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Natural Gas Stars in Duke Energy's Carolinas Power Revamp

Natural gas is the cornerstone of Duke Energy's newly announced plan to retire its Asheville, NC, coal-fired power plant within five years and modernize its power generation and transmission system in western North Carolina and upstate South Carolina.

"With the availability and near-record low cost of natural gas, this comprehensive project will transform the energy system in the region to meet the growing needs of our customers and significantly reduce emissions and water use," said Lloyd Yates, Duke's president for the Carolinas region. "We're eager to move ahead quickly on these projects and complete the key components of the plan by the end of 2019."

The plan's major components include retiring the 376 MW Asheville coal power plant, investing $750 million to build a 650 MW natural gas-fired power plant, and installing solar generation at the site. Charlotte, NC-based Duke said the combination of natural gas and solar will be one of the first of its kind.

Duke spokesman Dave Scanzoni told NGI there were no details available yet on how much natural gas the plant would use.

To support the new power plant, a natural gas pipeline extension will run through an existing PSNC Energy right-of-way area, which runs from Kings Mountain to Arden, NC, Duke said. The extension will connect to the larger intrastate Transcontinental Gas Pipeline (Transco).

Williams Partners’ Transco recently filed at the Federal Energy Regulatory Commission for its 1.7 Bcf/d Atlantic Sunrise expansion, which would deliver Marcellus Shale gas to Mid-Atlantic and southeastern markets (see Daily GPI, March 31).

Additionally, the Duke plan includes investing $320 million to build a transmission substation near Campobello, SC, and connect it to the Asheville plant with a new 40-mile, 230 kV transmission line. It also includes upgrading and rebuilding additional electrical infrastructure such as transmission lines and distribution substations.

Electricity demand in Duke Energy Progress' Asheville service area has doubled over the last four decades, the company said. The region currently must import about 400 MW during peak demand periods to ensure system reliability. The region's power demand is forecast to grow by about 15% over the next decade.

The Asheville coal plant is one of the company's few "must run" power plants, meaning it must operate to maintain reliability, even when it's not economical. This results in higher fuel costs that are passed on to North Carolina and South Carolina customers.

The new gas-fueled plant will be able to rapidly ramp up and down to meet voltage and power demand needs as they change throughout the day," the company said. Its combined-cycle technology will capture and convert exhaust heat into additional electricity, and is considered one of the most efficient power plant designs available.

"At today's natural gas prices, the gas plant would be about 35% less expensive to operate than the existing coal plant, saving customers money," Duke said. "Even with its expected higher operating levels, the gas plant is estimated to have significantly lower environmental impacts than the coal plant."

According to Duke, the plan will result in sulfur dioxide emissions reductions of 90-95%. Nitrogen oxide emissions will be cut by about 35% while mercury emissions will be completely eliminated. Withdrawals of water will be cut by 97%, and water discharges will decline by 50%, it said.

"Carbon dioxide emissions will be reduced by about 60%, on a per-megawatt hour basis, due to the efficiency of the new gas plant and the fact that natural gas burns more cleanly than coal," Duke said. "The new gas plant also will help reduce carbon dioxide emissions across Duke Energy's Carolinas power plant fleet."

Closing the Asheville coal plant and building a gas plant will make it unnecessary to invest in 126 MW of oil-fired generation units, to meet peak demand, and other capital investments that were planned for 2019, the company said.

Across the Duke Energy generation fleet -- regulated and nonregulated -- 42% of generating capacity is coal, 27% is natural gas, 28% is nuclear,1% is hydropower and 2% is wind, the spokesman said.

“We’re aggressively moving away from coal to natural gas for cost reasons and also environmental reasons...We’ll probably look at the ability to build more gas in the future, and renewables, too. We’re going to have some utility-scale solar on this site as well. We don’t have the number of megawatts defined yet or the cost, but we’ll be working on that.”

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