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Abstract An experimental study on the performance of double pass Solar Air Heater (SAH) having a new designed absorber is performed. The new SAH absorber is constructed from conductive aluminum tubes adjacent to each other and installed in the same direction of the air flowing inside the SAH. The new SAH performance (called Tubular Solar Air Heater (TSAH)) is studied at various mass flow rates of air inside the SAH. Moreover, it is compared with the performance of Flat plate Solar Air Heater (FSAH) having the same dimensions and materials of the TSAH except the absorber design. Findings indicate that the TSAH has higher outlet air temperature, efficiency and net energy gain and lower top heat loss compared to FSAH. TSAH achieves maximum air temperature rise more than 6 °C compared to FSAH at 0.025 kg/s. TSAH efficiency is greater than FSAH efficiency by about 19.4%, 21%, and 40.3%, at inlet air flow rate of 0.075 kg/s, 0.05 kg/s and 0.025 kg/s, respectively. The outlet air temperature and top thermal energy loss of the TSAH decrease with increasing the air mass flow rate, while its efficiency, energy output, and pressure drop increase. Moreover, TSAH efficiency in case of double air pass is greater than single air pass. Despite the TSAH pressure drop is greater than FSAH pressure drop, but its value is very small to impact the TSAH net thermal energy gain. The designed TSAH performance is found greater than the performance of FSAH and previous designs of published SAHs.

Abstract An experimental work is presented on the performance of solar air heater (SAH) has new designed absorber of finned transverse plate of lateral gaps and central holes. Moreover, a complete heat transfer analysis of the radiation and convection and SAH thermal performance are presented and discussed. The performance of this transverse SAH (TR_SAH) is compared with identical conventional flat plate SAH (FP_SAH) for single (SP) and double-pass (DP) airflow and air mass flow rates (AMFR) of 0.025, 0.05, and 0.075 kg/s. The experimental study is performed under hot climate conditions of Upper Egypt. The findings show that for all studied cases, TR_SAH has higher energy gain, output air temperature, thermal efficiency, and Nusselt number on the absorber plate, thermal-hydraulic performance parameter, and pressure drop compared to FP_SAH. The energy loss and radiation and convection Nusselt number on the TR_SAH glass plate is lower than that of FP_SAH. The maximum TR_SAH energy efficiency of value of about 89% is achieved in the case of DP airflow and high AMFR of 0.075 kg/s, with an enhancement of 24.2% compared to FP_SAH. The higher TR_SAH efficiency at these conditions reflects the optimal TR_SAH absorber design especially at high AMFR and using DP airflow. Despite TR_SAH air pumping power is greater than FP_SAH but it has a negligible effect on net energy gain.

Abstract The present work aims to improve the performance of tubular solar still by introducing a new design is conducted. A proposed modified tubular solar still is prepared by modifying the design of trough in the shape of half two concentric cylinders integrated with cylindrical parabolic concentrators (CPC). In the modifying design, the trough was proposed in the form of half two concentric cylinders of increases the absorbing surface area of the solar radiation. Besides, the CPC was used to increase the intensity of the solar radiation falling on the absorbent surface. Also, the effect of saltwater layer thickness between the half two concentric cylinders on the performance of modified tubular still was studied to obtain the optimal saltwater layer thickness. A different saltwater layer thickness was studied and compared to the traditional tubular still with a rectangular trough to obtain the optimal design. Experimental results showed that the improvement in accumulated productivity of the modified tubular still reached to 87.9%, 90.8%, 81.9%, and 68.1% for the saltwater layer thickness 1, 2, 3, and 4 cm, respectively compared to traditional tubular still with a rectangular trough. Also, the daily efficiency of modified design reached 60.4%, 61.4%, 58.5%, and 54.1% for the saltwater layer thickness 1, 2, 3, and 4 cm, respectively. But for the traditional case, the daily efficiency reached 32.2%. It is clear that the modified design of tubular solar still is more effective, and the optimal thickness of the saltwater layer between half two concentric cylinders is 2 cm.

