analog meters on the wind generator - little neon lights in several extension cords.

Just like a normal wasteful American energy junkie.

[MountainDon]

2 office computers each have their own 15 minute UPS with the ability to switch to the off grid power if that need should arise. (Change wall socket plugs)  

You said a million phantoms... more like a bazillion!   they're everywhere

One nice thing is I don't really have to worry about what might be melting or otherwise misbehaving if we're away for a few days.

[glenn-k]

We also have never lost anything in the freezer or fridge due to outages and usually if there is any kind of outage it is artificially induced by me such as trying start a loaded 7 horsepower motor off of our 220V inverters - overcharging on equalization or in general screwing around experimenting with my electricity.  :-?

We keep our freezer at -10F for safety downtime and extra long storage time.