Martin O. L. Hansen is a visiting research scholar at Princeton University’s Andlinger Center for Energy and the Environment and the department of mechanical and aerospace engineering. He is also the Anderson Family Visiting Professor in Energy and the Environment.
Hansen is visiting from the Technical University of Denmark (located in Kongens Lyngby, north of Copenhagen), one of Europe’s top engineering schools.
Hansen is an associate professor at the institution, where he teaches in the wind energy department, DTU Wind Energy. He is the head of studies in the master of science program in the wind energy department, and has written a widely used textbook on wind turbine aerodynamics.
For the spring semester at Princeton, he taught the course ENE 453 / MAE 453: Wind Turbine Aerodynamics and Technology, which covers basic wind turbine technology concepts such as aerodynamics, control, and structural aspects. The course also addressed dynamic aerodynamic loads on wind turbine blades from, e.g., atmospheric turbulence, and the associated dynamic structural response.
In this interview, Hansen talks about his research and the wind turbine industry in Denmark.
Tell me about your background:
I come from a background in classical fluid mechanics, but for the last 20 years, I have been doing research on wind turbines and wind turbine aerodynamics. Aerodynamics have always interested me and by applying this to wind turbines one can at the same time help mitigate the effects of climate change.
What is your research specialization and what are you working on right now?
My specialty is blade and rotor aerodynamics, where the loads and useful torque are created. Blade aerodynamics also include the wake behind the rotor that influences other, downstream wind turbines.
One of my current projects is looking at vortex generators, small devices attached to blades that increase blade aerodynamics. This helps to decrease the cost of energy. With these vortex generators, you can build more slender blades with the same materials of thicker blades, but they can produce the same loads as the wider ones and thus bring down the cost of the blades.
Another project I am working on is looking at vertical axis wind turbines. They have many disadvantages such as that wind closer to the ground has less speed. They are also exposed to fatigue damage – such as when you bend a spoon too many times, it will eventually break. To avoid this event with these machines, you must be able to predict the unsteady aerodynamic loads and consider this in the structural design.
But they also have advantages: They can work with any wind direction. You can locate them off shore on platforms, where wind speed doesn’t decrease so much near the surface. Some people suggest that these wind turbines can be packed more closely together.
Are there concerns with birds when it comes to wind turbines?
There has been some concern that installing these wind farms will change migrating birds’ paths, but biologists have been monitoring them closely. And so far, no alarming reports have emerged, but this possibility must of course be taken seriously.
How big is the wind turbine industry in Denmark?
In Denmark, wind energy produces 40 percent of all electricity. In America, at least in Texas, it’s 10 percent.
Every country, including the U.S., started becoming interested in turbines after the energy crisis in 1973. People started looking for alternatives to fossil fuels.
Denmark was the same. The wind industry grew out of this, and they managed to do it quite well.
Over the years there has been a lot of government support for the wind industry in Denmark, but in the last few years, the industry’s growth has been driven by businesses building large wind farms.