food storage tech - umass amherst · low cost food storage technology: energy savings and produce...
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Ben Weil
Luke Doody
University of
Massachusetts
Amherst
LOW COST FOOD STORAGE
TECHNOLOGY: ENERGY
SAVINGS AND PRODUCE
STORAGE QUALITY
Department of the Interior. Bureau of Reclamation. Civilian Conservation Corps Division.1940
Traditional Root Cellar
-40
-20
0
20
40
60
80
100
0 2000 4000 6000 8000
Ou
tdo
or
Tem
pe
ratu
re (
°F)
Hours of the year
Outdoor temps in a typical model year for Chicopee
Refrigeration Temp range
Winter Storage Season
Median Temp
Psychrometric Chart
Psychrometric temperatures
Humidity Ratio
Relative Humidity
30% RH
50% RH
100% RH 120% RH?
Relative Humidity
Dry Bulb Temperature
Wet Bulb Temperature
Enthalpy
Simplified Psychrometric Chart
ASHRAE Comfort Zone & Veggie Comfort Zone
Humans
Fresh Veg
DX Cooling Process
Coil Temp
PROTOTYPE COOLER
UNIVERSITY OF MASSACHUSETTS
SOUTH DEERFIELD FARM
The Original Cooler
Insulated Floor 2X4 with ¾”
Plywood
DX Coil Refrigeration
4” Foam Panels with Metal Sheathing
Dimensions: 8’X8’X8’
Intake Fan 94 Watts
Exhaust Damper
Insulated Air Intake Duct
Compressor 547 Watts
Outdoor Air System
Spring Loaded Damper
Guards for Pests and
Debris
HumDisk 10 Centrifugal Humidifier 45 Watts
Dayton Humidistat
Continuous Water Source
Humidification System
Water Feed Housing
Air Circulation
Bathroom Exhaust Fan 37 Watts
Duct Releases Air in Opposite
Corner
Compressor Fan 283 Watts
Outdoor Air Control Panel
Outdoor Air Control
Thermostat Set to 44˚F
Energy Meter
Fan Speed Controller
Hobo Data Logger
Temperature Controls
Set Point
Cut Out Cut Out
Cut In
Cut In
38 37 36 35 34 33 32
Outdoor Fan Thermostat
Compressor Thermostat
˚F
BAROMETRIC PRESSURE: 29.656 in. HG
PSYCHROMETRICCHARTNormal TemperatureI-P Units
246 FEET
Weather Data Location:CHICOPEE_FALLS_WESTO, MASSACHUSETTS, USA
Weather Hours
22 to 144 to 23
66 to 45
88 to 67
110 to 89
132 to 111
154 to 133
176 to 155
198 to 177
-10 -5 0 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100 105 110 115 120 125 130
DRY BULB TEMPERATURE - °F
0 5 10 15 20 25 30
35
40
45
50
55
55
60
60
EN
TH
AL
PY
- B
TU
PE
R P
OU
ND
OF
DR
Y A
IR
0
5
10
15
20
25
30
35
40
45
50
ENTH
ALP
Y -
BTU
PER P
OUND O
F DRY A
IR
SATU
RATI
ON T
EM
PERATU
RE -
°F
.05
.1
.15
.2
.25
.3
.35
.4
.45
.5
.55
.6
.65
.7
.75
.8
.85
.9
.95
1
1.05
1.1
1.15
1.2
1.25
1.3
1.35
VA
PO
R P
RE
SS
UR
E -
IN
CH
ES
OF
ME
RC
UR
Y
0
10
20
25
30
35
40
45
50
55
60
65
70
75
80
85
DE
W P
OIN
T T
EM
PE
RA
TU
RE
- °
F
Chart by: HANDS DOWN SOFTWARE, www.handsdownsoftware.com
1.00
0.95
0.90
0.85
0.80
0.75
0.70
0.65
0.60
0.55
0.50
0.45
0.400.350.300.250.20SENSIBLE HEAT RATIO = Qs / Qt
SE
NS
IBLE
HE
AT
RA
TIO
= Q
s /
Qt
10
20
30
40
50
60
70
80
90
100
110
120
130
140
150
160
170
180
190
200
15%
25%
2%
4%
6%
8% RELATIVE HUMIDITY
10% RELATIVE HUMIDITY20%
30%
40%
50%
60%
70%
80%
90%
-50
05
510
1015
1520
2025
2530
30
35
35
40
40
45
45
50
5055
5560
6065
65 70
70 75
75
80
80
85 WET BULB TEM
PERATURE - °F
85
90
12.0
13.0
14.0
VO
LU
ME
- CU
.FT
. PE
R L
B. D
RY
AIR
HU
MID
ITY
RA
TIO
- G
RA
INS
OF
MO
IST
UR
E P
ER
PO
UN
D O
F D
RY
AIR
0
1.0 1.0
:-
2.0
4.08.0
-8.0-4.0-2.0
-1.0-0.5
-0.4
-0.3
-0.2
-0.1
0.10.
