TU Graz Research 2019-1/21 DE

TU Graz

SCIENCE PASSION #24 research TECHNOLOGY < DE | 2020-2 | EN Research Journal of Graz University of Technology

HYDROGEN: ELECTRICITY STOR-

AGE OF THE FUTURE?

RELEVANCE OF HYDROGEN RAINBOW-COLOURED BATTERY SAFETY FOR THE FUTURE COMBS CENTER GRAZ

CONTENTS TU Graz research 2020-2/#24 Contents

Editorial: Vice Rector Horst Bischof

Hydrogen

■ Hydrogen: Electricity Storage of the Future?

■ Commentary: Alexander Trattner

Portrait ■ Rainbow-Coloured Combs and Sunlight Birgitta Schultze-Bernhardt

Infrastructure ■ Battery Safety Center Graz

Newsflash

Fields of Expertise

Advanced Materials Science ■ Editorial: Anna Maria Coclite, Christof Sommitsch, Gregor Trimmel ■ Hydrogen Embrittlement (HE) of Ultra-High-Strength Steel Screws in Service: Still a Development Potential? Andreas Drexler, Hamdi Elsayed, Rudolf Vallant

Human & Biotechnology ■ Editorial: Gabriele Berg, Gernot Müller-Putz, Bernd Nidetzky ■ Fast, Accurate and Built to Fit: Computational Protein Design to Address Challenges in Biotechnology Gustav Oberdorfer

Information, Communication & Computing ■ Editorial Kay Uwe Römer ■ The Future of Computing: Learning-Based, Energy-Efficient and Brain-Inspired Robert Legenstein

Mobility & Production ■ Editorial: Rudolf Pichler ■ Research on Next Generation Fuel Cell and Hydrogen Technologies Sebastian Bock

Sustainable Systems ■ Editorial: Urs Leonhard Hirschberg ■ Enhancing Production of Hydropower Plants and Eco-Friendly Electricity Generation Helmut Benigni

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Publication details: Owner: TU Graz. Publisher: Vice Rector for Research. Editor-in-Chief: Birgit Baustädter, Communi- cations and Marketing, Rechbauerstraße 12/I, 8010 Graz. E-Mail: [email protected] Design/layout: Christina Fraueneder, TU Graz; Petra Temmel, manege frei!. Trans- lation: Andrew Peaston. Printing: Druckhaus Scharner. Print run: 2,000 copies. Our thanks to the authors for pro- viding the texts and photos. The editors reserve the right to make minor changes. Cover picture: peterschreiber. media – AdobeStock. TU Graz research is published twice a year. © TU Graz Publishing 2020, www.ub.tugraz.at/ Verlag. ISSN 2664-1712. www.tugraz.at/research-journall EDITORIAL TU Graz research 2020-2/#24 Dear colleagues, research partners, and everyone interested in research at TU Graz,

Horst Bischof Vice Rector for Research Source: Oliver Wolf

Right now it seems like there’s only one issue: COVID-19. No matter where you look, it is the dominant theme. In addition to all the restrictions and efforts being made, the corona virus has shown us one thing clearly: how important research is and especially basic research. The PCR (the method used to amplify DNA in COVID tests) was developed as early as 1983 (but of course not to develop tests against vi- ruses). Imagine if we didn’t have reliable tests today. If there really is a reliable vaccine soon, which of course we all hope there will be, then that will be a triumph of science. Such a development in such a short time only works if you build on the strong foundation of solid basic research.

At Graz University of Technology we have so far come through the pandemic very well. Teaching has experienced a digitalization push (we were well prepared for this) and research has continued in many parts without any significant restrictions. In many cases it has even led to more papers and more research proposals being written. And we have achieved a number of sensational successes in recent months. Our colleague Birgitta Schultze-Bernhardt from the Institute of Ex- perimental Physics has received both the FWF Start Prize and an ERC Starting Grant for her research in the field of the interaction between UV light and matter. And recently we were informed that Harald Plank from the Institute of Electron Microscopy and Nanoanalysis has received the highly endowed Houska Prize for his research in the field of nanoprinting. Un- fortunately we haven’t been able to celebrate these prizes in a bigger context – but we will definitely make up for it.

Perhaps the current situation has something good in store for us. Instead of a hectic pre-Christmas period with many appointments, there may be more time for your loved ones and some reflection. And possibly during the holidays, some time to browse through this research magazine. In this spirit, I hope you enjoy reading this new issue of TU Graz research, and I wish you and your families a merry Christ- mas and a great start to the new year. GLOBAL CHALLENGES TU Graz research Hydrogen 2020-2/#24 Hydrogen: Electricity Storage of the Future? If our energy system is to become more eco-friendly, there is no way to avoid hydrogen as an energy carrier. Researchers around the world are certain of this. Some 160 scientists at TU Graz are working on methods for hydrogen production, storage, transport and use in mobile, stationary and industrial applications.

Birgit Baustädter

Hydrogen is the first element in the periodic table. Not only here does it occupy a prom- inent place, but also in the discussion about an eco-friendly energy system of the future. “At the turn of the millennium, it was agreed to use hydrogen as an energy carrier,” explains Vik- tor Hacker, who established the Fuel Cell and Hydrogen Systems Laboratory at Graz Univer- sity of Technology in 2001 and today heads the Fuel Cell and Hydrogen Systems working group. “As a strategic and climate-friendly energy carrier, hydrogen is the best common de- nominator for a variety of applications.”

The Fuel Cells and Hydrogen Systems research group works on low temperature fuel cells and hydrogen systems. Source: Lunghammer – TU Graz

Renewable energy sources, such as the sun, are subject to frequent fluctuations. There are many hours of sunshine in summer and few in winter for example – even rainy weather and fog have an impact on the yield of solar systems. In order to be able to compensate for these peaks and troughs, the energy must be efficiently stored and made available again. This can be done with batteries, for example. But the more energy to be stored, the larger the battery has to be. However, hydrogen could also be produced from the excess energy by electrolysis. “The advantages of hydrogen in mobility for example in- clude the long range and short refuelling times of fuel cell vehicles, which are already comparable with conventional fuels,” explains Viktor Hacker. “Even though we haven’t quite got there yet, in the medium and long term, the costs of hydrogen as an energy carrier are the main ar- gument in favour of it.”

More about the HyStORM project.

PRODUCTION, STORAGE, TRANSPORT On hydrogen itself, there is not much left to research, Viktor Hacker continues: “Hydrogen is commercially available, it’s just currently expen- sive.” However, it is important to become active in the field of decentralized production, on the one hand, and in the field of hydrogen transport, on the other. Hacker’s working group took on both aspects in the HyStORM (Hydrogen Storage via Oxidase and Reduction of Metal) research project. Together with the Graz-based start-up Rouge H2, they developed the chemical- looping hydrogen method. This involves producing a syngas from biomass, biogas or natural gas, and storing its energy in a metal oxide by means of a redox process. The metal oxide can be transported and stored safely and without loss. If water is subsequently fed back into the system, high-purity hydrogen is extracted.

EU-Project HyMethShip At the LEC (Large Engines Competence Center), at which the TU Graz is a major shareholder, Andreas Wimmer and his team are doing research on a propulsion concept for ships based on a hydrogen- powered IC engine. Methanol is used to store the hydrogen on board of the ship. For engine operation, the hydrogen is separated from the methanol via a

membrane reactor. The CO2 produced in this process is stored and is processed back on land with green hydrogen to generate methanol again. GLOBAL CHALLENGES TU Graz research 2020-2/#24

A system for the production of hydrogen from biomass is also being developed. In addition to the Institute of Chemical Engineering and Envi- ronmental Technology, the Institute of Thermal Engineering and the BEST (Bioenergy and Sus- tainable Technologies) competence centre are also involved in the BIO-LOOP project. Again together with the company Rouge H2, the developed systemis to be implemented directly with a local biogas producer.

KEY THEME: FUEL CELLS “Fuel cells will be key to the spread of hydrogen technologies because they enable us to compete with conventional technologies,” says Hacker. In the fuel cell, the energy stored in hydrogen is released again via a chemical process; it acts as an energy converter. “The main challenges at present are the service life and costs of fuel cells,” explains Hacker. He conducts research in the field of low-temperature fuel cells, especially polymer electrolyte fuel cells with an operating temperature of 80 degrees Celsius. The researchers expose the cell to adverse conditions – for example, freez- ing it or starting it at below 0 degrees Celsius – and try to increase its service life under these conditions. In addition, a patent has just been submitted for a method to reduce the corrosion of carbon in the electrode of the fuel cell by a thin layer of polyaniline. “We are working on the prototype of a fuel cell with this new technology.” In the longer term, according to Hacker, the aim is also to increase efficiency. “We are currently talking about an efficiency of a good 60 percent in a fuel cell. But I think we can get a lot more out of it.”

HIGH-TEMPERATURE FUEL CELLS Another, still very recent type of fuel cell already has a higher efficiency. High-temperature fuel cells operate at around 800 degrees Celsius and can, on the one hand, release the energy stored in the hydrogen, but can also produce hydrogen by electrolysis in the reversible operating mode. “The electrolysis efficiencies are therefore over 80 percent,” explains Christoph Hochenauer, head of the Institute of Thermal Engineering. And low-temperature fuel cells only work with high-purity hydrogen, while high-temperature fuel cells can use a wide variety of gases, such as carbon monoxide, natural gas or ammonia. “High-temperature fuel cells are very fuel flexible and can generate electricity from almost everything that is currently available on the market,” summarizes Hochenauer. But the high-temperature fuel cell is not yet sufficiently developed to be available on the market on a large scale or to be implemented in existing applications.

