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.

The Aura CDT will produce offshore wind specialists with a multi-disciplinary perspective, and will equip them with key skills that are essential to meet the future sector challenges. They will be highly employable due to their training being embedded in real-world challenges with the potential to become future leaders. As such, they will drive the UK forward in offshore wind development and manufacturing. They will become ambassadors for cross-disciplinary thinking in renewables and mentors to their colleagues. With its strong industrial partnership, this CDT is ideally placed to produce high impact research papers, patents and spin-outs, with support from the Universities' dedicated business development teams. All of this will contribute to the continued strong growth of the offshore wind sector in the UK, creating more jobs and added value to the UK economy. Recent estimates suggest that, to meet national energy targets, developers need >4,000 offshore wind turbines, worth £120 billion, over the next decade.

Alongside the clear benefits to the economy, this CDT will sustain and enhance the UK as a hub of expertise in this rapidly increasing area. The UK has made crucial commitments to develop low carbon energy by 2050 and this will require an estimated ~£400m UK RDI spend per year by 2032. Whilst the increase in R&D is welcome, this target will be unsustainable without the right people to support the development of alternative technologies. It is estimated that 27,000 skilled jobs, including in research, will need to be generated in the OSW sector. Of these, ~2,000 are estimated to require HE Level 7-8 qualifications. This CDT will directly answer the higher-level leadership skills shortage, enabling the UK to not only meet these targets but lead the way internationally in the renewables revolution.

Industry and policy stakeholders will benefit through-
a) Providing challenges for the students to work through which will result in solutions to pressing and long-term industry challenges
b) Knowledge exchange with the students and the academics
c) New lines of investigation/ revenue/ process improvement
d) Two-way access to skills/ equipment and training
e) A skilled, challenge focused workforce
Society will benefit through-
a) Offshore wind energy that is lower cost, more secure and more environmentally friendly, with a lower impact on precious marine eco-systems.
b) Engineers with new skillsets and perspectives that can understand environmental constraints
c) Skilled workforce who are mindful of the environmental and ethical impact
d) Graduates that understand and value equality, diversity and inclusion

The research projects undertaken by the Aura CDT students will focus on projects with a strong impact. The 6 themes have all been chosen after extensive industrial consultation and engagement that accelerated after the formation of the wider Aura initiative in 2016. The collaborative approach which has shaped this proposal will be continued and enhanced through the life of the CDT to ensure that it remains aligned to industry priorities.

The interdisciplinary nature of the OSW industry means that there are a wide range of stakeholders including large and small companies who are active at different stages of OSW farm development. These industry players will help ensure the training and experience provided in the CDT addresses the range of challenges that the industry faces.