Frequently Asked Questions

Combined-cycle technology uses two processes. 

The first process includes a combustion turbine that operates like a jet engine that draws in outside air and compresses it to high pressure. The pressurized air mixes with natural gas and is then burned, creating hot exhaust gases. These gases power the combustion turbine, spin a generator and ultimately make energy.

The second process sends the hot exhaust gases from the combustion turbine to a heat recovery system. This system captures the heat from the hot exhaust gases to produce steam. This steam then goes to a steam turbine that rotates another generator and makes more energy.

Combined-cycle technology is highly efficient because of this heat recovery system. Without this system, all of the heat from the hot exhaust gases would be released to the atmosphere instead of being captured and used to generate steam and make more energy. 

Building highly efficient natural gas plants is part of the company’s balanced approach to meeting future demand for reliable and increasingly clean energy. We can build natural gas plants safely, quickly and less expensively than other energy generating sources. As a regulated utility, we are also required to provide the lowest cost energy option for customers. Investing in natural gas infrastructure will help us meet our customers’ energy needs today and in the future.

Natural gas-fired combined-cycle plants offer a variety of benefits to the environment and the energy 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 energy system
• Reduce environmental emissions, including nitrogen oxide and sulfur dioxide
• Add new, efficient intermediate gas-fired generation to our portfolio

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

These new facilities boost local economies in three main ways. The large construction work force, often 400 to 800 people, spends months or years living in these local communities investing in local hotels, restaurants, shops and recreation. Once the plant is operational, it becomes part of the local tax base, contributing to schools, emergency services and other governmental programs for decades to come. Employees work and live in these local communities, often giving back through volunteerism and financial contributions to nonprofit organizations.