Leveraging Unsteady Flows for Enhanced Performance in Wind-Energy Systems

Wind energy is poised to play a considerable role in the global transition to clean-energy technologies within the next few decades. Modern wind turbines, like aircraft and other aerodynamic structures, are typically designed with the assumption that the flows they encounter will be uniform and steady. However, atmospheric flows are highly unsteady, and systems operating within them must contend with gust disturbances that can lead to performance losses and structural damage. Therefore, the next generation of wind-energy systems requires physics-informed design principles that effectively account for and even leverage these unsteady flow phenomena for enhanced power generation, robustness, and operational longevity. Recent theoretical work has suggested that flow unsteadiness in the streamwise direction may enable time-averaged efficiencies that exceed the steady-flow Betz limit on turbine efficiency. Accordingly, the power production of and flow around a periodically surging wind turbine are investigated using experiments and analytical modeling, which suggest that turbines could leverage unsteady streamwise flows for power-production gains of up to 6% over the stationary case. The experimentally validated models clarify the conditions under which turbines in these flow scenarios, such as floating offshore wind turbines, kite-mounted airborne turbines, and traditional ground-fixed turbines in axial gusts, might be able to capitalize on these performance enhancements. Our investigations provide the foundations for future studies at the intersection of wind-energy systems and unsteady atmospheric flows, which will lead to the development of principles and techniques for wind-farm siting, control, and optimization.