Attaining and using extremely high intensities of solar energy with non-imaging concentrators

Using the principles and techniques of non-imaging optics, solar concentrations that approach the theoretical maximum can be achieved. In this paper, the authors review recent progress in attaining, measuring, and using such ultrahigh solar fluxes. In particular, they review the design principles for optimized two-stage concentrators and solar furnaces and discuss the characteristics and properties of a variety of non-imaging secondaries which have been employed. These include Compound Parabolic Concentrators (CPC) type secondaries, Dielectric Totally Internally Reflecting Concentrators (DTIRC), and flow-line or {open_quotes}trumpet{close_quotes} concentrators. The usual design is a configuration where {phi}, the rim angle of the primary, is small, that is, corresponding to a system with a relatively large focal length to diameter (F/D) ratio. All three types of secondary are characterized by a design acceptance angle {phi}{sub a} which must be greater than or equal to {phi}. The design parameters and trade-offs for each of these systems including strategies for choice of particular secondary and degree of truncation, are presented. The authors review the calorimetric techniques used to measure these high intensities and describe a newly developed technique for {open_quotes}extracting{close_quotes} light from inside a high index medium. Finally they review a number of potential applications for highly concentratedmore » solar energy and the current status of the associated technology. By making possible new and unique applications for intense solar flux, these techniques have opened a whole new frontier for research and development of potential economic uses of solar energy. 63 refs., 34 figs., 3 tabs.« less