Vanja Subotić and Christoph Hochenauer are researching high-temperature fuel cells at the Institute of Thermal Engineering. Source: Lunghammer – TU Graz

Vanja Subotić, also from the Institute of Ther- mal Engineering, is working on the durability of high-temperature fuel cells. “The change in operation between electrolysis and power generation means that the fuel cell ages particularly quickly,” she explains. She is investigating the processes behind this and is trying to inhibit them and ensure a long and safe operation of the fuel cell. “In the framework of the current AGRO-SOFC project, we are trying to make the agricultural industry more sustainable and reduce the costs of food production by using a highly efficient fuel cell system coupled with

CO2 recycling.” Subotić and Hochenauer are jointly involved in the Hotflex project. As part of an Austria- wide research association, a pilot plant for high-temperature electrolysis and fuel cell operation was built in Mellach in Styria. “Here, we are trying to define the operating limits of the plant and test its efficiency and integration in power plant operation,” explains Hochenauer. “A basic understanding of various ageing and damage mechanisms is to be created in the FWF-SOEC project. The knowledge gained in this way is to be further developed into methods that make it possible to monitor the operation of electrolysis and fuel cell plants and extend their service life,” says Subotić. GLOBAL CHALLENGES TU Graz research 2020-2/#24 FUEL CELL AND COMBUSTION ENGINE At the Institute of Internal Combustion En- gines and Thermodynamics, several hydrogen- powered applications can be tested on one and the same test bench. Here, research is being conducted on both fuel cells and hydrogen- powered combustion engines. “The fuel cell has a higher efficiency than a combustion engine – at least at low loads,” explains Institute head Helmut Eichlseder. “The combustion engine, on the other hand, is robust and durable. And it could be quickly implemented technologically with hydrogen power.” According to Eichlseder, hydrogen-powered combustion engines are a promising alterna- tive, especially for heavy commercial vehicles: “The efficiency of a fuel cell decreases with the amount of the load – in heavy goods vehicles, for example, a combustion engine is the same.” In order to achieve the climate targets for 2030, the researcher is certain that at least commercial vehicles have to be converted to hydrogen propulsion. “It is feasible with relatively moder- ate modifications to conventional combustion engines and can be implemented on the existing infrastructure.”

At the Institute of Internal Combustion Engines and Thermodynamics they work with fuel cells as well as with hydrogen powered combustion engines. Source: Lunghammer – TU Graz

Until then, there are still some things to be done on the research side. Because even hydrogen- powered combustion engines cannot be operated entirely without pollutant emissions, the exhaust gas after-treatment system must be improved in order to achieve a zero emission level. And with the Bosch company, the team is working on the injection system, which is responsible for the correct mixture formation.

E-Fuels “Hydrogen is basically the first electrofuel; it is produced by means of electrical energy,” explains Helmut Eichlseder. He is convinced of the importance of e-fuels and sees lots of potential in them. “They are produced by electrolysis and then processed into a liquid fuel.” The e-fuels can then be used in combustion engines.

COMPETENCE CENTRE HYCENTA The competence centre HyCentA (Hydrogen Center Austria) at Campus Inffeldgasse, in which TU Graz has a majority shareholding, is completely dedicated to hydrogen research. The centre was established in 2005 as the first and currently only research centre focusing solely on hydrogen. It built the first hydrogen filling station in Austria, developed the first -hy drogen vehicle approved for road use in Austria and the first power-to-gas plant. Today the centre operates a hydrogen refuelling system, several test rigs for electrolysis, fuel cell systems and high-pressure hydrogen up to 1,000 bar. “In autumn 2020, the HyCentA test facility will be expanded by a further 600 square meters to further strengthen hydrogen research in Graz,” says Alexander Trattner.

Managing director Alexander Trattner talks about the value of hydrogen ! for the future on page 9.

Visit the website of the competence center HyCentA.

Projekt HyTrail In the HyTrail project, the Institute of Rail- way Engineering and Transport Economy of TU Graz, together with the hydrogen competence centre HyCentA, the Uni- versity of Leoben, the Johannes Kepler University Linz and the Synergesis company, conducted a comprehensive feasibility study on hydrogen for ÖBB (Austrian rail- ways) from 2018 to 2019. It was examined whether diesel-powered locomotives could be replaced by hydrogen-powered ones. A hydrogen train is already in trial operation on one of the lines investigated.

HYDROGEN CORROSION The transport and storage of hydrogen is also becoming a central issue. Hydrogen can attack metallic materials, causing what’s known as hydrogen corrosion. The very small atom pene- trates the material structure, embeds itself and makes the metal brittle. “You often don’t see the deformation for a very long time and sud- denly a fatal crack appears,” explains Rudolf Vallant from the Institute of Materials Science, Joining and Forming. Together with his colleagues Andreas Drexler and Hamdi Elsayed, he is researching how hydrogen corrosion oc- curs and how it can be prevented in the framework of the HISCC UHSS project (Improvement of hydrogen-induced stress corrosion cracking resistance of ultra-high strength steel screws and fasteners). “The corrosion problem was solved in the 1970s for the materials of that time. Today, however, there is a much stronger trend towards thin and high-performance materials, which have completely different load limits compared to materials of the past. So now we have to ask ourselves once again whether these new materials can withstand hydrogen,” says Andreas Drexler, explaining the subject’s renewed topicality. GLOBAL CHALLENGES TU Graz research 2020-2/#24

The researchers developed special corrosion cells for their experiments. In these cells the material is charged with hydrogen and the stress is slowly increased. “An experiment may take several days. So we can measure very precisely what happens at different concentrations of hydrogen.” Finally, their results are to be used in the field of mobility and transport and in the construction of hydrogen pipelines or tanks.

HYDROGEN AS AN ENERGY SOURCE FOR

THE PRODUCTION OF ANIMAL FEED FROM CO2 Robert Kourist and Bernd Nidetzky have a completely different research approach to the use of hydrogen in a collaboration between the Institutes of Molecular Biotechnology and Bio- technology and Biochemical Engineering. They want to optimize bacteria that use hydrogen to bind CO2, and then chemically extract proteins and amino acids from the bound CO2, which can be used for the production of animal feed.

“We want to turn CO2 into foodstuffs, so to speak,” summarizes Kourist. The bacteria currently under investigation grow too slowly and are not sufficiently productive to be used on a large industrial scale. Together with the acib GmbH competence centre (Austrian Centre of Industrial Biotechnology) and the Institute of Biotechnology and Biochemical Engineering, a project has now been launched to investigate and optimize the reactor environment and, at the same time, the bacteria themselves. Fur- thermore, TU Graz together with acib is participating in the Marie Skłodowska-Curie ITN ConCO2rde, which deals with the biotechnological use of hydrogen. The project leader at the Institute of Molecular Biotechnology is An- ita Emmerstorfer-Augustin, and at the Institute of Biotechnology and Biochemical Engineer- ing Regina Kratzer.

Für den am Institut verfolgten Ansatz sieht Kourist großes Potenzial: „Wasserstoff wird als

Anita Emmerstorfer-Augustin of the Institute of Molecular Biotechnology and Regina Kratzer of the Institute of Biotechnology and Biochemical Engineering Source: Baustädter– TU Graz

Kourist sees great potential for the approach pursued at the Institute: “Hydrogen will be readily available as a raw material source. And once it is cheap enough to run engines, it will also be cheap enough to produce chemicals from it. The future belongs to hydrogen and we want to work on that.”

Bernd Nidetzky of the Institute of Biotechnology and Biochemical Engineering. Source: Lunghammer – TU Graz

Robert Kourist of the Institute of Molecular Biotechnology. Source: Baustädter– TU Graz GLOBAL CHALLENGES TU Graz research 2020-2/#24

ConCO2rde ConCO2rde is a project within the Marie Skłodowska-Curie ITN Initiative. The aim of the project is to train young researchers in new technologies for

hydrogen use and CO2 utilization. The Institutes of Molecular Biotechnology and Biotechnology and Bioprocess Engineering pursue a holistic concept that includes the optimization of microorganisms and the design of new gas bioreactors.

VERSATILE USE The possible applications of hydrogen are manifold. TU Graz Rector Harald Kainz and Alexander Trattner, head of the hydrogen competence centre HyCentA, are also convinced of its value. In October, they jointly advocat- ed higher investments in hydrogen-related research and requested “hydrogen billions” from the Austrian government. “We need hydrogen to be able to realize new forms of energy and to convert our energy systems on a large scale,” summarizes Trattner.

Whether the path to a green future without detours is possible is not yet clear for Viktor Hacker: “At present, there is not yet enough electricity from renewable energy sources to be able to store and use energy in the form of hydrogen on a nationwide basis.” Detours via so-called blue or turquoise hydrogen are con- ceivable. Although hydrogen will continue to be produced from fossil energy sources, the

CO2 will be split off and the emissions will thus be significantly reduced. “This is a very interesting approach and can help to bring important technologies into society. But our goal is of course green hydrogen from 100 per cent renewable energies.” ■

H2GreenTech In order to achieve this goal Hacker and his working group initiated the H2GreenTech project in 2020, which aims to promote cross-border cooperation in hydrogen research between Slovenia and Austria and between science and industry.

More about the H2GreenTech project. GLOBAL CHALLENGES TU Graz research 2020-2/#24 RELEVANCE OF HYDROGEN FOR THE FUTURE

Alexander Trattner, HyCentA Source: HyCentA Research GmbH, Fotokuchl e.U.

