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TECHNICAL BRIEFS

# Annular Compound Parabolic Concentrator

[+] Author and Article Information
W. Lipiński

Solar Technology Laboratory, Paul Scherrer Institute, 5232 Villigen, Switzerland

A. Steinfeld

Department of Mechanical and Process Engineering, ETH— Swiss Federal Institute of Technology Zurich, CH-8092 Zurich, Switzerlandaldo.steinfeld@eth.ch

To a good approximation, sun rays can be assumed to originate in a disk that subtends a solid angle $θsun$ of $0.0093rad$. When sun rays are incident on a perfect specular and reflective paraboloidal mirror, their reflection at the focal plane forms a circular image of diameter $d$ given by

$d=fθsuncosΦrim(1+cosΦrim)$
where $Φrim$ is the rim angle of the parabolic mirror and $f$ its focal distance. On this circle, the radiation flux intensity is maximum and uniform in the paraxial solar image (the “hot spot,”), and decreases for diameters larger than $fθsun$ as a result of elliptical images being produced. Because of optical imperfections, it approaches a Gaussian distribution.

Skew rays are rays that do not belong to the plane containing the axis of the A-CPC.

J. Sol. Energy Eng 128(1), 121-124 (Mar 08, 2005) (4 pages) doi:10.1115/1.2148970 History: Received October 06, 2004; Revised March 08, 2005

## Abstract

The annular compound parabolic concentrator (CPC) is a body of revolution consisting of two axisymmetric surfaces produced by rotating a classical two-dimensional CPC around an axis parallel to the CPCs axis. Its ability to further concentrate incoming radiation when used in tandem with a primary solar parabolic concentrator is analyzed by the Monte Carlo ray-tracing technique. Potential applications are found in capturing the annular portion of primary concentrated solar radiation and augmenting its power flux intensity.

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## Figures

Figure 1

(a) 3D-CPC; (b) 2D-CPC; (c) A-CPC

Figure 2

Variation of the transmission efficiency η as a function of the cone angle of incident radiation θ, for the baseline configuration (R2∕R1=3,ρ=1). The parameter is the half acceptance angle α=30°,45°, and 60°.

Figure 3

Variation of the transmission efficiency η as a function of the cone angle of incident radiation θ, for the baseline configuration (R2∕R1=3,α=45°). The parameter is the reflectivity ρ=0.7,0.8,0.9, and 1.0.

Figure 4

Variation of the transmission efficiency η as a function of the radii ratio R2∕R1, for the baseline configuration (ρ=1.0,α=45°) and for incident radiation with cone angle θ=60°

Figure 5

Artist view of a 3D-CPC combined with an A-CPC for efficient absorption of concentrated radiation having a Gaussian power flux distribution

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