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Sustainability wonders: Bicycle Clothes line Condom Library Pad Thai Lady bugs Ceiling fan & The root cellar

Why are these Unity College students so serious? Solving a community problem Enrolled in the Environmental Citizen Service Learning Supplying a Community Need

My first root cellar -- under the cabin in British Columbia: Straw-bale and adobe Trap door in the kitchen Worked great but got moldy

My second root cellar experience: Under the Straw-Bale house Bucket system with ropes Compact Worked great, got moldy

My third root cellar experience: 55 gallon barrels Into a hill, insulated top and front Worked great, taste from barrels and plywood coatings

Ravenwood, Maine Field stone foundation using slip-form methods Sandy soils Inexpensive Labor intensive Insulated walls

Frank and Libby鈥檚 Homestead Built along outside of house, not under Concrete walls, gravel floor, covered access Manual ventilation, fruit and vegetables

St. Lawrence Nursery Earth-Bermed and insulated Concrete roof Differential thermostat, active ventilation

Goranson鈥檚 Farm, Dresden, ME 20鈥� X 60鈥� Root Cellar Stores 70 tons of food Cost: $225K

100,000 Pounds of Potatoes 1000 Btu/ton/day Loose 10% in weight to evaporation 3鈥� Urethane on walls 5鈥� on ceiling

Ventilation Draw in nigh time air till below 45 deg. before storing crop Set differential thermostat at 36 inside, 50 deg. outside, in series Exhaust:12鈥� tube axial fan Intake: 18鈥� Dehydrates produce (need to add humidity and loosely wrap) Draws off ethylene

Currently designing Unity College鈥檚 Root Cellar 12鈥橷 8鈥� expandable Stores 2,500 pounds 4鈥� below grade Concrete footing, block walls, poured ceiling Active ventilation Uses stackable crates and hanging shelves

Root Cellar Design Stephen Belyea Maine Department of Agriculture, Food, and Rural Resources

Storage is a period of rest : Not too warm, not too cool. Not too humid, not too dry. Just right!

Vegetables Respire in Storage H2O CO2 O2 Heat Pathogens

2-3 22000 1.5-2.0 50-70 50-55 40 Squash 6-12 1000 1.0-1.5 95-100 38-45 40 Potato 6 1200 1.0-1.5 98-100 32-38 36 Cabbage 4-6 1500 1.0-1.5 98-100 32-35 40 Rutabaga 4-6 2200 0.5-1.0 90-98 32-40 48 Beet 7-9 4400 0.5-1.0 90-98 32-35 40 Carrot 3-4 1100 2.0-2.5 70-75 32-50 43 Garlic 1-8 1100 2.0-2.5 65-75 32-45 46 Onion Months Btu/ton/day cfm/cwt % deg. F #/cu.ft. Crop Time Resp. Airflow Humidity Temp. Density Heat of Rel Storage Bulk

Three General Storage Conditions Cool and Dry 鈥� onion and garlic Cool and Humid 鈥� carrot, beet, cabbage, rutabaga, potato Warm and Dry - squash

Do these conditions occur naturally on a consistent basis? Certainly Not! How can we provide the storage conditions our stored crops need? We need to be able to control the environment in our storages.

Factors in Effective Storage Environment Control Predictable storage space conditions Relatively air tight Insulated Protected from weather extremes Not subject to water infiltration

Factors in Effective Storage Environment Control Predictable storage space conditions: Mechanicals: Fan Cooler Humidifier Heater Controls

2-3 22000 1.5-2.0 50-70 50-55 32 Squash 6-12 1000 1.0-1.5 95-100 38-45 40 Potato 6 1200 1.0-1.5 98-100 32-38 36 Cabbage 4-6 1500 1.0-1.5 98-100 32-35 40 Rutabaga 4-6 2200 0.5-1.0 90-98 32-40 48 Beet 7-9 4400 0.5-1.0 90-98 32-35 40 Carrot 3-4 1100 2.0-2.5 70-75 32-50 43 Garlic 1-8 1100 2.0-2.5 65-75 32-45 46 Onion Months Btu/ton/day cfm/cwt % deg. F #/cu.ft. Crop Time Resp. Airflow Humidity Temp. Density Heat of Rel. Storage Bulk

Sizing a Storage Unit Assume that the bulk density is approximately 40 lbs. / cu.ft. Only 75% of floor space is usable. Good air circulation. Leave space for easy access to different products. Shelves or pallets increase the total capacity by more efficient space utilization.