The economic, ecological, social and health consequences of climate change and environmental pollution pose a serious threat to our quality of life. A sustainable solution is offered by the energy revolution with the transformation of our fossil energy system into renewable energy sources such as green electricity and green hydrogen. First of all, the systematic and extensive expansion of renewable power generation from sun, wind and water is necessary. This expansion guarantees security of supply with local added value and improvement of the quality of life through zero emissions. For buffering fluctuating electricity supply and as a storage medium, green hydrogen is produced by electrolysis of water (“power to hydrogen”), especially in case of surpluses. Hydrogen may be stored and distributed indefinitely in con- tainers, underground storage facilities or in the (natural) gas network. Green electricity and green hydrogen can meet all the requirements of energy technology in mobility, household and industry. As a carbon-free energy carrier, hydrogen enables a closed material cycle with zero emissions through- out. Furthermore, this offers the economic opportunity for innovative know-how and technological leadership. All in all, hydrogen technology proves to be the appropriate zero-emission technology for Europe and above all for Austria, as the existing know- how, production technologies, industrial and economic sectors as well as the available resources offer ideal conditions for this. Hydrogen technologies are seen as an important building block for achieving the goal of “climate neutrality by 2040” in Austria. A national hydrogen strategy has been anchored in the government programme of the Austrian Federal Govern- ment. Research and technology development in the field of green hydrogen are to be promoted especially for the economic and transport sectors in order to make Austria an innovation leader. Austrian companies, research institutes and universities have long been active in the research and development of hydrogen technologies. Supported by the pioneering work of Karl Kordesch in the 1970s, about 160 researchers are now working in the field at TU Graz and its affiliates. With the HyCentA research centre, Graz University of Technology has thus become one of the largest research institutions of its kind in Europe. The further expansion of the research infrastructures at HyCentA and TU Graz should further reinforce the power of the research. Now developments must be continued and accelerated, and the results transferred to the market. Training and teaching in this specialist area should also be further promoted. It is very promising for Austria that domestic industry and research consider the exploitation of this potential as a joint project and a number of companies, universities and research institutions are already working on it. ■ PORTRAIT TU Graz research Physics 2020-2/#24 Rainbow- Coloured Combs and Sunlight After only a few months at Graz University of Technology, Birgitta Schultze-Bernhardt has already brought two renowned research grants to Graz: an ERC Starting Grant and the FWF START Prize. With these in her pocket, Schultze-Bernhardt wants to generate more (UV) light at the Institute of Experimental Physics at Graz University of Technology.

Birgit Baustädter

Birgitta Schultze-Bernhardt. Source: Lunghammer – TU Graz

The sky in front of the wall-sized window is the colour of fresh concrete. Today, sunrays find no gap in the cloud cover. It is more pleasant inside, in Birgitta Schultze-Bernhardt’s office. There is water from coffee cups and warm ceiling light. The fact that the cloudy sky swallows the ultraviolet sunrays does not bother the physicist. After all, in future she wants to make her own UV rays. UV radiation is very high-energy radiation. When it encounters matter or gases, the interactions are very frequent and very strong and, because it is also emitted by the sun, this makes it particularly relevant for research. Yet it is also difficult because there is currently no laser source that can emit such high-energy light directly. “I was already working on creating a frequency comb for the UV range during my doctorate,” says the researcher. “A frequency comb is a laser ruler, so to speak, by which I can measure radiation with great precision and broad band,” explains Schultze-Bernhardt. For her research she uses a method of converting infrared light into UV light – an unfortunately very inefficient method: a lot of laser power is lost, so it has to be started at a very high level in the first place.

ERC STARTING GRANT AND START PRIZE In two projects, rooted like a tree in the same thematic ground and branching upwards, she wants to create a new approach to UV spectroscopy. The Electronic Fingerprint Spectros- copy (ELFIS) project was awarded the FWF’s START prize in spring and focuses on the lower UV range. In the summer, the researcher was awarded an ERC Starting Grant from the Eu- ropean Research Council, which now allows her to devote additional attention to the high- energy UV range. “With these funds I can establish a special laser source and two high-power amplifiers in Graz,” she says, looking forward to the years of research ahead of her. The results of her work are intended, on the one hand, to improve precision spectroscopy and, on the other, to be used in applied research, for example in atmospheric research: “We could use them to investigate how the sun’s UV light affects the gases in the Earth’s atmosphere and thus, for example, find out the exact conditions under which these gas molecules react to form new molecules or simply decompose,” she explains, adding, “We physicists always want to know everything down to the last detail.” PORTRAIT TU Graz research 2020-2/#24 RAINBOWS IN THE BEDROOM And this is what the now 39-year-old has want- ed since her childhood days. Light has fasci- nated the researcher ever since the framed picture of her grandparents first threw a rainbow onto the ceiling of her bedroom. “I used to arrange the photo so that the rainbow looked particularly beautiful,” she says. “I was fasci- nated by simple things like a rainbow, a convex mirror in a driveway or the upside-down reflection in a spoon.” She was already enthusiastic about mathematics when she went to school, and a little later physics was added, too – “because this subject is closer to reality for me.” During her studies, she then decided to study physics, and while working on her diploma thesis with Nobel Prize winner Theodor Hänsch at the Max Planck Institute for Quantum Optics, she began working with frequency combs.

“MANY HAVE TURNED THEIR BACKS ON SCIENCE” “There were only a few women in this course of study. But what did bother me was that during my doctorate, the number of women around me dwindled,” says the mother of two. “Many turned their backs on science because they thought that family and science could not be combined. Whenever possible, she wants to give young women researchers confidence: “Solutions are often found more easily than you think. In my case, it was possible because I combined a passion for my job and my family. A lot has happened in recent years and childcare is now even offered at some conferences.” ■

TU Graz and ERC Grants Currently there are six on-going ERC-grant projects at TU Graz: ELFIS (Birgitta Schultze-Bernhardt, ERC Starting Grant), HelixMold (Gustav Oberdorfer, ERC Starting Grant), POPCRYSTAL (Paolo Fal- caro, ERC Consolidator Grant), SmartCore (Anna Maria Coclite, ERC Starting Grant), SOPHIA (Stefan Mangard, ERC Consolida- tor Grant) and FEEL YOUR REACH (Gernot Müller-Putz, ERC Consolidator Grant). Two ERC-funded projects have just finished: HOMOVIS (Thomas Pock, ERC Starting Grant) and OMICON (Stefan Fre- unberger, ERC Starting Grant).

ERC Grants at TU Graz. INFRASTRUCTURE TU Graz research 2020-2/#24 BATTERY SAFETY CENTER GRAZ

In the Battery Safety Center Graz, TU Graz researchers will in future conduct research into the safety of batteries under the strictest safety precautions. The new center is the result of many years of cooperation with the company AVL. At the heart of the new research centre are three climate chambers for targeted battery ageing and novel mechanical test environments.

The team at the Battery Safety Centre: (from left) Ajla Purkovic, Christian Ellersdorfer, head of Battery Centre Jörg Moser, Stefan Grollitsch, Christian Trummer and Michael Krenn.

The hydraulic test stand “PRESTO 420” enables mechanical load tests at extremely slow load speeds.

The highly dynamic crash system for charged batteries with a length of almost 15 metres was specially developed for the centre. It can reach a maximum speed of 108 km/h.

Batteries can be tested in three identical climate chambers, each with a capacity of 17 cubic metres, at temperatures between minus 40 and plus 90 degrees Celsius during the charging and discharging process. “We can age the batteries in a targeted manner through individually programmable cycles and receive detailed information for analysing battery performance. Under normal conditions, this would be very difficult or even impossible to achieve during test drives,” explains Jörg Moser, head of the centre..

The BATMAN charging unit and the ROBIN clamping device enable batteries to be charged and discharged quickly while si- multaneously recording the temperature and under controlled mechanical pre-stress. The test environment is completed by the RIDDLER battery workstation, where the batteries are disassembled after testing and disposed of properly.

Source: Lunghammer – TU Graz NEWSFLASH TU Graz research 2020-2/#24

Structural Biology

The initiative “Integrative Structural Biology and Biophysics” of the inter-university research cooperation BioTechMed-Graz is a platform for networking researchers in the field of structural biology. Several research groups from Graz University of Technology are already involved in the initiative. You can find more information online on the BioTechMed-Graz website.

CD Labs

In November, two new Christian Doppler laboratories opened at TU Graz. Wolfgang Bösch is head of the CD lab TONI (technology-based design and characterization of electronic components) and Daniel Rettenwander is head of the CD lab for solid state batteries.

Pro2Future

The Pro2Future competence centre has successfully passed the mid-term evaluation by an international jury of experts. Founded in 2017, the centre is located between Graz and Linz and conducts research on production systems of the future. It now employs almost 40 people and cooperates with over 30 academic and 40 industrial partners.

University of Strathclyde

The University of Strathclyde, located in Glas- gow, Scotland, is a new strategic partner university of TU Graz. Central components of the cooperation are the establishment of PhD clusters on the one hand and the initiation of cooperation in teaching and research on the other. The two universities are thematical- ly linked by their own outstanding research centers for pharmaceutical processes and product development.

FET Open Projects

Three research projects in the FET Open funding line at TU Graz will start in autumn with the aim of achieving a revolutionary technological breakthrough. The projects deal with biocatalysts, nanostructures and ultrafast information processing. Of the total volume of 9.4 million euros, just under 1.5 million euros will go to TU Graz.

Foundation Stone

On Campus Inffeldgasse of Graz University of Technology, Bundesimmobiliengesellschaft is constructing two new buildings: the “Data House” and the “SAL building”. The two buildings are being constructed on an 8,800 square metre site in Sandgasse. Together they offer around 20,000 square metres of net space. The investment volume is around 55 million euros. The completion of the buildings is scheduled for July 2022 (Data House) and January 2023 (SAL building).

Houska Prize

With his research project “3D-Nanoprinting”, Harald Plank from the Institute of Electron Mi- croscopy and Nanoanalysis at TU Graz won the Houska Prize in the category University Re- search, which is endowed with 150,000 euros.

