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to power 20,000 homes) by capturing 15 percent of the tide's energy – EPRI's rough estimate of how much could be safely withdrawn without disrupting the environment.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.

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