On US border, a surge in tidal-power projects

"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?"

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