November 15, 2007

Focus on O&M (November 2007)

ENERGY EFFICIENCY

How data logging can cut power bills

One of the greatest challenges facing building owners and facilities professionals today is finding ways to reduce energy costs. The challenge can be even greater in factories full of electricity-hungry production equipment.

Air compressors, for example, are often a factory’s largest energy consumers. According to the U.S. Department of Energy, the majority of compressed-air systems at small and midsize industrial facilities have energy-efficiency opportunities.

Concerned about its factory’s high and rising electric bill, a New York-based metal products manufacturer recently hired Power Concepts LLC (www.powerconceptsllc.com), a Manhattan-based consulting engineer, to conduct an energy audit at its plant. Specifically, the company wanted to monitor the run times of a number of air compressors in the factory to better understand their consumption patterns and pinpoint where energy-saving opportunities existed.

First, do an audit

Betsy Jenkins, director of Power Concepts’ energy field team, led the audit. She explains, “our client believed that air compressors were consuming most of the factory’s energy. They wanted us to confirm that by calculating precisely how long several operated over a typical period. With that information in hand, we would then be able to recommend steps the client could take to cut the factory’s power consumption.”

To monitor the compressors’ run times, Jenkins chose HOBO State (on/off) data loggers from Onset Computer Corp. (www.onsetcomp.com). She did so as a result of her experience, as well as the units’ excellent reputation. “In our line of work, we have to make sure that our recommendations are based on accurate data,” Jenkins says. “That’s where HOBOs really shine, and it doesn’t hurt that they’re very reliable and inexpensive, too.”

HOBO State loggers (Figure 6) are compact, battery-powered devices used to track changes in the operating status of a piece of equipment. In practice, a unit does just one job: recording every time that, say, a motor or compressor turns on or off, as well as the direction of the transition. For this customer, Jenkins’ team attached one HOBO to each of the factory’s three main compressors and then let it monitor changes in status over a two-week period (Figure 7).

6. On the job. A Hobo State unit monitoring transitions of an air-operated valve. Courtesy: Power Concepts LLC

7. Big iron, small plastic. Another kind of Hobo, riding the rails of a compressor motor. Courtesy: Power Concepts LLC
 

After two weeks’ worth of data had been recorded, the information was uploaded to a PC and analyzed using Onset’s HOBOware Pro graphing and analysis software. The analysis indicated that compressor run times were unusually high, verifying the customer’s gut feeling.

Then, apply the results

Jenkins and her team then performed a second, more in-depth evaluation of the factory while it was shut down, during lunch hour. They detected several places where compressed air was leaking out of fittings. In one case, they noted a compressed air nozzle whose actuating handle had been taped open to disperse fumes.

“Because we conducted our site survey when the building was quiet, we were able to hear hissing sounds that no one had noticed before,” Jenkins explains. “We also discovered that one operator was using a compressor nozzle as a fan to blow fumes away from his welding machine. He had no idea that doing so was costing the company a ton of money. He could have had the fumes dispersed much more cheaply by asking his boss to have a small fan mounted near the machine.”

According to Jenkins, the data loggers also were instrumental in helping her client understand that a large portion of the factory’s power consumption was attributable to several leaks in air compressors. “Before conducting the audit, our client didn’t realize how often the compressors were running. Now he does, and we expect that our recommended energy conservation measures—plugging those leaks, for example—will save him a tidy sum,” concludes Jenkins.

—Contributed by Onset Computer Corp. (www.onsetcomp.com).