EFFECTS OF SOLAR IRRADIATION CONDITIONS AND OTHER FACTORS ON THE OUTDOOR PERFORMANCE OF PHOTOVOLTAIC MODULES

The operating efficiency of an installed photovoltaic module is not well predicted by its datasheet, related to standard test conditions: normal and unpolarized light, 1000 W/m of irradiance, AM1.5 spectrum and 25 ◦C of cell temperature. These reference conditions in fact are hardly attainable in the field as they combine the irradiance of a clear summer day with the module temperature of a clear winter day and spectrum of a clear spring day. Thus, the energy supplied by the module in the field can be 30 % lower than expected. From this point of view, it is of great importance to reveal the characteristics of photovoltaic modules in actual use conditions for a long-term period. This long-term investigation of photovoltaic modules, however, will give more reliable information about their practical performance than indoor measurement as the modules experience seasonal changes all the year. This study illustrates a comprehensive experimental study of the effects of environmental factors on both the efficiency and electrical power output of photovoltaic modules. Atmospheric conditions, angle of incidence, solar position, orientation of the cell, and cell temperature are considered as the key environmental parameters in this study.

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