The hunt for 60+% thermal efficiency

In this era of high concern for energy consumption, readily available energy-efficient motors top the 96% mark, electric drives reach 95%, and many appliances and consumer devices exhibit rising efficiency. What, then, makes 60% thermal efficiency so special? It’s a much different scenario for power generation.

08/01/2008


In this era of high concern for energy consumption, readily available energy-efficient motors top the 96% mark, electric drives reach 95%, and many appliances and consumer devices exhibit rising efficiency. What, then, makes 60% thermal efficiency so special?

It’s a much different scenario for power generation. Complex combustion and fluid-flow processes involved in power conversion limit thermal efficiency, despite application of the best engineering know-how. For example, a typical light-water reactor nuclear power plant offers thermal efficiency around 35%, while a modern coal-powered plant with super-critical boiler tops out at 44%.

However, one power technology, the gas turbine, has been pushing the efficiency envelope. These large, land-based (stationary) turbines—with 100s of megawatt (MW) output—draw on the advances in design, materials, and cooling techniques of their more numerous aircraft gas turbine cousins. The latest turbines offer thermal efficiencies in the 40% range, with a recent model reportedly obtaining 46%.

These values refer to simple-cycle operation, where turbine exhaust is not further used. Real advantage comes from gas turbine exhaust applied as input to a standard steam turbine in a combined-cycle power plant. This is where new-generation gas turbines can become the driving engine to obtain 60%+ overall thermal efficiency.

Europe leads the way

Among stationary gas turbine suppliers, developments from two manufacturers are particularly noteworthy. GE Energy installed the first of its H systems (combined-cycle gas and steam turbine) at Baglan Bay power station in South Wales (U.K.). The plant went commercial in 2003 and, to date, has logged over 30,000 operating hours. Currently it runs at 480 MW, with capability for higher output, according to GE Energy.

Five other GE H turbines are in various stages of implementation; three are in Japan at Tokyo Electric Power Co.’s (TEPCO’s) Futtsu thermal power station. The first of these 50-Hz machines was initially fired in Dec. 2007, and is expected to be in operation in late summer 2008. H systems in TEPCO Units 2 and 3 are scheduled to run by mid-2010.

GE’s first H-class turbine in the U.S., also its first 60-Hz machine, was installed in 2006 at Inland Empire Energy Center—a natural gas combined-cycle power plant in Riverside County, CA. Two GE H systems will comprise this plant, which is designed for maximum net rated electrical output of 775 MW to domestic and business users. Inland’s two units are scheduled to go online later this summer.

Meanwhile, Siemens Power Generation is moving its H-class SGT5-8000H turbine toward commercialization. Installed at the Irsching 4 gas power plant near Ingolstadt, Germany, the first firing of the turbine occurred in Dec. 2007. First synchronization to the grid followed in March 2008 and full-load testing (simple-cycle mode) started in April 2008, notes Phillip Ratliff, director of next-generation gas turbines at Siemens.

Siemens’ 50-Hz machine outputs 340 MW, but is designed to produce 530 MW in eventual combined-cycle operation—with expected efficiency of more than 60%. “A 60-Hz turbine is being developed after further verification of the first design,” says Ratliff.

An extensive test and validation program will continue for the SGT5-8000H turbine until mid-2009. Then, build-out of the combined-cycle plant begins in phase 2 of the program, with transfer to the plant operator, E.ON Kraftwerke GmbH, expected in mid-2011.

The next couple of years look exciting for the gas turbine power generation arena.



ONLINE extra

Also read: New, efficient industrial gas turbines coming . The story describes GE Energy and Siemens Power Generation technologies that weigh up to 440 metric tons.


Author Information

Frank J. Bartos, P.E., is a Control Engineering consulting editor. Reach him at braunbart@sbcglobal.net .




No comments
Consulting-Specifying Engineer's Product of the Year (POY) contest is the premier award for new products in the HVAC, fire, electrical, and...
Consulting-Specifying Engineer magazine is dedicated to encouraging and recognizing the most talented young individuals...
The MEP Giants program lists the top mechanical, electrical, plumbing, and fire protection engineering firms in the United States.
Water use efficiency: Diminishing water quality, escalating costs; Lowering building energy use; Power for fire pumps
Building envelope and integration; Manufacturing industrial Q&A; NFPA 99; Testing fire systems
Labs and research facilities: Q&A with the experts; Water heating systems; Smart building integration; 40 Under 40 winners
Maintaining low data center PUE; Using eco mode in UPS systems; Commissioning electrical and power systems; Exploring dc power distribution alternatives
Protecting standby generators for mission critical facilities; Selecting energy-efficient transformers; Integrating power monitoring systems; Mitigating harmonics in electrical systems
Commissioning electrical systems in mission critical facilities; Anticipating the Smart Grid; Mitigating arc flash hazards in medium-voltage switchgear; Comparing generator sizing software
As brand protection manager for Eaton’s Electrical Sector, Tom Grace oversees counterfeit awareness...
Amara Rozgus is chief editor and content manager of Consulting-Specifier Engineer magazine.
IEEE power industry experts bring their combined experience in the electrical power industry...
Michael Heinsdorf, P.E., LEED AP, CDT is an Engineering Specification Writer at ARCOM MasterSpec.