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Research Papers

Optical Parameters in High-Efficiency Optical Receivers With a Parabolic Reflector Before and After Coating With Ag Film

[+] Author and Article Information
Chung Jui Lee

Industrial Technology Research Institute,
ITRI South Campus, Regional Industrial
Service Department,
Tainan 709, Taiwan
e-mail: chjlee@itri.org.tw

Jen Fin Lin

Department of Mechanical Engineering,
Center for Micro/Nano Science and Technology, Institute of Nanotechnology and
Microsystems Engineering,
National Cheng Kung University,
Tainan 701, Taiwan
e-mail: jflin@mail.ncku.edu.tw

1Corresponding author.

Contributed by the Solar Energy Division of ASME for publication in the Journal of Solar Energy Engineering. Manuscript received June 3, 2012; final manuscript received June 6, 2013; published online August 21, 2013. Assoc. Editor: Santiago Silvestre.

J. Sol. Energy Eng 136(2), 021003 (Aug 21, 2013) (15 pages) Paper No: SOL-12-1146; doi: 10.1115/1.4024924 History: Received June 03, 2012; Revised June 06, 2013

High-efficiency optical receivers before and after the coating of Ag film are composed of a parabolic reflector, a solid parabolic second optical element (SOE), and a Fresnel/aspheric concentrating lens. The optical receivers before the Ag-film coating are fabricated on a high-precision machine tool based on an optimum design attained from ray tracing software simulations. The real profiles of the reflector before and after coating the Ag film are found to be the average of the two orthogonal parabolic profiles. They are then compared to the perfect profile (without profile error and surface roughness) in order to investigate the influence of the profile error and the Ag film on optical performances. The optical parameters, including the total flux, the optical efficiency, and the maximum, minimum, and mean irradiances are evaluated for ray projection simulations in the ASTM G173-03 spectrum. Experiments for the same ray source are also carried out to compare with the simulation results. It is determined that Ag-film coating can improve the profile error and surface roughness of the reflector, thus resulting in all optical parameters being either equal to or higher than those of the reflector without Ag coating. The total flux and optical efficiency obtained from the module with the Fresnel lens has values relatively higher than those of the aspheric lens. The irradiance uniformity for the Fresnel lens is also determined to be better than that of the aspheric lens. The irradiance intensity of the reflector after coating the Ag film has a magnitude at various wavelengths higher than that of the reflector without the Ag-film coating. Due to the coating of the Ag film, the optical receiver shows an almost constant rise in optical efficiency for the two types of concentrating lenses. This characteristic is shown to be valid for both the simulation and experimental results.

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References

Figures

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Fig. 1

Framework of the proposed optical receiver

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Fig. 2

(a) Geometries of the reflector and SOE; (b) positions of the reflector and SOE; and (c) schematic diagram of the optical receiver

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Fig. 3

Design of the aspheric concentrating lens

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Fig. 4

Design of Fresnel lens. (a) Geometries of the Fresnel lens and the points for transmissivity measurement; (b) magnified drawings of the encircled local sections in (a).

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Fig. 5

Dimensions and surface profile of the parabolic reflector

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Fig. 6

The design and dimensions of the SOE

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Fig. 7

Transmissivity of the SOE at various wavelengths

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Fig. 8

Measurement of the reflector profile

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Fig. 9

(a) Surface profiles measured along the −Y-Y section before the Ag coating; (b) surface profiles in the reflector after coating the Ag

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Fig. 10

Magnifications of the profiles of the reflector in four directions; the profiles of the reflector (a) before and (b) after the Ag coating

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Fig. 11

(a) Designed profile and the real SOE profile; (b) errors in the SOE profile between the designed profile and the measurements

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Fig. 12

Variations of reflectance with wavelength for the optical receivers with the reflector (a) before and (b) after coating the Ag film

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Fig. 13

Ray tracings in the optical receiver and distribution of irradiances on the chip for (a) the ideal parabolic surface profile (b) the reflector profile before coating the Ag film, (c) the reflector profile after coating the Ag film; the surface profile with △/4 is given for both (b) and (c), and the Fresnel lens is used.

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Fig. 14

Ray tracings for light-collection receiver and distribution of irradiances on the chip surface for the reflector with (a) ideal parabolic profile, (b) the △/4 profile error before coating Ag, and (c) the △/4 profile error after coating Ag. The aspheric lens is assumed to have a sharp edge in the simulations.

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Fig. 15

Ray tracings for light-collection module and distribution of irradiances on the chip surface for the reflector with (a) ideal parabolic profile, (b) the △/4 profile error before coating Ag, and (c) the △/4 profile error after coating Ag. The aspheric lens is now prepared with a blunt edge in the simulations.

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Fig. 16

The reflectance of four metallic films obtained at various wavelengths of sun ray [46,52]

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Fig. 17

The photograph of the optical receiver

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Fig. 18

Irradiance intensities of the ASTM G173-3 ray source created by the optical receiver with the reflector (a) before and (b) after coating Ag film

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