This 30-year-old marvel is more powerful – and efficient – than ever

Turbine upgrades, plant modernization improvements enable Bad Creek to serve more Carolinas customers with cleaner energy

The final screw was just turned on a plant modernization project at one of the most powerful and flexible energy generation and storage assets on Duke Energy’s system: Bad Creek Hydroelectric Station in Oconee County, S.C.

The 164-foot-tall, four-level powerhouse is situated in the foothills of the Blue Ridge Mountains. But you wouldn’t know this from visiting the area. It’s hollowed into a mountain, 600 feet underground, accessible via a tunnel that was created by drilling through rock – the kind of thing you’d see in a Steven Spielberg film.

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Workers at Bad Creek Hydroelectric Station began disassembling the plant in 2018 to install new equipment, including massive spherical valves and three 700,000-pound transformers.

Using gravity to its advantage – the elevation difference between its upper reservoir where water is stored and Lake Jocassee below – Bad Creek operates like a massive battery, quickly generating electricity or storing energy based on customer demand.

Over five years, each unit was taken apart, then reassembled with more powerful and efficient components – a project that increased Bad Creek’s generating capacity by 320 megawatts (MW), enough to serve about 250,000 more Carolinas customers.

“After 30 years in operation, the plant required its first major maintenance outage,” said Preston Pierce, general manager for Hydro West at Duke Energy. “We had a choice in that we could disassemble all the units, recondition the parts and reassemble it, a lot of work to have the same output as before. Or we could invest in new turbines and more modern components to increase Bad Creek’s ability to store and generate energy.”

Duke Energy made the extra investment. The units were upgraded in phases, adding 80 MW of capacity to each new pump turbine. As a result, Bad Creek can generate a total of 1,680 MW, a 20% increase. It can also consume about 1,500 MW of excess energy to refill the upper reservoir when demand for electricity is low.

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Hollowed into a mountain 33 years ago, engineering wonder Bad Creek is just steps away from Lake Jocassee in the foothills of the Blue Ridge Mountains.

“The technological advancements in our hydraulic design put us in a position to be on the leading edge to help decarbonize our fleet,” Pierce said. “That’s exciting, no matter where you live in North Carolina or South Carolina.

“I’m also excited to see what else the future holds. Bad Creek can be a central part of what we’re doing in the Carolinas.”

Powering Carolinas’ energy growth

Bad Creek’s upgrades come at a time when Duke Energy is mapping out a plan to meet increased energy needs in the Carolinas, one of the fastest-growing regions in the country.

“From population growth to the expansion of manufacturing and other major economic development wins, the Carolinas are booming,” said Mike Callahan, Duke Energy’s South Carolina president.  

As energy needs increase, so does the demand for cleaner energy sources. Duke Energy is prioritizing investments in new generation that will maintain reliability with fewer emissions, with plans to relicense its nuclear and hydro fleet to make the most of its existing system resources.

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As general manager for Hydro West at Duke Energy, Preston Pierce oversees 14 conventional and pumped-storage hydro plants in western North Carolina and South Carolina.

In addition to the ongoing effort to relicense Bad Creek, the company is evaluating an opportunity to expand operations at the Oconee County site. A second underground powerhouse of equal size would roughly double the existing power generation and storage (pumping) capacity of the facility. 

Expanding operations would help Duke Energy meet forecasted load growth, while providing significant economic benefits of $7.3 billion to South Carolina, as the state benefits from construction and general infrastructure activity.

“We need a diverse energy mix to account for this growth on the coldest winter nights and the warmest summer days,” Callahan said. “We continue to look at solutions like expanding Bad Creek to make sure the power is there when customers need it, and it is as affordable as possible – providing certainty as they go about their daily lives.” 

‘The great integrator’

Most hydroelectric facilities rely on a flow of water to turn the blades of a turbine, which spin a generator, creating electricity that is fed onto the power grid. A pumped-storage hydro plant differs in that: When demand for electricity is high, a rush of water spins turbines as it moves from an upper reservoir to a lower one. When electricity demand is low, the turbines work in reverse, pumping water from the lower reservoir back to the higher one. It’s like a rechargeable battery.

