• Energy Research

En raison de l'industrialisation et de l'urbanisation rapides, l'augmentation des émissions de carbone dans l'atmosphère et l'épuisement des réserves de combustibles fossiles et de gaz ont obligé à trouver des sources d'énergie renouvelables alternatives, où l'énergie solaire est l'une des sources les plus prometteuses. Les capteurs solaires à auges paraboliques (PTC) peuvent transférer efficacement une température élevée dans le tube du récepteur jusqu'à 400 °C. Dans cette étude, l'analyse de la dynamique des fluides computationnelle (CFD) est utilisée pour analyser l'effet de plusieurs fluides de travail sur l'efficacité du CTP. Deux types différents de nanofluides utilisés pour analyser l'efficacité thermique du PTC par le biais de simulations CFD sont les nanofluides d'alumine et d'oxyde de cuivre. La concentration d'oxyde de cuivre et d'alumine a été maintenue à 0,01 % dans les nanofluides. L'efficacité pour le PTC est calculée à deux débits massiques différents, à savoir 0,0112 kg/s et 0,0224 kg/s. L'efficacité la plus élevée est de 13,01 et 13,1 % en utilisant Al2O3 comme nanofluides à des débits de 0,0112 kg/s et 0,0224 kg/s, tandis que CuO a une efficacité de 13,92 % et 14,79 % pour ces débits. Le comportement du matériau du tube absorbant sur la distribution de la température pour l'acier, le cuivre et l'aluminium en tant que matériau du tube absorbant a également été étudié. Le changement de matériau de l'acier au cuivre et à l'aluminium a augmenté la température de sortie du fluide. La température de sortie maximale a été atteinte pour le cuivre est de 311 K tandis que l'acier et l'aluminium ont montré une température inférieure de 307 K et 308 K du fluide à la sortie. En outre, l'impact de la longueur du tube récepteur sur la température du fluide de travail est également étudié. Le nanofluide d'oxyde de cuivre a une température plus élevée à la sortie pour les deux débits massiques par rapport au nanofluide d'alumine. En conséquence, une comparaison a été faite pour les résultats CFD avec les résultats expérimentaux de la littérature. Le système PTCS basé sur les nanofluides est une méthode prometteuse pour les applications environnementales durables. Debido a la rápida industrialización y urbanización, el aumento de las emisiones de carbono en la atmósfera y el agotamiento de las reservas de combustibles fósiles y gas han obligado a encontrar fuentes alternativas de energía renovable, donde la energía solar es una de las fuentes más prometedoras. Los colectores solares de cilindro parabólico (PTC) pueden transferir eficazmente altas temperaturas en el tubo del receptor hasta 400 °C. En este estudio, se utiliza el análisis de dinámica de fluidos computacional (CFD) para analizar el efecto de múltiples fluidos de trabajo sobre la eficiencia del PTC. Dos tipos diferentes de nanofluidos utilizados para analizar la eficiencia térmica de PTC a través de simulaciones CFD son los nanofluidos de alúmina y óxido de cobre. La concentración de óxido de cobre y alúmina se mantuvo al 0,01% en los nanofluidos. La eficiencia para PTC se calcula a dos caudales másicos diferentes, es decir, 0.0112 Kg/s y 0.0224 Kg/s. La eficiencia más alta es de 13.01 y 13.1% utilizando Al2O3 como nanofluidos a 0.0112 Kg/s y 0.0224 Kg/s de caudales, mientras que CuO tiene una eficiencia de 13.92% y 14.79% para estos caudales. También se investigó el comportamiento del material del tubo absorbente en la distribución de temperatura para acero, cobre y aluminio como material del tubo absorbente. Cambiar el material de acero a cobre y aluminio aumentó la temperatura de salida del fluido. La temperatura máxima de salida se logró para el cobre es de 311 K, mientras que el acero y el aluminio mostraron una temperatura más baja de 307 K y 308 K del fluido en la salida. Además, también se estudia el impacto de la longitud del tubo receptor en la temperatura del fluido de trabajo. El nanofluido de óxido de cobre tiene una temperatura más alta en la salida para ambos caudales másicos en comparación con el nanofluido de alúmina. En consecuencia, se hizo una comparación de los resultados del CFD con los hallazgos experimentales de la literatura. El sistema PTCS basado en nanofluidos es un método prometedor para las aplicaciones ambientales sostenibles. Due to rapid industrialization and urbanization, upward rise in carbon emissions in the atmosphere, and depletion of fossil fuel and gas reserves have forced to find alternative renewable energy resources, where solar energy is one of the most promising source. Parabolic trough solar collectors (PTCs) can effectively transfer high temperature in the tube of receiver upto 400 °C. In this study, Computational Fluid Dynamics (CFD) analysis is used to analyse the effect of multiple working fluids on efficiency of the PTC. Two different types of nanofluids used for analyising the thermal efficiency of PTC through CFD simulations, are Alumina and Copper-oxide nanofluids. The concentration of Copper Oxide and Alumina was kept to 0.01% in the nanofluids. The efficiency for PTC is calculated at two different mass flow rates i.e., 0.0112 Kg/s and 0.0224 Kg/s. The highest efficiency is 13.01 and 13.1% using Al2O3 as nanofluids at 0.0112 Kg/s and 0.0224 Kg/s flow rates, while CuO has an efficiency of 13.92% and 14.79% for these flow rates. The behaviour of absorber tube material on temperature distribution for steel, copper and aluminum as absorber tube material was also investigated. Changing the material from steel to copper and aluminum increased the outlet temperature of the fluid. The maximum output temperature was achieved for copper is 311 K while steel and aluminum showed lower temperature of 307 K and 308 K of the fluid at the outlet. Furthermore, the impact of the receiver tube's length on the working fluid's temperature is also studied. Copper Oxide nanofluid has higher temperature at the outlet for both mass flow rates as compared to alumina nanofluid. Accordingly, a comparison was made for the CFD results with the experimental findings from literature. The nanofluids based PTCs system is promising method for the sustainable environment applications. وبسبب التصنيع السريع والتحضر، فإن الارتفاع التصاعدي في انبعاثات الكربون في الغلاف الجوي، واستنفاد احتياطيات الوقود الأحفوري والغاز قد أجبر على إيجاد موارد بديلة للطاقة المتجددة، حيث تعد الطاقة الشمسية واحدة من أكثر المصادر الواعدة. يمكن لمجمعات الطاقة الشمسية ذات الحوض المكافئ (PTCs) نقل درجة الحرارة العالية بشكل فعال في أنبوب جهاز الاستقبال حتى 400 درجة مئوية. في هذه الدراسة، يتم استخدام تحليل ديناميكيات الموائع الحسابية (CFD) لتحليل تأثير سوائل العمل المتعددة على كفاءة معامل الحرارة الإيجابي. هناك نوعان مختلفان من السوائل النانوية المستخدمة لتحليل الكفاءة الحرارية لـ PTC من خلال محاكاة CFD، وهما السوائل النانوية من الألومينا وأكسيد النحاس. تم الحفاظ على تركيز أكسيد النحاس والألومينا عند 0.01 ٪ في السوائل النانوية. يتم حساب كفاءة معامل الحرارة الإيجابي بمعدلي تدفق كتلي مختلفين، أي 0.0112 كجم/ثانية و 0.0224 كجم/ثانية. أعلى كفاءة هي 13.01 و 13.1 ٪ باستخدام Al2O3 كسوائل نانوية عند 0.0112 كجم/ثانية و 0.0224 كجم/ثانية معدلات التدفق، في حين أن CuO لديه كفاءة 13.92 ٪ و 14.79 ٪ لمعدلات التدفق هذه. كما تم التحقيق في سلوك مادة أنبوب الامتصاص على توزيع درجة الحرارة للصلب والنحاس والألومنيوم كمادة أنبوب الامتصاص. أدى تغيير المادة من الفولاذ إلى النحاس والألومنيوم إلى زيادة درجة حرارة مخرج السائل. تم تحقيق أقصى درجة حرارة خرج للنحاس هي 311 كلفن بينما أظهر الفولاذ والألومنيوم درجة حرارة أقل من 307 كلفن و 308 كلفن من السائل عند المخرج. علاوة على ذلك، يتم أيضًا دراسة تأثير طول أنبوب المستقبل على درجة حرارة سائل التشغيل. يحتوي السائل النانوي لأكسيد النحاس على درجة حرارة أعلى عند المخرج لكل من معدلات التدفق الكتلي مقارنةً بالمائع النانوي للألومينا. وفقًا لذلك، تم إجراء مقارنة لنتائج عقود الفروقات مع النتائج التجريبية من الأدبيات. يعد نظام PTCS القائم على السوائل النانوية طريقة واعدة لتطبيقات البيئة المستدامة.

