News

Wild Horse Wind Power Project

May 22, 2008



On the wind-swept ridges of Whiskey Dick Mountain, about 15 miles east of Ellenburg, Wash., a revolution is taking place. It's the same movement that is spreading throughout the United States in places where the breezes blow in sufficient velocity and frequency to drive giant windmills that produce electricity.

Puget Sound Energy is building the 229-Megawatt Wild Horse Wind Project at Whiskey Dick as part of its strategic plan to secure low-cost, long-term diverse resources for its customers' growing electricity needs. The utility is working toward having at least 5 percent of its total electricity supplied by renewable sources, including wind power, by 2013.

After shattering previous records with more than 2,400 megawatts of wind energy installed in the United States during 2005, the industry is on course to bring on line an additional 3,000 megawatts in 2006, according to the American Wind Energy Association. This year, wind farms across the country will generate an estimated 25 billion kilowatt-hours of electricity, serving the equivalent of 2.3 million homes.

"Wind is an abundant and free domestic energy resource," said Randall Swisher, executive director of the AWEA, speaking in June at the WINDPOWER 2006 Conference and Exhibition in Pittsburgh. "Coupled with modern technology, wind energy displaces the need for fossil generation and reduces U.S. dependence on imported energy.

"As we have seen in Europe and with growing popularity in other nations of the world, wind power is proven, and can play a substantial role in powering America's energy future. Wind energy works — for our economy, environment and energy security."
By the Numbers

It's no small task to install 127 large turbines on a remote site that measures about 15 square miles, but that's what Puget Sound Energy doing at the $380-million Wild Horse project.

The turbine sites are situated along ridges with sufficient space between so they won't interfere with each other, explained Brian Doughty, project manager for PSE. Doughty served in a similar capacity on PSE's 150-megawatt Hopkins Ridge Wind Farm project, which was completed in 2005.

The placement of the turbines was designed for the prevailing winds, Doughty said, but the units can be managed individually if the wind shifts to an unusual direction. With the highest points on the site reaching 3,600 feet above sea level, Wild Horse is within a site-specific FAA limitation to not go above 4,000 feet.

As if the size of the site and number of turbines weren't enough to establish the magnitude of the project by the numbers, consider the specifications for each of the 1.8-megawatt Vestas V80 turbines.

Manufactured in Denmark, the turbines consist of an 80-ton nacelle and a 10-ton hub, to which are connected three blades, each weighing 7 tons and measuring 80 meters (about 130 feet) long. These units sit atop three-piece steel towers that stand 221 feet tall.

With Puget Sound Energy as owner, there are two prime contractors for the Wild Horse project.

The Portland office of Denmark-based Vestas Wind Systems A/S is responsible for supplying, erecting and commissioning the wind turbines. Vestas manufactured its first wind turbines in 1979 and has concentrated exclusively on wind energy since 1987.

Horizon Wind Energy is the balance-of-plant contractor. Based in Houston with its Northwest branch office in Portland, Horizon currently is operating and developing projects in more than a dozen states. Renewable Energy Systems Ltd. was contracted by Horizon to construct the site infrastructure, consisting of roadways, turbine foundations, the electrical collection system, substation, and transmission line.
Assembly Line

On-site mobilization and initial construction of roads and tower foundations began on Oct. 17, 2005. Crews worked throughout the winter, though there were a few day when high winds and snow halted work, said Tom Bensel, PSE's senior inspector on the project.

Doughty described the construction process as resembling an assembly line. Rather than building one complete turbine at a time, the work proceeds in multiples. The first step is road building (altogether nearly 35 miles of it) to provide access to the tower sites. Next comes foundation work for the towers and trenching for the cables. When the foundations are ready, a crane sets the base and middle section of the towers. Finally, a larger crane follows along to set the top piece of the tower, the nacelle and the blades.

The tower sections are built in Vietnam, shipped to the Port of Vancouver, Wash., and trucked to the site. Similarly, the components of the nacelles and hubs are shipped from Europe through Vancouver to the Wild Horse laydown area for assembly.

