Optical modeling of four Fresnel-based high-CPV units

Abstract

High Concentrator Photovoltaic (HCPV) units are typically based on the use of Fresnel lenses, refractive secondary optical elements (SOE), and triple-junction (TJ) solar cells. In this work, a detailed optical modeling is applied to analyze the performance of four Fresnel-based HCPV units equipped with different refractive SOEs while considering the subcells current density generation. Wavelength-dependent material properties are utilized while simulating the optical performance. The spectral response of a typical TJ solar cell is also included. This modeling allows to establish the subcell current limitation and the spectral matching ratio, SMR, values in each case. The following SOEs have been used for simulating the HCPV units: (i) Dielectric-cross compound-parabolic-concentrator (DCCPC), (ii) (SIngle-Lens-Optical element) SILO-Pyramid, (iii) Refractive truncated pyramid (RTP) and, (iv) Trumpet. Results show that the HCPV units with SOEs RTP and Trumpet, exhibit bottom subcell current limitation and lowest optical polychromatic efficiency, this is partly due to the irradiance absorption in the bottom cell spectral region and longer optical path length of the concentrated rays within the SOE material. In the case of the HCPV unit with the DCCPC SOE, top and bottom subcells limit the current generation alternatively depending on the misalignment angle of the HCPV unit respect to the simulated sunrays. None of the SMR parameters are equal to 1 under normal alignment of the HCPV units. The short-circuit current density distributions for each subcell in each case are studied under normal alignment and under 1°of misalignment angle.

Concentrated photovoltaic thermal systems: A component-by-component view on the developments in the design, heat transfer medium and applications

“…The cell configuration with lower number of cells had more radiative losses as it was exposed more to the surroundings and higher number of cells produced more electrical power output [19]. Srivastava et al [15] modelled four secondary optical elements(SOE) for a HCPV system as shown in Fig.1. The SOEs varied in volume and height.…”

“…Fig.1. Secondary Optical Elements design for acceptance angle and uniform distribution of illumination [15].…”

Algorithmically Optimized Hemispherical Dome as a Secondary Optical Element for the Fresnel Lens Solar Concentrator

“…While it depends on the SOE size, the smaller this parameter is for the same acceptance angle, the higher the geometrical concentration ratio, , and the CAP values; 3. The SOE-receiver spacing, , which represents the vertical distance from the to the dome's bottom surface-taking that surface at a vertical distance from the Fresnel lens equal to the focal length [5,11,15].…”

“…For instance, a four-fold Fresnel-Kohler concentrator was designed by the edge-ray principle in a four-part symmetry relating the POE and the SOE [5][6][7]. On the same note, the edge-ray principle has been used in the SOE designs of a ball-lens [8,9], a dome [10,11], a kaleidoscope with a flat top surface [12][13][14][15][16][17][18] and a domed top surface [12][13][14]18,19], a half-egg [12,13], a refractive truncated pyramid (RTP) [15][16][17], a single-lens optical element (SILO) pyramid [15][16][17]19], and a refractive dielectric-crossed compound parabolic concentrator (DCCPC) [15][16][17].…”

“…The SOE-receiver spacing, SRS opt , which represents the vertical distance from the FS to the dome's bottom surface-taking that surface at a vertical distance from the Fresnel lens equal to the focal length [5,11,15]. SRS opt , as it also depends on the SOE size, can be further optimized by simulation for either a higher concentration of rays or a better focal irradiance homogeneity.…”