Surveying the plant-scape for ripe opportunities to save energy, engineers usually find that big boilers or big process heat sources are the low-hanging fruit that will pay the big bucks. Now, at a time when many capital projects are on the back burner, those big heat and steam recovery projects may have to wait.
While a few giant assets can gobble up a large portion of a plant’s energy usage, there are dozens, maybe hundreds, of motors that can’t be bundled into a single project. But they still should be considered and even managed over time in a systematic manner with repair/replace guidelines, purchasing policies based on life-cycle costing and predictive and preventive maintenance planning.
Motors may be overlooked in capital project plans — which may well be on hold while the recession and credit crunch continue — but motors can add up to make a big dent in a plant’s overall efficiency profile.
- Electric motors account for nearly two-thirds of energy used in industrial settings, according to the Dept. of Energy (DOE).
- In keeping with the DOE estimate across industries, motor use in the food industry accounts for 60-70 percent of the typical plant’s total energy costs, according to a consensus of industry experts.
- The purchase price of a motor accounts for a fraction of its actual cost; at least 97 percent of the costs are incurred by electrical consumption over the motor’s service life.
It’s not just inevitable that food plants will gravitate toward higher-efficiency motors; soon, the law will require motor manufacturers to meet higher efficiency standards in the motors they offer.
Law to bump-up efficiency
The Energy Independence and Security Act of 2007 is a federal law that will take effect Dec. 19, 2010 to address a broad range of efficiency measures. Title III Section 313 of the act covers Electric Motor Efficiency Standards. When the law takes effect, it won’t mandate any immediate changes by end users.
The act specifies changes to most three-phase AC induction motors, 600 V or less, ranging in horsepower from 1 to 500 hp, which will fall into one of three groups when the law takes effect:
Looking to the Future
- Motors of 1-200 hp that were covered under a previous law, the 1992 Energy Policy Act (EPAct, enacted in 1997), must be manufactured to the highest level: the NEMA Premium standard of the National Electrical Manufacturers Assn. (NEMA).
- Motors 1-200 hp that were not covered by EPAct must be manufactured to the Energy Efficient designation that covered general purpose motors under EPAct.
- Motors 201-500 hp also must be manufactured to the above Energy Efficient standard.
In short, the act will bump-up the efficiency of motors by law instead of by choice. Some of the things the law will not affect include fractional-horsepower motors, two-phase motors (more common in small machinery) and DC motors, which generally have been eclipsed in plants by lower-maintenance AC motors mated to variable speed drives.
That leaves plenty of room to mandate better AC motors in production; heating, ventilation and air conditioning systems; and elsewhere around the facility — all of which eventually will get more efficient replacements.
“The law doesn’t force anyone to replace their motors. They can maintain their existing motors as long as they like,” says William Hoyt, industry director for NEMA. “But one thing they cannot do is repair a low-efficiency motor to make it a high-efficiency motor.”
So at some point, perhaps long after the supply chain is depleted of older-generation motors, the only available replacement motors will have been manufactured to higher standards.
Leading and green-leaning companies already opt for NEMA Premium-rated motors (http://www.nema.org/gov/energy/efficiency/premium), which bowed in 2003 to raise the bar on motor efficiency. Among their operational benefits, they meet tighter manufacturing tolerances for greater reliability and run cooler for greater overall energy efficiency.
Not surprisingly, progress has its price. When plants decide a motor can’t be rewound or refurbished, “They’ll be buying better products at a higher price,” says Robert Kindred, technical services manager at Toshiba International’s Industrial Division (www.toshiba.com/ind), Houston. Which is what happened 12 years ago when EPAct became law.