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Concentrating Solar Power

Parabolic Trough

Trough technology is a clean and mature solar power solution with years of successful power generation behind it. Troughs have been in use since the 80s with outstanding results. The technology has been improving steadily for the last 30 years, and modern troughs operate more efficiently at lower cost. Today, there is more than 300 MW of CSP trough power in operation around the world, with 400 MW under construction and around 6 GW in development.

Introduction to Technology

A parabolic trough is a large, curved mirror that sits on a motorized base, allowing it to follow the movement of the sun throughout the day. The mirror's unique parabolic shape is designed to gather a great deal of sunlight and then reflect that light onto a single point, concentrating the solar power.

A receiver tube sits at the point where the mirror concentrates all the sunlight. The tube is filled with a synthetic heat transfer oil, heated by the mirror's light to around 750 F (400 C). This superheated oil is then pumped from the solar field to a nearby power block, where the oil's heat is converted to high-pressure steam in a series of heat exchangers. This steam pushes a conventional steam turbine, creating electricity.

Parabolic trough technology is the most developed CSP technology, and has been a major focus of Abengoa Solar's research efforts. Abengoa Solar is currently deploying parabolic troughs at the SolĂșcar Platform outside of Seville, Spain a collection of five 50 MW plants. Continue on [link] for more information about Abengoa Solar's use of parabolic trough CSP technology around the world.

Parabolic trough technology

Operating Scheme for parabolic trough technology

The main components of parabolic trough technology are:

  • The parabolic trough reflector: The cylindrical parabolic reflector reflects incident sunlight from its surface onto the receiver at the focal point. Typically, the reflector is made of thick glass silver mirrors formed into the shape of a parabola. Alternatively, mirrors can be made from thin glass, plastic films or polished metals.
  • The receiver tube or heat collection element: The receiver tube consists of a metal absorber surrounded by a glass envelope. The absorber is coated with a selective coating to maximize energy collection and to minimize heat loss. The glass envelope is used to insulate the absorber from heat loss, and is typically coated with an anti-reflective surface to increase the transmittance of light through the glass to the absorber. For high temperature CSP applications, the space between the absorber and glass tube is evacuated to form a vacuum.
  • The suntracking system: An electronic control system and associated mechanical drive system is used to focus the reflector onto the sun.
  • The support structure: Typically made of metal, the collector support structure holds the mirrors in accurate alignment while resisting the effects of the wind.
    Abengoa Solar parabolic trough models are:
Parabolic trough

Parabolic trough on
Solnova 1

Solnova 1, 3 and 4, with 50 MW each, are the first three parabolic trough technology-based plants of a total of 5. At Abengoa Solar, we believe in this technology, and for this reason have research groups focused on parabolic trough technology.

  • For more information about tower technology, please download our Trough Technology White-paper




The Most Mature CSP Technology

The first commercial CSP plants were parabolic trough collector systems installed in the United Sates in the 1980’s. Continued research since that time has improved the technology making it more reliable and efficient. Troughs remain the most developed and commercially-ready CSP technology.

Requirements

Solnova I

Solnova I

Regarding Trough. technology, there are several variables to be analyzed when defining an installation. The most important requirements for a C.S.P. plant are:

  • Topography: the site needs to be level, preferably with a slope less than 1%
  • Irradiation: the direct normal insolation (DNI) should be a high as possible
  • Water Availability: water is needed for cooling in the power block
  • Electric Transmission: electric lines and transmission capacity are needed to convey solar power from the plant to the consumer


Land Requirements for 100 MW Plants

Requirements for 100 MW Plants

Individual parabolic trough collector modules are attached together to form a “collector” that can be from 100 to 150 m long. Collectors are configured together to form a collector row. Parabolic trough plants are made up of many parallel collector rows covering large rectangular areas of land. The table below shows the approximate surface of land needed for plant construction. Besides the surface specifications (acres), the approximate width (x in m) and length (y in m) of an intended rectangular plot have been included.

Requirements for 100 MW Plants
100 MWBasic TroughTrough w/storage 7 hs
Land requirements475 acre
x=4000 ft
y=5167 ft
940 acres
x=5150 ft
y=8050 ft