Refrigerator: harnessing the winter cold

My apologies if I should do more research before starting this topic, but I haven't quite found what I am looking for and wanted to see what you folks might have to say about this idea.


Off-grid/power limited/energy conscious fridge modification using coolant that cycles between outside and the fridge in your kitchen. The system would be a closed loop, using some kind of antifreeze/coolant, a pump (possibly thermosiphon, specifics dependent), and tubing/piping that runs outside into the cold winter and inside your kitchen and into your fridge, and possibly a thermostat to activate the pump.


Previously I had looked into simply ducting cold air from outside into your fridge, but this presents challenges such as:
-may require larger diameter holes in your fridge and house walls
-humidity issues
-air leakage, more potential for pests to enter system

A liquid cooled system would have some benefits:
-easier to control flow of liquid
-smaller diameter holes needed in fridge and house walls


The system could use copper tubing and coils, and could possibly include one or two radiators to collect and dissipate heat/cold.


Could this system work? What would the drawbacks be? How would you approach this? Is it worth it?


In my climate average outside temperatures are below fridge temperatures, often significantly, for approximately 7 months of the year.



There are other ways to improve the efficiency of your fridge:
-keep your house colder or keep fridge in cold part of house
-bring ice blocks from outside into the fridge
-potentially insulate the cold box portion of the fridge (don't insulate your compressor area)
-keep it clean
-etc etc.
But, I am interested in ways to cut the fridge's winter energy consumption greatly.

J.R., I have long considered trying this. It's completely bonkers that a cold glycol loop is not incorporated into fridges for northern climates. I guess they're designed for Florida, and mass production means we get the same units here.

The biggest risk is freezing the contents of your fridge. We store all of our hard-earned carrots and beets in the spare fridge, and I can tell you it's a very unhappy day if/when it fails and gets too cold. By the time you realize it, all your summer work has started to rot.

The challenge is to remove just enough heat so the compressor kicks in less, saving electricity. Automation could do this, but maybe a simple hand pump into a double-wall reservoir in the fridge would do it. Hmm. An external thermometer readout would tell you when it's time to crank the handle as you're walking to the coffee machine. Hmmm...

Other options, as you've noted: Some people try to insulate their fridges from the outside. Others make sure any spare space if filled with liquid in containers, which stays cold much longer than air due to its mass. Come to think of it: we have been tossing tetra-paks from vegetable stock into recycling. These would be handy sized "space fillers" in the fridge, filled with water.

A cool space is better for a fridge/freezer. But too cold a space actually means the compressor runs more; it relies on temperature differential within a certain range.

"It's completely bonkers that a cold glycol loop is not incorporated into fridges for northern climates."

Agreed!

Keeping the fridge full of liquid (Tetra packs would be a good choice for this!) certainly helps, but ultimately it may provide an additional chore, even if a relatively small one. Same goes for bringing ice in from outside.

Yes, unintended frozen veg is no fun.. perhaps this is where a thermostat tied in to the system would be useful (I've edited the original post to include the thermostat).

To avoid freezing in the fridge, the outside portion of the loop could possibly be buried in the ground, and potentially in snow (though I suspect the snow would melt or otherwise be affected). This may moderate the temperature of the coolant, even keeping it around the 4C mark, which may be perfect for assisting the fridge in keeping cool.

I'm also tired of listening to the fridge's compressor... I briefly had a propane fridge and generally enjoyed how quiet it was.

J. Rosseau wrote:To avoid freezing the outside portion of the loop could possibly be buried in the ground, and potentially in snow (though I suspect the snow would melt or otherwise be affected). This may moderate the temperature of the coolant, even keeping it around the 4C mark, which may be perfect for assisting the fridge in keeping cool.

Good idea! It could be buried on the outside of a house's concrete foundation. Just cool enough, and just warm enough.

J. Rosseau wrote:I'm also tired of listening to the fridge's compressor... I briefly had a propane fridge and generally enjoyed how quiet it was.

Haha, only country dwellers will understand this! The city has a baseline hum that cancels most of this out.

I wander if a simple one gallon container could go inside of the fridge with piping going up to the attic or roof such that the warm(40 degree F)solution thermosiphoning up
and the cold(20 degree  F) attic solution falling down.
Maybe a solenoid valve and thermostat in the loop somewhere too.

I want to build a cold room that uses ducted exhaust from a heat pump water heater. Maybe the room could be like a bucket with the warm air going out the top and the heat pump discharge air falling into the bottom. A little fan
could come on when the room gets too cold. Did a little math and the heat pump water heater would do the cooling of about one hour of a five ton air cond. About 60,000 BTU a day(5000BTU an hour) cooling or less considering some of the heat used to heat the water comes from the the compressor motor and such. Those cool bots don't use much large of a window AC unit than 6000BTU)

Douglas Alpenstock wrote:
Other options, as you've noted: Some people try to insulate their fridges from the outside.

For others reading this thread and getting ideas, make sure to not insulate the part of the fridge where the heat is supposed to escape. In some cases it may be prohibitively complex to add very much insulation value at all since large parts of the surface may be designed as heat sinks. Fridges work by pumping heat from inside to the outside, but if you insulate around them it will trap that heat and make them inefficient, run all the time, and prone to failure.

It's also worth noting that if the fridge is electric, inside your house, and you're heating that house with electricity, any inefficiencies in the fridge will be in the form of waste heat which would otherwise need to be created by your primary heating system. This means that during the cold months you might not be saving energy by modifying/upgrading your fridge - though your could certainly improve your peace of mind by making it run less if it's noisy.