Morphing Blades

This project is funded by the Engineering and Physical Sciences Research Council via the grant EP/V009443/1

The project "Morphing Blades: New-Concept Tidal (and Wind) Turbine Blades for Unsteady Load Mitigation" aims to demonstrate, at model-scale, a novel technology to reduce unsteady-loading for tidal (and wind) turbines, improving resilience and reliability and decreasing the levelised cost of energy. The project focuses on demonstrating a new morphing technology on tidal turbines, where there is an urgent unmet need for unsteady load mitigation, and where morphing technology is likely to be more effective because of the higher solid/fluid density ratio. However, the proposed morphing technology is suitable also for wind turbines, an application that is also considered in this project. 

Tidal energy is a promising renewable energy source that can contribute to providing energy security for the UK. The world’s first arrays of tidal turbines have recently been deployed in Scotland, confirming the UK as a world leader in this emerging energy sector. One of the main technical challenges of harvesting energy from tidal currents is the large load fluctuations experienced by the blades. These can result in fatigue failures of the blades and in power fluctuations at the generator, and thus in a lower mean power when load peaks correspond to rated power. The aim of this project is to develop a technology that cancels the unsteady loading at its source, while adding minimal complexity to the turbine, to ensure high resilience and reliability of the overall system. Furthermore, morphing blades might entirely replace active pitch, ensuring high fluid mechanics efficiency while substantually decreasing the system complexity and th costs

Our preliminary studies show that unsteady load fluctuations can be cancelled without affecting the mean load through blades that passively and elastically adapt their camber and angle of attack. We showed that complete cancellation of the torque, or thrust fluctuations is theoretically possible. We provide proof of principle for two practical implementations through physical experiments and computational fluid dynamics simulations. We consider a blade that is rigid near the leading edge and flexible near the trailing edge. We show that the unsteady load mitigation is proportional to the ratio between the length of the flexible and rigid parts of the blade. For example, for a blade section where the flexibility is concentrated in a hinge at 3/4 of the chord, the amplitude of the fluctuations is 3/4 of the original amplitude. Secondly, we consider a solid, rigid blade with a passive pitch mechanism. We show that, for a 1 MW turbine operating in shear flow, more than 80% of the unsteady loading is mitigated.

The project is led by Prof. Ignazio Maria Viola and includes Dr Eddie McCarthy, Dr Yabin Liu, Dr Stefano Gambuzza, Kuba Frankowski, Dr Anna Young (University of Bath), Dr Riccardo Broglia (Centro Nazionale delle Ricerche, Italy), as well as key tidal and wind energy technology companies such as SIMEC Atlantis Energy, Orbital Marine Power, Nova Innovation, Schottel Hydro, ACT Blades and Wood Group. Together with these industrial partners, we aim to investigate the applicability of morphing blades to different tidal technologies, from 70 kW to 2 MW, from 4 m to 20 m diameter and both seabed-mounted and floating turbines with single and multi-rotors. If proven effective for tidal turbines, we would also explore, with our wind energy partners (ACT Blades and Wood Group), whether this technology is suitable to complement or replace some of the existing unsteady load mitigation technology currently adopted by wind turbines. Morphing blades could contribute to reduce fatigue loads, to increase reliability and lifetime yield and hence to reduce the levelised cost of energy. 

Detached eddy simulation of a tidal turbine (with Riccardo Broglia and Antonio Posa)
Detached eddy simulation of a tidal turbine (with Riccardo Broglia and Antonio Posa)