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Passive cooling system to turn a root cellar into a cooler all year round

 
Posts: 12
Location: Albany, VT
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We are looking to build a root cellar on our farm in northern Vermont, that can serve as a cooler in the warmer months of the year. We plan on holding onto the cold of winter by freezing tanks of water inside the root cellar utilizing a closed loop system of pipes containing butane. The plan is explained in writing, pics and video in our Indiegogo campaign below

Root Cellar/Passive Cooler at Peace of Earth Farm

We are trying to raise enough funds to enable this project and be able to build and monitor this cooling system. The concept has been tested by a friend of ours in a smaller, less insulated situation. He was able to easily freeze a tank approximately 4 cubic ft and hold ice until late July/early August. We think we can hold onto ice and its cooling power longer than that in a space that will stay cool longer (a root cellar). We'll have to play around with the number of tanks needed to maintain the temperature in the space, and also how the tanks are insulated to balance holding the ice vs cooling the space. I welcome any questions you have about the project or suggestions based on similar experience.

If you think this is research that would be valuable to you or others, please consider contributing to our Indiegogo campaign and helping us spread the word!

Thank you
Rebecca Beidler
 
Posts: 249
Location: Central Texas zone 8a, 800 chill hours 28 blessed inches of rain
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I am looking forward to going through your plans to learn what I can.

I would encourage you to also consider, beyond the ice blocks, investigating geothermal cooling. Ground temperature is fairly stable below 4 feet from the surface. In VT, I bet that is a stable temp between 40 to 45 degrees year round. Digging a pit or trench down below the 4 foot mark, place HDPE pipe between 4 and 6 inch diameter and cover with soil. With both ends above ground, one is the output pipe which is mounted to a DC (computer) fan, powered by a small solar panel draws air the length of pipe with the input end in a cool shaded place (north side of the root cellar?) The air is cooled to near ground temp (below 45 degrees) as it passes through the coils. This will help keep your entire cellar cooler after the ice has melted.
 
Rebecca Beidler
Posts: 12
Location: Albany, VT
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Jack Edmondson, the whole passive cooler/root cellar will be underground. Only the door will be exposed and will need to be insulated well. I think that should help the space maintain the constant temperatures you mentioned without needing any additional trenches and fans. Please correct me if I'm missing your point. We are thinking that having the tanks of water in the root cellar will help cool down the space earlier in the fall, even if they are not frozen at that point. Often traditional root cellars are not quite cool enough when you want to pull things out of the garden in September/October.
 
Posts: 53
Location: Newfoundland
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While I like the idea of the water tanks, the repeated freeze/thaw might not be ideal. You'd easily burst the pipes eventually.
You might not even need water tanks to keep the area cooler in the summer.
Properly built and insulated, a root cellar would remain cool and ambient all year round, even in the summer, as long as you leave the door closed.
By introducing the tanks, and ice blocks, your not making a cellar, your making an underground freezer, and it's entirely different, especially with moisture.

Ideally, around here, 5ish Newfoundland, cellars aren't dug out of hillsides unless needed because of space, that interrupts the local ground water drainage, etc and introduces the risk of to much moisture. The old timers would simply pick a spot with drainage, or between hills and large rocks, most were simply built directly ontop of undisturbed soil in a spot in the garden where nothing would grow(usually over a scath of rock). They'd make a box room in general, with a strong roof, then pile stone and sod, building it up, all around the box, then heaping it over to make a thick natural roof. Then as they eventually cleaned out more rocks from the gardens over time, they'd end up thrown and heaped around the cellar and it'd become it's own hill. They only fell out of favour when, because of the WW2, most of the men who did the maintenance were laboured off or went to war. Without maintenance, they easily became susceptible to rats who dug out the sod, and inbetween the rocks(at least that's what happened local to me and my family), then the returning men brought with them electricity and proper refrigeration units(yes, most rural villages around here didn't get power or town running water until the 60's, or later).

In the last half of the 1900's, basements were regarded as cellars and treated as such. A shed, workshop or even a house was built over top with as good an insulated floor/ceiling they could arrange for, and things like the boiler, was kept at ground level, most people didn't have furnaces but still use wood stoves.

