FRESNEL LENSES BASED ON NANO SHELL-SILVER COATED SILICA ARRAY FOR SOLAR CELLS APPLICATIONS

Abstract

Fresnel lenses are low-cost optical elements used for focusing sunlight to solar panels to ensure operation under high- ∞ux density. However, the conventional Fresnel lens has a relatively high material usage and hence contributes to additional e-ciency degradation. Moreover, traditional design of Fresnel lenses introduces additional prismatic facets, due to deviations in manufacturing, which re∞ect the light toward the back focal spot, leading to additional losses. In this paper, Fresnel lenses based on flnite arrays of Nano Shell-Silver Coated Silica (NSSCS) are proposed to overcome the aforementioned drawbacks from infrared regime through the visible band to the ultraviolet region. To identify re∞ection losses, material losses of the NSSCS array and rejection bands due to the NSSCS array arrangement, three unique electromagnetic (EM) approaches are invoked: Frequency Selective Surfaces (FSS) to determine re∞ection bands, Metamaterial (MTM) to specify material losses and Electromagnetic Band Gap (EBG) to locate the rejection band. The EM characteristics of the NSSCS array are evaluated for wavelengths ranging from 0.3m to 300m, using CST MicroWave Studio (CST MWS), which is based on the Finite Integration Technique (FIT). It is found that the NSSCS array exhibits excellent transmittance within two bands, one from 545nm to 857nm and the other from 444.5nm to 480nm, for angles ranging from 0 - to 180 - along the azimuth and elevation. The efiective refractive index (nefi ) spectra showed that the NSSCS array does not provide a negative for its real (nefi ) part over the considered wavelength band. The imaginary part of (nefi ) value is found to be almost insigniflcant, between 0.857m to 1.714m and 316nm to 414nm and lossy elsewhere. In general, the NSSCS array shows no speciflc stop band over the considered frequency