Power Electronics

Self-Powered Wireless Sensor Networks Eliminate Battery Maintenance

MicroStrain Inc, a Williston, Vt.- based producer of wireless sensing instruments, including microprocessor-based, multichannel, programmable transmitters, has a vision. The researchers there are looking at new ways of extracting energy from the environment and converting it into power for sensing devices. In fact, to dramatically increase the life span of wireless sensors, engineers at MicroStrain are exploring unique methods to harvest energy from the environment to power directly wireless sensors without using the conventional batteries or traditional wired source. In turn, this will create self-powered wireless sensing networks that can eliminate the tedious task of replacing conventional batteries, while giving them infinite life span.

Although sunlight, heat, wind, water and other natural sources have been tapped for generations, the engineers at MicroStrain are investigating mechanical strain as a new source of energy. Perhaps no other material is better suited for this application than the piezoelectric material whose properties are well known.

Toward that goal, the U.S. Navy has awarded MicroStrain a $700,000 research and development grant. Under this two-year program, a new class of wireless sensors will rely on harvesting strain and vibration energies from their working environment to sense information and to wirelessly transmit that information to a central host. This breakthrough will not only reduce the cost of sensor applications by reducing costly wiring and replacement of batteries, but it will also expand the types of applications where sensors can be deployed, according to the developer.

Phase I of this program will realize improvements in efficiency of the piezoelectric energy harvesting circuit, and development of mathematical models to facilitate piezoelectric energy harvesting from a straining structure and vibratory environment. Phase II will focus on integration with Navy infrastructure for shipboard network communications.

Meanwhile, efforts on a commercial version are also underway. The developer hopes to ready a feasible commercial part within 18 months.

In this scheme, strain energy is stored by rectifying piezoelectric fiber output into a capacitor bank. When the capacitor voltage reaches a preset threshold, power is transferred to an integrated wireless sensor. [To view a block diagram, click here.]

For more information, visit www.microstrain.com.

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