Search

Worldwide, drinking water shortages are a major concern. In many parts of the world, fresh water sources are deteriorated and polluted by human activities and population growth. Using fossil fuels to distill water for human consumption requires a large amount of energy. It was suggested that solar energy could be used to distill polluted or salty water without harming the environment. The sun is a free and abundant energy source, especially in swampy and remote regions. However, the design and operation of solar stills limit their efficiency and productivity. Solar freshwater production systems are discussed in this review in terms of the latest developments in production and distillation efficiency. Based on various performance criteria, the study analyzes direct solar desalination processes. Detailed discussions of recent modifications and innovations are also included and highlighted in this paper. It is the goal of all the studies reviewed to achieve maximum productivity and efficiency, low capital costs, and ease of installation. Among the developments reviewed are phase change materials (PCMs), nanoparticles, and solar reflectors with high efficiency. In addition to features of solar stills, current modifications have been evaluated in terms of location, water temperature, solar radiation intensity, production level, inclination angle, productivity, and efficiency. Solar still performance parameters were also studied in relation to modifying the absorption area and using reflectors and condensers. Several improvements were made which resulted in high productivity rates. The distiller’s productivity increases from 10% to 180% when a phase change material is added. When a nanomaterial is added to paraffin in the still, productivity increases by 25% to 320%. Furthermore, Wicks increase the still’s yield by 20%-300%, depending on design. A few recommendations are made regarding future work in solar desalination based on this review at the end of the study. [ABSTRACT FROM AUTHOR]

Airborne dust and dust storms are natural disasters that transport dust over long distances from the source basin, sometimes reaching hundreds of kilometers. Today, Iraq is a basin that produces dust storms that strike all neighboring countries such as Iran, Kuwait and Saudi Arabia. These storms affect the productivity and capacity of the photovoltaic modules and reduce the amount of electricity that is generated clearly. Airborne dust reduces the intensity of solar radiation by scattering and absorbing it. In addition, the dust accumulated on the photovoltaic modules causes a deterioration in their productivity. In this study, an extensive review of wind movement and its sources, especially those that hit the city of Baghdad, the capital of Iraq, was conducted. Practical experiments were also carried out during a storm to measure important variables that had not been measured practically before at this site. The experimental tests were carried out starting from 1 April 2022 and continued until 12 April. Within this period, a dust storm occurred that lasted for three consecutive days that was considered one of the most severe storms that the city of Baghdad had experienced in the last few years. Practical measurements showed a deterioration in the solar radiation intensity by up to 54.5% compared to previous days. The air temperature during the storm decreased by 21.09% compared to the days before the storm. From the measurements of ultrafine aerosol particles PM1 and PM2.5, there was a significant increase of 569.9% and 441% compared to the days before the storm, respectively. Additionally, the measurements showed an increase of 217.22% and 319.21% in PM10 and total suspended particles, respectively. Indoor performance experiments showed a deterioration of current, voltage, power and electrical efficiency by 32.28%, 14.45%, 38.52% and 65.58%, respectively, due to dust accumulated during the storm days compared to the previous days. In the outdoor experiments, the rates of deterioration of current, voltage, power and electrical efficiency were greater, reaching 60.24%, 30.7%, 62.3% and 82.93%, respectively, during the storm days compared to the days before it. During a storm, cleaning the panels is futile due to the high concentration of dust in the air, especially by water. However, the photovoltaic modules can be dry cleaned with bristle brushes after the storm has subsided. [ABSTRACT FROM AUTHOR]

• 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]

Iraq is characterized by hot and sunny weather with high radiation intensity. These conditions are suitable to produce photovoltaic electricity, on the one hand, but on the other hand are not suitable for photovoltaic modules whose efficiency decreases with increasing temperature. In this study, a photovoltaic module was practically cooled by two PV/T systems, one cooled by water and the other by nanofluid and nano-paraffin. Iraqi-produced paraffin was used in this study for its cheap price, and because its melting and freezing temperature (46 °C) is close to the operating range of photovoltaic modules. Nano-TiO2 was adopted as an additive to water and paraffin. The study results showed an obvious enhancement of the thermal conductivity of both water and paraffin, by up to 126.6% and 170%, respectively, after adding a 2% mass fraction of nano-TiO2. The practical experiments were carried out outdoors in the city of Baghdad, Iraq. A fluid mass flow rate of 0.15 kg/s was selected for practical reasons, since at this rate the system operates without vibration. The PV panel's temperature, in the PV/T system (nano-fluid and nano-paraffin), decreased by an average of 19 °C when the tested systems operated during the peak period (12 PM to 3 PM). The decrease in temperatures of the PV module caused a clear improvement in its electrical efficiency, as it was 106.5% and 57.7% higher than the PV module (standalone) and water-cooled PV system, respectively. The thermal efficiency of this system was 43.7% higher than the case of the water-cooled PV/T system. The proposed system (nano-fluid and nano-paraffin) provides a greater possibility of controlling the heat capacity and increasing both efficiencies (electrical and thermal), when compared to a standalone PV module, in harsh Iraqi weather. [ABSTRACT FROM AUTHOR]

Summary: Photovoltaic thermal (PV/T) systems combine a hybrid photovoltaic (PV) module and a flat‐plate solar thermal collector. The hybrid design allows for simultaneou increase in thermal energy while providing cooling for the PV module. In doing so, the PV module temperature drops, and therefore the electrical efficiency increases. Another benefit of PV/T collectors is that they allow for the usage of thermal, and PV module in the same area and so that saved space for the consumer. This study presents a numerical (CFD) design and experimental evaluation of a PV/T system cooled by nano‐PCM and nanofluid. The selected nanomaterial and PCM were nano‐silicon carbide (SiC) and paraffin, respectively. Nano‐silicon carbide particles were employed with the paraffin to ameliorate its thermal conductivity. The study examined various aspects of the system such as the SiC particles' optimal mass fraction suspended in both water (base fluid) and paraffin, the optimum mass flow rate of nanofluid, voltage and current of the PV module, thermal energy of solar thermal collector, and the combined PV/T efficiency. The numerical and practical results were very close, which proves the validity of the hypotheses used in building the program. The significance of this study is demonstrated by the result as this design led to maximum thermal and electrical efficiencies of 72% and 13.7%, respectively. The proposed PV/T system introduced better stability of the generated power and thermal efficiency at peak time than the other two studied systems. [ABSTRACT FROM AUTHOR]

