Low Cost Cold Room Using CoolBot for Refrigeration

2012 Mid-Atlantic Fruit & Vegetable ConventionJohn Wilhoit, Extension Specialist

Biosystems & Agricultural Engineering Department University of 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

Link to construction plans schematic at:

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

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 Alternative materials or structures 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 wetCan harbor mold if it gets wet

Foam board as alternative to batt insulationR-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

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.

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

http://www.uky.edu/Ag/Horticulture/HortFact7002.pdf

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

NC State extension publication available at:

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