On the Power Response of Wind Turbines with Hydrostatic Transmission: An Experimental Study

Decarbonizing electricity generation drives the adoption of renewable energies during the energy transition, with wind energy playing a prominent role. Yet, horizontal axis wind turbines pose challenges due to fluctuating wind speeds that create loads on the structure and drivetrain, leading to direct transmission fluctuations. To tackle these issues, hydrostatic transmission integration for wind energy harvesting has seen remarkable growth. This approach offers adaptable gear ratios, allowing variable rotor angular velocity while maintaining constant generator speed. Also, its modularity permits relocating the generator from the nacelle to the ground, reducing torque fluctuations by up to about 40% under turbulent boundary layers. This streamlining of components also leads to significant cost savings in offshore wind turbines' Levelized Cost of Energy (LCOE). The study aims to address a gap in hydraulic wind turbines by characterizing the power output spectrum Φ_P experimentally. For this, two 3-meter diameter horizontal axis wind turbines were deployed in similar flow conditions, and a sonic anemometer assessed the flow structure and statistics at hub height. Initial analysis indicates hydrostatic transmission can effectively reduce high-frequency fluctuations compared to the current configuration. A fraction of these may reduce fatigue loads on the wind turbine and enhance power quality, thereby advancing renewable energy technology.