Control Strategies and Considerations for Livestock and Other Farm Buildings Kevin A Janni Bioproducts & Biosystems Engineering University of Minnesota
Automated control Replaces manual control Makes adjustments 24/7 Requires Sensor User specified set point Controller & logic Actuator Set Point Controlled Input Process Disturbances Controller Actuator Process Sensor Sensor feedback
Automated control Controller adjusts actuator Keeps process or system near user specified conditions On-off control rarely at set point Continuous adjustment control closer Controlled Input Process Disturbances Set Point Controller Actuator Process Sensor Sensor feedback
Actuator output Actuator output Types of control 5 Two-position On-off Incremental Continuous adjustment 4 3 2 1 0 0 5 10 15 20 Time On-Off 5 4 3 2 1 0 0 5 10 15 20 Time Continuous Incremental
Examples Thermostat for thermal control Heaters, ventilating fans, cooling equipment & adjustable curtains Lighting controls Timer, Timer + Photo sensor & motion detector Feeders Variable frequency drives Water pumps, vacuum pumps & milk pumps
Ventilation Controls
Mechanical ventilating tools Fans lots of them Single speed Variable speed Adjustable inlets Sprinklers or misters
Can you program a ventilation controller?
What is the relation between controller set-point temperature and barn temperature? Barn temperature is generally A. Lower than set-point temperature B. Within a degree or two of set-point C. Higher than set-point temperature
Controller Settings & Terminology Set-point temperature Temperature differential Bandwidth Minimum speed
Temperature Set-point temperature Not the average space temperature Temperature at which other adjustments begin to happen Room temperature Set-point temperature Time
Temperature differential Temperature difference between when a stage or device is turned-on and it is turned-off Reduces cycling Heater example On Heater on Differential Off Cold Heater off Warm Set point Set point + Differential Temperature
Heater on-off control On Heater on Differential Heater On at cold temperatures Off at warm temperatures Off Cold Heater off Warm Set point Set point + Differential Temperature Heater Turns off at set-point plus differential Turns on at set-point
Temperature Temperature differential Room temperature fluctuates above set point and within to slightly above differential Heater Room temperature Overshoot Setpoint Differential Heater on Time Heater off
Ventilating fan on-off control On Differential Fan on Ventilating fans Fewer at cold temperatures More at warm temperatures Off Cold Fan off Warm Set point Set point + Differential Temperature Ventilating fans Turns off at set-point Turns on at set-point plus differential
Ventilating Rate Three stage single speed fan control Third stage Second stage First stage Continuous Differential Barn temperature increases as more stages turn on Cold Warm Set point Barn Temperature
Airflow rate Variable speed fan settings Bandwidth Temperature deviation over which a variable speed fan goes from minimum to full capacity Minimum speed Controller speed setting at minimum airflow rate desired Maximum Minimum Temperature Bandwidth temperature
Ventilating Rate One variable & two single speed fans Third stage Second stage First stage Minimum Differential Barn temperature increases as more stages turn on Cold Bandwidth Set point Barn Temperature Warm
Multi-stage controllers One or more sensor inputs Temperature Relative humidity Other (static pressure, gas concentration) Variable speed fan outputs Multiple stages & outputs Single speed fans Heaters Other (ex. curtains & inlets)
Ventilation Controller Education Demonstration Trailer Designed by four state Extension Engineers Multiple fans, inlets and control options
Sensor location, maintenance Key controller input Represents animal space Away from fresh air inlets, drafts, heaters or direct sunlight Check calibration periodically Ceiling Ceiling inlet Fluorescent lamp Thermostat sensor
Swine barn ventilation
Dairy ventilation Tunnel ventilated Cross ventilated
Ventilating fans Sizes from 9 to 72 inch diameter Airflow rates vary by Static pressure Diameter Fan RPM Construction Guards, louvers Cone
Ventilating fans Use rated fans (BESS Lab) http://bess.illinois.edu/ Use energy efficient fans (CFM/Watt) 12 CFM/W for fans 24 inch diameter @ 0.10 inch static pressure 17 CFM/W for fans 36 to 48 inch diameter@ 0.10 inch static pressure Compare at same static pressure
Static Pressure Pressure exerted by a still liquid or gas Pressure perpendicular to the flow in a duct or tube Measured with manometer Examples Between inside and outside barn Different points in barn Before and after fan
Airflow (CFM) Fan Airflow vs. Static Pressure 4000 3500 3000 2500 2000 1500 1000 500 0 0.00 0.05 0.10 0.15 0.20 0.25 0.30 Static Pressure (inches of water)
