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Pro green 2012 vfd fans


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Presentation given during ProGreen EXPO in Denver Colorado 10 February 2012

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Pro green 2012 vfd fans

  1. 1. BEST INDUSTRY PRACTICE: REDUCE YOUR POWER LOAD Matthew Schreiner and Steve Newman
  2. 2. Reducing Your Electric Power Consumption Using Variable-Frequency Drive Controllers on Your Exhaust FansMatthew Schreiner M.S. Floriculture Graduate StudentSteven E Newman, Ph.D., M.S. Greenhouse Crops Extension Specialist and Professor of Floriculture ProGreen EXPO 10 February 2012 10:30 am – 11:30 am
  3. 3. Active Cooling in the greenhouse
  4. 4. Greenhouse CoolingWhy is cooling needed?• Solar radiation is the “heat input” for the earth – Radiate as much as 277 Btu/ft2/hr onto the surface of the earth on summer day – Coastal and industrial areas, may only be 200 Btu/ft2/hr• Up to 85% of this radiation may enter the greenhouse – Most of the IR heat becomes trapped inside – Greatly increases the greenhouse temperature
  5. 5. Greenhouse CoolingActive Cooling Systems• Dry bulb temperature – Actual air temperature measured with an ordinary thermometer• Wet bulb temperature – The air temperature if enough water were to be evaporated into it to saturate the air
  6. 6. Greenhouse CoolingActive Cooling Systems• Wet bulb temperature is what the air can be cooled to if the evaporative cooling system is operating at 100% efficiency• Fan and pad systems – 80% efficiency
  7. 7. Greenhouse CoolingPhysics of Evaporative Cooling• Use evaporation of water to convert sensible heat into latent heat, thus reducing the temperature of the air• About 1,060 Btu’s of heat are “absorbed” out of the air for every pound of water evaporated
  8. 8. PsychrometricChart
  9. 9. Greenhouse Cooling• Air exchange rate (cfm) required – Standard recommendation is one exchange per minute – Remove and replace entire volume of greenhouse• Modify “standard” cfm as needed – Account for density of air (elevation) • FELEV – Maximum light • FLIGHT – Maximum temperature rise • FTEMP
  10. 10. Greenhouse CoolingDesigning a Fan and Pad System• Fan selection and placement – Total fan cfm = calculated cooling requirements – Fans should be equal to cfm required – Usually placed on the wall opposite the pads – Maximum distance between fans and pads is 200 feet – Place fans close to plant height – No more than 25 feet between fans, evenly spaced
  11. 11. Greenhouse Cooling 75 F 82 F Typically temperature rises 7 F from cooling pad to exhaust fan
  12. 12. Energy Expenses Heat Refrigeration ( 1%) Ventilation (10%) Soil Pasteurization (9%)
  13. 13. What Does a VFD Do?• A VFD controls the frequency sent to the motor• Motor RMP can be varied as cooling need changes• Reduces cold/moist air rush
  14. 14. What Does a VFD Do?• Reduces cold/moist air rush• Reduces heat stress• Increase crop uniformity• Create uniform growth environment
  15. 15. Precise Control of Fan SpeedDuring summer months, thecooling requirement can changedramatically throughout the day• Short Cycling• In-Rush Current• Soft Starting• Affinity law
  16. 16. In-Rush Current• Truly a “killer” of electronics• Creates unnecessary heat• Motor consumes up 10 times its normal full amp load for 500 ms during start up
  17. 17. In-Rush Current• Short cycling• Fans run for longer so in-rush is limited• Eliminated with Soft Start• VFDs could lengthen life of equipment
  18. 18. Micro-climate Uniformity• Slowly ramp up fan speed as needed• Limits cool air rush
  19. 19. Micro-climate Uniformity• Evaporative Cooling Pad• Running fans longer help create homogeneity
  20. 20. Energy EfficiencyAffinity law• Change in power is proportional to the cube of the change in speed• A fan running at 50% RPM only uses 12.5% power!
  21. 21. Energy Efficiency• Teitel et al. (2004) proposed variable speed drives to control fans according to the heat load on the greenhouse.• They showed that it is possible to reduce electricity consumption by 36%.• In their study, the average energy consumption with a variable speed system over a period of one month was about 0.64 compared with ON/OFF. Teitel, et al. 2004. Energy Conversion and Management 45:209-223
  22. 22. Temp/Humidity• Measured Temp/Humidity for one day.• VFD greenhouse showed reduced change in both humidity and temp. Teitel, et al. 2004. Energy Conversion and Management 45:209-223
  23. 23. Temp/Humidity• Measured Temp/Humidity for one day.• VFD greenhouse showed reduced change in both humidity and temp. Teitel, et al. 2004. Energy Conversion and Management 45:209-223
  24. 24. Research OverviewIdentify benefits using VFDs• VFD greenhouse vs. Non VFD greenhouse• Envirostep• Temperature• Crop uniformity• Water use• Amp clamp
  25. 25. Envirostep• Wadsworth Envirostep greenhouse controller• Modulated voltage output• Many Possibilities for VFD setup
  26. 26. Temperature• VFDs creates a more homogeneous environment• Maintaining set points will be a challenge• Uniform air flow ramped up and slowed down as needed to eliminate cool air rushes• Place temperature sensors around the greenhouse
  27. 27. HOBO temperatureTemperature Sensors data loggers
  28. 28. Hanging Lysimeters• Water use• Weighing Lysimeter• Determine water use across greenhouse to determine how air flow rates impact plant growth
  29. 29. Hanging Lysimiters
  30. 30. Energy measurementsAmp Clamp• Measures amperage every 30s• Connects directly around power wire• Very accurate• Simultaneous amp data between VFD and On/Off
  31. 31. Amp Clamp Power Cycle Data
  32. 32. Energy EfficiencyContinuous Energy Use Monitor• 3-Phase electricity monitoring at up to 10 locations.• Simultaneous monitoring between VFD and NON VFD Greenhouse.• KWh units and cost estimate• Current usage and accumulated• Web accessible
  33. 33. Fan Control Requirements• Voltage Modulated Output (0-10 VDC)• Managed as a percentage of the voltage output similar to a mixing or steam valve• Integrates easily into step controllers ramping up fan speeds based on temperature demand
  34. 34. Contact Information• Review and share this presentation:• Website:• eMail: