Ultrasound sensors to reduce wind costs

Innovative monitoring technique for bearings in turbines under test in Ireland

A predictive maintenance technique for bearings that uses ultrasound could make wind energy cheaper and more competitive, the engineers behind its development have said.

The technique, developed by researchers at the University of Sheffield, uses a custom-built piezoelectric sensor mounted in the bearing to record the speed of sound through it.

When a bearing inside a wind turbine is subject 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 of these effects change the time of flight of an ultrasound wave through a bearing - measuring the time of flight allows the load to be determined. This data is then used by engineers to predict its remaining service life, which can save money in servicing.

According to the University of Sheffield, the method is the only way to directly measure load transmitted through the rolling bearing components. The sensor is also cheaper and smaller than those currently available, making it suitable for smaller turbines.

Professor Rob Dwyer-Joyce, director of the Leonardo Centre for Tribology at the University of Sheffield said: "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 sensor has been validated in the lab and is currently being tested at the Barnesmore wind farm in Donegal, Ireland by Ricardo. Researchers hope it will be used in the future inside monitoring systems for other turbines.

The technique, which was developed by Mechanical Engineering research student Wenqu Chen, has been published in the journal Proceedings of the Royal Society A.