Questions & Answers

A combined-cycle generating plant primarily uses combustion turbine generators, heat-recovery steam generators (or boilers), and steam turbine generators to convert natural gas fuel to electricity. Natural gas is burned in the combustion turbines to produce mechanical power that is converted to electric power by the generators. For increased efficiency, the hot exhaust gases resulting from this combustion process are routed through the boiler, which produces steam and additional electricity. Combined-cycle units offer greater efficiency than traditional combustion turbines, and their operational flexibility is vital in supporting intermediate load demand.

Duke Energy has a robust planning process that projects long-term demand and builds plants if needed to meet future customer needs. Although the recessionary economy has impacted our near-term load, we must prepare for the future when demand growth returns. Regardless of the recession, we will need additional capacity to meet our peak demand in the future. The newer units we are building will replace the older fossil plants we anticipate retiring over the next decade. We also continue to aggressively pursue renewable power sources and energy efficiency programs to complement our efforts to modernize our power plants.

Natural gas-fired combined-cycle plants offer a variety of benefits to the environment and the electric system. Combined with the retirement of older, less efficient coal-fired units, the projects:

• Increase fuel supply diversity
• Add generation in more remote parts of the Duke Energy service area to reinforce the electric system
• Reduce environmental emissions, including nitrogen oxide (NO_x) and sulfur dioxide (SO₂)
• Add new, efficient intermediate gas-fired generation to the Carolinas portfolio.

There are a number of uncertainties as Duke Energy plans for the future, including fluctuating fuel prices and potential carbon regulation. In either case, there is upward pressure on energy prices. Modeling shows continued fuel diversity including additions of natural gas-fired generation is the least-cost option to meet customer demand for electricity.

No, the new plants will use natural gas only. We evaluated dual fuel, but oil is not economical for intermediate load generation. Dual fuel is often provided at smaller peaking plants where fuel oil is required only a few days out of the year to meet high-demand periods.

These new facilities boost local economies in two ways. The large construction work force, often 400 to 800 people, spend months or years living in these local communities—investing in local hotels, restaurants, shops and recreation. Once the plant is complete, it becomes part of the local tax base, contributing to fund schools, emergency services and other programs for decades to come.