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Tiny devices harvest heat from machines to power sensors

07 December, 2007

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A German start-up company is offering a technology for tapping the heat from industrial equipment and using it to power devices such as wireless sensors used for condition monitoring, predictive maintenance and other duties.

The company, Micropelt, was set up on 2006 to exploit a technology developed jointly by the chip-maker Infineon and the Fraunhofer Institute for Physical Measurement Techniques. It is based on the well-established Peltier thermoelectric effect, by which heat is converted into electrical energy. Most previous attempts to apply the effect commercially have been inefficient and costly.

Micropelt generator

The new thermoelectric devices – based on silicon MEMS (microelectromechanical systems) technology – are much smaller than earlier devices with ten times higher power densities, and they promise economies of scale similar to those found in chip-making industries.

An array of the 1mm2 devices is combined with special DC-DC converters to produce a constant voltage of 1.2-5V across a wide range of operating temperatures. A temperature difference of 10–20°C between a machine and the surrounding air can produce an output of a few hundred µA. Larger temperature differences and specialised heatsinks can boost the output to mA levels.

The energy gathered can be used to charge a battery or to supply a low-power electronic device directly. Micropelt envisages its devices being built into wireless sensors, avoiding the need to install permanently wired power supplies or to replace batteries.

Micropelt is producing kits (shown above) that allow potential users to evaluate its energy-harvesting technology.

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