Drew Robb, contributing writer
Over the past five years Europe pioneered the development of offshore wind farms, establishing 13 small offshore plants in Sweden, Denmark, Holland and UK. In 2002, the 160 MW Horns Rev project went online off the Danish coast. Fueled by pro-renewable European Union government legislation, even larger plants are planned in Ireland and UK. Meanwhile in the U.S., plans for offshore wind development off the Eastern seaboard include a proposal for what could become the world’s largest plant, set to be built off the Massachusetts coast.
“With today’s volatile fuel pricing, increasing environmental concerns and wind energy’s cost competitiveness, more and more energy suppliers are adding wind power to their electricity mix,” said Steve Zwolinski, President of GE Wind Energy, America’s only commercial wind turbine manufacturer.
PacifiCorp, AEP and FPL have each accumulated hundreds of megawatts of wind resources and have bold plans for the future. Linn Draper, CEO of AEP, the largest burner of coal in North America, has added 310 MW of wind energy to the company’s portfolio since 2001.
“We are the true believers in wind,” said Draper. “It’s good for the environment, adds diversity to your portfolio and reduces the risk of fuel price volatility.”
The reason for such widespread support is as much to do with the price per kW as it is with environmental concerns. Twenty years ago, wind cost 75 cents per kW. Today, it is down to the 4 to 8 cents range, depending on the site and the turbine technology employed. These cost reductions are a result of booming markets for wind power that have spurred on innovation. Nowhere is this more evident that in offshore wind.
Compared to land-based wind, offshore locations have several advantages. Wind turbulence is less, enabling greater energy harvesting, reduced fatigue, and smaller turbine towers.
“Wind speeds are much higher at sea on average,” said Zwolinski. “Also, due to the lack of proximity of natural barriers such as mountain ranges and urban areas, wind experiences less turbulence over water.”
On the downside, the initial capital investment, as well as O&M fees are far higher offshore. In order for offshore wind to be profitable, therefore, economies of scale must be created whereby large offshore wind farms are sited near heavy load areas.
Projects in the wind
Cape Wind Associates LLC of Boston, for example, is the developer of a 468 MW project (420 MW net) proposed to be located off the coast of Cape Cod in Massachusetts’ Nantucket Sound. This wind farm could provide enough power to meet about three quarters of the annual requirements of the Cape and nearby islands, or approximately half a million average American homes.
“Nantucket Sound gets some of the strongest offshore winds in the U.S., is out of fishing and shipping routes, and the wind farm will be situated about five miles offshore,” said Jim Gordon, managing general partner of Cape Wind Associates and president of Energy Management Inc. (EMI). “We have selected to GE to provide the wind turbines for the Cape Wind project.”
In total, this amounts to 130 3.6 MW machines. Turbines of this magnitude play an integral role in offshore wind achieving true viability. And the technology behind them has seen major investment over the past year.
“We are calling on the total resources of the General Electric Company as we invest in technology to continue increasing the output, efficiency and commercial viability of wind turbines,” said Zwolinski. “Synergies with several GE businesses—including plastics, transportation, air-craft engines and our global research center—are playing a valuable role as we continue to move forward with wind turbine development.”
This research and development has culminated in the GE 3.6 MW turbine, the largest offshore turbine currently in commercial production. A range of technical innovations was incorporated into the design to keep the overall turbine cost of energy down. This includes new blades, an improved gearbox concept and adjustments to the structure to enhance load absorption and optimize assembly, transport and service logistics. It also includes patented power electronics technology and a variable speed rotor.
Several other additions to the 3.6 MW machine serve to reduce maintenance costs. The 3.6 MW machine features a pulse-width modulated frequency converter, a three-step gearbox and a doubly-fed asynchronous generator. As a result, only the power generated in the generator rotor (usually 25–30 percent) has to be fed through a frequency converter into the grid. Cape Wind will probably utilize tubular steel towers fitted on a monopile type foundation. These steel foundations are hammered into the seabed.
Turbines of this type are already been utilized in Ireland. GE Wind Energy is in the final stages of erecting seven 3.6 MW machines at the Arklow Wind Project. This is the first stage of another big offshore facility. Eventually, 200 turbines will stand on the Arklow sandbank to the south of Dublin, producing 520 MW—10 percent of the country’s electricity.
Robb is a Los Angeles-based freelance writer specializing in energy and technology.