Radar-cross-section reduction of wind turbines. part 1.

Abstract

In recent years, increasing deployment of large wind-turbine farms has become an issue of growing concern for the radar community. The large radar cross section (RCS) presented by wind turbines interferes with radar operation, and the Doppler shift caused by blade rotation causes problems identifying and tracking moving targets. Each new wind-turbine farm installation must be carefully evaluated for potential disruption of radar operation for air defense, air traffic control, weather sensing, and other applications. Several approaches currently exist to minimize conflict between wind-turbine farms and radar installations, including procedural adjustroents, radar upgrades, and proper choice of low-impact wind-farm sites, but each has problems with limited effectiveness or prohibitive cost. An alternative approach, heretofore not techoically feasible, is to reduce the RCS of wind turbines to the extent that they can be installed near existing radar installations. This report summarizes efforts to reduce wind-turbine RCS, with a particular emphasis on the blades. The report begins with a survey of the wind-turbine RCS-reduction literature to establish a baseline for comparison. The following topics are then addressed: electromagnetic model development and validation, novel material development, integration into wind-turbine fabrication processes, integrated-absorber design, and wind-turbine RCS modeling. Related topics of interest, including alternative mitigation techoiques (procedural, at-the-radar, etc.), an introduction to RCS and electromagnetic scattering, and RCS-reduction modeling techniques, can be found in a previous report.

Marine Suitability Assessment for Offshore Wind Farms’ Deployment in Thrace, Greece

“…Considering that OWFs may cause disruptions to the signals of military and commercial use radars and other infrastructures, such as airports, it is recommended to place an OWF at a distance greater than 15 km [83]. The maximum distance affected is considered to be 20 km and, due to the placement of the airport, only the study area for fixed-bottom installations is within this radius.…”

“…The electromagnetic interference area between radar signals and an OWF can be calculated using the Fresnel zone [66]. A simplified Equation ( 12) is introduced that aligns with the results of [66,83] and suits the needs of this study. The equation helps determine the approximate value of impacts, which are amplified by the increasing distance.…”

Active Radar Cross Section Reduction of an Object Using Microstrip Antennas

“…However, this method would entail delays in reacting to the interrogating signal in the circuits and digital processing, which might prove to be a disadvantage. Some of the methods described have been used to reduce RCS of wind turbines: Brock and et al (), Naqvi and Ling (), Palmer and Torres (), Pinto et al (), and Raza and Fickenscher (). A comprehensive discussion of existing RCS reduction techniques for phased arrays is provided in H. Singh and Jha (), where the authors mainly focus on the RCS due to the coupling between the array and an incident field (the so‐called antenna mode scattering).…”