As some talk wind farms, others want to harness the tides - Nantucket Sound considered as site

The Massachusetts Tidal Energy Co. is considering building an underwater tidal energy project in state waters off Martha's Vineyard and Naushon Island, the private island owned by the Forbes family and used by US Senator John F. Kerry. While plans are preliminary -- even the technology is still under development -- the developer is seeking approval from the Federal Energy Regulatory Commission for a feasibility study in parts of the Sound extending from Woods Hole to the southern tip of Naushon Island.

The project would harness ocean currents by using underwater propeller blades 20 to 50 feet in diameter connected to a generator. The devices would be anchored at varying depths, and the power would be sent to electric transmission lines in Falmouth or Tisbury, Martha's Vineyard.

Unlike the wind farms, which many think would make waterfronts look like industrial zones, the tidal project is expected to be largely unseen, though a consultant on the project could not say exactly how much would appear above water. ``The less that's above the surface, the less aesthetic impact, and in a setting like this, that's certainly a consideration," said Charles B. Cooper, director of environmental permitting and planning with TRC Environmental Corp. of Lowell, a consulting company studying sites for the developer.

Massachusetts Tidal is a subsidiary of Oceana Energy Co., based in Washington, D.C., a startup firm that has filed seven other applications for permits to study sites across the country. ``I don't know how many of these sites will pan out," said Oceana president Dan Power. ``We are at the beginning stages."

Cooper said the proposal would not conflict with Steamship Authority ferry routes, but could require some areas to be off limits to navigation. He said he expects the project would have to work in harmony with fishing, boating, and other uses in the Sound.

``My belief is that in order for these types of units to be deemed acceptable, there's going to have to be the ability to coexist," Cooper said. ``It's certainly one of the design considerations. The idea would be to allow all other uses and not preempt any of them."

Nonetheless, the project immediately sparked concerns and questions about developers seizing public space for development. Cape Wind Associates proposes to use 24 square miles of Nantucket Sound for a wind energy project, a deal that delights clean energy advocates but concerns residents who say it is unfair for a for-profit developer to cordon off their waterways.

Some environmentalists said they would wait to hear more details about the tidal proposal before judging it. ``On one hand, it's really exciting to have lots of ideas about energy development," said Mark Rasmussen, executive director of the Coalition for Buzzards Bay. ``On the other hand, it highlights the central issues with wind and now these subsurface proposals: Where is the appropriate spot?"

The Vineyard Sound location was eyed by the developer because of its strong currents, Cooper said.

It's also close enough to shore to connect fairly easily to electric transmission lines, also an incentive for the offshore wind projects, which would tie into a Massachusetts power market in dire need of additional power sources. Independent System Operator New England, which operates the six-state power grid, has been warning that New England faces a looming crisis and the likelihood of rolling blackouts as soon as summer 2008.

Details of the tidal project are still on the drawing boards, Cooper said. An FERC permit would give the developer three years to develop the technology, investigate the site, and work with stakeholders on the proposal.

The developer would also need to file plans with state environmental regulators, who would evaluate effects on fish or marine life as part of a review.

Tidal energy has been harnessed for hundreds of years. Millers would take advantage of a tidal basin by building dams across the opening, allowing the basin to fill on the rising tide and then slowly releasing the water through a waterwheel to convert it to energy. However, most tidal basin projects come with environmental consequences, such as silt build-up and reduced tidal flushing.

In recent years, new technology is making tidal energy popular again. Projects are being researched to capture the extreme tides in Washington and Canada's Bay of Fundy, where monster tides can rise 75 feet.

For the last 15 months in New England, the industry-funded Electric Power Research Institute has been evaluating the potential for tidal projects in New England, several other states, and two Canadian provinces. The institute conducted a feasibility study for Muskeget Channel between Nantucket and Martha's Vineyard and Eastport, Maine.

While Maine's project may be commercially viable, Roger Bedard of the institute said the Massachusetts model is not as commercially promising, because of its lower tides.