The TU Delft campus sports an impressive eleven wind tunnel labs, ranging from hypersonic to vertical wind tunnels. The Open Jet Facility (OJF) is the largest and is used to test wind turbines, bikes, cars and even the famous Senz storm umbrella.
The OJF is a closed-circuit tunnel with a 2.85 meter diameter. The wind can have a maximum speed of 35 m/s and blows out of the tunnel into a huge room making it possible to test large objects. Behind the protective glass and steel bars is the control room where PhD candidates Edwin van Solingen of the Netherlands and Sachin Navalkar of India conduct their own experiments.
Their handmade turbine built by technician Kees Slinkman of the TU Delft, is a replica of a larger machine. Van Solingen and Navalkar are working to reduce the cost of wind energy by reducing the loads and resulting vibrations on the turbines which is the main cause of failures. “If you bend a paperclip over and over it will eventually break off,” explains Van Solingen. He is designing a control algorithm that requires only two controllers to dampen vibrations at all load peaks.
“The OJF is not very realistic because of its low turbulence. It's halfway between pure theory and real life,” explains Navalkar. His focus is on an adaptable algorithm that can react to changes in the system itself for example, a change in wind speed.
Both Van Solingen and Navalkar came away from their time in the lab with promising results. With a gap between industry and academic research, their results will hopefully bolster the algorithms to be eventually used in the real world. “The algorithm is more complex, but the turbine can then tune itself by reacting to changes instead of having technicians do it,” says Navalkar. Simple is not always better and more complex ideas coming out of the TU Delft can hopefully bring down costs and improve the wind turbines of the future.