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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]

Graphical abstract Highlights: • A mathematical model for nanofluid and nano-PCM PVT is presented. • Discretization of parameters and equation was made. • An experiment has been conducted to validate the simulation results. • The nano-PCM PVT's glass and solar cell maximum temperatures recorded were 41.2°, 39.92 °C, respectively. • The nano-PCM and nanofluid maximum temperature achieved were 38.8° and 36.5 °C, respectively. Abstract The photovoltaic/thermal (PVT) system is developed to combine the two separate systems to reduce the located area and cost, improve the efficiency and save lots of materials. However, different PVT designs and configurations had been proposed with air, water, nanofluid, phase change materials (PCM) and mix of these cooling methods. In this paper, a mathematical model was proposed for the new nanofluid/nano-PCM PVT system. Experiments had been conducted to validate the mathematical model results. The comparison confirmed the ability of the proposed mathematical model to satisfactory simulate and match the experimental results. The experimental and mathematical model results show that electrical and thermal efficiencies are 13.7%, 13.2% and 72%, 71.3% respectively. However, it is found that the maximum temperature registered in glass, PV cell, wax, and nanofluid are 41.2, 39.92, 38.8 and 36.5, respectively. The proposed mathematical model accuracy compared and validated with experiment results and shows a good consistent and agreement. [ABSTRACT FROM AUTHOR]

The reduction in efficiency of photovoltaic (PV) units due to increases in cell temperature occurs when a small part of the absorbed solar radiation is converted into electricity and the remaining part is lost as heat. Recently, the addition of a range of nanomaterials with high thermal conductivity to the cooling fluid in PV/T systems has been the subject of much research. In this study, three nanomaterials were added to water as a base fluid with several volume fractions to determine the best concentration and nanoparticle for this application. The PV/T system was setup in an indoor laboratory. Knowing which material has a better effect on the PV unit in particular, and the PV/T unit in general, is important for deciding which nanomaterial is more suitable for the system. The results reveal that nanofluid gives higher thermal conductivity with very little increase in the fluid density and viscosity compared with the base fluid. The studied volume fractions were 0.5, 1, 2, 3, and 4% and the selected nanoparticles were Al 2 O 3 , CuO, and SiC. It was found that silicon carbide nanoparticles have the best stability and the highest thermal conductivity compared to the other two nano-substances. Copper oxide nanofluid has higher thermal conductivity than aluminium oxide but lower stability, although it was found here that this material reliably stable compared to in other studies. The nanofluid reduced the indoor PV/T system temperature and enhanced its generated power. [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]

The term Dust is called for any substance that spreads in the air which includes soil and dust particles (suspended dust), smoke, fog and particulate matters. It is formed from organic and inorganic substances of terrestrial origin. Such substances are like sand storms, factory smoke, bacteria, pollen, Forrest fires and volcanoes vapors. Also, they include solid atmospheric particles that stay suspended in the air for long periods, and that are able to move with wind movements for long distances. It represents large differences in volume, shape, distribution and concentrations. Dust-storms are an environmental phenomenon that transcends boundaries and their growing intensity and frequency-as a result of increasing desertification and decreasing vegetation coverage-has a tremendous negative impact on national and regional human and socio-economic development. In this study, a review of Iraqi geographical and meteorically characteristics will be made. In addition, a review of the human activities that increased desertification in Iraq areas that reflects on increasing sand and dust storms in the country will also be reviewed. The focus on dust causes, types and specifications was a priority in order to analyze its effects on PV systems. PV systems performance is affected by dust and dust storms highly influence the energy collected. A comprehensive review for the effect of dust on PV in Iraq is represented to researchers; designers and engineers dealing with PV systems in Iraq. [ABSTRACT FROM AUTHOR]

The increase in the PV cell temperature ultimately causes a reduction in its effectiveness. One of the new methods used to retain that efficiency is to establish a hybrid photovoltaic thermal PV/T system. In this study, PCM has been employed with a cooling nanofluid circulation system in order to the control heat capacitance of the system to maintain electrical efficiency on the one hand, and to raise the overall efficiency on the other. Nano-SiC particles were used in paraffin-PCM and nanofluid to establish higher thermal conductivities and therefore higher efficiency. The design is tested outdoors in Selangor, Malaysia. The tests were conducted using a fluid flow rate of 0.17 kg/s. The proposed system reduced the cell temperature (30 °C) at the peak solar radiation period (12:30 AM to 1:30 PM), which was reflected positively on the PV/T system performance. The proposed PV/T-nano PCM-nanofluid system increased the open circuit voltage from 11–13 V to 20–21 V, the power from 61.1 W to 120.7 W, and the electrical efficiency from 7.1% to 13.7%. Besides, the system made use of the thermal energy gained as its thermal efficiency reached 72%. These results ensure the adequate use of the new design. [ABSTRACT FROM AUTHOR]

The thermophysical properties of nanofluid composed of water and SiC nanoparticles without the use of a surfactant as a coolant for a PV/T system was investigated. It was observed that the addition of 3 wt% of these nanoparticles to water caused an increase in the resulting fluid density by up to 0.0082% and an increase of viscosity by up to 1.8%. Moreover, the thermal conductivity was enhanced by up to 8.2% for the tested temperature range of 25 °C–60 °C. The stability of the nanofluid was examined at intervals of three months and it was found that after six months the thermal conductivity reduced by up to 0.003 W/m K, indicating that the solution was stable and suitable for use for long periods. The use of 3 wt% SiC nanofluid increased the electrical efficiency by up to 24.1% compared to the PV system alone, while the thermal efficiency increased by up to 100.19% compared to the use of water for cooling. The final results indicated that the total effectiveness of the PV/T nanofluid system had a higher overall efficiency of about 88.9% compared to the separate PV system. [ABSTRACT FROM AUTHOR]

In the last four decades, greater attention has been paid to PV/T systems due to their advantages compared with PV or solar thermal systems alone. This paper aims to study various aspects of PV/T systems through the existing literature in order to highlight key points as future work in this field as well as illustrate different techniques used for such systems. In addition, PV/T systems are reviewed in terms of thermal and electrical side views. Furthermore, the analysis of solar thermal systems, various system applications such as air, water, air/water, phase change material PCM and Nanofluid systems are summarized. In light of most attempts to improve the PV/T system, more focus has been paid to the thermal rather than the electrical side. Furthermore, comparisons between PV/T systems in terms of performance parameters and efficiencies are presented. A critical review of many findings of previously conducted research is also discussed. It is found that the PV/T air heater system is promising for future preheating air applications. Moreover, it is suggested that the use of nanoparticles and water as base fluid improves the overall system efficiency. Furthermore, the PV side views require more attention in technical and cost terms. However, more research is essential to reduce the cost and, improve the effectiveness and technical design of such systems. [ABSTRACT FROM AUTHOR]