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Stuart Hampton

Combined Cycle: The Natural Gas Power Plant Revolution

by Stuart Hampton | Dun & Bradstreet Editor

July 29, 2015 | No Comments »

Turbine-GE_1100pxIn 2015 electric generating companies expect to add more than 20 gigawatts (GW) of utility-scale generating capacity to the US power grid. While these additions are dominated by wind (9.8 GW), natural gas is not far behind at (6.3 GW), followed by solar (2.2 GW).

The ramp-up of greener power production is on pace to more than replace the nearly 16 GW of generating capacity that is expected to retire in 2015, 81% of which is coal-fired generation.

While wind and solar attract the most attention as the renewable energy sources that are replacing the dirty coal-fired plants, the real shining star in the power generation industry’s transition from dirty fuel sources to cleaner ones is natural gas combined-cycle generators, which have utilization factors three to five times those of wind and solar generators.

Combined-cycle natural gas power plants are quickly becoming the new workhorses of the US power generation fleet by revolutionizing how electricity is produced.

Natural gas plant additions in 2015 are spread throughout the country, but Texas is adding more than double any other state (1.7 GW, 27% of total natural gas additions). There are also many new plants in the mid-Atlantic region, with more than 26% of total natural gas additions expected in Delaware, Maryland, New Jersey, and Pennsylvania.

According to a recent ANGA blog post, power generation has remained largely unchanged since 1882. The process used by the first centralized power plant in the US (New York’s Pearl Street Station) and still used by most plants in operation today involves boiling water, capturing the steam, and channeling it through a generator to produce electricity. The problem is that efficiency levels for the coal plants that use this single steamed-based process range from only 32% to 40%.

By contrast, natural gas combined-cycle power plants greatly improve the efficiency of power generation by using two processes. Instead of using natural gas to boil water, it is first used to power a jet engine-like turbine that directly turns a generator to produce electricity.

In addition, heat from that combustion process is also captured and used to boil water, create steam, and drive a second generator. This means that a combined-cycle plant is generating electricity from one natural gas source but in two cycles, and achieving efficiency levels of more than 60%.

With the promise of reduced emissions and increased fuel savings, utilities are lining up to order the giant gas turbines made by the likes of Siemens, Alstom, and General Electric.

In July 2015 Bechtel broke ground on a new 700-MW natural gas-fired combined-cycle power plant in Carroll County, Ohio, for Carroll County Energy, LLC.

In 2014 Florida Power and Light began operating a new combined-cycle plant at its Riviera Beach location.

According to industry analyst Black & Veatch, combined-cycle power plants accounted for 21% of the electricity generated in 2014. The analyst projects that these plants will account for some 38% of total US generation by 2038.

It may not be as green as wind, solar, or hydro, but natural gas, used in combined-cycle power plants, is a cleaner and powerfully more efficient alternative to the country’s aging coal-powered plants.

British editorial veteran Stuart Hampton has been covering oil and gas companies for Hoover’s since the Neogene-Quaternary period. Well, actually, since the early 1990s. For the best overview of the oil industry and its history, he recommends Daniel Yergin’s The Prize. You can also follow Stuart on Twitter.


Photo courtesy of GE.

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