This article discusses that despite of the challenging winter weather conditions the largest windmill-based power plant located on East of Mississippi has been exceeding performance expectations. Green Mountain Power selected the Searsburg site because of its powerful and persistent winds and its proximity to existing access roads and transmission lines. The stronger winter winds enable the plant to generate more electricity at the time it is most needed. Indeed, the wind power plant at Searsburg, the largest east of the Mississippi River, is expected to have a positive effect on the environment by reducing the need to burn fossil fuels in other parts of New England. Green Mountain Power estimates that the electricity generated by the Searsburg plant will eliminate approximately 22 million pounds of air emissions per year that would have been generated by adding fossil fuel-burning capacity.
Most wind power farms in the United States have been constructed in either sun-kissed Califori1ia or the prairies of the Great Plains states. More recently, however, this renewable energy source has been demonstrating its effectiveness in cold, snowy climes thanks to Green Mountain Power Corp. in South Burlington, Vt. The recently commissioned 11 high-tech windmills in Searsburg, Vt. , have generated over 3.4 million kilowatt-hours of electricity in the first quarter of 1998. This is sufficient power for about 1,500 homes.
Green Mountain Power selected the Searsburg site because of its powerful and persistent winds and its proximity to existing access roads and transmission lines. The stronger winter winds enable the plant to generate more electricity at the time it is most needed. An added benefit is the region's remoteness from population centers, thus eliminating most environmental concerns.
Indeed, the wind power plant at Searsburg, the largest east of the Mississippi River, is expected to have a positive effect on the environment by reducing the need to burn fossil fuels in other parts of New England. Green Mountain Power estimates that the electricity generated by the Searsburg plant will eliminate approximately 22. million pounds of air emissions per year that would have been generated by adding fossil fuel-burning. capacity. The cost per kilowatt-hour of energy generated at Searsburg will be comparable to alternative sources over the 25-year life of the plant.
Eleven windmills in Vermont have generated sufficient power for about 1,500 homes.
Green Mountain Power contributed about 64 percent of the $11 million price tag of the Searsburg plant. The remaining funds were awarded by the joint Electric Power Research Institute (EPRI) and U.S. Department of Energy (DoE) Wind Turbine Verification Program (TVP). EPRI and DOE launched the TVP in 1992 to evaluate prototype advanced wind turbines developed at several sites by U.S. electric utility companies, as well as to link turbine development and commercial applications.
The Searsburg wind plant encompasses 11 Z-40FS wind turbines designed by Zond Energy Systems Inc. in Tehachapi, Calif. This includes power collection and switching equipment, and a 1.5-mile transmission line that delivers the power generated by the turbines to the transmission grid of the New England Power Company in Westborough, Mass.
Each Zond Z-40FS wind turbine is mounted on a 40-meter-tall tubular steel tower that is supported by 200-ton concrete foundations. "We chose tubular towers rather than lattice-type towers for two reasons. First, maintenance workers can climb inside the' 12-foot-diameter tubes without being exposed to the elements, and because the tubular towers provide little opportunity for birds to perch," said Bill Ralph, a mechanical 'engineer for Green Mountain Power.
The turbines themselves consist of a horizontal axis, a three-blade rotor measuring 132 feet in diameter, a gearbox transmission, an induction generator and a computer control system. The rotors turn at a constant speed of 29 revolutions per minute and each generates 550 kilowatts of electricity at wind speeds between 29 and 65 miles per hour. The computer controls located at the base of each tower adjust the turbine's orientation and blade pitch to optimize power output with changes in wind speed and direction. These controls include a 17-megahertz, 32-bit Motorola microprocessor as the main controller.
Ralph worked with Zond engineers on the features of the cold-weather package that was developed for the Searsburg project. It includes providing the rotor blades with a slippery, black surface to minimize the accretion of ice and concentrate the sun's energy to shed ice. In addition, there are several heaters and synthetic lubricants that enable the rotors to operate in temperatures as low as rninus 40°C.
The installation of the wind turbines, on the largest wind farm east of the Mississippi River, posed a challenge to Zond engineers more used to building wind power plants in California or the sprawling Midwest. "Searsburg's turbines are installed on a mountain, and at this elevation, 2,700 feet to 2,900 feet, the construction season is very short. In the spring we get mud, and the roads are narrow," said Ralph. Local subcontractors helped smooth the raising of the towers before the beginning of November, 1996. Debugging and refining was accomplished before the wind plant was commissioned in July 1997.
"We are pleased with the plant's recent winter performance, which exceeded our expectations," said John Saint-cross, director of resource portfolio management at Green Mountain Power. "Not only does this break new ground, operating turbines under the difficult winter conditions in Vermont, but they have also achieved a high level of community support and pride for the project," noted Tony Armor, director of generation technology development at EPRI.
Armor said that wind energy in the U.S. is particularly strong in the Great Plains and on both coasts, and the success of the Searsburg plant will encourage other utilities to exploit wind power. A similar 6.6 megawatt EPRI-sponsored wind project was installed in 1995 by Central and South West Services in Fort Davis, Tex. Future wind projects designed to evaluate wind generation are planned for Iowa, Nebraska, New York, Oklahoma, and Texas. Two small wind projects in Wisconsin and Alaska that are also associated with the TVP program will provide useful wind turbine performance and other data, according to EPRI.