Compound parabolic concentrator

Figure 9.3. The FIRAS horn a compound parabolic concentrator with a trumpet bell flare to reduce sidelobes.

Blanco J, et al. Compound parabolic concentrator technology development to commercial solar detoxification applications. Sol Energy 1999 67 317-330. 

A compound parabolic concentrator (CPC), similar to one used for solar power concentration, was used to compress the beam from a transmitting optical fiber onto a small spot on the artery surface. This CPC was molded from a polymer and contained a polished aluminum lining. 

Another structure type suitable as an angle-selective reflector is the so-called compound parabolic concentrator (CPC) [16]. Light from a defined range of angles of incidence is reflected by total internal reflection on the parabolic walls of the CPC and concentrated at the exit of the CPC. If this exit is covered by a mirror then... 

The aim of the solar thermal collector development is to improve and optimize them for the temperature level from 80 °C to 250 °C. There are different approaches like double-glazed flat plate collectors with anti-reflection coated glazing, stationary compound parabolic concentrator (CPC) collectors, evacuated tube collectors, vacuum flat plate collectors, small parabolic trough collectors, linear concentrating Fresnel collectors and a concentrating collector with a stationary reflector. 

Compound parabolic concentrator Name given generi-cally to a class of nonimaging collectors with reflecting walls (not necessarily parabolic) that concentrate flux by the theoretical limit. 

Dielectric compound parabolic concentrator Nonimaging collector that operates by total internal reflection. 

Although the construction of Fig. 4a gives the two-dimensional compound parabolic concentrator, or CPC, rotating the profile about the axis of symmetry gives the three-dimensional CPC with diameter A at the entrance and A2 at the exit. The two-dimensional CPC is an ideal concentrator, that is, it works perfectly for all rays within the acceptance angle Oq. The three-dimensional CPC is very close to ideal. The flat absorber case is a natural candidate for rotating about the axis because the ratio of diameters (sin 0) agrees with the ratio of maximum skew. Other absorber shapes, such as circular cross-sections (Fig. 4d) (cylinders in two-dimensional, spheres in three-dimensional), do not have this correspondence because the area of the sphere is ttA, whereas the entrance aperture area is 7tA /A. 

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. 

O Gallagher, J., and Winston, R. (1983). Development of compound parabolic concentrators for solar energy, J. Ambient. Energy 4, 171. 

Average number of reflections on compound parabolic concentrator (CPQ mirror for B <9 < ) Average number of reflections on CPC mirror for B> B,. 

A third approach (47) is to place an inverted compound parabolic concentrator (CPC) in front of a detector with a response that is spatially uniform. The CPC restricts the incidence angle on the detector to a range such that the variation in the detector s Fresnel response is small (e.g., 1-3%). Raytraces of parallel light incident at four different angles on an inverted CPC with dc = 30° are shown in Fig. 5. 

Fig. 5. Raytrace of an inverted compound parabolic concentrator (CPC), with 9 = 30°, for meridional ray incidence angles of 20, 40, 60, and 80°. Note the limited incidence angle on the detector surface for 80° incidence on the CPC.

Fig. 6. Angular response of a hemiellipsoid reflectometer utilizing a bare photomultiplier tube (PMT) (left) or an inverted compound parabolic concentrator (CPC) with a PMT (right).

Robert Lodder [68] has been producing excellent results in the assessment of arterial walls for a decade. In this, the location and quantities of HDL, LDL, and apolipoproteins in living tissue were determined. A compound parabolic concentrator (CPC) was used to compress the beam from a transmitting optical fiber onto a small spot on the artery surface. Light in the 1100 to 2500 nm range was transmitted through the concentrator onto the exterior arterial wall. The scattered light was detected at the proximal end of the CPC by lead sulfide detectors, located off axis of the incident beam. False color maps are then produced wherein the types and amounts of each type of plaque are determined. 

K Tanaka, MTT Pacheco, JF Brennan III, I Itzkan, AJ Berger, RR Dasari, MS Feld. Compound parabolic concentrator probe for efficient light collection in spectroscopy of biological tissue. Appl Optics 35 758-763, 1996. 

Compound parabolic concentrator (CPC, also called Winston collector or Winston cone) [95-97] is a reflective nonimaging light concentrator intended to collect incident light from a spatial angle larger than that of imaging concentrators and to... 

R. Winston, Dielectric compound parabolic concentrators. Appl. Opt. 15(2), 291-293 (1976)... 

Tanaka K, Pacheco M, Brennan J, Itzkan I, Berger A, Dasari R and Feld MS (1996) Compound parabolic concentrator probe for efficient light collection in spec troscopy of biological tissue. Applied Optics 35(4) 758- 763. 

Vidal et al. presented the first pilot-plant study about solar photocatalysis for bacterial inactivation. Researchers constructed a new low-cost compound parabolic concentrator (CPC) prototype containing solar collector (Pyrex photoreactor tubes, aluminum reflective surface), flowmeter, pump, sensors (pH, O, T, UV radiation), pipes, fittings, and tanks (PVC). This solar photoreactor has an area of 4.5 m and it was tilted at local latitude to maximize the available solar irradiation. It was observed 5-log reduction for E. coli and Enterococcus faecalis (initial concentration lO -lO" CFU/cm ) after 30 min of solar irradiation (solar UV value 25 W/m )... 

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