Onshore Wind Renewable Energy
HITEK has been working with an active consortium to produce Safe Passage material in response to a DTI request for industry to respond to radar issues caused by wind turbines.
DTI Project No: TP/5/LOW/6/I/H0543A is for a “Low cost , safety critical, Radar Absorbing Material for wind turbines, nacelles and towers” and has been running successfully for more than 18 months and has produced innovative solutions to the materials and installation issues.
Working with its Technology partner PERA Innovation and the TSB Monitoring team, the Safe Passage consortium have been able to demonstrate excellent innovative solutions.
For those wind farm developers needing an immediate solution, Safe Passage is available using a broad band layered absorber mounted onto the planks. Standard planks are 6 metres by 0,5 metres and are affixed to towers and metal structures using an innovative solution. The panels are fully weatherproofed using a solution in use on Royal Navy Warships and have seen many years service in hostile wind and sea conditions.
Radar modelling is planned to identify the most economical solution to cloaking the towers and nacelles. Contact HITEK directly to get the latest situation with regard to cloaking towers and nacelles. For blades and spinners please see the Blade Runner section.
Where towers and blades have been fully cloaked it can be difficult to see the exact locations of towers on radar. HITEK Electronic Materials are able to supply broad band Luneburg Lens’s covering the relevant radar bands which return a precise radar signature of defined cross sectional area which can be tied to a GPS location thus ensuring accurate locations of the towers on radar.
These Luneburg Lens’s are solid state with no requirement for external power or maintenance and will give 25 years service when mounted on the nacelle roof alongside safety lighting.
An innovative radar absorbing composite structure for wind turbine blades.
Blade Runner aims to develop a new type of Radar Absorbing Material (RAM) for application to wind turbines to reduce the overall radar shadowing and ghost signals created by wind-farms.
Currently wind farms can affect radar due to both the very large ‘Radar Cross Section’ of the wind turbine towers and the Dopler effect caused by the rotating wind turbine blades. Wind turbine blades are manufactured using Glass Reinforced Polymers (GRP) and foamed materials to reduce the radar reflections. However, one of the main problems with wind turbines are the catastrophic failures associated with lightning strikes. Lightning tends to hit at the highest point, which is invariably the tip of the turbine blades. Therefore, to protect against lightning strikes, modern composite blades typically have an external terminal (~20mm diameter) connected to a 50mm2 copper lightning conductor running from the blade tip, through the pitch bearings to Earth. These conductors run along the inside of the blades where they are periodically glued to the inner surface. The presence of these copper conductors leads to the large Doppler radar signals from the blades.
The British Wind Energy Association estimates that more than 25% of wind farm planning applications are opposed by radar operators as a result of the effects of wind turbines on marine navigation and air traffic radar. This problem can be eliminated by covering the towers and blades with radar adsorbing materials. However the current materials solutions are prohibitively expensive and do not give sufficient radar attenuation.
The project will reduce costs for wind power generation projects through the development of novel ‘stealth’ technologies to reduce the overall radar shadowing & ghost signals created by wind-farms. This technology will then be applied to new wind turbine blades to greatly reduce the radar return signal.