Clean Technology 2009
M.R. Kim, A.E. Ankeny
GGB Bearing Technology, US
bearings, composite, wear, friction, wave energy
The Pelamis Wave Energy Converter is an electric power generation system that uses a revolutionary power conversion unit to convert ocean wave energy to electricity. It harnesses the undulating motion of ocean waves by translating the wave force into oscillations at three power-generation joints along the Pelamis unit. The oscillating mechanical motion derived from the waves is converted into hydraulic fluid flow that drives electrical generators. The oscillating motion required a bearing design that supports that motion and provides long bearing wear life with low friction to minimize power losses from sliding friction even under aggressive ocean conditions. The design also required self-lubrication and maintenance-free operation, as well as a high degree of reliability. These factors were all required because of the remote location and limited accessibility of the power generating units in general, and the bearing locations in particular. The optimum bearing type for this application is a composite that utilizes a high strength fiber/resin construction combined with a self-lubricating bearing layer on the inside diameter. The self-lubricating layer consists of a combination of PTFE fibers and other high strength polymeric fibers encapsulated in a graphite-filled epoxy resin. This paper discuss the general design considerations that led to the selection of high strength composite as the bearing of choice, as well as the tribological properties of fiber/resin composites that allow them to serve difficult applications such as wave energy conversion. This discussion of tribological properties will include a comparison with other more classic bearing types such as greased bronze and needle roller bearings.