a year of turbulence
After a year of sharp decline in orders in the electric power industry, there's a prediction of clear skies ahead.
By Lee S. Langston
There
is an old movie cliché about the dashing male boss ignoring the attractiveness
of his efficient and available female secretary. If one were to anthropomorphize
technologies, you could see plenty of parallels between that overlooked
assistant and the gas turbine.
In the aftermath of a spike in natural gas prices and in the face of record
gasoline prices, there is a renewed interest in energy (really, energy
conversion), hydrocarbon fuel depletion, and mankind's possible
role in global warming.
Two new and very good books on these topics—Power to the People
by Vijay Vaitheeswaran and Out of Gas by David Goodstein—present
a very favorable picture for the possibility of a "hydrogen economy"
and widespread energy conversion based on yet-to-come fuel cell technology.
But neither author pays much attention to the revolution already occurring
in pollution reduction and in improved energy conversion, brought about
by the use of new gas turbines and combined-cycle electric power plants.
It has been that sort of year in the gas turbine industry. Even when steady
increases are being made, the headlines are more likely to emphasize the
negative and pine for some new alternative.
And that's a shame. Gas turbines are one of the most efficient—even
green—technologies around. In recent years, land-based gas turbines
have utilized some of the newest jet engine technology to improve thermal
efficiency (to as high as 40 percent) and reduce emissions.
New combined-cycle power plants, in which exhaust heat from a gas turbine
driv- ing an electrical generator is used to make steam to power a separate
turbine driving yet another electrical generator, can see efficiencies
as high as 58 percent, close to the idealized maximum. This represents
an almost doubling of thermal efficiency compared to older conventional
power plants, with a very significant reduction in fuel use and a reduction
of emissions for a given power output.
Technological advances haven't slowed, either. Solar Turbines announced
the commercialization of its Mercury 50 recuperated gas turbine system.
The Mercury 50 is a compact, 4.6-megawatt machine that is an outgrowth
of the U.S. Department of Energy's Advanced Turbine System program.
It is also the first electric power gas turbine to have been specifically
designed around a recuperator, which is a heat exchanger that transfers
heat from the turbine exhaust to air entering the combustor, and helps
to raise the unit's thermal efficiency to 38.5 percent.
General Electric will introduce its new LMS100 electric power gas turbine
to the market in 2005. It is rated at 100 MW and will have the highest
thermal efficiency of any simple cycle gas turbine, at 46 percent. The
LMS100 makes use of an intercooler, a first for a modern production electric
power gas turbine. The intercooler is a heat exchanger mounted between
the high and low compressor, cooling gas path flow. This results in less
compressor work, increasing the work output and providing for colder cooling
air for the hot turbine, boosting thermal efficiency.
A New
Fact of Life
The high thermal efficiencies of both of these new gas turbines are partial
answers to a new fact of life in 2003: higher natural gas prices. In the
recent past, the U.S. price of natural gas had been fairly steady, between
$2 and $3 per million Btu, but last year, the price rose to $5 to $6 per
million Btu. This spike has led to shutdowns of some gas-fired electric
power plants as the gas became more valuable than the electricity produced.
Experts do not see natural gas prices coming down in the short term.
A long-term answer is to promote the liquefied natural gas market. Proven
worldwide reserves of natural gas exceed those of oil, on an equivalent
energy basis. In liquefied form, natural gas can be more easily transported
anywhere in the world than in its gas phase, and thus becomes a fungible
commodity, like oil. But creating an LNG infrastructure requires a large
capital investment in equipment and a stable natural gas price (some estimate
$3 to $5 per million Btu).
Studies done by ExxonMobile predict that more than 40 percent of the worldwide
demand for natural gas in 2020 will be used to generate electricity, twice
the rate of demand in 1980. Gas used exclusively for electricity is likely
to account for 11 percent of the world's energy demand by 2020,
from just under 4 percent in 1980.
