Lighting Systems and Energy Efficiency on Dairy Farms

November 14, 2013for

MILK ∙ LAIT 2020, Moncton, NB, Canada

John P. Chastain, Ph.D.Professor and Extension Agricultural Engineer

School of Agricultural, Forest, and Environmental Sciences

Electrical Energy Use on Dairy Farms Old study (1987) on 5 freestall dairies in

Kentucky: 502 to 699 kWh/cow/yr. (34 to 100 cows, 63 avg)

New study (2005) in New York (Ludington & Peterson):

1. 14, Tie-stall dairies: 542 to 1561 kWh/cow/yr (42 to 140 cows. 77 avg)

2. 18, Freestall dairies: 424 to 1,736 kWh/cow/yr. (65 to 860 cows, 244 avg).

So based on these data we can conclude that on the average…

Old Freestall New Freestall Tie-stall

596 kWh/cow/yr 811 kWh/cow/yr 934 kWh/cow/yr

1. In 1987 dairy farms were more energy efficient than in 2005.

2. Tie-stall barns are at a significant disadvantage since they use more electricity per cow.

3. Energy cost are more important now than ever.

Really? What am I forgetting?Old Freestall New Freestall Tie-stall

596 kWh/cow/yr 811 kWh/cow/yr 934 kWh/cow/yr

1. In 1987 dairy arms were more energy efficient than in 2005.

2. Tiestall barns are at a significant disadvantage since they use more electricity per cow. 3. Energy cost are more important now than

ever.

Dairy farms typically sell milk not cows.

Average Electricity Use Based on Milk Production

Old Freestall New Freestall Tie-stall

63 cows 244 cows 77 cows

14,073 lb/cow 24,897 lb/cow 20,582 lb/cow

63.95 hL/cow 113.14 hL/cow 93.53 hL/cow

596 kWh/cow/yr 811 kWh/cow/yr 934 kWh/cow/yr

4.24 kWh/cwt 3.26 kWh/cwt 4.54 kWh/cwt

9.32 kWh/hL 7.17 kWh/hL 9.99 kWh/hL

Electrical use per amount of milk produced is a better indicator of efficiency than electrical use per cow.

Breakdown of electrical energy used has changed.

1987 Freestall

2005 Freestall

2005Tie-stall

Water Heating 31.5% 2.1% 10.3%

Milk Cooling 17.8% 26.0% 23.2%

Vacuum Pump 24.3% 17.1% 18.0%

Other 26.4% 54.8% 48.5%

Total Dairy 100.0% 100.0% 100.0%

1. Water heating is more efficient.

2. New uses of electricity has caused the “other” to double.

Breakdown of electrical energy use from New York audits (Ludington and Peterson, 2005)

Tie-stall FreestallWater Heating 10.3% 2.1%

Milk Cooling 23.2% 26.0%

Vacuum Pump 18.0% 17.1%

Lighting 16.6% 26.0%

Ventilation 20.9% 21.8%

Feeding 7.2% 1.4%

Manure Handling 2.7% 4.4%

Miscellaneous 1.0% 1.2%

Electrical uses for manure management

Water Heating – Heating Efficiency

Electric is most efficient at 100%. Gas and oil is about 80%. Heat is lost in flue

gases. Condensing type reclaim flue gas heat and can

have heating efficiencies as high as 95% ($). Electric is more efficient, but fuel cost is

important. Oil or gas may cost less. LP ($/gal) = Electric Price ($/kWh) x 21.096 10 cents/kWh = $2.21/gal LP = $0.58/L LP

Water Heating – Standby losses can be over 50% of energy use. Replacing a water heater? Buy the most efficient

one possible. Tank insulation reduces standby losses. More insulation the better.

Electric water heaters are easiest to insulate and have standby losses of 0.5% to 1% per hour or 12% to 24% per day.

Typical gas or oil heater standby loss is 2.5%/hr or 60% per day.

Insulate hot water pipes to reduce standby losses.

Water Heating – Only use what is needed. Fix water leaks. Consider having your pipeline washing system

adjusted to reduce the amount of water needed to wash the milking system.

Are milk lines too large? Correct sizing saves water and energy.

Pre-rinse water only needs to be 100° to 110°F (38 to 43 C). Too high can cause deposition of milk solids.

Use cold or tepid water for the acid rinse.

Water Heating – Use waste heat to your advantage.

Milk must be cooled from 95°F (35 C) to 40°F (4 C). Most dairy refrigeration systems dump heat to the air. A refrigeration heat recovery unit (RHR) is a heat

exchanger & tank that is designed to capture the waste heat from milk cooling to pre-heat water before it enters the water heater.

