Compound parabolic collectors design

The photoreactivity experiments were carried out by using compound parabolic collectors (CPC), installed at the Plataforma Solar de Almeria (PSA, Spain). CPCs are static collectors with a reflective surface formed by two connected parabolic mirrors with an absorber tube in the focus. They have no tracking system and their design allows the solar rays to be reflected onto the absorber tube, attaining a low concentration factor, defined as the ratio of the collector aperture to the absorber perimeter (it is usually 1-1.5 depending on the application). 

Compound parabolic collectors (CPCs) belong to the most promising photocatalytic solar reactors which combine the advantages of parabolic trough concentrator and non-concentrating system [178]. CPCs are low-concentration static collectors with reflective surface and can be designed for any given reactor shape (see Fig. 7.3a) [182]. The CPC reflectors are usually made from polished aluminum... 

Compound parabolic concentrators permit the use of low to moderate levels of concentration for solar thermal collectors without the requirement of diurnal tracking. When used in conjunction with an evacuated absorber with selective surfaces, a fully stationary CPC (designs with concentrations of l.l-1.4x are now commercially available) has a typical efficiency of about 40% at 150°C (270°F) above ambient with available conventional materials. An experimental 5x CPC requiring approximately 12 tilt adjustments annually, when used with a similar available evacuated absorber, has a measured efficiency of 60% at 220°C above ambient and is capable of efficiencies near 50% at 300°C. With such thermally efficient absorbers, higher concentrations are not necessary or desirable. 

Rabl, A., O Gallagher, J., and Winston, R. (1980). Design and test of non-evacuated solar collectors with compound parabolic concentrators, Solar Energy 25,335. 

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