Off - Grid refridgerators - How do you do it?

If you have any elegant solutions I'd like to hear about it.
I'm sure others would too.
My take is that I will just need to have enough PV panels and Battery bank and an Inverter to run a Fridge and Freezer.
Thanks...

Nicholas
Thanks - I saw your thread now...
https://permies.com/permaculture-forums/2124_0/alternative-energy/keeping-your-stuff-cold

i have been looking into this my self this is a neat idea of how to turn a chest type freezer into a frig that uses about a 10th of what a stand up frig will use thats good for me be cause i can have less solar panels  http://www.solviva.com/wastewater.htm im looking to build a house after i get back and for it to be all off gride also making it easyer for me to retire and wtih little to no bills and have a good life and retire young mid to late 30s im hoping and this off grid house will make it posable

thecheapguy

I appreciate your goals, Cheapguy.

My thoughts:
an old non-working chest freezer, can probably be had for free.

a working small (1.4 cu. ft.) dorm style refrig, preferably with grills on the back.  $20 to $40 on Craigslist.

2- 4x8 sheets of 2" foam board insulation $25 - 40

Cut a 6" round hole in the top left side of the freezer side (centered front to  back)
and
in the lower right side of the refrig.

Caulk around the hole and screw the frig to the freezer meeting up the holes.  Cold air from the EFFICIENT refrig will fall into the freezer.  don't use the frig itself accept to clear ice.

Insulate the outsideS with the insulation board.  Cover insulation with something to protect.
Worth a try.

http://crosleyautoclub.com/IcyBall/HomeBuilt/HallPlans/IB_Directions.html

Backwoods Solar sells chest refrigerators. Look for DC Sundanzer chest refrigerator.
http://backwoodssolar.com/

Another thing we have discovered in our off grid refrigeration adventure is that in our climate we don't need a refrigerator half the year.  It's cold out- at least at night.  When it's cold enough to make ice, we harvest the ice for our cooler we store in the cold storage pantry.  When it gets down to 40 F or so at night, we bring the full cooler outside and leave it exposed to the night sky- with a screen over it to protect from animals.  Then back in the pantry during the day.  This has worked great for us.

The key is not to expect to have a refrigerator filled with things you rarely use.  This way takes more attention, like a lot of things do when you live off the grid.  But it reduces the need for high tech refrigeration to only some months of the year.  Luckily, these months also provide many of hours of sun a day to provide solar power for a dc refrigerator. 

          that is a nice idea Erikgreen have you made any progress yet?

In my mind, converting light to electricity and then converting that electricity to refrigeration is inefficient, although it is a method that many would choose to use.  I like looking to the examples of the past, when many of our technilogical marvels didn't exist, and see how problems were solved then, hence the posting of the 'Icy Ball' link that I posted above.  Long before freon and other ozone-damaging gasses were discovered, our ancestors came up with the idea of the ammonia absorbtion refrigerator, a far cry from the 'ice box' (which used chunks of ice for cooling). 

For those of you fortunate enough to own an old Servel refrigerator, you have just such an ammonia absorbtion cycle unit.  The first units used a kerosene stove to heat and evaporate the ammonia, later units use electricity to do the same thing.  My idea is to use the sun as a heat source, concentrating light (heat) onto the evaporating portion of the unit.  This light is not used at night, which is when the cycle reverses, as the ice in the freezer unit melts, starting the cycle over again.

Alternatively, a heatsource such as a rocket stove/RMH could provide the heat source to make the unit work.

A number of commercial ice-production plants use the ammonia absorbtion/evaporation cycle to produce their product, so it is a viable technology.  It just has to be handled carefully, and hopefully by qualified people, in the setup phase.

Erikgreen wrote:
a working small (1.4 cu. ft.) dorm style refrig, preferably with grills on the back.  $20 to $40 on Craigslist.

I wonder about this. All of the low cost dorm sized refrigerators (under 2 cu ft) I've seen don't even have a Energy Star label. The few that I've seen that are Energy Star labeled are 3 cu ft to 4 cu ft and not cheap. I'm simply wondering about the claim of this being efficient.

In my experience, they are not at all efficient. Couple years ago I was looking into getting an extra fridge to store seeds in and looked at them. An ordinary full-size refrigerator used hardly any more electric than those did.

