Dr Matthew Large holds a cross-section of a wind turbine blade

Researchers in our Materials Physics group have developed a nanomaterial-based coating that, when added to wind turbine blades, will absorb radar waves otherwise deflected by the moving blade tips.  The so-called ‘radar clutter’ caused by the blades can interfere with systems used for air traffic control, weather forecasting and defence, potentially masking incoming challenges.  Solving the issue will not only enhance coastal security, but may increase capacity to generate wind power by releasing currently sensitive sites for development.

A front-page article in The Times (5 January 2025) addressed the threat to security posed by wind farms and described a range of possible solutions, including the use of the coating, which was developed at Sussex as part of a long-term partnership between the Materials Physics group and Advanced Material Development (AMD).

Dr Aline Amorim Graf, Research Fellow with the Materials Physics group and co-lead researcher explains how the coating works: “The coating is integrated into the existing composite material of the blade lay-up.  The nanomaterial-based formula that we developed with AMD bonds with the individual fibres of the material, saturating the layer. We control the properties of each layering sheet we produce by adjusting the composition of the coating so that it will absorb, not reflect, radar energy.” The team at Sussex have been working on the coatings for over 18 months as part of a Government-funded scheme through the Defence and Security Accelerator (DASA).

Dr Matthew Large, Senior Research Fellow and co-lead researcher describes how the project has evolved: “When we started working with wind turbines, the blades were much smaller, but the largest wind turbines being manufactured now have blades up to 107 metres long, that’s the same length as a football pitch!  Radar signals are detectable from around 300 metres above sea level, so when the total blade diameter is over 200 metres and you add the hub height of the tower, the tips of the turbine blades on the largest models deployed offshore, which can rotate at speeds of up to 150mph, will reflect and scatter radar signals.  This really hampers signal stations trying to decipher radar activity.   If the blades are constructed to absorb radar signals, rather than reflect them, the problem is mitigated and the impact of the turbines effectively hidden.”

Although the research grew out of the need to secure coastal defences and navigation systems, there is a further societal impact which the group is keen to highlight: “We know that offshore windfarms are more efficient and have the potential to generate far more power that currently,” continues Dr Large, “but often the locations where they would be most effective are sensitive, because of the issue with radar interference.  By solving this problem, we’re opening up new areas where windfarms could be sited, increasing our capacity to harvest wind energy.”

The UK is aiming to decarbonise our power system and achieve Net Zero by 2050 and offshore wind farms will play a key role in the transition to renewable energy sources. Our long coastline, shallow waters and strong winds are natural assets, and the UK is home to the world’s largest offshore wind farm project at Dogger Bank.

The conditions where windfarms can harvest power are more favourable offshore, e.g. greater efficiency due to faster and more consistent wind speeds, fewer environmental obstacles and less restricted opportunities for scaling up.  Although more expensive to construct and maintain, offshore windfarms typically outperform their onshore counterparts, and projects to secure and exploit this asset as our energy demands grow include floating wind farms and Energy Islands.

As Dr Large explains, the solution proposed by the Materials Physics group has the added advantage of being sustainable: “Our coating is cheap and the production process is efficient. Although the materials we use are grown in the laboratory or mined from the ground, only a very small quantity is needed. We calculate that less than one kilogram of dry solids combined is the total weight required to produce enough of the coating to cover each turbine. Also, these materials may be produced from bio waste in the future, mitigating their environmental impact. Coated turbines do not require any extra maintenance, as the coating is integral to the structure, not superficial—it won’t chip, or become damaged, and will maintain efficacy throughout the typical 10–20-year lifespan of the turbine.”

The group has also demonstrated that their solution is scalable: “We have just produced a batch with coverage equivalent to 500 square metres!” says Dr Amorim Graf. “Integrating the technology into the existing production processes is easy, the treated layer is just added as part of the usual lay-up when the turbine is constructed, there is no extra stage or additional equipment required and we can calculate and produce the coating according to the order, so there’s very little waste.”

For the Materials Physics group, the real win with their coating is that it will hide the undesirable impact of windfarms, while increasing opportunities to reap their potential. As Dr Large says: “We’ve found a way to solve the problem of radar clutter created by wind turbines, with the added benefit that it will enable the expansion of wind power harvesting by opening up sites for development that were previously considered to be too sensitive for security reasons.”

Prof. Alan Dalton, Leader of the Materials Physics group says: “Our researchers have developed a unique portfolio of coatings and paints from carbon-based nanomaterials, and we’ve learned how to formulate and sensitise them to bespoke requirements.  This application for wind turbines is nearing the stage where a prototype, currently under construction, will be deployed in the field and tested. This is where research gets really exciting: we’ll get to see how our technology performs outside of the lab in harsh and even extreme conditions.  Radar clutter is increasingly an issue in sensitive environments around the world. Mitigating its impact on essential systems, while also enabling the expansion of renewable energy sources, is a viable outcome for the work we’ve done developing this coating.”

Read more about Materials Physics, their partnership with AMD and the story in The Times.

Additional resources: BBC - Record year for wind power in 2024

Gov.UK – Energy Trends: UK renewables