Industry’s perspective has come a long way from the ’50s and ’60s when it seemed we’d have an endless supply of cheap energy. Back then, Reddy Kilowatt promised nuclear power so inexpensive they wouldn’t have to meter it, throwing half the energy of combustion out the smokestack was good enough, and Jed Clampett could strike oil just “shooting for some food.”
The rapid rise of energy costs during the past few years, buttressed by concerns about energy security and climate change, support the widespread conclusion that we’re entering an era in which energy productivity (energy cost per unit of production delivered to the customer) will loom ever larger as a factor in the bottom line and global competition.
As Contributing Editor Peter Garforth has explained in detail starting October, 2005 in our Energy Expert series (see sidebar, “More resources at www.PlantServices.com”), systematically increasing your company’s energy productivity requires a comprehensive strategy built on solid understanding of each facility’s consumption, usage, criticality to the business and vulnerability in the market.
But how big are the potential savings, how fast might they come and where are they commonly found? Of course, there’s no single answer that fits every facility, but the experts we consulted put the finger on three major villains: electrical, boiler and compressor/pump/fan systems. We’ve renamed this evil trio the Zapper, the Steamer and the Leakster, respectively and as a group, we dub them the D-Energizers.
These villains break down into a number of areas where major wasted energy dollars usually lurk. Individually, or as a team, they’re out to sabotage your plant’s energy resources. If you want to be the hero at your plant and rid your world of the D-Energizers, get your utility belt ready and follow along.
What are you paying?
The first step in any rehabilitation is acknowledging a problem. Recognize that these D-Energizers exist and lurk around every corner. While you and your purchasing department might be well aware that you need to pay more attention to energy, the folks in charge of using it often are oblivious, and most plants don’t have the detailed consumption information they need to get started. The first step to raising awareness and getting actionable data is to monitor consumption. Catching the D-Energizers in the act is the place to start.
“If a plant is monitoring energy and water usage, they’re really ahead of the game,” says Cassie Quaintance, energy market segment manager, Schneider Electric (www.us.schneider-electric.com).
“If not, they need to install instrumentation. You have to be armed with information to be given the green light on projects.”
Consumption data can support negotiations with power companies. “Attention to rates, tariffs, time-of-day and peak shaving on the supply side can provide some really quick hits with good return on investment that can finance changes on the demand side,” Quaintance says, “and the demand side requires detailed energy analysis.”
If you perceive the need for a monitoring system as a significant obstacle, think of it as a tool not only for targeting cost reduction opportunities, but for enlisting energy users in the cause, Quaintance says. “It’s difficult to put an ROI on a monitoring system, but we find that just putting one in place can make people aware and reduce consumption by 5% to 7%.”
Enter the Zapper. He’s fast and out to sap the motors at your plant by making them run at less than peak performance. Because you’re reading this, you’ve probably seen a lot about industrial motor efficiency, so I’ll be brief. Consider motor efficiency first if large motors run many hours under heavy loads (Table 1).
For average motor applications, replace single-phase motors with three-phase motors. Where a typical single-phase motor is operating at 80% efficiency, a premium single-phase is 86.5%, a typical three-phase is 87.5%, and a NEMA Premium three-phase is 90.2%. If only a single phase is available, consider using an inverter and a three-phase motor.
The U.S. DOE estimates annual savings of 62 billion kWh to 104 billion kWh (15- million metric tons to 26 million metric tons of CO2) would result from implementing motor-related best practices (see sidebar, “DOE’s hit list”). But if we only replace motors on failure, this will take 15 years to 20 years. Make life-cycle cost a factor in every motor decision and, when in doubt, spend more for the most efficient motor you can lay your hands on to keep the Zapper away.
The Zapper bolts over to this area of your plant to exhaust your equipment. Pumps, fans, compressors, many other kinds of driven equipment, motors and power transformers are designed for maximum efficiency at a specified output. Whenever that’s more than you need or you control output by throttling, you’re almost certainly wasting energy. If you never need full output, it might make sense to downsize the driver.
If the specified output is needed only part of the time and output can be varied by motor speed, a variable-speed drive (VSD) might offer rapid payback. Pumps, fans and compressors are common applications. For centrifugal pumps and fans, affinity laws show that flow is proportional to motor speed, pressure is proportional to motor speed squared and power required is proportional to motor speed cubed (Figure 1).
VSDs aren’t just for big compressor motors. Candidates include centrifugal pumps and fans used for supply and return air, chilled water, hot water from boilers to coils and cooling towers. “One of our typical plants will have, for every 100,000 sq.ft., five or six air handlers, each with a 10-hp to 15-hp supply fan and 5-hp return fan; 10 hp to 15 hp on cooling towers and a network of five to 15 pumps to and from chillers, boilers and cooling towers,” says Ivan Spronk, AC drive product line manager, Schneider Electric. The equipment is sized to keep things cool on the hottest days and warm on the coldest days, but there are only perhaps 20 extremely warm or cold days in a year. On the other 345 days, it could operate at lower capacity.