On Friday, 25 November, he holds his farewell speech at the end of the symposium "The Future of Wind". His last official words as professor at TU Delft. Professor Dr. Gerard van Bussel is one of the founding fathers of scientific education and research in the field of wind energy. Strongly connected to the world's challenges and co-responsible for today's solutions. A livable climate in the future has always been dear to him. 

What is your take on the ambitious plans of Rob Jetten? 

"I come from a generation where only the optimists among us hoped that one day 20% of our electricity needs would come from wind power. Now, Rob Jetten (Minister for Climate and Energy Policy) wants to put 70 gigawatts of wind power offshore by 2050. That’s 35 big coal plants in the North Sea. I would have never thought anyone in such a position would express this ambition.” 

Did you hope though? 

“Yes absolutely, which is why I have been doing research for decades to make wind energy better, more sustainable and more affordable. But the belief in wind energy was not there for a very long time. Not even at TU Delft. We had to fight for that. It certainly didn't happen by itself." 

Where did that drive and belief in the power of wind originate? 

"My wife is the daughter of a millwright. I could often be found there helping him restore old mills. Practical problem solvers we were. He, with his passion for old mills, and I with my love for model airplanes. I enjoyed working with my hands. Together we philosophized about what would be possible with wind and new techniques in the future. Those were great conversations. I was twenty years old at the time." 

"Nice to talk to gas people or civil servants about wind energy. They really don't understand much about it."

What else did you do besides that? 

"I studied applied mathematics in Nijmegen and took a fantastic course there, philosophy of science. A subject concerned with the critical examination of the presuppositions, methods, and results of science. At that time I got my hands on the report of the Club of Rome. This book fascinated me immensely. It was about modeling the limits of the earth, population growth, resources, CO2 production, all kinds of things. I realized that I wanted to further explore this.” 

And then? 

"I started looking for a graduation assignment in applied fluid dynamics and ended up with Theo van Holten of TU Delft (senior lecturer at AE). Theo had an interesting assignment for me; optimizing the efficiency of a new wind turbine motor design. I graduated on this in 1976. Every two weeks I went by train to Delft-Zuid to discuss the progress. Getting off in that awful neighborhood with those towering flats, and then walking to AE's high-rise for a half-hour discussion. Shortly after I graduated, he asked me to come to Delft because he had received a research budget from the first National Research Program on Wind Energy. So a year later I found myself in Delft-Zuid in one of those 17-story flats looking out on other 17-story flats. Oh well, it was the only housing I could get." 

Then your ‘other half’ Gijs van Kuik came into the picture? 

"Yes. I then worked on that project with Gijs van Kuik for several years. A mathematician and a theoretical aerodynamicist. A great combo though, because we were also practical. Together Gijs and I hammered together models for the wind tunnel and helped to build a test turbine. In those days we lugged large drills and thick chains. Using our brains, but also rolling up our sleeves. Everything we came up with, we also had to carry out ourselves. A great time. We were working on this from '77 to '84." 

You were a great team. Why didn't you continue? 

"At AE (Aerospace Engineering, TU Delft) they thought we were this weird little club of wind mill fanatics. They didn't care much about what we did. Gijs and I had hair up to our shoulders and Theo walked around in sandals, smoking his pipe. That didn't really help either. In September 1984 the story ended. Theo was done with the lack of trust and left for the industry. Gijs and I were out on the street and the wind energy group was disbanded." 

"Gijs found a job as a PhD student in Eindhoven and I ended up, through the mediation of Rector Veltman, in the subdepartment of Mathematics and Computer Science at TU Delft. There I could continue my theoretical wind energy research. " 

When did they finally believe in your research? 

There still was research money left for wind energy from the project and Rector Veltman felt that something had to be done with it anyway. We then set up a new interfaculty club: the Institute for Wind Energy. We used the money to build a new test field in Delft, between the nuclear reactor and the A13 motorway, and new people were hired. I became the research coordinator. The test turbine was moved to the new test field, as well as the very first cooperative wind turbine in the Netherlands. Many new designs were researched. For example, in Delft we did the very first experiments with a wind turbine on a monopile foundation, now the standard solution for almost all offshore wind farms. Looking back, we laid the foundation there for a lot of knowledge we have today." 

In 2004, you were reunited with Gijs at Aerospace Engineering. What had changed in the meantime? 

