Karlsruher Institut für Technologie (KIT) scientists have now developed three-dimensional component architectures based on novel, printable thermoelectric materials. Thermoelectric generators, TEGs for short, convert ambient heat into electrical power. They enable maintenance-free, environmentally friendly, and autonomous power supply of the continuously growing number of sensors and devices for the Internet of Things (IoT) and recovery of waste heat. This work could very well be a milestone on the way towards use of inexpensive TEGs.

Professor Uli Lemmer, Head of the Light Technology Institute (LTI) of KIT said, “Thermoelectric generators directly convert thermal into electrical energy. This technology enables operation of autonomous sensors for the Internet of Things or in wearables, such as smart watches, fitness trackers, or digital glasses without batteries.” In addition, they might be used for the recovery of waste heat in industry and heating systems or in the geothermal energy sector.

With the help of newly developed inks and special production techniques, such as origami, inexpensive thermoelectric generators can be produced for various applications. Image Credit: Andres Rösch, Karlsruher Institut für Technologie. Click image for the largest view.

“Conventional TEGs have to be assembled from individual components using relatively complex manufacturing methods. To avoid this, we studied novel printable materials and developed two innovative processes and inks based on organic as well as on inorganic nanoparticles,” Lemmer said. These processes and inks can be used to produce inexpensive, three-dimensional printed TEGs.

The team’s research paper has been published in the Nature’s journal Flexible Electronics.

The first process uses screen printing to apply a 2D pattern onto an ultrathin flexible substrate foil using thermoelectric printing inks. Then, a generator having about the size of a sugar cube is folded by means of an origami technique. This method has been developed jointly by KIT researchers, the Heidelberg Innovation Lab, and a spinoff of KIT. The second process consists in printing a 3D scaffold, to the surfaces of which the thermoelectric ink is applied.

Professor Lemmer is convinced that scalable production processes, such as roll-to-roll screen printing or modern additive manufacturing (3D printing) are key technologies. “The new production processes not only enable inexpensive scalable production of these TEGs. Printing technologies also allow the component to be adapted to the applications. We are now working on commercializing the printed thermoelectrical system, he said.

Running at 47.8 µWcm² (microwatts per square centimeter) from a 30 K (1 K = ± 1.8° F or 54° F) temperature difference is quite an impressive result. Should this technology scale and still be very low cost, thermoelectric generation could very well start a consumer market in harvesting and scavenging lost heat back to electrical work or profit.

Perhaps this inventive work will trigger further improvements that might harness the more than half of the fuel we use being lost now as waste heat.


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