Both electrical and thermal efficiencies combine in determining and evaluating the performance of a PV/T collector. In this study, two PV/T systems consisting of poly and monocrystalline PV panels were used, which are connected from the bottom by a heat exchanger consisting of a spiral tube through which a nanofluid circulates. In this study, a base fluid, water, and ethylene glycol were used, and iron oxide nanoparticles (nano-Fe2O3) were used as an additive. The mixing was carried out according to the highest specifications adopted by the researchers, and the thermophysical properties of the fluid were carefully examined. The prepared nanofluid properties showed a limited effect of the nanoparticles on the density and viscosity of the resulting fluid. As for the thermal conductivity, it increased by increasing the mass fraction added to reach 140% for the case of adding 2% of nano-Fe2O3. The results of the zeta voltage test showed that the supplied suspensions had high stability. When a mass fraction of 0.5% nano-Fe2O3 was added the zeta potential was 68 mV, while for the case of 2%, it reached 49 mV. Performance tests showed a significant increase in the efficiencies with increased mass flow rate. It was found when analyzing the performance of the two systems for nanofluid flow rates from 0.08 to 0.17 kg/s that there are slight differences between the monocrystalline, and polycrystalline systems operating in the spiral type of exchanger. As for the case of using monocrystalline PV the electrical, thermal, and total PV/T efficiencies with 2% added Fe2O3 ranged between 10% to 13.3%, 43–59%, and 59 to 72%, respectively, compared to a standalone PV system. In the case of using polycrystalline PV, the electrical, thermal, and total PV/T efficiencies ranged from 11% to 13.75%, 40.3% to 63%, and 55.5% to 77.65%, respectively, compared to the standalone PV system. It was found that the PV/T electrical exergy was between 45, and 64 W with thermal exergy ranged from 40 to 166 W, and total exergy from 85 to 280 W, in the case of using a monocrystalline panel. In the case of using polycrystalline, the PV/T electrical, thermal, and total exergy were between 45 and 66 W, 42–172 W, and 85–238 W, respectively. The results showed that both types of PV panels can be used in the harsh weather conditions of the city of Baghdad with acceptable, and efficient productivity. [ABSTRACT FROM AUTHOR]

• Evaluation of dust impact and cleaning methods on photovoltaic performance. • Indoor experimental investigation of monocrystalline and polycrystalline has been conducted. • The effect of different dust types has been studied and collected samples from different locations were tested. • Power losses and degradation of yield were calculated for different cases. Photovoltaic modules are affected by the weather and are sensitive to dust accumulation. The accumulation of dust causes obvious losses in the produced yield. To reduce these losses to a minimum, it is recommended to clean the photovoltaic units periodically by several cleaning methods. In this practical study, the accumulated dust was collected for a period of two months (March and April/2021) from five sites in the Wilayat of North Al Batinah – Oman. The dust components were examined, and the sources of these components were determined and their proportions in the dust of each city. The study adopted the examination of the effect of each component separately on the performance of monocrystalline and polycrystalline PV modules. The results showed that the contamination of 5 g/m2 on the monocrystalline PV module caused a decrease in the produced power by 12%, 6%, 6%, 7%, 3%, 4%, and 4%, for ash, calcium carbonate, limestone, cement, sulfur, sawdust, and brown soil, respectively. For polycrystalline module, at the same contamination (5 g/m2), the measured deteriorations were 5%, 4%, 4%, 1%, 2%, and 2% for ash, sand, limestone. sawdust, black silicon carbide and silica gel, respectively. The best manual cleaning methods were also studied to choose the optimal ones for each PV module and city. Polycrystalline are more affected than monocrystalline by the accumulated dust, with an average of not less than 10% at an accumulation rate of 50 g/m2 and 5.28% at an accumulation rate of 5 g/m2. The best way to clean PV modules to recover the largest percentage of yield losses is the sodium solution with rubber and cloth brushes. The study suggests, depending on the practical results, periodic cleaning periods from 10 days (for polycrystalline module in the cities of Liwa, Sohar and Barka) to 15 days (for monocrystalline module for all the cities studied). [ABSTRACT FROM AUTHOR]

Solar energy and photovoltaic (PV) systems became an essential part of the global energy profile. The PV systems are designed using different configurations such as standalone, grid-connected, and tracking. However, PV systems could be added to other renewable energy systems or nonrenewable energy systems such as wind turbines and diesel generators, respectively. In this context, designers, researchers, and engineers working to find the optimum design fitting the electrical load in terms of technical, economic, environmental, and social aspects. Many software, models, and algorithms were invented and proposed to help to find the optimum PV sizing and design. In this paper, a comprehensive review was conducted to describe, evaluate, and compare most of the software (36 software were considered), models, and algorithms used to design PV systems in the past eight decades. It is found that PV system design optimization tools developed with time and needs. Different classifications are used for design software, sometimes as classical and artificial or single and hybrid algorithms. However, hybrid algorithms became the most used algorithm due to their flexibility and ability to deal with complex problems. Also, comparison and critical review are presented, and a case study is given in this paper. It is found that REPS.OM software results are closer to the case study experimental results compared with HOMER software with less than 7% variation between the two software. The review presented in this paper provides useful information to identify PV system design software suitable for the user application. [ABSTRACT FROM AUTHOR]

The purpose of this paper is to review findings on the integration of solar thermal collectors, photovoltaic thermal collectors, and heat pumps to provide both electrical and thermal energy. The energy consumption of HP systems in buildings is significant. Studies have verified the benefits of using PVT collectors in heat pumps to provide electricity and solar assistance to their cold sources. This article provides an overview of advances and progress in solar assisted heat pumps (HPs). Increasingly, heat pumps are integrated with thermal and photovoltaic solar collectors. Providing both heat and hot water as well as electricity, this integration can be applied to a variety of applications. The services range from providing power and heating to industrial and agricultural needs. The aim of this review is to examine research conducted over the past twenty years with an emphasis on studies that have significant implications for the evolution of the technology in the near future. In demanding environmental conditions, the coupling of Photovoltaic/Thermal collectors (PVT) with HP systems has demonstrated a noticeable improvement in system performance and operational reliability. By addressing critical challenges and unresolved issues, the subsequent discussions and recommendations serve to channel attention. This will lead to enhanced performance improvements in HP systems by directing efforts in this way. [ABSTRACT FROM AUTHOR]

