Bob’s your output

Manchester University has unveiled an innovative wave energy device that uses the ‘bobbing’ effect of water to create power.

Developed as part of the government- backed Carbon Trust initiative to research renewable energy technologies, the so-called Manchester Bobber would produce more power than offshore windfarms, it is claimed.

Peter Stansby, professor of hydrodynamics at Manchester University and co-inventor of the Bobber, said: ‘When you hear that a wind turbine produces 2MW, that actually indicates the maximum output. The Bobber’s output of 5MW is the mean power output, with the potential for much more depending on sea conditions.’

The waves produce an oscillatory motion that is converted into one-directional motion through a clutch, which drives the generator. If the system is put into full-scale use the Bobber units will be attached to a platform or rig — about 20m above mean water level to avoid the maximum wave height — with the mechanics and generator on top. Mounting the units on decommissioned offshore oil-rigs is also being explored by the team.

Keeping all the device’s vulnerable mechanical and electrical components above water makes them more accessible for repairs and less susceptible to seawater damage, claimed Stansby.

The Bobber is intended to operate in low to medium sea states, as well as heavier weather conditions.

If this week’s tests prove successful, the next stage is to find funding to mount a full-scale trial and run a number of units side by side, said Stansby. He hoped that the Bobber’s efficient vertical action could mean that a number of units together would provide simple energy amplification.

The university’s spin-out development company, Manchester Intellectual Property, has applied for an EPSRC grant to test an array of up to 49 units.

Stansby said: ‘Despite all the talk about wave energy, there has been virtually nothing done on scaling up to see how different units interact with each other. That is our next step.’

Stansby’s team is working with construction contractor Mowlem and engineering consultant Royal Haskoning, which designed the rig. The project is one of a number of efforts to harness wave energy, which in the UK has tended to be overshadowed by wind power as a focus for renewables investment.

But several projects are underway, notably Wave Hub, a £13m initiative to build one of the world’s biggest wave energy farms off Cornwall.