On US border, a surge in tidal-power projects

Tides are a fact of life on the Bay of Fundy, and here more than most places. Strong enough to carry a small sailboat backward, they flow around this island in reversible rivers. Currents smash together in a violent chop or conspire to create whirlpools – including the hemisphere's largest.

People have long dreamed of harnessing these tides, including Franklin D. Roosevelt, who wanted to build dams from Deer Island to the Maine and New Brunswick mainland as part of an aborted Depression-era energy scheme. Until recently, the environmental and monetary costs of tidal dams nixed most efforts.

But with high energy prices and increased demand for renewable energy, tidal power is taking the stage again. It's greener this time, with new technologies that promise to generate clean, predictable power without dams or negative environmental consequences.

More than a dozen developers have been working on this so-called "in-stream" technology inspired by wind turbines. Most of their prototypes incorporate turbines attached to the seafloor, where tidal currents spin them safely beneath the shipping lanes and, hopefully, without troubling marine life. Almost all require further field-testing before they're ready for large-scale deployment.

"The technology is still in its infancy, with people trying out a lot of different technologies to pick the winners," says Margaret Murphy of Nova Scotia Power, which has partnered with an Irish company to test turbines at Minas Passage, a narrow waterway flowing into Minas Channel near the head of the Bay of Fundy, where tides reach 50 feet. "We feel if it's going to happen, it should happen here and it should happen now."

Spurred by a survey

Last year a North American survey of potential tidal energy sites by the Electric Power Research Institute in Palo Alto, Calif., found that most of the best potential sites were in the Bay of Fundy, including Nova Scotia's Minas Passage and the three passages that surround Deer Island, including one that forms the boundary with Maine.

Put together, the three Deer Island sites could produce an estimated 29 megawatts of electricity (enough to power 20,000 homes) by capturing 15 percent of the tide's energy – EPRI's rough estimate of how much could be safely withdrawn without disrupting the environment. The Minas Passage site might produce as much as 152 megawatts, powering 117,000 homes.

The study has triggered an explosion in interest that has surprised even its author. Nova Scotia and New Brunswick promptly launched a detailed site evaluation process, while three companies have secured permits to test their technologies on the Maine side of Passamaquoddy Bay, which opens onto the Bay of Fundy.

"I was shocked at the speed of the response," says EPRI analyst Roger Bedard. "There's a confluence of forces that are coming together right now that are making private investors believe renewables are about to really take off."

Concerns about the environmental, economic, and strategic costs of relying on fossil fuels have been on the rise, prompting many states and provinces to adopt renewable energy quotas. Experts say that over the past decade, wind power has been proven commercially reliable, but other alternatives are needed. "Everybody's interested in renewable energies because we all realize we're going to need them," says Darwin Curtis of the New Brunswick department of energy. "We think tidal energy is very promising."

Key advantage: predictable energy

Tidal power has a big advantage over wind or solar: You always know how much is going to be available, and when.

"The dispatchers who run the grids, who have to match supply and demand at all times, can perfectly predict what they'll be getting from the position of the sun and the moon," notes Mr. Bedard. And because water is more than 800 times as dense as air, he adds, the same amount of power can be created with a much smaller turbine than a wind farm would need. Most designs are hidden deep underwater and thus out of sight.

Once the prototypes start hitting the water – in Eastport, Maine, this November and Minas Basin in 2009 – there will be plenty of challenges to overcome. The Bay of Fundy's frigid, powerful currents will test any machine submerged in it, just as scientists and regulators will be taking a careful look at how currents and sea life are affected by the machines.

OpenHydro, the Irish company behind the proposed Minas Basin project, has the rights to a turbine design that has undergone tests in Scotland's Orkney islands as a 0.3-megawatt prototype. A Norwegian firm, Hammerfest Strom, intends to install a full-scale 1-megawatt device in Scotland in 2009.

"We don't expect to have any effect at all on the currents or marine life, but we won't know for sure until we test it," says Chris Sauer of Ocean Renewable Power Co., which will begin testing a small prototype in the passage between Eastport and Deer Island this fall. "Before we go to full deployment, we'll have all those answers."

Another unknown: how much tidal energy can be captured without altering the flow and, therefore, the marine environment. "One would think one turbine would have a very minimal impact, but how about 200 or 400?" asks Lesley Griffiths of Halifax, Nova Scotia, who is heading up the ongoing strategic environmental assessment of potential sites in Nova Scotia and New Brunswick. "At what point will it start affecting how and where sediments are carried and how tides are experienced in harbors?"