Siemens combined cycle achieves 60% milestone

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Siemens is first past the post of achieving over 60% combined cycle efficiency with the opening of its Irsching 4 plant in Germany. After ten years in development, the H-class gas turbine (SGT5-8000H) is the cornerstone of this landmark. Its output of 578 MW and measured efficiency level of 60.75% during a lengthy extensive test phase are world record levels, according to Michael Suess, CEO of Siemens Energy Sector. As well as output, he singled out its operating flexibility. "With more wind and solar plants providing a steadily increasing percentage of fluctuating power to the grid, rapidly reacting large-scale power plants that can compensate for weather-dependent fluctuations are a decisive factor for maintaining grid stability", said Suess.

As such, this new machine can put more than 500 MW online within 30 minutes at increments of 35 MW per minute. Further, the H-class in CCP mode consumes one-third less natural gas perkilowatt-hour compared to current CC plants.


More than 750 Siemens employees, including 250 engineers, were involved in this development at a cost of more than half a billion Euros in turbine development and in construction/operation of this prototype plant. Situated in the small town of Irsching in Bavaria (Southern Germany), it has been undergoing testing for one and a half years.

Initially, the plant operated as a simple cycle facility to ensure H-class operations met expectations. Once proven, Irsching 4 was converted to a combined cycle facility through the addition of a bottoming steam cycle with a once-through Benson-type Heat Recovery Steam Generator (HRSG) and a Siemens high-temperature steam turbine operating at 600° Celsius.

The current phase, known as the trial operation phase, is being done in readiness for German utility E.ON taking over commercial operation of Irsching 4 this summer. Meanwhile, the company has begun sales of a 60 Hz H-class version into the U.S. and Asian markets. Suess noted six units sold for the 1200 MW Cape Canaveral and Riviera Clean Energy

Centers of Florida Power & Light with these machines currently being produced in Berlin. They will be shipped to Florida in 2012. Another 60 Hz order of two units is for the 410 MW Bugok III plant of GS Electric Power & Services, Ltd in South, scheduled to go online in 2013.

“The SGT6-8000H, rated at 274 MW, is a direct scale of the 50 Hz SGT5-8000H,” said Fischer. “A scaling factor of 1 : 1.2 is being applied consistently over the entire cross section of the turbine.”

The exception is the combustion system, where the same burners and baskets are used as in the 50 Hz model. But in order to reflect the reduced mass flow of approx. 1 : 1.44, only 12 can combustors are used on the 60 Hz model instead of 16 in the 50 Hz version.

“Our first 60 Hz unit will be installed in the test center of our Berlin factory in 2011 and be subject of a six-month test program,” said Fischer.