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On-Farm Cold Storage Facilities Scott Sanford Sr. Outreach Specialist Rural Energy Program Biological Systems Engineering UW-Madison 1
On-Farm Cold Storage Facilities
Scott Sanford Sr. Outreach Specialist Rural Energy Program
Biological Systems Engineering UW-Madison
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Crop Storage Parameters l Type of Storage
l Crop Volumes l Bulk Storage l Containers
l Length of Storage l Short – up to 60 days l Long – 3-12 months
l Crop Compatibility l Temperature l Humidity l Ethylene l Odor
l Investment
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Root Cellars
l Energy Efficient l Use ground temperature l Outside air for cooling l Temperature subject to ambient temp
l Vent warm air / respiration gases ?? l Little/no electrical energy use (fans) l Not suitable for removing harvest heat
l Slow transfer of heat l Access for material handling??
l Can’t afford to hand carry crops in and out 3
Source: http://www.kk.org/streetuse/redneck_root_cellar.jpg
Modern Root Cellar Concept l Earth Contact basement
l Average ground temperature – 49F
l Office/living 2nd Floor l Why not under-ground?
l Fork Truck Accessible l $36,000 (2001)
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Potatoes Bulk Bins 42-45°F
Winter Squash on racks
50°F
Carrots pallets Bins
35-38°F Staging
Area
Modern Root Cellar Concept l Outside air cooling
l Outside air used when l Cooling is needed & l Outside air colder than inside
temperature
l Computer controlled l Fans and Dampers
l Mixing Fans & heaters
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More information at http://smfarm.cfans.umn.edu/rootcellar.htm
Refrigerators l Self contained l Great for smaller quantities l No humidity control l No planned air exchange l Space efficiency?
l Do containers fit shelving?
l Solid doors more energy efficient than glass l Limited capacity to remove field heat l Cost effective for small grower / short term storage
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Source: http://www.selectappliance.com/exec/ce-product/tl_g20000
Walk-in / Drive-in Coolers
l Workhorse of industry l Rule of thumb
l 2.5 to 3 cu. ft. of cooler volume per bushel l 1.24 cu ft / bushel – 50% utilization
l Modular or built-in-place l Features:
l Lockable door l Washable interior l Floor drain
l Well insulated walls l Temperature control l Insulated floor l Self closing door
7 Source: http://www.webstaurantstore.com/nor-lake-walk-in-cooler-6-x-12-x-6-7-indoor/596KLB612.html
Walk-in / Drive-in Coolers l Manufactured panels
l Modular tongue/groove panels l Walls and Roof l 2” to 12” thick
l Insulation l Closed Cell Foam
l 4” minimum (R-25) – 6” better (R-38) l Urethane or Polystyrene
l Vapor barriers l Installation
l Easy to assemble l Locking cams l Ceiling or floor to wall
l Cam locks or bolts l Caulk all seams 8
Source: http://www.kingspanpanels.us/ColdStorage/ThermalspanWall/200-Inverted-Rib.aspx
http://www.master-bilt.com/pdfs/io_manuals/walk-in_io.pdf
Built-in-place Cooler l Insulated walls –
l R-25 minimum (EPACT 2005) (R-30+ recommend)
l Fiberglass insulation NOT recommended l Wet insulation reduces insulation value
l Foam - Polyurethane / Polystyrene l R-value - 4 to 6.5 per inch
l Vapor barrier – warm side (not needed with Foam) l Year round storage – warm side changes
l Insulated floor l 1-2” foam board under concrete – 25 or 40 PSI rating foam
l Washable interior surface l Fiberglass / plastic / steel
l Drain – condensation / clean-up l Cost - ~ same as used cooler panels (labor & floor excluded)
l 12 x 12 x 8 – $5500 w/ refrigeration
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Insulation Materials l Foam – (4” minimum – 6” better))
l Types l Urethane (yellow) l Expanded Polystyrene (pink/blue)
l Insulation value – R-4 to R-6.5 l Foam in place – seals all edges l Rigid Board
l Tongue & groove – tape all seams l Double layer with offset seams
l Cover to protect l Steel / plastic corrugated sheeting l Fiberglass board
