Scavenging Energy for Wireless Sensor Networks

Researchers are developing ways to better tap energy sources found in industrial environments as a way to boost the batteries that power wireless sensor devices.

Mark Pacelle, Vice President of Marketing, Millennial Net
Mark Pacelle, Vice President of Marketing, Millennial Net

Wireless sensor networks hold significant potential in the industrial environment. But before wireless industrial sensors can be deployed in large numbers, some see a need for improved methods for powering these devices.

“We feel that wireless technology is going to revolutionize the whole industrial instrumentation world,” says Dave Lafferty, a researcher at the Warrenville, Ill., North American headquarters of BP, the London-based global energy company. But the idea of periodically replacing batteries in thousands of wireless devices throughout an industrial complex is not attractive, he points out. “So the whole power thing [related to wireless sensor networks] will probably be the next major hurdle to get over.”

Lafferty made his remarks during a conference session on emerging technologies at the ARC Forum, Feb. 1-3, in Orlando, Fla., sponsored by ARC Advisory Group Inc., of Dedham, Mass. And in fact, work on overcoming that hurdle is already well under way. Some speakers at the session pointed to research and development activity that is showing great promise for “scavenging” energy sources from the environment as a way to keep wireless sensor networks running.

Shade power

One was Bob Karschnia, director of technology at Rosemount Inc., a Chanhassen, Minn.-based division of Emerson Process Management, which is developing wireless network technology for use in the process industries. “Solar energy holds the highest energy density right now per cubic centimeter of any energy scavenging technology,” said Karschnia. And during a question and answer session, Karschnia told the audience about solar technology that Emerson is developing that can operate in shade, such as that found where devices are shaded by equipment or are located on the north side of a building.

“Solar power is typically designed to work in very intense sunlight conditions. But we designed our recharge circuitries to actually optimize themselves based on the power you could see in the shade,” Karschnia said. “And we can operate for significant periods of time, and with very high update rates, by using this technology.”

Complementing the Emerson effort is work done by Millennial Net, a Burlington, Mass., wireless networking company, to develop an energy saving “sleep mode” for its wireless mesh network technology. Millennial Net has partnered with Emerson in the industrial space. “We’ve put in synchronization and sleep mode capability to allow a sensor network to essentially run indefinitely, when combined with the solar technology that Bob [Karschnia] is speaking of,” said Millennial Net Marketing Vice President Mark Pacelle, who also spoke at the emerging technologies session.

Hot oil method

BP’s Lafferty also described one energy scavenging technique used by his company on the North Slope of Alaska, where wireless sensors are being deployed for pipeline corrosion measurement programs. In these programs, “battery life is a huge issue,” Lafferty said. “So one of the things that we did was to actually cut into the insulation of the pipeline and put the batteries up against the pipe.” By tapping the heat from the oil flowing through the line, the technique has “greatly enhanced” battery life, Lafferty said.

“The good news is that in industrial environments, you have an incredible amount of energy sources out there,” Lafferty observed. “So the secret lies in finding ways to harness a lot of them.”

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