food storage tech - umass amherst · low cost food storage technology: energy savings and produce...

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




246 FEET


Weather for winter storage season (Nov-April) Western Mass.



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


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


1.00

0.95

0.90

0.85

0.80

0.75

0.70

0.65

0.60

0.55

0.50

0.45


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%



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




348 FEET


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, Â°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



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


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


1.00

0.95

0.90

0.85

0.80

0.75

0.70

0.65

0.60

0.55

0.50

0.45


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%



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




246 FEET


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



H20

Vapor Profile of Carrot in Storage in Winter



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



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

food storage tech - umass amherst · low cost food storage technology: energy savings and produce...

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