Drones could stop wind turbines icing over

In freezing conditions, the wind turbines that we increasingly rely on for clean energy can seize up: ice forms on the blades, resulting in a rotational imbalance and increased wear. Sometimes, the turbines have to be shut down for several days for repairs.

Researchers at the Fraunhofer Institute in Germany are exploring the use of drones to protect rotor blades against ice, an upgrade on expensive existing methods which require heating mats to be integrated into the blades, or systems to pump warm air into the rotors, or the use of helicopters to spray de-icing agent onto the turbines. 

“Drones that are only used when needed offer a cost-effective alternative,” says Andreas Stake, project manager at Fraunhofer IFAM, part of the team which has been developing drones that can coat the blades with de-icer. To succeed, the drones needed to meet three criteria: first, a durable coating. Second: a lightweight but accurate spraying system. And third: a high payload for each drone.

The researchers on the project, called Turbo, developed a coating made from urea and wax which is environmentally friendly and sticks to the blades well. They then developed equipment to apply the coating, consisting of a small pump which pushes the mixture at pressure through a 0.3mm nozzle, allowing it to be sprayed precisely onto the edges of the blades at wind speeds of up to 35km/h. Hitting the edges accurately is important because this is where the icing process begins, as cold wet air hits the turbine. 

“Our decades of experience in modelling coating processes really helped us out. We were able to draw on this expertise,” said Oliver Tiedje, project manager at Fraunhofer IPA, whose team used fluid dynamics to determine the correct droplet size and required pressure. “However, we did have to adapt the process parameters to the complex geometry of the wind turbines.”

Now the researchers intend to work with industry partners to get their technique ready for widespread adoptions. As well as turbines, it could be used to treat other infrastructure – overhead lines in rail, for instance, or the facades of difficult to reach buildings.