Can save as much as 50% of the energy needed for water heating. Payback often highest for electric WH.

Use water directly from the RHR tank when hot water is not needed.

Milk Cooling – Maintenance saves money.

Keep area around condenser ventilated with cool air and in the shade if possible.

Cooling capacity is reduced by 6°F (3 C) for every 10°F (6 C) increase in air temperature.

Dirty air-cooled condensers are less efficient. Make cleaning a part of your routine.

Repair refrigerant leaks – no bubbles in the sight glass.

Outdoor Condenser Better airflow than indoors. Would be better if shade was

provided in summer. Easy to clean. I like a shed that can be

closed in winter and opened in summer in cold climates. Can use heat for milkroom in winter.

Milk Cooling – Type of compressor makes a difference.

Most compressors are of the reciprocating type

Scroll compressors have less moving parts and are more energy efficient.

Replacement of an old hermetically sealed reciprocating compressor with a scroll compressor can save 15% to 20% in milk cooling.

Slightly more expensive.($525 CAD)

Milk Cooling – Advanced Systems ($) More efficient but may not be

cost effective for small herd sizes.

Shell and tube water-cooled condenser common.

Two-stage instant cooling can cool milk to 38°F (3 C) before entering the tank.

Photo courtesy of DeLaval

Milk Cooling – Refrigeration Heat Recovery (RHR) A RHR unit will capture waste heat to reduce

water heating costs, and will improve milk cooling efficiency for an air cooled compressor.

Increases the effective heat exchanger area in condenser.

May not be as beneficial when used with an efficient well water pre-cooler. Less heat needs to be removed by refrigeration system.

Milk Cooling – Precoolers are often the easiest to implement.

Heat exchanger that uses well water to cool the milk before it reaches the bulk tank.

Can reduce milk temperature by 20°F (11C) to 40°F (22C).

Can reduce milk cooling costs by 30% to 60%. Can improve milk quality. Improper matching of milk and water flow rates

is greatest problem. May need a surge tank for low water flow systems.

Effect of Precooling on Energy UseSystem Description Measured kWh/cwt

Air-cooled, reciprocating 1.0 (0.8 to 1.2)

Addition of well water pre-cooler

0.75 (0.6 to 0.9)

Average Measured Savings = 25%

Source: Ludington and Peterson, 2005

Adding a VFD to the receiver pump can drop average use to 0.55 kWh/cwt and provide a savings of 45%. ($)

What to do with the water from the precooler? Don’t waste it! Cows drink about 3 times as much water as

they give in milk. Cows like to drink tepid water. One of the best uses of precooler water is to

use it to supply waterers. Helps to keep waterers in cold barns from

freezing in winter. May need an insulated storage tank in some

cases.

Milking System – Proper sizing saves energy. Many older vacuum pumps were sized based

on “more is better”. Research has shown 3 cfm per milking unit

plus a 35 cfm base capacity for up to 32 units is typically adequate to prevent falloff problems.

May be able to reduce pump speed or a new pump may be in order.

Saving Energy Used for Milking Maintain belt tension and condition to save

energy. Check vacuum levels. If they are not at the

desired level system efficiency and udder health may be compromised.

Check vacuum pump motor temperature. High temperature indicates motor overload and can be an indication of motor or voltage problems.

Variable Frequency Drive (VFD) on Vacuum Pump Changes motor speed by variation of electrical

frequency. Maintains efficiency at lower speeds. Reduces noise – good for cows & people. Can save 50% in electrical costs. Milk 8 hours / day? Typically a good payback.

Milk 6 hours / day? Check the benefits. Payback is often too long on smaller dairies.

Savings Potential with VFDVacuum Pump (Source: NATC)

Without VFD With VFD

Pump Size 10 hp 10 hp

Milking hours/day 12 12

Average load (kW) 9 kW 4.5 kW

Energy Use 108 kWh/day 54 kWh/day

Annual Cost ($0.10/kWh) $3,942/yr $1,971/yr

Annual Savings $1,971/yr

VFD Cost $4,100

Simple payback 2.08 years

Use of Fans for Ventilation and Mixing has Increased. Ventilation provides air

exchange. Mixing improves air

velocities past animals during hot weather and helps with heat stress.

Air velocities in the range of 400 to 600 fpm (2 to 3 m/s) help.

So what do we look for in an energy efficient fan?

What we do not look for…

Number of fan blades Fan diameter - exclusively Cool looking fan housing Metal versus plastic

The fan must be designed for use in agricultural buildings, and it must be a rated for air flow and efficiency at the required pressure drop.