While all this is under way, separate crews were building an on-site substation and a microwave site on Whiskey Ridge that connects to the towers via fiber optic cable and will provide communications links for monitoring and controlling the towers remotely. Additional work includes construction of eight miles of transmission line off-site to a PSE substation for connection to existing PSE line; the upgrade 26 miles of transmission lines beyond there; and construction of a lattice tower crossing of Columbia River to Wanapum Switch Yard (owned by Grant County PUD).

The workforce on the project peaked at about 250 people, Doughty said.

"It's definitely a multi-discipline operation," Bensel observed. "We've got every aspect, pretty much."
Rocky Site

Site conditions on Whiskey Dick Mountain were a combination of good news and bad news. On most of the site, a thin layer of topsoil blankets solid basalt rock formations. The hard rock provided a secure foothold for the towers, but it also played havoc on the trenching equipment, Bensel observed.

Each tower is set on a patented P and H tensionless concrete foundation, a design by California-based Patrick and Henderson Inc. that takes advantage of the rocky conditions. Basically, the design allows the tower and its foundation to exist as a single unit so that when the tower leans the entire structure is subject to moment swing, and the concrete in the foundation never goes into tension, Doughty said.

The foundations are concrete cylinders measuring 14 feet outside diameter and extending to depths of 25 feet, 28 feet, 30 feet, or 32 feet depending on ground conditions. Building the tower foundation starts with stitch drilling around the perimeter and setting charges to loosen the rock. Then the hole is excavated by conventional means.

Two corrugated steel cans, the outside measuring 14 feet in diameter and the inside 10 feet in diameter, are set into the excavation and backfilled. Between the cans, 120 anchors bolts extend to the depth of the excavation and are encased in an annular ring of concrete. The bolts are cast in the foundation, and when the foundation concrete has achieved its design strength (cured), the tower base is set over the bolts and grouted in place. The bolts are then stretched by applying a tension of 86,000 pounds to achieve a specified elongation, and the nuts turned down snug, forming a solid unit.

"What we are trying to do here is create a socket in the rock that will hold the tower," Doughty explained.
Special Technique

Erection of the towers and turbines is fairly straightforward. Lifting subcontractor Barnhart Crane & Rigging utilizes a special technique that allows a single FMC-Link-Belt lattice-boom crane to pick the tower sections from the horizontal position on a truck bed, stand them up vertically and move them into place. Bensel said the rig involves the use of a sling and J-hook that hold the bottom of the section by gravity until it reaches the proper position to pop free. The process saves about 45 minutes, plus the expense of a second crane, over the familiar two-crane lift.

"Safety is the biggest factor," Bensel said. "This section (a tower base) weighs 38 tons. It's not something you would want to drop." To date, there has been just one lost-time accident on the project.

Barnhart uses the FMC-Link-Belt crane for the base and middle sections of the tower. A mighty 425-ton Demag 2600 does the high lifting of the top tower section, nacelle and blades. In the laydown area, a Lampson Manitowoc 4100 Vicon lattice-boom crane does the lifting work.

When PB&E visited the project in early June, the Wild Horse Substation was substantially completed and schedule to be energized later in the week. Once its circuits were tested, the substation would be ready to power up the turbine units for testing as they are completed.

Despite the huge site, the volume of work and the remote location, the Wild Horse Wind Power Project is on schedule for completion in December of this year, just 14 months after construction began. And when Wild Horse begins generating electricity, it likely will garner a lot of attention from other "revolutionaries" in the wind energy industry.

"Once this is dialed in, (Wild Horse) will be a flagship station for the United States," Bensel said. "It's state-of-the-art for an electrical facility."

Key Project Participants

Owner: Puget Sound Energy

Turbine Contractor: Vestas Wind Systems A/S

Balance-of-Plant Contractor: Horizon Wind Energy; Renewable Energy Systems Ltd.

Heavy Hauling: Wilhelm Trucking Co.

Lifting: Barnhart Crane & Rigging

Blasting: Rock Solutions Inc.

Road Construction: Herling Construction Inc.

Foundations: Dressel Enterprises

Transmission Lines: American Energy Inc.

Substation: General Electric/Christensen Power Services

U/G Collector System: Power Partners

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