Q&A: Duke on transmission lines

Duke Energy has announced that it will construct a substation in Campobello, South Carolina, and a 230-kilovolt transmission line that will deliver power to a planned natural gas-fired plant near Asheville. The 40- to 45-mile line will import power from a substation located near the Oconee nuclear plant.

The decision has drawn the ire of thousands of property owners from the Upstate to South Asheville, outraged that 140-foot tall towers strung with power lines might cross their land, mar scenic views and cause environmental problems.

The Asheville Citizen-Times asked Tom Williams, director of external relations for Duke, about some of the issues that most trouble area residents. Some answers include information from previous statements by Duke officials or the company's website www.duke-energy.com/western-carolinas-modernization.

Question: Why does the Asheville area need energy imported from another region?

Answer: The region's power consumption has doubled since the 1970s, and peak needs in hot and cold weather are showing bigger swings. "We have to be prepared to meet these extreme weather events on the system or we have reliability problems and have to do structure-rotating blackouts," Williams said.

Q: The proposed natural gas-fired power plant at Lake Julian will be about 650 megawatts. The existing coal-fired plant it will replace is 376 megawatts. Why isn't that extra power enough?

A: The Lake Julian facility is also home to two combustion turbines, which can produce another 324 megawatts of peaking power. Before the natural gas announcement, Duke had planned to add another 120 megawatts of less efficient diesel-fired peaking power to meet demand. Those plans have been canceled.

Q: Duke is already planning to build a natural gas-fired power plant at Lake Julian. Why doesn't Duke build a bigger facility and drop the transmission lines?

A: The design is a "package," Williams said. Waste heat is driven off two powered jet engines, put through a steam turbine, which feeds a third energy turbine. "We would have to upsize the gas line or build twice the plant. We've already been criticized for building the plant too big. In a nutshell, the current plant presents by far the best economy of scale."

Q: Has Duke considered using solar energy to bridge the power needs?

A: The site of the coal plant will be home to a solar farm, its size not yet determined. Large-scale solar power isn't a pragmatic option for a mountainous region and won't be reliable enough to meet demands when energy needs peak on the hottest summer days or coldest winter nights.

Q: Instead of creating routes in forested areas or near homes, why doesn't Duke use existing transmission lines and rights-of-way?

A: Some potential routes do include existing paths, but varying kilovolt lines have different right-of-way requirements. "You can't run a 230-kilovolt line on a 100-kilovolt tower. The towers are specifically designed to serve the weight of the wire, the ice load on the wire, the topography based on the turns on the wire," Williams said. "We have looked at where we can bundle existing wires together on existing lines, and we are considering that seriously. We would much rather add capacity to an existing 230-line than build a whole new right-of-way. We do that whenever we can. It's significantly less expensive and less intrusive."

Q: Will Duke look at burying the transmission lines?

A: Duke has only one underground 230-kilovolt line, constructed because the company has no other option in that case. It runs for a short distance in St. Petersburg, Florida, Williams said. The company will look at burying the line once a route is established, but past analysis of other projects shows that option is cost prohibitive and raises its own environmental concerns.

Q: What happens next?

A: Duke will take into consideration comments gathered though various means, including at a series of three recent public meetings and those submitted online at www.dukeenergyfoothillsproject.power-viz.com. Officials expect to select a route by September and will seek approvals and permits. Construction is set to begin in 2017.