2
0.3
0.4
0.5
0.6
0.8
-2000
-1000
0
500
1000
1500
2000
3000
5000
-::
SENSIBLE HEAT Qs
TOTAL HEAT Qt
ENTHALPY
HUMIDITY RATIO
Dh
DW
Chart by: HANDS DOWN SOFTWARE, www.handsdownsoftware.com
BAROMETRIC PRESSURE: 29.656 in. HG
PSYCHROMETRICCHARTNormal TemperatureI-P Units
246 FEET
Chart by: HANDS DOWN SOFTWARE, www.handsdownsoftware.com
Weather for winter storage season (Nov-April) Western Mass.
BAROMETRIC PRESSURE: 29.548 in. HG
PSYCHROMETRICCHARTNormal TemperatureI-P Units
348 FEET
Weather Data Location:CONCORD_MUNICIPAL_ARPT, NEW_HAMPSHIRE, USA
Weather Hours
16 to 132 to 17
48 to 33
64 to 49
80 to 65
96 to 81
112 to 97
128 to 113
144 to 129
-10 -5 0 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100 105 110 115 120 125 130
DRY BULB TEMPERATURE - °F
0 5 10 15 20 25 30
35
40
45
50
55
55
60
60
EN
TH
AL
PY
- B
TU
PE
R P
OU
ND
OF
DR
Y A
IR
0
5
10
15
20
25
30
35
40
45
50
ENTH
ALP
Y -
BTU
PER P
OUND O
F DRY A
IR
SATU
RATI
ON T
EM
PERATU
RE -
°F
.05
.1
.15
.2
.25
.3
.35
.4
.45
.5
.55
.6
.65
.7
.75
.8
.85
.9
.95
1
1.05
1.1
1.15
1.2
1.25
1.3
1.35
VA
PO
R P
RE
SS
UR
E -
IN
CH
ES
OF
ME
RC
UR
Y
0
10
20
25
30
35
40
45
50
55
60
65
70
75
80
85
DE
W P
OIN
T T
EM
PE
RA
TU
RE
- °
F
Chart by: HANDS DOWN SOFTWARE, www.handsdownsoftware.com
1.00
0.95
0.90
0.85
0.80
0.75
0.70
0.65
0.60
0.55
0.50
0.45
0.400.350.300.250.20SENSIBLE HEAT RATIO = Qs / Qt
SE
NS
IBL
E H
EA
T R
AT
IO =
Qs / Q
t
10
20
30
40
50
60
70
80
90
100
110
120
130
140
150
160
170
180
190
200
15%
25%
2%
4%
6%
8% RELATIVE HUMIDITY
10% RELATIVE HUMIDITY20%
30%
40%
50%
60%
70%
80%
90%
-50
05
510
1015
1520
2025
2530
30
35
35
40
40
45
45
50
5055
5560
6065
65 70
70 75
75
80
80
85 WET BULB TEM
PERATURE - °F
85
90
12.0
13.0
14.0
VO
LU
ME
- CU
.FT
. PE
R L
B. D
RY
AIR
15.0
HU
MID
ITY
RA
TIO
- G
RA
INS
OF
MO
IST
UR
E P
ER
PO
UN
D O
F D
RY
AIR
0
1.0 1.0
:-
2.0
4.08.0
-8.0-4.0-2.0
-1.0-0.5
-0.4
-0.3
-0.2
-0.1
0.10.
