Gavin J Poupart
UK DTI Report Number: W/14/00614/00/REP
This study has focused on the development and validation of a computer model that can be used to predict the radar reflection characteristics (Radar Cross Section, which is measured in square metres and is normally presented on a logarithmic scale) of wind turbines and understand the complex interaction between radar energy and turbines. The scope of the model includes:
- The affects of the radar propagation over the terrain between the radar and the wind farm;
- The dynamic radar scattering from the wind turbines;
- The signal processing in the radar;
- Display of results via a simulated radar display.
The model was validated through a full–scale trial, using a QinetiQ mobile radar system to collect data for a single operational wind turbine at Swaffham in Norfolk. The model was then used to perform a detailed sensitivity analysis and to compile a list of the key factors influencing the radar signature of wind turbines.
The following are some of the results generated by the project:
- The design of the tower and nacelle should have the smallest Radar Cross Section (RCS) as possible. The RCS of these components can be effectively reduced though careful shaping and choice of construction materials;
- Large turbines do not necessarily lead to large RCS (i.e. tower height does not greatly affect RCS);
- Blade RCS returns can only be effectively controlled though the use of absorbing materials;
- Spacing of wind turbines within a wind farm needs to be considered in the context of the radar cross range/down range resolutions.
- Spacing the turbines such that only one turbine can appear in any range cell has advantages in identifying the wind farm, filtering out the turbines and in tracking aircraft over the farm area;
- Single wind turbines do not create a significant ‘radar shadow’. Any shadow region is only dark to a distance of a few hundred metres behind the turbine. Beyond this there is some reduction of the radar power, and a time-variation, but these will not prevent detection except possibly for very small targets.