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# Gas Turbines and Natural Gas SynergismPUBLIC ACCESS

[+] Author Notes
Lee S. Langston

Professor Emeritus of Mechanical Engineering, University of Connecticut

Mechanical Engineering 135(02), 30-35 (Feb 01, 2013) Paper No: ME-13-FEB4; doi: 10.1115/1.2013-FEB-4

## Abstract

This article presents a study on new electric power gas turbines and the advent of shale natural gas, which now are upending electrical energy markets. Energy Information Administration (EIA) results show that total electrical production cost for a conventional coal plant would be 9.8 cents/kWh, while a conventional natural gas fueled gas turbine combined cycle plant would be a much lower at 6.6 cents/kWh. Furthermore, EIA estimates that 70% of new US power plants will be fueled by natural gas. Gas turbines are the prime movers for the modern combined cycle power plant. On the natural gas side of the recently upended electrical energy markets, new shale gas production and the continued development of worldwide liquefied natural gas (LNG) facilities provide the other element of synergism. The US natural gas prices are now low enough to compete directly with coal. The study concludes that the natural gas fueled gas turbine will continue to be a growing part of the world’s electric power generation.

## Article

New electric power gas turbines and the advent of shale natural gas are upending electrical energy markets. Historically, coal-fired Rankine cycle power plants have been the most cost effective way to generate dispatchable electric power. Coal has been the cheapest fuel, used to drive steam turbines to power electric generators. Until recently, coal plants have provided about half of US electrical power.

Brayton cycle gas turbine electrical power plants, although much cheaper to build and fueled by much cleaner natural gas (for equal energy, coal combustion produces more harmful emissions and almost 100 percent more CO2 than natural gas’s methane) have been more expensive to fuel.

But now that picture is changing with electric power gas turbines predicted to become the dominant prime mover for dispatchable electric power plants in the US. In its Annual Energy Outlook 2012,[1] the US government’s Energy Information Administration (EIA) presents estimates of the averaged levelized costs for generating technologies brought online by 2017. (Levelized cost represents the per-kilowatt hour cost of building and operating a generating plant over an assumed financial life and duty cycle.)

EIA results show that total electrical production cost for a conventional coal plant would be 9.8 cents/kWh, while a conventional natural gas fueled gas turbine combined cycle plant would be a much lower 6.6 cents/kWh. (Advanced nuclear is 11.1 cents/kWh.) An advanced gas turbine combined cycle plant (more on this later) would have a total system levelized cost of 6.3 cents/kWh—some 36% lower than King Coal!

Furthermore, EIA estimates that 70 percent of new US power plants will be fueled by natural gas. They calculate that as a fuel, natural gas (and hence gas turbines) increases its percentage of electrical generation in the US to 31% in 2012, up from 21% in 2008, with further increases predicted beyond 2012.

Many of us know that gas turbine power plants fueled by natural gas are also fitting into non-dispatchable renewable electric systems (e.g. wind turbine farms and solar power plants) like hand in glove. When the wind doesn't blow (or blows too hard) or the sun doesn’t shine, fast-starting gas turbine plants supply electrical power as a backup or supplement, to fulfill power contracts and needs.

Just what combination of factors is bringing about this new-found dominance of natural gas fueled, gas turbine power plants? It is a synergism brought about by the relatively new technology of combined cycle power plants, and the new technology of horizontal well drilling and down-hole well fracturing in shale beds, that is significantly increasing natural gas production in the US.

Gas turbines are the prime movers for the modern combined cycle power plant (more accurately, a combined power plant because the thermodynamic cycles aren’t combined, but separate). The hot exhaust of a Brayton cycle electric power gas turbine is used to produce steam to drive a Rankine cycle electric power steam turbine, thus using one unit of fuel (generally natural gas) to supply two sources of electric power. These superstar power plants are generally in the 100 to 600 MW range, with overall thermal efficiencies in the 50-60 percent range.

In May 19, 2011, Siemens announced that their new combined-cycle unit at Irsching, Germany had reached a thermal efficiency of 60.75 percent, with an electrical output of 578 MW[2]. This would probably make it the most efficient heat engine ever operated. These advanced combined cycle plants are being developed by General Electric, Mitsubishi and Alstom, as well as Siemens, with targets of up to 65 percent efficiency.

On the natural gas side of the recently upended electrical energy markets, new shale gas production and the continued development of worldwide liquefied natural gas (LNG) facilities provide the other element of synergism.[3] Two years ago I wrote in this column that gas turbines had a bright future based on the promise if abundant natural gas.[4] Now that has come to pass!

Recent exploration in the U.S. has produced very large finds of unconventional natural gas. (Natural gas occurring with an oil well is termed “conventional”.) By using new drilling (horizontal as well as vertical) and hydraulic fracturing techniques (termed fracking in the petroleum industry), extensive deposits of natural gas are being piped out of underground shalebeds in the eastern and southern U.S., apparently enough to supply the counry for many years to come. Large deposits occur in the Marcellus and Utica Shale Formations underlying Pennsylvania, New York, West Virginia and Ohio, close to major markets and pipelines.

The new shale gas has driven the US natural gas prices down to the $2-3 per million BTU range (Henry Hub prices) in 2012, contrasted to a high of about$13 in 2008. Currently the price of natural gas wouldwide is about $8 per million BTU in the UK and is in the$15 range for LNG in Japan. (In 2012, Japan was buying about one third of the world’s LNG, to make up for the power losses in their nuclear power plant shutdown after the 2011 Fukushima incident.)

The US natural gas prices are now low enough to compete directly with coal. For instance, here in New England, in 2009, 15% of electric power was coal produced. In 2012 it was only 3%, supplanted by natural gas fueled gas turbine plants.

Thus, we can safely conclude[4] that the natural gas fueled gas turbine—be it the heart of a super efficient combined cycle base load electric power plant or be it a quick start supplemental power plant to back up renewable electric systems—will continue to be a growing part of the world’s electric power generation.

## References

“Levelized Cost of New Generation Resources in the Annual Energy Outlook 2012”, EIA, July 2012, <>.
Langston, Lee S., 2012, “Breaking the Barriers”, Mechanical Engineering Magazine, May, pp. 32-37.
Nicholls, Tom, Editor, 2012, “Everything you wanted to know about gas: - but were afraid to ask”, Silverstone Connunications Ltd., ISBN: 978-0-9555409-7-4.
Langston, Lee S., 2010, “A Bright Natural Gas Future”, Global Gas Turbine News, February, p.3.
View article in PDF format.

## References

“Levelized Cost of New Generation Resources in the Annual Energy Outlook 2012”, EIA, July 2012, <>.
Langston, Lee S., 2012, “Breaking the Barriers”, Mechanical Engineering Magazine, May, pp. 32-37.
Nicholls, Tom, Editor, 2012, “Everything you wanted to know about gas: - but were afraid to ask”, Silverstone Connunications Ltd., ISBN: 978-0-9555409-7-4.
Langston, Lee S., 2010, “A Bright Natural Gas Future”, Global Gas Turbine News, February, p.3.

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