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The wind power industry's largest-ever repowering effort is well under way at enXco's Shiloh IV wind farm in Solano County, Calif.

enXco is replacing 235 100 kW Kenetech wind turbines - constructed in 1989 - with 50 REpower MM 92 2.05 MW machines. As a result, the wind farm's net energy capacity will increase from 23.5 MW to 102.5 MW.

The company expects to complete the project by November, in time to qualify for the production tax credit, which is set to expire on Dec. 31, Hanson Wood, manager of origination at enXco, tells NAW.

enXco's repowering program is actually seven years in the making. In 2005, the company decommissioned 90 Kenetech machines and replaced them with 6 GE 1.5 MW turbines. In summer 2011, enXco decommissioned another 191 Kenetech turbines. All told, the developer expects to fully decommission 600 Kenetech wind turbines by 2016.

Kenetech's 100 kW single-speed wind turbines make up the 60 MW wind farm formerly owned by U.S. Wind Power, which in 1993 changed its name to Kenetech Wind Power. However, Kenetech filed for bankruptcy protection in 1996, and enXco acquired the wind farm assets in 2001.

From an energy, environmental and economic perspective, repowering a wind farm makes a lot of sense, Wood says.

"We see it as smart development - not only are we reducing the aggregate number of wind turbines, but we're providing a vital economic boost to the area," Wood explains, adding that the Shiloh IV project represents a $300 million investment.

Placing the new wind turbines in the same location can end up reducing biological and environmental impacts, Wood says. He characterizes the Shiloh IV project as an infill project - surrounded on all sides by operational wind farms - as a sort of middle ground between "green field" and "brown field" development.

Because the wind farm is contained within the boundaries of other wind farms in the area, there is less visual blight and less potential for avian impacts, according to Wood. From his perspective, repowering gives wind energy developers an opportunity to use industry best practices and modern technology to mitigate environmental concerns that have arisen since the late 1980s.

For example, the Kenetech turbines featured lattice-style towers that acted as nesting and perching spots for golden eagles and other raptors. Given the wind industry's push to mitigate wind development’s impact on avian species, developers will gladly employ current technology to allay environmental concerns.

Today's tubular-style wind towers dramatically reduce nesting and perching opportunities, Wood says. Furthermore, raptor concerns are mitigated somewhat because there are significantly fewer wind turbines, and they are spaced further apart.

A key component to any repowering program involves recycling. To that end, Wood says enXco hired a demolition contractor, and the vast majority of the project was recycled or salvaged for scrap. The only substantial waste products involved the blades and foundations, which were disposed of at a local landfill. About 20 of the towers and nacelles were resold, Wood adds.

enXco donated two non-operational wind turbines and down-tower computers to Rio Vista High School for education purposes. The donation follows the company's $150,000 donation to the high school in 2011 to start a wind technician training program.

Photo courtesy of enXco


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