“We Bring Engineering

to Life”

Biological and Agricultural Engineering

On-Farm Energy Assessment of New

Curing BarnsGrant Ellington

North Carolina State University

2010 2011 2012 2013 2014 2015 2016 2017 2018 2019 20200

5

10

15

20

25Propane Natural Gas

2011

Dol

lars

per

Mill

ion

BT

U

Source: U.S. Energy Information Administration (LP Gas – Wholesale/Resale; N.G. – Commercial)

LP Gas and Natural Gas Price Outlook

$15 / MMBTU @ $1.10/gal

$9.40 / MMBTU @ $0.75/therm

Variables Effecting Energy Consumption• Barn energy efficiency (insulation, structural air leaks)• Heat exchanger efficiency• Burner firing rate• Ambient temperatures • Curing management• Quantity of tobacco• Quality of tobacco• Curing energy efficiency quantified as pounds cured leaf

per unit of fuel (lbs/gal LP)

Tytun

Long

World Tobacco

New Barn Specifications• Long (10-box)

– Long HEx @ 350,000 Btu/hr

• World Tobacco (15-box)– Evans HEx @ 500,000+ Btu/hr – 2” insulated panels

• Tytun (14-box, 32T)– Powermatic HEx @ 400,000 Btu/hr – 4” insulated panels

• All fan motors 10 hp, 1-phase • All barn pads insulated (3/4” blue board)• Suretrol controllers

World Tobacco Long Tytun Existing Long

2-Aug 29-Aug 16-Sep   2-Aug 29-Aug 16-Sep   2-Aug 29-Aug 16-Sep   2-Aug 29-Aug 16-Sep

Barn Temperature (oF) NA 150 145 NA 150 145 NA 150 145 NA 168 145

 

Exhaust Gas Temperature (oF) 575 616 601 312 355 345 352 370 369 NA 360 387

Thermal Efficiency (%) 79.2 76.9 77.5   82.1 80 80.4   86.8 86.5 85.8   NA 84.3 83.5

Stack Gas Analyzer Results(Averages)

0 48 96 144 192 240 288 336 384 432 480 528 576 62480

90

100

110

120

130

140

150

160

170

180Long (db) Long World (db) World (wb) Tytun (db)

Time (hrs)

Tem

per

atu

re (

oF)

Temperature Profiles Cures 6-8

0 1 2 3 4 5 6 7 80

50

100

150

200

250

300

350

World Long Tytun

Time (Days)

Fu

el (

Gal

lon

s)

0 1 2 3 4 5 6 7 80

200

400

600

800

1000

1200

1400

1600World Long Tytun

Time (Days)

Ele

ctri

cal E

nerg

y (

kWh)

0 1 2 3 4 5 6 7 80

20

40

60

80

100

120

World Long Tytun

Time (Days)

Fu

el (

Gal

lon

s)

New Barn Cumulative and Daily Energy Usage(Cure 7)

0 24 48 72 96 120 144 16880

90

100

110

120

130

140

150

160

170

180

0

20

40

60

80

100

World Fuel Usage Long Fuel Usage Tytun Fuel Usage

Time (hrs)

Tem

per

atu

re (

oF)

LP

Gas

(ga

ls)

New Barn Daily Fuel Usage (Cure 7)

0 500 1000 1500 2000 2500 3000 3500 4000 4500 5000 55000

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9Tytun Long World

Time Units (5 minute intervals)

Stati

c Pr

essu

re A

cros

s To

bacc

o (i

n. H

2O)

Static Pressure Across Tobacco vs Time (Cures 4 & 5)

lb/ft3

10.010.410.4

lb/ft3

12.512.212.0

Cures Avg. Cure Time (hrs)

Total Fuel (gal)

Avg. per cure (gal)

Total Electrical (kWh)

Total Green Wt. (lb)

Total Cured Wt. (lb) lb /gal LP

World Tobacco (15 Box)

8 181 2,399 300 10,483 176,500 35,952 15.35

Long (10 Box)

8 172 2,422 303 11,301 179,000 35,917 14.94

Tytun (14 Box)

8 156 2,171 271 9,862 183,400 37,458 17.26

Existing Long (10 Box)

6 206 *1,584 NA 9,127 132,500 23,849 13.25

Existing DeCloet (13 Box)

8 184 2,223 278 7,748 149,930 27,283 12.64

             

* 5 Cures

2013 Energy Performance Summary

  Fuel Cost ($/unit)

0.80 1.00 1.20 1.40 1.60 1.80 2.00

lb/gal $ / lb Cured

7 0.114 0.143 0.171 0.200 0.229 0.257 0.286

8 0.100 0.125 0.150 0.175 0.200 0.225 0.250

9 0.089 0.111 0.133 0.156 0.178 0.200 0.222

10 0.080 0.100 0.120 0.140 0.160 0.180 0.200

11 0.073 0.091 0.109 0.127 0.145 0.164 0.182

12 0.067 0.083 0.100 0.117 0.133 0.150 0.167

13 0.062 0.077 0.092 0.108 0.123 0.138 0.154

15 0.053 0.067 0.080 0.093 0.107 0.120 0.133

17 0.047 0.059 0.071 0.082 0.094 0.106 0.118

Energy Efficiency and Estimated Cost per Pound Cured Leaf (fuel only)

Summary• New barn energy efficiency was approximately 22%

higher compared to existing barns on average• New barns purchased to replace aging curing

infrastructure and to better handle existing production• 5 barn manufacturers made and sold barns in 2013• Energy performance alone is not the single justification

for purchasing a given barn make, but is an important factor

• Performance comparisons and competition should result in improving barn design

• Plan to continue work in 2014 and include additional barns

Acknowledgements• NC Tobacco Research Commission• Philip Morris International• Altria Client Services• Alliance One International• Japan Tobacco International• Lake Wendell Farming Co.• Triple B Farms• Scott Farms• DMG Farms • Patterson Farms• Allen Newton• Mac Grady Farms• R.A. Wood Farms• Dennis R. Wood