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• Dust and pollutants accumulated in the PVT system were investigated. • The dust accumulation and cleaning effects on PVT system performance were evaluated. • Comparisons with PV modules and thermal collectors are presented. • After 30 days of exposure to outdoor conditions, the percentage of energy generated per day was 61.17 %, 46.96 %, and 42.73 % for clean, polluted, and conventional systems, respectively. • After 60 days of exposure to outdoor conditions, the average daily energy generated was 60 %, 38.18 %, and 33.9 % for clean, polluted, and conventional systems, respectively. Dust causes losses in power generated by the PV modules as well as causes an increase in their temperatures. In this study, the photovoltaic/thermal (PVT) module dust heating effect was investigated using a spiral coil using for two PVT water cooling systems. One of the two systems was cleaned periodically (every-two weeks) and the second was left polluted with dust. The practical tests were conducted in Sohar – Oman outdoor conditions for two months (July and August 2021). The two systems performance was compared with a PV module left without cleaning. The dust accumulated on the studied systems caused a decrease in their average productivity. After 30 days, the clean PVT, polluted PVT, and conventional PV systems; yield was 61.17 %, 46.96 %, and 42.73 %, respectively. After 60 days, the average daily energy generated was 60.00 %, 38.18 %, and 33.90 % for clean, polluted, and conventional systems, respectively. Increasing the exposure period to external conditions caused an increase in the accumulated dust rate, resulting in a deterioration in the power output of both polluting PVT and conventional PV. In the periodic cleanliness of the PVT system, most of its performance was restored and its losses were limited. After 4 and 8 weeks, the yield losses for the conventional PV system were (9 % and 20 %), (2.5 %, 3.3 %) for the clean PVT system, and for the polluted PVT system they were (7.5 %, 17.7 %). [ABSTRACT FROM AUTHOR]

• Evaluation of ageing and performance of grid-connected PV. • A seven years measured data used to evaluate the PV performance. • Power losses, degradation of energy, yield, and efficiencies was calculated. • Ageing impact compared with studies in literature. In this study, the aging measurements of a 1.4 kW grid-connected photovoltaic system were analyzed. The system is located at the Solar Energy Laboratory at the College of Engineering, Sohar University, Sohar, Oman. The system variables were monitored and measured for a period of seven years, starting from 1 October 2012 until 30 September 2019, during which the electricity produced to the network was fed. Weather data metrics measurements showed solar irradiation values, ambient temperature, and the PV module temperature were measured for seven years. The performance criteria for the different PV system, which included (the PV module and system efficiency), performance ratio, and capacity factor were measured in addition to the different losses and system productivity. The results showed that the system is exposed to aging, although the amount of its impact is relatively small, as the study was conducted for a seven-year-old, while the effect of aging is more at longer ages. The measured aging caused the system efficiency to decrease by 6.3% and the production rate to 5.88% while the mean daily array capture loss and system loss were 6.95% and 6.13%, respectively, and the capacity factor decreased by 4.91%. Measurements during the seven years showed that the rate of degradation is greater during the summer than the rest of the seasons due to the high radiation intensity which causes high temperatures of the PV units in addition to the high dust density during this season. The results showed that the use of GCPV systems in the Sohar region is very successful in terms of the limited aging of the system and its long-term viability with appropriate efficiency. [ABSTRACT FROM AUTHOR]

Dust depositions on photovoltaic (PV) modules reduce the transmittance of PV glazing, resulting in the degradation of efficiency. The primary source of dust is wind-blown sand and soil particles from the ground. The coarse dust particles have a diameter larger than 2 μm. Photochemical reactions of gaseous pollutants in the atmosphere and dried droplets of seawater forming salt particles form most of the fine particles smaller than 2 μm in diameter. The physical properties of dust, such as specific gravity, particle shape, surface properties, moisture content, plastic and liquid limits, and particular grain size, vary from location to another all over the world. These differences are due to the topographic, geological, and environmental conditions of each region. The weight and shape of dust particles have a significant effect on their deposition behaviour and PV performance. In this paper, an investigation of energy losses caused by dust deposition on PV modules in Oman is presented. Six dust samples collected over three months from six locations in Northern Oman were investigated to evaluate their physical properties. Most of the dust particles (64%) diameters size ranged from 2 to 63 μm. The dust deposition on PV modules was found to vary from one location to another. The results indicated that there is no significant energy-yield loss caused by the low surface mass concentration of dust (<1 g/m 2 ) on the PV module. The maximum daily efficiency loss was measured and compared with that from the literature, revealing that the efficiency loss was 0.05%, which is small compared to those of neighbouring countries. However, the results show a decline in the productivity of the PV module up to 35–40% after exposure to the weather conditions for more than three months, indicating that the advisable cleaning period, is every three months. Therefore, establishing PV systems at these sites is a reasonable option. [ABSTRACT FROM AUTHOR]

Dust accumulation on photovoltaic modules (PVs) affects performance and reduces productivity. Many parameters specify the dust effect, and the degradation is different for PV technologies. In this study, four PV modules each with a 100 W rating were installed and tested horizontally in Sohar, Oman, for an entire year. Two monocrystalline (m-Si) and two polycrystalline (p-Si), one dusty and one kept clean. The measured power, voltage, and current show the degradation where the m-Si shows more reduction compared with p-Si. According to microscopic and XRD analysis, the dust particles have a size of 25–61 µm, and the main elements are SiO2 (55.7%) and CaO (30.0%). For m-Si and p-Si, power reductions were 19% and 14%, respectively. M-Si is more affected by dust than p-Si based on its I-V characteristics. After 55 days of dust accumulation, m-Si power degradation was found to be 40%. Furthermore, the highest power degradation was found in August. The m-Si efficiency, PV performance, capacity, and yield factors are 9.24–10.76%, 52.76–72.81%, 19.53, and 140.87 Wh/Wp, respectively. The results conclude that despite the dust accumulation still, the m-Si PV module shows promising behavior and characteristics in Oman. [ABSTRACT FROM AUTHOR]