Andasol Solar Power Station: a parabolic trough solar thermal complex in Andalusia

Technology and main components

Andasol uses parabolic trough collectors: long, curved mirrors that focus sunlight onto a receiver pipe running along the focal line. A heat transfer fluid circulating through the receiver is heated by concentrated sunlight and carries thermal energy to a conventional steam turbine to generate electricity. To extend operating hours beyond daylight, Andasol incorporates molten-salt (liquid salt) thermal storage. The stored heat can be released to produce steam for several hours after sunset, allowing the plant to supply electricity on demand in the evening.

History and development

The Andasol complex was built in the mid-to-late 2000s as part of a broader push in Spain and Europe to deploy renewable electricity technologies at utility scale. Initial units were constructed near Guadix because of the high solar resource and available flat land. Following the first unit, additional sister plants were added at the same site to form a multi-unit complex, often referred to collectively as the Andasol plants.

Performance and impact

Each Andasol unit has a nominal capacity of about 50 MW and a thermal energy storage system designed to allow several hours of full-load operation without sunlight. Typical annual production figures for a single unit are on the order of 170–180 gigawatt hours, depending on site conditions and operational patterns. That generation displaces fossil-fuel electricity and contributes to greenhouse-gas reductions, while providing a more predictable output than non-stored solar photovoltaic systems.

Advantages, limitations and notable facts

• Advantages: dispatchable renewable power (due to storage), higher capacity factor than many solar PV installations, modular expansion by adding units.
• Limitations: higher initial capital cost than utility-scale PV per installed megawatt, land and water requirements for cooling and cleaning, and dependence on direct normal irradiance (DNI) which favors sunny, dry locations.
• Notable: Andasol's use of molten-salt storage demonstrated how thermal energy storage can expand the usefulness of solar energy for grid balancing and evening demand.

Further information

For additional background on the site and technology, see regional resources and project summaries at linked reference. The Andasol plants remain frequently cited examples when discussing concentrated solar power with thermal storage.