Nanofluids are widely used today as an excellent heat carrier in various solar energy applications. In the current study, the possibility of using a nanofluid consisting of copper oxide (CuO) nanoparticles added to a blend of water and ethylene glycol (EG) at 75% to 25%, respectively, were investigated. Nano-CuO was added in four mass fractions (0.1, 0.5, 1.0, and 2.0%) using ultrasonic vibration to make sure that a stable emulsion was obtained. The thermophysical properties of the samples prepared in the laboratory were examined, as well as the stability of these samples. The prepared emulsions thermal conductivity continued to rise as the nano-CuO mass fraction added was increased in the base fluid. The increment rate was close to 140% compared to the base fluid. The effect of nanoparticle addition to base fluid on the resulted density was limited to 0.072% (2% of Nano-CuO added). Also, the increase in the viscosity of the nanofluids did not exceed 2.3% when adding 2.0% of the nanoparticles. The results of the stability test of the prepared fluids showed that they have high stability, and the stability of emulsions increases with a decrease in the percentage of adding bulk nanoparticles. A nanofluid with an added mass fraction of 2.0% was examined in a PV/T system installed on the roof of the Solar Energy Laboratory at Sohar University – Oman. The electrical and thermal efficiencies were enhanced by 6.76% and 39.6% respectively when the prepared nanofluid (2.0% nano-CuO) was used due to its better cooling effect compared to the use of the base fluid only. The study presents one of the appropriate solutions to treat the high temperatures of PV modules in Oman and the deterioration of their electrical efficiency. [ABSTRACT FROM AUTHOR]

• The study focuses on examining different PCMs to be used in PVT systems. • Hybrid PCMs were produced from mixing Vaseline and paraffin. • Vaseline mixes with paraffin and reduces its melting point. • Lower melting point of the PCM corresponds to an increase in the heat flow rate. • Best cooling results were obtained when using the hybrid PCM. The use of phase change materials (PCMs) in photovoltaic-thermal systems (PVT) is essential for developing PV systems and raising their productivity. PCM is distinguished by its many variations and properties, the most important of which is the melting point. In this study, the driven question and focus was on investigating which is better for use in a PVT, PCM systems with a high or low melting point? Two types of PCM were used in the study: paraffin wax (melting point 45 °C), Vaseline -petroleum jelly (melting point of 25 °C), and hybrid PCM (mixtures of the two PCMs in proportions of 25%, 50% and 75%). The study was conducted indoors by simulating the harshest condition in Iraq's weather in summer. The results showed that the wax and the Vaseline mixed entirely with an apparent decrease in the product's melting point. In contrast, the rest of the thermophysical properties of the product were relatively affected. The use of paraffin, petroleum jelly and 50% paraffin + 50% Vaseline in the PVT system caused a decrease in the surface temperatures of the photovoltaic cell, which resulted in a more significant improvement in the performance of the system. The maximum electrical efficiency reached was 13.7%, while the maximum thermal efficiency was 39.0%. Reducing paraffin melting point leads to better performance of PVT systems, as the hybrid paraffin (50% wax + 50% Vaseline) have better productivity than pure paraffin wax due to its lower melting point. [ABSTRACT FROM AUTHOR]

Summary: The temperature of photovoltaic cell is reduced by heat transfer fluids (HTF) in cooling channels, which are attached to the back of the photovoltaic module in a hybrid thermal photovoltaic system (PV/T). Recently, nanofluids have been implemented as HTF's in PV/T systems. Various types of nanofluids have been synthesized, prepared, and tested, however, not a specific type in particular. In this paper, experiments were carried out using Single‐walled carbon nanotubes (SWCNTs) nanofluids. The proposed nanofluid consisted of a primary fluid that is water with a volume ratio of 75.0% and glycol Ethylene with a volume ratio of 25% and a surfactant, Cetyltrimethylammonium Bromide(CTAB), in an amount of 0.5 mL. Single‐walled carbon nanotubes (SWCNTs) were added in four weight ratios of 0.1%, 0.5%, 1.0%, and 2.0%. The samples were examined and compared based on their thermophysical properties, and from these properties, a volume fraction of 0.5% SWCNT was chosen to form the nanofluid. In this study, the performance characteristics of the PV/T were investigated. The results of the study showed that the proposed nanofluid caused an increase in the electrical power generated by 11.7% while the electrical efficiency of PV/T was increased up to 25.2% compared to the PV system. It is found that the cell temperature reduced by 18% on average for a whole day operation. The studied PV/T system produced an impressive overall efficiency of 71% compared to the PV system, which generated no more than 11%. SWCNTs have shown superior results in improving the performance of the studied PV/T system compared to other types of nanofluids used in PV/T systems in the literature. [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]

• A new model of dust impact on grid-connected PV was proposed. • The dust characterization and effects in Sohar, Oman was investigated. • Experimental validation of the proposed model with the techno-economical evaluation presented. A grid-connected photovoltaic system was tested and investigated for the entire year under desertic weather exhibited. The system contains 1.4 kW PV and 1.7 kW inverter —the data was measured every second and used to model and evaluate the system performance. However, dust is one of the essential parameters that affect grid-connected photovoltaic performance, yield, and profitability. In this paper, a proposed model has been takes into consideration the dust impact on grid-connected photovoltaic performance in a novel way. The outcomes demonstrate that the proposed model precisely anticipated the system performance and validated through experimental results. However, it is found that the photovoltaic, inverter, and performance efficiencies are 10.80%, 94.00%, and 73.00%, respectively. Besides, the average yield factor is 141.39 kWh/kWp, and capacity factor is 19.64%. It concluded that the system productivity in Oman is within the prospected rate. The information in this paper is valuable for investors, researchers, and engineers interested in grid-connected photovoltaic and dust impact in Oman and neighboring countries. [ABSTRACT FROM AUTHOR]

