With an electrical rating of 838 MW and an efficiency of 59.2 percent in straight power generation, the new plant surpasses the contractually agreed performance values. Thanks to the district heating output of 400 MWth, more than 80 percent of the energy in the fuel is put to effective use. 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,” says 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 Thermal Power GmbH & Co. KG, sums up the benefits of the new power plant. The new plant 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 dust-free district heating makes an effective contribution to improving air quality,” adds Mayer.
The Mellach combined-cycle plant runs on natural gas and is located to the south of the regional capital of Graz. The two new power plant units 10 and 20 are designed as single-shaft plants in which the major components are arranged on the same shaft. In addition to 5 billion kilowatt-hours (kWh) of electric power per year, the plant can produce about 800 million kWh of 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 doing the maintenance for the main components. To comply with strict local water pollution control regulations, the plant features two different cooling systems: unit 10 is cooled by fresh water, while unit 20 has a cooling tower. The two transformers were manufactured in the Siemens Transformers Austria Weiz facility, which was also responsible for the planning, construction and testing of the transformers and their assembly and commissioning at the plant.
High-efficiency combined cycle power plants are part of the Siemens environmental portfolio, with which the company earned revenues of about €30 billion in fiscal 2011. This makes Siemens one of the largest global suppliers of environmentally friendly technology. Using Siemens products and solutions, customers saved nearly 320 million metric tons of carbon dioxide (CO2) during the same time period; this figure is equivalent to the total annual CO2 emissions of Berlin, Delhi, Hong Kong, Istanbul, London, New York, Singapore and Tokyo combined.