Lengthy-term evaluation of PV panel degradation underneath sizzling, humid tropical climates – pv journal Worldwide
A Dutch-Hungarian research team has been measuring the degradation rates of PV modules installed in an off-grid system in Ghana for 12 years. The panels were found to have an average annual decrease in power efficiency of 3.19%.
18th November 2020
Scientists from the Hungarian Szent István University and the Technical University of Eindhoven in the Netherlands carried out a 12-year assessment of the deterioration rates of solar modules on an off-grid solar power generator in Koforidua in eastern Ghana.
The main goal of the research was to measure the degree of degradation of PV modules in hot, humid and tropical climates.
The floor-mounted PV system is based on 50 W solar modules from the US manufacturer Helios, which are mounted at an angle of 15 degrees. “Each PV module consists of a toughened front glass, ethylene vinyl acetate (EVA) encapsulant, polymer backing sheet and aluminum frame,” explained the researchers, adding that all modules were electrically isolated from each other and examined individually.
The IV and PV properties of the modules were measured simultaneously with the irradiation data and the temperature of the panels by an IV curve plotter. Temperature sensors were also attached to the rear of the modules and thermographic analysis was performed with an infrared (IR) camera. “The IR images show PV modules that are affected by hotspots, inhomogeneity in cell temperature, bypass diodes with open circuits, potentially induced degradation and cell breakage [and] heated bypass diodes and cables, ”said the scientists.
Measurements were taken at noon and on a clear day in order to avoid high deviations that can occur when translating low exposure values into standard test conditions.
According to the Dutch-Hungarian team, the test results showed that the PV module yield decreased by 34.6% to 41.4% and the average annual loss was 3.19%. The drop in short circuit current (Isc) was between 7.1% and 16.4%, while the open circuit voltage (Voc) dropped between 11.4% and 17.1%. “The drop in the fill factor (FF) was between 11.3% and 24.2%,” he said. “On average, the decrease in FF was the most significant, followed by the Voc and the Isc as the least decrease.”
The most common defects identified by the researchers were EVA tan, cell tie tape tan, and corrosion of solder bonds.
The results of the research were presented in the study Analysis of the long-term performance and reliability of PV modules under tropical climates in Sub-Saharan Africa, published in Renewable Energy.
In March, researchers from Ghana’s Kwame Nkrumah University of Science and Technology in Kumasi and UK’s Teesside University identified parameters and techniques that they believe could be used to design and manufacture robust, moisture-resistant PV modules for the tropics.
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