Siemens Energy is to supply an industrial 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 in the vicinity of 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 thus become a reference product for solar tower power plants.
In the “Solar Tres” solar tower power plant operated by Sener the sunlight will be bundled by sun-tracking mirrors (known as heliostats) and reflected directly to a receiver located on top of an approximately 120-meter-high tower. The heliostats will be arranged over a surface area of 320,000 square meters, which is equivalent to the size of more than 40 soccer fields. 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.
Sener had commenced planning construction of the “Solar Tres” solar tower power plant seven years ago. 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 insolation 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.
Siemens is market leader for steam turbines for solar thermal power plants and has already secured orders for the supply of more than 40 of these specially adapted turbines. Unlike the Sener solar tower power plant, most of the solar power plants planned to date featured parabolic mirrors in a parallel configuration, which focus the solar radiation on piping. In these pipes a thermo oil is heated and then flows through a heat exchanger. A steam turbine-generator is operated with the steam produced.
“The solar power market is one of the fastest growing power plant markets,” said Markus Tacke, CEO of the Siemens Business Unit Industrial Applications, Steam Turbines. “Due to their flexibility, our steam turbines are perfectly suited for deployment in solar power plants to ensure the efficient production of eco-friendly electricity.” Solar power is an important part of Siemens environmental portfolio, which accounted for company revenues totaling EUR17 billion in 2007.