The "energy star" label in todays world

is nothing more than the "Sears Best" of yesteryear.  Or, remember, in the 60s and 70s when movie stars like Debbie Reynolds, Jane Wyman, and the like, would pose and make claims to the wholesomeness and technological advantages of their new Avacodo washer and dryer.

You ever notice how the "energy star" models are the most expensive models?  ah heh. 

Gee, I wonder if some UNspecial interests were working behind the scenes in Washington for that. 
hmm.  Corruption in our government?  Nahhh. 


The best way to check for real efficiency is to get a Watt meter, plug your appliances in and monitor. 

Cheap guy,
Well, its been a bit more than 24 hours, but I have been thinking how to perfect this. 

As a matter of fact, I do happen to have a small 1.4 cu. ft. dorm frig that I'm not using.  See it on the floor in the pic under the two frigs I use, each close to 4 cu. ft. each.

I don't have a chest freezer, but I know someone who sells appliances and has all the used ones sitting behind their store. 

I've been thinking, do I want to do this.  How will it fit into my Tiny house?  I will have room for my two frigs, and compact 3.5 cu. ft. freezer, but would a frig chest be a good idea? 

Thoughts:
Why I think my idea would work.  When you open the chest, you don't lose any cold air, so a chest frig doesn't need as big a compressor as a vertical frig.  And with the extra insulation added...

another thought:
instead of using a standard, freon based, dorm frig,
use a thermoelectric frig.  Again they are cheap, even new.
This can be converted to run on 12 volt thereby by-passing the need for an inverter when connected to solar.
Also, it would be easy to vent outside using 2" pvc with a flow through design against an outside wall.  The inlet, say at floor level, and the outlet at ceiling level.

I haven't taken apart a thermoelectric frig yet, however, if the electroplates can be removed and reinstalled on the freezer, you can eliminate the box. 
If not simply removed, take a jig saw with metal blade and cut out the back of the frig, cut the same size hole in the back of the freezer and install.

Also, I think a chest Frig would be better made from an old vertical frig because they aren't as deep.  An old frig, laid on its back and elevated off floor to countertop height would be easier to reach in and retrieve items.  They are more prevalent than old freezers and newer ones, better insulated.  Also a two door frig would give you a way to separate things.  Maybe the small door could be used for beverages, easier to get.

and the frig pic.

Erik, I appreciate the doubt expressed regarding label claims. I own two Kill-A-Watt meters. They are very good. I love numbers and data.  I also agree with the thought that a chest unit costs less to run than an upright. I for one do not like the idea of a chest refrigerator though. They are not as convenient; so yes they do have a place, but not at my place.

My own experience with the Kill-A-Watt meters and the appliances I own has been interesting. (Everything measured for a 30 day period. Room temperatures slightly less than the US average.)

My new refrigerator (2009 Energy Star labeled) used about 2% more than what the Energy Star website database indicated. I think that is pretty impressive. It used almost 22% less than the older equal sized refrigerator it placed.

The freezer (2010) can in under the Energy Star rating by 8% and beat the crap out of the older freezer.

The dishwasher (2010) came in at just about equal to the Energy Star claims. I can't compare to the old one as it died. The new one also uses a heck of a lot less water.



The upright on it's back would might require some spring or gas cylinder assists to make it easy to lift the door that is now a lid. 



By thermoelectric are you referring to the finned, solid state Peltier effect modules as used by Koolatron and other cooler manufacturers?

PaulB.

The icey ball sounds neat.  Its just, I'm always a bit hesitant about something that has a tendency to

EXPLODE !

me, I'm sure its just me,  I don't know if I could live with the trauma of my refrigerator exploding.  or just the threat of it. 
The stove, my car, the major abandoned mall near by...
I could live with that, but not my frig. 

Maybe the ball could be double hulled, then I would be willing to try it.

Hi Don,

I thought about the doors needing assists but I know that assists can be had as a standard hardware item.
Or if one wants something simple, a hook on a cord to hold the door up once open. 
Thats a minor concern, but  a valid one, for sure. 

The Thermo electric dorm refrigs that can be had for about $69 new at common retailers.  They look like a standard small dorm frig, but when you look inside there is no ice box and the back has grills.  Also, the sides have holes for venting heat. 

