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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.

The prototype WITT Energy device underwent its initial testing at the University of Exeter.

Readers' comments (15)

  • What a brilliant idea. I hope they can patent and protect the IP and most of all manufacture the device in the UK. I wonder if a smaller version for yachts is practical. Power on longer voyages is always an issue.

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  • Surely if this device was deployed in proximity to a ships hull in motion, the governing wave forces would be from the ships wake. This would mean that any energy generated would be from the driving force of the vessel. In other words the vessel's engine/s would have to produce more power to replace that absorbed by the device.

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  • In response to the above comment, Sean Limbrick, engineering director at Supacat, says: 'Whilst the ship’s wake might be dominant in calm conditions, the motion of the ship in terms of roll, pitch and heave results from the sea surface conditions (that is the waves) and it is this energy which the device will harvest. As a side effect, as some of the energy is absorbed by the devices, the motion of the ship may well be reduced, particularly for smaller vessels.'

  • What proportion of the energy used to drive a ship around will this device capture? 1%? 0.001%? Like wind turbines, I expect, a complete waste of time and effort.

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  • Hydraulic Ram Turbine Dissociators would work better.. a sea saw float would pressurise water inlet through a valve into a tank below the water line.. the uplift of the float would force the water through a turbine with a momentum flywheel generating enough electricity to dissociate the water into hydrogen and oxygen to explosively motivate a ringdrive like a chambered waterwheel with ignition devices.. to further accelerate and incrementally maintain the momentum of the flywheel on the spindle.. to generate more electricity to dissociate more water into stored explosive gases.. the approach could work on a lifecraft.. and provide heating and drinkable hot water.. with light and power for equipment.. all the way across the oceans back to land in heavy seas..

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  • Most large passenger vessels are dynamically stabilised and VLCC type vessels are too big for any rapid pitching or yawing in response to wave movement, making this device useless in such situations, so it must be aimed at the Leisure market. It could be an ideal battery charger in moored boats if it is cheap enough to buy and install. This means keeping it small. Scaling it up is just not economic. There are probably not enough 'all electric' boats to make a slightly larger version viable. The cynic in me could believe this is just another' grant catcher' ploy.

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  • I thought boat stabilisers required energy input to react the motion of the ship to stabilise it. By having a passive device and withdraw energy from it would actually increase the roll of the ship and discomfort of the journey I'd have thought, and possibly increased the risk of capsize to due to greater angles of lean.
    Feels amost as silly as Pavegen but not quite. No-one has suggested a daft idea to trump that one.

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  • What is the point if the engines are driving the ship they are generally driving the generator. Sea based devices all end up on the shore. Just look at the stormes we get. A huge wave can contain thousons of ton of liquid energy and can go in any direction. nothing last very long against it.

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  • Imagine a dynamic soaring device submerged; imagine a somewhat conventional wave machine moving along with the ship. With such ideas in mind, I suppose one could extract wave energy whilst moving; its been done before with the wind...

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  • In my opinion, this is a brilliant yet simple idea, will work in any dynamic conditions and will act as a small stabiliser. Size WILL be scalable. It should get all the encouragement available provided it is made in UK!

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  • This sounds promising. I can't help thinking that there must be a place for good old wind power ( the ultimate renewable ) in the marine mix. With cargo ships slowing down now to save money there must be potential

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