Solar Energy Perspectives - IEA

Chapter 7: Solar heat
Photo 7.6 Possible future mirror-film troughs, pictured in a stadium for illustration
Source: SkyTrough®.
Key point
Parabolic troughs are mature linear concentrating devices.
Figure 7.7 Compact linear Fresnel reflectors
Mirrors
Absorber tube
and reconcentrator
Key point
Linear Fresnel reflectors are less costly than troughs but less effective when the sun is low.
Linear Fresnel reflectors have a lower optical efficiency than troughs, due to greater cosine
losses, if one compares the efficiency in the capture of the energy that falls within the
apparatus. This makes them less effective than troughs at times of low sun, in the early
morning and late afternoon. However, they offer a smaller footprint than other technologies,
as the high position of the receiver allows the troughs to be installed close to each other. They
are less costly to build than parabolic troughs, and can use CPC collectors around the
receiver to somewhat increase concentration levels. They usually have very effective back
side insulation. The fixed receiver allows for high pressure and thus direct steam generation.
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© OECD/IEA, 2011