May 2, 2009
Originally Published MPMN May 2009
Wireless Sensor System Features Battery-Free Operation
A wireless sensor node by Germany-based Micropelt is powered by harvesting thermoelectric energy.
When a product derives its power from batteries, the user is saddled with the inconvenience of replacing or recharging the power source. Removing batteries and plugs from the equation for hassle-free operation, Micropelt GmbH has developed what it claims is the world’s first thermopowered wireless sensor system.
“It is the first device offered that uses the concept of wireless sensing without using any battery or line power,” says Burkhard Habbe, vice president of business development. “[The TE-Power Node] is the first true autonomous, battery-free device that operates on a continuous basis and does not require any external power or maintenance.”
A specialist in thin-film thermoelectrics, Micropelt drew on its proprietary scalable microelecromechanical systems–based microstructuring platform technology to develop the TE-Power Node. Equipped with up to two of the company’s MPG-D751 thermogenerators, the sensor node operates by harvesting thermal energy from as little as 3.5°C of effective temperature differential. “Our technology uses the Seebeck effect, so it converts a heat flux driven by a temperature difference across the thermogenerator into electrical power,” Habbe explains. This thermoharvesting technology provides the node with a renewable, battery-free, unlimited power source from an outside temperature difference of 15°C or more. Habbe adds that the system is also an environmentally friendly alternative to batteries.
Depending on application requirements, either one or two of the thermogenerators is affixed to an aluminum base plate with a footprint measuring 60 × 27 mm. An aluminum heat spreader, designed with threaded holes for easy access to various heat sinks, is positioned on top of the thermogenerators. It is stabilized and insulated by a printed circuit board, which features the receptacles for plug-in modules. Also incorporated in the product is a modified version of the company’s TE-Power Plus dc-dc convertor designed to change the variable incoming thermoharvested voltage into a battery-like constant 2.4 V. “Even a few-hundred microwatts supplied continuously can easily outperform a good set of batteries,” according to Habbe.
With its battery-free and thermal-energy-based operation, the wireless sensor node could be integrated into medical equipment in order to monitor such elements as temperature, sudden temperature changes, pressure, shock, and vibration. Furthermore, the company sees potential for the device’s use in nonimplantable monitoring applications for patients, providing ultra-low-power wireless sensing of human body functions based on body heat harvesting.
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