Une étude numérique de la performance d'une fenêtre intelligente à panneaux multiples intégrée à des cellules solaires GaAsP/InGaAs QWSC (∼32% d'efficacité) de troisième génération refroidies à l'eau et éclairées par des concentrateurs solaires de suivi à deux axes à 500× dans l'espace inter-vitre est présentée. L'optimisation des paramètres du système tels que le taux de concentration optique et le débit de liquide de refroidissement (eau) est essentielle afin d'éviter la dégradation des performances du système en raison des températures élevées des cellules et des contraintes thermiques. Une modélisation détaillée des caractéristiques thermo-fluidiques du système de fenêtres intelligentes a été entreprise à l'aide d'un package CFD à volume fini. Les résultats de cette analyse qui a pris en compte les processus d'échange de chaleur conducteurs, convectifs et radiatifs se déroulant à l'intérieur du système de fenêtre intelligente ainsi que l'échange de chaleur vers l'environnement ambiant interne et externe sont présentés. Se presenta una investigación numérica del rendimiento de una ventana inteligente de paneles múltiples integrada con células solares QWSC de GaAsP/InGaAs de tercera generación de alta eficiencia refrigeradas por agua (~32% de eficiencia) iluminadas por concentradores solares de seguimiento de dos ejes a 500× en el espacio entre paneles. La optimización de los parámetros del sistema, como la relación de concentración óptica y el caudal de refrigerante (agua), es esencial para evitar la degradación del rendimiento del sistema debido a las altas temperaturas de la celda y las tensiones térmicas. El modelado detallado de las características del termofluido del sistema de ventanas inteligentes se llevó a cabo utilizando un paquete de CFD de volumen finito. Se presentan los resultados de este análisis que consideró los procesos de intercambio de calor conductivo, convectivo y radiativo que tienen lugar en el interior del sistema de ventanas inteligentes, así como el intercambio de calor al entorno ambiental interno y externo. A numerical investigation of the performance of a multi paned smart window integrated with water-cooled high efficiency third generation GaAsP/InGaAs QWSC (∼32% efficiency) solar cells illuminated by two-axis tracking solar concentrators at 500× in the inter pane space is presented. Optimising system parameters such as optical concentration ratio and coolant (water) flow rate is essential in order to avoid degradation in system performance due to high cell temperatures and thermal stresses. Detailed modelling of the thermo-fluid characteristics of the smart windows system was undertaken using a finite volume CFD package. Results of this analysis which considered the conductive, convective and radiative heat exchange processes taking place in the interior of the smart window system as well as the heat exchange to the internal and external ambient environment are presented. يتم تقديم تحقيق رقمي لأداء نافذة ذكية متعددة الأجزاء مدمجة مع خلايا شمسية من الجيل الثالث GaAsP/InGaAs عالية الكفاءة مبردة بالماء (32 ٪ كفاءة) مضاءة بواسطة مكثفات شمسية ثنائية المحور عند 500× في الفضاء الداخلي. يعد تحسين معلمات النظام مثل نسبة التركيز البصري ومعدل تدفق سائل التبريد (الماء) أمرًا ضروريًا لتجنب التدهور في أداء النظام بسبب ارتفاع درجات حرارة الخلايا والضغوط الحرارية. تم إجراء النمذجة التفصيلية لخصائص السوائل الحرارية لنظام النوافذ الذكية باستخدام حزمة العقود مقابل الفروقات ذات الحجم المحدود. يتم عرض نتائج هذا التحليل الذي أخذ في الاعتبار عمليات التبادل الحراري الموصلة والحملية والإشعاعية التي تحدث في الجزء الداخلي من نظام النوافذ الذكية بالإضافة إلى التبادل الحراري إلى البيئة المحيطة الداخلية والخارجية.

