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Billions of dollars lost each year as waste heat from industrial processes can be converted into electricity with a technology being developed at the Department of Energy's Oak Ridge National Laboratory. The high-efficiency thermal waste heat energy converter actively cools electronic devices, photovoltaic cells, computers and large waste heat-producing systems while generating electricity, according to Scott Hunter, who leads the development team. The potential for energy savings is enormous.
Wireless sensor nodes are nowadays employed in many different application fields such as healthcare, automotive and predictive maintenance, but these sensors currently provide limited lifetime as they require significant power for operation. Increasing lifetime, preferably unlimited, becomes possible with energy harvesting. One promising way for power generation is vibrations, and an electrostatic transduction method can be employed to transfer mechanical into electrical energy. An electrostatic energy harvester is, in essence, a movable capacitor which needs a high voltage source for power generation. A patterned electret could operate as this voltage source. In its most general meaning, an electret is a material that stores a quasi-permanent electric charge upon its polarization. It can be called the electrical equivalent of a permanent magnet. It is an important component for a MEMS based energy harvester.
Microbots based on MEMS have long been sought to collect environmental samples, to search for survivors in collapsed buildings and for other reconnaissance style missions that are ill-suited for people. Although decades in the making, one major “hang-up” for fully autonomous operation of such microbots remains – a locomotion source. The tiny mechanisms and electrical circuitry are relatively easy to cast, but currently there are no reliable locomotion sources on such a small scale.
Energy harvesting is an attractive way to power MEMS sensors and locator devices such as GPS; however, the power harvesting technologies often fall short in terms of power output. For example, vibratory MEMS generators might give out only microwatts of electrical power. While this may be sufficient for emerging ultra low power sensors, many current applications require milliwatt power levels. As an example, commercially available running sensors for shoes consume over 100 uW of electrical power and requirements for GPS locators are even higher.