ERC Starting Grant

TU Graz physicist Birgitta Schultze-Bernhardt was awarded an ERC Starting Grant for her project Electronic Fingerprint Spectroscopy (ELFIS) and a few months ago was awarded the FWF START Prize.

Honorary Doctorate

Peter the Great St. Petersburg Polytechnic University awarded an honorary doctorate to the Rector of Graz University of Technology, Harald Kainz, in recognition of his contribution to the promotion of the long-standing strategic partnership between the two universities.

THE Subject Ranking 2021

In THE Subject Ranking 2021, published at the end of October, Graz University of Technology was able to improve its ranking in Computer Sciences by one group to 126-150. Graz Univer- sity of Technology has also been ranked in Engi- neering (301-400) and Physical Science (401-500).

FIELDS OF EXPERTISE TU Graz research 2020-2/#24 Fields of Expertise TU Graz‘s research activities are grouped into five strategic, forward-looking Fields of Expertise. Researchers engage in interdisciplinary cooperation and benefit from different approaches and methods, shared resources and international exchange.

Source: istockphoto.com/fotolia.com

ADVANCED MATERIALS SCIENCE

Editorial: Anna Maria Coclite, Christof Sommitsch,Gregor Trimmel

Hydrogen Embrittlement (HE) of Ultra-High-Strength Steel Screws in Service: Still a Development Potential? Andreas Drexler, Hamdi Elsayed, Rudolf Vallant

HUMAN & BIOTECHNOLOGY

Editorial: Gabriele Berg, Gernot Müller-Putz, Bernd Nidetzky

Fast, Accurate and Built to Fit: Computational Protein Design to Address Challenges in Biotechnology Gustav Oberdorfer

INFORMATION, COMMUNICATION & COMPUTING

Editorial: Kay Uwe Römer

The Future of Computing: Learning-Based, Energy-Efficient and Brain-Inspired Robert Legenstein

MOBILITY & PRODUCTION

Editorial: Rudolf Pichler

Research on Next Generation Fuel Cell and Hydrogen Technologies Sebastian Bock

SUSTAINABLE SYSTEMS

Editorial: Urs Leonhard Hirschberg

Enhancing Production of Hydropower Plants and Eco-Friendly Electricity Generation Helmut Benigni

Advanced Human & Materials Biotechnology Science

Fields of Information, Sustainable Expertise Communication & Systems Computing

Mobility & Production

Source: TU Graz

TU Graz has divided its research into five innovative areas: the Fields of Expertise. Researchers in the Fields of Expertise break new ground in basic research. They take part in interdisciplinary cooperation, gain support for outstanding projects, and are based in the region as well as part of international networks. They also develop key technologies for industry and commerce, and perform research in the framework of company shareholdings and partnerships.

ADVANCED MATERIALS SCIENCE Researchers aim to understand the smallest components in the structure and function of new materials, and develop and assemble them in special processes.

HUMAN & BIOTECHNOLOGY Researchers develop devices and methods for medical applications and therapies, or focus on using enzymes and living microorganisms such as bacteria, fungi and yeast in technical applications.

INFORMATION, COMMUNICATION & COMPUTING Researchers face challenges prompted by the information age, for example data security the efficient use of the ever- increasing volume of data.

MOBILITY & PRODUCTION Researchers investigate novel vehicle technologies, new drive systems and more economical product manufacturing processes.

SUSTAINABLE SYSTEMS Scientists focus on the complex challenges presented by a growing population and increasingly scarce natural resources. FIELDS OF EXPERTISE TU Graz research EDITORIAL 2020-2/#24

Source: istockphoto.com ADVANCED MATERIALS SCIENCE Fields of Expertise TU Graz

Anna Maria Coclite, Christof Sommitsch, Gregor Trimmel, Advanced Materials Science Source: Lunghammer – TU Graz

otwithstanding the difficult situation due to the pandemic, the Field of Ex- Npertise Advanced Materials Science held the Advanced Materials Day 2020! This was done in a hybrid form: the posters were physically exposed in the halls of the Physics and the BMT buildings, but were presented and discussed online. 62 posters were regis- tered and for each of them a short video pre- sentation was uploaded. Then, on Sept. 28th, we hosted a Webex poster discussion from 9 am to 5:30 pm, reaching peaks of atten- dance of 70 people, including professors and students. We consider this a great success and thank all the participants one more time. Another important piece of news of the past months was that two projects were awarded the Initial Funding from our Field of Ex- pertise. Initial Funding amounts to a maximum of EUR 10,000 and is aimed at foster- ing the development of competitive proposals. The awardees of the 14th call were Daniel Rettenwander with the project (Electro-) Chemo-Mechanical Effects in Solid-State Batteries and Michael Haas with the project Self-Disinfecting Surfaces Made from Poly- silane-Cellulose Hybrid Materials. We wish them all the best for the future proposal sub- mission and we look forward to the next call.

With respect to the current topic Hydrogen, projects and activities in the FoE are in progress, e.g.: Improvement of Hydrogen- Induced Stress Corrosion Cracking Resist- ance of Ultra-High Strength Steel Screws and Fasteners. This project aims to enable the implementation of hydrogen crack- resistant ultra-high strength steels in automo- bile car body and motor applications by im- proving testing techniques and optimizing heat treatment and microstructure. Influence of Sheet Metal Forming and Cutting on the Resistivity of Advanced High-Strength Steels (AHSS) to Hydrogen Embrittlement. Drawing, bending or cutting introduce zones of severe plastic deformation in sheet metal components. This increases the local hydrogen concentration and changes the microstructure, thus affecting the susceptibility of AHSS to hydrogen embrittlement. The research focus is the development of micro- structurally sensitive hydrogen embrittlement testing procedures, modeling and simulation and hydrogen analytics. FIELDS OF EXPERTISE ADVANCED MATERIALS TU Graz research SCIENCE 2020-2/#24

Source: istockphoto.com

Andreas Drexler, Hamdi Elsayed, Rudolf Vallant: Hydrogen Embrittlement (HE) of Ultra-High- Strength Steel Screws in Service: Still a Development Potential? Hydrogen embrittlement is a major concern for the automotive, construction, and energy sectors. It limits the use of new ultra-high- strength steels, which have huge advantages in reducing raw material consumption, decreasing fuel consumption, and decreasing carbon dioxide emissions. The Institute of Materials Science, Joining and Forming has carried out intensive studies underpinning the harmful effects of hydrogen on steels and to defeat hydrogen’s detrimental effects.

Figure 1: HE cracks in an ultra-high-strength screw steel. Source: TU Graz / IMAT

The global trend in modern lightweight steel construction in the automotive industry increases the need for ultra-high-strength steels (UHSS) with an ultimate tensile strength above 1,500 MPa. Due to the downsizing of steel

structures, CO2 emissions are significantly reduced. However, UHSS are susceptible to HE, which restricts the use of the materials and makes component assessment difficult. Hydrogen can be taken up during steel production, thermal and mechanical processing, coating, or service. Smallest amounts of hydrogen in the microstructure can lead to time-delayed and thus unexpected brittle failure of UHSS screws. The delay in time is particularly crucial because it is difficult to predict the time of critical hydrogen uptake and thus to prevent brittle failure. In the past two years, the Institute of Materi- als Science, Joining and Forming at TU Graz has established an intensive research project in cooperation with voestalpine Wire Rod Aus- tria GmbH in St. Peter-Freienstein, one of Eu- rope’s leading manufacturers of wire rod, and the Centre of Excellence for Electrochemis- try and Surface Technology (CEST) in Wiener Neustadt and Linz, which is one of the Austri- an COMET centers for applied research. The project combines fundamental and applied research to undermine the harmful effect of hydrogen on different microstructural constituents, to design new materials, and to optimize the heat treatment process.

The key development activities in the research project are ▪ the experimental techniques for the microstructural sensitive evaluation of HE resistivity and ▪ the validation of integrated multiscale material models.

M Iath boundaries PAG boundaries

M3C precipitates

MX precipitates

Figure 2: TEM analysis, showing high-resolution microstructural constituents and intensive precipitation [Dománková, 2019]. Source: TU Graz / IMAT

ADVANCED MICROSTRUCTURAL CHARACTERIZATION With proper alloy chemistry and heat treatment, it is possible to reduce HE susceptibility and increase steel strength.

To this end, changes are made to the microstructure concerning the following mechanisms: ▪ beneficial hydrogen trapping by nano-precipitates ▪ grain refinement and ▪ reduction of internal micro-stresses.

Figure 3: In-situ HE testing cell during mechanical loading. Source: TU Graz / Hamdi Elsayed FIELDS OF EXPERTISE ADVANCED MATERIALS TU Graz research SCIENCE 2020-2/#24

Figure 4: Development of a digital twin of the in-situ HE testing cell. 1: Mechanical simulation of the hydrostatic stress field at a screw notch. 2: Diffusion simulation of the hydrogen accumulation in the strained area during mechanical loading. Source: TU Graz / Andreas Drexler

New alloy concepts can be investigated with a new smelting device available at voestalpine for very small melt batches of 45kg. To apply different heat treatments, ovens with oil and salt baths are used. The investigation of the microstructure was applied using many techniques such as LOM, SEM, TEM, XRD, and EBSD, to determine the phases, grain size, sub-grain size, dislocation density, precipitates (size, shape, and chemical composition). In addition, thermal desorption spectroscopy (TDS) was performed to investigate the hydrogen distribution in the microstructure. It was found that hydrogen segregates at the precipitate-matrix interfaces and the dislocations. To optimize the industrial heat treatment process concerning the total precipitate matrix interface area, a MatCalc routine was developed. MatCalc is a thermodynamic software which includes physical principles and is thus capable of handling complex alloy systems and complex heat treatments. For calibration, the necessary parameters are obtained from TEM and TDS analysis.

