PV module reliability is alsways an important issue for PV industry. In an outdoor PV system, PV modules suffer from degradation due to different factors. It is then very important to determine the loss mechanisms of a PV module and making improvement based on this. It is found in this work that due to mismatch effect, using fitting method to extract I-V characteristics might not be well applied on a PV module, especially when it has non-uniform degradation problem. This work proposes a method to accurately quantify the power loss of PV modules due to different degradation mechanisms, including series resistance (Rs) loss, non-uniform shunting loss and number of shunted cells, uniform shunting loss, uniform current loss, non-uniform current (mismatch) loss, recombination current (J01 and J02) losses of a PV module. All required input information are the measured current-voltage (I-V) curves and short circuit current- open circuit voltage (Isc-Voc) of PV module initial state and final state. The method is first applied to a simulated PV module with various degradation problems. Power loss due to each loss mechanism for the simulated PV module is then extracted using the proposed method and a pie chart can be generated. Comparing with the actual power loss on each loss mechanism, the method proposed in this work is proved to be very accurate. The method is then further applied to a degradated PV module istalled in an outdoor PV system. The power loss on series resistance, shunting and current mismatch are effectively identified and the number of shunted cells is accurately calculated. In the real application, this method can be used in both indoor and outdoor characterization, which can be very beneficial for PV degradation analysis of PV modules and systems.
In this work, the use of manufacturing metrology across the supply chain to improve crystalline silicon (c-Si) photovoltaic (PV) module reliability and durability is addressed. Additionally, an overview and summary of a recent extensive literature survey of relevant measurement techniques aimed at reducing or eliminating the probability of field failures is presented. An assessment of potential gaps is also given, wherein the PV community could benefit from new research and demonstration efforts. This review is divided into three primary areas representing different parts of the c-Si PV supply chain: (1) feedstock production, crystallization and wafering; (2) cell manufacturing; and (3) module manufacturing.