Fan test data for a particular fan can be obtained on line from…

Bioenvironmental and Structural Systems LaboratoryUniversity of Illinois

Department of Agricultural and Biological Engineering 332 Agricultural Engineering

Sciences Building 1304 W. Pennsylvania Avenue

Urbana, Illinois 61801Ph. 217-333-9406 Fax 217-244-0323

http://www.bess.uiuc.edu/

Need some definitions Airflow is measured in cfm – cubic feet per

minute. Static pressure drop (ΔP) is a measure of how

hard a fan is loaded. It is measured in inches of water using a manometer.

The amount of power the fan motor requires is measured in Watts (W).

Fan efficiency is determined by dividing airflow by power or cfm / W.

The high efficiency fan moves 20% more air at 0.05 and 0.10 inches of water.

48 inch diameter fans, 1 hp - belt drive

2080022000

1720018400

0

5000

10000

15000

20000

25000

0.00 0.05 0.10 0.15 0.20 0.25

Static Pressure Drop (inches of water)

Air

flo

w (

cfm

)

High Efficiency Low Efficiency

The high efficiency fan is 32% to 33% more energy efficient.

48 inch diameter fans, 1hp - belt drive

20.5

22.9

15.517.2

0

5

10

15

20

25

30

0.00 0.05 0.10 0.15 0.20 0.25

Static Pressure Drop (inches of water)

Fan

Eff

icie

ncy

(cf

m /

Wat

t)

High Efficiency Low Efficiency

Select energy efficient fans at 0.10 inches of water in most cases.

Fan Diameter Efficiency range

Minimum to be high efficiency

@ 0.10

24 inch 8.7 to 19.4 cfm/W

11.9 cfm/W

36 inch 12.7 to 23.7 cfm/W

16.2 cfm/W

48 inch 13.5 to 27.0 cfm/W

17.6 cfm/W

Sources: ASABE EP566 and A3784-6, UW Extension

Shutter design is also important.

Butterfly Shutters seem to provide the least air flow restriction and maintenance problems.

From Chore-Time web site.

We also need to consider how well the fan will move air if we have a strong head wind.

The engineers at the BESS lab provide an air flow ratio (AFR).

The AFR is the air flow at 0.20 inches of ΔP divided by the air flow at 0.05 inches of ΔP.

Air flow ratio is a measure of the steepness of the fan curve. The higher the better.

Minimum airflow ratio is 0.7

Select efficient fans that… Provide the required amount of air flow at

0.10 inches of water. Have a minimum air flow ratio of 0.7 to make

sure adequate ventilation is provided during windy conditions.

Select the highest cfm/W using these criteria.

Retrofit Ventilation System for a 103-Cow Tie-stall Barn in Minnesota

Replaced old fans and improved inlets

Overall ventilation efficiency was increased from 14 to 18.6 cfm/W

Efficiency was increased by 33%

Payback for efficient fans can range from 1.2 to 3 years.

New mechanical ventilation in 100-cow barn in Minnesota corrected air quality problems in winter.

Carbon Dioxide Ammonia

Old System 5000 ppm 25 ppm

TARGET 3000 ppm 15 ppm

New System 2500 15 ppm

Outside temperature was -20°F or -28 C.

High-Volume, Low-Speed (HVLS) Fans Are More Efficient Than Basket Fans

Comparison of Mixing Fans to HVLS in Freestall Barns

315 ft (96 m) freestall barns requires 6, 24 ft (7.3 m) diameter HVLS fans @ 1.65 kW/fan

Total load for HVLS = 9.9 kW Same building would need 30, 36” basket

fans. @ 0.57 kW/fan (See BESS web site.) Total load for basket fans = 17.1 kW HVLS will save 42% in energy cost for same

operating hours.

Fan Maintenance Is ImportantA study by Janni et al. (2005) has shown that the actual airflow delivered by a fan can be 20% to 50% lower than the BESS fan test data if the fan is dirty, shutters do not work properly, or the belts are loose.

Janni, K.A., L.D. Jacobson, R.E. Nicolai, B. Hetchler, and V. J. Johnson. 2005. Airflow reduction of large belt-driven exhaust ventilation fans with shutters and loose belts. In Livestock Environment VII, Proc. of the 7th International Symposium, ASABE.