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That's a good thing. The gas turbine and steam turbine combined
cycle is the most efficient of power plants, using less fuel than any
other for a given power output.
In the deregulated electricity market, a power plant may be called on
to start up or shut down upon demand, during the day. This calls for start-up
times measured in minutes rather than hours.
Gerry McQuiggan, engineering director for gas turbines, and his colleagues
in Orlando, Fla., point out that their company, Siemens Westinghouse,
is working to shorten combined-cycle start-up times. The time-limiting
components are on the steam, or Rankine, cycle. Siemens Westinghouse has
developed new steam-side components, such as an improved design of the
heat recovery steam generator, to significantly reduce combined-cycle
start-up time.
That is still on the horizon. And it's a view that might be easily
obscured by the results from 2003.
Forecast International of Newtown, Conn., estimates the value of worldwide
gas turbine production in 2003 was $22.9 billion, down 37 percent from
2002 and down almost 50 percent from the banner year of 2001, which peaked
at $45.4 billion (in 2004 dollars). Why did this 2003 reduction occur,
pushing back total value of production to the level of the early 1990s,
in the space of a year?
Each year's data is broken into two subcategories. The value of
production for aviation—jet engines, turboprop engines, and aircraft
auxiliary power units—was $14.4 billion, up less than 1 percent
from $14.3 billion in 2002. Of this total for 2003, civil aviation accounted
for $11.4 billion and military aviation gas turbines were at $3.0 billion.
That value of production has been fairly constant for the past seven years.
Robert Leduc, chief operating officer of Pratt & Whitney (one of the
three big jet engine manufacturers), sees this fairly constant aviation
value of production continuing until 2005. After this, he feels that both
airline and military sales should finally trend upward. More on this in
a minute.
Anything
but Stable
Non-aviation turbines, encompassing both land-based gas turbines (used
for such applications as electric power generation and tank engines) and
marine gas turbines, were anything but stable. The value of production
for non-aviation gas turbines in 2003 was $8.5 billion, down to nearly
a quarter of its 2001 peak. But mechanical drive gas turbines and marine
gas turbines remained at levels consistent with 2001 and 2002. The significant
downturn was due almost entirely to a sharp drop in sales of new gas turbines
for electric power. The value of production of electric power gas turbines
for 2003 plummeted to $7.2 billion, compared to a high of about $29 billion
in 2001.
There is no one reason for this decline. The failure and bankruptcy of
electric power trader Enron, for instance, and the California electric
utility deregulation meltdown led to a sharp decrease in capital funding
for new power plant projects. Overbuilding of merchant gas turbine power
plants in some areas of North America and the spike in gas prices removed
much of the rationale for new gas-powered generation. And the seemingly
unstable array of regulated and deregulated electric utility systems across
the United States has cast a specter of uncertainty across the industry.
Adam Robinson, the manager of power generation marketing for Solar Turbines,
explained that gas turbines of 100 MW output or greater suffered the greatest
downturn in 2002-03. He said that because of robust conditions in the
oil and gas industry and the expanding cogeneration market, the value
of production figures for gas turbines smaller than 100 MW remained strong
for 2003.
The future is undoubtedly brightening for aviation turbines. There was
a high level of activity among major airframe companies last year, and
that will improve commercial jet engine value-of-production figures in
the next few years.
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Boeing will be delivering its first long-range 365-passenger 777-300ER in 2004, powered by two General Electric GE90-115B engines rated at 115,000 pounds of thrust, or lbt. Early in 2003, General Electric tested this engine at a record 127,900 lbt. The new 555-passenger Airbus 380, powered by four 70,000 lbt engines (by either Rolls-Royce or a General Electric and Pratt & Whitney alliance) is slated for first deliveries in 2006. And the Boeing 7E7, a 250-passenger, two-engine aircraft designed to go into head-to-head competition with the Airbus 380, was announced by Boeing in 2003.
All three major engine manufacturers competed to provide engines, with
General Electric and Rolls-Royce winning, each offering derivative engines,
and Pratt & Whitney losing out, after proposing a completely new engine.
