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Building turbines in tornado alley

Duke Energy Renewables faced some challenges while building their first project in Oklahoma, not the least of which was unpredictable weather due to the site's location in tornado alley.

By Tony Kryzanowski

Duke Energy Renewables has discovered that the wind really does come sweeping down the plain in Oklahoma, just like the opening song in that famous musical with the same name.

The company recently commissioned its 200-megawatt (MW) Frontier wind power project in Kay County, Oklahoma, and already has its eyes set on a second project, Frontier II, right next door.

Frontier II, with a potential output of 200-MW or more, has been under development since 2014. Amshore US Wind, the original developer of Frontier I, conducted initial work such as negotiating lease agreements with landowners, measuring the wind resource, and completing environmental studies. Amshore and Duke are co-developing phase II, advancing the project's interconnection position, wind resource and environmental studies, and project design. Duke has now taken Frontier I across the finish line, and the companies continue to work together to advance Frontier II.

Frontier I is selling all its power to Springfield, Missouri-based City Utilities, on a 22-year power purchase agreement (PPA). Wanzek Construction was the construction contractor on the project.

Mike Braun, Duke Energy Renewables project director, says that the company is investigating PPA opportunities for Frontier II, which would serve to advance development of that project. Should a PPA be awarded, they hope to be able to complete that project by the end of 2020.

"The market seems to be good, with a lot of people buying power," says Braun. "There are municipal utilities like City Utilities of Springfield, who purchased the power from Frontier I, and a growing number of commercial and industrial customers out there. Right now, there is a lot of attention on renewable energy."

Frontier I was Duke's first wind power project in Oklahoma and the first time that the massive, Vestas V-126, 3.3-MW wind turbines were put into production in the United States. These units feature 126-meter blades, which are considered extra long for the industry. They also provided the step-up transformers, towers, and nacelles.

A total of 61 wind turbines at a height of 87 meters were constructed over about a 9,000 acre area, with lease agreements signed with 42 landowners.

"We studied a number of turbine variations but the Vestas 3.3 on an 87-meter tower proved to be the best option in our model," says Braun. "Also the bigger the turbine, the smaller the overall project footprint. We constructed fewer turbines for the same total project capacity."


At its peak, the construction project had as many as 250 workers on site. Now completed, the Frontier project is providing 10 full-time jobs and supplying renewable energy to about 60,000 homes.

The wind farm is located near the city of Blackwell, about 90 minutes north of Oklahoma City. John VanDeLinde, Duke Energy construction manager, says the project has received tremendous local support; it isn't uncommon for residents to approach company individuals (wearing clothing with the Duke insignia) to express how grateful they are that the company chose the Kay County area to make this investment. One particular benefit that Kay County residents received with the development was the upgrading of a number of county roads, to accommodate the heavy loads of hardware needed for each wind turbine installation.

"The county road infrastructure was nowhere near what it needed to be to handle the heavy payloads coming off the highway onto the gravel roads to deliver to each pad location," VanDeLinde says. "We spent the first couple of months building up the Kay County roads and widening them out so we could have two-way traffic that was safe, and making them durable enough so we could make deliveries under safe circumstances. We maintained those roads over the entire construction process."

One way that the community welcomed Duke Energy Renewables and the Frontier project was by helping the company lease a vacant building for ongoing operations and maintenance use, as well as blending in costs associated with upgrading the building so that it suits Duke's needs into the lease payments.

"Rarely does a project, by design, have a multi-generational economic impact on a region like Duke Energy Renewables' new Frontier wind farm," says John Robertson, executive director of Blackwell Industrial Authority. "Blackwell is fortunate to have been selected for their operations and maintenance facility, assuring decades of high-tech jobs and investment in our rural location."

 Frontier I is Duke Energy Renewables' first wind power project in Oklahoma and it is the first time that the massive Vestas V-126, 3.3-MW wind turbines have been used on a project in the U.S. These units feature 126-meter blades, which are considered extra long for the industry.

Dave Hazel, working with Energy Renewal Partners on contract with Duke Energy Renewables to handle such matters as lease negotiations, permitting, and communication with local officials, says he has been working in the local area for the past couple of years. The impact the tax revenue generated from this wind power project is having on the community is quite evident.

"I've had local landowners who were not involved in the project, and who just live in the area, approach me to express their gratitude that our wind project and the other operating wind projects in Kay County have brought better educational facilities to Kay County," he says.

"Right now, those schools are building new additions, they are installing a new track at one of the schools, and there is a new early learning facility that is being built," he says. "People are extremely excited that it's all due to wind power and that they are getting upgraded and brand new facilities for their children, who are obviously the future."

Duke approached the project with a definite goal of maintaining good communication and an open-door policy, with the main message being that there would be benefits in addition to the royalty fees and lease payments to local landowners. Construction projects like those at local schools demonstrate how that is definitely the case.

The terrain where both Frontier I and the future Frontier II are located is described as flat Oklahoma farmland, making it ideal for wind power production. The land is farmed for a variety of crops and for grazing livestock. The wind resource itself is described as fairly consistent, with Kay County being home to a robust transmission system that helps get the power to major load centers.

The terrain where both the Frontier I wind project and the future Frontier II project are located is flat Oklahoma farmland, making it ideal for wind power production. 

Hazel says that each turbine installation has a small footprint on each landowner's property, taking up about two acres including the access road. Farming and ranching continue to take place right up to the wind tower pads and access roads.

An initial concern with the wind turbines was the aesthetics, he says. "But once we started putting the turbines up, people couldn't stop looking at them. They are majestic, they are tall, they are beautiful, they are white, and much nicer to look at than a coal plant or some other type of power plant."

Wind power development is an established industry in Oklahoma, with a couple of other projects having already been completed in Kay County prior to Duke's arrival. "I would say that there are a lot of areas still to be built in Oklahoma," says Braun. "I think it is a question of whether the state continues to support it. I think the state of Oklahoma is quite promising for the next few years in terms of development and building."

Transmission of the power produced by Frontier I to Duke Energy Renewables' customer, City Utilities, went smoothly despite the customer being out of state. Fortunately for Duke, Oklahoma Gas & Electric had just constructed a new 345-kV substation facility less than a mile from the Frontier development, which made connection of Duke's collector substation to the transmission system of the Southwest Power Pool an easy task. The main power transformer in the Duke substation was provided by GE Prolec. The collection cables on the project were supplied by Southwire.

However, constructing the pro-ject, which began in January 2016, was no walk in the park, and Oklahoma's weather patterns were definitely factored into how construction was handled.

"The biggest hazard that we encountered was weather," says Hazel. "The weather is unpredictable across Oklahoma because of the potential for tornadoes in that part of the country. But we also encountered heavy rains, which essentially would come in and literally dump anywhere from two to eight inches of rain at one time."

Consequently, Duke was required to constantly maintain and build back its roads within a tight timeline to maintain the scheduling for the overall construction project.

The weather also factored into scheduling deliveries and the need to tie down equipment once it arrived on the site but prior to installation.

There are automatic features built into the installation, as with other wind installations, so that the wind turbines can feather their blades into the wind and stop spinning during high wind events, although Hazel says there is nothing that can withstand a direct, major tornado hit. Duke Energy Renewables monitors each of its wind and solar power sites across the United States 24/7 from their Renewable Control Center in North Carolina. Technicians can make remote operational adjustments to enhance reliability, improve production, and ensure the safety of all personnel.