As for the stickers.  They don't even rates small appliances.  For example these small dorm frigs or small point of use type water heaters like 6 gallon vs.40 gallon, for example. 
I think they want people to think that those items aren't in the running.  I recently picked up a tank type water heater brochure.  Anything under 20 gallon wasn't rated. 
Why not? 
because if you see how much more efficient they are, people would consider them.   
We have to remember that the oil and energy companies have been doing what ever they can to corrupt. 

Here is an idea i seen awhile back of using a chest freezer with thermostat to regulate temp that is about the easiest ive seen http://mtbest.net/chest_fridge.html
they have directions and such there also

I guess this is more of an ice-chest design than a fridge, but we have an old well-water milk cooler that was used to cool large milk cans before the days of refrigeration. It's still here, and I'll try to take some photos. It's a large concrete basin, about 4' deep and sunk half into the ground. The top is a thick wood, insulated and hinged affair, and the milk cans were lowered into the cool well water. There's a water line that runs into the cooler, straight from the well.

I don't know how cold the water is, but it makes for a chilly shower! It's in a different direction than the earlier posts, but a pretty cool pre-electric solution all the same!

We are not off grid, but would love to be.  We do however have to pay an electric bill every month which is a big incentive to save electricity.

I also read about converting chest freezers into fridges, but read on a post here that it will shorten the life expectancy of the unit.  So we are going to try a different tactic.

Today we bought a 5 cubic foot chest freezer, tomorrow the fridge gets unplugged.  We will keep our cold stuff in a cooler of ice.  We will make the ice with our freezer.  Hopefully in a month our efforts will have saved us some serious cash.

I think that with careful menu planning we will be able to utilize both our cooler space and food inventory a lot more efficiently.  (Hey there is no room in the cooler, guess we better eat those leftovers for lunch today)

PaulB

Here is a similar design.

http://www.solarhaven.org/AmmoniaAbsorptionIcemaker.pdf

Thanks, Shawn, I printed out that pdf a couple of years ago, I have it in mind when I build my house.

Cyric30 wrote:
Here is an idea i seen awhile back of using a chest freezer with thermostat to regulate temp that is about the easiest ive seen http://mtbest.net/chest_fridge.html
they have directions and such there also

I'm kinda bugged by the author's attitude of, "why don't people recognize what a great idea I had!"  The problem is that this system won't fit into the kitchen of a tiny house, or even in the kitchens of most standard houses.  It means removing somewhere between 4 and 5 feet (1.2 to 1.5 meters) of counter space, unless you put it on some fancy roller system that lets you store it under the counter.  (which means you've given up an equal amount of cubic storage space.)

Yes, it's wonderfully efficient in terms of power usage, but if you have to keep the fridge in the basement and tromp up and down the stairs when you're trying to make Sunday breakfast, the glamor of low energy usage can wear pretty thin.

PaulB wrote:


For those of you fortunate enough to own an old Servel refrigerator, you have just such an ammonia absorbtion cycle unit.  The first units used a kerosene stove to heat and evaporate the ammonia, later units use electricity to do the same thing. 

A seller on Ebay has 5 of these for sale http://cgi.ebay.com/antique-servel-gas-refrigerator-NEVER-USED-very-rare-/17062791002

Here's the description: "This is an old gas refrigerator i found in a house i bought that has a large area full of antiques. im pretty sure it used to be a general store at some point. there are 5 of these total all in their respective shipping crates never been used ever! they have all the original parts, packaging, ice trays, shelves, everything that comes with it is all brand new and very rare."

He set the starting bid at $900.

EDIT 4/14/2011.  This link may work better?  http://cgi.ebay.com/antique-servel-gas-refrigerator-NEVER-USED-very-rare-/170627910026?pt=LH_DefaultDomain_0&hash=item27ba37498a

Most freezers seems to have really thick insulation...I've looked on google and there are some pretty efficient refrigerators out there. Look for the "energy star" rated ones...if you stay with a reasonable size they will work well in a off grid solar set up...as far as I'm concerned.

For a solar system I think that the following recipe ought to be cost optimal:

Decide how much fridge volume you need.

Then buy an ordinary chest freezer of at least twice that size.

