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Jet Engines Dominate the Gas Turbine Industry, But other Sectors are Also Primed for Growth.

[+] Author Notes

Lee S. Langston, an ASME Fellow, is professor emeritus of the Mechanical Engineering Department at the University of Connecticut in Storrs. He was a member and a past chair of ASME's International Gas Turbine Institute.

Mechanical Engineering 133(05), 30-33 (May 01, 2011) (4 pages) doi:10.1115/1.2011-MAY-2

## Abstract

This article explores the increasing use of natural gas in different turbine industries and in turn creating an efficient electrical system. All indications are that the aviation market will be good for gas turbine production as airlines and the military replace old equipment and expanding economies such as China and India increase their air travel. Gas turbines now account for some 22% of the electricity produced in the United States and 46% of the electricity generated in the United Kingdom. In spite of this market share, electrical power gas turbines have kept a much lower profile than competing technologies, such as coal-fired thermal plants and nuclear power. Gas turbines are also the primary device behind the modern combined power plant, about the most fuel-efficient technology we have. Mitsubishi Heavy Industries is developing a new J series gas turbine for the combined cycle power plant market that could achieve thermal efficiencies of 61%. The researchers believe that if wind turbines and gas turbines team up, they can create a cleaner, more efficient electrical power system.

## Article

INSTALLED Workers eased MHI's 320 MWJ class gas turbine into a combined-cycle power plant in Japan.

Mitsubishi Power Systems Americas

Shale gas used to be a fairly obscure geological phenomenon. Indeed, a search through news stories archived by Google shows that as recently as 2005, the words shale gas appeared in only 157 published articles and press releases. Last year, however, shale gas broke through to the big time: Google's news archive has more than 6,000 articles, and a documentary about gas drilling was nominated for an Academy Award.

To be sure, not all the attention was positive. The documentary, for instance, focused on environmental damage attributed to the method for recovering shale gas known as hydraulic fracturing. And the word fracking was lifted from petroleum industry jargon to become something of a pejorative.

The recent rise of shale gas was, however, welcomed in the gas turbine industry. Thanks to abundant supplies of natural gas, the cost of the fuel remained relatively inexpensive—the average wellhead price hovered around $4 per thousand cubic feet for much of last year, less than half its price two years before. For gas turbines, an expansion in the natural gas industry, which has become a worldwide phenomenon not only because of shale gas in the U.S. but also the development of liquefied natural gas as a global commodity, will likely lead to growth in the mechanical drive gas turbine market. A natural gas pipeline needs roughly one gas turbine-driven compression station every 100 km to make up for the pressure losses. And a whole variety of mechanical drive gas turbines are needed in LNG trains, the very expensive, multipart facilities that cool and condense natural gas to a liquid phase. The latter is 600 times denser than gas and more easily transportable in special LNG tankers. Mechanical drive is just a sliver of the industry right now —accounting for just$2.2 billion in production in 2010, according to Forecast International in Newtown, Conn., out of a worldwide total of $42.1 billion for gas turbines of all sorts. Forecast International is able to cover the recent production record of the gas turbine industry for both the aviation and non-aviation sides—the two disparate parts of the industry that are usually reported on separately in trade journals. Using FI's extensive data base and computer models, analyst Bill Schmalzer is able to calculate gas turbine market data in terms of the 2010 dollar value of production (considered more accurate than sales figures) for 1995-2010, as well as FI's projections to 2015. The$42.1 billion value of production for all gas turbines in 2010 was 2.6 percent higher than 2009, and 15 percent higher than a 10-year average of $36.8 billion. Clearly, the FI value of production figures do not show a strong effect of the 2008 Great Recession, and FI predicts the industry will exceed$56 billion in production value by 2015. If so, that will smash through the current record for production, $48.9 billion in 2001. As usual, the aviation sector represents the largest slice of the gas turbine market for 2010. The value of production for commercial aircraft engines was$21 billion, while the value for military aircraft engines was $5.5 billion. The total sector was down slightly from 2009 levels, but FI's forecast, which is based strongly on existing aircraft orders, predicts strong growth ahead, up to$39 billion in 2015. All indications are that the aviation market will be good for gas turbine production as airlines and the military replace old equipment and expanding economies such as China and India increase their air travel.

