Technologies

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Concentrated Solar Power

Parabolic Trough Technology

Trough technology is a mature and clean with years of tracked records that demonstrate to be ready for large scale installation.
The technology has been installed from the 80s with an outstanding performance. Since then, the technology has suffered large improvements, reducing costs and increasing efficiencies. Nowadays more than 300 MW are in operation, 400 under construction and around 6 GWs in development.

Introduction to Technology

A parabolic trough is a solar concentrator that follows or tracks the sun around a single, rotational axis. Sunlight is reflected from parabolic-shaped mirrors and is concentrated many times onto the receiver tube at the focal point of the parabola. For CSP applications, synthetic heat transfer oil pumped through the receiver tube and is heated to approximately 752 F (400 C). The oil transports the heat from the solar field to the power block where the energy is converted to high-pressure steam in a series of heat exchangers. This steam is converted into electrical energy using a conventional steam turbine.

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:
• Solúcar TR
• PT1
• RMT

Solnova 1 and III are the first of a total of five 50 MW plants to be deployed at the Sanlucar Plataforma Solar outside of Seville, Spain. Parabolic trough technology is the most developed CSP technology and hence has been a major focus of our research efforts.

• 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

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

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.

100 MW	Basic Trough	Trough w/storage 7 hs
Land requirements	475 acre x=4000 ft y=5167 ft	940 acres x=5150 ft y=8050 ft

Links

Download our White Paper on Trough Technology