Fill the bottom and line the sides with lots of cans of beer to provide thermal mass. Tape them into place until at least half of the volume of the freezer is taken up. Line the remaining space with card board so you now have a usable cold food storage space of the desired volume. The sides of the freezer might well go below freezing, but because it takes so much energy to freeze beer the zone in the middle where you store food will never get to freezing temperature. This will work as long as you don’t provide enough energy for the refrigeration mechanism of the freezer to run 24 hours per day. And this is the trick - scale the solar panels to provide current to power the system only when the sun is shining. During the day the beers will get really cold and at night they will slowly take up heat from the food storage compartment.

You might be able to simply get an inverter matched to the max power of the freezer and directly connect the solar panels to the inverter, without using a charge controller or a battery.

Unfortunately it is probably not quite that simple - there is one more trick. Ordinary electric motors require a much bigger starting current that what they need when they are running normally. You probably will have to add a battery to the system to provide this brief power kick. This won’t cost anything because the power spurt is quite brief and an old car battery that is too feeble to start a car and too old to store much energy will still be quite sufficient for this application for many years after it has been retired. But then you need to make sure that when the solar panel is not providing enough power that you don’t drain the battery. A simple solution would be to add a relay so that when the voltage on the DC system get to below about 14 volts then the AC circuit gets shut off. An electrician/engineer ought to be able to put this together for a few pennies.

I haven’t done this yet, but I intend to do so someday.

There are custom chest freezer controllers for converting for keg beer usage, check the top homebrewing sites, and Brew mag.

Peltier electric conversion panels are some of the least efficient systems out there, and generate a LOT of heat. Vents and fans are required. Great for small spaces, and areas that need to be kept dry tho.

You cant lay a standard fridge down on it's back, without moving the coils, and the diptube? around to the back. there is a vertical evap pipe in the back of those fridges. That is why you have to let them set for 24-48 hours after you move them. Also, heating from below, not the most efficient design.

Most freon systems, including vehicle systems, can have the coolant replaced with propane, and still operate at peak performance. There is lots of discussion/argument about this, and in vehicles, where there are more explosive risks, there is only one, possibly, event that may have been caused by this replacement. It also may have been a hit. Propane systems don't have to be pumped down to vacuum when adding or replacing coolant. There is not one, single , HVAC service person that recommends this.

Jack Shawburn wrote:If you have any elegant solutions I'd like to hear about it.
I'm sure others would too.
My take is that I will just need to have enough PV panels and Battery bank and an Inverter to run a Fridge and Freezer.
Thanks...

1. Use only a fairly large chest freezer. Do not purchase a separate refrigerator unit.
2. Load the freezer with bottles of salt water. The salt will lower the freezing point. Of course, leave some space for your frozen foods.
3. Use ice bottles to cool a small super insulated container to serve as your refrigerator. I suppose you could get fancy and connect the insulated space to the freezer with ducting (preferably right next to the freezer).

The main benefit here is in using a thermal mass which will lessen the discharge on the battery system and help protect your batteries. Note that a large freezer is a lot more efficient than a small freezer due to the lower surface area/volume ratio, so a large freezer provides more cooling capacity for each unit of electricity consumed (checking the specs on freezers shows this clearly). Also, it's easy to super insulate a small container far greater than most small refrigerators available on the market today. Therefore, this configuration allows for providing a large thermal mass without suffering additional electricity consumption, and without suffering a lower food storage capacity. NOTE: When it comes to off grid power generation, the batteries are the heart of the system... all else equal, the configuration that best protects the battery system should be favored.

You could use bottles of salt water for thermal mass but from a Thermodynamic point of view beer will work just as well. And beer comes conveniently packaged and can be useful to have on hand in case of unexpected emergencies like a sudden barbecue.

Why not just keep the fridge inside the freezer? Just be careful that you don’t overpower the system and nothing ought to freeze.

Refrigeration is the exception where batteries need not be the heart of a solar system. Instead of storing energy chemically in batteries you can use thermal mass to store cooling potential. Minimal battery power might be needed to provide compressor motor startup current and the batteries can be protected with a simple electronic relay system.

