A Comprehensive Methodology for Outdoor and Indoor Degradation Studies on Photovoltaic Modules. Phinikarides, A., Makrides, G., & Georghiou, G. E In 3rd International Conference on Renewable Energy Sources & Energy Efficiency, pages 85–93, Nicosia, Cyprus, 2011.
A Comprehensive Methodology for Outdoor and Indoor Degradation Studies on Photovoltaic Modules [pdf]Paper  abstract   bibtex   
The scope of this paper is to present a methodology for evaluating the performance of photovoltaic (PV) modules installed outdoors on the plane of array (POA) and operating at maximum power point (MPP). The methodology is based on the installation of a 1 kWp, grid- connected photovoltaic system and 2 additional modules of the same make/model on the POA, with the additional modules connected to a computer controlled dc load. The dc load will keep each module operating at MPP, while performing I-V scans at regular intervals. This serves two purposes: a) the modules are operating and degrading as if they were connected to an inverter that keeps them at full load conditions and b) the I-V scans allow for the periodic measurement of the electrical characteristics of the PV modules, all essential in the study of their degradation. The additional modules will be periodically dismounted from the POA and put on a testbed, to acquire the STC (Standard Test Conditions) rating and the dark I-V characteristics, according to the IEC 60904-1 standard. The grid-connected system will serve as the basis for PV performance evaluation and degradation rate determination from a system standpoint. The paper will present important issues arising when comparing the outdoor and indoor measurements. These are: 1) the spectrum utilization, 2) how the time between when a module is dismounted from the POA and tested under the solar simulator can affect the internal stability of the module, 3) the I-V scanning sweep rate and, 4) the duration of the light pulses of the solar simulator and how the measured Pmax, with mismatch factor (MMF) corrections as described in standard IEC 60904-7, compares to the outdoor measurements of the PV technologies.

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