Nonimaging optics

As discussed in the previous section, one type of solar collector geometry that has been foimd to be very advantageous for solar photocatalysis is based on CPC (Blanco et. al., 1999), which are a type of nonimaging optical devices. 

Although different solar photoreactors have been developed in the last 20 years, each one with its own advantages and limitations, there is still room for new designs and innovative ideas. Nowadays, CPC appear as one of the most promising alternatives among solar photocatalytic reactors. The concepts of nonimaging optics, with its emphasis in efficient energy collection can also be a very useful in future developments. 

Nonimaging optics Optical theory and design that departs from traditional methods and develops techniques for maximizing the collecting power of concentrating elements and systems. 

Several years ago, our group at The University of Chicago set out to demonstrate the ability of nonimaging optics to concentrate sunlight at or near the theoretical limit implied by the sine law. Actually, we chose to immerse the hot zone in a refractive medium to further boost the limit by the square of the index of refraction. These have been small-scale roof-top experiments carried out by talented and dedicated graduate students. In the first round of experiments we attained 56,000 suns. This was a fairly conservative design where the nonimaging optical element was a hollow silver funnel filled with... 

The techniques of nonimaging optics are particularly valuable in space or lunar environments where the use of solar thermal energy has obvious advantages. Earlier preliminary studies have explored this concept for the produc-... 

Applications of the techniques of nonimaging optics in the design of solar thermal concentrators has resulted in significant performance improvements in conventional short focal length dish concentrators, dramatic changes in the approach to solar furnace design, and the establishment of new solar flux concentration records in air and in refractive media. These accomplishments in just over ten... 

Welford, W. T., and Winston, R. (1989). High Collection Nonimaging Optics, Academic Press, San Diego. 

Winston, R. (ed.), (1995). Selected papers on nonimaging optics, 6 P/ Milestone Series, MS 106, SPIE Opt. Engineering Press, Bellingham, WA. 

Winston, R. (ed.) (1999). Nonimaging optics Maximum efficiency light transfer, V, Proc. SPIE. 3781. Previous sessions are I, Proceedings SPIE 1528 (1991) II, Proceedings SPIE 2016 (1993) III Proceedings SPIE 2538 (1993) IV Proceedings SPIE 3139 (1997). 

Microsystem and nanosystem technologies applied to infrared photonic photodetectors open a pathway to a plethora of novel approaches and possibilities for improvement. Some of the concepts that emerged in the past decade enabled methods and techniques that were unimaginable not so long ago. It is sufficient to mention materials with photonic bandgap, metamaterials, plasmonics, but also nonimaging optics and transformation optics to see that the field is very much alive and that novel paradigms do appear in what very recently had appeared a mature and well established area with veiy little room for further development. 

J. Chaves, Introduction to Nonimaging Optics (CRC Press, Bocca Raton, 2008)... 

J.J. O Galagher, Nonimaging optics in Solar Energy (Morgan and Claypool, San Rafael,... 

R. Winston, J.C. Minano, P.G. Benitez, Nonimaging Optics (Academic Press, New York, 2005)... 

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