HYDROGEN EMBRITTLEMENT (HE) TESTING AND SIMULATION To understand the effects of hydrogen accumulation at a notch, a new in-situ HE testing cell was designed and established to evalu- ate the resistivity to HE and stress corrosion cracking. The special feature of this cell is that it allows the precise control of the hydrogen uptake by cathodic polarization or under cor- rosive conditions. A new 250kN electro-mechanical machine currently performs slow strain rate tests (SSRT) and incremental step load tests (ISLT). In addition, a multiphysical finite element model (FEM) of the in-situ testing device was developed and parametrized. This model allows the hydrogen accumulation at the notch during SSRT to be simulated as a function strain rate. It was found that the strained area at the notch can increase local hydrogen concentration up to five times compared to the measured average bulk concentration.

Hamdi Elsayed is a Ph.D. candidate at the Institute of Materials Science, Joining and Forming, focusing on heat-treatments, microstructural characterization, electrochemical and in-situ hydrogen testing of ultra- high-strength steel screws.

Source: Hamdi Elsayed

Andreas Drexler is a university assistant at the Institute of Materials Science, Joining and Forming, focusing on hydrogen-metal interactions, hydrogen embrittlement testing, and simulations.

Source: Andreas Drexler

Rudolf Vallant is a project senior scientist at the Institute of Materials Science, Joining and Forming, working in different metal-joining projects, and is responsible for the corrosion lab development and failure case analyses

Source: Andreas Drexler

In an initial study, the beneficial role of nano- precipitates, which is still under debate in the literature, was evaluated. For this purpose, two different steel alloys were produced: one precipitation rich (containing Cr-Mo and V) and one precipitation free (containing Si and Mn) steel. The former alloy can trap hydrogen and the latter can dissolve it in the microstructure. The investigations always focus on the goal to prevent a movement of atomic hydrogen, especially from corrosion reaction during loading, which can happen in service within the steel microstructure. In a second study, the Quenching and Parti- tioning (Q&P) heat treatment was intensively studied. It is a promising approach for producing a microstructure of martensite (M) and carbon-enriched retained austenite (RA). This complex microstructure imparts high strength to the steel due to the presence of M and high ductility due to the presence of a considerable amount of RA. Because of the high solubility of hydrogen in RA, which acts as a strong trap, the resistance against HE should be increased, but this is not the case. There is a contradiction between results from different investigations in this area. The crucial factor, however, is the RA stability and shape. When the RA is stable and in thin layers around the tempered M, it acts as a barrier and binds the hydrogen, thus prevent- ing it from reaching sensitive phases; in turn, the HE susceptibility should decrease.

OUTLOOK The simultaneous use of microstructural sensitive testing procedures and integrated physically based material models make a contribution to our project by reducing the HE of the high strength screws and fasteners applied in lightweight mobility and the planned

CO2-free energy production. Our understanding of different microstructural constituents regarding the hydrogen distribution and HE contributes sustainably to making a safe use of UHSS possible – and has in this way still a huge development potential. FIELDS OF EXPERTISE TU Graz research EDITORIAL 2020-2/#24

Source: fotolia.com HUMAN & BIOTECHNOLOGY Fields of Expertise TU Graz

Bernd Nidetzky, Gernot Müller-Putz, Gabriele Berg Human & Biotechnology Source: Lunghammer – TU Graz

n this issue, TU Graz research is focusing on topics related to the production, I storage and use of hydrogen. In recent years, hydrogen has emerged as a new focus area at Graz University of Technology. In the field of biotechnology, there are approaches to the technological use of hydrogen as a substrate in microbial production processes. Hydrogen serves special microorganisms as a reducing agent to convert gaseous carbon substrates such as carbon dioxide or carbon monoxide in- to basic chemicals and polymers. This ex- tends the raw material base of modern bio- production to the important group of so- called C1-carbon sources. The microbial utilizability of C1 carbons combines biotechnological processes with chemical processes of using plant biomass (e.g. gasifi- cation of residual and waste materials). The use of C1 carbons in biotechnology hardly competes with food at all and is considered an important part of the sustainable development of a bio-economy of the future. At Graz University of Technology, biotechnology institutes are engaged in integrated process development for the conversion of carbon dioxide and hydrogen into valuable chemical substances. They are doing this in close cooperation with the Austrian Centre of Industrial Biotechnology (acib). Molecular aspects of the development of efficient production strains of microorganisms are combined with modern bioprocess technologies. The interdisciplinary focus on hydrogen at Graz University of Technology offers interesting new cooperation opportunities in the field of biotechnology with institutes of other faculties. In the last round of the Initial Funding Pro- gramme we did not approve any applications. We check applications for plausibility and expected chances within the selected funding programme. We also critically re- view the justification for the requested initial funding. The funds for the Initial Fund- ing Programme are limited by the returns from those third-party funded projects that are assigned to the Field of Expertise Human and Biotechnology. Calls for appointments (Professorship in Computational Medicine, §98; Professorship in Medical Technology, §98, successor to Rudolf Stollberger; Field of Expertise tenure track position) are underway and we will continue to report here. FIELDS OF EXPERTISE HUMAN & TU Graz research BIOTECHNOLOGY 2020-2/#24

Source: fotolia.com

Gustav Oberdorfer: Fast, Accurate and Built to Fit: Computational Protein Design to Address Challenges in Biotechnology Computational design of novel protein structures is a promising tool to make superior biological materials with tailor-made properties, new pharmaceuticals or complex fine chemicals. Over the last two years research in my group focused on developing methods to design and functionalize de novo proteins. Ultimately, we are aiming to be able to routinely and robustly design catalytic or small molecule binding proteins of arbitrary shapes.

Structure prediction De novo design Sequence known, Sequence unknown, structure unknown structure unknown INPT Known amino Deﬁnition of acid sequence architecture/function

TPT Predicted Designed protein backbone 3D structure and sequence

Figure 1: Differences in structure prediction and de novo protein design.

Native proteins

Directed evolution

De novo protein design

Illustrative representation of protein sequence space (grey). Sequence analysis of native proteins shows that tight clusters of protein families can be identified (beige). Source: Gustav Oberdorfer

DE NOVO PROTEIN DESIGN Since the beginning of protein science, it has been clear that proteins have tremendous potential to tackle and solve a variety of biomedical and biotechnological challenges. This is the major reason why they are used widely e.g. as drugs to treat diseases or to generate highly pure chemical compounds, while at the same time producing only minimal amounts of waste and exhibiting an excellent resource balance. In addition, researchers have long shown that the element that gives rise to a protein’s function is its three-dimensional structure – commonly referred to as the structure-function relation- ship – and that all the information needed to adopt this function/structure is stored and encoded in the amino acid sequence of the protein. It was proposed as early as 1963 by Christian Anfinsen that the structure a protein adopts is always the lowest energy state ac- cessible to its amino acid sequence. Remark- ably, with all the given degrees of freedom, even for a small protein, this process would take a prohibitively long time, if all the conformations it could adopt were to be explored (referred to as Levinthal’s paradox or the protein folding problem). This implies, however, that rather than being a set of random trials, the folding trajectory of a protein follows a path. So, if we can come up with ways to simulate and solve this problem efficiently, we should be able to make proteins from scratch according to our needs. De novo protein design is the attempt to use our best understanding of protein biochemistry and biophysics – how proteins fold into their shapes by burial of hydrophobic amino acid residues, or what the typical inter- and intramolecular interactions of amino acids are and how they interact with their environment or targets/substrates – to identify a minimum energy amino acid sequence composition that allows the protein to fold exactly into a desired shape. This is essentially the protein structure prediction problem turned upside down, where a minimum energy structure for a given amino acid sequence is computed. Com- putationally, protein design represents two inter- connected problems: a) How do we score conformations of an amino acid chain and b) How can we sample all its degrees of freedom efficiently? These problems are difficult to solve because sequence space for a typically sized protein (~200 amino acids) is vast (20200) and comprehensive sampling of it remains a challenge even with current computational power. Besides that, the free energy of such a large system is very difficult to compute with absolute accuracy.

Gustav Oberdorfer heads the protein design working group at the Institute of Biochemistry. Their research focuses on the design and engineering of biomolecular structures and their functions – a highly interdisciplinary effort that combines the approaches of computational biology, structural biology, biochemistry and biophysics.

Source: Lunghammer – TU Graz

EXPLORING SEQUENCE SPACE So why try to design a protein, if the odds of success are against the experimenter? With the advent of protein sequence databases and their ever-increasing growth, it has become ev- ident that nature only sampled an infinitesimal small subset of all possible sequences available. Protein design on the contrary allows for the exploration of this “dark matter” of amino acid sequence space (Figure 1). However, the question remaining is: Is it possible to find something new in this pool of unexplored sequences? Given the sheer number of available FIELDS OF EXPERTISE HUMAN & TU Graz research BIOTECHNOLOGY 2020-2/#24

and yet unexplored sequences, it is reasonable to argue that there are thousands of possibilities for designing novel proteins of high stability and arbitrary shape. All of these bare the potential to go beyond classical biochemical approaches and could ultimately provide solutions to biomedical and biotechnological challenges much faster than nature can. Over the last couple of years, tremendous progress has been made in this direction with many novel protein structures designed from scratch. This can be attributed to advances in understanding the fundamental processes underlying protein folding and concomitant improvements in computational methods. In addition, breakthroughs in the field of synthetic DNA manufacturing and the increase in computational power were key aspects for these successes.

