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Gas-fired generation is projected to grow 3.1 percent a year through 2038.

By Russell Ray, Managing Editor

Combined cycle power plants are highly efficient, allowing power producers to wring much more power from the same amount of natural gas. The energy conversion rates for combined cycle gas turbine (CCGT) plants are high, ranging from 50 to 60 percent.

Natural gas-fired generation is projected to grow 3.1 percent a year through 2038, adding 348,000 MW of gas-fired capacity to the U.S. grid, according to a report from Black & Veatch. Most, if not all, of that capacity will be met with CCGT technology. Natural gas-fired combined cycle plants are expected to account for 50.5 percent of U.S. power production by 2038, up from 25 percent this year, according to the report. By 2038, coal’s share of the generation pie will drop to 21 percent, down from 39 percent in 2014.

The transition to CCGT technology is being driven by low gas prices, stricter regulation for coal plants, and the integration of growing amounts of renewable power. Combined cycle plants compliment wind and solar power because they can start and stop quickly, and thus are capable of offsetting the fluctuations in renewable power.

Combined cycle power plants feature gas and steam turbines. The gas turbine generates electricity using natural gas, while the steam turbine generates electricity using waste heat from the gas turbine. The process is highly efficient because the exhaust heat, which would otherwise be lost in the stack, is re-used in the steam turbine to generate additional electricity.

What follows is a description of a handful of combined cycle projects under some stage of development in the U.S.

CB&I to build combined cycle project in Indiana

In June, CB&I was awarded a $500 million contract from Indianapolis Power & Light (IPL) for the engineering, procurement and construction of a combined cycle plant near Martinsville, Indiana.

The 671-MW unit will be built next to the existing Eagle Valley coal-fired power plant. In May 2013, the utility said it plans to close six units at Eagle Valley.

IPL also selected General Electric’s 7FA.05 series gas turbine for the new unit. Engineering and procurement for the combined cycle project is under way. On-site construction is expected to begin in 2015. The project is expected to be completed in 2017.

In May, state regulators in Indiana approved the utility’s request for a Certificate of Public Convenience and Necessity, allowing IPL to invest $600 million in a new combined cycle project and $36 million to convert Units 5 and 6 at the Harding Street Generation Station from coal to natural gas.

Marshalltown plant under construction

Alliant Energy’s Interstate Power and Light recently started construction of a 650-MW combined-cycle plant known as the Marshalltown Generating Station (MGS) in Iowa. Commercial operation is expected to begin in the second quarter of 2017.

“Construction of MGS is a key part of our company’s long-term energy resource plan that further balances our energy supply while reducing emissions,” said John Larsen, senior vice president of generation for Alliant Energy.

KBR was selected as the project’s engineering, procurement and construction contractor.

The project is part of a long-term, multi-billion dollar plan to meet customer demand and reduce emissions.

Dominion building project in Virginia

Dominion Virginia Power is building a $1.3 billion, 1,360-MW combined cycle power plant in Brunswick County, Virginia.

Construction began in September. The project is on budget and on schedule to be completed by summer of 2016, Dominion said. Fluor Corp. is the engineering and procurement services provider for the project.

The Brunswick County plant will use natural gas to fire three combustion turbines to produce 810 MW. The excess heat will be captured and used to produce 550 MW from a steam turbine. The gas-fired generation will replace power from old coal-fired plants that are being retired for economic and environmental reasons.

Panda Liberty to power 1 million homes

Panda Power Funds is building an 829-MW combined cycle power plant in the heart of the Marcellus Shale gas play in Pennsylvania to take advantage of low gas prices, abundant supplies and low transportation costs.

The Panda Liberty project is under construction in Bradford County, Pennsylvania, and will be able to generate enough electricity to power 1 million homes in the region.

Officials broke ground on the project in May. Commercial operation is expected to begin in 2016.

The combined cycle plant will use Siemens SGT6-8000H-class gas turbines, the first generation technology to achieve operating efficiencies of 60 percent. What’s more, the plant will be cooled with air, not water.

Gemma Power Systems and Lane Construction were selected to provide engineering and procurement services for the installation, construction and commissioning of the project. Burns and Roe is the design engineer for the project.

Plans to retire more than 20 GW of coal-fired power in the PJM (Pennsylvania, New Jersey and Maryland) market have been announced. Power plants that account for more than 70 GW are 56 years old, on average.

CC project under construction in Anchorage

Anchorage Municipal Light & Power (ML&P) is building a 120-MW combined cycle power plant in Anchorage, Alaska.

The George M. Sullivan Plant 2A Expansion Project is a 2×1 combined cycle configuration using General Electric’s LM6000 combustion turbine technology.

The $225 million project is expected to be completed in the summer of 2016. In addition to a significant reduction in the use of natural gas, the project will cut NOx emissions by 97 percent CO emissions by 80 percent.

The project is expected to save the utility more than $13 million a year in gas costs.

Stantec was selected by Quanta Power Generation, the EPC contractor, to provide engineering and design services for the project.

“This plant will be a great example of how to combine traditional power generation with efficient and effective modern techniques,” said Bill Shelley, vice president of Stantec’s U.S. power practice.

TVA building CC plant in central Kentucky

The Tennessee Valley Authority is replacing its two oldest coal-fired units at the Paradise Fossil Plant in central Kentucky with a high efficiency, combined cycle plant fueled with natural gas.

The $1 billion project, which will replace Paradise units 1 and 2, is expected to be completed in 2017 and will be capable of generating up to 1,000 MW.

“A combined cycle gas plant at Paradise will help ensure power system stability and reliability in the northern-most part of our service area while meeting environmental regulations,” said TVA President Bill Johnson.

The new high efficiency, combined cycle plant will be similar to TVA’s John Sevier combined cycle plant, which was fully commissioned in April 2012.

TVA has bought or built five combined cycle power plants since 2007.

NTE Energy to build $450 million project in North Carolina

Construction of the Kings Mountain Energy Center, a 480-MW combined cycle project in North Carolina, is expected to begin next year, with a targeted completion date of 2018.

NTE Energy will develop, own and operate the $450 million project. The plant will use a M501GAC combustion turbine and a steam turbine from Mitsubishi Hitachi Power Systems Americas.

The project is expected to employ more than 300 people during construction and about 30 once the plant is up and running. It will generate enough electricity to power 400,000 North Carolina homes.

Adding capacity to Polk Power Station

Tampa Electric plans to build a 460-MW combined cycle power plant in central Florida.

The utility secured a greenhouse gas (GHG) permit from the Environmental Protection Agency in January. The $700 million project will convert the four existing simple-cycle gas units at Polk Power Station to a 4×1 combined cycle configuration. The project is expected to be completed by January 2017.

The project will increase the capacity of these units from 660 MW to 1,160 MW. The modifications will feature four 7FA.03 combustion turbines from General Electric, four heat recovery steam generators and a steam turbine.

The GHG permit requires the use of “Best Available Control Technology” to limit GHG emissions. The project would create about 500 jobs at the peak of construction. The expansion is needed by 2017 to accommodate customer growth and to replace purchased power agreements due to expire.

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