With the further economic development of China, the demand for energy also increases. Satisfying this energy demand with fossil fuels is becoming increasingly undesirable as this harbors environmental and climate risks.
One solution is to use renewable energy sources like wind power, and it has seen rapid growth in China over the past decade. But many wind farms are built in regions with high seismic activity.
In AIP Publishing’s Journal of Renewable and Sustainable Energy, researchers from Changzhou University and Beijing University of Technology present their work examining the dynamic behavior of wind turbines exposed to combined wind-earthquake loads.
The group discovered that wind changes increase or decrease the response amplitude of the wind turbine in the event of weak or strong earthquakes.
“The angle of entry of earthquakes affects the seismic response of wind turbines due to the asymmetry of aerodynamic damping and blade stiffness,” said Xiuli Du, co-author of Beijing University of Technology. “The ground movements caused by wind and earthquakes both induce the vibrations of wind turbines, especially the rotor blades, which changes the aerodynamic load acting on the rotor blades.”
Modern large wind turbines use the technology of variable speed and pitch control, whereby their dynamic behavior is influenced by the controller.
“Consequently, the dynamic response of wind turbines under wind-earthquake excitation shows the coupling effect of aeroservoelasticity – the interactions between the inertial, elastic and aerodynamic forces that occur when an elastic body is exposed to fluid flow,” said Du. “Wind and ground movements are also random vector fields that, in combination, are associated with complex time domain and spatial uncertainties.”
Surprisingly, the researchers found that the wind simultaneously exerts a dynamic load and a dampening effect on the seismic response of wind turbines. They therefore warn that considering only one of these two effects could lead to inaccurate or even wrong conclusions.
“Our work can guide the determination of wind-earthquake combinations for the seismic design of wind turbines and directly aid in the design of wind turbine structures,” said Du.
Wind turbine support towers located in seismically active areas of China usually do not contain redundant supports. So if one fails, it can cause the turbines to collapse.
“During the conversion of wind energy into electricity, wind turbines are in the operating state for most of their service life, so it is important to investigate the dynamic behavior of wind turbines under wind and earthquake loads,” says Du.
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