Before the company proceeds, however, it must monitor the first six turbines for 18 months to assuage concerns of federal and state regulators that the turbines, whose tips cut through the water at up to nine meters per second, won’t chew up the river’s fish. Such qualms have already delayed the first-of-its-kind project by several years. Corren says monitoring to date has shown that few fish venture into the strong currents flowing past the turbines, but he says the extensive studies will provide a critical foundation for future developments.

Meanwhile, Canadian and European tidal-turbine producers are already scaling up their designs. Marine Current Turbines of Bristol, England, has operated an 11-meter, 300-kilowatt turbine off Devon for four years and plans to install a one-megawatt turbine in Northern Ireland’s Strangford Lough this year. Marine Current’s design resembles Verdant’s but uses two rotors, each with two blades. Other competitors are scaling up so-called ducted turbines, which are surrounded by a power-boosting shroud to guide water flow. Nova Scotia Power recently signed up Dublin’s OpenHydro to install a one-megawatt ducted turbine in the Bay of Fundy, while Vancouver-based Clean Current Power Systems is working on a two-megawatt version of the 65-kilowatt ducted turbine it installed off the coast of British Columbia in December.

Although scale will reduce costs, Clean Current president Glen Darou says the nascent industry will also have plenty of work ahead proving the reliability of its mechanical and electrical systems underwater. “Salt water is insidious,” says Darou; try as you might to seal it out, corrosive seawater “will get in there eventually.”