l Flammable – protect from heat sources l No vapor barrier needed 10
Foam Thickness
R-Value
3 19 4 25 5 31 6 38 8 50
10 63 12 75
Self-contained units l Truck/Trailer Reefer l Higher Heat losses/gain
l 2.25” to 3” foam
l Smaller refrigeration system l Designed to maintain the temperature of product
l Air flow may not be ideal l Access for Material Handling
11 Source: http://www.portablecoldstorage.com/
Refrigeration System – Direct Expansion
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Source: Refrigeration and Controlled Atmosphere Storage for Horticultural Crops – NRAES-22
In-Cooler
Pre-heat water
Types of Refrigerants l New systems – R404a l Used Systems
l Avoid l R-12 - restricted sales (ban as of Jan 1, 2015) l R22 - Jan 1, 2010 ban the use in new equipment
§ Production creases Jan 2020 § Can use a replacement refrigerant for existing equipment
l Acceptable Refrigerants l R134a – restricted sales (March 2004) l R404a l It is illegal to intentionally release any refrigerant
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Evaporator Fan motors l Can be higher cost to operate than compressors
l Run to promote air mixing l Evaporator Fan Controller
§ Reduces fan speed when compressor not running
l PSC – Permanent Split Capacitor (old) l Full load efficiency – 50-60% l Lower efficiency at lower speeds
l EC – Electronically Commutated (new) l Efficiency - 65 – 80% l Typically 30-50% energy savings
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Refrigeration Sizing
l Field heat removal l Heat of respiration l Conduction heat gain / loss l Convection heat gain / loss
l Infiltration l Air exchange (opening of door)
l Equipment heat gain l Lights, fans, fork truck
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Refrigeration Requirement l Field heat
Removal l Largest
component l Short duration l Smaller for Fall
harvested crops l ΔT x lbs x SH l Slow removal
effects produce 16
Source: Refrigeration and Controlled Atmosphere Storage for Horticultural Crops – NRAES-22
Precooling
l Hydro-cooling – Water bath l Forced air cooling l Ice Pack l Vacuum Cooling
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Heat of respiration table
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Source: Refrigeration and Controlled Atmosphere Storage for Horticultural Crops – NRAES-22
Refrigeration Sizing l Total refrigeration requirement
l Use maximum (worth case) values for each Qt = QFH+ Qresp+ Qcond+ Qinfil+ QEquip
l Capacity of refrigeration system Capacity = Qt x SF x DF
l SF = service factor, typically 1.1 to 1.2 l DF = defrost factor, typically 1.1 to 1.2 l One ton of Refrigeration = cooling based on
melting 2000 lbs of ice in 24 hrs l 288,000 Btu/24 hrs or 12,000 Btu/hr
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Compressor Capacity Recommendation for Small Coolers
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Source: Refrigeration and Controlled Atmosphere Storage for Horticultural Crops – NRAES-22
Small Refrigeration Systems l CoolBot Controller
l Over-rides standard window air conditioner controls l Cooling capacity less than rating at lower temps l Maybe lower capacity than require for field heat removal l Multiply units may be needed
l Self-Contained Refrigeration unit l Condenser, compressor & evaporator – one unit l Plug and Play – no Refrigeration tech needed l Higher / known capacity l Circulating fan l Roof top or side-mount l Inside or outside l Warranty
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Temperature Ranges for crops l Cold & Wet
l Beets, cabbage, carrots, turnips, parsnips l 32F & RH 95%+
l Cold & Dry l Onions / Garlic - 32F & RH 65-70%
l Cool & Wet l Potatoes - 40-50F & RH 95%
l Warm & Dry l Winter Squash - 50-55F & RH 50-70% l Sweet Potatoes - 55-60F & RH 80-85%
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Storage Guidelines for Fruits & Vegetables, E. de Long, S. Reiners, Cornell Cooperative Extension-Chemung Co., 2004 http://www.gardening.cornell.edu/factsheets/vegetables/storage.pdf
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Humidity control l Add moisture to air to
