Engineers from the University of Sheffield have developed a technique to predict when bearings inside wind turbines will fail.

The method, published in the journal Proceedings of the Royal Society A and developed by mechanical engineering research student Wenqu Chen, uses ultrasonic waves to measure the load transmitted through a ball bearing in a wind turbine. The stress on wind turbine is recorded and engineers then can forecast its remaining service life.

When a bearing is subject to a load, its thickness is reduced by a small amount due to elastic deformation, and the speed of sound is affected by the stress level in the material. These effects change the time of flight of an ultrasound wave through a bearing.

The method directly measures the transmitted load through the rolling bearing components. It uses a custom-built piezoelectric sensor mounted in the bearing to measure the time of flight and determine the load. This sensor is less expensive and smaller than currently available, making it suitable for smaller turbines. It can also provide a better prediction of the maintenance needed, saving money in servicing.

Professor Rob Dwyer-Joyce, co-author of the paper and director of the Leonardo Centre for Tribology at the University of Sheffield says, "This technique can be used to prevent unexpected bearing failures, which are a common problem in wind turbines. By removing the risk of a loss of production and the need for unplanned maintenance, it can help to reduce the cost of wind energy and make it much more economically competitive."

The technology has been validated in the lab and is currently being tested at the Barnesmore wind farm in Donegal, Ireland by the company, Ricardo.

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