Photovoltaic cells are profoundly affected by the weather conditions of their erection area, and the most important of these influencing conditions is dust. This study focused on assessing the harmful effects of dust deposition on the performance of a photoelectric module operating in the weather conditions of the city of Baghdad-Iraq. The accumulated dust was collected for two months, and its components were studied. Also, the effect of the main three elements on the PV module performance was examined separately, and it was compared to naturally accumulated dust. Ascending blocks of; particulate particles (PM), calcium carbonate (CaCO3), and soil were used and the effect of each of them was evaluated on the PV module performance. The accumulation of dust causes a significant decrease in the performance of the PV module. The components of accumulated dust also play an essential role in determining the rate of reduction in the generated energy. Dust deposition increases the surface temperature of the photoelectric, which in turn increases the loss of generated energy. The study examined several types of locally available PV cleaning materials to evaluate the best ones. Cleaning the PV module by sodium solution reduced the generated energy loss when the module is contaminated with natural dust and PM, but its effect is limited on soil and CaCO3. For CaCO3 and soil, high-pressure water should be used, wiping the surface of the PV with a cloth or brush to prevent these substances from sticking to the surface of the PV. [ABSTRACT FROM AUTHOR]

The interest in water-diesel emulsion fuel (EM) is increased recently because of the significant reduction in emissions from diesel exhaust, especially NOx and PM. In this study, a diesel engine configured for experimental investigations was fueled by ultra-low sulfur diesel (ULSD) and a diesel-water emulsion (EM). Both fuels' combustion characteristics were studied at a speed of 1500 rpm and using a load of 2.5 and 5 bars and variable injection timings. Regular and irregular pollutants were studied at the same conditions as well as at variable engine loads and speeds to better understanding for their formation conditions. As for the first time (in the case of an engine running with a water-diesel emulsion) irregular pollutants for EM emulsion were measured. The measured results indicated that the use of water-diesel emulsion reduced the heat released in the combustion chamber, which causes an increase in the brake specific fuel consumption and ignition delay. For the tested loads, the diffusion combustion duration for EM was decreased when the injection timing was retarded while the opposite was occurred for premixed combustion duration. The regulated NOx and Smoke Number were reduced when EM was used compared to ULSD while CO and HC levels were increased at low engine's speed and loads. Besides, these concentrations are depending on injection timing (they were higher at restarted timing). The unregulated emissions measured (Formaldehyde, Acetaldehyde, Methane, Acetylene, Ethylene, and propylene, Ammonia, and Acetone) were increased with using EM, especially at no and low loads, indicating the high impact of the combustion chamber temperature on these pollutants formation. • The effects of W/D emulsion use were compared to ULSD combustion in a diesel engine. • W/D emulsion reduced the combustion chamber's heat released causing high BSFC. • When W/D emulsion used, NOx and Smoke Number reduced at medium and high speeds. • When W/D emulsion was used, CO and HC levels were increased at low engine's loads. • Using W/D emulsion increased the unregulated emissions at no and low loads. [ABSTRACT FROM AUTHOR]

• Dust and pollutants accumulated on PV in six cities located north of Oman was investigated. • The chemical components of accumulated dust were studied and analysed. • The influence of wind velocity and relative humidity on the collected dust type on the PV cells was examined. • Sodium solutions more effective for PV cells cleaning near industrial area due to high percentage of PM. • Dust physical properties dependent on environmental conditions and geographical area. The Sultanate of Oman, similar to other GCC countries, is affected by the fluctuation of oil prices, which led the decision-makers in this country to move towards renewable energy and particularly the establishment of photovoltaic (PV) solar power plants. This step requires a thorough study before spending millions of dollars to build such power plants. Since dust is one of the main problems of PV in the GCC countries, this study investigates the influence of certain weather factors such as wind speed, relative humidity on dust accumulation and the effect of the cleaning method applied to each city separately. After a full year of observation and data collection on climatic conditions and the output of the six systems installed and used in this study, it is found that the cities of Liwa and Sohar, followed by Muscat, exhibit the highest percentage of dust and contaminants. The most prominent pollutants are the particulate matters (PM) from the chimneys of the power plants, and smelters in the industrial city of Sohar. Also, the movement of a considerable number of vehicles in Muscat caused a rise in the concentration of PM deposited on PV cells. For the other three cities (Al-Khabourh, Suwaiq, and Shinas), they are far from any industrial zone, and because of reduced traffic, the percentage of accumulation of dust and pollution of PV cells was limited. Nine available methods have been used to clean the PV cells after the dust accumulated for one month. From these methods, it is found that the use of water is sufficient to wash the PV cells in the cities of Al-Khaburah, Shinas, and Al-Suwaiq, but the effect of cleaning is more reduced on Sohar, Liwa, and Muscat. Because of PM and many chemical compounds, the use of a sodium solution was the best option in cleaning the PV cells of these three cities. It was noted that the loss of solar cell productivity decreases during the rainy season, which acts as a natural cleaner for the PV. The study also found that dew in the cities studied before sunrise causes the interaction of some salts of sodium, magnesium, and calcium and builds a layer of cohesive salts, which are difficult to clean. [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]

