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By Mike Pehanich, Plant Operations Editor | 01/09/2007
Simply replacing drafty old doors with modern, energy-efficient ones can be a big energy saver, as discovered by Truitt Bros.
Processors can justify equipment purchases and energy management programs only when they have adequate data. Good data facilitates negotiation for better energy rates. Knowing energy requirements at every significant point in the plant makes it easier to identify problems with power systems and to lower power demand charges. It can also reduce downtime and help avoid blackouts.
Motors are always candidates for efficiency upgrades. Rockwell Automation published a study in 2002 showing the food industry was able to effect total energy cost savings of 12.4 percent in applications with high motor system content by implementing efficiency measures.
Baldor Electric (www.baldor.com), Fort Smith, Ark., the world’s largest manufacturer of motors, often quotes a U.S. Dept. of Energy report that claims “electric motor-driven systems used in industrial processes consume some 679 billion kWh, or 63 percent of all electricity used in U.S. industry.” It’s easy to see how even a small efficiency increase in a motor, multiplied by the millions of motors out there, can add up to huge reductions in electricity use.
In 1992, the Energy Policy Act established minimum efficiency standards for industrial electric motors made after October 1997. But Baldor estimates only 10 percent of all motors in use today comply with those minimum efficiency levels.
The greatest gains in energy savings come when processors can integrate improvements from as many of the components of energy consumption as possible. In addition to motors, these include motor controls, power distribution, transmissions and plant floor equipment and processes.
Energy audits, of course, always precede such efforts. Plant drawings and utility bills come into play. Measurements of energy consumption at key points of the operation are critical. Motors driving processing and packaging equipment should be monitored often.
Strategies for improvement include load profiling, measuring electrical consumption over time; demand management to control electrical loads and to avoid demand penalties; and co-generation and the addition of backup energy measures.
In the late 1990s, Kraft Foods engineers lamented that the difficulty of demonstrating return on investment for capital expenditures indefinitely delayed needed boiler upgrades. They were not alone. Much of the food industry was guilty of the same penny-wise, pound-foolishness, for which processors paid dearly as energy prices skyrocketed.
“When processors should have made investments in the 1990s, capital dollars didn’t go into energy systems,” says Schneider Electric’s Worlick. “A lot of systems are 15 to 30 years old. We see more attention to them today. Companies are looking at ways to make older systems more efficient, but energy efficiency measures are still fighting hard for attention today.”
Companies that avoided upgrades to steam generators and heat recovery systems in the past might want to reconsider. A lot of companies passed up steam trap systems to capture waste heat, steam vent losses and boiler stack losses a few years back. Worlick says they may want to take a second look today.
“The economics that come into play are different today,” he says, identifying ionic stack economizers and other pieces of heat recovery equipment surrounding boilers as savings-makers. “If you have a place to put steam back into the process, you are now seeing one- to two-year payback."
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