FUNCTIONALIZING HELICAL DE NOVO PROTEINS BY DEVIATING FROM IDEAL GEOMETRIES Coiled-coils, a particular group of protein structures, have seen big advances in terms of design. These usually parallel and oligomeric protein assemblies present ideal targets for protein design studies, as they are very regular and follow a repeating sequence, which, in the ca- nonical case, is seven residues long. We could show that it is possible to design genetically encoded, single-chain helix bundle structures with atomic level accuracy. To do so, a novel method that uses equations originally derived by Francis Crick in 1953 which accurately de- scribe the geometries of -helical protein structures was established and used to sample the folding space of helical proteins computationally. The resulting designed proteins were highly idealistic in terms of geometry and showed very high thermodynamic stability (extrapolated

ΔGfold > 60 kcal mol-1), with their experimentally determined structures close to identical to the design models and nearly perfect packing of amino acid side chains between the helices (referred to as “knobs-into-holes”, Figure 2).

Figure 2: Computationally designed helix-helix interface. Through iterative fine sampling of backbone geometries, the computations converged on “ideal” knobs-into-holes packing arrangements, without enforcing sequence motifs to achieve these types of interactions. Source: Gustav Oberdorfer

However, it is obvious that in nature, most protein functional sites sit at the end of structural elements or in unstructured regions and therefore are not placed at positions of ideal protein geometry. It has been shown that this can be a result of selective pressure, where the ances- tral proteins had more regular structural elements, exhibited higher thermodynamic stabili- ties and less dynamics, in comparison to their contemporary versions. This is why it is still un- clear whether idealized protein structures can be functionalized. In order to address this question, research in my group is currently focusing on designing large proteins with topologies not observed in nature. Key elements we hope to find with these studies are whether they exhibit simi- lar rigidity and stability as observed for the small ideal proteins we designed previously (Figure 3).

Figure 3: Side and top view of a computationally designed 20-helix bundle. This topology is completely unknown in nature. Source: Gustav Oberdorfer

Figure 4: Computationally designed 4-helix bundle with a designed binding site for heme B. It can clearly be seen how much the helices had to be bent, in order to accommodate the heme. Source: Gustav Oberdorfer

We are also investigating to what degree we can harness some of the very high thermodynamic stability of our parametrically designed helical bundles to introduce devia- tions from ideal geometry for the gain of catalytic function. To test different levels of devi- ation in helical backbones and to check if this is concomitant with a reduction of thermodynamic stability, functional sites of various sizes have been chosen. In particular my lab is working on metal complexation and cofactor binding (Figure 4). The ability to sample hun- dreds of thousands of potential protein backbones which can be used as starting points to introduce catalytic or ligand binding sites into de novo designed helical proteins is a big advantage over previous attempts in designing functional proteins. Initial results from this research show that there might be a tradeoff between high stability and degree of idealism as far as the protein backbone is concerned; however, many more designs have to be made and characterized before we can draw definite conclusions. In answering these questions though, we hope to pave the way for downstream applications of de novo protein design to tackle environmental, biomedical and biotechnological problems. FIELDS OF EXPERTISE TU Graz research EDITORIAL 2020-2/#24

Source: istockphoto.com INFORMATION, COMMUNICATION & COMPUTING Fields of Expertise TU Graz

Kay Uwe Römer, Information, Communication & Computing Source: Lunghammer – TU Graz

n 2017 the Bavarian state government announced the establishment of a new I Technical University in Nuremberg – about 20 kilometers away from the Uni- versity of Erlangen-Nuremberg, which has traditionally had a strong technical faculty, some say the strongest among all its faculties. The enthusiasm in Erlangen about this new Technical University and future competitor right in front of the door was very limited as reported by different media. Skillfully, the Bavarian state government later also decided to spend a large additional amount of money to also strengthen the University of Erlangen and the Universi- ty of Applied Sciences Erlangen, such that criticism from the latter is rarely heard – at least not in public. The German Science Council – which usually analyses demand and makes recommendations before a new university is established – was not involved in the decision to establish this new university, but it was only after the political decision was made that a concept for the new Technical University was developed under the leadership of Wolfgang A. Herr- mann (retired president of TU Munich) and the Science Council was asked to com- ment on that concept. History seems to be repeating now in Upper Austria (hopefully also the part with the additional money for the existing universities...) In this issue of TU Graz research, Robert Legenstein – who was recently promoted to full professor and head of the Institute of Theoretical Computer Science (congrat- ulations!) – writes about his research. Enjoy reading! INFORMATION, FIELDS OF EXPERTISE COMMUNICATION & TU Graz research COMPUTING 2020-2/#24

Source: istockphoto.com

Robert Legenstein: The Future of Computing: Learning-Based, Energy-Efficient and Brain-Inspired Computer science is at a turning point. Novel Machine Learning (ML) methods are revolutionizing how we think about computation and build computers. ML is believed to provide a path to artificial intelligence. Current ML systems however are energy hungry, which renders them unsuitable for edge applications and contributes to environmental problems. Hence, in the forthcoming transformation, energy-efficiency will play a major role, in which respect there is a lot to learn from the brain.

Robert Legenstein is head of the Institute of Theoretical Computer Science.

Source: Lunghammer – TU Graz

Computers are like empty boxes. They provide possibilities but need to be filled with content to be useful. The way we have done this filling since the advent of computing has only changed recently. An expert writes a computer program which defines the computation performed by the machine. It turned out that this way of filling the box has a severe drawback. It is extremely hard to design programs for many computational problems, in particular those that can be easily solved by humans.

COMPUTER SCIENCE IS AT A TURNING POINT Within the last decade, tremendous progress has been made in this respect by using the Ma- chine Learning (ML) approach. Instead of tell- ing the computer how to exactly process each input in order to determine the desired output, one lets the computer figure it out by itself. For example, data sets exist with millions of images accompanied by labels that define which objects can be seen in each image. An ML algorithm can then figure out how to process input images in order to recognize objects in it. ML has been used to recognize objects or speech, to understand text, to play video games, or to control robots. Virtually all that progress was achieved by deep learning, an ML method based on deep neural networks. These successes have convinced many experts that deep learning provides a path to artificial intelligence.

Figure 1: A spiking neural network learns to play the Atari game Pong. Source: Franz Scherr

Note that ML does not just provide another tool in the toolbox of the computer scientist, it potentially preludes and fuels three fundamental paradigm shifts in computer science. First, a shift from the era of programming to the era of training. Second, a shift from computers as useful tools to computers as intelligent systems. Third, as discussed below, it brings about a complete reworking of the computing hardware we use.

THE ENVIRONMENTAL COSTS OF AI The von-Neumann architecture has been the dominant computing architecture since the early days of computer science. It features a central processing unit (CPU) that communi- cates with a random access memory. However, the fact that during a computation, data has to be shuffled permanently between the CPU and memory through a tiny bus (the von-Neumann bottleneck), renders this architecture inefficient. In particular, it is not suited to the implementation of neural networks used for deep learning. Neural networks are inspired by the architecture of the brain, where simple computational units (neurons) form a complex network. Com- putation in this network is extremely parallel and memory is not separated from computation. Hence, there is no von-Neumann bottleneck. The currently used better option involves graphical processing units (GPUs). While they do provide significant speedups, they are very energy hungry. This is not only a problem for low-energy AI systems in edge devices, it is also becoming an environmental problem. For example, the training of a deep neural network for the GPT-2 model was estimated to emit

about five times as much CO2 as an average American car during its lifetime. INFORMATION, FIELDS OF EXPERTISE COMMUNICATION & TU Graz research COMPUTING 2020-2/#24

Figure 2: Neurons in the brain dynamically form interacting assemblies. Source: Michael G. Müller

ENERGY-EFFICIENT BRAIN-INSPIRED COMPUTATION To build AI systems with reasonable power budgets, novel technology is needed. Here, the brain can serve as a source of inspiration. While having the computing capabilities of a super computer, it consumes only 20 Watts. Many universities and big IT players such as Intel and IBM have thus developd so-called neuromorphic hardware which implements neural networks in a more brain-like manner. Like the brain, it uses spikes as the main communication unit between neurons. Spikes are binary pulses that are communicated only if necessary, hence making the computation much more power efficient. The Institute of Theoretical Computer Sci- ence is at the forefront of this research. It has worked on the foundations for spiking neural networks (SNNs) for more than 20 years, and is now utilizing its expertise in several projects where energy-efficient brain-inspired hardware is developed.

NEUROMORPHIC COMPUTING AND BEYOND Wolfgang Maass is leading a research team at the Institute of Theoretical Computer Science within the European flagship project – the Human Brain Project. The team has developed the machine learning algorithm e-prop (short for eligibility-propagation) for training SNNs. Previous methods achieved too little learning success or required enormous storage space. E-prop now solves this problem by means of a decentralized method copied from the brain. The method approaches the performance of the best-known learning methods for artificial neural networks [1]. For example, we used e-prop to train SNNs to play video games (Fig. 1). The energy-efficiency of neuromorphic systems can be further increased by using novel nano-scale circuit elements [2]. The potential of this approach is investigated in the Chist- era project SMALL (Spiking Memristive Archi- tectures of Learning to Learn), launched this year and coordinated by the Institute of Theo- retical Computer Science. Our team is developing computational paradigms that combine neuromorphic hardware developed by the University of Zurich with memristive devices from partners IBM Zurich research and Uni- versity of Southampton. Another computational substrate with high potential for ultra-fast computing are optical fibres. The Institute of Theoretical Computer Science is participating in the EU FET-Open project ADOPD (adaptive optical dendrites) that has just started. The project will develop ultra-fast computing units based on optical- fibre technologies that function according to the principles of information processing in den- dritic branches of neurons in the brain.