Solar energy technology has been evolving for the better part of the last decade. Worldwide innovation and support have created an alternative energy source that is helping to battle climate change. Photovoltaic thermal (PV/T) converters use various working fluids. Silicon carbide (SiC) nanofluid is employed in this study in the cooling application of a PV/T system. The aim of this study is to assess and evaluate the performance of PV/T collectors when running a SiC nanoparticle dispersed in water as the base fluid for both indoor and outdoor systems. The performance assessment includes thermal, electrical and combined PV/T efficiencies. Indoor and outdoor experimentation is done to accurately assess the performance enhancement hypothesized by the authors. Furthermore, a comparison is made between the indoor and outdoor results to validate each experiment and draw conclusions. The indoor system results were close to the outdoor experiment, suggesting a performance enhancement with an incremental efficiency rise. [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 developments in the field of nano-additives have increased in the recent years due to the desire to reduce the level of exhaust emissions in diesel engines. The soot characteristics of particulate matter (PM) and nitrogen oxides (NOX) were experimentally investigated using two concentrations of titanium dioxide (TiO2) as nano-additives (25 ppm and 40 ppm) blended with C20D (composed of 20% castor oil methyl ester and 80% diesel fuel) and 30% exhaust gas recirculation (EGR). The combustion of C20D + TiO2 increases brake thermal efficiency (BTE) by 2.8% in comparison with neat C20D, while a significant reduction was obtained in BSFC 6.5% and NOX emissions were maintained at a level parallel with diesel. The results indicated that the technique involving a high EGR rate and the addition of 25 ppm and 40 ppm of TiO2 nanoparticles to the C20D exhibits better reductions in NOX emissions by 17.34% and 21.83%, respectively, compared to the technique comprising the use of C20D + TiO2 and C20D. The reduction in the total concentration of PM via the addition of TiO2 nanoparticles to the C20D was 26.74% greater than neat C20D and diesel. In contrast, the incorporation of a high rate of EGR with C20D +TiO2 increased the PM concentrations by 16.85% compared to the technique without EGR. Furthermore, the high concentrations of TiO2 nanoparticles (40 ppm) in the C20D produced 19 nm smaller soot nanoparticles compared to the 23 nm larger soot nanoparticles produced from the low concentrations of TiO2 nanoparticles (25 ppm) added into the C20D. The current investigation reveals that the reduction in NOX emissions and the production of soot nanoparticles notably improved due to the synergic effect of EGR, the TiO2 nanoparticles, and biodiesel. [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]

Abstract: Iraq suffers from electricity shortages, and many challenges will have to be overcome to meet future increases in electrical demands. This investigation found that solar, wind and biomass energy are not being utilized sufficiently at present, but these energies could play an important role in the future of Iraq’s renewable energy. Additionally, the potential of offshore-wind energy in the Gulf (near Basrah in the southern part of Iraq) needs to be investigated. The Iraqi government''s attempts to utilize renewable energy have been discussed. This paper aims to review and discuss the status and future of renewable energy in Iraq. The uses of renewable energy sources, such as solar, wind and biomass, have been reviewed. This paper concludes with recommendations for the utilization of these energy resources. [Copyright &y& Elsevier]

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]

Utilizing solar energy to generate electricity on large scale photovoltaic (PV) power plants became a trend as a new option adopted by many countries. The optimum installation of PV power plants depends on the geographical location, which specifies irradiation, latitude, longitude, tilt angle, orientation, etc. However, the PV panel affected by many environmental parameters, which has a significant impact on the power productivity, conversion efficiency, and cost of energy. Dust is one of the essential parameters that affect PV panel performance, yield, and profitability. However, the dust characteristics (type, size, shape, meteorology, etc.) is geographical site specified. Many researchers investigated PV panel dust cleaning and mitigation methods. This paper put into perspective the recent investigations of dust impact on PV systems and decent cleaning methods. It is found that daily PV power losses and monthly efficiency reduction due to dust in some locations is more than 1% and 80%, respectively, which is relatively high. The present paper aims to provide an appraisal of dust problem and cleaning methods status, challenges, and prospects. Also, a critical review is developed for researchers interested in this field. It is found the main dust elements which have impact are six dust pollutants. Also, the study conclude that selection of the dust cleaning method depends on many parameters in term of technical and economic aspects. Finally, this paper contains a comprehensive review of dust problem and cleaning methods for engineers, designers, and researchers dealing with PV systems. • A comprehensive review of dust problems and PV cleaning methods is discus. • A new dust cleaning methodology is proposed. • Different type of cleaning methods was discussed and compared technically and economically. [ABSTRACT FROM AUTHOR]

Solar cells convert the irradiance to electricity, but environmental conditions affect cell performance. In this study, a general model for dust accumulation effect on solar cell performance is proposed. An improvement is introduced to the solar cell one-diode model by considering dust impact to simulate solar cell performance and particularly I-V characteristics. In this study, the novelty is to propose a dust model and improve the single-diode model. The proposed model accounts for the impact of dust on the PV performance by taking into consideration the dust ingredients. Three major components of Oman dust (SiO2, CaO, and Fe2O3) in different proportions were adopted to verify the proposed model using a 4.18 W solar cell. Also, dust samples were collected from six locations in Oman and used for validation in the lab by using a 125-W conventional PV module and solar simulator. I-V characteristics and power losses were determined to compare experimental, ideal, and proposed model results. When mixing 10 g of SiO2, CaO, and Fe2O3 to form 30 g of dust on the cell, the short-circuit current is 42.86% higher in the ideal model than the measureds short-circuit current, while the short-circuit current of the proposed model was 2.79% lower than the measured values. The results obtained from the proposed model are consistently close to the results from the experimental measurements even when using different masses of dust ingredients. [ABSTRACT FROM AUTHOR]

Summary: The use of photovoltaics has spread widely, and government agencies have begun adopting plans to deploy plants with large capacities, due to their environmental friendliness, low manufacturing costs, and high productivity. In the sunny countries where this technology should spread, the photovoltaics' energy conversion efficiency decreases due to the high temperature of which the cell's operate at; because a large part of the solar radiation is absorbed by the solar panels as heat, while the smaller part converts it to electricity. From here, the benefit of the shift towards the PV/T technology that works to reduce the photovoltaic modules temperature and improve their electricity produced along with yielded thermal energy which can be utilized in other applications. In this study, a thorough review of many recent research and studies published in the field of PV/T has been carried out. The present study was divided into several sections to clarify and focus on the effect of each technology separately. Researchers used one or more fluids to cool the solar panels, and their research dealt with many of these fluids, starting with air, water, oil, etc. Other researchers have tended to increase the thermal conductivity of liquid cooling fluids by adding many types of nanoparticles with high thermal conductivity. Other researchers have used variable‐phase materials to take advantage of the large storage of the latent heat of these materials. Other researchers have studied improving heat transfer of PCMs by mixing it with nanomaterials with high thermal conductivity. Others have also combined nano‐PCMs and nanofluids together in one system, and they have demonstrated, in theory and practice, that this technique exhibits higher energy collection and utilization than the other types of PV/T. At the conclusion of the study, some critical points are identified that work is still limited and needs more research efforts and studies. [ABSTRACT FROM AUTHOR]

