The high wind speeds at sea make offshore wind farms the most reliable sources of renewable energy. What role does the sensor ring, which can be seen in the video, play here?

For the full performance potential of an offshore wind turbine to be exploited, it must of course be intact. Such a turbine consists of four main sections: the rotor section, tower, transition piece with working platform and the foundation structure that anchors the turbine stably to the seabed. Up to now, maintenance of these sections has been carried out by visual inspection. Diving operations are organized for this purpose – weather-dependent and expensive. With the sensor ring, the condition of this foundation structure can be automatically monitored underwater in real time by ultrasound – for example, whether a crack occurs in the weld seam between the transition piece and the foundation structure – and the plant can be operated more economically. This is because permanent monitoring makes it easier to plan repairs and schedule them in the best possible way.

Aggressive salt water, maritime vegetation, strong pressures under water – all these factors affect a steel structure and have certainly posed challenges for the development of the sensor ring?

Definitely. But together with our interdisciplinary team – we are materials scientists, electrical and mechanical engineers, and I myself am a geophysicist – we were able to find a robust solution that can remain permanently in the depths of the sea: Extremely flat piezoceramic disks act as ultrasonic sensors and are protected from seawater penetration by additional lamination. A foundation structure is several meters in diameter. Depending on its circumference, up to 30 of these sensors are integrated into the ring. Data evaluation is then performed by imaging techniques adjusted for environmental factors such as humidity and temperature that affect the signals.

You have tested the ring in the Baltic Sea wind farm Baltic 1. How was that for you?

Exactly, for half a year the ring measured and detected at a depth of 18 meters before we brought it back to the surface for further optimization. The expedition took place in wind force 9 – anchoring the rocking ship in the whipping waves a few kilometers off the almost 70-meter-high giants was precision work for the captain and crew. Precisely because of this, the diving work is a great challenge that sometimes has to be cancelled due to bad weather conditions. This is then already a big disappointment after all the work involved in preparing the trip. But when everything works out like here and you drive back in the evening sunshine, you look back on the disappearing wind farm with satisfaction and look forward to your next visit.

What goal are you pursuing with your development in the next five years?

Personally, I am pleased that we can now generate our energy more ecologically and that we can actively contribute to this with our research. I hope that we can further increase the attractiveness of wind power with intelligent maintenance concepts such as the sensor ring. From a technical point of view, data transmission from the ring to the maintenance station is still an issue that concerns us. At the moment, a ROV, an underwater robot that is supplied with energy from the ship by cable and controlled with high precision by an experienced pilot on deck – probably also a very good computer player – communicates with the ring. The sensor ring transmits its collected data to the robot via WLAN. My vision is a self-sufficient, full-time measurement that can transmit both the results and the energy required wirelessly over long distances directly to the operator.

Read the press release here.

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