Reducing noise from wind turbines

In March 2023, the UK Government published its Energy Security Plan. This builds on a consistent set of strategic objectives set out in earlier white papers and strategies to transform the energy system so that it is secure, low-cost and low-carbon. The plan acknowledges that increasing the supply of low-carbon energy is “dependent on enhancing our strengths on wind, solar and nuclear power generation alongside hydrogen production and carbon capture, usage and storage”. This will be delivered, in part, by removing barriers and addressing blockages. 

 

One such barrier to increasing secure, low cost and low carbon energy from onshore wind projects is noise.  Wind turbines create both mechanical and aerodynamic noise, and this can negatively impact nearby residents. Whilst the Government can help unblock the planning process for wind developments, actually reducing noise created by wind turbines at source is something that will clearly be led by industry.  

 

A relatively recent development in wind turbine noise reduction are serrated trailing edges to blades. Recent research conducted in an anechoic wind tunnel has shown that wind turbine blades with serrated trailing edges can exhibit a 3 to 6 dB reduction in mid-frequency to high-frequency wideband noise emissions. Improvements towards the greater end of this range may be difficult to realise outside of the laboratory, but this design concept offers proven blade noise reductions and several manufacturers now offer serrated trailing edges as an option on their turbines. The most recent predictions we have undertaken for Pencloe Wind Farm are based on a turbine model with serrated trailing edges which are around 3dB quieter than the straight edged equivalent across the range of wind speeds that we modelled. Or, put another way, the reduction in noise from serrated trailing edges will provide the equivalent noise benefit as would placing the turbines twice as far away from dwellings (which is rather impractical, as we can’t move the hill the turbines are on, or the dwellings that people live in). 

 

There are several other blade noise technologies that show promise, such as vortex generators which seek to reduce aerodynamic noise by reducing the pressure gradient at the trailing edge of the blade and delaying flow separation. This improved aerodynamic characteristics of the blade should result in lower levels of noise. The addition of closely spaced fibres (like a brush) to a trailing edge has also been demonstrated to reduce trailing edge aerodynamic noise in laboratory experiments. Whilst still being the focus of research, porous trailing edges may in time be another tool that designers can turn to in order to reduce trailing edge aerodynamic noise.

 

What is also becoming increasingly clear is that wind turbine noise is not necessarily a static or permanent impact. Aside from ever changing wind conditions, turbines do not last forever, and with rapid development in both the efficiency and noise performance we are seeing an increase in older wind developments that are being ‘re-powered’ with newer, more powerful and quieter turbines.