"Wind had become a big industry. There were now wind turbine companies that employed more than 10,000 people. At AE, the switch finally flipped, a more positive attitude emerged toward wind energy. We were finally able to build the wind tunnel we had wanted for so long. This new wind tunnel opened the doors in 2009 and is also widely used commercially. Cyclists, skaters, the Nuna solar cars. Everything fits in, it’s big." 

There is a smile on your face when you talk about the wind tunnel. Feeling proud? 

"With this wind tunnel, many experiments were performed that were also new to aircraft aerodynamicists. For example, the study of three-dimensional flow along rotors with thick profiles. Once we started with knowledge and tools from aircraft aerodynamics, but over the years we developed our own advanced tools. Newly developed aerodynamics integrated with the dynamics of the flexible rotors. That has produced new design tools that are now used to make very large, reliable wind turbines." 

You don't seem to have missed the momentum? 

"I have been lucky enough to get in at the right time. The moment when everything was still to be conceived and developed, and even many people didn't believe in it. Now, I step out and a dream has come true. The technology is mature. Wind turbines have become much bigger than I could ever imagine. There is a wonderfully dynamic and complex story in the development of a 120-meter-long rotor blade. They are really smart structures. Slim, highly flexible, and self-adapting to wind speed variations. Now the question is, how far can we get with this technology? At some point we run into a limit. So in parallel with the current technique, we have to develop new techniques and design tools." 

Gerard van Bussel in 1977

What will a wind turbine look like in 50 years? 

"Not so different, just look at the car, which hasn't changed much in its basic form either in 80 years. In particular, technology will change, making the wind turbine even smarter. For example, the nacelle of a wind turbine will have a lidar, a laser that allows us to 'look ahead' and thus see wind gusts coming. Air is not 100% clean; there are always dust particles in it. The lidar can look 500 to 1000 meters ahead and thus see large wind gusts, but also a flock of birds, coming. With a wind speed of 10 m/s, you gain 50 seconds to anticipate and stop the wind turbine motor. This way you can reduce fatigue effects, increase service life, and avoid bird casualties. But for new applications, such as far away on the oceans, wind energy systems might look very different." 

What will you miss the most about work? 

Working with students. I believe I trained about 600 engineers. Supervised them myself or chaired their thesis committee. I read and commented on all their work. At least 500 students are still working in wind energy. I have always wished for a full-fledged master's degree in wind energy at the faculty. The market is ready for it, but such a program never materialized in Delft. We did have a European master's program (European Wind Energy Master) and a full Offshore Wind minor. I've done a lot on the education side, that's also where much of my passion lies." 

And now? 

"I have a few more PhDs, which, by the way need to get on with, but then it's done. I give advice to start-ups, and courses on energy transition and the role of wind energy in it. It's fun talking to gas people or provincial officials about wind energy. They don't really understand much about it. There is still a lot to explain." 

Gerard studied applied mathematics at Radboud University in Nijmegen and received his PhD from TU Delft on a study of the aerodynamics of wind turbine rotors. 

He was chair holder and section leader of wind energy at TU Delft's Faculty of Aerospace Engineering from 2008 to 2020. He has conducted extensive research on the aerodynamics of wind turbine rotors, maintenance, operation and reliability of offshore wind farms, new wind energy concepts and on the application of wind energy in the built environment. 

In addition to his teaching duties at the Faculty of Aerospace Engineering, he was also active nationally in renewable energy education as part of the 4TU SET master's program, and internationally in the EUREC Master and the EWEM European Wind Energy Master.  

His research interests include experimental and theoretical rotor dynamics, O&M modeling of offshore wind farms, conceptual design of unconventional wind energy systems, and wind energy in the built environment. He specializes in static and dynamic wind loads on wind turbine rotors and other components. 

He was a board member and president of ODE (the Organization for Sustainable Energy), of the Dutch Wind Energy Association NEWIN, of WindEurope, the European Wind Energy Association, of EAWE (the European Wind Academy for Wind Energy), and of NWEA (Dutch Wind Energy Association). He is co-founder and chief editor of Wind Energy Science, the scientific online open access journal of the European Academy EAWE. 

In 2020, with his retirement, he was named an honorary member of the EAWE. He is an advisor to the De Hollandsche Molen Association on mill biotope issues. 

/* */