Duke Energy, Siemens team up on advanced natural gas project

Go behind the scenes during construction of Duke Energy’s newest natural gas combustion turbine

Inside the massive Siemens Charlotte Energy Hub, technicians are building a 402-megawatt natural gas turbine to serve more than 300,000 Duke Energy customers in the Carolinas.

The unit’s engine, generator and main components weigh about four times more than a space shuttle and would snuggly fit inside an Olympic swimming pool. Some components are thinner than a sheet of paper, and others are made with lasers and robots.   

At the Siemens Charlotte Energy Hub, technicians Gordon Tomberlin, left, and Kim Wilson assembled and inspected the generator’s stator, the stationary part of the rotating system.

As part of an innovative agreement, Siemens will build and test its newest natural gas combustion turbine technology, the SGT6-9000HL, at Duke Energy’s Lincoln Combustion Turbine Station near Denver, N.C., about 25 miles north of the Siemens manufacturing plant.

Duke Energy customers will receive all of the unit’s energy during a four-year testing period while only paying some fuel costs. When testing is finished in 2024, the company will receive the unit at a discount. 

“Natural gas technology has broad and significant benefits for everyone both economically and environmentally,” said Richard McMahon, senior vice president for energy supply and finance at Edison Electric Institute. “This technology will produce cleaner energy more efficiently and help back up renewables like wind and solar.”

The generator is expected to arrive at Duke Energy’s Lincoln station this spring, and crews will later connect it to the combustion turbine. Natural gas fuels the turbine, which spins the generator and ultimately makes electricity.

The unit is based on four generations of technologies and five previous models, starting with the SGT-2000E in the 1980s. The new unit is designed to last longer before maintenance is required and will be the most efficient of its type in Duke Energy’s fleet. This efficiency means customers get more energy for the same fuel cost.

“Every decade, we have a significant technology jump,” said Siemens’ Manager Peter DeHaan, who is leading development of the 9000HL. “We’ve taken the best DNA from each of our previous models and made the HL the most powerful and most efficient.”

Investing in this technology represents one of Duke Energy’s most innovative projects. Utilities usually do not invest in new technology during the testing phase.

Technician Kevin Batson prepared a disc for the combustion turbine.

“We’re getting a state-of-the-art unit at a great price,” said Duke Energy Project Director Gary Thompson. “When we save money, our customers save money. To me, that’s a good deal.” 

A combustion turbine generator operates like a jet engine, drawing in and compressing outside air to a high pressure.

The pressurized air mixes with natural gas and then burns, creating hot exhaust gases. These gases power a turbine, spin a generator and ultimately make electricity.

What makes the Siemens’ combustion turbine advanced is the way it burns fuel, coupled with the shape, aerodynamics and thermal dynamics of its blades.

During testing, experts will observe how the engine expands and contracts and monitor emissions like sulfur dioxide and nitrogen oxides. Technicians will listen to the frequency of the turbine’s blades. Like a bell, each blade has a unique sound. If one is not performing well, workers will hear it.

The natural gas must burn hot – more than 2,900 degrees Fahrenheit – but not so hot that it melts parts. And the space inside must be compact.

“The combustion system is where the magic happens,” said DeHaan. “It consumes natural gas as hot and uniformly as possible, while aerodynamic blades move air like a canoe paddle moves water – but really fast.”


Because the heat is like a continuous blow torch, the unit has coatings and ceramics to prevent the blades from melting. Cooling air also protects the blades and helps them perform.

This type of unit can start quickly, so the 9000HL will give Duke Energy more flexibility to support its growing portfolio of solar generation to meet customers’ needs when the sun isn’t shining.

“The new unit will help us fill in the gaps and continue our plan to close coal-fired units,” said Thompson. “Natural gas is competitive and helps us manage carbon emissions.”