Improving Motor Efficiency
By James Piper, P.E. February 2012 - Energy Efficiency
Motors and the loads they drive represent some of the largest users of electricity in commercial and institutional facilities. Because motors are such high users of energy, they present a tremendous opportunity for maintenance and engineering managers to reduce energy use and cost through improved motor efficiency.
One such opportunity occurs when managers must make a decision on whether to repair or replace an aging motor. If the determination is to replace the unit, managers have several options that can have a tremendous impact on system operation and overall energy efficiency.
Efficiency On The Rise
Much has happened recently that gives managers tools to improve motor efficiency. The federal government has developed energy standards that manufacturers must meet for the types of motors commonly found in a facility's energy-using systems. Replacing standard-efficiency motors with high-efficiency motors will reduce the energy requirements for that motor by about 2-8 percent. While that might not seem like a major improvement, depending on the horsepower of the motor and the number of hours it operates annually, the energy savings can be significant.
The development of high-efficiency motors was only the first step. Today, premium-efficiency motors meet even higher energy-efficiency standards and can produce even greater savings. A side benefit for both energy-efficient and premium-efficiency motors is that to meet the energy standards, they require higher-quality components and more exacting manufacturing processes, resulting in a higher quality motor.
Manufacturers have developed reliable electronic controls that can reduce the operating speed of electric motors to match the load requirements for use in applications ranging from small pumps to large centrifugal chillers.
All of these energy-efficiency improvements come at a cost, however. The typical high-efficiency motor typically costs 10-15 percent more than the standard-efficiency motor it replaces. Premium-efficiency motors cost even more.
To help offset this increased cost and provide managers with the incentive to upgrade to more efficient motors, some utilities offer rebates and other incentives that can be as high as $50 per horsepower (hp). Programs are flexible, and many utilities offer technical assistance. Managers can contact their local utility to see if a particular application qualifies for a rebate, as well as procedures to followed to qualify.