A look inside Bad Creek Pumped Hydro, the biggest battery in the Carolinas

SALEM, S.C. — Nestled in the Blue Ridge Mountains, one of the biggest pieces of Duke Energy’s renewable energy fleet has been working diligently for decades, using the power of water and gravity to keep the lights on in nearly a million homes. Now, as the company works to comply with North Carolina’s net-zero carbon energy requirement by 2050, the Bad Creek Pumped Storage Project will be a key piece of the puzzle.

The Bad Creek Pumped Storage Project came online in 1991, at first, as a way to store energy from Duke Energy’s nuclear fleet.

While some power generating plants, like coal and natural gas, are load-following, which means they can ramp up or down depending on the need for energy, nuclear plants are primarily base-load generators, which means they produce the roughly same amount of energy regardless of whether that power is needed at any given time.

To prevent excess power from going to waste when it was in low demand and make it available for peak demand hours, Duke needed energy storage options, and they looked at pumped hydro as the solution.

It works like this: there are two water reservoirs. One is higher than the other. When energy is abundant, an electric motor pumps water through a turbine from the lower reservoir into the higher reservoir, storing it until energy is in high demand. That’s when gravity takes the water down through the turbines, turning them to generate electricity, essentially reusing the power produced earlier in the day.

At Bad Creek, engineers accomplished this with four sets of motors, generators and turbines, that control the flow of water between Lake Jocassee and Bad Creek. When it opened, it could store up to 1280MW of power. Once current upgrades on the project are completed this spring, it will be able to store up to 1400MW, enough to power a million homes in the Carolinas.

The pumped storage facility has been a massive part of Duke’s energy grid for more than 30 years, but now with the demand for energy in the Carolinas expected to skyrocket over the next 15 years while Duke plans to phase out it’s coal-burning facilities, Ben Williamson, a company spokesperson, said Bad Creek will be an even more vital piece of the company’s transition.

“Long-duration storage is very important to a utility where renewables will play a factor,” he said.

Most of Duke’s renewable energy comes from solar, which tends to peak around the same hours every day (typically between 10 a.m. and 4 p.m.). High energy demand, meanwhile, tends to peak around 6-9 in the winter and early evening in the summer. A facility like Bad Creek would be able to shift the time that power is available far more efficiently, and for a longer period of time than any utility scale battery currently available. Currently, Bad Creek can provide 12-24 hours of energy storage.

“It is thousands of acres of land that would be required for the amount of batteries that it would take [to match Bad Creek,]” Williamson said. “But then you would need to multiply those batteries threefold because they only are going three to four hours.”

Creating a facility like Bad Creek, however, is no easy task. Duke got its license to build the facility in 1977, spent ten years and $1 billion to bring it to fruition. Engineers had to build a dam around the Bad Creek, blast into a mountain to build the powerhouse and create, at the time, the biggest elevator in South Carolina, to construct these pump and generator units hundreds of feet under the reservoir.

Even the recent upgrades to improve efficiency and storage capacity, cost roughly $200 million. The upgrades started in 2018 and are on track to be completed March 2024.

In its Carbon Plan, Duke also proposed building a second powerhouse at Bad Creek to more than double its storage capacity. That would involve another lengthy and costly process to carve into the mountain and build new pump and generator units, though the powerhouse could work off the same reservoir and connect to existing transmission infrastructure. Bad Creek II would be expected to come online in 2033.

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