via e-mail. Parabolic trough collector acceptance angle test results. Acceptance angle is the maximum angle at which incoming sunlight can be captured by a solar concentrator. The half acceptance angle θ is usually chosen to correspond to between two and three times the half angular width of the sun (0.27 degrees). of n2 = 1.4. A further possibility would be to seek ways to bring the focusing parabola closer to the concentration limit of Eq. Learn how your comment data is processed. However, other errors also affect the acceptance angle. Figure "angular aperture of sunlight" on the right shows the effect of the angular dispersion of sunlight on the acceptance angle. Therefore, for incidence angles α < θ all light is captured while for incidence angles α > θ all light is lost. After you have modified some values, click a "calc" button to recalculate the field left of it. All rays end up on the receiver and, therefore, all light is captured. As your inputs are first reviewed by the author, they may be published with some delay. Note: this box searches only for keywords in the titles of encyclopedia articles. Questions and Comments from Users. This diffraction places a fundamental limit on the ability of a lens to resolve fine detail. The reflecting light is called a phase conjugate wave. © 1999-2006 Doris Jeanne Wagner and Rensselaer Polytechnic Institute. Definition: the maximum incidence angle of a light ray which can be used for injecting light into a fiber core or waveguide, German: Akzeptanzwinkel in der Faseroptik, How to cite the article; suggest additional literature. However, optimal orientation needs to be selected to achieve maximal concentration gains. The refractive index of the launching medium is n 0. If θz and γs are the azimuth and zenith angle of sunlight, respectively, only when θz and γs, respectively, meet certain conditions can sunlight be reflected to the receiver. An optical element which transmits some percentage of a laser beam away from the optical axis or point of incidence. follows: Copyright where TR is the absolute temperature of the receiver and Ts is the temperature of the sun’s surface. will be trapped (Figure B). In Fiber optics, the cone within which Optical Power may be coupled into the bound Modes of an optical fiber. It is also important for your physics test. This means that all HCPV systems must track the sun in both azimuth and elevation, and the smaller the acceptance angle is, the more accurate the tracking has to be. Radiation flux from a spherically symmetric black body falls off as 1/R2. Today let us discuss the terms related to fiber: Numerical Aperture (NA): NA is the light gathering ability or capacity of an optical fiber. Formation of an image on a curved surface, an optical behavior inherent to refractive imaging optics. between 28° and 62°, probably closer to 28°. John F. Ready, in Industrial Applications of Lasers (Second Edition), 1997. will escape the fiber (Figure A), while light striking the interface with For line-focus systems, such as a trough concentrator or a linear Fresnel lens, the acceptance angle is one dimensional, and the concentration has only weak dependence on off-pointing perpendicular to the focus direction. This site uses Akismet to reduce spam. Conventional focusing optics, like that of the parabolic troughs widely used today, falls way short of this limit. which defines a quantity CAP (concentration acceptance product), which must be smaller than the refractive index of the medium in which the receiver is immersed. For diffuse radiation, only some part of diffuse light entering the CPC can reach the receiver, called effective diffuse radiation. Please do not enter personal data here; we would otherwise delete it soon. Direct and indirect sunlight entering a CPC could be influenced by the cover, and the degree of influence relies on the transmittance of cover τc. Sunlight is not a set of perfectly parallel rays (shown in blue), but it has a given angular aperture θS, as indicated by the green rays. The maximum incidence angle of a light ray which can be used for injecting light into a fiber core or waveguide is know as Acceptance Angle. We can calculate the exact number as For a linear-focused concentrator, the equation is not squared. Acceptance cone: It is the cone in which the light incident at acceptance angle or less than the acceptance angle and then the light can propagate through the fiber after total internal reflection. For linear concentrators, once again it is the acceptance angle that matters and this is effectively 90° in the plane of the sun and linear receiver, so concentrating light from the sun is still limited by Eq. Your email address will not be published.