The most lucrative market for engine manufacturers is twin-engine, single-aisle narrow body jets. Boeing's 737 and Airbus's A320, powered by 30,000 lbt engines from CFM International (a collaboration of General Electric and Snecma) and International Aero Engine (a venture of Rolls-Royce, Pratt & Whitney, MTU, and JAEC) number in the many thousands. The big news of 2010 for this important segment of the engine market, was an announcement by Airbus to offer a new version, the A320neo—“neo” short for “new engine option.” On this re-engined passenger aircraft, Airbus will offer a choice of the new fuel-efficient engines: the LEAP-X from General Electric/Snecma or Pratt & Whitney's PW1100 geared turbofan. Each of those new engines promises a fuel burn reduction of around 15 percent—a very attractive feature for the airline industry, which can have as much as 60 percent of its operating costs spent on fuel.

As I write this, Airbus has substantial orders from Virgin America, Brazil's TAM, and India's new airline, IndiGo, for deliveries starting in 2016. International Lease Finance Corp., which leases aircraft to such airlines as Southwest, Delta, American, and Jet Blue, has ordered 60 A320neo aircraft with the Pratt geared turbofan engine.

FAST RESPONSE: The Mill Creek station in Montana backs up a wind farm.

Photo: Pratt & Whitney

Boeing is standing firm in its plan to offer a newly designed 737 in 2020, but gas turbine industry analysts are waiting to see if Boeing will bend to Airbus competition and offer a re-engined 737 before then.

Production of jet engines for military aircraft in 2010 increased 20 percent over 2009's levels. Although in size it is a factor of four smaller than commercial aviation, gas turbine companies eagerly seek military contracts because of their long-term stability and the need for engine technology that pushes the envelope—which can bear fruit for new advances and developments in commercial engines.

For instance, the Joint Strike Fighter, the Lockheed Martin F-35, has the 40,000 lbt F135 engine, now in production by Pratt & Whitney. It can operate with turbine inlet temperatures in the 3,600 °F range, higher than the boiling point of molten silver. The cooling techniques developed for the F135 may someday improve performance and durability of commercial engines.

Some analysts estimate that the JSF program will require between 3,000 and 4,000 engines. The General Electric/ Rolls Royce Fighter Engine Team has been developing an alternate JSF engine, the F136, but recent actions by the U.S. Congress and the administration have canceled funding. That leaves Pratt & Whitney as the sole source for powering this remarkable aircraft.

Pratt & Whitney is also the behind-the-headlines winner in the battle to replace the 1950s-era KC-135 aircraft, which conduct aerial refueling missions for the Air Force. Boeing received a $35 billion contract for 179 aerial refueling tankers, to be derived from the company's 767. To power those tankers, Pratt & Whitney will supply some 400 PW4062 engines. The other market segment, gas turbines for non-aviation uses, had a value of production of$15.6 billion in 2010, according to Forecast International. That's a 14 percent increase over the year previous. Within that segment, gas turbines for marine power had a production value of $442 million, and$2.2 billion in turbines for mechanical drives were produced.

By far the largest sub-segment was electrical power gas turbines, which accounted for \$12.9 billion in 2010. Gas turbines now account for some 22 percent of the electricity produced in the U.S. and 46 percent of the electricity generated in the United Kingdom. In spite of this market share, electrical power gas turbines have kept a much lower profile than competing technologies, such as coal-fired thermal plants and nuclear power.

Gas turbines are also the primary device behind the modern combined power plant, about the most fuel-efficient technology we have. 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. Modern gas turbine combined cycle power plants are producing electric power as high as half a gigawatt with thermal efficiencies approaching 60 percent—almost twice the efficiency of the steam power plants of yesteryear.

