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The Measure of Power

Non-intrusive load monitoring gives detailed views of where power is going, with payoffs for utilities, customers and maybe Big Brother.
June 28, 2001

California’s winter of rolling blackouts left its citizens outraged, its utilities in crisis and its politicians pointing fingers. Enter Steven Leeb and Les Norford, two MIT professors with a plan to help electricity suppliers and consumers figure out where power is going and how to conserve it.

Leeb, a professor of electrical engineering, and Norford, a professor of architecture, are working together to test a system called non-intrusive load monitoring, or NILM (rhymes with “film”), which uses a wallet-sized blue box, a PC and some very advanced software to measure fluctuations in voltage and current hundreds of times each second.

Using complex algorithms, the system’s software analyzes these minute fluctuations to identify a building’s electrical “load”-the individual machines drawing power off the line, be they light bulbs, air conditioners or a washing machine. The system is “non-intrusive,” explains Leeb, because it attaches to the outside of a power cable running into a building.

Truly Smart Sensing

While “smart meters”-devices that gather detailed data about electricity in a home or business-have been around for years, researchers call NILM a major leap over existing technology.

Most smart meters in use today must be connected to the power line, which makes installation expensive. And such systems take only a few measurements per minute-or per hour. By taking hundreds of samples each second, the new monitoring technique can present a far more detailed, high-resolution picture of electricity use.

“It’s like a microscope,” says Mary Ann Piette, a staff scientist at Lawrence Berkeley National Lab in Berkeley, CA, where researchers are testing the system. “You’re looking at very minute info from the signal data.”

A NILM prototype currently monitors washing machines in an MIT dorm, displaying the results on the Internet. “See that?” exclaimed Leeb during a recent demonstration. “Someone just turned on a drier!”

Leeb even claims to be able to tell when someone is washing sneakers-maybe-because uneven loads put a different strain on a washer’s motor. Another finding: most MIT students do their laundry between 11 p.m. and 4 a.m.

Conserve Your Energy

This spring, Leeb and Norford set up experimental monitors in several California buildings.

Working with researchers at Lawrence Berkeley National Lab, the two hope to demonstrate that non-intrusive load monitoring can pay off in two ways. First, the data collected could help building operators use power more efficiently. Second, the sensitive monitor could identify equipment problems early-before systems break down.

The system can improve power conservation by helping buildings optimize their power consumption. On average, office buildings could save 20 to 25 percent of their energy costs, says Jeff Haberl at Texas A&M’s Energy Systems Laboratory.

Haberl advises building operators on energy efficiency. With NILM, he says, “you can collect this information, run an analysis, and tell people, ‘Your cooling system’s running higher than it should. Your lights should be off at night.’”

Another application is finding faulty equipment. For example, says Norford, sticky valves in a building’s cooling system are ordinarily very hard to detect. With a smart monitoring box, the building operator could see that nearby fans are drawing more power than normal, a sign that they are pushing against a closed valve.

As more buildings adopt alternative sources of power, such as batteries, microturbines and fuel cells (see “Power to the People”), NILM will play a third role, says Steve Shaw, a professor of electrical engineering at Montana State University. Many devices, including motors, laser printers and incandescent bulbs, draw a large amount of power when they turn on, but less once they are running, explains Shaw. The initial spike may trigger a building’s backup generators, when battery power would have sufficed.

But if the spike can be recognized for what it is, a great deal of power and money could be saved, says Shaw. “We can avoid having situations where generator sets turn on for 10 seconds or operate in inefficient or polluting ways,” he says.

Electric Eyes

In essence, non-intrusive load monitoring is an information technology. And like any such technology, it could gather information that customers would prefer to keep to themselves.

Privacy advocates worry that utility companies could turn over to others the information they collect. Some utilities already notify the police when residential customers draw unusually high amounts of electricity-a tip-off that they could be, for example, growing marijuana.

A utility that uses customer information to improve service-such as a phone company listening in on a call to monitor quality-doesn’t worry Marc Rotenberg, director of the Electronic Privacy Information Center. What does concern him, he says, is when the utility shares that information with a third party, like the government or another business.

But power surveillance could be put to good use, says Shaw, pointing to the problem of arms control monitoring. “If some fellow has an underground bunker, you have no idea what’s going on in there,” he says. “If you want to make sure it’s not a machine shop for making missile parts, you might be able to determine what’s happening inside” by using this type of tool.

The bottom line, says Rotenberg, is who controls the data. “You may not have a lot of privacy concerns about whether you’re using a toaster or a toaster oven,” he says, “but you should be able to decide whether or not you reveal that information.”

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