August 13, 2015 – Engineers from the University of Sheffield say they have developed a technique for predicting when bearings inside wind turbines will fail, which could make wind energy cheaper by removing the risk of lost production or unplanned maintenance.

Developed by research student Wenqu Chen, the method uses ultrasonic waves to measure the load transmitted through a ball bearing in a wind turbine. The stress on the turbine is recorded, enabling engineers to forecast its remaining service life.

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

The new method is the only way to directly measure the transmitted load through the rolling bearing components, say researchers. 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 significantly smaller than those currently available, insist researchers, making it suitable for smaller turbines. It also also promises a better prediction of the maintenance needed, saving money in servicing.

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