• Increase of mass flow rate from 10 to 40 kg/h led to increase in useful heat gain. • Using spiral flow collector enhances electrical efficiency of PV modules. • PV/T with spiral flow channel outperforms PV/T's with direct and web flow channels. • Electrical efficiency of PV/T systems outperform conventional PV module. The electrical efficiency of photovoltaic modules reduces with increase in cell temperature. However, using photovoltaic/thermal systems to enhance thermal, electrical, and overall outcomes is an excellent option. In this study, three water cooling PVT systems that have variable flow channels (web type, direct type, spiral type) installed, tested, evaluated, and compared with conventional PV in terms of electrical performance. The systems were tested outdoor in Sohar, Oman. The water mass flow rate was tested at 40 kg/h. The proposed systems reduced cell temperature on average by a minimum of 3 °C. The temperature reduction improves the voltage, power, and efficiency significantly. The highest average maximum voltage, current and power were observed for the spiral flow PVT system, which are 17.7 V, 2.89 A and 51.3 W, respectively. The overall efficiency for the conventional PV, web, direct and spiral type PVT systems were around 7.8%, 18.5%, 28.0% and 35.0%, respectively. The spiral flow collector found to produce the best efficiency compared to web and direct flow collectors. The results confirm that the use of the proposed PVT design is very suitable for the Sultanate of Oman and neighboring countries with similar environmental conditions. [ABSTRACT FROM AUTHOR]

Summary: Hybrid photovoltaic thermal system is an effective method to convert solar energy into electrical and thermal energy. However, its effectiveness is widely affected due to the high temperature of photovoltaic panel, and it can be minimized by employing nanofluids to the PV/T systems. In this research, the effect of various nanoparticles on the PV/T systems was studied experimentally. The nanofluids Al2O3, CuO, and multiwall carbon nanotube (MWCNT) were dispersed with water at different volume fractions of 0, 0.5, 1, 2.5, and 5 (vol%) using ultrasonication process. The effect of nanomaterials on viscosity and density was classified. All tests were carried out in an outdoor laboratory setup for calibrating the PV temperatures, thermal conductivity, electrical power, electrical efficiency, and overall efficiency. In addition, the energy analyses were also made to estimate the loss of heat owing to the nanofluids. Results show that use of the nanofluid increased the electric power and electrical efficiency of PV/T compared with water. Furthermore, MWCNT and CuO reduced the cell temperature by 19%. Consequently, the nanofluids MWCNT, Al2O3, and CuO produced the impressive values of 60%, 55%, and 52% increase in an average electrical efficiency than conventional PV. Particularly, the MWCNT produced superior results compared with other materials. It is evidently clear from the result that the introduction of the nanofluid increases the thermal efficiency without adding any extra energy to the system. Moreover, insertion of Al2O3, CuO, and MWCNT on PV/T system increases the exergy efficiency more than conventional PV module. [ABSTRACT FROM AUTHOR]

Summary: This article evaluates a 1.4‐kW building integrated grid‐connected photovoltaic plant. The PV plant was installed in the Faculty of Engineering solar energy lab, Sohar University, Oman, and the system data have been collected for a year from July 2017 to June 2018. The grid‐connected system was evaluated in terms of power, energy, specific yield, capacity factor, and cost of energy, and payback period. The measured diffuse and global solar irradiations are 3289 and 6182 Wh/m2, respectively. Four predictive models (TLRN, FRNN‐1, FRNN‐2, and FRNN‐3) using deep learning approach based on RNN and TLRN were proposed to predict the PV current performance through data input of temperature (T) and solar irradiance (G). The experiment results found that the highest energy production, array, reference, and final yields are 245.8 kWh, 3.43 to 5.65 kWh/kWp‐day, 4.61 to 7.33 kWh/kWp‐day, and 3.24 to 4.82 kWh/kWp‐day, respectively. Meanwhile, CF, CoE, and PBP were found to be 21.7%, 0.045 USD/kWh and 11.17 years, respectively. The highest performance for prediction models were found for FRNN‐2 and FRNN‐3 due to they exhibit lower MSE which means being tightly fitted to experiments. [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 GCC experience is the only successful Arab experience at the level of regional cooperation in the Arab region. This success can only be enshrined by the Council's ability to continue. Also, these countries succeeded in promoting a rapprochement between their States and the Arab region and its surroundings. The three wars in the area posed significant challenges to the Gulf Cooperation Council. Arabian Gulf authorities have sensed the need to develop a strategic partnership focus on the defense and the sustainability of the GCC countries, and their well-being. Climate change has sparked a war; all the wealth and luxury enjoyed by the people of the Gulf States will be affected by climate change. The impact of climate change appears in many forms, including an increase in the average ambient temperature in the region with severe decrease in precipitation. The area climate is rapidly changing because of human activities from year to year and decade to decade. The Arabian Gulf region is interested in climate change on several levels, and there is a growing awareness in the area. The potential for climate change is affecting many sectors and systems, like distilled water processing, food security, renewable energies and public health. This paper will discuss these issues in this paper. The information presented in this article aims to give a review and discussion of the effect of climate change in the GCC to the researchers; decision makers, politicians, and engineers. [ABSTRACT FROM AUTHOR]

The decline of petroleum resources is a real problem that needs to be addressed by the non-renewable energy policies applied by world governments. Renewable energies such as solar and wind sources, nuclear power, or hydrogen fuel cells may become viable alternatives to conventional fuel in the future. This study reviews the conditions of the world's leading oil producers for the coming 50 years, i.e. the Gulf Cooperation Council (GCC) countries. On the other hand, this study clarifies the share of renewable energies today and how it will continue to increase steadily. This study demonstrates that the increase in oil and shale gas production will affect the GCC countries, especially kingdom of Saudi Arabia (KSA), the largest oil exporter in the GCC. The study demonstrates that the GCC have failed in the separation between economic development and energy demand in the past decades. Therefore, the GCC economies are among the least efficient in the world. The growth in energy consumption is faster than economic growth in the region. Sustainable energy in GCC states has been considered since 2008. Resource efficiency programmes, clean technology research, alternative energy projects, green building codes, green economy strategies, and public transport systems have become a part of mainstream news. The GCC states have started to have a stake in the transition to sustainable energy. The GCC states have already undertaken some policy, projects, and sector-wide efforts. These projects, if implemented, will boost the investment, and its effect on the environment will be apparent. Many of these policies and plans, however, still exist only on paper. The green building codes and national solar targets has been discussed. [ABSTRACT FROM AUTHOR]

