Motors

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Introduction

Electric motor-driven systems make up by far the largest single category of electricity end use in the American economy. Based on a detailed analysis of motor systems inventory, the U.S. Department of Energy Office of Industrial Technologies (DOE OIT) estimates that industrial motor energy use could be reduced by 11% to 18% in the manufacturing sector alone if facilities managers undertook all proven, cost-effective efficiency technologies and practices. That is, implementation of all well-established motor system energy efficiency measures and practices that meet reasonable investment criteria could yield annual energy savings of up to $5.8 billion at average industrial energy prices. Potential motor efficiency savings in non-manufacturing industries are estimated at an additional 14 billion kilowatt hours (kWh). This is roughly equivalent to potential energy savings in such major commercial end-uses as indoor lighting.

Technology Options

There are two basic categories of motor system energy efficiency measures:

  • Motor efficiency upgrades that improve the energy efficiency of the motor driving a particular machine or group of machines.
  • System efficiency measures that improve the efficiency of a machine or group of machines as a whole. System efficiency can be improved by reducing the overall load on the motor through engineering strategies such as: improved process or system design, better match between component size and load requirements, use of speed control instead of throttling or bypass mechanisms and better maintenance.

The Flex Your Power Tips page provides examples of each of these elements along with the range of savings associated with each kind of efficiency measure. Here are some examples of both motor upgrades and system measures:

Motor Efficiency Upgrades

  • Replace motor currently in use with higher-efficiency motor. Essentially, there are two major types of energy-efficient motor standards today: the federal Energy Policy Act of 1992 (mandatory); and the Consortium for Energy Efficiency Premium Efficiency Motors Initiative (voluntary — on average, CEE's motor efficiency specifications are 1% to 2% higher than the federal requirements). Both standards are based on National Electrical Manufacturers Association motor specifications.
  • Improve rewinding practices. Follow rewinding protocols adopted by the Electrical Apparatus Service Association 'Electrical Apparatus Service Association (EASA).' Avoid rewind practices known to contribute to efficiency degradation such as the use of high temperatures to soften wire.

System Efficiency Measures

  • Reduce load requirements. This category encompasses a wide range of strategies such as widening pipe diameters to reduce resistance, straightening ducts, leveling process flows over time to reduce peak loads, and eliminating unnecessary by-passes. These strategies reduce and/or level loads on motors, which open up opportunities for use of smaller or fewer motors in the system. Case studies of these kinds of projects report reductions of 5% to 60% of system energy use.
  • Reduce or control speed. Reduction of speed to match load or use of adjustable speed drives (ASD) to match speed to fluctuating loads can save a great deal of system energy due to the exponential relationship between shaft speed and energy. Case studies of ASD installations or mechanical speed reductions to replace throttling controls have found system savings in the range of 30% to 80%.
  • Match size to load. Motor systems are often sized to accommodate expected peak load, with little or no allowance for the operation of the process at partial load. Serving partial loads while saving energy includes staging of equipment, automatic shutdown, parallel systems and downsizing. Estimated savings from these kinds of projects range from 5% to 30%.
  • Upgrade component efficiency. Relatively small savings are available by upgrading the inherent efficiency of components such as pumps, compressors and auxiliaries. Analysts suggest that available savings range from 2% to 10% of system energy use.
  • Conduct regular maintenance. Conscientious maintenance can yield significant system savings from to plugging leaks and maintaining system balances. Savings from these measures can range from 2% to 30% of total system energy use.

Efficiency Benefits

Motor system energy use and potential savings vary greatly among industries. For industries that use significant amounts of motor system energy, the financial impact of motor system energy costs and potential savings are substantial. For industries with tight operating margins, relatively small increases in operating margin can have a significant impact on profitability.