reduce crop moisture loss
l Evaporative cooler pad l Atomizer l Misting
l No water on crops l Pack in Plastic bag l Pack crops in damp sand or sawdust
25 Source: http://ivi-air.com/
Gellert Company
Humidistat l Accuracy range
l Range to 99% l Accuracy - 3-4% or less l Resolution – 1% or less
l Smallest display digit l Accuracy decreases >90%
l Remote sensor desirable l Locate in air flow
l Enclosure designed for wet environment
l Cost $130 - $500
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Humidity Control l Refrigeration dehumidifies air l Low temp drop à large evaporator surface area
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Source: Refrigeration and Controlled Atmosphere Storage for Horticultural Crops – NRAES-22
Outdoor air to reduce refrigeration l Exchange air l Controls
l Manual l Automatic
l Temperature l Time of day
l Disadvantage l Loss of humidity l Colder air is dryer
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Air Flow/Ventilation Patterns
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Cold storage – clearances & air flow pattern
l Nothing stacked above bottom of evaporator
l Wall clearance allows air to cool product
l Space under and between containers
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12-18” clearance
8-10” space
8-10” space
4-6” space
Air Flow with Plenum Wall
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• Horizontal slots in plenum wall • Bins stacked tight • 2-way fork slot – air duct
• Use for Force-Air pre-cooling • Humidification in plenum
Block end of fork slot
Plenum
Fan
Refrigeration Humidification
Bins & Tots l Materials:
l Wood – heavier, absorb moisture, repairable l Plastic – FDA approved, easily sanitized, repairable?
l Rated for loading l Stackable (without lid)
l Vented / solid sides / bottom l Minimum 8-11% of bottom open
l Handle with Fork Truck or Pallet Jack l Fit standard racking l Hand holes
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Racking l Allows better access to individual containers l Better ventilation and cooling l Keep containers off floor l Wire shelving – better air flow l Rolling racks for small walk-ins
33 Source: http://ervojic.hr/images/uploads/paletni-regali-velika.jpg http://www.ancostorage.co.uk/acatalog/Kwick_Rack.html http://www.martforcarts.com/carts/3.html
Material Handling Equipment l Pallet Jacks l Pallet Lift
l Need smooth level hard surface l Narrower aisle than needed for fork truck
l Fork Truck l Skid Steer w/ Pallet Forks
34 Source: http://www.beechhandlingservices.co.uk/ http://www.prestolifts.com/stuff/contentmgr/files/f243d69b64cf66fa30c5f6092fccb8ec/misc/pallet_stacker.jpg Source: http://www.getprice.com.au/images/uploadimg/910/350__1_pallet_jack.jpg
Layout Issues – Door Location
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• Door location doesn’t allow maximum number of containers
Layout Issues – Door Location
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• Allows last container to go straight in.
Layout for accessibility
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Rac
king
Aisle
• Add doors to reduce aisle space inside cooler • Small goods and Bulk area
Rac
king
Bulk Produce in Pallet Bins
Third Door for First in – First Out
Layout for accessibility
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Racking
Racking
Aisle
• Small quantities / fragile goods / packed produces
Racking
Bulk Produce in Pallet Bins
Small quantities / Packed produce
Planning!!! l Space requirements l Material Flow
l Access to processing area
l Material Handling l Utility needs
l Water l Electricity l Drains l Temperature
l Labor l Future Expansion 39
Cleaning
Packing
Storage
Office
Employee space
Produce from Fields
Flow Charts – by crop
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From Field Wash Bulk Bins Long-Term
Storage Oct - Feb
34°F
@ 95% RH Packing 5# mesh
bags
Short-term
Storage
Truck to Market
Sort by size
A & B
Culls – Food-bank /
Compost Pile Food Bank Compost
Loading Dock
Ramp to Fields
