Spain to spin turbines with solar steam

Currently under construction in one of the sunniest parts of Spain – the desert-like heights of the Sierra Nevada in Andalusia – Andasol will be the largest solar energy plant in Europe, and one of the largest in the world, when completed in 2009. It also will be Europe's first and the world’s second solar energy plant to use parabolic troughs to capture solar radiation and generate electricity on a commercial scale. (The first is the 64 MW Nevada Solar One in the United States.)

Andasol 1 and 2 will each generate 50 MW of renewable electricity by concentrating sunlight in two vast solar fields of trough-shaped parabolic mirrors. The technology collects the solar radiation as heat, which is pumped to adjacent power plants where it generates electric power from steam turbines.

Parabolic trough power plants use concentrated sunlight in place of fossil fuels to generate steam to drive turbines in adjacent conventional thermal power plants. A large field of parabolic trough mirrors tracks the sun and concentrates solar radiation on a collector tube installed at the focus of the mirrors. Heat-transfer fluid passing through the collector tube is heated to temperatures high enough to generate steam. 

Each power plant will have its own 200-hectare (494 acres) solar field containing 624 parabolic troughs arranged in 156 loops. The fields produce twice the thermal energy that the plants’ steam turbines can absorb. The excess energy is stored in liquid salt tanks for as long as seven hours, thereby ensuring a continuous and stable supply of electric power to the grid.

The plants will produce about 350 gigawatt-hours of electricity per year, controlled by ABB’s Extended Automation System 800xA and ABB Power Generation Portal software.