Large-area flexible printed thermoelectrics harvest energy from waste heat

March 29, 2013 // By Julien Happich
Large power stations only rarely manage to convert more than 40 percent of the produced energy into electrical power. The rest is released unused, mainly via the cooling towers, into the atmosphere.

Researchers at the Fraunhofer Institute for Material and Beam Technology IWS in Dresden, have been working on using the potential lying dormant in the over 150m high concrete giants. The idea is to use thermoelectric devices fitted inside cooling towers, where there can be very large differences between the hot steam and cooler concrete skin under some circumstances.

Dr. Aljoscha Roch of the Fraunhofer Institute for Material and Beam Technology IWS in Dresden explains: ”Thermoelectric generators (TEG) currently have an efficiency of around eight percent. That sounds very small. But if we succeed in producing TEG cost-effectively, on a large scale and from flexible materials we can install them extensively on the insides of the concave cooling tower wall. In this way, through the enormous amount of energy produced in the huge plants, we could generate large quantities of electricity”.

Together with his colleagues at the IWS, Roch has now taken a big step closer to this goal. The scientists have succeeded in producing TEG by means of a printing process. The miniaturized generators can not only be produced cost-effectively, on large surfaces and in a flexibly manageable manner, but an additional major advantage is that the materials used are environmentally-friendly. ”TEG are today largely produced by hand from toxic components which contain lead for example. We are now using modern 3D printing technology and harmless polymers (plastics) that are electrically conductive,” explains Roch.

3D printing makes it possible: A demonstrator of a printed TEG wriggles flexibly around a sample component. © Fraunhofer IWS



The new printing technology functions in a similar way to an inkjet printer. The difference is that instead of a thin jet of ink, a thermoelectrically active polymer paste emerges from the cartridge and produces the around 20 to 30 micrometer thick thermoelectric layers. “The generators have to be of a certain thickness in order to build up electrical voltage from temperature difference. Currently