Building Layout
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Bath / Shower Room
Office
Lunch Rm / Employee Lockers
Cooler Access Alley
Cooler #1
Cooler #2
Cooler #3
Belt washer
Hydro-Cooler
Packing Line
Supply Storage Racks
Sorting equipment
Work Alleys
Economics of Storage Crops Factors to consider: l Cost to build and operate storage units l Facilities and capacity to move, wash and pack heavy, bulky items during the winter l Shrink (spoilage and grading) – 5 to 40% l Labor costs (benefits) l Markets and Pricing
l 20% higher costs l Handling/storage
l Risk and rewards l Cash flow during normally low period
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Storage Facility Capital Cost l Multiple units may be needed if you plan to
store different products l 12 x 12 cooler:
$8,000-$9000 (new) $4,000-$6,000 (used)
l 20 x 30 cooler: $20,000-$24,000 (new) $12,000-$14,000 (used)
l Electric costs to run cooler: l $2 to $4 per day. l Supplemental heating required
l Storage units in unheated building/outside 43
Storage Crop Case Studies
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Farm A Farm B Farm C Farm D Cubic Feet of Storage Space 812 6,000 17,374 22,400
Crops Roots, Alliums, Squash, Cabbage, Sweet Potatoes
Roots, Alliums, Squash, Cabbage
Roots, Cabbage, Alliums, Squash, Sweet Potatoes
Cabbage, Carrots, Butternut
Winter Labor Owner (2-4 hrs / wk)
Owner + 1 part-time (30 hrs / wk
Owner + 5.5 (80-90 hrs / wk)
Owner + 8 (280 hrs / wk)
Markets CSA (Direct Wholesale)
Direct Wholesale CSA and (f. mkts)
Direct Wholesale Distributor & (CSA)
Direct Wholesale (CSA)
Gross Sales $14,400 $85,000 $136,000 $250,000
Gross / cubic ft $18 $14 $8 $11
Person hours per $1000 in sales
2.4 7 11 24
Farm Storage Facility Loan Program
l Low interest financing l Fixed rate for 2.000% - 7yr, 2.625% - 10yr , 2.875% - 12 yr l Up to $500,000 l 15% down
l Build or upgrade storage and handling facility l New cold storage (Used equipment not eligible) l Framed structure or prefabricated permanently installed l Permanently affix equipment – refrigeration system, lighting,
controls l Useful life of 15 years or more
l Administered by Farm Service Agency l http://www.fsa.usda.gov/FSA/webapp?area=home&subject=prsu&topic=flp-fp
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Summary
l Know the storage requirements for each crop l Market within the expected storage duration l Plan storage facilities into work flow / traffic l Use Foam insulation!!! l Plan for expansion l Sanitize storage and containers between
seasons l Price produce to cover additional costs
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Resources l Bartsch, J.A.,G.D.Blanpied,”Refrigeration and Controlled Atmosphere
Storage for Horticultural Crops”, NRAES-22, Natural Resource, Agriculture and Engineering Service, Cornell U., Ithaca, NY, 1990. (Out of Print)
l Roper, T., K. Delahaut, B.Ingham., Storing fruits and vegetables from the home garden, A3823, University of Wisconsin-Extension, 2006.
http://learningstore.uwex.edu/Assets/pdfs/A3823.pdf l _____, The Commercial Storage of Fruits, Vegetables, and Florist and
Nursery Stocks, USDA-ARS, Agricultural Handbook Number 66, 2004. Available at http://www.ba.ars.usda.gov/hb66/contents.html
l De Long, Eric, Storage Guidelines for Fruits & Vegetables, Cornell Cooperative Extension, 2004. http://www.gardening.cornell.edu/factsheets/vegetables/storage.pdf
l Fruit & Vegetable Post Harvest & Storage Information – Website with data sheets on crops from Ambarella to Zinnia. http://www.postharvest.com.au/Produce_Information.htm
l Wilhoit, J., Low Cost Cold Storage Room for Market Growers, AEN-96, University of Kentucky Extension, 2009
http://www2.ca.uky.edu/agc/pubs/aen/aen96/aen96.pdf l Bubel, Mike & Nancy, Root Cellaring, 2nd Ed, Storey, Pownal, VT, 1991
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Questions??
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Scott Sanford Senior Outreach Specialist
Biological System Engineering University of Wisconsin [email protected]
608-262-5062
