Short season walk in cooler for tree seedling storage.

Submitted by sgbotsford on Sun, 12/13/2015 - 3:42pm

Tool Concept

Stage:

DIY

License:

This work is licensed under a Creative Commons Attribution 4.0 International License.

Description:

Under development: I'm building an ice house. I buy tree seedlings for resale and my own use. Stored in shade, seedlings can be kept for about 3 weeks. I hope to extend this to 10 weeks using a cold room. Version 1 is an insulated 10x10 shed (R12 fiberglass in walls and ceiling) In this shed, I'm putting 10 200 liter barrels of water (2/3 full) to freeze. Barrels are on blocks so the bottom will freeze faster. Water surface is covered with 3" of Styrofoam peanuts to slow down the top freezing I'm hoping this will prevent or reduce bulging, and that expansion will take place in the center of the top, much like an ice cube in the fridge. The tops of barrels are covered in 2" styrofoam plank. Boxes of seedlings are top of the styrofoam. A thermostat will run a fan to maintain the temperature at the seedlings between 0 and 2 C (32 to 35 F)

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Documentation

Documentation Wiki:

Bill of materials

Existing shed
10 plastic 45 (55 US) gallon barrels. (Surplus from antifreeze company)
10-15 cublc feet styrofoam peanuts (Shippers supply or Edmonton Reuse center)
Blocking to support barrels (Old pallets, cut in sections)
Dual input differential thermostat
Door Switch to turn turn off fan when door is opened.
Styrofoam for barrel tops. (Home building store)
6" 120v fan (Princess Auto
Weather stripping
Window box fan
Electric heater

Other tools needed to build this tool

Chainsaw or sawsall (To cut up pallets)
Electricians tools (wiring up thermostat, switched outlet...)
Jigsaw

Step-by-step build instructions

Clean shed. Squirrels found it a nice place.
Patch holes in corners (squirrels again) by screwing pieces of 3/4" OSB to block holes.
Patch roof (Shed was used for boiler, and flashing was not in good shape.
Rework old stack as an exit vent for exhausting warm air during the chilling season. (Plug with a wad of fiberglass insulation in spring)
Rework door, adding styrofoam on inside face. New doorstops, and seals to make tight.
Bring in barrels.
Bring in blocking.
Using jigsaw, cut a 6" hole in the middle of the top of the barrel. If you are patient, you can try putting 4" of peanuts through the bung, but I'm not.
Fill barrels 2/3 to 3/4 full with water. If you wish to experiment make a variety of levels and inspect for damage in spring.
Wire up differential thermostat to operate small intake fan whenever outside temperature is below inside temperature.
Wire up thermostat to turn operate circlation fan when temps get above 2
Wire up 2nd thermostat to operate heater when temperatures are below -1 (At seasons start the ice and the foundations of the building are at temps of about -20 to -30 C (0 to -20 F) While trees need to be cold, they must NOT freeze)
Wire up 3rd thermsostat to operate alarm if temps get down to -2
Wire up door switch to shut off circulation fan when door is open

Future development

This is a proof of principle, and a temporary stopgap.

Version 2 differs as follows:

Strawbale walls (R32-R40)
Rafter and steel roof
8" EPS type 2 celing (R32)
24x30 feet
Ice stored as a frozen pond in the middle of the room, covered with insulated deck.

Not clear at this point if such a room will freeze deeper than about 18" It may be necessary to circulate antifreeze through pipes from outside to freeze the bottom of the pond.

Sources

Barrels: I put an ad on Kijiji for these, and have companies that call me when they have 30 or so barrels to pick up.

Differential Thermostats: Hard to find. Two sources

The first is simpler and cheaper. The second is more programmable, and can be attached to more than just temperature probes.

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User Manual

User Manual Wiki:

Theory of operation

The whole idea of this: Store cooth from the time it's plentiful (winter) to time it's needed.

Ice takes some 330 kJ per kg to melt. A barrel with 210 liter capacity fllled with 150 liters has 150 kg of water/ice. That's about 27,000 kJ If the ice was further chilled to -30, I get another 9000 kJ.

A kJ is about a BTU (within 5%)

A 10x10 shed has 320 square feet of wall and 100 square feet of ceiling. Assuming R12 batts, we need (320 +100) square feet / R12 = 35 BTU per hour per degree F. So 840 BTU per day per F. A worst case spring day it's 25 C outside (75 F) To keep it at 35 F we have a differential temperature of 40 degrees. So it will take 48,000 BTU per worst day. More than a barrel. More realistically we get days that peak in the low 60' F and get close to freezing at night.

In practice we still have frosts in early May and highs of only 25 in mid July

https://docs.google.com/spreadsheets/d/12kGdYqsC-hsjTw9duqJ6M8OVP6jagSSAZHefBJeuckY/edit?usp=sharing

is a link with my cooler calculations. TL:Dr; 10 barrels should last me to the middle of June. This ignores coolth stored in the ground,which after a winter with the door open should be considerable. It also ignores air infiltration, cold air loss when the door is open.

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