This is a numerical investigation of the unsteady mixed convective flow over an isothermally heated circular cylinder. The flow is directed vertically downwards with buoyancy forces in the opposite direction. A parametric analysis was conducted at five Reynolds numbers Re = 10 , 20 , 30 , 40 , 100 , and for Richardson numbers between Ri = 0 and 0.5, to evaluate the influence of thermal buoyancy on the instantaneous flow behaviour, vortex-shedding characteristics, thermal fields, and mean heat-transfer rates. The simulations show that at the highest Reynolds number investigated, Re = 100 , the normal periodic von Kármán vortex street still characterises the flow as Richardson number is increased; however, the oscillation frequency decreases and the oscillation amplitude increases. For Re ≤ 40 , a new vortex street appears, named the " Buoyancy-Opposing Vortex Street ", due to thermal buoyancy modifying the von Kármán street. Interestingly, at very low Re = 20 and 10, the von Kármán street completely disappears in the heated wakes, whereas the "Buoyancy-Opposing Vortex Street" remains as the sole vortex street characterising the flow. • Unsteady mixed convective flow vertically downward directed to across a heated circular cylinder, is studied. • The analysis was conducted at Re = 10, 20, 30, 40, 100 and for Richardson number ranging between Ri = 0–0.5. • The aim is to evaluate the influence of the buoyancy effects on the vortex shedding attributes. • Unusually Kármán vortex street is generated for R e ⩽ 40 by heating the cylinder. • A new vortex street, namely the "Opposing-Buoyancy Vortex Street", is discovered by heating the Kármán vortex street. [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]

• The advances injection timings and B100 improved the combustion characteristics. • The combination between injection timings and B100 has beneficial in reducing the NO X emissions. • The PM size distribution decreased during B100 combustion and retarded injection timing. • The average size of d po decreased with both effect of B100 and retarded injection timing. • The PM characteristics (size and concentrations) decreased under 5 BMEP compared with 2.5 BMEP. The combination between different conditions of fuel injection timings and biodiesel is a major challenge for the communities of vehicle research in terms of efficiency and emissions. The difficulties to achieving the emissions regulations in the recent years are linked to undesirable health effects and environmental impact. The effects of different engine conditions (injection timings and loads) on combustion, emissions, and particulate matter (PM) characteristics for diesel and biodiesel (B100) in diesel engine were experimentally investigated in this study. The combustion characteristics of cylinder pressure and rate of heat release (ROHR) were slightly higher during the combustion of B100 and advanced injection timing than during the combustion of diesel. Results have shown that THC and CO decreased from B100 combustion by 21% and 31% under 5 brake mean effective pressure (BMEP), respectively, and 32% and 46% under 2.5 BMEP of engine load compared to the diesel. Furthermore, advanced injection timing decreased CO and THC compared with retarded injection timing for B100 and diesel under both conditions of engine loads. However, nitrogen oxide (NO X) decreased (by 24%) with retarded injection timing and increased (by 7%) with advanced injection timing. Smoke number and particle number concentration decreased under conditions of advanced injection timing compared with retarded injection timings, especially during B100 combustion. In terms of particulate size, d po decreased by 26.6 nm during B100 combustion and by 32.7 nm during diesel combustion under different conditions of injection timings and engine loads. The oxygen-bond in B100 contributed to important benefits in terms of NO X and PM without substantial influence on combustion characteristics and efficiencies. [ABSTRACT FROM AUTHOR]

This paper aims to enhance the power production performance of the PV/T based on three cooling models using nanofluid, SiC-water and nano-PCM. The effect of solar irradiance and ambient temperature on the power productivity performance has been investigated based on sensitivity analysis that shows that electrical current and solar irradiance has more impact on power prediction than voltage and temperature. Also, three mathematical linear prediction models were developed and compared with the prediction of ANN models, and the results were verified and fit the experimental results. The comparison with published literature is made based on three common evaluation criteria that include the coefficient of determination R2, MSE and RSME. The proposed predicting models attained an excellent R2 result of 0.99 and MSE value of 0.006 and RSME of 0.009 for both P-M1 and P-M2 models. Besides, the P-M3 obtained an MSE value of 0.022. Finally, the proposed linear prediction models help to reduce the error in furcating future results and determine the best conditions for any solar system in an easy and fast way. • The study aimed to enhance the performance of (SiC-water and nano-PCM) PVT system. • A mathematical and ANN model for nanofluid and nano-PCM cooling PVT presented. • The proposed linear models are consistent with ANN model and experimental results. • The linear predicting models verified simple and accurate results. • The proposed PVT model electrical efficiency coincided with the literature results. [ABSTRACT FROM AUTHOR]

• In Iraq, building materials are transported and stored badly. • The percentage of cement and gypsum in the accumulated dust was high. • Studied materials deposition (even in small quantities) reduces transmissivity. • In dry cleaning used, the normal cement was the most difficult material to clean. • Technical gypsum has high degree of adhesion followed by sand. Different building materials such as sand, cement, and gypsum are transported and stored poorly in Iraq (open-air), so large amounts of them fly into the air and form part of the dust. In this study, collected amounts of dust deposited for three months studied in a controlled manner. The components of the accumulated dust were examined and found that the largest part of it (more than 50%) is silicon oxides (sand), the rest of which represent most significant part of the components of cement and gypsum. In this study, the accumulation of building materials (sand, ordinary cement, egg cement, gypsum, and industrial gypsum) studied on the power output of a photovoltaic module (PV). The effect of periodic cleaning and its duration on the lost power of the PV were also studied. The study results showed that the accumulation of these materials, even in small quantities on PV reduces the transmittance and reduces the resulting power because it prevents the arrival of solar irradiation to the PV. The accumulation of natural and white cement followed by sand and gypsum gave the most considerable loss of energy produced. The studied module cleaned without using any liquids so as not to react with the tested building materials. Natural cement is the most difficult of these materials in dry cleaning due to its particles' small size. The industrial gypsum causes the most substantial power reduction when accumulates in more than 25 g/m2. When studying the material's ability to adhere to the surface of the dry PV module, the industrial gypsum showed a high degree of adhesion followed by sand compared with the other studied materials. Three methods to prevent the dew water from being connected to the building material were studied, which is to clean the PV daily at the evening, cover the PV with plastic cover from evening until early morning, and turn the PV in the evening to face the ground. The first method limited in effectiveness, while the other two methods were effective in reducing dust accumulation damage and preventing its interaction with dew. [ABSTRACT FROM AUTHOR]