2
0.3
0.4
0.5
0.6
0.8
-2000
-1000
0
500
1000
1500
2000
3000
5000
-::
SENSIBLE HEAT Qs
TOTAL HEAT Qt
ENTHALPY
HUMIDITY RATIO
Dh
DW
Chart by: HANDS DOWN SOFTWARE, www.handsdownsoftware.com
BAROMETRIC PRESSURE: 29.548 in. HG
PSYCHROMETRICCHARTNormal TemperatureI-P Units
348 FEET
Chart by: HANDS DOWN SOFTWARE, www.handsdownsoftware.com
Weather for winter storage season (Nov-April) Central NH.
Weather for winter storage season (Nov-April) North Central CT.
64
69
74
79
84
89
94
99
104
5
15
25
35
45
55
65
%R
H
°F
Conditions in Experimental Cooler and Conventional Cooler
outTemp, °F CoolerTemp, °F SGTemp, °F CoolerRH, % SGRH, %
Compressor
Outdoor temp above cutoff
0
2
4
6
8
10
12
14
16
Outside AirEvap
Conventional
kWh
/day
Fan
Compressor
Outdoor Fan
Circ Fan,Humidifier &Freeze protect
Energy Use
BAROMETRIC PRESSURE: 29.656 in. HG
PSYCHROMETRICCHARTNormal TemperatureI-P Units
246 FEET
Weather Data Location:CHICOPEE_FALLS_WESTO, MASSACHUSETTS, USA
Weather Hours
22 to 144 to 23
66 to 45
88 to 67
110 to 89
132 to 111
154 to 133
176 to 155
198 to 177
-10 -5 0 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100 105 110 115 120 125 130
DRY BULB TEMPERATURE - °F
0 5 10 15 20 25 30
35
40
45
50
55
55
60
60
EN
TH
AL
PY
- B
TU
PE
R P
OU
ND
OF
DR
Y A
IR
0
5
10
15
20
25
30
35
40
45
50
ENTH
ALP
Y -
BTU
PER P
OUND O
F DRY A
IR
SATU
RATI
ON T
EM
PERATU
RE -
°F
.05
.1
.15
.2
.25
.3
.35
.4
.45
.5
.55
.6
.65
.7
.75
.8
.85
.9
.95
1
1.05
1.1
1.15
1.2
1.25
1.3
1.35
VA
PO
R P
RE
SS
UR
E -
IN
CH
ES
OF
ME
RC
UR
Y
0
10
20
25
30
35
40
45
50
55
60
65
70
75
80
85
DE
W P
OIN
T T
EM
PE
RA
TU
RE
- °
F
Chart by: HANDS DOWN SOFTWARE, www.handsdownsoftware.com
1.00
0.95
0.90
0.85
0.80
0.75
0.70
0.65
0.60
0.55
0.50
0.45
0.400.350.300.250.20SENSIBLE HEAT RATIO = Qs / Qt
SE
NS
IBLE
HE
AT
RA
TIO
= Q
s /
Qt
10
20
30
40
50
60
70
80
90
100
110
120
130
140
150
160
170
180
190
200
15%
25%
2%
4%
6%
8% RELATIVE HUMIDITY
10% RELATIVE HUMIDITY20%
30%
40%
50%
60%
70%
80%
90%
-50
05
510
1015
1520
2025
2530
30
35
35
40
40
45
45
50
5055
5560
6065
65 70
70 75
75
80
80
85 WET BULB TEM
PERATURE - °F
85
90
12.0
13.0
14.0
VO
LU
ME
- CU
.FT
. PE
R L
B. D
RY
AIR
HU
MID
ITY
RA
TIO
- G
RA
INS
OF
MO
IST
UR
E P
ER
PO
UN
D O
F D
RY
AIR
0
1.0 1.0
:-
2.0
4.08.0
-8.0-4.0-2.0
-1.0-0.5
-0.4
-0.3
-0.2
-0.1
0.10.
