Ladies and gentlemen, dear colleagues and dear friends, I will specifically talk about the role of transdisciplinary collaboration in thermal science to meet such societal challenges. When Professor Kasagi invited me to contribute to this panel, this subject came almost instantaneously into my mind because during the last maybe 8 to 10 years, I worked more and more multidisciplinary, interdisciplinary, and in some cases also even more, so transdisciplinary, and this work goes on. I, of course, made some experiences and I hope I can share some of these experiences with you to stimulate a discussion on the needs, on the advantages, but also on the disadvantages. Before I come to that in detail, let me start with the role of funding, R&D funding in societal challenges from a European perspective and of course also from a German perspective.

This here shows the seven societal challenges defined within the European Framework Program for Research and Innovation, the so called Horizon 2020 program, which is a huge European R&D funding source. If you look to these top-down defined societal challenges, they address the areas of health, food, efficient energy, smart or green transport, climate action, and resource and raw materials efficiency, then Europe in a changing world and also a secure society.

I marked here in red the three out of the seven societal challenges, which I think have a lot to do with thermal sciences. Thermal Sciences addresses specifically energy efficiency, smart and green transport, as well as resource efficiency, etc.

Now let’s look even closer into the energy program of the European Commission Research and Innovation funds. They defined nine energy relevant topics. They are shown here, from solar energy to energy networks and so on – fuel cells, hydrogen – you can read them here, including some horizontal aspects. If you look into this program you can read the following sentence. It says “A challenge-based approach will bring together resources and knowledge across different fields, technologies and disciplines, including social sciences and the humanities.". This means nothing else than that EU Project Funding is based on a top-down approach which asks clearly for transdisciplinary collaboration.

If I look into a smaller world, inside Germany, we basically get our R&D funding either from the government or ministries or the German Science Foundation. In the “German Energiewende", I think this expression is meanwhile even used in English, in the German Energiewende, so the energy transition, we are somewhere in a transition period and we are focusing severe problems at the moment. The government and the ministries defined some goals, and you can read the goals here. They are really challenging. Challenging goals to reduce greenhouse gases, to increase renewable energy targets, and to increase the overall energy efficiency, specifically for example, electricity up to 50%.

Our major research funding agencies for basic research is the German Science Foundation, the DFG. With DFG, it's a little bit different. It is still a funding agency that follows the bottom up approach without defining any priority topics. However, transdisciplinary or interdisciplinary research proposals are specifically welcome and more and more pushed also in the DFG world. That means if we compare government and ministry funding versus German Science Foundation funding, it's basically a top-down approach versus a bottom up approach.

Now let me come to my personal experience with transdisciplinary or interdisciplinary collaboration. I want to mention specifically two things here that occurred during the last years. I was one of the founders and co-directors within the German Excellence Initiative of this so-called research cluster of Smart Interfaces. This was started in 2007 with rather a huge amount of funding, about 6.5 million Euro per year. The funding from the German government will end at the end of this year and then we will shift the cluster into an internal university research cluster, but, of course, not with the generous funding from outside, that means we get some financial support for overhead. In this center, as a co-director and as a researcher, I work together with my discipline, basically mechanical engineering but also with a lot of mathematicians, physicists, chemists and also materials scientists.

The other experience is in 2012, we were successful again within the German Excellence Initiative with the so-called Excellence Graduate School at TU Darmstadt and it's the only Energy Science related graduate school in Germany. It's the “Darmstadt School of Energy Science and Engineering”. This is a transdisciplinary or interdisciplinary school with a master and PhD program. We defined it to educate tomorrow's leading energy engineers and it involves 10 faculties. These faculties are listed here. So it's even a little bit more interdisciplinary, multidisciplinary, or hopefully transdisciplinary and it also includes some of our colleagues from sociology and economics.

With that experience in background, I had some very very positive experience, which I want to share with you. These are basically the following. I understood and learned really a lot about the colleagues about other research methods, trends and possibilities from other disciplines – mathematical optimization, for example, which I didn't really cover before and other things, of course, more material science and others. I started understanding the sometimes quite different thinking and also sometimes different culture from different disciplines and I could clearly see that there is a trend at least that we work towards broader solutions, more efficient system solutions instead of just towards optimum solutions of small subsystems. Summarizing that, first in the enthusiastic part of my collaboration life, I came to the conclusion that transdisciplinary research is mandatory to solve the upcoming energy problems and it makes my life as a researcher much richer, but before I end my talk, I will show you the negative part.

The negative experience was the following – transdisciplinary projects sometimes do not show the usual scientific depth from each disciplinary perspective. If you work in energy for buildings with an architect or maybe with the civil engineer, they probably don't know the second law of thermodynamics and so they sometimes even violate it and probably I violate their laws sometimes vice versa and, therefore, it comes also to misunderstanding between the colleagues.

Also, the evaluation and re-evaluation process of such an interdisciplinary research activity is often extremely difficult. Why? Because the peers come from multiple disciplines. The different disciplines also have their different performance indicators. As a natural scientist, it's good if you have published in “Nature”, as an applied engineer, it's good that you have some patents. So to bring these worlds together in a peer evaluation process is not very easy. Each discipline has, I would say, his specific arrogance. The physics, as an example, typically says, about an engineer : he's not a real scientist, he is only an engineer. And the engineer says about the physicists: he doesn't solve real life problems. And that's not a good start for a transdisciplinary work.

From the negative side only, before I showed you the positive side, my conclusion would be: I should stop pushing myself for transdisciplinary research and proposal writing and concentrate on my narrow expertise, maybe pool-boiling and the success ratio would be much higher in this case, and my life would be easier.

I'm somehow in a dilemma, and probably many of you are somehow in this dilemma. My dilemma is that I think transdisciplinary collaboration is needed to solve societal challenges and it looks straightforward and easy on paper, but when it comes to real life it is sometimes very hard and can be also frustrating.

Now I think we should discuss ideas how we could promote transdisciplinary research and how we could go on. I put some questions marks here. It's no answers. It's only questions. Maybe some specific transdisciplinary sessions in conferences like this, addressing one specific topic from different disciplines, more bottom-up approaches instead of the top-down approach. This is something we should try. We should also learn more about the performance indicators of others.