This article explores the advantages of gas turbines in the marine industry. Marine gas turbines, which are designed specifically for use on ships, have long been one of the segments of the gas turbine market. One advantage that gas turbines have over conventional marine diesels is volume. Gas turbines are the prime movers for the modern combined cycle electric power plant. Both CFM International (a joint venture of General Electric and France’s Snecma) and Pratt & Whitney are working on new engines for this multibillion dollar single-aisle, narrow-body market. Pratt & Whitney’s new certified PW1500G geared turbofans will have a first flight powering the first Bombardier CSeries aircraft. On land, sea, and air, the surge in gas turbine production is remarkable. The experts suggest that what the steam engine was to the 19th century and the internal combustion engine was to the 20th, the gas turbine might be to the 21st century: the ubiquitous prime mover of choice.
When Looking for Gas Turbines Aboard an Aircraft Carrier, the First Place to Look is the Flight Deck. That’s where the ship’s complement of aircraft, each with its own set of high performance jet engines, is sitting awaiting takeoff. But in Scotland’s Firth of Forth, a new carrier is under construction at the Rosyth Royal Dockyard, that puts the gas turbine not just on the flight deck and hangar, but in the engine room. The Royal Navy’s HMS Queen Elizabeth, scheduled to enter service in 2016, is being equipped with two 36 MW Rolls-Royce MT30 gas turbines, to supply two thirds of the 109 MW of electric power necessary for propulsion and ship’s needs.
The HMS Queen Elizabeth and its sister ship, HMS Prince of Wales, introduce a new class of supercarrier for the Royal Navy. At a length of 920 feet, a top speed in excess of 25 knots, and a cruising range of 12,000 miles, the ships will carry 40 aircraft, consisting of gas-turbine powered helicopters and F-35s, the Lockheed Martin Lightning II STOVL Joint Strike fighter.
The twin-spool MT30 selected to power the ships is currently the world’s most powerful marine gas turbine, with a thermal efficiency exceeding 40 percent. It is an aeroderivative gas turbine, emanating from the Rolls-Royce Trent 800 turbofan engine, (93,000 pounds thrust), used on Boeing’s 777 airliner.
Marine gas turbines, which are designed specifi cally for use on ships, have long been one of the segments of the gas turbine market. But it’s a segment that has languished behind the outstanding production figures for stationary gas turbines used for generating electricity and the jet engines built for civil and military aviation. Even the remaining segment, turbines used mostly to drive compressors for natural gas pipelines and for liquefying natural gas, outpaces marine gas turbines. But sea-based applications are gaining prominence.
By 2018—Just Five Years from now—The Constant-Dollar value of Worldwide Production for Gas Turbines is Projected to be $73 Billion, a 29 Percent Jump.
For instance, in January my wife and I took a seven-day Caribbean cruise aboard the 2,046-passenger GTS Celebrity Summit. Built in 2001, the Summit is one of four Millennium-class cruise ships owned by Celebrity, each one powered by two General Electric LM2500+ aeroderivitive gas turbines. The turbines drive electric generators to power the ship’s propulsors, two stern-mounted electric motor azipods. As one boards Summit, the discerning passenger is greeted by the sight of an LM2500+ engine enclosed in a display case, with a sign announcing this is the ship’s spare engine, and proclaiming a mere 12-hour installation, if needed.
Summit’s two operating gas turbines, mounted in a lower deck engine room, each with a 30 MW output, exhaust into a 10-deck high, heat recovery steam generator, which is topped by the ship’s external funnel. HRSG steam produced by the hot gas turbine exhaust is used for ship’s heating and to drive a single 7 MW steam turbine to produce additional electrical power.
One Advantage that Gas Turbines Have
over conventional marine diesels is volume. Summit’s chief engineer told me that the space saved by the gas turbines allowed 120 more crew cabins to be added, which, in turn, provide space for 90 additional revenue-producing passenger cabins. Also, maintenance costs for the gas turbines are much less than those for conventional diesel engines. The usual time for gas turbine removal for overhaul is 60,000 hours of operation, with one of Summit’s units going for a record 85,000 hours.