A 2003 military aviation highlight was the start of the system and development
demonstration test program for the jet engine on the Lockheed Martin Joint
Strike Fighter. At its Florida test center, Pratt & Whitney began
tests on the JSF F135 40,000 lbt class engine in the conventional takeoff
and landing configuration. Tests on the short takeoff/vertical landing,
or STOVL, version of the F135 will begin this year.
The STOVL version will allow the aircraft to hover solely on engine power,
using a separately clutched Rolls-Royce lift fan module, and then go into
supersonic flight, reaching speeds greater than Mach 1.5. This engine
will have the highest thrust-to-weight ratio and the most advanced turbine
cooling in the industry.
Historically, many gas turbine technology improvements, such as film cooling,
came from military engines, so one can look to the JSF program for eventual
improvements in the performance of both commercial aviation and non-aviation
gas turbines.
As 2003 ended, the new Queen Mary 2 prepared for its Jan. 12, 2004,
maiden voyage from Southampton, England. This trip eventually saw the
QM2 make a dramatic entrance into New York Harbor. The QM2,
considered to be the largest cruise ship afloat, is powered by two electrical
power aeroderivative gas turbines (GE LM2500+) and four electric power
diesels, giving it a top speed of 30 knots. It joins a growing fleet of
cruise ships powered by gas turbines.
H as
in Humongous
Land-based turbines also saw technological advances last year. Records
were set during 2003, with the smallest and largest electric power gas
turbines going into commercial operation. The smallest, claimed to be
the world's first portable gas turbine electrical generator, is
manufactured and marketed by IHI Aerospace of Japan. The unit, fueled
by diesel oil, consists of a fist-size 100,000 rpm gas turbine, an electrical
generator, and controls. The entire setup weighs just 67 kg and has an
output of 2.6 kW, at a noise level much lower than a comparable Otto cycle
engine. About 600 units were sold last year, two to the U.S. Army.
The world's largest gas turbine yet to go into service is General
Electric's 367,900 kg 9H (50 Hz) combined-cycle plant rated at
480 MW—more than 100,000 times the output of IHI's unit.
It is installed at Baglan Bay on the south coast of Wales to feed electric
power into the U.K.'s national grid. The 9H was tested by GE for
almost a year on site and started commercial service late in 2003.
According to Edward Lowe, product line manager of GE Energy, the thermal
efficiency of the Baglan Bay unit is just under 60 percent. He said GE
is confident that H system units will achieve 60 percent at more favorable
sites, making it the most efficient of combined-cycle plants.
The H system uses steam from the steam cycle to cool both turbine stators
and blades in the first and second stages of the gas turbine, or Brayton,
cycle. The heated coolant steam is then returned to the Rankine cycle
as reheated steam, reducing the heat input required to power the steam
turbine. By integrating the two cycles in this way, two points of the
nominal 60 percent thermal efficiency are gained, according to Lowe.
Lowe added that the component testing that was done for the H system is
the most extensive in GE's history. The H system testing is very
much like an aircraft gas turbine test program, and this appears to have
paid off. The Baglan Bay unit hasn't developed the kinds of problems
that plagued the industry's earlier F-class machines, which were
characterized by minimal OEM development programs and a rush to market.
A good part of the H system was developed under the DOE's Advanced
Turbine System program, which began in 1992.
Some of the earliest work on the concept of steam cooling in combined
cycles was done by Ivan Rice of Spring, Texas. He showed the performance
gains that could be realized, in a series of papers given at ASME gas
turbine conferences and published in the ASME Journal of Power
in the early 1980s Thermodynamists may come to classify the H system,
and others like it, as a new thermodynamic combined cycle, not two separate
ones. Perhaps it might be called the Rice combined cycle.
Lee S. Langston, a professor of mechanical engineering
at the University of Connecticut in Storrs, is the editor of ASME's
Journal of Engineering for Gas Turbines and Power.