Figure 3: Two question-answering tasks from the bAbI dataset. The neural network with a brain- inspired memory system observes a sequence of up to 320 sentences and has to provide the correct answer to a subsequent question. Source: Thomas Limbacher

But there is much more to learn from the brain. It is known from neuroscientific experiments that neurons in the brain dynamically form assemblies to encode symbolic entities and relations between them. Recently, we have published work that shows how such assemblies could give rise to novel paradigms for symbolic processing in neural networks (Fig. 2) [3, 4]. In addition, the brain uses various memory systems to store information over many time scales. In an FWF project on stochastic assembly computations, we have recently shown how such memory systems can enable neural networks to solve demanding question-answering tasks (Fig. 3) [5]. In summary, the way we think about computation in computer science has remained largely decoupled from the way neuroscientists think about brain function. The ML revolution will change that. Future computing machines will benefit from our knowledge about how the brain is able to generate intelligent behaviour on a tiny energy budget.

[1] G Bellec et al., Nature Communications, 11:3625, 2020. [2] R Legenstein, Nature, 521:37-38, 2015. [3] CH Papadimitriou et al., PNAS, 117(25), 2020. [4] MG Müller et al., eNeuro, 7(3), 2020. [5] T Limbacher and R Legenstein, NeurIPS 2020, accepted. FIELDS OF EXPERTISE TU Graz research EDITORIAL 2020-2/#24

Source: istockphoto.com/fotolia.com MOBILITY & PRODUCTION Fields of Expertise TU Graz

Rudolf Pichler, Mobility & Production Source: Lunghammer – TU Graz

he visible life of mobility and production has been suffering hard times T and we have to acknowledge that the first lockdown in spring turns out not to have been the last one. The short summer in between was immediately used to reopen the laboratories in order to restart the test benches, to reactivate experimental research, to be available again for our students and also to develop new teaching concepts. This is the most wonderful ex- pression of Science, Passion, Technology. Two months ago, the European Commis- sion reinforced the targets for the Europe- an Green Deal and once more Graz Univer- sity of Technology turns out to be on the right path. Its many years of experience with hydrogen concepts in mobility is going to be further intensified. That is why this issue of TU Graz research presents the latest results of the next generation of fuel cells and hydrogen technologies. To ensure that hydrogen technology really thrives in mobility and comparable applications, multi- ple challenges still have to be tackled, such as corrosion issues, finding the right framework conditions for obtaining high-purity hydrogen, finding appropriate carrier systems and so on. In terms of production, last September a milestone in communication standards at Graz University of Technology was able to be achieved. The establishment of a 5G campus private network was finalized at the smartfactory@tugraz. With this instal- lation the research environment for digital production has now got a full playground for working with highest bandwidths and doing tests with upcoming end devices that will help boost production in the fields of productivity, safety and security. At this stage, an open invitation goes out to any interested institution or company to use these facilities for tests or improvements of any kind. Just get in contact with us! This is only one facet of the spirit of all our institutes in this Field of Expertise. And now please enjoy the fascinating article by our colleague Sebastian Bock. FIELDS OF EXPERTISE MOBILITY & TU Graz research PRODUCTION 2020-2/#24

Source: istockphoto.com/fotolia.com

Sebastian Bock: Research on Next Generation Fuel Cell and Hydrogen Technologies Due to current efforts being made in the reduction of greenhouse gas emissions and the associated political focus on hydrogen as a clean energy carrier, methods for sustainable hydrogen production and efficient utilization are again in great demand. In the coming years, fundamental and industry-related research as well as innovative ideas are essential to meet the ambitious goals with regard to efficiency, service life and sustainability of the whole process chain. The fuel cells and hydrogen working group is currently focusing on several approaches to tackle these challenges.

Sebastian Bock recently completed his dissertation on the development of chemical looping technologies for high-purity hydrogen production and is currently a post-doc researcher in the fuel cells and hydrogen working group at the Institute of Chemical Engineering and Environmental Technology. The co-authors Sigrid Wolf and Maximilian Grandi are PhD students in the working group.

EXTENDING DURABILITY OF FUEL CELLS BY REDUCING CARBON CORROSION The development of clean and noiseless propulsion systems for transport applications is crucial to provide a sustainable, internationally connected economic system. Polymer electrolyte fuel cells (PEFCs) are currently seen as a viable option for use as a power supply in elec- tric vehicles (FCEVs), and achieve high driving ranges in combination with fast refueling, as required especially for commercial vehicles. However, the main cost driver for current fuel cell stacks in FCEVs is the membrane electrode assembly (MEA), which still contains the precious metal platinum in the electrode catalyst. Increasing the lifetime and platinum-specific efficiency of the electrodes is therefore crucial for the commercialization. A novel concept for the reduction of precious metals through the selective coating of the carbon support material with polyaniline (PANI), a semi-conductive polymer to increase the catalyst lifetime and activity, was recently demonstrated by the working group. The materials were synthesized in cooperation with international research partners and industry and characterized in the MEA using pur- posefully designed accelerated stress tests to determine performance over long-term operation. In preliminary tests, the lifetime of the catalyst was increased by +14% in comparison to a state-of the-art Pt/C catalyst. Moreover, at single-cell level a significant increase of the platinum-specific activity of +46% was identified, which consequently enables lower platinum loadings in fuel cell stacks. An international patent was successfully grant- ed for this innovative concept, for which additional research is scheduled to further enhance the characteristics and preparation method of the PANI-coating and control the material properties in the MEA.

Figure 1: Chitosan anion exchange membrane doped with graphene oxide for use in direct alkaline alcohol fuels. Source: TU Graz / CEET

NEW CATALYST SYSTEMS FOR THE SUBSTITUTION OF PRECIOUS METALS With the development of advanced catalyst systems, liquid fuels such as ethanol will in future also be used in polymer electrolyte fuel cells for a clean energy supply in mobile and stationary applications. Direct ethanol fuel cells promise advantages regarding high performance, low toxicity and environmental friendliness as well as robustness. However, concerning the significantly lower efficiency compared to other fuel cell technologies, such as PEFCs, the development of enhanced catalysts and membrane development is crucial in order to enhance the performance, durability and costs. In the ongoing project, the performance of the membranes is improved by adding functionalized graphene oxide (GO) to new anion-exchange membrane composite materials by using simple papermaking and coating procedures. The properties of graphene oxide, such as a large surface area, high electrical conductivity, corrosion resistance and the ability to be chemically FIELDS OF EXPERTISE MOBILITY & TU Graz research PRODUCTION 2020-2/#24

Figure 2: Catalyst-coated membrane and SEM recording of the cross-section. Source: TU Graz / Grandi

modified, make the material interesting as a carbon support. Moreover, graphene is very cost- effective compared to other carbon supports as it can be produced from common graphite. Special methods for doping the membranes with GO are proposed to further increase the ionic conductivity as well as their chemical, thermal and mechanical stability and reduces the ethanol crossover in the cell. The synthesized and advanced functionalized graphene-based electrode materials are now used for the development of novel membrane electrode assemblies (MEAs), an evaluation of the influence of production parameters and cell design on the performance of MEAs and their final characterization on cell level.

ADVANCED OXYGEN CARRIER FOR THE PRODUCTION OF HIGH-PURITY HYDROGEN Besides research on electrochemical cells, the research group focuses on the development of chemical looping hydrogen, a process for- merly known as the steam iron process. In this process, the production of high-purity hydrogen is made possible by the ability of iron oxides to act as an oxygen transmitter between its reduction with reductive gases and its re- oxidation by steam. In the latter, the binding of the oxygen atom from water in the iron oxide results in the release of pure hydrogen. The challenge lies, among others, in the optimization of suitable thermally and chemically stable metal oxides. The strongly fluctuating, high process temperatures in the range of 600-1200°C as well as the constant chemical transformation by the incorporation and removal of oxygen in the metal lattice permanently induc- es structural changes and phase transforma- tions. The addition of high-melting inerts such as aluminium oxide, silicon oxide or zirconium oxide is inevitable to preserve the mechanical integrity and oxygen exchange capacity of the metal oxides, in order to obtain long-term stable materials for later industrial applications.

Figure 3: Synthesis of corrosion-resistant carbon supported catalyst for PEM fuel cell electrodes. Source: TU Graz / Grandi

Recent research focused in particular on the improvement of the preparation route for oxygen carriers regarding their mechanical integrity and oxygen capacity. The results indicated that the pre-treatment of the applied materials, often highly prioritized in the literature, had less influence in the long run compared to the chemical composition and the process conditions. Also, the oxidation state of the applied oxygen carrier was identified as significantly influencing the mechanical strength of the porous pelletized materials, which hence determines the preferred oxidation state during storage.

Figure 4: High-purity hydrogen production through chemical looping with pure carbon dioxide and nitrogen sequestration. Source: TU Graz / Bock

The use of other metal oxides as a chemical intermediate to separate oxidizing media from the fuel has also been proposed for other high-temperature processes in the field of fuel conversion, such as biomass combustion for heat generation or synthesis gas production from biomass or hydrocarbon reforming. The advantage of such processes is to easily separate air as the oxidizing media stream from the combustibles by phase separation and hence enable the production of nitrogen-free product gas streams. The research group is currently involved in the Bio-Loop project in cooperation with, among others, BEST Research and TU Wien, to also develop and enhance such oxygen carriers also for future biomass- focused applications.

