A Three-Dimensional Radiation Transfer Model to Evaluate Performance of Compound Parabolic Concentrator-Based Photovoltaic Systems

Abstract

Abstract:In the past, two-dimensional radiation transfer models (2-D models) were widely used to investigate the optical performance of linear compound parabolic concentrators (CPCs), in which the radiation transfer on the cross-section of CPC troughs is considered. However, the photovoltaic efficiency of solar cells depends on the real incidence angle instead of the projection incidence angle, thus 2-D models can't reasonably evaluate the photovoltaic performance of CPC-based photovoltaic systems (CPVs). In this work, three-dimensional radiation transfer (3-D model) within CPC-θ a /θ e , the CPC with a maximum exit angle θ e for radiation within its acceptance angle (θ a ), is investigated by means of vector algebra, solar geometry and imaging principle of plane mirror, and effects of geometry of CPV-θ a /θ e on its annual electricity generation are studied. Analysis shows that, as compared to similar photovoltaic (PV) panels, the use of CPCs makes the incident angle of solar rays on solar cells increase thus lowers the photovoltaic conversion efficiency of solar cells. Calculations show that, 2-D models can reasonably predict the optical performance of CPVs, but such models always overestimate the photovoltaic performance of CPVs, and even can't predict the variation trend of annual power output of CPV-θ a /θ e with θ e . Results show that, for full CPV-θ a /θ e with a given θ a , the annual power output increases with θ e first and then comes to a halt as θ e > 83 • , whereas for truncated CPV-θ a /θ e with a given geometric concentration (C t ), the annual power output decreases with θ e .

Effect of Reflector Geometry in the Annual Received Radiation of Low Concentration Photovoltaic Systems

“…Considering anisotropic light sources, the concentrator factor related to typical MaReCo Solarus [22] structures is roughly 1.4 to 1.5 suns. In the results, this geometry will be considered as a standard geometry and it is schematically represented in Figure 8.…”

“…The acceptance angle between both controls the amount of light that can be reflected and finally end up on the receiver. The interesting fact is, only an incident ray that falls in the acceptance angle range will definitely be reflected by both reflectors and reach the receiver [22].…”

“…It is mainly designed for higher latitudes [22]. It is a non-tracking collector with a bifacial absorber.…”

“…In Figure 1, the basic shape of the collector is shown [22]. The aperture d2 in the bottom of Figure 1 is the distance between the focuses of the two parabolas, A and B, and it is the receiver (solar cells) location.…”

A Theoretical Study on Performance and Design Optimization of Linear Dielectric Compound Parabolic Concentrating Photovoltaic Systems

“…Yousef et al[9] tested a CPV (2.4×) with a polished stainless-steel reflector and found that, as compared to similar solar panels, the electricity from the CPV with and without cooling of solar cells was increased by 52% and 33%, respectively. These works indicated that reflective CPCs can increase the power output, but the increase factor was much less than the geometric concentration due to optical losses resulting from imperfect reflection of the solar rays on their way to the solar cells [10] and electrical losses resulting from higher cell temperatures, inhomogeneous irradiation and increased incidence angles on the solar cells [11][12][13]. The inhomogeneous irradiation on solar cells usually creates hotspots, leading to current mismatch and tending to reduce their power output and durability [14].…”