Thermoelectric generators, or TEGs for short, convert ambient heat into electrical energy. They offer a maintenance-free, environmentally friendly and self-sufficient power supply for the steadily growing number of sensors and devices for the Internet of Things (IoT) and a possibility for the recovery of waste heat. Scientists at the Karlsruhe Institute of Technology (KIT) have now developed three-dimensional component architectures with novel, printable thermoelectric materials. These could represent a milestone for the use of inexpensive TEGs. They report on their results in the journals npj Flexible Electronics (DOI: 10.1038 / s41528-020-00098-1) and ACS Energy Letters (DOI: 10.1021 / acsenergylett.0c02159).
“Thermoelectric generators can convert thermal energy directly into electrical energy. This technology allows energy self-sufficient sensors for the Internet of Things or in wearables, such as smartwatches, fitness wristbands or digital glasses, to be operated without batteries, ”says Professor Uli Lemmer, Head of the Light Technology Institute (LTI) at KIT. Furthermore, they could be used in the recovery of waste heat in industry and in heating systems or geothermal energy.
New printing processes thanks to customized inks
"Conventional TEGs have to be assembled from individual parts using relatively complex manufacturing processes," says Lemmer. “To get around this, we researched new types of printable materials and, in addition to two innovative processes, developed both organic and inorganic inks based on nanoparticles.” These could be used to produce inexpensive, three-dimensional printed TEGs.
In the first method, a 2D pattern of thermoelectric printing inks is applied to a wafer-thin, flexible substrate film by means of screen printing and then a cuboid generator the size of a sugar cube is folded up using an origami technique. The KIT scientists developed this method together with the InnovationLab in Heidelberg and a KIT spin-off company. In the second process, the researchers first print a 3D framework, on whose surfaces they then apply the thermoelectric ink.
Cost savings through printing technologies
Lemmer is convinced that highly scalable manufacturing processes such as printing in roll-to-roll screen printing or in modern additive manufacturing (3D printing) are key technologies. “The new manufacturing processes not only allow cost-effective and scalable production of these TEGs, but the printing technologies allow the component to be individually adapted to the respective application. We are working hard to make printed thermoelectrics commercially available, ”he emphasizes.
The German Research Foundation (DFG), the Federal Ministry of Education and Research (BMBF), the Graduate School MERAGEM and the German Federal Environmental Foundation (DBU) have supported research within the 3DMM2O Cluster of Excellence.
Andres Georg Rösch, André Gall, Silas Aslan, Matthias Hecht, Leonard Franke, Md. Mofasser Mallick, Lara Penth, Daniel Bahro, Daniel Friderich, and Ulrich Lemmer: Fully printed origami thermoelectric generators for energy-harvesting. npj Flex Electron 5, 1 (2021). https://doi.org/10.1038/s41528-020-00098-1
Md Mofasser Mallick, Leonard Franke, Andres Georg Rösch, and Uli Lemmer: Shape-Versatile 3D Thermoelectric Generators by Additive Manufacturing ACS Energy Lett. 6, 85 (2021). https://doi.org/10.1021/acsenergylett.0c02159