Bobbing for energy

12 Oct 2005 | News
Energy: The Manchester “bobber” is using the power of ocean waves to find a lower-cost route to alternative energy.

The Manchester “bobber” is using the power of ocean waves to find a lower-cost route to alternative energy. Capturing energy from the rise and fall of ocean waves may not be a new concept, but the University of Manchester and its partners have devised a device that remains relatively stationary in the ocean, to make the most of the promising alternative energy source.

The university is now seeking another £10 million or so from venture capitalists and other investors to develop a commercial version of the device, known as the "Manchester Bobber."

The bobbers are 10-metre-diameter, capsule-shaped devices, grouped in grids floating on the sea surface. They could produce more power than offshore wind farms, and do so less expensively. Energy from these farms costs about three times as much as gas and other conventional energy sources. But the bobber should come in cheaper – about the same price as onshore wind turbines, or about double conventional energy costs, said Peter Stansby, professor of hydrodynamics at Manchester University and co-inventor of the device. An array of 25 bobbers could generate about 4 megawatts of energy.

The advance made by Stansby and his team is in stabilising the vertical motion of the float of bobbers by using tethers. In their small-scale model, they hung vertical cables with weights on their ends from a platform on the water’s surface, as well as used horizontal cables above the surface. This is important, as waves can vary greatly depending on the weather, and the bobber grid must be able to withstand harsh wind and wave conditions. The aim now is to mount the bobbers on existing oil and other offshore platforms.

The current bobber is at about one-tenth its intended full-scale size. Keeping the bobber’s components completely above water protects vulnerable mechanical and electrical components as well, and makes them easily accessible for maintenance checks. The bobber can respond to waves coming from any direction without needing to be adjusted. Each bobber also can be repaired individually, so the network of bobbers can continue generating power even if one or more bobbers goes down.

So far the project work by Manchester and its partners, University of Manchester Intellectual Property Ltd. (UMIP), as well as Mowlem and Royal Haskoning, has been funded through the Carbon Trust. UMIP owns the intellectual property. Phase I, which involved building a 1/100th scale model, was funded to the tune of £50,000 by the Carbon Trust and matching funds by the university and other sources. It was completed in January 2005. Phase II, which started recently, received similar funding.

Mowlem and Royal Haskoning are about half finished with developing and costing conceptual designs for a full-scale platform, and should be done by the end of this year, Stansby said. Phase III, which will involve building the full-scale model, testing it in extreme weather conditions offshore and commercializing the bobber, will require about £10 million. It could take a few more years to work out who will run the bobber power grid and to negotiate offshore leases.

A demonstration at the New & Renewable Energy Centre in Blyth, Northumberland, on 19 September drew interest from a couple of interested venture capitalists, one from the UK and one from the US, but neither has yet made a commitment, Stansby said.

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