Control Strategies and Considerations for Livestock and Other Farm Buildings

Transcription

1 Control Strategies and Considerations for Livestock and Other Farm Buildings Kevin A Janni Bioproducts & Biosystems Engineering University of Minnesota

2 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

3 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

4 Actuator output Actuator output Types of control 5 Two-position On-off Incremental Continuous adjustment Time On-Off Time Continuous Incremental

5 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

6 Ventilation Controls

7 Mechanical ventilating tools Fans lots of them Single speed Variable speed Adjustable inlets Sprinklers or misters

8 Can you program a ventilation controller?

9 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

10 Controller Settings & Terminology Set-point temperature Temperature differential Bandwidth Minimum speed

11 Temperature Set-point temperature Not the average space temperature Temperature at which other adjustments begin to happen Room temperature Set-point temperature Time

12 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

13 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

14 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

15 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

16 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

17 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

18 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

19 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)

20 Ventilation Controller Education Demonstration Trailer Designed by four state Extension Engineers Multiple fans, inlets and control options

21 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

22 Swine barn ventilation

23 Dairy ventilation Tunnel ventilated Cross ventilated

24 Ventilating fans Sizes from 9 to 72 inch diameter Airflow rates vary by Static pressure Diameter Fan RPM Construction Guards, louvers Cone

25 Ventilating fans Use rated fans (BESS Lab) Use energy efficient fans (CFM/Watt) 12 CFM/W for fans 24 inch 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

26 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

27 Airflow (CFM) Fan Airflow vs. Static Pressure Static Pressure (inches of water)

28 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

29 24 inch diameter fans with varied airflow (cfm ratings) Airflow Efficiency 0.10 In. H 2 O cfm/w Fan 1 7, Fan 2 7, Fan 3 6, Fan 4 4, All fans were equipped with discharge cones

30 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, Static pressure (in. of water) Source: BESS Lab data Discharge cones

31 What restricts airflow? Restricted or small openings Direction changes Opening size and air velocity changes Entrances & Exits Wind

32 Practical flow restrictions Dirty and corroded shutters Plugged eave inlets & screens Filters Eave inlet

33 Pit Fans Restricted connections Multiple direction changes Small openings into pit Full manure pits Foaming manure pits Commonly only 50% rated flow

34 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 ttp://

35 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

36 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)

37 Clearance height Mixing Fan Location 10 feet x fan diameter in feet

38 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

39 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

40 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

41 Actuator output Variable frequency drive (VFD) Avoids on-off control Provide continuous adjustment Can save energy Examples Vacuum pumps Milk pumps Well pumps Time Continuous On-Off

42 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%

43 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

44 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 VFD well pumps 8 31 Brinker, J., B. Reinholtz and C. Beedle Comparison of water and energy management strategies on two Wisconsin dairy farms. Paper No ASABE, St. Joseph, MI.

45 Lighting Energy efficient lighting Light emitting diodes (LED) Fluorescent High intensity discharge Adjustable lighting output (dimmers) Timers Photo sensors Motion detectors

46 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

47 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

48 Thank You For Your Attention Kevin A. Janni Professor & Extension Engineer

49 Acknowledgements The following individuals are acknowledged for resources they provided for this presentation Larry Jacobson Steve Pohl Mike Brumm Jennifer Brinker Adam Laurent