Annual energy losses due to partial shading in PV modules with cut wafer-based Si solar cells

To further improve the efficiency of the wafer-based silicon photovoltaic (PV) module, producers are introducing new module designs with cut-cells. Since smaller solar cells might be affected by partial shading even more and earlier than full-size cells, the energy performance simulations of partially shaded modules are crucial. A detailed shading analyses of partially shaded modules with different cut cell designs are presented not only on a single case scenario but on annual energy yield simulations using Spice, where a shading scenario over the whole module by the use of a new 3D shading horizon profile of selected shading objects is calculated. The annual simulations reveal that regardless the module design almost all cells in the module are confronted by reverse bias, which can deteriorate the module performance significantly. Simulation results with three different shading objects on five different module topologies at five locations showed that the best cut-cell module design depends strongly by the micro location and shading objectshowever, in general the string of solar cells connected in series should be aligned with the shading shape around noontime as much as possible. A comprehensive annual energy performance evaluation of partially shaded cut-cell modules revealedthat with a correct cell layout of cut-cells in a PV module, the shading losses can be reduced by 30e50% if comparing to the standard PV module design

Stress induced inhomogeneities in crystalline silicon solar cells

In this contribution we present a fully scalable, quasi-SPICE distributed modelling approach for a wholesome analysis of stress induced, as well as inherent inhomogeneities (material impurities, grain boundaries) in silicon solar cells and PV modules based on electroluminescence imaging. We describe the derivation of electrical models for different IEC TS 60904-13 recognised stress induced inhomogeneities, namely the active and the inactive cracks, dead cell areas, and contact finger interruptions, and highlight their effects on the current-voltage characteristic of the cell. We validate our model on a selection of experimental cases of sample silicon solar cells on the basis of a comparative study of current-voltage characteristics and electroluminescence images. We demonstrate the applicability of our model on a complexly damaged full-sized sample cell, showing excellent agreement with the measurements

Cut out for efficiency

In our work we aim to, with the help of numerical modelling on one side and subsequent correlation with spatially resolved measurements on the other, qualitatively evaluate and quantitatively determine the recombination parameters of cut edges of silicon solar cells, which govern the efficiency decreases of cut-cells obtained by different cell separation techniques (cleaving, laser ablation and cleaving, thermal laser separation). With the proposed approach, we were able to recreate an LBIC scan of a healthy part of a separated Zebra IBC cell in high detail

Detailed luminescence modelling in high-efficiency solar cells for precise calibration of spatially resolved characterisation methods

In the scope of solar cell characterisation, spatially resolved imaging (SRI) methods (EL, PL and LBIC) have long been a standard procedure for valuable in-depth evaluation and extraction of various spatially resolved material properties, especially those related to the electrical behaviour. While this extraction can be straightforward in the case of laterally homogeneous devices, the situation is vastly different when the structural features are laterally varying, such as in the case of interdigitated back contact (IBC) solar cells. We show that in the case of laterally varying devices inherent device optical properties play a far more important role in determining the measured profile in this case and may indeed overshadow any underlying electrical effects. We therefore propose and validate a methodology that couples SRI characterisation with advanced bottom-up simulation of IBC solar cells. The method fully accounts for lateral device variability and allows for accurate extraction of the underlying electrical phenomena. We demonstrate the applicability of the method on state-of-the-art high-efficiency IBC solar cells, and explain the key factors, which could lead to misinterpretation of the results obtained solely by SRI measurements

Electroluminescence imaging of PV devices

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