Wind PowerEarth and Environment
Land- vs. Sea-based Wind Farms Posted: November 16, 2005

Driving across certain parts of the United States reveals hillsides dotted with posts topped with gently spinning rotors, hundreds of feet high. These electricity-generating wind farms are mostly located in the Midwest and Great Plains, but now the United States' first wind park built on water is proposed for Nantucket Sound in Massachusetts.

Constructing a rotor. Photo credit: Cape WindCape Wind's project, aimed for completion in 2009, is a 24-square-mile project five miles off the shore of Cape Cod on Horseshoe Shoal. The 130 wind turbines are expected to have a total maximum output of 420 megawatts, creating enough electricity to power three-quarters of the Cape and Islands when working at average capacity, the company says.

Wind power has been growing as an alternative energy source, and the arrival of the first offshore project marks a general push toward diversifying energy generation from mostly fossil fuels.

Massachusetts is one of several states that has what is called a renewable portfolio standard, a policy that requires a certain percentage of a utility's power plant capacity or generation to come from renewable sources, such as wind.

The policy propelled the Cape Wind project into being -- with federal regulatory guidance but no federal funding, said Stan Calvert, chief engineer for the Energy Department's Office of Wind and Hydropower Technologies.

Europe has had offshore wind farms for years, and once the industry in the United States began proposing projects within a nominally competitive zone for cost, the Department of Energy recognized the opportunity for wind power nationally and began seriously studying the renewable energy source in 2004, said Calvert.

But when considering whether to move forward with proposed wind farms, officials must balance between the pros and cons of developing offshore versus onshore.

Offshore wind farms generally have more energy production potential. The wind, which glides over the smooth surface of water, is of a higher quality and less turbulent than wind traveling over land, said Calvert.

Cape Wind itself has an expected energy output of 38 percent of capacity over the course of a year, compared to the mid-to-high 20s or low-30s for onshore wind farms, noted Cape Wind's communications director Mark Rodgers.

Wind farms built on land, however, often are not as close to major cities and, therefore, do not raise as many objections, said Calvert. "A high percentage of the country's major cities are 100 miles from the coast," he added.

Another advantage to offshore wind plants is installing the turbines in water is easier without the presence of bridges, roads, etc., he said.

Wind turbines in water. Photo credit: Department of EnergyBut one of the main challenges to building offshore is cost. The price tag of installing offshore sites can reach 50 percent to twice that of land-based wind technology, Calvert said.

This cost is reflected in the fact that currently sea-based wind farms generate only about 600 megawatts, compared to 50,000 megawatts of land-based wind power, he added.

Aside from the financial challenges, the Cape Wind project faces other challenges stemming from the United States' uncertainty about what the environmental impacts may be, such as to seabirds and whether sounds may reverberate through the ocean disrupting marine life, said Calvert.

Cape Wind's project is, in this way, a test in how American officials will permit and regulate offshore wind power sites. Other companies have shown an interest in beginning the approval process, including a publicly owned utility in Long Island, N.Y. and a Louisiana-based private developer looking to Texas-owned waters in the Gulf of Mexico, he said.

Under the Energy Policy Act of 2005, the Department of Interior's Minerals Management Service is starting to regulate renewable and alternative energy programs, including wind technologies, located in the outer continental shelf -- federally administered submerged land usually three miles from shore.

In another partnership, the Energy Department in 2005 began working with the Massachusetts Technology Collaborative and General Electric, which makes wind turbines, to develop guidelines for offshore wind resources.

One idea is to create floating platforms for wind farms, similar to floating oil rigs, to station the wind turbines far enough away from shore so that people will not be able to see them in the hopes of eliminating concerns over preserving scenic vistas, said Calvert.

"The hope is that wind power will be embraced in many places like it has in the Midwest and Texas," he said.

-- By Larisa Epatko, Online NewsHour

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