Parabolic Trough Power Plant Solar Fields.

The solar field of a parabolic trough power plant is comprised of many rows of parabolic troughs around six meters high and several hundred meters long. Despite their enormous size, these high-precision optical devices are aligned with millimeter precision. The rows run in a north-south direction and track the sun from east to west during the course of the day.

Special components are used for the collectors. The concave mirrors are made from silver-coated white glass which is about 4 to 5 mm thick and 2 to 2.8 square meters in size. Over 98% of the solar radiation that arrives at the mirrors is reflected onto the absorber pipe along the focal line of the collectors. The absorber pipes contain a heat transfer medium which is heated to around 400 °C by the concentrated sunlight.

The absorber pipes, also known as receivers, consist of a metal pipe which contains the heat transfer medium, surrounded by a glass pipe. Between the two pipes is a vacuum which insulates the metal pipe, thus reducing heat loss. The glass pipe is composed of special materials and coatings to enable as much solar radiation as possible passing through to be absorbed by the metal pipe rather than being reflected.

7,488 collector elements need to be assembled on site for a solar field the size of one of the Andasol power plants. They are then hung between the supports in the solar field, connected to the oil circuit and put into operation.