Energy Efficient Motor Drive Systems

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 1st to 2nd 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 • h = 92% • h = 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 loads Power 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

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 • W2 = W1 (V2/V1)3 • Reducing flow by 50% reduces pumping costs by 87%