The largest combined cycle gas turbines in operation are the H class machines made by General Electric and Siemens. A new Siemens H class gas turbine, the SGT-8000H, rated at 375 MW making it the world's largest gas turbine, has undergone tests at Irsching, Germany. It is the heart of a new 570 MW combined cycle plant, slated to go into operation in the fall, and designed to exceed 60 percent thermal efficiency.

Mitsubishi Heavy Industries is developing a new J series gas turbine for the combined cycle power plant market that could achieve thermal efficiencies of 61 percent. One key to this advance is higher inlet turbine temperature:

Electric power gas turbines can typically run at about 2,700 °F, while commercial aviation gas turbines reach 3,000°F at takeoff. MHI is testing a J series turbine this year that will operate with an inlet turbine temperature of 2,912 °F—closer to a jet engine than a typical power plant gas turbine. The company plans to follow with another J series that will have a turbine temperature at 3,092 °F, 1,700 °C, with the hope of reaching 62 to 64 percent combined cycle efficiency.

One of the most intriguing markets for electric power gas turbines has to do with wind and gas. There has been a boom in recent years in wind turbine installations to generate electric power, using the wind as a renewable source of energy. Large wind turbines in the 500 kW to 8 MW output range are being installed worldwide. At present, wind generates less than 1 percent of U.S. electrical power, while in Germany as much as 6 percent is supplied by an extensive wind turbine system.

One drawback to wind turbine electric power is that it is “non-dispatchable”—that is, it is not capable of being turned on and off or increased or decreased on demand, such as hydroelectric or gas turbine generation. Wind turbine power is termed an “intermittent renewable” source of electric power, available when the wind blows, and variable even then. Wind turbine power generation occurs between the cut-in-speed—the lowest velocity at which useable electric power is generated, usually 3 to 5 m/s—and the cut-out speed, some 25 to 30 m/s, beyond which the wind turbine may be damaged. (See the December 2009 article, “Fitting a Pitch,” for a discussion of how these limits are controlled by varying the pitch of the wind turbine blades.)

As an example of the fast swings in power production from wind farms, NorthWestern Energy in Montana has reported that its farm at Judith Gap can ramp up from zero to 131 MW in 10 minutes—and ramped down from 121 MW to zero in a similar time.

Efficient: CFM International's LEAP-X engine (left and, under testing, above) will be offered on the Airbus A320neo.

To mitigate against such variability, NorthWestern Energy has installed six Pratt & Whitney Power Systems FT8 gas turbines, each at 25 MW and a 38 percent simple cycle thermal efficiency, at the Mill Creek Generating Station as “regulating capacity,” with a call for power on a second-by-second basis. The turbines give the utility a backup support of 150 MW to the wind farm.

The FT8 is derived from P&W's JT8D jet engine. It burns natural gas (with fuel oil as a backup) and can be brought from a cold start to full power in ten minutes, with ramp up or down at a rate of 15 MW per minute.

In a similar hedge against daily and seasonal variability, Westar Energy in Topeka, Kansas, has a 665 MW gas turbine power plant at the Emporia Energy Center for year-round support of 800 MW of wind farms, according to Bill Owen in the September-October 2010 issue of Gas Turbine World. Owen reported that as a general rule, Westar's wind farms produce about 40 to 45 percent of nameplate power early in the morning, drop off to a little over 20 percent by mid-day, and rise back up to again to about 40 percent in the late afternoon and evening. To provide for wind power variation, grid stabilization and system peaking demands, the 665 MW gas-fired dispatchable power plant uses four GE LM 6000 aero-derivatives (each one rated at 37 MW) and three GE 7FA (172 MW each) heavy frame gas turbines.

With the growing availability of natural gas and the environmental appeal of wind power, such combined operations would seem to have a bright future. If 2010 was the year of shale gas, the coming decade may well be one where wind turbines and gas turbines team up to create a cleaner, more efficient electrical power system.

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