Linear Fresnel Reflector

 Continued from Part 4

(This is a series of articles on the various technologies that can be employed to trap the sun’s energy. This is the 5th part of the series.)

A Linear Fresnel Reflector is another type of solar power collector. It uses flat mirrors as opposed to parabolic mirrors that are used in solar parabolic troughs. The basic principle remains the same with the mirrors collecting solar power which is then utilized to generate steam which in turn drives a turbine. This technology leads to the production of steam directly and do not use heat transfer fluid or other medium. The sunlight that is concentrated with the help of mirrors boils the water which is present in the receiver tubes thereby generating steam. No heat exchangers are used in this system.

A linear Fresnel reflector works by utilizing the Fresnel lens effect which was first developed by French physicist Augustin-Jean Fresnel. The design allows the construction of lenses of large aperture and short focal length without the mass and volume of material that would be required by a lens of conventional design. It helps in cost reduction as parabolic reflectors proved to be costly. However, nowadays since the advent of nanotechnology, the cost has come down.

One big disadvantage with this design is the shading effect of adjacent mirrors which can be encountered only by utilizing more ground space which increases costs.

Advantages:

1. Flat mirrors are used which are cheaper and that more reflectors can be placed in the same amount of space, this allows more efficient utilization of the sunshine available.
2. Structure used is much simpler, single absorber tube can be shared between several mirrors. Maintenance costs will also be less.
3. Linear Fresnel Reflectors generally produce steam directly and do away with the requirement of expensive heat exchangers.
4. Land use is less because of efficient use of space. Leveling of land is not necessary and thus less expensive.
5. No use of toxic materials.

Disadvantages:

1. To avoid shading, mirrors need to be spaced in a greater area which requires more land and thus increases costs.
2. Very high temperatures are not produced as compared to a parabolic trough or a sterling dish and therefore the efficiency is less.

Image credit: kenneyjr, on Wikimedia

Read part 1, part 2 and part 3