Energy Scavenging for Remote Sensor Solutions

Paul Wright and his mechanical engineering students mounted a temperature sensor under a staircase at the University of California, Berkeley and fed its readings into the stairwell's thermostat.

ENERGY-RICH VIBRATIONS. Engineer Paul Wright and his students put this temperature sensor under a wooden stairway, where it scavenged all the energy it needed from vibrations generated by students clomping up and down. Wright

ENERGY-RICH VIBRATIONS. Engineer Paul Wright and his students put this temperature sensor under a wooden stairway, where it scavenged all the energy it needed from vibrations generated by students clomping up and down. Wright The sensor, which was about the size of a quarter, had no power cord or batteries. Instead, the device extracted the energy it needed from the vibrations that shook the wooden staircase as students clomped up and down between classes.

"The 1990s marked this very interesting period in which devices for computing, communication, and sensing all became much cheaper and much, much smaller," explains Wright. He's an engineer who has worked in robotics and computer science and is currently chief scientist at the Center for Information Technology Research in the Interests of Society, a multicampus program supported by the state of California.

The most obvious result of the miniaturization was a wild proliferation of cell phones, personal digital assistants, MP3 players, and other portable gadgets. But in parallel, Wright says, "researchers were led to this picture of wireless sensor networks everywhere"—in effect, an electronic nervous system that reports on both the built environment and the natural landscape.

In the not-so-distant future, for example, bridges could tell us whether they had been damaged in an earthquake.

Office buildings could track the locations of their occupants, automatically adjusting the lights and air conditioning for maximum comfort and minimum energy use. Automobiles could talk to each other—and to the road—in an effort to avoid both accidents and traffic jams. Implantable sensors could continuously monitor blood-glucose levels and a host of other medical conditions. And webs of environmental sensors could monitor the health of remote ecosystems, tracking moisture, temperature, micronutrients, pollutants, and many other variables. All these developments would rely on networks of minuscule sensors

Energy scavenging is not a new idea. Self-winding wristwatches, in which a tiny mechanical oscillator extracts energy from the wearer's arm movements, first appeared in the 1920s. And, of course, windmills and water wheels have been harvesting natural energy for thousands of years. But the current wave of interest in energy scavenging for microelectronics began in the late 1990s—initially because researchers were looking for a better way to power the newly devised portable devices.

Energy-scavenging researchers turned their focus from relatively power-hungry portable electronic devices to a new generation of far-more-thrifty gadgets made with microelectromechanical-systems (MEMS) technology.

From an energy-scavenging standpoint, the great advantage of MEMS sensors is that they typically require only about 100 microwatts of power—a thousandth of what portable consumer electronic devices typically need. Such minuscule quantities of energy abound in the environment: in vibrations, temperature gradients, sunlight, and so on.

The challenge is to make effective use of that energy. The first thing to keep in mind is that there is no all-purpose solution.

SOURCE: Read the entire fascinating article at ScienceNews.org

CALIFORNIA RESOURCE:
Paul K. Wright
5133 Etcheverry Hall, Mail Stop 1740
Department of Mechanical Engineering
University of California, Berkeley
Berkeley, CA 94720-1740