1. Energy Efficient Motor Drive Systems

2. Motor Electricity Use Motors consume about 75% of all the electricity used by industry. Their popularity is a testament to their reliability, versatility and efficiency. Despite these attributes, the cost of powering motor driven systems in the US is over $90 billion per year. Thus, increasing the efficiency of motor drive systems can lead to significant savings.

3. Motors: The Nature of Wealth  James Watt observed that a horse pulling 180 pounds of force walked at 181 feet per minute.  Thus, the horse generated 33,000 ft. lbs. per minute, which Watt called one “horsepower”.  Generating 1 hp required: –1,000 lb horse –6 ft tall –costs $5,000 /yr to board  Today, generating 1-hp requires: –32 lb motor (30x less) –4 x 6 inches (12x less) –costs $250 /year (20x less)

4. Inside Out Approach to Energy Efficient Motor Drive Systems  End Use –Turn off motors when not in use –Move motor use to off-peak shift  Distribution –Motor drives  Primary Energy Conversion –Right size motors –Purchase ‘Premium Efficiency’ motors

5. Turn Off Motors When Not In Use!  Stamping press motors –80% loaded while stamping –65% loaded during idle –65% of power dissipated as heat due to friction!  Example: Turn off 50-hp stamping press for 2,000 hr/yr. –50 hp x.65 x.75 kW/hp x 2,000 hr/yr x $0.10 /kWh = $4,875 /yr

6. Turn Off Motors When Not In Use!  Hydraulic system motors –8 kW while loaded –5 kW while unloaded –Draws 63% of loaded power when unloaded.  Example: Turn off 20-hp hydraulic motor for 2,000 hr/yr. –5 kW x 2,000 hr/yr x $0.10 /kWh = $1,000 /yr

7. Move Motor Operation to Off-Peak Shift  Motor used only during first shift  Move motor use from 1 st to 2 nd shift to reduce electrical demand  Example: Move use of 50-hp, 80% loaded, 90% efficient, grinder to off-peak shift –50-hp x 0.75 kW/hp x 80% / 90% = 33 kW –33 kW x $14 /kW-mo x 12 mo/yr = $5,544 /yr

8. Inside Out Approach to Energy Efficient Motor Drive Systems  End Use –Turn off motors when not in use –Move motor use to off-peak shift  Distribution –Motor drives  Primary Energy Conversion –Right size motors –Purchase ‘Premium Efficiency’ motors

9. Replace Smooth with Notched V-belts Notched V-belts –3% more efficient than smooth belts –Last 50% to 400% longer than smooth belts –Cost only 30% more than smooth belts Example –25-hp motor, 91% efficient, 75% loaded –Savings = 25 hp x 0.75 kW/hp x 75% /.91 x (1/.92 - 1/.95 ) = 0.5 kW –Savings = 0.5 kW x 6,000 hours/yr = 3,000 kWh/year –Savings = 3,000 kWh/year x $0.10 /kWh = $300 /year  = 92%  = 95%

10. Inside Out Approach to Energy Efficient Motor Drive Systems  End Use –Turn off motors when not in use –Move motor use to off-peak shift  Distribution –Motor drives  Primary Energy Conversion –Down size under-loaded motors –Purchase ‘premium efficiency’ motors –Replace rather than repair older failed motors

11. Down-size Under-loaded Motors Efficiency declines at low loadsPower factor declines at low loads

12. Motors: Energy Cost >> Purchase Cost 20-hp, 93% eff, 75% loaded, 8,000 hrs/year, $0.10 /kWh, cost = $1,161 Annual energy cost = 20 hp x 75% x.75 kW/hp / 93% x 8,000 hr/yr x $0.10 /kWh = $9,677 /yr Over 1 yr, energy cost is 8x greater than purchase cost Over 12-yr life, energy cost is 100x greater than purchase cost!

13. Purchase Premium Efficiency Motors Consider –15 hp motor, 80% loaded, 6,000 hr/yr, $0.10 /kWh –Standard Eff = 0.91 = $889 Premium Eff = 0.93 = $1,010 Cost of electricity –Savings = 15 hp x.8 x.75 kW/hp x 6,000 hr/yr x $0.10 /kWh x (1/.91 – 1/.93) –Savings = $127 /yr Incremental Cost of Premium Efficiency Motor –$1,010 - $889 = $121 Simple Payback –$127 / $121 /yr = 1 year

14. Replace or Repair Older Failed Motor? Assuming 80% loaded, 6,000 hr/yr, $0.10 /kWh

15. Replace Rather than Rewind Motors Source: US DOE Motor Master+ 4.0

16. U.S. D.O.E. Motor Master Software  Over 25,000 motors from 18 manufacturers  Rapid data entry, sorting by condition, and rewind/replace recommendations.  Technical data to help optimize drive systems, such as: –Motor part-load efficiency, power factor –Full-load speed, locked-rotor, breakdown, and full-load torque.  Motor purchasing information, including list prices, warranty periods, etc.  Capability to calculate savings, payback, return-on-investment, etc.  http://www1.eere.energy.gov/industry/bestpractices/software.html#mm

17. Employ Energy Efficient Flow Control

18. Inefficient Flow Control By-pass loop (No savings) By-pass damper (No savings) Throttling valve (Small savings) Inlet vanes (Moderate savings)

19. Efficient Flow Control Trim impellor for constant-flow pumps Slow fan for constant-flow fans VFD for variable-flow pumps or fans

20. Power and Flow Control

21. Case study: Large Cooling Towers

22. Large Cooling Loop Pumps

23. Worlds Largest Bypass Pipe

24. For Constant Flow Pumping: Trim Pump Impellor and Open Throttling Valve

25. For Constant Flow Fan: Slow Fan Speed by Increasing Pulley Diameter

26. For Variable Flow: Install VFD & Control with Difference Pressure W 2 = W 1 (V 2 /V 1 ) 3 Reducing flow by 50% reduces pumping costs by 87%