Top Plant: Irsching 4 Combined Cycle Power Plant, Irsching, Bavaria, Germany

Courtesy: Siemens Energy

Owner/operator: E.ON

The Irsching 4 Combined Cycle Power Plant has set a new world record in power plant efficiency with its new SGT5-8000H gas turbine. With an output of more than 578 MW and efficiency of 60.75% (net) achieved at a world record test run in May 2011, the plant demonstrates that climate protection, low-cost power generation, and flexible operation using fossil fuels can be attained simultaneously through technical advances. Due to its high efficiency, the gas-fired plant uses significantly less fuel and produces lower carbon dioxide emissions than traditional combined cycle plants.

Germany, which has the world’s fifth-largest economy, is known for being a global trendsetter in its environmental practices and power plant innovation. Conserving resources is a well-established German habit, and recycling is almost a national sport. So it’s not surprising that the Irsching 4 Combined Cycle Power Plant in Bavaria is leading the way with its innovative gas turbine technology that maximizes efficiency while cutting greenhouse gas emissions.

The new gas turbine technology implemented at the Irsching 4 facility is the first in the history of power plant engineering to achieve a net electrical efficiency of over 60.75% while simultaneously producing a unit output of more than 578 MW (net) with one gas turbine (Figure 1), a generator, and a steam turbine. Siemens, the turnkey contractor, handed over the facility to E.ON in July 2011.

1. Transformative turbine technology. With an output of more than 578 MW and an efficiency of 60.75% (net), the Siemens combustion turbine used at the Irsching 4 Combined Cycle Plant is making history in the field of power plant technology. Courtesy: Siemens Energy

The new Siemens gas turbine is designed for 400 MW in simple cycle duty and for 600 MW in combined cycle duty. Michael Suess, CEO of Siemens Energy Sector, emphasized that “these are historic dimensions and world record levels.” The new plant consumes one-third less natural gas per kWh generated than the average for combined cycle plants currently installed worldwide. Consequently, the plant’s carbon dioxide emissions are reduced by a third.

“The Irsching 4 power plant is a prime example of eco-friendly, flexible power supply for the future,” said Klaus Hammer, COO of E.ON, who manages the operations of its combined cycle power plants. “High-efficiency, flexible gas turbine power plants like the Irsching 4 plant and the Irsching 5 plant, which went online in 2010, significantly help to compensate for the increasingly pronounced fluctuations in the feed-in of renewables-based power and thus make an important contribution toward assured power supply in Germany.”

Innovative Gas Turbine Design

“Our new gas turbine is a supreme example of the fine art of engineering,” Suess said. “What enabled us here to break new technical ground was that we all pulled together—power providers, engineers, building contractors, and also the public. In E.ON we found just the right partner to implement this trail-blazing technology.”

The engine concept was selected from a number of air-cooled engine design options and several gas turbine cycle variants after completion of a comprehensive feasibility analysis during the conceptual design phase, explained Willibald Fischer, program director of 8000H, Fossil Power Generation Division.

The internal, fully air-cooled concept selected offers maximum added value by virtue of its higher operational flexibility—an essential prerequisite in the deregulated power generation market environment. The most important gas turbine design features are:

  • Single tie-bolt rotor comprising individual compressor and turbine disks with Hirth facial serrations.
  • Hydraulic clearance optimization.
  • Thirteen-stage axial compressor with high mass flow, high component efficiency, controlled diffusion airfoils in the front stages and high-performance airfoils in the rear stages, variable guide vanes, and cantilevered vanes.
  • High-temperature, fully air-cooled, can annular combustion system.
  • Four-stage, exclusively internal air-cooled turbine section.
  • Advanced, on-board variable dilution air system, with no external cooling system.
  • Advanced, highly efficient, high-pressure and high-temperature combined cycle process with a Benson boiler design based on the high mass flow and exhaust temperatures of the new engine.

Promoting Flexibility Through FACY Features

“We not only achieved a world record, we also have built a plant with outstanding flexibility,” Suess said. “Apart from the improvements to the gas turbine, we have also incorporated the features already familiar from the SCC5-4000F 1S under the name of FACY (Fast Starting and Cycling) in order to achieve this special flexibility.”

An essential element of power plant flexibility under the market conditions referred to earlier is the time taken for a “hot start,” which is typically required after six to eight hours off line, in the early morning when demand on the grid starts to rise again. Suess explained that the Siemens engineering team was able “to demonstrate that, thanks to the FACY feature, the complete plant can be very reliably run up to full load in less than 30 minutes.”

Just as important is the reverse case, when the plant has to shed load or even run down very quickly if there is a sudden disturbance on the grid or a surge of power input from wind and solar generators. Seuss said, “here, too, we can prove that the plant can be run down to a minimum load or to zero within 30 minutes.”

“Despite its world-record size, the plant can, if necessary, run stably at around 100 MW—less than 20% of its total rated output—in combined cycle mode with an efficiency that is still that of typical peak-load (open cycle) power plants,” he said. “This shows that this plant can be used very efficiently throughout the base, intermediate, and peak load ranges.”

Balancing Fluctuating Renewables

With more wind and solar energy facilities providing a steadily increasing percentage of fluctuating power in-feed to the grid, rapidly reacting large-scale power plants that can compensate for weather-dependent in-feed fluctuations are a decisive factor for maintaining grid stability.

Lothar Balling, head of GT Power Plant Solutions in the Fossil Power Generation Division of Siemens Energy in Germany, commented on the importance of providing balance to the increasing amount of renewable power that is going online in Europe. “If we in Europe achieve the targets for significantly expanding our power generating capacity from renewable energy resources, it will be possible by 2020 in countries like Germany to meet the entire power demand in some periods on a sunny and windy day entirely from wind, solar, hydroelectric, and biomass-fueled power plants,” he said.

The new H-class plant can quickly react to the demands for additional or reduced output. Siemens tested a number of corresponding load gradients for this. As an example, more than 500 MW can be put online in only 30 minutes, and stable load gradients of 35 MW/minute can be run, according to Balling. The impressive performance of new high-efficiency, flexible gas turbine power plants like Irsching 4 is made possible by the interaction between innovative gas turbine technology and the plants’ key components, which are optimized for high temperatures and pressures.

Ensuring a Dependable Future Power Supply

“Irsching 4 is designed to provide a reliable supply of power to the industrial region surrounding Ingolstadt and other major parts of southern Germany,” said Hammer. He noted that the goal of a reliable electrical supply “is becoming more concrete against the backdrop of the faster nuclear phase-out currently being debated in Germany.” The nuclear moratorium shows that large-capacity power plants like Irsching 4 are necessary to stabilize the transmission network and thus ensure the reliability of supply because of significant changes in load flows, particularly in southern Germany.

Angela Neville, JD, is POWER’s senior editor.