Forensic investigation undertaken by Ricardo MultiLife, on behalf of wind energy clients, has identified an important similarity in bearing failure mechanisms commonly arising in wind turbine drivetrains. Wear on the inner race of bearings in the inaccessible planetary stages of the gearbox tends to be concentrated over a small arc of some 40°, and can lead to premature failure while the remainder of the race remains unworn.
The Ricardo MultiLife wind turbine bearing system offers the potential to significantly extend bearing life—by in excess of 500% in rig tests carried out to date—irrespective of the root cause of the bearing damage. This is achieved by rotating the race of standard bearings over time, which ensures that the fatigue damage or wear never reaches a critical localized condition during the turbine life. Put simply, the entire 360° circumference of the race is more gradually expended, not just 40° of it.
As a result, unplanned removal and repair of the gearbox, which can be a particularly costly maintenance operation for offshore turbines, can be avoided.
The MultiLife concept was originally designed for retrofit to existing turbines with minimal modification to the gearbox. In recent discussions, suppliers of new gearboxes have sought assurances of 25-year device life to support their extended warranties. A larger-scale version of MultiLife is also applicable to the races of certain direct-drive turbines that suffer damage from sustained lift and gravity loads.
As part of the UK government’s Department of Energy and Climate Change funded OWDIn (Offshore Wind Drivetrain Innovation) project, a MultiLife system has now been installed for live validation trials at the Barnesmore wind farm, a location that is known to experience aggressive wind conditions. The work in which Ricardo is collaborating with ScottishPower Renewables and the Universities of Sheffield and Strathclyde will enable the full potential to be evaluated for the first time in an operating wind farm environment.
“Reliability is key for wind turbines, particularly offshore and bearing failures are a significant cause of wind turbine loss of production, unplanned maintenance, and consequently unnecessarily high cost of energy for wind farm operators, investors and ultimately the consumer,” commented Ricardo global head of clean energy and power generation Paul Jordan.
“The Ricardo MultiLife wind turbine bearing system addresses this issue by offering the prospect of extending bearing life of the turbine even in the presence of conditions that might otherwise lead to premature failure. The installation of MultiLife for the first time on a live, grid connected turbine is a significant step towards increasing reliability and the ultimate goal of bringing down the cost of wind energy,” Jordan said.