The location of solar thermal power station Andasol 3, close to Granada in southern Spain is ideal. At 1,100 m, the sun shines for around 3,000 hours per year and the new power station can supply up to 200,000 people with electricity from the sun’s energy.

Andasol 3 is a parabolic trough power plant. The core element is the solar field that supplies steam for the conventional steam turbines. It consists of many rows of solar collectors arranged in a north-south direction. More than 204,000 mirrors over a collector area of 497,000 m². The reflectors consist of parabolically formed mirrors made from four millimeter thick, silver coated bowed clear glass. In the course of the day, they follow the sun’s course from east to west.

The collector mirrors concentrate the sun’s rays 80-fold on to an absorber tube in the collector’s focal line – in total, there are 21,888 tubes each 4 meters long. Within the absorber tube, temperature-resistant synthetic oil circulates in a closed loop where it’s heated to 400 degrees Celsius and is then pumped to a centrally located power plant where it flows through the heat exchanger. The steam generated in the heat exchanger then drives a generator — which supplies the electricity — via an MAN Turbo steam turbine.

The high-pressure and low-pressure turbines used at the Andasol 3 solar thermal power plant come from MAN Diesel & Turbo in Oberhausen, Germany – a result of many years of experience building complete turbomachinery trains.

The turbine dimensions are impressive: eight meters long, four meters wide, almost five meters high, a stately 160 tons in weight – and designed to provide 50 megawatts. The dual-housed machinery train has been specially optimized for solar power operation in Spain with significantly increased efficiency. The solar field delivers a peak efficiency of around 70% (an annual mean of around 50%). The efficiency of the complete facility is around 28% at its peak and around 15% annual mean – environmentally-friendly energy that couldn’t otherwise be used.

What’s special about Andasol is that it also delivers energy at night and when the sun doesn’t shine for a few hours. Part of the thermal energy is stored in giant tanks containing molten salt. A mixture of around 28,500 tons of potassium and sodium nitrate salts are heated during periods of sunshine and then provide the necessary heat for the power plant at night or during cloudy periods. The molten salt mixture with an initial temperature of 290 degrees Celsius absorbs additional heat that raises its temperature to around 390 degrees Celsius. Two tanks are used for storage per power plant and use a principle similar to a Thermos flask, keeping the salt warm for several weeks. A full salt reservoir can drive the power plant turbines for around 7.5 hours. That means energy generation can be planned and the electricity supplied evenly. Operation that is almost around the clock is possible during the summer months.

The relevance of Andasol has also been recognized by the European Parliament; in 2008 the major project received the “Energy Globe Award”. The globally renowned environment prize honors the project’s innovative character and the significant contribution to climate protection.

Andasol 3 – just one example of the groundbreaking possibilities that MAN technology makes possible in the fields of energy and environmental protection.

MAN. Engineering the Future — since 1758.