Energy-harvesting ships are a blast from the past

05 September 2011 | By Ellie Zolfagharifard

Compared with wind and solar energy, people often believe that wave power is a relatively new area in the renewables field. But an 1876 report in The Engineer’s archive reveals a far longer history in harnessing waves to generate power.

An invention by Mr Browne of Kidwelly shows a novel design of ship with air chambers fitted outside the hull. The chambers are open at the bottom and closed at the top except for a pipe connected with an air reservoir placed on board the vessel.

The report said: ’In this connection-pipe there is a valve, which allows the passage of air from the chambers into an air-reservoir [E in the picture below], but which prevents its return. There is also in this connection-pipe a provision for preventing water passing with the air into the air-reservoir, but should water by any chance get into the air-reservoir, it can be drawn off at H.’

It continued: ’The air is forced into these chambers by the rolling of the ship, and the compressed air can be used for pumping… It must be understood that the compression results not from the difference of head within and without the chamber, but from the inertia of the water, which acts almost as an immoveable piston in the air chambers, when the ship rolls suddenly.’

More than 100 years later, Boston University and the Fraunhofer Center for Manufacturing Innovation have come up with a very similar design. Their idea is to send a fleet of wave-powered ships out into the middle of the ocean, where they would drop anchor and start gathering energy from the movement of the surrounding waves.

The 50m-long ships would harvest wave energy using buoys attached to their sides by pivoting arms. While the hull remains relatively stable, the buoys bob up and down on the waves, causing the arms to pivot back and forth and drive a generator. If this is a success, then Mr Browne may have been onto something more significant than his contemporaries first believed.