Performance characterization of polycrystalline silicon photovoltaic modules installed in Kumasi, Ghana

The focus of this study is on the assessment of the performance of 14 polycrystalline silicon PV modules installed in Kumasi, Ghana after 22 years of field exposure. Visual inspection was carried out to ascertain any observable defects. Current-Voltage performance data was taken using a non-invasive characterization technique able to predict performance at standard test conditions (using TRI-KA and TRI-SEN) followed by Infrared (IR) Imaging tests. The results of the I-V tests showed average Pmax degradation rate of 1.38%/yr for all 14 modules. This is higher than the acceptable limit of (0.7–1.0%/year). In terms of the individual modules, M1 recorded the worst Pmax rate of degradation of 1.74%/yr, and the lowest values for efficiency and fill factor. This is consistent with the IR images and temperature difference that were recorded in the IR tests. A higher temperature difference of 25°C was recorded indicating the presence of a hot spot and a defective cell which was confirmed by the hue white colour observed in the IR test. Power Performance Factor (PPF) range of 61.8–76.5% was recorded which is below the limit of 80% often quoted in warranty statements. The drops in PPF indicate that the modules have degraded.

Advantages of InGaN–GaN–InGaN Delta Barriers for InGaN-Based Laser Diodes

An InGaN laser diode with InGaN–GaN–InGaN delta barriers was designed and investigated numerically. The laser power–current–voltage performance curves, carrier concentrations, current distributions, energy band structures, and non-radiative and stimulated recombination rates in the quantum wells were characterized. The simulations indicate that an InGaN laser diode with InGaN–GaN–InGaN delta barriers has a lower turn-on current, a higher laser power, and a higher slope efficiency than those with InGaN or conventional GaN barriers. These improvements originate from modified energy bands of the laser diodes with InGaN–GaN–InGaN delta barriers, which can suppress electron leakage out of, and enhance hole injection into, the active region.