Summit’s gas turbines burn marine gas oil, a low-sulfur fuel that’s roughly equivalent to the No. 2 fuel oil used in diesel road vehicles. Right now, costs for this type of fuel are very high. Cruise ship diesel engines use much cheaper, tarlike No. 6 fuel oil (Bunker C) with a very high sulfur content. With fuel costs for Bunker C fueled cruise ships amounting to about 30 percent of their operating costs, compared to as much as 55 percent for the MGO-burning Summit, sticking with diesels has been the safe bet for cruise line operators.
But that calculation may be beginning to change. Low sulfur fuels are now required for cruise ships operating in Antarctic waters, and pollution restrictions imposed by ports in Alaska—one of the most popular cruise destinations—has forced many cruise lines to install gas turbines for port power, as the only way to meet requirements for reduced sulfur dioxide and NOxs emissions.
In 2012, the marine gas turbine market had a value of production of only $509 million out of a total worldwide value of production of $56.7 billion—less than 1 percent. But there’s plenty of opportunity there for growth.
Those figures come from analyst Bill Schmalzer of Forecast International in Newtown, Conn. The company uses computer models and an extensive database to record value of production (considered to be more accurate than sales figures) for both the aviation and non-aviation gas turbine markets. For this review, Schmalzer has provided gas turbine market data dating back to 1990 and forecasts projecting to 2022.
Even if one is skeptical of market predictions 10 years into the future, FI’s forecast of near-term growth is bracing: by 2018—just five years from now—the constant-dollar value of worldwide production for gas turbines is projected to be $73 billion, a 29 percent jump.
Broadly, the Gas Turbine Market
is divided into two parts: those for aviation, and everything else. In addition to the $509 million value of marine gas turbine production, in 2012 mechanical drive gas turbines had a value of production of $2.3 billion and those for use in electrical power generation had a value of production of $13.6 billion, up by 7.4 percent from 2011.
Gas turbines are the prime movers for the modern combined cycle electric 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 to 60 percent range. Advanced combined cycle plants are being developed by Alstom, General Electric, Mitsubishi, and Siemens, with efficiency targets up to 65 percent.
In December, I attended an IGTI meeting in Munich, and visited the Irsching E.ON Kraftwerke. In 2011, Siemens announced that its combined-cycle unit at Irsching had reached a record thermal effi ciency of 60.75 percent, with an electrical output of 578 MW. This would make it likely the most efficient heat engine ever operated—and a must-see for an engineer interested in gas turbines.
A Staggering Prediction: The Value of Production for Civil Aviation Gas Turbines will reach $50.6 billion in 2018. That’s Close to the Size of the Entire Gas Turbine Market last Year.
It was about an hour train ride to the north of Munich, through snow-covered Bavarian farmland, passing by houses and barns, most with roofs supporting arrays of solar panels. (Germany has an aggressive renewable energy program, with a heavy reliance on solar and wind.) The Irsching 4 record-breaking combined cycle plant is housed in a handsome ultramodernistic building along the Danube. The E.ON plant manager said they typically run the unit from 5 a.m. to about 7 p.m. each day. (E.ONs gas turbine plant in Russia runs continuously, an illustration of difference in dispatching practices.)
The Siemens unit is a single-shaft arrangement with the generator mounted between the steam turbine and the SGT5-8000H gas turbine. It must have been quite a feat to move this largest gas turbine in the world, weighing 489 tons with an output of 375 MW, from Siemens’s plant in Berlin to Irsching.
Siemens has a unique blade tip clearance system, called hydraulic clearance optimization. With the daily load variation and the start-ups and shutdowns, rotating blade tip clearances can increase or decrease; Siemen’s HCO has hydraulic pistons that can shift the rotating gas turbine rotor along the axis of rotation.
The outer case of the gas path is conical in the compressor (apex downstream) and in the turbine (apex upstream). Thus an HCO rotor shift towards the gas turbine inlet decreases the blade tip clearance in the turbine, but increases those in the compressor. However, since turbine power is twice the power to drive the compressor and the conical turbine case is four times steeper than that of the compressor, increased compressor tip losses are only one-eighth of the turbine’s power and efficiency improvement.
