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Themeninfos – A compact guide to energy research

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The NASA explores the surface of mars with a robot named Curiosity. A thermoelectric generator supplies its energy.
© NASA / JPL-Caltech /Malin Space Science Systems
Thermoelectric generators
Themeninfo I/2016
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Thermoelectrics: power from waste heat

Waste heat is produced in all areas of daily life – in industry, homes and transport. In Germany alone, this adds up to a waste heat potential of 300 TWh per year. This energy volume corresponds to nearly half the total energy consumed by German industry. Thermoelectric generators (TEGs) can tap into this huge energy reservoir and transform the "waste energy" without moving parts into a higher form of energy. The TEG utilise waste heat and already produce electricity from small temperature differences. This recycling of waste or ambient heat that would otherwise be lost is also known as energy harvesting, which in future will make an important contribution to achieving energy efficiency and reducing CO2 emissions.

Thermoelectric modules can not only convert heat directly into electricity but also, in the form of an electric heat pump, use electricity to provide direct cooling and heating: these days, industry uses Peltier coolers for controlling the temperature of car seats or for stabilising the temperature of electronic components. In the consumer goods sector, these coolers can also be found, for example, in camping cool boxes and silent hotel fridges. In their simplest form, thermoelectric modules consist of a thermocouple that is used in many applications as a temperature sensor. This is constructed from two thermoelectric materials whose electrical junctions are at different temperature levels. The first thermoelectric materials could only be produced at great expense and generated only a few watts. These days systems are now available that generate up to 1000 watts. New materials and processing methods enable greater temperature differences to be utilised, whereby the power output will also continue to rise.

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Researchers and manufacturers are working to increase the efficiency of thermoelectric generators and develop appropriate manufacturing processes for mass production. Similar to photovoltaics, the way has now been paved for using a technology originally developed to supply vehicles in outer space, such as the Mars rover, Curiosity, for a wide range of uses in various applications. This Themeninfo brochure provides an overview of how the technology functions and its application areas, as well as the materials that are being developed and optimised for different temperature ranges.

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