Dispersive Optical Systems for Highly-Concentrated Solar Spectrum Splitting: Concept, Design, and Performance Analyses

We present a concept design of a solar spectrum splitting system that enables highly-concentrated solar energy harvesting over the entire AM1.5 spectral range. After passing through an array of the dispersive optical system (DOS) module composed of a grating structure and dispersive prisms below a concentrating lens, incident sunlight can be separated into two wavelength bands of visible (VIS) and infrared (IR) ranges, which can then be focused onto corresponding solar receivers. Based on the spectral response of typical crystalline silicon solar cells, the VIS wavelength band is selected from 0.4 mu m to 1.2 mu m to contribute to photovoltaic (PV) conversion to generate electricity. Meanwhile, the IR band in longer wavelength ranges (1.2 mu m <= lambda <= 2.5 mu m), which does not contribute to PV conversion, can be simultaneously used for solar thermal applications such as water heating and thermoelectricity. In this paper, various design parameters (e.g., focal length of a concentrating lens, groove density of a grating, geometry of dispersive prisms, material combination of optical components, etc.) have been investigated to determine an optimum set of system configurations, using optical design software (Zemax OpticStudio 14.2). Our simulation studies validate that the DOS is able to split incident AM1.5 solar irradiance into the two wavelength bands of the VIS and IR ranges and focus each wavelength band with concentration factors as high as 798x and 755x on the same focal plane, respectively. Such high concentration factors for both wavelength bands can be actualized due to the additional optical components used-a grating structure and dispersive prisms, which allow to minimize optical aberrations through both diffraction and refraction. The proposed DOS, designed with commercially available optical components, has the potential to widen the use of the sun's spectrum by allowing effective PV conversion of solar cells under high concentration with tolerable optical system losses and concurrently converting the remaining solar irradiation into useful energy for a broad range of thermal applications.