Scotland's AWS Energy has reported results some 20% better than predicted for its Archimedes Waveswing, a prototype wave energy generator that's been undergoing ocean-based testing at the European Marine Energy Centre (EMEC) in Orkney for the last six months.

The Waveswing is a cylindrical metal buoy that's tethered to a single point on the ocean floor. In operation, it stays beneath the surface and responds to water pressure changes. As a wave passes overhead, the pressure increase pushes down on the top "floater" section of the device, sliding it downward relative to the lower "silo" section, with a rolling seal ensuring no water gets in.

This linear motion in this "telescoping can" compresses the air in the Waveswing device, creating an air spring to push the floater section back up as the wave rolls onward. As the floater moves up and down, it drives a hydraulic motor, which converts the linear motion into rotation, and a regular electrical generator draws power from both the upward and downward strokes.