Holistic opto-thermo-electrical analysis of a novel spectral beam splitting-based concentrating photovoltaic thermal system

Abstract

The spectral beam splitting (SBS) approach decouples the dependence between photovoltaic and photothermal conversions in a traditional photovoltaic thermal (PVT) system. And hence, it overcomes the inherent limitation of obtaining a low-quality thermal output from a conventional PVT system as the operational cell temperature limits the maximum attainable thermal output. However, the energy transfer and transformation are complex operations in an splitting-based PVT system. In the present work, a 2.3× concentration ratio compound parabolic collector (CPC) is truncated from a 2.8× concentration CPC. For the solar spectral splitting, a nanofluid-based optical filter inside a transparent borosilicate glass tube is used. Deionized water and ZnO nanofluid are employed as optical filters. A linked optical–thermal–electrical framework is developed and implemented to assess the performance of the devised physical model. The optical analysis used a Monte Carlo ray-tracing routine to determine the heat flux distribution on the cell and glass tube units. The average heat flux is then used in a quasi-dynamic thermal model to numerically solve for the cell temperature and temperature rise of the optical filter. Furthermore, for analytically calculating the electrical performance with cell temperature and incident solar radiation as known parameters, a five-parameter (1-diode/2-resistor) electrical model is utilized. The stated optical, thermal, and electrical models are validated against the experimental and numerical findings for a simple conventional collector. The developed model demonstrated optical filter’s prowess by transmitting solar rays within the spectral response range to the PV array while absorbing the remainder of the spectrum. Without splitting, average array temperatures are recorded as high as 360 K and 375 K during solar noon in January and June, respectively. However, when using the spectral splitting, the corresponding temperatures are 310 K and 328 K, respectively. Therefore, it is observed that while employing the splitting, the cell temperature is kept near the standard test temperature without using any additional passive or active cooling strategy. Moreover, the greatest cumulative temperature rise of deionized water and ZnO nanofluid at 1600 h in January is reported to be 35.62 K and 43.59 K, respectively. However, for the month of June, it is found to be 58.76 K and 71.88 K for deionized water and ZnO nanofluid, respectively.