As the offshore wind sector expands, the trend towards +12 MW turbines is stretching the design margin of the conventional drivetrain components, particularly the main-shaft bearing, a component that has been scaled up from traditional onshore turbines with little industry effort expended on reviewing its current suitability.
Lack of field experience of large size main-shaft bearing will increase the probability of failure without factor in excessive design margin in large offshore wind turbines. Any premature failures will make a significant contribution to the Levelised Cost of Energy (LCoE). With the offshore wind sector under ever-increasing pressure to reduce the LCoE, there is a clear industry requirement for an alternative bearing solution
Currently, rolling-element bearings (REBs) are employed on the main-shaft of a turbine but these inherently suffer from fatigue and have limited lifetimes. Hydrodynamic journal bearings (HJBs) represent an improvement over REBs as their operational contact pressures are significantly lower and they do not suffer from fatigue. In theory, with appropriate lubrication conditions, they have an unlimited service life.
ORE Catapult is using its expertise in the wind turbine bearing area to conduct a feasibility study and demonstration of HJB on the main-shaft of an offshore wind turbine in order to enhance main-shaft-bearing reliability. Based on our in-depth knowledge and experience of offshore wind technology, our team will define the technical specification and functional requirement of HJB, evaluate the test program, conduct test and process test data, and disseminate findings of project.
In addition, the project will apply an ultrasonic based condition monitoring system that provides accurate real-time data on the health of the bearing such that:
The HJB will have a modular design such that repairs, when required, can be performed without the need to dismantle the entire bearing, minimising downtime and the costs associated with extended periods of production loss. Furthermore, economic analysis will be performed aiming to calculate the potential reduction in LCoE associated with mass deployment of HJB technology on the main shaft of a wind turbine.
This new journal bearing technology will support wind industry growth by reducing the commercial risks and loss of energy yield associated with rotor shaft bearing premature failures. The UK’s strong position in the offshore wind energy sector could be further enhanced with better developed domestic wind turbine bearing supply chain. Cross-industry technology transfer could certainly be adapted in this case with some HJB manufacturers in UK successfully applying HJB technology in other sectors such as marine and hydro power generation. Successful demonstration of the HJB technology for the wind turbine main-shaft application as a replacement of the incumbent REBs will potentially open up a new wind turbine bearing market opportunity in the UK supply chain and make a significant contribution to the job creations and the growth of UK economy.