Figure 5: SEM recording of porous oxygen carrier with aluminum oxide as inert stabilizer. Source: TU Graz / Grandi

As presented in the above-mentioned applications, further fundamental and industry-related research in cutting-edge fuel cells and hydrogen technologies at research organisations is essential to find solutions for future commercial applications. Innovative ideas will hence further strengthen the position of Austrian research and industry in the economically important field of mobility technologies also in combination with future fuel cell technologies. FIELDS OF EXPERTISE TU Graz research EDITORIAL 2020-2/#24

Source: ymgerman – fotolia.com SUSTAINABLE SYSTEMS Fields of Expertise TU Graz

Urs Leonhard Hirschberg, Sustainable Systems Source: Lunghammer – TU Graz

hat we should “treat the crisis as an opportunity” we’ve all heard rather Ttoo often, recently. T It’s true that the pandemic has disrupted our lives in ways that made us inventive. It’s true that the

amount of CO2 emissions we have saved by attending conferences and meetings from the comfort of our laptops is impres- sive. Our members’ meeting in November likewise was held online and did not in- clude the traditional visit to the research infrastructure of a member institute. We’ve learned some lessons and we don’t com- plain. We wear our masks and wash our hands and remain upbeat and optimistic that we’ll get through this “opportunity”! Fortunately there’s not only the crisis, there’s also research as an opportunity. And when it comes to research, many things are proceeding at undiminished speed. This is also true for our Initial Funding Pro- gramme, which has continued as usual. In the 13th round of the programme, held in the spring of 2020, the following four project proposals were deemed eligible for funding by the Field of Expertise leadership. The GeoTendon project was submitted by Franz Tschuchnigg from the Institute of Soil Mechanics, Foundation Engineer- ing and Computational Geotechnics – just this spring he was awarded his habilitation. He wants to improve the measuring basis for non pre-stressed tension elements that are often used for securing sloping terrain along infrastructure routes, thereby making them more resource efficient and more economical. A consortium of academic and industry partners are teaming up for this project to be submitted to the Austrian Research Promotion Agency (FFG). “Climate-fit building” is what Barbara Tru- ger from the Sustainable Construction working group of the Institute of Technol- ogy and Testing of Construction Materi- als wants to study in the small region of Stiefingtal by applying to the FFG funding program City of the Future. The four- stage project includes the building of a pilot project which will subsequently be mon- itored for its sustainability. The goal is to develop consulting guidelines for region- optimized building. Barbara Truger submitted her successful bid even before com- pleting her Master’s studies in May. She will be working alongside a consortium of partners from inside and outside TU Graz. The Graz region is one of the most lightning- active regions not just in Austria, but in Eu- rope. Lukas Schwalt of the Institute of High Voltage Engineering and System Perfor- mance has already worked on new ways to measure and analyze lightning in his dissertation. The FFG Bridge research proposal now put forward will apply artificial intelligence and big data analysis to his highly refined acoustic measurements in order to arrive at an even more complete understanding of this natural phenomenon. The fourth funded project has online and digitally enhanced education, which has achieved particular prominence during the pandemic, as the object of its research. With the Beyond Boundaries project, Armin Stocker from the Institute of Construction and Design Principles along with an interdisciplinary team of partners wants to investigate future methods of online and in-person teaching in architectural education. The proposal will be submitted to the FFG program Laura Bassi 4.0 equal opportunity in digitalization. We wish all applications the best of luck and hope that the resulting projects can one day be presented on these pages, just like the work of Helmut Benigni on the next few pages. FIELDS OF EXPERTISE SUSTAINABLE TU Graz research SYSTEMS 2020-2/#24

Source: ymgerman – fotolia.com

Helmut Benigni: Enhancing Production of Hydropower Plants and Eco-Friendly Electricity Generation The EU’s Green Deal and Austria’s efforts to generate the total demand for electricity in Austria based on renewable energies call for a boost of advancement in the hydropower industry. At present, hydropower is the only technology capable of storing and generating renewable electrical energy on a large scale, on-demand and in large capacities.

Figure 1: Model test of a high specific speed pit turbine, horizontal axis 3-blade runner with the nominal specific speed ns = 1000. Source: HFM / TU Graz

All forms of generation or storage of electrical energy have one thing in common: in a best- case scenario, a power plant should be available everywhere, however not in the vicinity of habitats and invisible to the eyes of the observer, regardless of whether it is hydroelectric power in urban areas, wind parks in alpine regions, pho- tovoltaics in agricultural regions, chimneys of thermal power plants, or nuclear power plants near our country’s borders. Potentially, proximity to residential areas and people, in general, has an unwanted influence on permissible emission levels. It is, therefore, standard practice to devote particular attention to problems such as noise or vibrations, audio- visual impairments or the ecological impact in general. Although these aspects are nowadays essential in the development of power plant sites and their mechanical equipment, the cost issue is especially critical for hydropower. Due to increasing grid requirements, machines are being operated in areas as never before, leading to increasingly innovative cost-optimised projects for hydropower technology. As of the growing integration of other renewable energy sources, the market calls for permanent partial load operation at the lowest possible level, speed variability and increased load change frequency. Research on hydraulic machines and their upgrading is therefore carried out on different levels. Upgrading and repowering machines for this purpose requires virtual and experimental tests, some of which are presented as selected examples in the following.

HIGH SPECIFIC SPEED UNITS In recent years, different machine concepts have been developed to exploit locations with low heads for energy production as well. A closer look at the cost allocation within a low- pressure system reveals that the economic as- pect stands out, as in addition to the construction costs the generator is a fixed cost block. Utilising a standard generator (asynchronous or synchronous) and having a one-step transla- tion results in an enormous cost advantage as direct-coupled low-speed generators are ex- pensive and respective manufacturers are few. The demand for high-performance bulb turbines, which provide high efficiencies and low pressure fluctuation characteristics, has been increasing. However, head losses in draft tubes may induce high energy losses in relation to the low heads under which they are operated. The model test serves as a link for almost all developments in hydraulic machines, on the one hand, to verify numerical developments, and, on the other hand, to subsequently extrapolate the results of model tests to prototypes. For this type of turbine, the central element is the pit, which is mounted on the turbine frame and includes the torque measurement shaft and a bevel gearbox to transfer the shaft power to the generator during the model test (see Figure 1). The hydraulic design has been numerically enhanced, based on an existing start geometry, and a manufactured model has been installed on the 4-quadrant test bench of the institute for an IEC 60193-compliant test. Further investigations within the presented research project, which was funded by the Italian government, included cavitation, pressure and pressure pul- sation measurements directly on the blades in the rotating system, for which the signals were transmitted by radio via a telemetry system, and velocity field measurements in different sec- tions. The results of these measurements were used in particular to compare the CFD results with experimental data. FIELDS OF EXPERTISE SUSTAINABLE TU Graz research SYSTEMS 2020-2/#24

Figure 2: Numerical simulation of downstream fish migration. Source: HFM / TU Graz

FISH FRIENDLY DESIGN – DOWNSTREAM FISH MIGRATION Migrating fish can be injured when passing through turbines in the downstream direction. Although the overall influence on the fish population is still not known, it is undoubtedly linked to the damage potential of the turbines, the stage of maturity and the size of the migrating individuals as well as the number of migrating fish in proportion to the total population. The main damage mechanisms are usually the contact with the turbine blades, and the pressure drop in the turbine as well as shear forces and turbulences. Investigations with live fish in a 5-bladed vertical Kaplan turbine were carried out, and Barotrauma Detection Sensors (BDS) were applied to determine physical parameters during the turbine passages. The numerical flow simulation included the entire turbine to realise transient simulations with a scale-adaptive turbulence model, combined with a par- ticle tracking model to determine the correct flow path of the machine. These trajectories provided the input information based on which the magnitudes of injury mechanisms could be quantified. The lowest pressures could be quantified and localised (Figures 2 and 3). The results and correlations detected can be incor- porated into the development of fish-friendly turbines, where – to date – it has been necessary to rely on the results of experiments which do not represent the conditions prevailing in Central Europe. The investigations are part of a project supported by the Austrian Research Promotion Agency (FFG) and the Austrian Association of Electricity Companies (Österreichs Energie).

Figure 3: Comparison of numerical and experimental results for downstream migration, Nadir pressure. Source: HFM / TU Graz

INCREASING THE ENERGY PRODUCTION BY EMPOWERING A KAPLAN TURBINE Hydropower plants have already proven their long service life with countless plants that have been in operation for more than 100 years. Now- adays, the refurbishment of such plants leads to a maximum annual production with a simultaneous increase in the ecologically necessary residual water. For a 25 MW power plant in Up- per Styria, an improvement of the annual production by 6 GWh could be achieved through a replacement of the runner. Based on the results of the numerical development, the starting point of cavitation could be shifted to the limit of the new operating range. This effect could also be confirmed by a model test (Figure 4).

Figure 4: Model of the turbine unit. Model test according to IEC 60193. Source: HFM / TU Graz FIELDS OF EXPERTISE SUSTAINABLE TU Graz research SYSTEMS 2020-2/#24

Figure 5: Cavitation observation in full load operation. Source: HFM / TU Graz

Taking a look at the point of maximum discharge now, the limit is easy to determine. At slightly lower sigma values, pronounced surface cavitation forms, whereas at plant-specific sigma values a clean blade, free of surface cavitation, is obtained (Figure 5). Single-phase CFD simulation determines the cause of this surface cavitation, which originates from the low pressure in the area of the blade centre, where bubbles are formed and carried to the rear of the blade. Hydropower contributes and will continue to contribute by far the most to the goal of generating 100 % of the electricity demand in Austria from renewable energy sources.

Helmut Benigni studied mechanical engineering at Graz University of Technology, specialisation in numerical simulation, PhD thesis on the optimisation of hydraulic machines. In post-doctoral position responsible for hydraulic machine simulations employing CFD methods, development of different hydraulic designs and machine configurations, test rig and on-site measurement, habilitation in hydraulic fluid machinery. Vice-head of the Institute of Hydraulic Fluid Machinery, Graz University of Technology.

Source: HFM / TU Graz