Qinetiq Limited

Greg Peter Wade Fixter

Christopher Douglas James Spooner

Christopher James Perry

Vincent Savage

Andrew Shaun Treen

Shahid Hussain

Paul Barrie Adams

Stefan Szwarnowski

Richard Bryant

Christopher John Gilmore

Alexandra Frances Paterson

Adrian Simon Thomas Vaughan

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.

Wind turbine having a reduced radar cross section

A wind turbine comprising a support structure and one or more turbine blades is disclosed, that incorporates means 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 means for reducing the RCS, and the lower section does not have the said adaptation. The invention makes use of the realization 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 localized application of e.g. RAM can give good RCS reduction at a lower cost than treating the whole structure.

A thermally emissive apparatus () having an electro-thermal heating element () comprising a layer () of a first material having a first resistivity and a plurality of discrete regions () of a second material having a second resistivity substantially lower than that of the first material in electrical contact with the first material. The plurality of regions () of second material are arranged spatially so as to impart a predetermined effective sheet resistivity to the first layer (). A plurality of heating elements may be used having a common first layer () of first material, wherein the spatial arrangement of the regions () of second material within a first heating element are optionally different to that within a second heating element. In this configuration the first and second heating elements may emit infrared radiation () having different intensities. The apparatus () finds applications as a thermal target and as an electro-thermal ice protection device.

Thermally emissive apparatus

An electrothermal heater mat for anti-icing or de-icing of a helicopter rotor blade or other aerodynamic surface comprises a substrate, such as a flexible polyimide sheet, bearing tracks of a material of selected electrical resistivity, these tracks being formed by printing onto the substrate with a thermosetting ink loaded with electrically conductive (e.g. carbon) particles. Electrical bus bars/terminals for the supply of electrical energy to the resistive tracks may also be printed, using an ink loaded with particles of higher conductivity material such as copper or silver.

Ice protection of aerodynamic surfaces

A method of measuring the reflectivity of a region of an article to electromagnetic radiation, in particular for the characterisation of the radio-frequency (RF) properties of wind turbine blades. The article is arranged in the near-field of a transceiver antenna, which performs both illumination and measurement of reflected radiation from the region of the article undergoing measurement. The method is beneficial in that it can be used with an antenna in close proximity (or in contact) to the article to be measured, for example for use in on site measurement of specific regions of a turbine blade.

Measurement apparatus and method

A wind turbine blade includes a multilayer composite structure including a first reflective layer, and a second layer including a plurality of resistive circuit analog (CA) elements. The CA elements are tuned so as to interact with the first layer to provide absorption of electromagnetic (EM) energy over a desired frequency range. The parameters of the CA elements can be varied to provide for frequency tuning and to maintain absorption at a specific frequency range despite varying layer separation, while at the same time ensuring that the mechanical properties of the CA layer are compatible with integration into the turbine blade.

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Hook, United Kingdom

Greg Peter Wade Fixter