Airflow vs. static pressure Select fan based on measured airflow at appropriate static pressure Typically Animal barns at 0.05 inch H 2 O vacuum Filtered barns at 0.20 inch H 2 O vacuum Eave inlet Ceiling inlet Exhaust fan
24 inch diameter fans with varied airflow (cfm ratings) Airflow Efficiency cfm @ 0.10 In. H 2 O cfm/w Fan 1 7,270 12.4 Fan 2 7,000 16.6 Fan 3 6,060 16.1 Fan 4 4,150 11.1 All fans were equipped with discharge cones
Fan Attachments Matter Comparison of 24 inch diameter fans Airflow (cfm) 8,000 7,000 6,000 Shutter & guard only + Wind hood + Discharge cone 5,000 Wind hoods 4,000 0.00 0.10 0.20 0.30 Static pressure (in. of water) Source: BESS Lab data Discharge cones
What restricts airflow? Restricted or small openings Direction changes Opening size and air velocity changes Entrances & Exits Wind
Practical flow restrictions Dirty and corroded shutters Plugged eave inlets & screens Filters Eave inlet
Pit Fans Restricted connections Multiple direction changes Small openings into pit Full manure pits Foaming manure pits Commonly only 50% rated flow
Filtered Sow Barns Adds to ventilation static pressure Pre-filter MERV-8 Main filter MERV-14 to -16 V-style MERV = Minimum Efficiency Reporting Value http://www.camfil.us/global/resize/79000_220_180_proportional.pngh ttp://www.camfil.us/global/resize/33260_210_220_proportional.png
Ventilation recommendations Use third party rated fans Select energy efficient fans Beware of fan interactions Avoid on/off timers for ventilation Backup controls parallel thermostats Fan maintenance Belts Louvers
Mixing (circulating) fan criteria (BESS Lab) 5 diameter centerline velocity (fpm) Thrust (lb f ) Efficiency ratio (lb f /kw) Operating cost: Fan kw x Operating hours x Electrical rate ($/kwh)
Clearance height Mixing Fan Location 10 feet x fan diameter in feet
Fan maintenance Tighten belts Lubricate shutters Poorly maintained fans have flows 40% to 60% of rated flow rates Example: 50 fans with 1 hp motors 90% efficient vs. 60% efficient 42 kwh vs. 63 kwh $3,000 vs. $4,500 per month for 50 fans
Sizing Heating Systems Correct system size is critical for Efficiency Comfort, and Lowest maintenance and operating costs over the system s life Balance building heat loss rate (BTU per hour) with heating system capacity
Avoid over sized heaters Oversized heaters lead to large temperature swings Correct size improves Energy efficiency & economics More uniform thermal conditions Balance building and ventilating air heat loss with heating system capacity
Actuator output Variable frequency drive (VFD) Avoids on-off control Provide continuous adjustment Can save energy Examples Vacuum pumps Milk pumps Well pumps 5 4 3 2 1 0 0 5 10 15 20 Time Continuous On-Off
Vacuum pumps Recommendations Properly sized rotary lobe (blower) pump VFD adjusts motor speed to match vacuum level needed Can reduce energy usage 40 to 70% http://www.delaval-us.com/-/product-information1/milking/products/?at=cow&p=3 http://www.delaval.com/en/-/product-information1/milking/products/transport/vacuum-pump/dvp-f/?sp=585&p=5 http://www.delaval.com/en/-/product-information1/milking/products/transport/vacuum-pump/lvp/?sp=585&p=5
Variable speed milk pump Pumps milk from receiver jar to bulk tank Used with well water plate cooler (heat exchanger) Match water and milk flows for efficient cooling (from 1:1 to 3:1) Reduces other cooling costs http://www.dairymaster.com/milking-parlors/advanced-technologies/ http://www.delaval.com/en/-/product-information1/milk-cooling--storage/products/?psg=463
Well pumps Two farms with two 20-hp well pumps Single speed vs. VFD Monitored pumps turning on-off and energy use over 3 days Estimated energy savings per year: 16,089 kwh and $2,333 ($0.06/kWh) Times pumps turned on in 24 hours Pump 1 Pump 2 Standard well pumps 170 169 VFD well pumps 8 31 Brinker, J., B. Reinholtz and C. Beedle. 2012. Comparison of water and energy management strategies on two Wisconsin dairy farms. Paper No. 12-13337412. ASABE, St. Joseph, MI.
Lighting Energy efficient lighting Light emitting diodes (LED) Fluorescent High intensity discharge Adjustable lighting output (dimmers) Timers Photo sensors Motion detectors
Lights Timer Photocell Lighting control Photo sensor + Timer Dark Light On Off On Off 0:00 6:00 12:00 18:00 0:00 Lights Timer Photocell
Automated controllers Useful tools to manage systems Many types and options To better manage systems need to learn Controller terminology How to program controllers Assess system performance Controllers are part of management
Thank You For Your Attention Kevin A. Janni Professor & Extension Engineer kjanni@umn.edu
Acknowledgements The following individuals are acknowledged for resources they provided for this presentation Larry Jacobson Steve Pohl Mike Brumm Jennifer Brinker Adam Laurent