Krummendeich. Where the dyke to the Elbe is not straight but curved. Population: 390. A flat land where wind is part of everyday life. Since summer 2023, the rotor blades of OPUS 1 and 2 have been turning at the WiValdi wind energy research farm. When a rotor blade is vertical, its tip is 150 metres above the ground. What you can't see from a distance: the wind turbines and the measuring masts are equipped with a total of 1500 sensors from the foundation to the tip of the rotor, collecting and recording data around the clock. And if you look closely, you will see that the two wind turbines are arranged one behind the other in the main wind direction – an absolute no-go for commercial turbines, because the rear turbine is in the wind turbulence of the first. Both are intentional, because WiValdi is a research facility, not designed to generate as much electricity as possible but to gain as much scientific knowledge as possible. Lukas Firmhofer, Kevin Gnebner and Julia Menken have all stood 90 metres high on the turbine’s large central nacelle and felt the strong headwind. In a series of three articles, we introduce the people who work at and with the wind farm.
Working inside the rotor blade
Installing sensor technology inside the rotor blade
The wind turbine's rotor blade, which Kevin has equipped with measurement technology, stands about 90 metres above ground.
For certain jobs, Kevin Gnebner, from the Institute of Aeroelasticity, has to shut off his brain – like when he was sitting inside the rotor blades and checking the functionality of the sensors and measurement systems. That's hardly surprising given the staggering 90-metre drop below. "That was probably my most unusual place of work – sometimes hot, sometimes cold, but always dusty and slippery," he says, summing up his assignment at the OPUS 1 and 2 wind turbines, which laid the groundwork for his and others' research. During lunch, he would head out onto the top surface of the nacelle to take in the fresh air and expansive views of the flat landscape around him. However, the rotor blade instrumentation process actually began in Portugal, with Kevin and 30 fellow DLR team members spending five weeks in close proximity to the 'sacred' production halls where the rotor blades were being manufactured. They were constantly on call, as the sensors had to be installed in one 24 hour window during the ongoing production process. "We had never done this on a scale like that before," says the 31-year-old engineer. To ensure everything went as smoothly as possible, the team trained in advance, practising workflows on a model rotor blade they had built themselves.
Working with a data treasure trove
Test turbines for enhancing wind turbine lifespan
The aim is to use the research data to maximise the turbines' effectiveness and lifespan.
During his mechanical engineering degree in energy and process engineering, Kevin specialised in aircraft engines. But he shifted his focus whilst working on his master's dissertation evaluating vibration measurement data from a wind turbine's rotor blades – which he wrote more than four years ago during a placement at the DLR Institute of Aeroelasticity. Today, he is continuing his efforts for the new turbines at the wind energy research farm. His research has one primary goal: "We want to give recommendations on how to better regulate turbines in the future, extend their lifespan and enhance their efficiency." This doesn't just take place in models on a computer but also draws on real measurement data. For over a year now, the sensors have been providing data for his research. Back at the Krummendeich site, they have already added a weight exceeding one metric tonne to the rotor blades for a measurement campaign aimed at calibrating the numerous strain gauges. "Despite bearing over a tonne of additional load , the rotor blades have barely bent at all. In real-life operations, however, larger forces are at play that can cause the blades to deflect by several metres depending on how strong the wind is," he explains.
His data analysis will show how the inflowing wind field affects the differently arranged wind turbines under real load conditions. The second turbine is especially interesting for research purposes as it's positioned in the first turbine's wake and will consequently face particularly complex, turbulent wind conditions. Such set-ups will be necessary as the use of wind energy expands in the future, but further investigation into the impact on turbine performance and lifespan is still needed.
A workplace with a view
Thanks to the numerous sensors installed by the team at the WiValdi wind farm, all researchers have access to current data.
Kevin's experimental work also involves a great deal of administrative effort. All measurement data must be quality-assessed, and all sensors and measurement systems – which operate under challenging conditions such as changes in temperature and the flexibility of the rotor blades – must be monitored in terms of their functionality. Software and algorithms support the engineer in his efforts. Via remote control, he also has direct access to the wind turbines' latest measurement data from his home base at the DLR site in Göttingen. If technical problems arise, he simply switches his office space at the institute for the wind farm in Krummendeich. He's almost gotten used to the fact that he's nearly 90 metres in the air when working inside the rotor blades.
Interdisziplinär und standortübergreifend
Preparations for the measurement campaign
Kevin was involved in setting up the WiValdi wind energy research farm and will also use the data collected in his work.
"I was fresh out of university and thrown straight into the deep end. My manager, who had previously supervised my master's dissertation, had faith in me. Measurement technology, sensors and experimental work were new to me, but with experience comes confidence," says Kevin, who regards his current role as his dream job. "I have a mix of office-based and experimental research." Collaborating across disciplines and locations is part and parcel of wind energy research at DLR, too. Meteorology, for example, was once something he couldn't quite wrap his head around. "By engaging with colleagues, I have also learned a great deal about this specialist subject area. DLR benefits from having all these specialists spread out across the team."
