Many years of innovation in power harvesting have brought some maturity to solar, wind, geothermal and even wave technologies. Solar panels have become ubiquitous, General Electric has mastered the megawatt-caliber wind and geothermal turbine, and younger companies like Finavera Renewables have harnessed ocean-wave motion with electrical- generator technologies.
On the horizon, however, is a new wave of power harvesting. A variety of technologies eliminate the need for batteries through the use of innovative transducers that generate electricity by virtue of converting the linear motion of pushing a button, the vibrations on an aircraft, the fluctuations of a magnetic field, the radio waves that fill the air and ever-present environmental gradients such as changes in temperature.
"The market for this new field of power harvesting is very small today, but we expect units shipped to exceed 200 million by 2010," said Darnell Group Inc. analyst Linnea Brush, who is preparing a report on power harvesting. Darnell will host NanoPower Forum 2007, a conference on energy harvesting and power-management solutions, June 4-7 in San Jose, Calif. (http://nanopower.darnell.com/ index.php). "The first systems will be applications where batteries cannot be used or would be very problematic, such as wireless sensor nets in remote locations," said Brush. "When the cost can be reduced in a few years, we will see many industrial and commercial applications such as light, temperature, humidity and other building controls." Transportation will be next, "and finally, consumer and medical markets."
Early adopters, such as contemporary oil fields, are already retrofitting wired sensor networks with wireless versions that never require battery replacement by virtue of power harvesting. But as the cost of the technology drops, retrofits will give way to equipment designed to be battery-free from the start.
Power harvesting for battery replacement is typically low voltage and low current at this point, but as new architectures and new materials increase efficiency, the technology is destined to tackle higher-power applications. Building wiring today is being retrofitted with wireless switches that generate RF power from the linear motion of pushing the button. But home wiring tomorrow could be designed to use wireless switches from the get-go.
Powering the venerable light bulb with harvested energy is still a thing of the future, since it requires tens of watts vs. the micro- and milliwatts harvested today. But eventually, even home lighting could become wireless and self-powered.
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