Active wind farm control via morphing blade technology

Since the 1970's wind turbine blades have been manufactured using discrete composite blades. These blades are a tried and tested technology, both structurally and aerodynamically. Since the formulation of the blade-element momentum (BEM) theory by Glauert, horizontal wind axis turbines (HAWT) have been optimised in such a way that they are now capable of reaching power coefficients of around 0.5 (based on aerodynamic efficiency), which is quite close the to the Betz-Joukowsky's limit of 0.593 (Porté-Agel et al., 2020).

Though these structures are capable of extracting a lot of energy from the wind, these structures suffer from high cyclic loads and must be reinforced adequately. A major trend in the offshore wind industry is to produce wind turbines with larger rotor diameters. This will inevitably increase the weight of the rotors blades, and gravitational loads will become design drivers.

Additionally, as the blades become longer, they will also deflect more, and thus structural stability becomes of increasing importance.

Even though modern turbines are highly efficient at extracting the power from a freestream airflow, the same cannot be said at a windfarm level. Wind turbine wakes are responsible for significant power losses in wind farms. The so called 'greedy' turbines within the first row of the array extract more energy from the wind.

Leaving downwind wind turbines to suffer from turbulent air, receiving lower wind speeds, and higher fluctuating loads. This not only will produce less AEP but will reduce the life expectancy of the blades.

Wind farm control via yaw or pitch angle actuations has received an increasing amount of attention recently to mitigate wake effects and provide more energy for the whole wind farm. However, due to their limitations in terms of induced unsteady loads and efficacy, they have yet to be implemented commercially. This is why in this project, we propose a new wind farm control concept in which active blade morphing is used to mitigate wakes effects.

Passive and active morphing aerofoil and wings have been an active field of research in the aerospace and aviation industry for several decades (Lachenal et al., 2013). Many of morphing concepts are bio-inspired such as the one based on the common swallow (Nafi et al., 2021). However, there are very limited studies on using morphing technology in wind turbine blades.

The novelty of this projects comes from studying the wake formation of a developed wind-turbine prototype with active morphing blade sections in a wind tunnel environment. Our aim is to assess the aerodynamic performance when changing the geometry of the blade and visualise the wake formation. The formation of wakes produced by morphing blade structures is an unexplored area of research, and we believe that outcomes of this project will develop and mature this new cutting-edge wind farm control technology.

The topic of this project is quite interdisciplinary as it involves novel manufacturing methods and complex aerodynamic studies of the developed smart turbine and its wake region. To ensure the successful completion of this project, we thus pool our resources and expertise in three institutions (Durham, Hull and Sheffield) to provide the expertise and support that the PhD student needs.