Sensing & Controls News

Thermo-Driven Energy Harvesting For Wireless Sensors

One of the latest trends in sensing technology is wireless devices, with a cutting-edge addition: energy harvesting solutions to avoid battery maintenance or an external power source.

The German manufacturer Micropelt recently introduced a mini thermo-harvester capable of producing power from minimum differences in temperatures of virtually any heat source, including – the company said – body heat under “favorable circumstances.” The only limitation is a maximum temperature of 200 °C in order not to destroy the generator and a minimum gradient of approximately 3 °C for running a DC converter.

Temperature differences are converted by the unit into electrical power and used to operate wireless sensors.

The new thermo-generator model MPG-D751 by Micropelt is a thin-film device of 3.3 by 4.2 by 1 mm. Built into a thermo-harvester such as Micropelt’s TE-Power NODE, it produces 140 millivolts per effective degree across the device, for example 2.8 V from a temperature gradient of 23 °C.

The company explained that the principle at the base of thermoelectric generators is the Seebeck effect, based on the fact that a heat flux through a thermoelectrically active material will generate a current flow and a voltage.

The engineers at Micropelt developed and specialized in the production of a 36-micron-thick thermoelectric film. A method that now brings economies of scale to thermoelectric volume production, the company said. At the same time they developed a structuring method for the thin-film which produces microscopic voltage generating elements (thermocouples), whose number defines the electric generating capability. For example they reported that the MPG-D751 contains 540 thermocouples which can produce one milliwatt of power from a temperature difference of approximately 8.5 °C.

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