Offshore wind power has not arrived yet, but ambitious proposals are coming in.
A wind power developer, Deepwater Wind, on Wednesday proposed a 1,000-megawatt wind farm in a spot between Rhode Island and the eastern end of Long Island in New York. The towers would be so huge, their blades rising 500 feet above the water’s surface, that they would be separated by seven- or eight-tenths of a mile, and thus would cover 270 square miles.
Perhaps more significantly, the farm would be connected to the grids of both New England and New York and could become a conduit for relatively low-priced electricity in the north to flow into the higher-priced New York market.
“Transmission projects are complicated, but they make an awful lot of sense,’’ said William M. Moore, chief executive of the company, Deepwater Wind.
A power line running from the offshore turbines to one point on shore would be mostly unused the majority of the time because the wind machines are seldom turning at full capacity, he said. But the power lines could be loaded with power generated on land -– from wind machines or conventional sources –- during hours when the wind was not blowing strongly offshore.
The Department of Energy has designated the land area that such a cable would bypass, Connecticut and part of New York State, as one of the two most congested, electrically speaking, in the United States.
In some ways, the project’s logic echoes the rationale for the Atlantic Wind Connection, a proposal for a transmission backbone that would run down the Atlantic coast from New Jersey to Virginia.
New technology has made offshore cables more practical.
Mr. Moore said that the proposed wind farm would be financed and built in phases, with 40 or 60 machines going up each year. The machines would generate 5 or 6 megawatts each. (By comparison, giant wind machines on land are generally 1.5 megawatts. A megawatt is enough to run a Super Walmart.)
The offshore depths are 90 to 160 feet, modest by oil drilling standards but very deep for wind. This would require building platforms that look a bit like bar stools, Mr. Moore said, with a standard “monopole” rising from the platform.
The rotor’s diameter would be 400 feet, so that when a blade pointed straight up, it would rise more than 500 feet above the water’s surface. Building huge machines makes economic sense at sea, where each platform is expensive and where giant blades can be delivered by barge, expert say. They are too long to move on most roads.
The project’s massive scale could bring down the unit costs, wind proponents say. A farm with wind machines of that size was recently approved for the coast of Belgium, Mr. Moore noted.
Along with huge machines, advocates say that what offshore wind needs to succeed is a sort of critical mass, the promise of enough investment that onshore industries will spring up to manufacture the parts in enough volume to push costs down.
“Offshore wind is clearly building momentum, which means more momentum for green jobs and lower prices for wind energy,’’ said Jacqueline Savitz, an analyst at Oceana, a nonprofit environmental group in Washington that recently published a study of the potential for Atlantic wind.
Locating the farm between two large power pools would make its output easier to absorb, Mr. Moore said. But it would require approval by the New York Independent System Operator as well as its New England counterpart and the Federal Energy Regulatory Commission.
It would also need permission from the Interior Department, which controls land use at sea, but that agency recently announced a simplified procedure for approving wind farms.
Mr. Moore said he had enough financing in hand to get through the planning phase but that new investors would be needed before construction could begin. Building the wind farm would cost $4 billion to $5 billion; the transmission line, which would be 150 miles long, would cost another $500 million to $1 billion, he said.By MATTHEW L. WALD/NYT