A WAVE-DRIVEN generator with virtually no moving parts could make wave power a more efficient and competitive form of renewable energy. The key to the device, dubbed the Snapper, is the way it converts a slow, steady wave motion into an efficient current-generating jackhammer-like action.
Despite growing enthusiasm for wave power in countries such as the UK and Portugal, wave-driven generators are still dogged by heavy start-up costs and low efficiency. Generators produce electricity most efficiently when a small force is applied at high velocity. Waves tend to produce large, slow-moving forces, so most generators have to resort to turbines or hydraulics to convert the forces into a suitable form. This adds to the complexity and expense, and also reduces efficiency.
Now Ed Spooner, a consultant engineer based in the UK at Crook, County Durham, has devised an alternative solution consisting of a buoy linked to a generating unit on the seabed. The buoy is attached to a vertical armature inside the generating unit, and as it bobs up and down magnets mounted on the armature induce a current in static coils fixed to the generating unit.
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Mounted next to the armature are a parallel set of fixed magnets, aligned with the magnets on the armature. It is the interaction between the two sets of magnets that produces the Snapper鈥檚 jerky motion. The attraction between the two sets of magnets tends to hold them in place next to each other. As the buoy tries to rise with a wave, this attraction initially holds it down. When the buoyancy force becomes large enough to overcome the attraction between the magnets, the buoy and the armature attached to it move sharply upwards until the magnets align again. As the buoy continues to rise this behaviour is repeated. Then as the buoy descends after the wave has passed, a spring produces a similar effect as the armature moves downwards.
Spooner told the World Maritime Technology Conference in London this week that the result is a sequence of rapid movements that generate pulses of current.
Experiments on a prototype show the arrangement results in increased current-producing forces compared with existing wave-power systems, suggesting that much smaller generators could be built for the same output, reducing costs.
Spooner has passed the patent rights for the device to the New and Renewable Energy Centre in Blyth, Northumberland. Its director of technology, Keith Melton, says the increased efficiency of the device should help to make wave-powered generators competitive with other renewable energy sources, such as wind power, as well as with fossil fuels.
