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Energy FundamentalsEnergy Fundamentalsfor Farm Lightingfor Farm Lighting

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(USDA Census of Agriculture, 2007)

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Proper lighting should:

• Provide a safe, effective working environment

• Deliver proper light level

for animals

• Be energy efficient

• Be cost effective

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Lumens:• Quantity of light

output (lm)

Average rated life:• Number of hours for

half of the bulbs to burn out in lab tests

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Efficiency:• Lumens/Watt• Example:

– 1200 lm/20 W = 60

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Foot-candles (fc):• Level of light at a

working surface

• One fc is amount of illumination from a candle falling on a surface at a distance of one foot

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Incandescent• Most common currently• Least energy efficient• Cheapest initial cost• Shortest life • Being phased out from

retail− 100 W – Jan 1, 2012− 75 W – Jan 1, 2013− 60 & 40 W – Jan 1, 2014

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Compact Fluorescent (CFL)

• 10 times more life than incandescent

• 75% less energy usage• Should be rated for moist

and dusty environment• Enclosure globes can

shorten life

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Light Emitting Diodes (LED)• Five times more efficient than incandescent• Long rated life (near 100,000 hrs)• Directional lighting• Currently limited in damp or

dusty environments• Improving efficiency and costs

every six months… stay tuned

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Tube Fluorescent • T 12 (1.5” diameter)

− Phasing out (bulbs July 2012)• T 8 (1” diameter)

− 4x more efficient than incandescent− < 12’ off floor− Mount electromagnetic ballast in weatherproof fixtures

• T 5 (0.6” diameter)− Shorter and more efficient than T8− Only good in clean-dry environments currently

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CFL Type of Lamp

Incandescent

23 W Input Wattage

100 W

69.6 lm/w

1600 lm/23 W Efficiency 15.8 lm/w 1580 lm/100 W

67.2 kWh 0.023 kW x 2920 hr

Energy Use 292 kWh 0.1 kW x 2920 hr

$6.72 67.2 kWh x $0.10 Energy cost/yr

$29.20 292 kWh x $0.10

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Economic comparison example:• 23 W CFL (1600lm) vs. 100 W incandescent (1580

lm)• Used 8 hours per day (2920 hrs)• Electricity is $0.10/kWh

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CFL Type of Lamp

Incandescent

23 W Input Wattage

100 W

12,000 hrs

Rated life 1500 hrs

6,000 hrs 50% of rated Assumed life

750 hrs 50% of rated

0.49 bulbs

2920 hrs/6000 hrs

Bulbs/yr 3.9 bulbs 2920 hr/750 hrs

$3.19 Cost/bulb $0.45$1.56/yr $3.19 x 0.49

bulbsBulb cost/yr $1.75/yr $0.45 x 3.9

bulbs

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• 23 W CFL (1600lm) vs. 100 W incandescent (1580 lm)

• Used 8 hours per day (2920 hrs)• Electricity is $0.10/kWh

CFL Type of Lamp Incandescent23 W Input

Wattage100 W

$6.72 67.2 kWh x $0.10

Energy cost/yr

$29.20 292 kWh x $0.10

$1.56/yr $3.19 x 0.49 bulbs

Bulb cost/yr $1.75/yr $0.45 x 3.9 bulbs

$8.28/yr $6.72 + $1.56 Annual Cost $30.95/yr

$29.20 + $1.75

$22.67/yr $30.95 - $8.28 Savings0.14 yrs $3.19/$22.67 Payback

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• 23 W CFL (1600lm) vs. 100 W incandescent (1580 lm)

• Used 8 hours per day (2920 hrs)• Electricity is $0.10/kWh

SUMMARY:• Adequate light level is important to meet basic

needs in facilities in a safe manner• There are multiple options for efficient indoor

lighting• Be aware of the impact of dust and humidity on

light in your lighting decision• Include initial cost of wiring and fixtures when

looking for cost savings• Appropriate disposal measures should be taken

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FOR MORE INFORMATION:• Google “ISU farm energy” or visit us online at

http://farmenergy.exnet.iastate.edu• Download ISU Farm Energy publications at no

charge• Follow us on Twitter @ISU_Farm_Energy for

updates• Ask your local utility provider to contact us!

http://farmenergy.exnet.iastate.edu

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http://farmenergy.exnet.iastate.edu