Sizing Example 2 tons of winter squash Stored in 50 # totes 4,000 # / 50 #/tote = 80 totes Tote size 18 x 18 x 12 = 2.25 c.f. 4 layers high Footprint = 20 totes @ 2.25 s.f. x 125% = 56 s.f. of floor space

Storage Totes Footprint - Drawn to Scale In the Floor Plan

Ventilation Summer and early Fall 鈥� remove Field Heat and Heat of Respiration Usually requires refrigeration Usually short term storage Late Fall and Winter 鈥� remove heat of respiration Also have to consider heat gain through structure

Cooling with Outside Air Most economical cooling method Amount of cooling air required will vary significantly from day to day and week to week as outside air temperatures vary and as cooling load in the storage locker changes. Requires at least minimal controls

Shell Ventilation Cools inside of locker or storage room. Produce relies on air circulation through room and around bins / bags. Generally need 0.25 鈥� 0.50 cfm / cwt of stored product. Multiple fans or variable speed fans are most effective for varying conditions.

2 3 4 5 1 1 鈥� 24 hr. timer 2 鈥� Low Limit Thermostat 3 鈥� Inside Temperature Thermostat 4 鈥� Outside Temperature Thermostat 5 鈥� On / Off Switch Ventilation Fan Basic Ventilation Control Panel Components

Refrigeration Eliminates / minimizes vagaries of outside conditions or harvest temperatures. Requires more involved calculation of heat removal.

Calculating Cooling Load Contributors to cooling load: Field heat Heat of respiration Heat gain through structure Use Excel calculator or formulas in Refrigeration Manual

Cooling Load Calculations 12 x 20 storage room with 8 ft. ceiling 4 in styrofoam in ceiling and walls 2 in. styrofoam under concrete slab 1 pass door 3鈥� x 7鈥� Minimal traffic through door Minimal lighting 40F inside 75F outside / ground temperature 50F

Cooling Load - Structure Q = A dt / R Walls A = (20+20+12+12) x 8 = 512 s.f. dT = 75F outside 鈥� 40F inside = 35F R = 20 Q = 512 x 35 / 20 = 896 btu/hr. Ceiling A = (12 x 20) = 240 s.f. Q = 240 x 35 / 20 = 420 btu/hr.

Cooling Load - Structure Floor A = (12 x 20) = 240 s.f. Q = 240 x 10 / 5 = 480 btu / hr. Door A = (3 x 7) = 21 s.f. Q = (3 x 7) x 35 / 7.5 = 98 Summary Walls + ceiling + floor + door = 896 + 420 + 480 + 98 = 1894 btu / hr

Cooling Load 鈥� Field Heat 500 # corn @ 70F Specific heat = 0.79 Q = MCdT (btu/day) M = mass = 500 # C = specific heat = 0.79 btu/lb.-F dT = 24 temperature drop = 30F Q = 500 x 0.79 x 30 = 11,850 btu / day Q = 494 btu / hr.

Cooling Load 鈥� Heat of Respiration Q = MK M = mass (tons) K = respiratory heat production (btu/ton-day) Q = (500 # / 2,000 #/ton) x 20,000 = 0.25 x 20,000 = 5,000 btu / day = 208 btu / hr

Cooling Load - Infiltration Q = (ho 鈥� hi) x VN / 13.5 ho and hi are enthalpy values for outside and inside air (get values from Table 9). V = volume of room = 1,920 c.f. N = number of air changes per hour = 0.25 13.5 = ave. specific volume of air, c.f. / lb. Q = (38.62-15.23) x 1,920 x 0.25 / 13.5 = 832 btu / hr.

Cooling Load 鈥� Summary Total cooling load = structure + field heat + heat of respiration + infiltration = 1894 + 563 + 208 + 832 = 3,497 btu / hr.

Refrigeration Sizing Refrigeration sizing = calculated cooling load x Service Factor x Defrost Factor = 3,497 btu / hr. x 1.1 x 1.1 = 4,615 btu / hr. 1 ton of refrigeration = 12,000 btu / hr. Approx. 1 hp / ton of refrigeration

Commercial Refrigeration Condensor

Air Conditioner Cool Bot Application?

Easy Access / Easy Clean Up Well Lighted

Questions 鈥� and maybe Answers

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Rootcellar design, Steve Belyea & Jim Merkel

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