Wind Farm Optimisation - An overview of some aerodynamic considerations

Wind Farm Optimisation: An overview of some aerodynamic considerations
Exploiting the UK’s wind resource, the best in Europe, is vital to achieving our net zero goals. This will require the construction of many more wind farms in promising locations, such as the North Sea, with e.g. predictable winds, shallow water, proximity to centres of population etc. However, as we install more and more wind farms into promising locations overcrowding becomes an issue since the wake of one wind farm becomes the inflow to neighbouring farms. It is thus vital to drive up the efficiency of future wind farms in order to combat these diminishing returns. This necessitates new optimisation methods for designing the layouts of the wind farms of the future. Optimising future wind-farm layouts requires the formulation of a merit function to optimise and a means of evaluating it for all proposed farm layouts. Wind turbines produce turbulent wakes and so turbines located within the central part of a wind farm are exposed to the turbulent wakes of upstream machines rather than the oncoming wind. The power that an individual wind turbine can extract depends on its inflow conditions and turbines situated within the wake of an upstream machines may produce as little as 55% of the power of a turbine in isolation. Further, exposure to an unsteady turbulent inflow can expose the components of wind turbines to fatigue damage. In this talk we will discuss the development of a merit function for wind-farm optimisation; it requires that the farm maximises the power production from a given land area but not at the expense of substantial outages due to maintenance, replacing fatigue-damaged turbine-components. This requires a closer examination of the mechanical response of wind turbines to turbulent inflows. Secondly, we need simple, fast-running (preferably analytical) models to propagate the turbulent wakes produced by the turbines within a wind farm in order to evaluate the merit function a sufficient number of times to obtain an optimal layout. This requires us to advance our understanding of the spreading of turbulent wakes out into a turbulent background, produced either by the wake of an upstream turbine or due to the turbulent nature of the atmospheric boundary layer, by the process of entrainment. We must also further our understanding of the dynamics of the wake, including the proclivity of wind-turbine wakes to “meander” as they progress downstream through consideration of the dominant coherent motions embedded within wind-turbine wakes, such as blade-tip vortices or the effect of the tower/nacelle.

Biography:
Oliver Buxton is presently a Reader in experimental fluid mechanics in the Department of Aeronautics at Imperial College London. He joined the same department as a lecturer in 2013 having previously worked as a post-doctoral research fellow in the Department of Aerospace Engineering and Engineering Mechanics at the University of Texas at Austin, U.S.A. 2011 - 2013. Prior to that he graduated with a B.A./M.Eng. from the University of Cambridge in 2007 and a Ph.D. from Imperial College London in 2011 under the supervision of Prof. Bharathram Ganapathisubramani; in fact he was his supervisor’s first Ph.D. student. During his Ph.D. work he won the 2010 ERCOFTAC da Vinci award for his work on fine-scale turbulence in the far field of turbulent mixing layers. His research is primarily experimental, and in particular he makes use of laser diagnostic techniques such as particle image velocimetry (PIV, both two-dimensional and three-dimensional) and planar laser induced fluorescence (PLIF) to interrogate turbulent flow fields, although he has also worked with several different direct numerical simulation (DNS) codes though not as a developer. Recently, he has focused on turbulent entrainment and multi-scale generated turbulence. He is currently an EPSRC fellow seeking to apply his advances in both to the understanding and modelling of turbulent wind-turbine wakes for wind-farm optimisation and also has research interests in Martian aerodynamics, hydrogen-powered aircraft, and cloud microphysics. In terms of service to the community OB is an advisory board member for the U.K. Turbulence Consortium and sits on the Research Alignment Group for the Supergen renewable energy hub. He has previously been a visiting researcher at Laboratoire PRISME at the University of Orléans in France, is a regular collaborator with the Turbulence, Wind-Energy, and Stochastics research group at the University of Oldenburg in Germany, and has delivered an invited lecture series on the application of PIV and PLIF to turbulence research at the Indian Institute of Technology in Kharagpur, West Bengal. He has published over 40 archived journal papers and has supervised/co-supervised 15 Ph.D. students, one of whom was runner up in the U.K. Fluids Network thesis competition in 2019.

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