As a wave of wind power proposals sweep across New England, researchers from the electric utility industry have concluded that it makes economic sense to look underwater for affordable electricity.
The Electric Power Research Institute contends underwater turbines powered by the tidal movement at three sites, including one in Maine, can produce electricity at a cost that competes with wind power and natural gas-powered power plants.
Its study concluded that tidal power could produce electricity for 4.2 to 6.5 cents per kilowatt-hour at those three locations. For comparison's sake, the standard offer for Central Maine Power customers is 8.4 cents per kilowatt hour.
"I was shocked when my team came up with those cost-of-electricity numbers. I thought, 'It can't be,'" said Roger Bedard, the project leader in Palo Alto, Calif.
Bedard's team provided a detailed analysis of the technological and economic feasibility of tidal resources at one site apiece in Maine, Massachusetts, California, Washington and Alaska, and in two Canadian provinces, New Brunswick and Nova Scotia.
In Maine, the study focused on the Western Passage in Passamaquoddy Bay, where twice a day the tide rises and falls 20 feet, the greatest tide change in the continental United States. The other two sites with the greatest potential were at San Francisco's Golden Gate Bridge, and in the Bay of Fundy at Minas Pass, Nova Scotia, Bedard said.
Tidal power appeals in several ways.
Unlike the wind, tides are predictable, for starters. And water's greater density means fewer turbines are needed to produce the same amount of electricity as wind turbines. Since they're underwater, there aren't aesthetic issues associated with wind farms.
The study focused on locations like rivers and other narrow passages where the tidal flow is concentrated, creating the greatest potential for affordable electricity.
The tidal-powered turbines are much like wind turbines, but their blades turn more slowly. There are several types, some of which look like two- or three-bladed wind turbines. Others look like a cylinder surrounding multiple blades. All are attached to the ocean floor. An underground cable would connect to a substation on shore.
The EPRI study focused on large, commercial turbines that make one revolution every six seconds. That should be slow enough for fish to escape harm, and the theory will be tested later this year in New York's East River and in the United Kingdom, Bedard said.
For all its promise, the obvious problem for developers is the regulatory process, since no one has ever obtained a permit for a commercial-scale project and the current regulatory scheme was designed for conventional hydroelectric projects, Bedard said.
But that isn't stopping companies from rushing to file proposals with state and federal regulators to get their foot in the door.
Maine has five preliminary proposals from the Piscataqua River that divides Maine and New Hampshire to the Western Passage that divides Maine and Canada's New Brunswick. In between, there are proposals for the Kennebec and Penobscot rivers. A fifth proposal calls for a different kind of tidal project using a dam in coastal waters off Cutler.
So far, the Federal Energy Regulatory Commission has received 21 preliminary permit applications for tidal power projects, said spokeswoman Celeste Miller. Ten have been granted and the others are pending, Miller said.
Maine is promoting the idea of small-scale demonstration project, said Beth Nagusky, top energy adviser to Gov. John Baldacci.
"What people want to see is a demonstration project, to see if it works not only environmentally but economically," said Dana Murch, dams and hydro director for the Maine Department of Environmental Protection.
The technology is in its infancy, similar to wind power 20 or 25 years ago, he said. And the permitting process will have to evolve, as well.
In Maine, environmental officials say the closest thing to a permit for an underwater turbine project would be a hydroelectric permit, Murch said. And it has been 20 years since a new permit was issued to build a dam in Maine, he added.
All of the tidal power talk comes against a backdrop of a flurry of proposals for wind power projects across New England.
In Maine, one wind power project is under construction in Mars Hill, and at least five more are being explored, including two proposals near the Sugarloaf USA ski area that would produce enough electricity for more than 100,000 homes.
Vermont's Public Service Board is expected to decide this summer whether to approve a plan for four turbines on East Mountain in East Haven. And in New Hampshire, there's a proposal to put a dozen 400-foot turbines in Lempster.
As for tidal power, the EPRI study focused only on sites with commercial potential. But there are scores more smaller cites that could be conducive to smaller-scale projects in Maine and elsewhere, said Mike Mayhew, Maine's energy efficiency engineer.
All of that talk raises questions for Pat White, top executive with the Maine Lobstermen's Association who fishes from York Harbor.
He said he wants to see the test results on how the underwater turbines affect marine life, including Maine's lucrative lobster fishery.
"I want to know what it's going to do to the baby fish and lobsters," he said.