Advancing Technology: High-efficiency gas turbines

General Electric and Siemens are among companies pushing the frontiers of large high-efficiency gas turbines for electricity generation. Target is more than 60% thermal efficiency for combined-cycle power plants.


Introduction of the newest H-class gas turbines over the past few years is making greater than 60% thermal efficiency a reality for combined-cycle gas turbine (CCGT) power plants. H-class is the largest and most efficient of gas turbines now being produced for electric power generation.

Relatively few manufacturers build these giant machines; among them are Alstom, General Electric, Mitsubishi Heavy Industries, and Siemens. In the forefront of H-class gas turbine development, GE Energy has three installations worldwide at CCGT power plants. GE’s first H-class installation was a 9H system that began service in 2003 at Baglan Bay power station in Wales, U.K. This 520-megawatt (MW) output, 50-Hz system has compiled more than 36,000 operating hours and served as a technology validation site.

Three other 50-Hz GE H-turbine systems are at work in Japan at Tokyo Electric Power Co.’s (TEPCO) Futtsu thermal power station 4. The first system went into service in 2008, while the third one just recently entered commercial operation. “That brings the total H-technology output for three units at the TEPCO site to 1,520 MW,” said Don Hoffmann, advanced combined cycle platform leader, GE Power & Water. A noteworthy sidelight is that Futtsu 4 is part of a larger TEPCO complex that produces more than five gigawatts of power—making it one of the world’s largest gas turbine combined-cycle installations. Besides the three H systems, the site employs 18 smaller GE gas turbines.

GE’s first 60-Hz H system went online in 2008 at Inland Empire Energy Center in Riverside County, CA, accumulating more than 8,000 operating hours. With the recent start-up of a second turbine, the plant has surpassed 10,000 total operating hours, according to Hoffmann. Inland CCGT power plant has maximum net rated electric output of 775 MW.

Modular implementation

Meanwhile, Siemens Energy is approaching completion of a 10-year development program for its 50-Hz H-class SGT5-8000H turbine that weighs in at 440 metric tons and is designed for 530 MW output in combined-cycle operation. Siemens chose a novel, modular commercialization approach by installing the turbine at a working gas power plant—Irsching 4, near Ingolstadt, Germany. Following synchronization to the grid in March 2008, extensive design validation, durability evaluation, and full-load testing in simple-cycle mode has taken place. Some 1,500 operating hours have been achieved in this mode.

In phase 2 of the program, build-out of the combined-cycle plant began, which included civil engineering work for cooling water piping and the heat recovery steam generator (HRSG), where hot turbine exhaust will be fed in combined-cycle operation. Other progress included installation or near completion of most of the steam turbine, condenser, cooling system, HRSG, and electrical and I&C equipment, explained Willibald Fischer, Siemens’ program manager for H-turbines. Fischer adds that most of the mechanical and electrical installation work will be completed by year-end 2010.

Hot recommissioning of the gas turbine and associated combined-cycle systems will follow early next year. “First firing is on schedule for early January 2011 and hand-over to our customer—E.ON Kraftwerke—remains on target for mid-2011,” said Fischer. “Based on final evaluation of hundreds of terabytes of test data, we are very confident to be able to demonstrate in reality what we promised.”

Scaled from its 50-Hz turbine, Siemens has designed a 60-Hz machine (SGT6-8000H) and announced a first sales order of six units in June 2010 (read more online).

Frank J. Bartos, PE, is a Control Engineering contributing content specialist. Reach him at


Also see:,%20search%20for%20/


- First order for Siemens’ 60-Hz, H-class gas turbine


- The hunt for 60+% thermal efficiency


- Largest gas turbine: 2,838 sensors, 90 GB data per hour of testing


- New, efficient industrial turbines coming

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