Researchers at Clarkson University in Potsdam, NY, have developed technology that uses the vibrations caused by passing traffic to power wireless bridge monitoring sensors.

Wireless battery-powered sensors that monitor bridges and report changes that may lead to failure are easy to install, but it is unwieldy to provide power for the sensors. Each bridge needs at least several sensors, many installed in hard-to-access locations. Replacing millions of batteries could become a problem, adding to the expense of maintaining the bridges. The Clarkson researchers have found a way around this problem.

“We have completely eliminated the battery from the equation,” said assistant professor Edward S. Sazonov, who developed the technology along with professor Pragasen Pillay. “Hermetically sealed wireless sensors powered by bridge vibration can re-main on the bridge without need of maintenance for decades, providing continuous monitoring of such parameters as ice condi-tions, traffic flows and health status.”

The two electrical and computer engineering professors, along with graduate students Darrell Curry and Haodong Li, used the New York State Route 11 bridge, a steel girder structure, which runs over the Raquette River in Potsdam as a case study.

Energy was harvested by locating an electromagnetic generator on a girder. The harvester responded to one of the natural vi-bration frequencies of the bridge. Each time a car or a truck passed over the bridge, even in a different lane from the sensor in-stallation, the whole structure vibrated and excited the mover in the generator, producing electrical energy. Harvested electrical energy powered unique wireless sensors that increased energy output of the harvester and consumed only microwatts of power while performing useful tasks.

Sazonov and Pillay have been invited to present their work at the Transportation Research Board of the National Acade-mies Meeting in Washington, D.C., in January. The board provides support for their research.

Wireless monitoring of bridges and overpasses has gained much attention in the past few years. Bridge collapses happen sud-denly and unpredictably, often leading to tragic loss of human life. In 2006, the Federal Highway Administration listed 25.8 percent of the nation’s 596,842 bridges as either structurally deficient or functionally obsolete. While many of these bridges will remain in service for years, they need monitoring and rehabilitation. Currently, bridge monitoring is performed through periodic visual inspections. In the tragic example of I-35W bridge collapse in Minneapolis on Aug. 1, 2007, the bridge passed a visual inspection a year prior to failure.

Devices and technological advancements such as these may prove to ensure the confidence in bridges for years. Furthermore, this kind of kinetic energy harvesting is catching on. You may have read about the Michigan Technological University researchers that can power an iPod with a backpack that captures the energy produced by simply moving while wearing it. In addition, the November 2007 issue of ELECTRICAL CONTRACTOR contained a story about Massachusetts Institute of Technology students that are developing a way to capture the energy created by footsteps. Your hyperactive children may soon be able to contribute to the household after all. EC