Stillwater’s Energy Center’s design earns recognition, praise

An energy center’s design is getting some recognition, and its owner, Stillwater Electric Utility, couldn’t be happier.

The Burns & McDonnell-designed Stillwater Energy Center project recently earned an Honor Award in the Energy category from the Oklahoma chapter of the American Council of Engineering Companies.

The award recognized the design firm for helping the utility build a project that can generate rapid, efficient and flexible energy to counterbalance fluctuations in power from renewable sources.

At its heart are three reciprocating, natural gas-powered engines connected to generators that can quickly spin up to generate 56 megawatts of electricity.

When needed, the energy center provides power through the Grand River Dam Authority (the contracted power buyer) to the regional transmission organization, the Southwest Power Pool. The Southwest Power Pool’s mandate is to keep affordable and reliable electricity flowing across its multistate area of responsibility.

Stillwater officials said they felt like their choice to build the project was one that helps the environment, its customers and indeed, people across the central U.S.

“This is one of the most efficient plants of its type in the Southwest Power Pool system,” said Loren Smith, director of the Stillwater Electric Utility.

“It is a great story.”

Electrical questions

Stillwater Electric Utility is the second-largest municipally owned electric utility and is the largest municipal generator and transmission utility in the state. Stillwater has owned its own electric utility since 1901 and owned its generation since 1903.

The last generation plant built by the utility before it built its current energy center east of town on Airport Road was Boomer Lake Station in the mid-1950s.

That station, which had two steam-powered generators, could produce 27 megawatts of power and was able to supply all of Stillwater’s electrical needs until 1967. After that, Stillwater supplemented its generation by buying power from the Grand River Dam Authority and other wholesale power suppliers.

In 1988, Stillwater took the station offline and overhauled it to extend its expected life by 20 years while the city rebuilt Boomer Lake’s dam.

The city returned Boomer Lake Station to service in 1994, primarily running it during summers as a peaking plant to provide the city with supplemental power. Meanwhile, the community and its power demands continued to grow. And the regional electricity marketplace evolved as well.

By 2012, city officials knew the Southwest Power Pool was about to implement an integrated markets system where utilities and other power distribution entities would buy power from and sell power to the regional grid, daily.

They also realized a significant and growing amount of renewable energy, primarily generated by wind farms, was finding its way onto the grid.

The question they faced, Smith said, was whether Stillwater should rebuild its existing plant, get out of the power generating business altogether, or do something else.

As officials studied that question, they learned about a natural gas-powered “simple cycle” plant that uses massive reciprocal engines connected to generators to make electricity.

They determined that design would provide the utility with a low cost, efficient way to create power the Southwest Power Pool could use to help balance power supplies across the grid, keeping power reliable and affordable for its customers.

“We are doing our fair share,” Smith said.

Specifications

The Stillwater Energy Center, which cost about $70 million, includes a power generation building that houses three 25,000-horsepower natural gas fired reciprocating combined engine/generation units, with room for more.

Together, the Wartsila engines — the largest in the world when they were manufactured for Stillwater’s project in Trieste, Italy — are capable of producing a total output of 56 megawatts of electricity.

They can be brought online and to full load in 10 minutes, can be shut down in three minutes, and can be restarted six minutes after that.

The motors, officials said, require very little water for cooling and do not require high pressure gas. They also are extremely efficient and affordable to maintain and generate minimal emissions.

The center also includes an operations/administrative complex and an electrical transmission and distribution substation.

A major challenge for contractors building the project involved getting the engines to Stillwater. Each unit weighs 580,000 pounds, and Stillwater’s Smith said each had to be broken into several sections to get them to the community using rail and truck transportation.

Other project challenges involved obtaining power purchase agreements from the Grand River Dam Authority, executing a revenue bond issue to finance it, building out the infrastructure needed to get an adequate natural gas supply to the site, and air permitting issues.

Contractors began building the project in July 2015, and the facility, which employs 17, began commercially operating a year later.

An engineer who was the project manager for Burns & McDonnell on the Stillwater Energy Center project, Brian Elwell, said his firm has designed numerous, similar plants, but never any in the heart of the nation.

“The logistics of the transportation was a challenge on this project,” agreed Elwell. “We set up a big tent, where we used cranes to reassemble the engines on the site and put them into the building.”

But, despite that challenge, Elwell added Stillwater thought ahead by designing its center so it could add two engines to generate more power, if needed.

He observed Stillwater also brought another advantage to the project — abundant potential sources of competitively priced natural gas.

“There were multiple natural gas lines, not very far away,” he said. “That enabled the city to negotiate with multiple vendors to find the best provider.

“Definitely, the city had a very competitive advantage. All of my other clients would love to have that, but very few do.”

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