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Glory days of steam are back for Siemens

Industrial giant Siemens Energy is to supply a steam turbine for one of the world’s first commercial solar tower power plants.

The Spanish company Sener will build the innovative solar thermal power plant with a capacity of 19 megawatts (MW) at a site near Seville in Andalusia.


For the “Solar Tres” project Siemens will supply an industrial steam turbine specially adapted to meet solar technology requirements. The turbine will become a reference product for solar tower power plants.

In the power plant the sunlight will be bundled by heliostats – sun-tracking mirrors – and reflected directly to a receiver located on top of 120-metre high tower. The heliostats will be arranged over a surface area of 320,000 square metres, which is equivalent to the size of more than 40 football pitches. A unique feature of the Sener project is the use of salt for heat transfer in the interior of the receiver instead of the thermo oil normally used in solar thermal power plants. Bundling of the sunlight produces temperatures of over 850°C at the solar receiver. The salt heated to approximately 565°C flows in a molten state through a heat exchanger, in which sufficient steam is produced to operate a steam turbine-generator.

The overall project is backed with funds provided under the terms of the Fifth European Community Framework Research Program (Contract NNE5-2001-369). For the demonstration plant Siemens will supply a two-cylinder reheat SST-600 industrial steam turbine, which was specially adapted to meet solar technology requirements. The reheat enhances overall power plant efficiency. Since insulation fluctuates significantly depending on the time of day and season, a concept was developed jointly with Sener, which protects the steam turbine from cooling down too much at night and also significantly shortens the warm-up phase on start-up.