Lighting Systems and Energy
Efficiency on Dairy Farms
November 14, 2013
for
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
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2.
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):
14, Tie-stall dairies: 542 to 1561 kWh/cow/yr
(42 to 140 cows. 77 avg)
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
2005
Tie-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)
Water Heating
Milk Cooling
Vacuum Pump
Lighting
Ventilation
Feeding
Manure Handling
Miscellaneous
Tie-stall
Freestall
10.3%
23.2%
18.0%
16.6%
20.9%
7.2%
2.7%
1.0%
2.1%
26.0%
17.1%
26.0%
21.8%
1.4%
4.4%
1.2%
Electrical uses for manure management
Water Heating – Heating Efficiency
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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.
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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.
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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.
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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.
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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
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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.
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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.($525 CAD)
Milk Cooling – Advanced Systems ($)
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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)
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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.
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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 Use
System Description
Measured kWh/cwt
Air-cooled, reciprocating
1.0 (0.8 to 1.2)
Addition of well water pre0.75 (0.6 to 0.9)
cooler
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!
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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.
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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
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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
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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 VFD
Vacuum Pump (Source: NATC)
Without VFD
Pump Size
10 hp
Milking hours/day
12
Average load (kW)
9 kW
Energy Use
108 kWh/day
Annual Cost ($0.10/kWh)
$3,942/yr
Annual Savings
VFD Cost
Simple payback
With VFD
10 hp
12
4.5 kW
54 kWh/day
$1,971/yr
$1,971/yr
$4,100
2.08 years
Use of Fans for Ventilation and Mixing has
Increased.
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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…
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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 Laboratory
University of Illinois
Department of Agricultural and Biological Engineering
332 Agricultural Engineering
Sciences Building
1304 W. Pennsylvania Avenue
Urbana, Illinois 61801
Ph. 217-333-9406
Fax 217-244-0323
http://www.bess.uiuc.edu/
Need some definitions
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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.
25000
22000
20800
20000
18400
Airflow (cfm)
17200
15000
High Efficiency
Low Efficiency
10000
5000
48 inch diameter fans, 1 hp - belt drive
0
0.00
0.05
0.10
0.15
0.20
Static Pressure Drop (inches of water)
0.25
The high efficiency fan is 32% to 33% more
energy efficient.
30
Fan Efficiency (cfm / Watt)
48 inch diameter fans, 1hp - belt drive
25
22.9
20.5
20
17.2
15.5
15
10
High Efficiency
Low Efficiency
5
0
0.00
0.05
0.10
0.15
0.20
Static Pressure Drop (inches of water)
0.25
Select energy efficient fans at 0.10 inches
of water in most cases.
Fan Diameter
24 inch
36 inch
48 inch
Minimum to be
Efficiency range high efficiency
@ 0.10
8.7 to 19.4
11.9 cfm/W
cfm/W
12.7 to 23.7
16.2 cfm/W
cfm/W
13.5 to 27.0
17.6 cfm/W
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.
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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…
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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
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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
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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 Important
A 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
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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
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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
Incandescent
Halogen
Fluorescent
Compact Fluor.
Metal Halide
High Pressure Sodium
LED
Lamp Size
(W)
34 - 200
50 - 150
32 - 110
5 - 50
70 - 400
35 - 1000
5 - 22
CRI
100
100
70 - 95
80 - 90
60 - 80
20 - 80
70 - 95
Efficacy
(Lumens/ W)
11 - 20
18 - 25
75 - 98
50 - 80
60 - 94
63 - 125
50 - 100
Typical Lamp Life
(hr)
750-2,000
2,000 - 3000
15,000 - 20,000
10,000
7500 - 10,000
15,000 - 24,000
15,000 – 50,000
Compact Fluorescent Vs. Incandescent
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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
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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
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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
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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)
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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 HPS
250W HPS
$280
LED High Bay
$290
Fixture +
Lamp
Rated Life
24,000 hrs
100,000 hr ?
Lumens
25,200 avg.
11,200
Lumens/W
100
77
1. 2.25 LED fixtures will be needed to equal one HPS.
2. So the longer life of LED cost twice as much and is
30% less efficient.
Winter Day Length is not Optimal for
Dairy Cows in Northern Latitudes.
Can you get some
“free quota” with
this in the fall?
Supplemental Lighting Needed to Provide 16
hours/day if Natural Light Can be Used.
Tie-Stall Barn: Provided 10 fc with 32W T8 Fluorescent
Lamps Spaced 12 ft (3.66m).
Controlled with timer to provide 16 hr/day.
Supplemental Lighting in Tie-Stall Barns Yields
a 6% to 8% increase in Milk Production
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Increase in milk production paid for lighting
over mangers, control timer, and additional
feed cost in 4 months assuming with an 8%
increase in milk (6% increase in DM).
If milk production increased by only 4% the
payback was still 267 days.
Tie-stall dairies can implement this relatively
easily.
Does not include cost of additional quota.
Supplemental Lighting in Freestall Barns
Using HPS – can use MH or LED in future.
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Control lights with timer and
photocell.
Open ridge provides natural
light during the day.
8% increase in milk provided
a payback in 2 months.
4% increase in milk provided
a payback in 124 days
No quota cost included.
Conclusions
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Efficient water heating is common.
Many are using precoolers. Use the water.
Opportunities to save energy in milking and
cooling.
Use efficient ventilation
Use efficient mixing fans to reduce heat stress.
Efficient lighting is needed and photoperiod
control could provide an opportunity ($).
Reduce the cost of making purchased quota.