Table: Financial Impact of Motor Energy Consumption and Savings in Selected Industries
  Motor Energy
Industry Motor System Costs/Estab. Costs/Total Operating Costs Savings per Estab/Yr. Savings as % of Operating Margin
Paper Mills $4.6 M 6.5% $659,000 5.0%
Petroleum Refining $5.6 M 1.4% $946,000 1.0%
Industrial Inorganic Chemicals $1.6 M 10.4% $283,000 6.0%
Paperboard Mills $3.0 M 6.4% $492,000 5.0%
Blast Furnaces and Steel Mills $6.0 M 2.1% $358,000 2.0%
Industrial Organic Chemicals $1.3 M 1.0% $91,000 1.0%
Industrial Gases $1.1 M 21.7% $116,000 13.0%
Plastics Materials and Resins $1.5 M 1.5% $121,000 1.0%
Cement, Hydraulic $2.2 M 9.6% $219,000 4.0%
Pulp Mills $1.7 M 6.7% $483,000 5.0%
Source: U.S. Industrial Electric Motor Systems Market Opportunities Assessment December 2002



Table: Potential Systems-Level Motor Energy Savings by Select Manufacturing Applications
  Estimated Savings (GWh/Year)
Industry Fan System Pump System Compressed Air Systems Other Proc. Systems Motor Upgrade Motor Downsizing Replace vs. Rewind All Systems Total Energy
Food 157 1,250 494 517 1,376 585 295 4,674 12.40%
Textile Mill 170 593 408 166 743 305 121 2,506 15.00%
Apparel 1 0 68 15 47 22 8 162 13.90%
Lumber/Wood 153 243 324 341 432 336 184 2,013 8.80%
Furniture 87 5 78 33 173 68 26 471 12.70%
Paper 1,082 6,293 773 881 3,197 845 870 13,942 14.00%
Printing 52 17 74 90 305 153 39 731 12.30%
Chemicals 942 7,556 6,813 994 4,219 1,409 1,255 23,188 16.10%
Petroleum/Coal 271 6,159 1,352 169 1,736 459 453 10,599 20.40%
Rubber/Plastics 113 1,851 813 411 1,498 435 303 5,424 14.80%
Leather 27 0 0 0 22 6 3 58 11.80%
Stone/Clay/Glass 31 18 96 20 117 45 14 343 15.40%
Primary Metal 738 1,537 2,150 1,085 3,199 983 749 10,441 11.90%
Fabricated Metal 34 181 303 80 298 195 46 1,137 15.60%
Industrial Machinery 28 195 200 94 368 208 44 1,138 15.40%
Electronics 18 1,554 513 43 609 222 93 3,053 23.10%

Source: U.S. Industrial Electric Motor Systems Market Opportunities Assessment December 2002

Many kinds of motor system efficiency improvements yield benefits in addition to energy cost reductions. These include improved control over production processes, reduction in waste materials and improved environmental compliance.

Manufacturers

Motors & Motor Manufacturers is a database of 341 motor manufacturers at Thomas Register, a comprehensive online resource for finding companies and products manufactured in North America.

Industrial Quick Search, Inc. offers an electric motors manufacturers directory including DC motors, stepper motors, servo motors, AC motors, gear motors, DC electric motors, stepping motors, synchronous motors, permanent magnet motors, brushless motors and electric motor manufacturers.

Purchasing Tips

As of October 1997, all integral horsepower, polyphase, general purpose, low voltage AC induction motors from 1 to 200 horsepower sold in the U.S. must meet minimum efficiency standards. These standards, promulgated by the EPAct, are based on the NEMA MG 1. The minimum efficiency standard increases with horsepower category. The minimum EPAct standards leave room for improvement in motor efficiency and offer the opportunity for energy savings. Premium efficiency motors currently on the market are more efficient than the minimum standard, particularly in the lower horsepower ranges, and NEMA MG 1 has been updated to reflect new Premium standards.

For many companies, it makes sense to establish a motor purchasing policy because it indicates management approval and simplifies the paperwork needed to purchase a new premium-efficient motor. While some original equipment manufacturers supply premium motors as an option, they generally offer a lower-efficiency motor unless your motor management plan specifies the premium model.

There are many tools to help you purchase efficient motors. These include campaigns such as Motor Decisions Matter Campaign and the U.S. DOE OIT's Best Practices Motor Program, as well as software and publications, including:

Emerging Technology

Experts predict a wide range of trends for motor system components, including:

  • Variable speed drives will become small enough to be packaged directly on the motor and sold as a unitary variable speed motor.
  • Drive dependability will increase so significantly that this component will last the life of the motor.

More forward-looking information on motor and drive technology is available at NineSigma, where visitors can do keyword searches in the Patents section to find out about newly issued motor and drive patents. The U.S. Patent Office continues to award patents covering motors and/or drives linked to HVAC and industrial processing applications.