Aerodyn Engineering Uses HBK’s High-Precision S9M Force Sensor to Test Innovative Offshore Wind Turbines

The global demand for energy is growing rapidly. Every year, 16,330 billion kilowatt-hours of electrical energy is consumed worldwide, and the number only keeps rising.

Renewable energy sources are especially becoming increasingly important to power generation. The reason behind this is that, to reduce CO2 emissions and limit climate change, technologies that generate power more efficiently and that are more environmentally friendly than, for instance, traditional gas and coal power stations are required. aerodyn engineering develops innovative wind turbines that allow better utilization of wind power. Before deploying these systems, the technology company located in Büdelsdorf, Schleswig-Holstein, Germany performs tests to investigate how their constructions prove themselves under extreme environmental conditions.

These series of complex tests require robust testing and measuring equipment that provides reliable data, even underwater. Experts at aerodyn engineering, therefore, use high-grade sensor technology such as HBK’s high-precision S9M force sensor to test a new offshore wind turbine.

The average seawater temperature off the coast of the Japanese island of Kurahashi is 10 °C. Here, in Hiroshima Bay, aerodyn engineering is currently testing a floating wind turbine that independently aligns itself in the direction of the wind.

Three thin floats keep the structure that has a total weight of three metric tons afloat on water. Two rotor blades that span over 16 meters have been installed on the eight-meter-high tower. "The turbine delivers an output of five kilowatts with good wind conditions. 

However, this is just a model in scale 1:10. The full-size turbine will weigh about 3,000 metric tons and generate up to six megawatts power later, " explains Martin Bode, Senior Chief Engineer at aerodyn engineering.

Six steel cables fixed to six anchoring points at the bottom of the sea are used to stabilize the wind turbine in its position. The swivel joint, where the anchoring cables meet, allows the entire turbine to freely align itself according to the direction of the wind.

It is important for the tests to determine the stress to which the turbine’s anchoring system is subjected. “Whether they are exposed to heavy storms or high waves, the wind turbines anchors need to withstand extremely rough conditions in the long term later. It is therefore essential to our measurements to use extremely robust force transducers that can be used underwater for several months, "says Martin Bode. 

The sensors also need to provide very precise and detailed results to enable dependable data for the full-size turbine to be derived from the model test.

The experts from HBK, the global technology and market leader in test and measurement, have advised aerodyn engineering and presented them with various sensors.

“Our hermetically encapsulated S9M force sensor is the optimal solution for aerodyn engineering’s measurements below the sea surface that take several months. Our products are thoroughly tested. This ensures that every sensor fully meets our and our customers’ quality requirements,“ says Christoph Miks, HBK Sales Engineer.

The S9M force sensor optimally meets the wind power experts’ requirements. The S-shaped force transducer is available with seven different capacities, ranging from 0.5 kN to 50 kN. It measures tensile and compressive forces very precisely and can be used for a wide range of static and dynamic measurement applications; for instance, in test benches, lever-arm torque measurements, and production and monitoring tasks.

"Due to its minimized temperature dependence and the very small effect of parasitic forces, the S9M allows for extremely high precision in the sensor’s lower measurement range, also in extremely harsh environments, regardless of whether force is measured in industrial applications or below the sea surface,” says Christoph Miks, HBK Sales Engineer. 

The S9M offers high accuracy (HBK accuracy class: 0.02); thus, it provides a precision that is unique for a sensor with this design and is also extremely robust. The force sensor is hermetically sealed and is rated with an IP68 degree of protection, i.e., it is suitable for immersion underwater.

“The welded and sealed strain-gauge installation optimally protects the sensitive strain gauges against the ingress of water, also during the long-term measurements performed by aerodyn engineering. Our products are thoroughly tested to ensure that every sensor fully meets our and our customers’ quality requirements,"states Christoph Miks. 

“Our turbines will be exposed to very high wind speeds of up to 25 meters per second, which is a really heavy storm,” explains Martin Bode, “the anchoring cables also need to withstand high waves of up to 17 meters.” Strong waves are likely to occur off the coast of Kurahashi, too, which can subject the anchoring cables to very high tensile loading temporarily. The S9M is extremely accurate, even with high capacities.

Therefore, a sensor with a higher capacity can be used in applications where high overloads are likely to occur. The sensor’s excellent performance guarantees highly precise measurement results.

Besides the S9M force sensor, aerodyn engineering uses additional accessories such as the matching knuckle eyes that are optimally tailored to the sensor’s capacity.

The wind power experts additionally use the U9C miniature load cell to measure the tensile loading of the rotor tower’s three guy ropes.

Due to its high dynamics and robust stainless-steel measuring body, it precisely acquires load changes in the guy ropes over a long period of time.

"We offer a wider range of sensors and measurement electronics for every requirement,” says Christoph Miks. “We provide our customers with technology comprising the complete measurement chain from a single source, ranging from the sensors to the measurement electronics and matching installation accessories.” aerodyn engineering has relied on HBK’s extensive expertise in sensors and testing and measuring technology for several years.

"We need a partner that joins us in breaking new ground and promoting our innovative wind energy concepts,” says Martin Bode, “The HBK experts advise us and provide us with high-grade, dependable technologies that make our prototype test runs more efficient and reliable.

We benefit from HBK’s global presence in our tests worldwide, for instance, when spontaneous measurement missions require rapid deployment.”