Lawnmower-style underwater turbines

A new design for underwater turbines promises to make tidal energy harvesting cheaper and more efficient, according to a team of engineers at Oxford University. In essence, this design is more horizontal than today’s tidal energy-harvesting devices, which resemble small wind turbines installed underwater. The Oxford design looks like it uses the blades of an old-fashioned lawnmower.They’ve built and tested a prototype, and now they’re scaling it up to the size they hope will one day become commercial.

The UK is thought to have about 10 percent of the world’s harvestable tidal energy. The country’s first tidal turbine started generating electricity in July at 150 kilowatts.

Ocean power has only just gotten started. One plan that has a provisional nod to proceed involves installing seabed turbines off the coast of South Korea. If a 1-megawatt pilot project next spring succeeds and passes an environmental assessment, then the company, Lunar Energy, expects to get the go-ahead to put in a field of 300 tidal turbines. Another tidal project, by Pelamis Wave Power, is in a pilot phase off of the northern coast of Portugal, and the company says it is in talks to expand that. San Francisco’s mayor, Gavin Newsom, has also made bold statements about harnessing some form of ocean power before he leaves office.

The biggest question is still whether these devices will prove to be economical; as of now, they haven’t shown themselves to be. One economic estimate holds that if the turbines were installed as a farm, the cost per megawatt would be just under the price of installing wind power. If the Oxford design is as efficient as they predict, this team can’t be ruled out.

Lots more details are available in this story in the UK Guardian.