Nova Scotia’s Race to Harness Tidal Power

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ABOARD THE PLAT-I 6.40 GENERATING PLATFORM, Nova Scotia — The Bay of Fundy, off the Canadian provinces of Nova Scotia and New Brunswick, has long tantalized and frustrated engineers hoping to harness its record-setting 50-foot high tide to generate electricity.

After more than a century of attempts, there has only been one small power-generating station, since closed, and countless broken dreams, abandoned plans and bankruptcies.

Even so, a new coalition of entrepreneurs and scientists in Nova Scotia are trying again. One participant, a company called Sustainable Marine, has devised a new technology and successfully operated it for more than seven months, longer than any other similar system, producing enough electricity for about 250 homes.

Sustainable Marine’s innovation is that rather than placing stationary turbines onto the seabed as has been tried in the past, it floats movable ones on the surface, lifting them when a dangerous object approaches and for maintenance.

If the platform continues to prove reliable, is economically viable and doesn’t harm marine life, it will have harnessed not just a new source of renewable energy, but also one of the most reliable ones in the world. Because unlike wind or sunshine, tides are unceasing and completely predictable.

Sustainable Marine is one of five racing to produce a viable method of electrical generation in the Bay of Fundy and, it hopes, in dozens of similar tidal regions in the world.

Scientists collaborating with a provincial government research center are studying the impact of the technologies on marine life. A fishing group unsuccessfully went to court six years ago to block the laying of underwater cables at a government test site, and ran billboards with the catchphrase “Grinding Nemo.”

Regulators have required Sustainable Marine to outfit its platform with a variety of underwater sensors and cameras to track sea life and to automatically lift the turbines when whales or other large creatures approach.

If Sustainable Marine’s underwater sensors and cameras confirm assertions by the tidal power generation industry that fish, whales and other sea creatures will safely swim around their turbine blades and the prototype proves reliable, it may become part of a large-scale development.

Engineers and scientists in Nova Scotia are driven to harness the tides partly because the province is one of the few in Canada that still relies heavily on fossil fuels to generate power.

While the country’s three largest provinces long ago traded fossil fuels for other energy sources, Nova Scotia still produces 51 percent of its electricity by burning coal, the mining of which was once a key part of its economy. With the province now committed to eliminating those plants by the end of the decade, attention is again focused on the tidal power generation potential of the Bay of Fundy.

Every six hours in the Minas Passage — the narrow portion of the bay near the port of Parrsboro, Nova Scotia — the water level rises or falls about 55 feet, roughly the height of a four-story building.

In all, 14 billion metric tons of water make the trip across the bay every 12 hours at speeds of up 12 miles per hour. The Minas Passage is estimated to have the potential to generate about 7,000 megawatts of power, more than double the amount of electricity currently generated by other sources for the province of nearly one million residents.

The Bay of Fundy has “been called the Everest of tides,” said Lindsay Bennett, the acting general manager of Force, a provincial government tidal research station about six miles from Parrsboro. “It’s been described over the years as sort of the Fundy standard. If you can operate your technology here in this environment, you can operate your technology anywhere in the world.”

The Bay of Fundy’s funnel shape is part of the reason for its exceptional tides. Along its 96 or so miles of length, the bay dramatically narrows and its depth drops from 765 feet to 147 feet.

The bay’s water has a natural rocking motion, like any large body of water. But what distinguishes the Bay of Fundy is that is that it rocks back and forth at the same frequency that its tides rise and fall. The tide amplifies the sloshing motion — and vice versa — each making the other faster and higher, increasing the tide.

Since the early 20th century a variety of schemes have been proposed or tried to turn this into a source of electricity. One complicated project in 1915 planned to use the force of the tides to pump water up to reservoirs above the bay. That water would then pass through a conventional hydroelectric generating plant as it returned to the sea. A fire that destroyed the project’s equipment in 1920 brought it to an end.

Worldwide, including in the Bay of Fundy, the only tidal power generation technology that has gained any traction involved building dams containing power-generating turbines. Nova Scotia operated one of four tidal barrage dams in the world until it was closed three years ago because of environmental concerns and a mechanical failure.

Free-standing tidal power generation technologies have generally relied on turbines, placing them into the water, where they spin as the tide flows through them, then converting the energy produced by the spinning into electricity.

Seven years ago, Nova Scotia passed a law to support the development of a tidal power industry that protects the environment. The province has since selected five companies to run demonstration projects that would test and show off their technologies.

The first project did not offer an auspicious start. It involved fitting a turbine about 52 feet in diameter on the seabed. But almost as soon as it was in the water, the force of the tide shredded the turbine.

“It was under-engineered,” Ms. Bennett said. “Nobody had a full understanding of the power of these tides.”

The potential power at the Minas Passage, recent research has shown, is about 24 times greater than the original estimate.

During the second project, a more robust turbine was then lowered into the sea only to have the company behind it go bankrupt. After a year of running without maintenance, the turbine seized. For now, it sits lifeless on the seabed.

Visiting Sustainable Marine’s project, the most advanced of the latest efforts to turn Fundy’s tide into electricity, involves two ferry rides to the village of Westport, population 193, on Brier Island. When the tide is out, the shacks on adjacent lobster fishing wharves loom far above the water on stilt-like pilings.

Sustainable Marine, a German-owned company based in Scotland, came to Westport for initial tests of its system, which has been feeding electricity into Nova Scotia’s grid since March. Westport’s proximity to the mouth of the bay means its tide has about half the force of what’s found at the Minas Passage, making it less risky for trial runs.

The platform, as the company refers to its power generator, resembles a white submarine with two large hulls as outriggers. Spread across one end, like a vastly oversized outboard motor array, are six, three-bladed turbines. The platform is 107 feet long and 87.6 feet wide at its broadest point, and is highly automated.

While circling the platform in a large inflatable boat, Nabil Al-Kahli, the project’s senior engineer, demonstrated its capabilities by pulling out his phone and commanding the turbines, each 13 feet in diameter, to lower themselves in pairs into the receding tide. A faint hum filled the air as their generators kicked in, and the platform rose like a motorboat when its generators began producing power.

Mr. Al-Kahli said that so far the platform and the attached underwater cable sending its power ashore have worked as planned.

To ensure reliability, said Kiley Sampson, a marine engineer who is operations manager for Sustainable Marine Canada, the project has adapted proven technologies from ships and offshore oil drilling.

The turbines, for example, are modified bow thrusters — the electrically driven propellers that keep cruise ships snug against docks — made by Sustainable Marine’s parent company Schottel, a major shipbuilder and propeller maker. They use electric motors as a generators.

Ms. Bennett said tidal power generation is likely to require significantly higher investments than other forms of renewable energy like solar and wind, effectively increasing the cost of power it generates. Mr. Sampson said, however, that its costs should decline over time.

Standing on a walkway above the churning turbines, Mr. Al-Kahli who is from Yemen, reflected on the transition his career had undergone since he arrived in Canada from Singapore four years ago. He went from building and installing oil and gas rigs, a source of climate change, to pioneering one of its alternatives.

“For me, going from oil and gas offshore to marine renewable is really good,” he said.

Sumber: www.nytimes.com

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