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Abstract: In a typical series-connected photovoltaic module with three bypass diodes, not all of the energy generated by the individual cells in the module can be collected when one or more of the cells in the module are partially shaded. In this work, various photovoltaic (PV) module layouts are investigated, using both full-size solar cells and halved solar cells. The performance of these module layouts is investigated under conditions where one or more cells in the module are partially shaded. A solar cell equivalent circuit model has been implemented in the SPICE soft ware Micro-Cap to investigate several different module configurations. Module configurations investigated include a standard 72-cell module with 3 bypass diodes, one new configuration with a series of six matrices (whereby each matrix consists of two parallel strings of 12 halved cells each) with 3 bypass diodes, and another configuration with a series of 72 cells (whereby each matrix consists of two halved cells in parallel) with 3 bypass diodes. In the simulation, a shadow with zero transmittance was simulated to pass over the area of one 6-inch full-size solar cell in the corner of the module from two orthogonal directions, and the maximum power was calculated for each of the investigated module configurations. Simulation results show that the series-parallel hybrid connection of cells within a module has a significant improvement on the power output of the PV module under partial shading conditions. [Copyright &y& Elsevier]

Abstract: Optical losses in a photovoltaic (PV) module consist of reflectance (R) losses and parasitic absorptance losses (Apara.mod) in the front layers of the module. In this paper, a method for quantifying the optical losses associated with the cover glass and the encapsulant material of silicon wafer based PV modules is presented. The method involves measuring the spectral reflectance (R) and the full-area external quantum efficiency (EQE) of a silicon wafer solar cell before and after encapsulation. The approach used is to first obtain the full-area internal quantum efficiency (IQE) of the cell using R and EQE of the cell before encapsulation. Assuming that the IQE of the cell is not changed by the encapsulation process, the spectrally resolved parasitic absorptance loss (Apara.mod) associated with the cover glass and the encapsulant material is calculated with the aid of EQE and R measurements of the encapsulated cell. Using this method, the optical losses (at near normal incidence) of single-cell monocrystalline silicon wafer PV modules with various glass structures (textured, planar, antireflection coated) and encapsulant materials (EVA, ionomer) are investigated and compared. Ionomer encapsulated modules are found to show higher Apara.mod because of a higher absorption coefficient of the material. Modules with textured glass show a higher Apara.mod due to the longer optical pathlength resulting from refraction of light at the glass-air interface. [Copyright &y& Elsevier]

Abstract: The sunbelt regions of the globe on either side of the equator represent a vast potential for the generation of photovoltaic (PV) electricity. However, PV modules deployed in tropical regions face a different set of environmental conditions than PV modules deployed in temperate regions where the majority of today''s PV markets exist. The tropical climate poses several unique challenges for PV modules. High year-round humidity is the greatest threat to PV module durability, while high ambient temperatures and highly diffuse light conditions can negatively affect PV module output power. Given this situation, SERIS is undertaking a research project to develop “Singapore modules” which are specifically tailored to perform better and last longer in tropical climates. This paper presents an overview of the scope of the project, as well as first key findings and results. The first phase of the project involved a detailed study of the state of the art in today''s PV module technologies. Ten different module technologies were chosen for evaluation, representing today''s most commonly used PV technologies. These commercial modules were subjected to standard accelerated aging tests, as well as tightened accelerated aging tests to identify strengths and weaknesses of the various technologies. Outdoor performance monitoring of each module type is also on-going. The results obtained during the first phase of the project are being used to guide the development of Singapore modules. First prototype Singapore modules have been fabricated, and a 10 kWp testbedding system has been installed in Singapore. [Copyright &y& Elsevier]

Abstract: Ten commercially available photovoltaic module technologies were selected for this study including five thin-film technologies and five silicon wafer based technologies. These modules were subjected to accelerated ageing tests in a dark climate chamber under conditions of 85C and 85% relative humidity and electrical bias for 650hours. The bias voltage±1000V DC was applied between the active circuit of each module and module frame to study the impact of electrical bias on PV module durability under hot and humid conditions. Module performance assessed with a Class A solar simulator under standard testing conditions (STC) showed the biased stressing condition in damp heat test could significantly degrade electrical performance and cause various defects such as delamination, glass surface deterioration, frame corrosion, and metal grid discoloration, depending on module type and bias polarity. [Copyright &y& Elsevier]