The view‐factor effect shaping ofI‐Vcharacteristics

Abstract

The diffuse radiation collected by PV modules is coupled with a view-factor of the module to sky, which varies across the module surface in multiple-row installations. The view-factor variation inflicts current mismatch between the module strings by virtue of the nonuniform solar flux absorbed by the module's cells, leading in turn to an overall reduction in performance. The following study establishes a theoretical framework for predicting the step-wise properties of the module I-V curve following the current mismatch induced by the view-factor. To illustrate the steps pattern, synthetic I-V curves are derived by using the 5-parameter PV cell single-diode model in conjunction with 3 additional parameters that account for the cell's avalanche breakdown.We investigate the steps pattern as well as the power losses incurred by the view-factor by simulating different types of PV deployments over a range diffuse radiation rates. For a tilted module installed on a horizontal plane, for instance, the study predicts a reduction in power ranging 2.8% to 25%, depending on the precentage diffuse radiation on the site in question. KEYWORDS current mismatch, diffuse irradiation, I-V curve steps, view-factor to sky

The Effect of Collector Shading and Masking on Optimized PV Field Designs

“…Not much attention has been paid in the past to the masking phenomenon and its effect on the power loss of PV systems. The detrimental effect associated with masking has been addressed in a recent work [3]. The article deals with the effect of uneven diffuse incident radiation on the PV cells within the module caused by the effect of the local view factor along the module's surface.…”

“…A general expression for the sky view factor developed in [3] pertains to any number N of PV cell rows in a module. Therefore, this expression may also apply to rows in a PV field containing N modules placed one above the other along the row width.…”

“…The second and subsequent collector rows are subject to shading and masking (expressed by the sky view factor) by the rows in front. Shading affects the direct beam radiation [1,2] and masking affects the diffuse incident radiation on the rows [3]. A design of PV fields must take into account the decrease in the incident radiation caused by these two effects and hence causing losses in the electrical energy generation.…”

“…In fact, the amount of masking on the collector varies along the collector width causing uneven incident diffuse radiation on the PV modules. The detrimental effect associated with masking has been addressed in a recent work which established the view-factor as an emerging topic of technical significance [3]. The article deals with the effect of uneven diffuse incident radiation on the PV cells within the module caused by the effect of the local view factor along the module's surface.…”

Power Performance of Bifacial c-Si PV Modules With Different Shading Ratios

“…In order to reduce electrical losses due to exposure to shade, bypass diodes are installed in the PV module. Typically, one bypass diode per 24 cells are installed in a 72-cell PV module [12], which leads to the minimization of electrical loss by allowing electricity flow through a bypass diode in the event of shade exposure. There has been extensive research on the power characteristics of conventional PV module power systems under shade conditions [13].…”