From academic to industrial research: A comparative review of advances in rolling element bearings for wind turbine main shaft

The growing demand for renewable energy has made wind turbines increasingly large and complex. Demand for efficient main bearings optimized to endure dynamic and unpredictable stresses while allowing turbine motion rises even more. Over the years, rolling element bearings have advanced to meet this demand, driven by innovations from industry and academia. This study examined industry-related and academic contributions to the advancement of wind turbine main bearings. Spherical and tapered roller bearings are identified as the basic wind turbine rotor bearings. From the works reviewed, it was found that industry-related contributions on these bearings center on bearing configuration improvements, cage improvements, the development of improved coats, and the design of novel evolutionary variants of the bearings. The SKF was identified as having contributed more to the development of wind turbine rotor bearings with the patenting of two novel bearings: the CARB toroidal bearing and the Nautilus. Scholarly contributions have majored in bearing geometry and profile optimization. Tapered roller bearings were found to have received more research attention than spherical roller bearings. Also, few innovative studies on CARB toroidal bearing, asymmetrical spherical roller bearing, and the Nautilus have been reported. Exclusively theoretical analyses have been mostly used in performance optimizations of the bearings. Only in a few studies did experimental investigations validate theoretical findings, creating potential avenues for experimental studies. Insights from the review indicate that tapered roller bearings or plain bearings could be viable substitute for spherical main shaft bearings, considering their persistent reliability challenges. The authors recommend more exploration of evolutionary bearing optimization techniques, more investigations on bearing lubricants, housing material, cage material, and coating material designs, and increased industry-academic engagement to pave the way for more main bearing innovation.