Fresnel Reflectors

A linear Fresnel reflector power plant uses a series of long, narrow, shallow-curvature (or even flat) mirrors to focus light onto one or more linear receivers positioned above the mirrors. On top of the receiver a small parabolic mirror can be attached for further focusing the light. These systems aim to offer lower overall costs by sharing a receiver between several mirrors (as compared with trough and dish concepts), while still using the simple line-focus geometry with one axis for tracking. This is similar to the trough design and different from central towers and dishes with dual-axis. The receiver is stationary and so fluid couplings are not required as in troughs and dishes. The mirrors also do not need to support the receiver, so they are structurally simpler. When suitable aiming strategies are used i.e. mirrors aimed at different receivers at different times of day, this can allow a denser packing of mirrors on available land area.

 

Advantages and Disadvantages of a Fresnel Solar Power System

Advantages

  • A flat solar mirror as used in the solar fresnel technology is less expensive than the parabolic shaped solar mirror of theparabolic trough or the parabolic dish.
  • The absorber tube is simpler and less expensive than that of the parabolic trough system, because multiple solar mirrors reflect solar power to a single absorber tube and the absorber tube doesn't need couplings as the receiver tubes for the parabolic trough and parabolic dish systems do, because the absorber tube is fixed.
  • A linear solar fresnel solar plant can be hybridized with fossil fuel backup to be used for electrical generation when the sun isn't shining.
  • The flat solar fresnel reflectors don't need to support the absorber tube, so they are structurally simpler than the parabolic trough and parabolic dish systems.

Disadvantages

  • A linear solar fresnel solar plant doesn't produce a fluid temperature as high as the parabolic trough or parabolic dish solar concentrators, so its thermal efficiency for conversion of solar power to electricity is lower.

Status of Commercialization of Fresnel Solar Power Technology

The linear solar fresnel technology is not as commercially developed as either the parabolic trough or heliostat solar tower technologies, both of which have commercial solar power plants in place. A prototype fresnel solar plant with 100 meters of linear fresnel reflectors began operation in Almeria, Spain, in July 2007. A 177 MW solar fresnel solar power plant is scheduled to begin operations soon in California.