Duke Energy Carolinas tells federal regulators it is considering doubling the power of the Bad Creek pumped-storage station in South Carolina to accommodate plans for significantly more solar power on its grid to cut carbon emissions.
“A feasibility study for the potential second powerhouse is underway and will be completed by the end of 2022,” says Duke spokesman Ben Williamson.
He cautions that no decision on the expansion has been made. Even once the study is completed, it may take Duke some time decide whether to go forward. But, he says, Duke is looking at building the project by the end of the decade.
Duke is already building upgrades to the existing Bad Creek hydro plant that will increase its power to 1,400 megawatts next year. The federal licensing for that project expires in 2025.
And in a relicensing filing made last week, Duke tells the Federal Energy Regulatory Commission that is undertaking the feasibility study on the possibility of doubling that capacity,
“Given the need for additional significant energy storage and renewable energy generation across Duke Energy’s service territories over the Project’s new 40- to 50-year license term, Duke Energy is evaluating opportunities to add pumping and generating capacity at the project,” the filing says. “Construction of the 1,400-MW Bad Creek II Power Complex is, therefore, an alternative relicensing proposal presently being evaluated by Duke Energy.”
Started for nuclear
The plan, which is in very early stages, would double the roughly 1,400 megawatts at Bad Creek by building a second powerhouse with four turbines. It would include new caverns carved into Booger Mountain to accommodate new inlets, outlets, large vertical shafts and high-pressure tunnelsas well as the underground power complex.
It would not, however, increase the size of the 375-acre Bad Creek Reservoir or the 7,500-acre Lake Jocassee at the site.
Bad Creek operates by pumping water from Lake Jocassee in South Carolina to the 375-acre Bad Creek Reservoir, where the water is stored until needed to produce power during peak usage on the system. It was built in 1991 to use excess power produced at night by the three nuclear plants Duke Carolinas’ operated at the time.
Nuclear plants cannot be easily turned on and off to follow high demand for electricity during the day and the low demand at night. Using the power they produce overnight to pump water to the upper reservoir to Bad Creek — and an earlier pumped Storage plant Duke built on Jocassee in 1973 — allows Duke to use the reservoirs as batteries to store power that would otherwise be wasted.
There is a similar issue that is becoming more acute as solar and other renewables become more widely used in North Carolina. On a bright, sunny afternoon, for instance, solar projects may produceand store more power than Duke can use on its system, particularly as the company adds more solar.
More input
Long-term resource plans for Duke Carolinas and its sister utility Duke Energy Progress have proposed building has much as 16,250 megawatts worth of new solar capacity in the state by 2035.
Bad Creek is already used to store some power from renewables. But the need for storage is going to grow significantly as solar spreads more widely on the Duke system. That will be particularly true, if, as Duke Energy Corp. (NYSE: DUK) has proposed, it combines the grid operations of Duke Carolinas and Duke Progress in the next few years. Duke Progress produces significantly more solar power than Duke Carolinas, but it currently has no pumped storage of its own.
The expansion would allow Duke to fill the upper reservoir more quickly and drain it more quickly during peak use so it could produce a maximum combined output of 2,800 megawatts. That would double the 1,400 megawatts that will be available when the plant completes its upgrade next year; the current maximum is 1060 megawatts.
But going to the maximum output will shorten the duration of the power production. Essentially the duration is cut in half, and the number of megawatt hours of electricity produced would be somewhere between 30,500 and 31,000. However, it allows excess power to be stored and released at greater levels to balance supply and demand on the system.
Williamson says expansion will require approval by state regulators as well as FERC. And Duke intends to allow for significant input from customers and other interested parties before any final decision is made.
“Filing the pre-application document with FERC is the first step in a multiyear collaborative process that includes review and input from various regulators and local, state and federal stakeholders,” he says.
