Climate-based technology screening and temperature-derating assessment of commercial PV modules under hot-arid conditions in Najaf, Iraq, using NREL SAM

Abstract

High ambient temperature is a major constraint on photovoltaic (PV) performance in hot desert regions, where modules are still often screened primarily by rated efficiency or total annual energy. The aim of study to describe the use of these resources for resource assessment and performance modeling is quite common, as with NSRDB-type data and a comparison between different commercial PV module technologies was conducted for the city of Najaf, Iraq, based on climate parameters and by employing the PV module simulation tool (NREL SAM) with MATLAB post-processing. All cases used the same weather file to remove the variability introduced by the climatic input to compare module technology and the temperature derating that happens to each one of them. This study presents a climate-based comparison of four commercial PV module technologies for Najaf, Iraq, using the National Renewable Energy Laboratory System Advisor Model (NREL SAM) with MATLAB postprocessing. A fixed-tilt, grid-connected rooftop PV system of about 10 kWp was modeled under identical location, orientation, inverter, loss, and grid assumptions. The cases comprised SunPower SPR-E19-310-COM and Jinko JKM400M-72L-V monocrystalline silicon modules, a Panasonic EVP370PK high-efficiency monocrystalline silicon module, and a First Solar FS-7550A-FT1 CdTe thin-film module. Annual AC energy, specific yield, DC capacity factor, performance ratio, the Pmax temperature coefficient, and deviation from standard test conditions (STC) were compared. SunPower and Jinko delivered the highest annual AC energy (18,731 and 18,720 kWh/year), largely because their installed DC capacities were slightly higher. After normalization by installed capacity, however, the CdTe module performed best, reaching a specific yield of 1,782 kWh/kWp/year, a performance ratio of 0.80, a Pmax temperature coefficient of −0.295 %/°C, and an STC deviation of −6.914 %. The results show that total annual energy is an inadequate sole criterion for module selection in this climate and that normalized yield, performance ratio, and temperature-related derating should also be considered. The conclusions apply to the four modules and system assumptions examined.