Wave device raises hope of renewable power for ships

British engineers have begun testing a device that could allow ships to harvest energy from the sea by capturing wave movement in any direction.

The Whatever Input to Torsion Transfer device, developed by Martin Wickett at small firm WITT Energy, uses two pendulums connected to a flywheel to generate electricity from movement.

The company, working with Exeter and Plymouth universities and engineering firms A&P Falmouth and Supacat, have built a version of the device for use in water that they hope could be installed in sea craft to generate renewable auxiliary power from the waves.

The WITT Energy device

Supacat’s engineering director, Sean Limbrick, said although the WITT device would be less efficient than a marine turbine that captured movement for a single direction, it would enable energy generation in more difficult environments.

‘The vessel could be travelling in any direction relative to the waves, which have a lot of mess [in their movement], so we’re in a fairly chaotic input environment,’ he told The Engineer.

‘The multiple degrees of freedom allow us, in principle, to harvest those energy inputs even though they are chaotic and coming from all directions.’

The device’s two pendulums are arranged perpendicularly and attached to a shaft that rectifies their two dimensional movements into a single dimension. And because the device can also freely rotate it can also capture movement along a third dimension.

As part of the Technology Strategy Board-funded project, Supacat turned WITT Energy’s prototype into a test model around 450mm x 450mm x 200m in size using commercially available parts, but if it were to be scaled up for commercial use it would require custom-made components, said Limbrick.

The new model has now begun a five-month test programme at Exeter University’s Dynamic Marine Component (DMAC) facility that will assess how the pendulums and flywheel can be tuned and enable the team to improve their mathematical models of how the device works.

They hope to use this information to determine how the device could be adapted for and installed in ocean-going vessels. Limbrick said one possibility might for it to replace ballast in a ship’s keel.

WITT Energy last year won a $100,000 prize for the device from US environmental organisation The Ocean Exchange.