Lighting Proper lighting is needed for worker and

animal safety Can increase worker productivity 8 to 13%

(office work) Can improve quality of work (20% reduction

in defects) Photoperiod control can improve milk

production by about 5 lb/cow-day or 2.2 L/cow-day

Need the right amount and quality of light based on tasks Parlor pit – 50 fc (540 lux = lumen/m2) Parlor stalls & return lanes – 20 fc (216 lux) Holding area – 10 fc (108 lux) General lighting in barn – 20 fc (216 lux) Minimum amount needed for photoperiod control –

10 fc (108 lux) Need CRI of 80+ in places like the parlor and office. Uniformity also important in parlor and animal

handling areas (spacing/mounting height, 0.87 – 2.0).

Types of Lighting & Key Characteristics

Lamp Type

Lamp Size (W)

CRI

Efficacy (Lumens/ W)

Typical Lamp Life (hr)

Incandescent 34 - 200 100 11 - 20 750-2,000 Halogen 50 - 150 100 18 - 25 2,000 - 3000 Fluorescent 32 - 110 70 - 95 75 - 98 15,000 - 20,000 Compact Fluor. 5 - 50 80 - 90 50 - 80 10,000 Metal Halide 70 - 400 60 - 80 60 - 94 7500 - 10,000 High Pressure Sodium 35 - 1000 20 - 80 63 - 125 15,000 - 24,000 LED 5 - 22 70 - 95 50 - 100 15,000 – 50,000

Compact Fluorescent Vs. Incandescent Energy savings is about 70%. Lamp use = 8 hr/day: payback period is about

0.36 yr. Lamp use = 2 hr/day: payback period is about

1.5 yr. Problem with CFLs is they tend to burn out

early if turned off and on. CFLs contain mercury, a hazardous waste.

T8 Tube Fluorescent Vs. Incandescent Energy savings is about 52%. Ballast increases

use. Lamp use = 8 hr/day: payback period is about

3.1 yr. Lamp use = 2 hr/day: payback period is about

12 yr. More reliable lamp life than CFL. Burned out lamps also a hazardous waste.

T8 Fluorescent Lamps Reduce Energy Use Compared to T12 by 29% to 35%.

Recommendations for low-bay & office applications Eliminate incandescent lamps Use CFLs for simple lamp swaps. Use T8 tube fluorescents if a complete system retrofit

is needed.(T5s don’t seem to last.) LED lighting will overtake CFLs in the near future

similar efficiency, longer life, non-hazardous waste, dimmable, good cold temperature starting.

Price of 40W to 60W replacement LEDs have decreased to $10 - $12.

Lamps appear to meet typical life of 25,000 hr

Energy Efficient Options for High-Bay Applications – Freestall Barns, Parlors

High Pressure Sodium Metal Halide Best lighting uniformity provided

using bulbs in the range of 150W to 250W.

400W may work at mounting heights of 20 ft (6 m) or more.

Low-bay HPS is in the range of 10 to 12 ft. (3.05 to 3.66 m) Fixtures are available Need to use 100W to 150W lamps. Promotes better uniformity. If designed correctly energy use is the same.

LED for High Bay Is Available

LED High Bay VS. 250W HPS250W HPS LED High Bay

Fixture + Lamp

$280 $290

Rated Life 24,000 hrs 100,000 hr ?

Lumens 25,200 avg. 11,200

Lumens/W 100 77

1. 2.25 LED fixtures will be needed to equal one HPS.

2. So the longer life of LED cost twice as much and is 30% less efficient.

Winter Day Length is not Optimal for Dairy Cows in Northern Latitudes.

Can you get some “free quota” with this in the fall?

Supplemental Lighting Needed to Provide 16 hours/day if Natural Light Can be Used.

Tie-Stall Barn: Provided 10 fc with 32W T8 Fluorescent Lamps Spaced 12 ft (3.66m). Controlled with timer to provide 16 hr/day.

Supplemental Lighting in Tie-Stall Barns Yields a 6% to 8% increase in Milk Production

Increase in milk production paid for lighting over mangers, control timer, and additional feed cost in 4 months assuming with an 8% increase in milk (6% increase in DM).

If milk production increased by only 4% the payback was still 267 days.

Tie-stall dairies can implement this relatively easily.

Does not include cost of additional quota.

Supplemental Lighting in Freestall Barns Using HPS – can use MH or LED in future. Control lights with timer and

photocell. Open ridge provides natural

light during the day. 8% increase in milk provided

a payback in 2 months. 4% increase in milk provided

a payback in 124 days No quota cost included.

Conclusions Efficient water heating is common. Many are using precoolers. Use the water. Opportunities to save energy in milking and

cooling. Use efficient ventilation Use efficient mixing fans to reduce heat stress. Efficient lighting is needed and photoperiod control

could provide an opportunity ($). Reduce the cost of making purchased quota.