Much is made of the benefits of modular design and construction but not often associated with the large scale of power plants.
Yet, this is the path Siemens Energy has taken to bring online the world’s largest H-class gas turbine, expected to deliver 60%+ thermal efficiency in combined-cycle operation.
That operating mode will come after adding a steam turbine, with full system completion and handover expected in mid-2011.Installed at the Irsching gas power plant, SGT5-8000H gas turbine is a 440 metric ton, 50-Hz machine that outputs 340 MW—and is designed for 530 MW in eventual combined-cycle operation.
Control Engineering was fortunate to be able visit Irsching Unit 4 in late-Nov. 2008 to obtain a first-hand progress update from Willibald Fischer, Siemens program manager for H-turbines. The site is Siemens’ turbine Test Center until turnover of the system to German power company E.ON Kraftwerke.Siemens’ H-class turbine is now in phase 2 endurance/durability testing until mid-year `09, accumulating operating hours and start-up experience, explains Fischer. “This is a semi-commercial operating stage, with tenders ongoing to other customers,” he says.
Instrumentation engineer’s dream: 597 spinning sensors The Irsching test site is an exciting place for control/instrumentation engineers. Some 2,838 sensors and associated wiring are deployed to monitor the turbine. Of these, 597 rotate with the turbine, with data brought out to telemetry units at each end of the rotor.
Most numerous are temperature and pressure sensors (1,688 and 616, respectively), and strain-gages (357), besides accelerometers and other sensors for clearance, blade vibration, and flow/force measurement. All test information goes to onsite computers for monitoring by a small staff; then, data are transmitted for detailed analysis to Siemens facilities in Orlando and Jupiter, FL, and Mülheim, Germany. “Data flow is near real time. One hour of testing produces 90 gigabytes of data,” Fischer explains.
With modular construction, the SGT5-8000H currently produces electric output only by shaft power directly coupled to the generator (simple-cycle operation).Through Nov. `08, approximately 250 hours of operation have been logged. Siemens intends to demonstrate reliable turbine operation under cyclic loads, thus daily shutdowns are part of the testing. H turbine is said to be capable of 150-200 starts per year, if needed, but also can deliver 8,000 hours of baseload operation.
The gas turbine’s second output—exhaust to the heat recovery steam generator (boiler)—will come into play during combined-cycle gas turbine (CCGT) operation. Build-out of the CCGT plant begins in mid-2009. However, foundations for the steam turbine, other civil engineering works, an air-intake filtration system, and myriad auxiliary equipment are in place, thanks to modular construction.
In a single-shaft CCGT plant layout, the steam turbine will connect to the end of the generator opposite the gas turbine. The boiler will be installed behind the gas turbine’s high-temperature exhaust diffuser and connected to the steam turbine by steam piping systems. The boiler, steam turbine, and condenser, are scheduled to arrive in 2010. Program completion date of July 2011 remains on target, as the “steam side” of the plant represents more predictable, standard technology, notes Fischer.
Kilovolts next to millivolts-Test work at Irsching is one of contrasts. “While kilovolts of electricity flow from the system’s output to the grid, just millivolts monitor banks of sensors at other points of the same system to ensure the turbine’s health,” Fischer adds.
Siemens’ investment in H-class gas turbines is projected to be €500 million through the project’s completion. An undertaking of this size is bound to be costly and needs to be viewed as a lease on the future.