2
0.3
0.4
0.5
0.6
0.8
-2000
-1000
0
500
1000
1500
2000
3000
5000
-::
SENSIBLE HEAT Qs
TOTAL HEAT Qt
ENTHALPY
HUMIDITY RATIO
Dh
DW
Chart by: HANDS DOWN SOFTWARE, www.handsdownsoftware.com
BAROMETRIC PRESSURE: 29.656 in. HG
PSYCHROMETRICCHARTNormal TemperatureI-P Units
246 FEET
Chart by: HANDS DOWN SOFTWARE, www.handsdownsoftware.com
Weather for winter storage season (Nov-April) Western Mass.
0
500
1000
1500
2000
2500
3000
3500
4000
4500
5000
Conventional Free Cooling EvapEnhanced
Ho
urs
(N
ov
- A
pri
l)
Weather-driven operating hours (for Chicopee, MA)
Compressor
Error
Economizer
$100.00
$150.00
$200.00
$250.00
$300.00
$350.00
$400.00
0
500
1000
1500
2000
2500
3000
Co
st
kWh
Energy usage and operating costs (based on
Chicopee, MA weather)
Compressor
Error
Economizer
Cost ($)
Item Cost Economizer only
Humdifier $900 N/A
Air intake fan $200 $200
Circ. fan $40 $40
Misc. $100 $100
Total $1,240 $340
Savings $213 $122
Simple Payback 2.91 Years 2.78 Years
First Cost and Simple Payback Period
Humidifier savings probably bigger at larger scales
• Prototype is only 800 ft3
• Identical setup can work up to 12,000 ft3
• Humidisk10 can work up to 20,000 ft3 at 1 ACH.
• 70 CFM Circ fans will have to be multiplied (approx. 1 for every 1000 ft3.)
DX Cooling Process
Coil Temp
Vapor Profile of a Carrot in Storage
Vapor Pressure: 0.414 kPa 35°F, 60% RH
Vapor Pressure: 0.689 kPa 35°F, Saturated
H20
Vapor Profile of a Carrot in Storage
Vapor Pressure: 0.662 kPa 35°F, 96% RH
Vapor Pressure: 0.689 kPa 35°F, Saturated
H20
Vapor Profile of Carrot in Storage in Winter
Vapor Pressure: 0.662 kPa 35°F, 96% RH
Vapor Pressure: 0.689 kPa 35°F, Saturated
H20
Vapor Pressure: 0.191 kPa 20°F, 50 % RH
H20
air
film
Inte
rio
r C
ove
r
Insulation
Ext.
Sh
eat
hin
g
Ext.
Fin
ish
o
ut
air
film
0 2 4 6 8 10
Inches
15
20
25
30
35
4020°F Outside
Cooling Process
0.00193 lbs H20/lb dry air
condensed
Vapor Profile of a Carrot in Storage in Summer
Vapor Pressure: 0.662 kPa 35°F, 96% RH
Vapor Pressure: 0.689 kPa 35°F, Saturated
H20
Vapor Pressure: 2.339 kPa 89°F, 50 % RH
H20
60°F Outside
Cooling Process
0.00446 lbs H20 / lb dry air
Condensed
20°F outside
60°F outside
90°F outside
Construction Elements
• Lots of insulation (R-20 min) on all sides including floor.
• Interior materials must be corrosion and rot resistant (metal, plastic, cement)
• Vapor barrier on interior (metal and plastic) • Minimum 2/3 of total R value must be air
impermeable and vapor retardant (foam board with sealed seams) interior of sheathing.
• Air tight construction. Test by pressurizing with fan and use theatrical fog or a moistened back of the hand.
Mechanical Elements
• circulation independent of compressor
• controlled fresh air exchanges
• Atomizing humidification system controlled by humidistat
• Temperature controlled by accurate thermostats
• Set points based on local weather characteristics
• Monitor with humidity and temperature sensors (data logging is preferable, but thermometer hygrometers are okay)
From Season extension to System extension?
• Short term market crop storage (e.g. tomatoes, greens, lettuce, etc.)
• Staged field heat reduction
• Any suggestions?
Questions?
• Thanks!
– USDA
– Ruth Hazzard
– Daniel Pepin
– Amanda Brown
– Simple Gifts Farm
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