Low Cost Cold Storage

2016 Indiana Small Farms ConferenceJohn Wilhoit

Thistles End Farm

Versailles, Kentucky

Room Air Conditioner Unit Used for Refrigeration Advantages

Low cost Easy to install

Disadvantages Coils will freeze up if you attempt to cool below about 60˚ F Makeshift way to overcome this problem (using strip

heaters, a thermostat, and a timer to create a defrost cycle) is cumbersome to rig up and hard to maintain

“CoolBot” control unit overcomes limitations of using air conditioner for refrigeration

Available from Store it Cold, LLC1 for about $300 Prevents freeze up by cycling the compressor on and off

based on sensor readings of room temperature and frost on the cooling coils and by “fooling” the air conditioner’s temperature sensor with a tiny micro-heater

Can cool down to 33˚ F with sufficient capacity air conditioner

Simple digital controls and readout Very simple to install

1Mention or display of a trademark, proprietary product, or firm in text or figures does not constitute an endorsement and does not imply approval to the exclusion of other suitable products or firms.

Requires certain brands of air conditioners that have plastic temperature sensors (does not work metal temperature sensors)

Use without filter and front grill on the AC unit Insert frost sensor into fins, free AC’s temperature sensor and

attach CoolBot’s micro-heater to it Installation takes only a few minutes

Low cost cold room for using CoolBot

• Constructed from readily available building materials.

•Room measures 8 ft x 10 ft x 8 ft tall, large enough for substantial

walk-in cold storage space, but small enough to fit into many existing

barns or other covered storage spaces.

•Floors, walls, and ceiling constructed using 2 x 6 or 2 x 4 studs and

plywood sheathing inside and out.

•Floors, walls, and ceiling insulated with batt insulation and foam

board to an R-value of 19.

•Since this is a cooler, vapor barriers are to the outside (the hotter

side) of the constructed walls.

Foam board with taped joints forms vapor barrier on the outsideConstructed with skids on the bottom so it can be dragged around, or even lifted with large forklift

“Walk-in” space of 8’x10’x8’ tall cold room

University of Kentucky Extension Publication AEN 96. Link available at:

https://www.uky.edu/bae/specialty-crop-plans-publications-presentations

Link to construction plans schematic at:

https://www.uky.edu/bae/specialty-crop-plans-publications-presentations

Link to materials and price list at:

http://www.bae.uky.edu/ext/Specialty_Crops/

Additional considerations for low cost cold storage room construction

Floor drain Floor insulation Alternative to batt insulation Material Estimator for Walk-in Cooler Alternative structures or construction Low-cost methods for forced-air cooling to

remove field heat

Concrete Floor

Cold Room

< 55˚F

= 55˚F

Ground (soil)

Concrete Floor

Cold Room

>55˚F

Ground (soil)

= 55˚F

Floor Insulation important for improved efficiency if cooler used for very cold temperatures

Foam board instead of batt insulation

Disadvantages of batt insulation Loses much of its insulating value if it gets wet Can harbor mold if it gets wet

Foam board as alternative to batt insulation R-value of 5 per inch thickness 4 inch thickness would not fit within 2x4 stud

walls Estimated additional cost of $500-600 for

equivalent insulating value of batt insulation used in this cold room

Construction of Cold Room with Foam Board Insulation

Construction of Cold Room with Foam Board Insulation

Note use of expanded foam for thoroughly sealing between foam board and studs.

Construction of Cold Room with Foam Board Insulation

Note vapor barrier with sealed seams to the outside.

University of Wisconsin –Extension Web Site

Link at: http://fyi.uwex.edu/cropstorage/on-site-built-walk-in-coolers/Note web site strongly recommends against use of batt insulation.

University of Wisconsin –Extension Walk-in Cooler Material Estimator

Link at: http://fyi.uwex.edu/cropstorage/on-site-built-walk-in-coolers/

Alternatives to Constructed Cold Room

Old or defunct cold storage structures can be refurbished at very low cost using the CoolBot for refrigeration.

Low cost cold room can be made from recycled materials such as these insulated panels.Manufacturers (such as that make garage door panels) sometimes have scraps available at very low cost.

Prefab Insulated Buildings

Prefab buildings advertised insulated to R-16, surprisingly cheap ($1700 for 10’x10’ in 2013). Cheaper than you could build one, although it will be less energy efficient.

Prefab Insulated Buildings

Sandwich material similar to insulated panels used for garage doors. Good water resistant surface, fairly resilient.

Converting Existing Room/Structure for Cold Storage

Concrete block room inside a larger structure, insulated and AC unit with Coolbot installed in door.

Converting Existing Room/Structure for Cold Storage

Insulated on inside with foam board.

Converting Existing Room/Structure for Cold Storage

Floor insulated with foam board covered by plywood.

NC State extension publication available at:

http:// www.bae.ncsu.edu/programs/extension/publicat/postharv/ag-414-7/index.html

Different fruit and vegetables have different temperature requirements for storage For market growers, many items like squash,

cucumbers, peppers & watermelon do best at 45-60 ˚F.

Tomatoes subject to chilling injury if stored too cold (< 50 ˚F).

Different fruits and vegetables also have different humidity requirements. Best to oversize AC unit if higher humidity is needed.

HortFact-7002, “Recommended Storage Conditions for Vegetables” available at: www.uky.edu/Ag/Horticulture/comveggie.html