Robert Isted wrote:You could use bottles of salt water for thermal mass but from a Thermodynamic point of view beer will work just as well. And beer comes conveniently packaged and can be useful to have on hand in case of unexpected emergencies like a sudden barbecue.

I suppose I should have clarified the purpose of the salt water. Most freezers operate at about 0F. The freezing point of salt water can get as low as -6F by adjusting the salt concentration. BTW, my limited research suggests that a freezer can operate safely between 10-15F. As far as the beer goes... well, yes, that's a tragic loss. .

Robert Isted wrote:Why not just keep the fridge inside the freezer? Just be careful that you don’t overpower the system and nothing ought to freeze.

I suppose so, but then you'd have to open the freezer every time you get a beer!

Robert Isted wrote:Refrigeration is the exception where batteries need not be the heart of a solar system. Instead of storing energy chemically in batteries you can use thermal mass to store cooling potential. Minimal battery power might be needed to provide compressor motor startup current and the batteries can be protected with a simple electronic relay system.

This is a matter of perspective. I see the battery as the heart of the system, and a thermal mass refrigeration system as a means to reduce stress on the heart. The goal is to help the patient (err, system) live longer. If properly designed (for example, by setting the proper mass, heat flux, and freezing point of the thermal mass), then the compressor should cycle only once during most days.

Yes I agree.

Ideally, to fully exploit the latent energy of the phase change, you would have to tune the freezing point of each bottle of the thermal mass fluid to be the average temperature of that bottle. You could do this by adjusting the amount of salt in each bottle of water. Or you could forgo the optimal solution and simply have a few more cold beers on hand and slightly less space in the fridge.

I read an article on here a ways back that linked to mt best where I found out about the chest fridge idea: http://mtbest.net/chest_fridge.html

Basically it's a chest freezer with a fridge thermostat hooked up to a dedicated fridge inverter that is powered by a dedicated solar panel.

It doesn't have a freezer but it runs on its own solar power, you could get a mini freezer and use the same concept

The chest design is best for a refrigerator because when you open the door you don't let out any of the cold air [Because cold air falls]
Set the thermostat to 32-33*f and hook up your inverter.

Your battery bank needs to be able to handle 100watt hours per day that the fridge uses on average, so pretty much any battery will do, You MIGHT be able to get away with using a car battery, but I wouldn't recommend it.

100 watt hours isn't a lot of energy by today's measures, You could get away with a single 60w 18v panel as long as you get more than three hours of sun per day. If you were to buy your panel it might cost $200, but you can build one for significantly less if you buy in bulk.

I got the cells for around $20 brand new, got a battery for $40 off craigslist and I had an inverter [if you don't have an inverter you can get one for ~$50 and the chest freezer came in at $200 from home depot. Total cost for the project was $320 for an off grid refrigerator...not bad!]

I used to own an old propane refrigerator that was amazing . It ran off a pilot light sized flame. Flame made contact with a diaphram that expanded with the heat. This was enough to provide pressure to the ammonia gas in line which then cooled. I wonder if anyone is still making those. Mine was Swiss made. Wish I still had it.

Here's an idea that I haven't figured out yet.


Radiational cooling occurs when infrared radiation is emitted from an object's surface, causing its temperature to decrease. On a clear night, infrared rays are emitted from the ground into the atmosphere, cooling the air down. This is why the night is extremely cold in the desert. Most people have experienced water's natural convection currents when warm water rises while cold water sinks and pools at the lowest level.

The cooling unit of the refrigerator (capacity 200 litres) is made of metal that has high thermal conductivity. A large volume of water (about 250 litres) is stored around this unit as a coolant. Radiator panels are placed on top so that the inner surface of the panel touches the coolant water. The heat of things stored in the cooling unit is conveyed to the surrounding water by the metal, and the heat goes up by natural convection. Thus it is conveyed to the radiator panel, and emitted through radiational cooling.

The system is most efficient on a clear night when there is less water vapor in the air. One clear night (and sometimes even one cloudy night) every three days can keep the temperature inside the refrigerator at around 7 to 8 degrees Celsius even on a mid-summer day. This innovative refrigerator belies our present-day common sense assumption that things cannot be refrigerated without electricity.
by Yasyuki Fujimura of Non-Electric Atelier

What are the radiator panels made of?
I look forward to other people's thoughts on this one

Yesterday on the Survival Podcast with Jack Spirko he had Steven Harris who is an alternate energy guy and he talked about refrigeration. He said those dorm coolers use as much electricity as regular fridges because they use the same size compressor and because they have less insulation they run more often. He recommended using an ice maker as an efficient means of cooling/making ice since in those machines the water/ice is in direct contact with the cooling element unlike fridges that have to cool the air in order to cool the food/water.

