Gas Peakers with Clutches Power Bakken Oil Boom

With rapidly growing electricity demand from North Dakota’s booming shale oil industry, Basin Electric Power Cooperative needed flexible peaking generation in a hurry. Two stations equipped with LM6000 turbines and clutches are providing both peaking and reactive power.

U.S. electricity production has been flat for the past decade, hovering between 3.9 billion MWh and 4.1 billion MWh per year. For Basin Electric Power Cooperative (BEPC), though, it has been a scramble to add capacity fast enough. Largely due to the booming oil and natural gas production from the Bakken Formation in the Williston Basin, industrial electricity sales in North Dakota increased by nearly 60% between January 2007 and February 2013. Commercial and residential sales increased by 20% or more in that same period.

“We are seeing growth in housing developments, retail stores, and all the ancillary support businesses,” says BEPC Project Coordination Representative Curt Pearson. “We are also seeing load growth due to the farm economy with a lot of our cooperatives’ member owners improving their farm operations.”

To meet the anticipated demand for an additional 1,270 MW of capacity by 2015, BEPC has created a balanced plan involving two new peaking plants, synchronous condensing for voltage support, wind farms, and new transmission lines.

“The cooperatives in that area are seeing really phenomenal growth,” says Pearson. “If you’ve been following the Bakken, you know how quickly everything has been developing out there.”

A Multifaceted Approach

Headquartered in Bismarck, N.D., BEPC is a regional wholesale electric generation and transmission cooperative servicing 136 member rural electric systems with more than 2.8 million customers in Colorado, Iowa, Minnesota, Montana, Nebraska, New Mexico, North Dakota, South Dakota, and Wyoming. It also, through its subsidiaries, markets coal, operates a carbon dioxide pipeline, quarries limestone, and provides Internet hosting and security services (the latter two, while unusual for urban-focused utilities, are not uncommon for rural cooperatives). For its main function of generating and transmitting electricity, it owns and operates more than 5,300 MW of coal, nuclear, hydro, wind, and peaking capacity.

But the Bakken Formation growth has thrown BEPC’s plans out of balance. In 2007, the region was producing 150,000 barrels of oil per day. It is now producing more than a million barrels per day, second only to Texas. The region is also experiencing a glut in gas production—1.3 Bcf/d in July 2014, according to the N.D. Department of Mineral Resources—with substantially more coming out of the ground than there is pipeline capacity to ship it out. (BEPC’s portfolio actually includes about 1 MW of capacity generated by natural gas flaring.)

North Dakota has the highest population growth rate in the country, according to the U.S. Census Bureau, and in 2012 the state’s per-capita GDP increased by 11%. In 2009, BEPC and its member systems had planned for an additional 400 MW of demand in the area by 2025, but by August 2014 that figure was revised upwards to 1,270 MW.

To get the additional capacity needed in a hurry, BEPC is working on a build-and-buy strategy. The build part includes adding two peaking stations, detailed below. Meanwhile, BEPC proposes running a new 190-mile, 345-kV transmission line to the Bakken area from the 900-MW coal-fired Antelope Valley Station near Beulah, N.D. That project won approval from the U.S. Forest Service and U.S. Department of Agriculture Rural Utilities Service this summer and state regulators earlier this year. BEPC is set to begin construction, though permits are still needed from the U.S. Army Corps of Engineers and the U.S. Department of Energy.

With the new line, says Pearson, “Not only can we get power from the Antelope Valley Station, but the substation at the Antelope ValleyStation allows us to connect to the grid so we can purchase power from other plants and utilities as needed.”

In November 2013, BEPC also signed a 25-year power purchase agreement with Infinity Wind Power LLC, which will build two wind farms near Beulah with a total capacity of 278 MW. Both wind farms are scheduled for completion by the end of 2015.

“It is a multi-faceted approach to meeting our member cooperatives’ needs and their constituents’ needs, which makes sense in today’s marketplace,” says Pearson. “With the wind farms, our peaking stations, and other resources that we will be able to access, we will be able to meet the forecasted demand.”

Peaking Plants

Gas turbine–based peaking plants are designed to provide immediate power to meet demand spikes, and in this case the peaking plants themselves were rushed to the scene to start generating long before the wind farms and transmission lines are permitted and built. BEPC was the first utility in the world to install a General Electric LMS100, but this time it decided to go with the smaller LM6000.

“The size was what we needed, and the machines were available to meet our needs at this time,” says Pearson. “They were something we could phase in as we continued our load studies.”

BEPC now has two peaking plants in the heart of the Bakken production area. Both plants have three 45-MW LM6000s, with more generation being added. Phase 1 consisted of getting the first unit at each location online in a hurry. The first of the two plants to come online was the Pioneer Generating Station near Williston, which went commercial on Sept. 4, 2013. It was followed a few months later by the Lonesome Creek Station close to the town of Alexander, west of Watford City (Figure 1).

1. Fast-start, fast-build plants. Basin Electric Power Cooperative (BEPC) is building two three-unit peaking stations to serve rapidly growing demand from oil and gas exploration in the Bakken Formation. The Pioneer Generating Station (left) and the Lonesome Creek Station (right) both employ General Electric LMS6000 turbines equipped with clutches between the turbine and generator. A third phase is planned for both plants, starting next spring. Courtesy: BEPC

One interesting element of these plants, according to Pearson, is that each generating unit has a synchronous clutch between the turbine and generator. “If needed, we can disconnect the turbine from the generator, and the generator will continue [spinning] and act as a motor, and that will help with voltage support in the area,” Pearson explained. “That was an important component of the design of both stations.”

The clutches were built by SSS Clutch Co., the same company that provided the clutch for BEPC’s original LMS100. The clutches are designed to connect when the speed of the turbine matches or exceeds that of the generator and disconnect when the turbine slows down. This allows the operator to use the turbine to bring the generator up to synchronous speed and then connect to the grid. If generation is not needed, the turbine can be shut down, leaving the generator synchronized to the grid and providing reactive power. Then, when generation is needed, the turbine can come up to speed quickly, because it isn’t already driving the generator, and then connect to a generator that is already synchronized to the grid.

Can’t Add Capacity Fast Enough

The original plans from November 2011 and February 2012 were to have a single turbine at each station, but it soon became clear that 45 MW was not enough. So in July 2012, the BEPC Board of Directors approved two more turbines for each site. Phase 2 at Pioneer reached commercial operations in January 2014; Phase 2 at Lonesome Creek will start up in December.

Yet even that has proved to be insufficient. In July 2014, with demand still growing rapidly, BEPC decided to add a third phase to both plants. At Lonesome Creek, this will consist of another two 45-MW turbines. For Pioneer Station, BEPC will add 12 9.3-MW gas-fired engines, for a total of 112 MW. Construction on Phase 3 is slated to begin next spring, with completion scheduled for mid-2016. ■

Joe Zwers is a freelance writer in Glendale, Calif., specializing in engineering, technology, and business.