The solar thermal power plant Andasol 3 is situated in the South of Spain and has been realised by Stadtwerke München and RWE Innogy in conjunction with Ferrostaal, RheinEnergie and Solar Millennium. The power plant has an installed capacity of about 50 megawatts, and is jointly operated by the project partners.
Andasol 3 is the third solar thermal power plant to be installed in the Spanish province of Granada by Solar Millennium. The neighbouring projects Andasol 1 and Andasol 2, which each have an electrical output of around 50 megawatts, are already connected to the grid. The power plants, which are almost identical in their construction, have a collector surface area of over 1.5 million square metres – equal to the surface area of approximately 210 football fields.
Thermal storage system for generating electricity day and night
At the Andasol 3 site more than 210,000 parabolic mirrors capture the sunlight. These six metres wide, arched mirrors concentrate the sun’s rays to heat a transfer fluid. Then, through heat exchanging devices the thermal energy is transferred to a water/steam circuit. As in a conventional power station, this steam drives a turbine that in turn drives a generator, which produces electricity.
The Andasol 3 plant also has a thermal storage system, comprising of 30,000 tonnes of a special salt mixture. This can continue to run the turbine for 8 hours at full load, and is therefore able to reliably generate electricity even after the sun has set.
If you ever have held a magnifying glass in the sun, you know how it works: the lens concentrates the rays to produce temperatures high enough to ignite paper. Parabolic trough power plants work on the same principle, but concentrate the sun’s rays with enormous curved mirrors. The 12-metre-long and roughly 6-metre-wide parabolic mirrors focus the sunlight onto an absorber tube, the ‘receiver’. Inside this vacuum-insulated tube flows a heat transfer fluid, usually oil, that the sun can heat to temperatures of up to 400 degrees Celsius. The hot oil is used to generate steam in a heat exchanger – and the steam then drives a turbine in a conventional power plant where a generator produces electricity.
What makes solar thermal plants like Andasol so special is the attached heat store that makes solar electricity available even at night. Liquid salt acts as a heat storage medium that can compensate for short-term fluctuations in production and ensure reliable electricity generation around the clock. When the sun shines, the storage tank is topped up with the hot salt solution. When it’s cloudy or during the night, the salt solution releases its heat back into the thermal oil. The thermal storage unit can hold some 28,500 tonnes of the salt mixture; the capacity is sufficient for over seven hours of full load operation. That means these plants can generate almost twice as much electricity as a solar power plant without a thermal storage system.
The solar thermal power plant Andasol 3 in the south of Spain is realised by the project company Marquesado Solar S.L. Stadtwerke München has a 48.9% share in this company. RWE Innogy and RheinEnergie jointly hold 25.1% of the shares via an investment holding company (Andasol AS 3 Beteiligungs GmbH: RWE Innogy: 51%, RheinEnergie: 49%). The remaining 26% of the project company are equal shared owned by Ferrostaal Industrial Projects GmbH and the Andasol 3 Kraftwerks GmbH.
|Location:||10 km east of Guadix, Granada Province|
|Size of the solar field:||497,040 m2|
|Number of parabolic mirrors:||204,288|
|Number of receivers (absorption pipes):||21,888 pipes each measuring 4 m|
|Heat storage capacity||30.000 t salt for 8 peak load hours|
|Power plant capacity|
|Turbine capacity:||approx. 50 MW|
|Annual operating hours:||3,700 peak load hours|