Wind turbine having a reduced radar cross section

Patent metadata

Field	Value
Publication number	US-11053926-B2
Application number	US-201916584703-A
Country	US
Kind code	B2
Filing date	Sep 26, 2019
Priority date	Jul 30, 2013
Publication date	Jul 6, 2021
Grant date	Jul 6, 2021

Abstract

A wind turbine including a support structure and one or more turbine blades is presented, that incorporates ways for reducing the radar cross section (RCS), wherein the support structure is notionally divided into an upper section in the shadow of the blade sweep area, and a lower section beneath the upper section, wherein the upper section is adapted to have the ways for reducing the RCS, and the lower section does not have the adaptation. The invention makes use of the realisation that the blade masking the tower as it rotates (or the blade being masked by the tower if facing away from a radar), contributes significantly to interference to radar systems, and so localised application of e.g. RAM can give good RCS reduction at a lower cost than treating the whole structure.

First claim

The invention claimed is:

1. A wind turbine comprising:
a support structure; and
one or more turbine blades, each of the one or more turbine blades having a tip at an end thereof, the tip being at a lowest point when the turbine blade reaches its nadir upon aligning with the support structure,
wherein the support structure is notionally divided, by the lowest point of the tip of a turbine blade of the one or more turbine blades, into an upper section and a lower section, the upper section including a part of the support structure that overlaps with the turbine blades' sweep area, and the lower section being a remaining part of the support structure below the upper section, wherein a portion spanning from approximately 20° to less than 180° of a circumference of certain cross-sections of the upper section is adapted to have a reduced radar cross section (RCS).

2. The wind turbine as claimed in claim 1 , wherein the portion of the upper section is covered with radiation absorbent material (RAM) and substantially none of the length of the lower section has a reduced cross section (RCS).

3. The wind turbine as claimed in claim 2 , wherein the RAM is adapted to be absorbent at wavelengths transmitted by an associated radar system.

4. The wind turbine as claimed in claim 1 , wherein the portion includes two opposing sections relative to the circumference of the upper section that each span approximately 45°.

5. The wind turbine as claimed in claim 1 , wherein, given a predetermined location of a radar in relation to the support structure, the portion faces the radar and is covered in RAM.

6. The wind turbine as claimed in claim 5 , wherein angular coverage of the portion covered with RAM extends to between approximately 20° to 90° either side of a point on the circumference facing the radar.

7. The wind turbine as claimed in claim 6 , wherein the angular coverage is approximately 45° either side of the point facing the radar.

8. The wind turbine as claimed in claim 5 , wherein a region on the upper side of the support structure opposite to the side facing the radar also has a RAM coating applied thereto.

9. The wind turbine as claimed in claim 1 , wherein the upper section is itself divided into a plurality of sub-sections or sub-regions, wherein a given sub-section or sub-region has a different covering of RAM as compared to another.

10. The wind turbine as claimed in claim 1 , wherein substantially ½ of the upper section has a RAM covering.

11. The wind turbine as claimed in claim 1 , wherein the RAM comprises a plurality of tiles, each comprising a multi-layered circuit analogue structure.

12. The wind turbine as claimed in claim 11 , wherein the tiles have a substrate layer comprising glass fibre.

13. The wind turbine as claimed in claim 1 , wherein the upper section of the support structure is shaped so as to avoid reflection of radio frequency electromagnetic (EM) energy in a direction of interest.

14. A wind turbine comprising:
a support structure; and
one or more turbine blades, each of the one or more turbine blades having a tip at an end thereof, the tip being at a lowest point when the turbine blade reaches its nadir upon aligning with the support structure,
wherein the support structure is notionally divided, by the lowest point of the tip of a turbine blade of the one or more turbine blades, into an upper section and a lower section, the upper section including a part of the support structure that goes into shadow of an illuminating radar as a turbine blade sweeps past the support structure, and the lower section being a remaining part of the support structure below the upper section, wherein a portion spanning from approximately 20° to less than 180° of a circumference of certain cross-sections of the upper section is adapted to have a reduced cross radar section (RCS).

15. The wind turbine as claimed in claim 14 , wherein substantially none of the length of the lower section has a reduced radar cross section (RCS), and the portion of the upper section is covered with radiation absorbent material (RAM).

16. A method of treating a support structure of a wind turbine, the wind turbine including a blade, the blade having a tip at an end thereof, the tip being at a lowest point when the blade reaches its nadir upon aligning with the support structure, the support structure being notionally divided by the lowest point of the tip into an upper section and a lower section, the method comprising:
i) identifying the upper section of the support structure, the upper section being a top part having overlap with a sweep area of the blade of the wind turbine, with a remainder of the support structure below it being the lower section;
ii) identifying a region on a side of the support structure facing a region of interest; and
iii) adapting at least a portion spanning from approximately 20° to less than 180° of a circumference of certain cross-sections of the upper section of the support structure to reduce its radar cross section (RCS), with the portion including a substantial part of the region defined in (ii).

17. The method as claimed in claim 16 , further including:
arranging the lower part of the support structure such that substantially none of the length thereof is adapted to reduce radar cross section (RCS); and
covering the length of the upper section with radiation absorbent material (RAM).

Assignees

• Qinetiq Ltd

Inventors

• Fixter Greg Peter Wade
• Spooner Christopher Douglas James
• Perry Christopher James
• Savage Vincent

Classifications

• Y02E10/72

  Wind turbines with rotation axis in wind direction · CPC title

• F03D80/80 Primary

  Arrangement of components within nacelles or towers · CPC title

• H01Q17/00 Primary

  Devices for absorbing waves radiated from an antenna; Combinations of such devices with active antenna elements or systems · CPC title

• Y02E10/728

  Onshore wind turbines · CPC title

• E04H12/02

  Structures made of specified materials · CPC title