In an opening ceremony on 22 June, Austria’s most efficient thermal power plant officially came on line as constructor Siemens formally handed over the Mellach combined-cycle plant to Austrian utility Verbund Thermal Power.

The heat and power cogeneration plant had already commenced operation in May this year. With an electrical rating of 838 MW and an efficiency of 59.2 % in straight power generation, the new plant has exceeded the contractually agreed performance values. When supplying 400 MWt of heat for district heating thermal efficiency rises to 80 %. This makes the new plant in Mellach not only the most powerful, but also the most efficient thermal power plant in Austria. It makes a major contribution to an environmentally compatible power and district heating supply for the Styria region.

“The Mellach combined cycle power plant meets the highest standards in terms of efficiency and flexibility. Fast start-up times and steep load gradients make the plant ideal for supplementing volatile power generation from renewable energy sources. The highly efficient design of the heat extraction system also reduces CO2 emissions significantly. This makes the plant a reliable cornerstone for a stable power supply in Austria over the coming decades,” said Roland Fischer, CEO of the Fossil Power Generation division at Siemens Energy. ‘More energy with fewer emissions’ is how Walter Mayer, board member at Verbund, summed up the benefits of the new power plant. It replaces five older units in southern Austria that were run on lignite or oil fuel, thus saving up to two million tons of CO2 per year. ‘Heat-and-power cogeneration also brings an immediate advantage for the Graz metropolitan area, where particulates-free district heating makes an effective contribution to improving air quality,’ adds Mayer.

The Mellach plant runs on natural gas and is located to the south of the regional capital of Graz. The two new units, designated 10 and 20, were designed as single-shaft units. In addition to 5 billion kWh of electric power per year, the plant can produce about 800 million kWh of thermal energy for district heating.

Siemens erected the plant as a turnkey project and supplied two gas turbines of type SGT5-4000F, two SST5-5000 steam turbines, two SGen5-2000H generators, all the electrical equipment, and the SPPA-T3000 instrumentation and control system. The company will also be carrying out the maintenance for the main plant components. To comply with strict local water pollution control regulations, the facility features two different cooling systems: unit 10 is cooled by fresh water, while unit 20 has a cooling tower. The facility’s two transformers were manufactured in the Siemens Transformers Austria Weiz factory, which was also responsible for the planning, construction and testing of the transformers and their assembly and commissioning at the plant.