They're a lot like mini-Hobbit holes. Hobbit homes were initially inspired and described as actually being root-cellars. Much of the same technology and building aspects of a hobbit-house would apply to root-cellars.

They're generally out of favour because root-cellars aren't exactly tidy little things that most people expect. A decent sized root-cellar has a ground foot-print nearly the same size of the tiny salt-box houses, most that I've seen in person have a ground foot print the size of a single-car garage, and people simply don't have the space. These styles of root-cellars were used all year round, generally kept dry, and kept things like milk, butter and cheese cool enough during summer days that they didn't spoil(generally because a family would go thru it before that happened, but they were used to store daily meals).
But, I have to admit, that most of these same places are built on the ocean, and everyone has a stage head on a wharf in general that had a fish box(a plastic insulated double-walled ice box about the size of a hot tub since about the 70's, before then, a wooden chest with a metal pan with a drain that would run out) that they'd stuff with ice, either cut out of the ocean during the winter, or refilled during the summer with ice from ice-burgs.

If your settled on having ice as a cooling source, you should consider instead getting a double-wall plastic container, filling it half full of iceblocks during the winter, or frozen bottles or buckets of water, then piling good sawdust ontop and around, then putting a board over it, for storing the things you want really chilled on top. But, even if you keep it cool, to much moisture will rot most veg eventually, and keep in mind that you'll want to be able to drain the thing at some point. As long as this container is kept out of the sun, in a room without a window and the doors closed, and the lid kept locked down unless your using it, this should keep the ice mostly frozen. Do you have any hope of keeping food frozen in there? Nope, it won't freeze things, and it won't keep 'real' ice cream frozen(most of the commercial stuff these days is made of some kind of cream/froth and isn't actually real milk just google for unmeltable ice cream bars). But it will delay thaw out, and it will keep unopened milk longer than a fridge does, in general.

Some links with a lot of pictures of local root cellars, old and modern.
http://www.townofelliston.ca/2at/rootcellars.html#cellar
http://doodledaddle.blogspot.ca/search/label/root%20cellars
http://collections.mun.ca/cdm/search/collection/ich_nature/searchterm/Root%20Cellar%20Traditions/field/subcol/mode/all/conn/and/cosuppress/
 
Rebecca Beidler
Posts: 12
Location: Albany, VT
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Alice, thanks for all the historical root cellar info from Newfoundland. While our project is an experiment with some unknown outcomes, I don't think that the freezing/thawing of pipes will be an issue. The pipes only contain butane, not water, and butane freezes somewhere around -220F, yes, that 0 is not a typo. From what I understand the water in the tanks will get colder and colder until it freezes from the inside out, which doesn't stress the container in the same way as freezing normally does. Time will tell whether the addition of ice tanks to the root cellar could make the cellar too cold in the winter months as you suggest. If that is the case I think we could insulate more heavily around the tanks, keeping the cold from adding to the root cellar space until it is needed later into the spring. Most root cellars in our area stay cool in the summer months, but not refrigerator temps (the low 40s), that is what we are aiming for. Our soil is almost pure sand and we will take care to manage drainage around the cellar so that excess moisture is not a problem.
 
pollinator
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I really don't understand why the over-complicated system of pipes and butane?

It has some "cool factor" to it, but simply using sawdust to cover blocks of ice would not only get you the lower temperatures you want, and it would do so year-round. Sawdust covered ice in a proper ice house just does not melt.

I could see sawdust might be an issue in North Dakota somewhere, but in Vermont I would think sawdust would be easy to get. I live in Maine and it is. In fact I once figured it out that for every 13 cords of tree length firewood that is produced, 1 cord of wood is converted to sawdust in the bucking process. A chainsaw has a 3/8 kerf after all.

Cut firewood
Cut ice
Cover ice with resulting sawdust from cutting firewood

Butane, propane, ammonia...they all would work, but the question is why, when organic matter that would do the same thing is readily available. Am I missing something?
 
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