Bearing design rev revolutionises wave power technology 30 March 2010

Working with engineers from Pelamis wave power, Schaeffler's bearing specialists have enabled what's being hailed as a breakthrough in the design of next generation wave energy converters.

Mike Woods, senior engineer and bearings group leader at Pelamis, says that for its latest 'P2' design to work, the company had to rethink its bearings and seals.

Pelamis' main tube structures are connected by the bearings units, which use Schaeffler bearings with four hydraulic rams at each joint.

"Our biggest challenge has always been how we manage the loads and motions from such an active and constantly variable environment, while extracting as much power as possible," states Woods.

"The forces generated across each joint can be several hundred tonnes, which can present huge problems for the bearings, as they have to take up the reactive forces coming back through the joints," he explains.

The solution was bringing the axes, or joints, together. "But this meant a completely new bearing solution, able to manage combined angles in a single package," says Woods.

And key to that was a new low-friction material, designed and developed by Schaeffler engineers, involving a modified PTFE fabric liner from its Elgoglide family.

That has low friction characteristics that eliminated the problem of 'stick-slip', and allowed the operating envelope of the machine to be extended.

"Now that we have been able to put all the bearings in one place, we have taken a major technological step forward. As well as being a much more efficient bearing mechanism, the new design is self-contained and modular.

"It is a bit like being able to take an engine out of a car in one go. It allows us to improve our inspection procedures and reduce our exposure to technological risk," says Woods.

Brian Tinham

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