Abstract This paper presents a field study for the performance of photovoltaic thermal (PVT) system that use aluminium cooling plate with straight and helical channels during July 2016. Three systems each of 0.37 m2 commercial poly-crystalline PV panels have been installed at the faculty of engineering at Shoubra, Benha University, Cairo, Egypt (30.1°N Latitude). Two of the systems are cooled using straight and helical channels with dimensions of 10 × 10 mm 2 and compared with the uncooled panel. The results showed that an increase in average electrical efficiency of 17.7% to 38.4% with relative to uncooled panels for flow rate range of 0.25 to 1 L/min. The corresponding average thermal efficiency increases from 31.6% to 47.2% for straight channels and 34.6% to 57.9% for helical configuration. While the corresponding average exergy efficiency increases from 11.1% to 12.9% for straight channels and 11.5% to 13.5% for helical arrangement. The associated water pumping power in both configurations does not exceed 3.3% of the converted electrical power while the increase in the obtained electrical power is of 30% with relative uncooled cell power.

Abstract Si3N4/MoS2 nanocomposite has been fabricated through a solvothermal process and Mixed with polystyrenesulfonate-doped poly (3, 4-ethylenedioxythiophene) to prepare (Si3N4/MoS2-PEDOT: PSS) as a counter electrode (CE) for bifacial dye-sensitized solar cells (DSSCs). The electrochemical studies confirm that Si3N4/MoS2-PEDOT: PSS CEs exhibits higher catalytic activity compared with pristine Si3N4/MoS2 and PEDOT: PSS. The DSSCs with 5% Si3N4/MoS2-PEDOT: PSS composite CE achieves conversion efficiency (PCE) of 7.16%, which is comparable to that of the conventional platinum CE (7.50%) and better than those of the pristine Si3N4/MoS2 (3.80%) or PEDOT: PSS (4.20%) CEs. Owing to the optical transparency of Si3N4/MoS2-PEDOT: PSS composite CEs, bifacial DSSCs based on 5% Si3N4/MoS2-PEDOT: PSS CE yield 2.03% PCE from rear irradiation. The simple preparation method, high catalytic activity and electrochemical stability demonstrate that Si3N4/MoS2-PEDOT: PSS can be used a transparent CE in bifacial DSSCs.

Abstract An experimental investigation is performed on the impact of utilizing a thermal energy storage of phase change material (PCM) on the performance of single acting solar still coupled with photovoltaic module (PV) by new integration. The integration of the PV with the still is based on installing directly the PV module over the still condenser where the PV uses the same solar still space. Installing the PV over the still transmits the reflected solar energy from the PV to the saline water in the still basin and the PV output power is also transmitted directly to the saline water. The impact of integrating PCM with the still basin on the still performance is studied for the conventional solar still (CSS) and modified still (CSS + PV) and for forced air cooling (FAC) of the modified still condenser (PCM + CSS + PV). Additionally, the impact of using PV as only a reflector on the still performance is illustrated. The findings indicate that integrating the PV with the CSS increases its productivity by 9%. Using PCM unit with the still coupled with PV increases their daily yield by about 11.7% while using FAC with (CSS + PV + PCM) rises this daily yield by 19.4%. Using PV as a reflector with CSS rises its productivity by 3.5% and lower its production cost compared to CSS. Moreover, the positive impact of the FAC or PCM on the still performance increases with increasing the PV power where using PCM with (CSS + PV) increases its efficiency by about 20%. Using FAC with the system (CSS + PCM and PV) reduces its freshwater yield cost and increases its efficiency.

Abstract In this paper an optimal performance of three phase induction motor drives a centrifugal water pump and fed from photovoltaic (PV) system without storage elements during starting and running is presented. A three level three phase inverter is used to convert the DC voltage from the PV array to a variable voltage and frequency to supply the three phase induction motor. The output voltage and frequency of the inverter are controlled to extract the maximum power from solar panel during running at different levels of irradiance and temperatures using a Teaching Learning Based Optimization (TLBO) algorithm with minimum motor losses. The ratio of voltage magnitude and frequency is held within rated values to avoid saturation and motor overheating. The rating of PV array is chosen to develop the rated power of the pump at normal irradiance and temperature. The output voltage of the inverter is controlled during starting to prevent an excessive current from PV and to develop a torque larger than pump torque. An artificial neural network (ANN) is developed to give an optimal inverter voltage and frequency to extract maximum power from the PV array. The complete model is simulated using MATLAB/Simulink. The simulated results emphasize the significance of the proposed method to attain the maximum power from PV with minimum motor losses.