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More than 1,200 feet separate the upper reservoir (foreground) from Lake Jocassee. The difference in elevation allows the plant to take advantage of gravity and produce more energy than traditional hydro plants with less water.

Bad Creek, in operation since 1991, was first envisioned as a weekly cycling facility. It would generate electricity for six hours each weekday (when power demand was high). Then it would run in reverse and refill the upper reservoir on weekends (when customers used less power). In the years that followed, operations transformed in tandem with the larger energy mix.

“As our system has evolved,” Pierce said, “we’ve turned Bad Creek into a facility that cycles between pumping and generating multiple times each day to maximize the effectiveness of the energy asset.”

This change is in response to a significant increase in the amount of solar energy Duke Energy and others have added in the Carolinas in recent years. Solar energy is variable; the energy output from an array of solar panels varies based on the position of the sun, cloud cover and more. Pumped-storage hydro power plants like Bad Creek are ideal matches to the ebbs and flows of solar output.

“Bad Creek is the great integrator,” Pierce said. “It’s able to store excess energy during off-peak times, then put it back on the system when it’s needed. As a result, our system operates at higher levels of efficiency while keeping costs lower for customers.”

A potential expansion

Expanding operations at Bad Creek would align with Duke Energy’s goals to reduce carbon dioxide (CO2) emissions, a goal shared by other U.S. utilities – and many of our customers, including some of the Carolinas’ largest employers.

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The powerhouse cavern houses the turbines and generators that power the plant. It’s so spacious that a 25-story building could fit horizontally inside and still have a little wiggle room.

Current operations only use about 30% of the storage capacity in the upper reservoir, which makes it an ideal candidate for expansion.

“If we add another powerhouse, it would roughly double how much energy Bad Creek can produce,” Pierce said. “So, we’ll be able to realize even more value from our existing infrastructure. That’d be a big win for Duke Energy and its customers.”

An added benefit of the project is that Duke Energy already owns the property required to build the Bad Creek II Power Complex.

A second powerhouse wouldn’t require creating any additional reservoirs and the locations of new structures have and will continue to be sited to help reduce impacts to natural resources, keeping environmental impacts low. Another factor as to why it’s ripe for expansion: Pumped storage is currently one of the only effective long-duration storage technologies available.

By comparison, it would take about 1,200 acres of battery storage for a similar storage equivalent to a second powerhouse. And because Bad Creek is long-duration storage (12 hours), you’d have to build out those batteries threefold due to their storage capacity of about three to four hours.

Economic impact of $7.3 billion (or more)

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Able to produce enough energy to power more than 1.3 million homes, the existing Bad Creek pumped-storage project provides emissions-free hydroelectric power to Duke Energy customers across its Carolinas service area.

If ultimately sought by the company and approved by a variety of regulators, an expansion at Bad Creek would also be a positive for the upstate and beyond, according to Joseph Von Nessen, Ph.D., a research economist at University of South Carolina. He studied the economic impact of Bad Creek on Oconee County and the entire state, using the data to project total economic impact of a potential plant expansion.

Bad Creek’s total economic impact in South Carolina is currently $40 million annually. This level of economic activity is associated with an estimated 98 permanent jobs that pay a total of nearly $7.8 million in labor income each year, Von Nessen said.

He also found that a potential investment by Duke Energy to expand Bad Creek, and related infrastructure work, could generate a cumulative economic impact of at least $7.3 billion in South Carolina by 2033, with an estimated 1,557 temporary jobs supported – directly or indirectly – each year between 2027 and 2033.

“Our hydroelectric legacy is as storied as our company itself,” Callahan said. “Putting the Upstate’s vast natural resources to use, while being incredible stewards of the environment, has helped fuel unprecedented growth in the state. It’s a great place to live.” 

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The Bad Creek project is located approximately 8 miles north of Salem, in Oconee County, S.C.