Kate Nudd wrote:Here's an idea that I haven't figured out yet.


Radiational cooling occurs when infrared radiation is emitted from an object's surface, causing its temperature to decrease. On a clear night, infrared rays are emitted from the ground into the atmosphere, cooling the air down. This is why the night is extremely cold in the desert. Most people have experienced water's natural convection currents when warm water rises while cold water sinks and pools at the lowest level.

The cooling unit of the refrigerator (capacity 200 litres) is made of metal that has high thermal conductivity. A large volume of water (about 250 litres) is stored around this unit as a coolant. Radiator panels are placed on top so that the inner surface of the panel touches the coolant water. The heat of things stored in the cooling unit is conveyed to the surrounding water by the metal, and the heat goes up by natural convection. Thus it is conveyed to the radiator panel, and emitted through radiational cooling.

The system is most efficient on a clear night when there is less water vapor in the air. One clear night (and sometimes even one cloudy night) every three days can keep the temperature inside the refrigerator at around 7 to 8 degrees Celsius even on a mid-summer day. This innovative refrigerator belies our present-day common sense assumption that things cannot be refrigerated without electricity.
by Yasyuki Fujimura of Non-Electric Atelier

What are the radiator panels made of?
I look forward to other people's thoughts on this one

I've played around with radiative cooling at school but my intent was to condense water from the air rather than refrigeration. I used a styrofoam camping cooler with a glass sheet on top and sealed the edges. The heat would get sucked out of the box to the night sky which will cool the glass top. I also painted wax on the glass in a checkerboard patter. Glass is hydrophillic, attracts water, while wax repels it. The idea was that water would condense on the glass, spread and then touch the wax where it would run off. By pointing the glass box to the night sky I was able to drop the temp by a couple of degrees and collected 6 milliliters of water.

IMO, radiative cooling probably can't be used for refrigeration effectively and an evaporative cooler would probably be a better idea.

Erikgreen Hatfield wrote:

Also, I think a chest Frig would be better made from an old vertical frig because they aren't as deep.  An old frig, laid on its back and elevated off floor to countertop height would be easier to reach in and retrieve items.  They are more prevalent than old freezers and newer ones, better insulated.  Also a two door frig would give you a way to separate things.  Maybe the small door could be used for beverages, easier to get.

I'm HVAC certified. I spent several years working with air conditioning and refrigeration. This idea would require major modifications to make work. And it's not something your average weekend warrior could do. You'd have to almost completely re-plumb the refrigerant system.

Your first problem is the condenser coil (the one that dissipates the heat drawn out of the compartment by the refrigerant) is now directly under the compartment (the part you wanna keep cold). It doesn't take a genius to figure out what kind of problem this will create.

Your second problem, and this is the big one, is that the compressor MUST be oriented properly. If you lay an upright fridge on its back, all the oil in the compressor meant to lubricate the moving parts will leak into the cylinder(s). Now your moving parts are not properly lubricated and your cylinder is full of liquid (liquids don't compress).

If you lay an upright fridge on its back and just plug it in, you will ruin it.

sonic refrigeration if you can wait a while -- http://www.wired.com/science/discoveries/news/2003/01/57063

maybe not practical now, but i remembered seeing this in a newspaper years ago

"Off - Grid refridgerators - How do you do it?"

See absorption refrigeration. The internal refrigerant dictates the heat need for operation. CO2 (R744) comes into operation at lowest heat.
Extremely easy to home built by cut and weld of pipe, or may be off the floor purchased.

There is a thread around here on ice houses.

I have an Amish neighbor with one. He spent probably about a grand on materials (mostly foamboard and metal siding) to build a walk-in fridge. If he can't harvest ice from his pond, he buys block ice from one of the ice companies that supplies the grocery stores and gas stations. It costs him $400-500 a year if he buys all the ice.