Tidal Turbine Blades Missing

NS: Blades missing on experimental tidal turbine recovered from Bay of Fundy
By John Lewandowski, the Canadian Press

Source: The Canadian Press - December 17, 2010

[HALIFAX, NS] - The strength of the currents in the Bay of Fundy may have been too much for an experimental tidal-power turbine that quit working shortly after it was deployed over a year ago.

All 12 blades from the unit’s core were missing when the 400-tonne turbine was lifted from the floor of the Minas Basin about a kilometre off Parrsboro, N.S., around noon on Thursday.

However, officials from Nova Scotia Power Inc. and Ireland’s OpenHydro, who have partnered for the demonstration project, said they’ve already learned a lot from their cursory look at the recovered unit.

“The blades have failed and we need to understand why,” said James Ives, OpenHydro’s chief executive officer.

“But the rest of the turbine, all the generator sections all look to be in very good condition.”

Ives said it’s early in their analysis but they think they overloaded the one-megawatt capacity turbine by underestimating the strength of the tidal current running through it in the Minas Basin.

“We’ve potentially underestimated how much energy is in that site,” said Ives, who calculated that the turbine’s capacity should have been doubled.

“We always thought that the Bay of Fundy was an extremely good tidal resource, but those flows are even stronger so that makes it all the better.”

Mark Savoury, NSP’s vice-president of technical and construction services, said of the six objectives set for the two-year demonstration project, three have been met including deployment, recovery and unit stability.

Early data suggests that the gravity base didn’t shift “a millimetre” during a full year of submersion.

And he said they’re well on their way to understanding more about tidal velocities, the environment and the ruggedness of the machine.

Savoury said they remain committed to the project but it’s too early to know whether they will redeploy the recovered unit or go with an entirely new one.

“The vast majority of the technology and the engineering is not in the blades but the outside diameter and that all looks like it’s in good shape, from what we can see so far,” he said.

Ives said OpenHydro engineers will inspect the turbine once it arrives in Halifax harbour some time in early January.

As to whether to fix and reuse or deploy a new unit, he did express a personal preference.

“We’ve moved on a couple of generations in technology since we built this machine. I would always be keen to be testing out latest technology on a site.”

The 10-metre diameter turbine looks like a giant jet engine and stands on a tripod-shaped base.

Data from its underwater cameras and acoustic monitoring equipment stopped flowing about a week after it was lowered into the water in November 2009.

Clean Current Power Systems Inc., a British Columbia-based firm, and Minas Basin Pulp and Power Co. Ltd. of Hantsport, N.S., have also outlined plans to install experimental turbines in the bay.