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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).

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Location & approach

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.

To get from Campus Nord to Campus Süd by car, there is the connection via Vogelpothsweg/Baroper Straße. We recommend you leave your car on one of the parking lots at Campus Nord and use the H-Bahn (suspended monorail system), which conveniently connects the two campuses.

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.

You can also take the bus or subway train from Dort­mund city to the uni­ver­si­ty: From Dort­mund main station, you can take any train bound for the Station "Stadtgarten", usually lines U41, U45, U 47 and U49. At "Stadtgarten" you switch trains and get on line U42 towards "Hombruch". Look out for the Station "An der Palmweide". From the bus stop just across the road, busses bound for TU Dort­mund University leave every ten minutes (445, 447 and 462). Another option is to take the subway routes U41, U45, U47 and U49 from Dort­mund main station to the stop "Dort­mund Kampstraße". From there, take U43 or U44 to the stop "Dort­mund Wittener Straße". Switch to bus line 447 and get off at "Dort­mund Uni­ver­si­tät S".

The AirportExpress is a fast and convenient means of transport from Dort­mund Airport (DTM) to Dort­mund Central Station, taking you there in little more than 20 minutes. From Dort­mund Central Station, you can continue to the uni­ver­si­ty campus by interurban railway (S-Bahn). A larger range of in­ter­na­tio­nal flight connections is offered at Düsseldorf Airport (DUS), which is about 60 kilometres away and can be directly reached by S-Bahn from the uni­ver­si­ty station.

The H-Bahn is one of the hallmarks of TU Dort­mund University. There are two stations on Campus Nord. One ("Dort­mund Uni­ver­si­tät S") is directly located at the suburban train stop, which connects the uni­ver­si­ty directly with the city of Dort­mund and the rest of the Ruhr Area. Also from this station, there are connections to the "Technologiepark" and (via Campus Süd) Eichlinghofen. The other station is located at the dining hall at Campus Nord and offers a direct connection to Campus Süd every five minutes.

The facilities of TU Dort­mund University are spread over two campuses, the larger Campus North and the smaller Campus South. Additionally, some areas of the uni­ver­si­ty are located in the adjacent "Technologiepark".

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