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Publication in Nature Com­mu­ni­ca­tions

Team Led by TU Dort­mund Recycles Heat

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Gerät zum recyclen von Wärmeenergie © TU Dort­mund
In this device, too, the waste heat could be recycled.

When electronic devices are operating, energy is wasted as heat. While large machines can already make use of waste heat, up to now this has not been possible on the level of microprocessors. An in­ter­na­tio­nal research team headed by TU Dort­mund University has now managed to do it. The researchers present their results in the renowned scientific journal Nature Com­mu­ni­ca­tions.

Information and communications technologies currently account for around 1.5 percent of the world's entire energy consumption, for example in the use of computers and mobile phones. When they're running, a large share of this energy is uselessly converted into heat, which in turn needs to be cooled down at great expense. Some high-performance computer processors get so hot that you could fry eggs on them.

One approach to tackling this problem is to further reduce energy consumption. On the other hand, an attempt can be made to convert the resulting heat back into usable energy. In principle, this has been possible for some time with large machines. In automobiles, for example, the hot combustion gases can be used in small "steam engines" or thermoelectric generators to produce electricity for the on-board electronics.

On the level of very small processors whose individual components are just a few billionths of a meter in size, such a conversion of heat into usable energy has not been possible. Yet that is precisely what a team of researchers from Dort­mund, St. Petersburg, Nottingham, Kiev, and Le Mans has now managed to do. They present their results in the current edition of the renowned interdisciplinary journal Nature Com­mu­ni­ca­tions.

A billion switching processes per second

In modern electronics, a billion or more switching processes per second are carried out in a single processor. With every switching operation, the processor heats up and then cools down until the next takes place. The temperature of the processor therefore fluctuates accordingly: It is heated up and cooled down a billion times per second.

In their investigations, the researchers simulated these switching processes by bombarding a chip with laser pulses spaced one-billionth of a second apart. They used the resulting periodic temperature variation to generate recyclable energy from the unused heat and transfer it to a magnetic layer. Such a layer can be used to store and process in­for­mation: The energy gained can be used – in the form of magnons, the elementary particles of a spin wave –  to switch the magnetic layer and thus to operate in­for­mation technology devices.

"Such a temperature modulation is already present in many electronic devices," says Dr. Alexey Scherbakov, who is part of the research team associated with the TU Dort­mund University physicist and rector Prof. Manfred Bayer. "With our research, we were able to show how you can use it instead of wasting it."

Original publication:
Kobecki, M., Scherbakov, A.V., Linnik, T.L. et al.: Resonant thermal energy transfer to magnons in a ferromagnetic nanolayer. Nat Commun 11, 4130 (2020). https://doi.org/10.1038/s41467-020-17635-1

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The campus of TU Dort­mund University is located close to interstate junction Dort­mund West, where the Sauerlandlinie A 45 (Frankfurt-Dort­mund) crosses the Ruhrschnellweg B 1 / A 40. The best interstate exit to take from A 45 is "Dort­mund-Eichlinghofen" (closer to Campus Süd), and from B 1 / A 40 "Dort­mund-Dorstfeld" (closer to Campus Nord). Signs for the uni­ver­si­ty are located at both exits. Also, there is a new exit before you pass over the B 1-bridge leading into Dort­mund.

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TU Dort­mund University has its own train station ("Dort­mund Uni­ver­si­tät"). From there, suburban trains (S-Bahn) leave for Dort­mund main station ("Dort­mund Hauptbahnhof") and Düsseldorf main station via the "Düsseldorf Airport Train Station" (take S-Bahn number 1, which leaves every 20 or 30 minutes). The uni­ver­si­ty is easily reached from Bochum, Essen, Mülheim an der Ruhr and Duisburg.

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