Summary: There are many photovoltaic/thermal (PV/T) systems' designs that are used mainly to reduce the temperature of the PV cell by using a thermal medium to cool the photovoltaic module. In this study, a PV/T system uses nano‐phase change material (PCM) and nanofluid cooling system was adopted. Three cooling models were compared using nanofluid (SiC‐water) and nano‐PCM to improve the performance and productivity of the PV/T system. Three mathematical models were developed for linear prediction, and their results were compared with the predicted artificial neural network results, results were verified, and experimental results were appropriate. Three common evaluation criteria were adopted to compare that the results of proposed forecasting models with other models developed in many research studies are done, including the R2, mean square error (MSE), and root‐mean‐square error (RMSE). Besides, different experiments were implemented using varying number of hidden layers to ensure that the proposed neural network models achieved the best results. The best neural prediction models deployed in this study resulted in good R2 score of 0.81 and MSE of 0.0361 and RMSE and RMSE rate is 0.371. Mathematical models have proven their high potential to easily determine the future outcomes with the preferable circumstances for any PV/T system in a precise way to reduce the error rate to the lowest level. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • An artificial neural network model for PV/T is presented. • Discretization of parameters and equation was made. • An experiment has been conducted to validate the proposed ANN models results. • Systems using water, nanofluid and nano-PCM moving through the cooling pipes are tested. • The comparison between different models results showed a good consistent and agreement. Abstract A Photovoltaic/Thermal (PV/T) system combines PV and thermal collector, which is considered promising technology especially for building integrated PV/T system. The PV/T cooling systems using water, water-PCM and nanofluid/nano-PCM moves through the cooling pipes were investigated, in this study. However, this paper focuses on testing different PV/T systems (conventional PV, water-based PVT, water-nanofluid PVT, and nanofluid/nano-PCM) under the same conditions and environment using one artificial neural network (ANN) based Multi-Layer Perceptron (MLP) system. Also, investigate the differences in the efficiency of these systems on both thermal and electrical when using only one simulation system (MLP). The proposed ANN approach proved that using of nanofluid/nano-PCM was enhanced the electrical efficiency from 8.07% to 13.32% and its thermal efficiency reached 72%. Also, the voltage was improved significantly. Many measurement methods were used for validating the results of the proposed ANN model like the Mean Absolute Error (MAE), Mean Square Error (MSE), Correlation (R), and coefficient of determination (R2). The proposed ANN model achieved a final MSE of 0.0229 in the training phase and 0.0282 in the cross-validation phase. The sensitivity analysis showed that the influence of solar irradiation and Amb-temp almost has a constant effect on electrical efficiency. However, the Ambient temperature had a significant impact on thermal efficiency. The results of the network were consistent with the experimental results of the current study and published works. [ABSTRACT FROM AUTHOR]

In this study, the techno-economic assessment of GCPVT with nanofluid has been investigated based on theoretical and experimental work in Malaysia. The productivity and utilisation of the PV have been investigated using yield and capacity factors (CFs), respectively. Also, the cost of energy and payback period has been calculated. The system installed, tested, and data have been collected. Evaluation of the system in terms of current, voltage, power and efficiency are presented. The average daily ambient temperature and total global solar energy in Kuala Lumpur are 38.89°C and 4062 Wh/m2, respectively. MATLAB software is used to analyse the measured data. The assessment results show that the GCPVT system has annual yield factor, CF, the cost of energy; payback period, and efficiency are (128.34-183.75) kWh/kWp, (17.82-25.52)%, 0.196 USD/kWh, 7-8 years and 9.1%, respectively. This study indicates that the GCPVT system with nanofluid improved the PV technical and economic performance. [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]

[Display omitted] • Adding CuO 2 nanoparticles to the RME improves the combustion characteristics. • BSFC significantly decreased with adding CuO 2 to the RME in comparison with neat RME. • The combination between EGR technology and CuO 2 has beneficial on the NO X reduction. • The concentration and number of soot particles decreased with addition of CuO 2 to the RME. • The average size of soot nanoparticles increased from both effect of CuO 2 and EGR. In recent years, the adding nano additives to the fuel is paid much attention by decreasing the exhaust emissions and enhance combustion characteristics without any modifications in diesel engine. The effects of copper dioxide (CuO 2) nanoparticles and exhaust gas recirculation (EGR) on combustion characteristics and morphological characteristics of soot nanoparticles in diesel engine fuelled with rapeseed methyl ester (RME) were investigated in this study. The good advantages of CuO 2 nanoparticles such as good thermal properties, oxygen storage, and density thermophysical properties of viscosity are encourage to using as nano additives into the biodiesel. The results showed that the pressure inside cylinder and ROHR improved by 4% and 11%, respectively, from adding CuO 2 nanoparticles into the RME in comparison neat RME. Furthermore, the BTE increased by 3.64%, 7.36%, 9.28% and 12.43% with adding CuO 2 to the RME, while the BSFC decreased by 5.26%, 7.47%, 9.68% and 12.73% when adding nanoparticles to the RME under 25%, 50%, 75% and 100% of engine load, respectively, in comparison with diesel fuel. Adding CuO 2 nanoparticles to the RME and 20% rate of EGR significantly decrease the NO X emissions by 29.64% when compared to the without nano additives. The number and concentration of soot nanoparticles were decreased with addition of CuO 2 nanoparticles to the RME and they increased with presence EGR technology. It is indicated that the soot nanoparticles concentration decreased or was in par with neat RME when incorporation between EGR and nano additives. The morphological parameters such as number of soot primary particles (n po) exhibits significant reduction by 18%, meanwhile slightly increase in the average diameter of soot primary particles (d po) by 7% with adding CuO 2 to the RME for with and without EGR. [ABSTRACT FROM AUTHOR]