The continued improvement in the efficiencies of gas turbine combined cycle plants and the recent shale natural gas finds in the U.S. are upending traditional views on the economics of generating electricity. In its Annual Energy Outlook 2012, the U.S. Energy Information Administration presents estimates of the averaged levelized costs for generating technologies brought online by 2017, considering the per-kilowatt-hour cost of building and operating a generating plant over an assumed financial life and duty cycle.
EIA estimates 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 like the one at Irsching would have a total system levelized cost of 6.3 cents/kWh. Anyone wanting to add generating capacity through some other means has to come up with reasons why they wouldn’t want to build a plant like Irsching.
While much of the most Interesting
work is going on elsewhere, aviation—jet engines and turboprop engines for commercial and military manned aircraft—is still the dominant market sector for gas turbines. Indeed, only during a brief period of electric utility deregulation hubris more than ten years ago did non-aviation gas turbine production values exceed those of aviation. In 2012, a more typical year, the total aviation gas turbine value of production was $40.2 billion, representing 71 percent of the total for all gas turbines. That’s a 10 percent increase over the value of production in 2011.
It Might not be too much Hyperbole to Suggest that What the Combustion Engine was to the 20th, the Gas Turbine might be to Steam Engine was to the 19th Century and the Internal the 21st Century: The Ubiquitous Prime Mover of Choice.
Forecast International projects an aviation total of $56.5 billion for 2018. Projections by airframe makers Boeing and Airbus also show substantial growth in aviation gas turbine production, as markets expand in China and India.
Military gas turbines represent a small segment of the market, with the value of production in 2012 accounting for $6 billion, or about 15 percent of the total aviation market. The military segment, however, is a key to future growth in all parts of the gas turbine market.
Many commercial engines emerged from antecedent military designs. And the technology developed from military programs has historically resulted in benefits for other gas turbine areas. For instance, single crystal turbine airfoils and film cooling technology started with military jet engines, and are now commonplace for use in commercial gas turbines, both aviation and non-aviation.
The new F135 Joint Strike Fighter engine is a case in point of advanced technology that will probably benefit commercial engines in the future. Now in production and testing, the F135 is a 3,600 °F (1,982 °C) class engine, operating at extreme temperatures for high performance. Some of this high-temperature technology will lead to more efficient commercial designs in the future.
The commercial aircraft gas turbine value of production for 2012 was $34.2 billion, and Forecast International predicts that value of production for commercial gas turbines will reach $50.6 billion in 2018. That sum is close to the size of the entire gas turbine market last year.
That staggering prediction is made with good reason. There is a great deal of activity in the commercial airplane market. In the twin-aisle, wide-body segment, Boeing is sorting out problems with its new 787 as the plane has entered service, and is working on a stretch version. Airbus is developing its competing A350, which will have a first flight this year.
The single-aisle, narrow-body passenger plane market has seen unprecedented activity in 2012 and should see much more in 2013. The biggest segment is in the 100-to-210-passenger size, which has been a near duopoly for the Boeing 737 and the Airbus A320. Now Canada’s Bombardier, China’s COMAC, and Russia’s Irkut are introducing airframes in this segment. In the 70-to-110-passenger size, Japan’s Mitsubishi and Brazil’s Em- braer are also developing new aircraft.
Both CFM International (a joint venture of General Electric and France’s Snecma) and Pratt & Whitney are working on new engines for this multibillion dollar single-aisle, narrow-body market. CFM International’s LEAP-X engine will have first full engine tests this year and certification is expected in 2015. And Pratt & Whitney’s new PW1500G geared turbofans, now certified, will have a first flight this year, powering the first Bombardier CSeries aircraft.
On land, sea, and air, the surge in gas turbine production is remarkable. It might not be too much hyperbole to suggest that what the steam engine was to the 19th century and the internal combustion engine was to the 20th, the gas turbine might be to the 21st century: the ubiquitous prime mover of choice.