Bio-inspired unsteady load control to enhance power output and fatigue life of wind and tidal turbines

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This project aims to develop a new blade concept for wind and tidal turbines using porous blades to passively mitigate unsteady loads. It builds on nature-inspired research on the advantages of porosity and flexibility for passive flight control.Unsteady fluid loads on wind and tidal turbines cause fatigue and power fluctuations, increasing the levelised cost of energy (LCOE). Previous work on passive morphing blades shows that they can completely mitigate load fluctuations. However, for resilience and reliable blade, flexibility may be restricted to the trailing edge, limiting mitigation efficacy. To gain additional load mitigation, the trailing edge can be porous, with its porosity controlled passively and in tandem with its deformation. Staggered holes in the top and bottom surfaces of the trailing edge may be brought into alignment as the trailing edge is deflected by increased fluid load. This low inertia, passively controlled trailing edge could react to high frequency fluctuations thereby combining the efficacy of active, low interia control surfaces with the reduced maintenance of passive control. Additionally, unlike existing passive control methods that rely on structural couplings, the trailing edge could be tailored along the full blade span, mitigating unsteady loads down to the root to reduce flow separation and energy losses and create a cleaner wake for downstream turbines - critical for large, compacted farms.This project capitalises on the recently concluded Leverhulme Trust (RPG-2015-255) project on the flight of the dandelion fruit, which demonstrated how the vortical flow structures and the forces on a porous surface can be controlled by porosity, making it possible to stabilise the wake behind a flow immersed body to generate new flow structures that would otherwise be too unstable to exist. This is, in fact, the mechanisms exploited by the dandelion fruit to fly, unpowered for hundreds of kilometres. We hypothesise that a similar principle is also exploited by birds, whose wings are both flexible and porous, to mitigate the effect of gusts. World-leading research groups, such as Spedding at UCLA, are currently investigating the aerodynamics of porous wings for aeronautical applications. This project will combine recent findings on the effects of porosity and flexible blades to develop a new blade concept for wind and tidal turbines.