Abstract This study aims to evaluate performance of 30 models (15 selected from literature and 15 newly developed) to estimate diffuse horizontal irradiance (Hd) using high-quality measurements for nine stations having different climatic conditions. The models (divided into three categories) are based on extraterrestrial global horizontal irradiance (Ho) and measured global horizontal irradiance (Hg) using sunshine duration ratio, clearness-index, temperature, relative humidity, and periodicity factor as input parameters. The performance of models was evaluated using statistical parameters; the performance of Hg based models (Category-II and Category-III) is better than Ho based models (Category-I). The performance of newly developed models in three categories is better than best models selected from the literature, due to higher number of input parameters and higher powers used. The best models in Category-I, Category-II and Category-III have rMBE (rRMSE) ranges from −0.3 to 0.6% (14 to 20%), −0.6 to 0.1% (10 to 17%) and −0.3 to 0.0% (10 to 17%) respectively. The performance of models varies in different zones, and different stations within same zone, due to variations of climatic conditions. The best models have rMBE within ±1% and rRMSE

Abstract Energy densification of biomass is usually done by pelletizing the raw biomass and then its torrefaction to obtain clean fuel from renewable resources. The objective of this study is to compare the untorrefied and torrefied pellets of two agricultural biomass residues as cotton waste (CW) and wheat straws (WS) with the different mixing ratios i.e., 100:0, 75:25, 25:75, 50:50, 0:100, respectively. Torrefaction of the pure biomass and their blending pellets were performed at 300 °C in a tube furnace at a heating rate of 10 °C/min with a residence time of 30 min. Characterization of untorrefied pellets showed slightly increase in carbon contents and its energy contents enhancement due to densification of the biomass residue owing to pelletization. Furthermore, its blends showed higher carbon content with the addition of cotton waste. Moreover, mass and energy yield data and Van Krevelon plot showed that the torrefied pellets with high CW to WS ratio specified even more rise in carbon contents and energy value due to high rate of devolatilization of hemicelluloses in CW residue. Finally, torrefaction severity index revealed that CW dictates its high degree of degradation as compared to WS which is an indication of high rate of hydrogen and oxygen loss and resulting enhancement in carbon content. Experimental results showed increased values of carbon contents and energy contents, which shows significant synergistic effect of blending and torrefaction to produce carbon rich solid biofuel. As a result carbon contents and calorific value of blended 25% WS + 75%CW torrefied pellets increased from 41.5 % to 64.84 % and 18.322 MJ/Kg to 28.5 MJ/K g respectively, similarly energy yield and torrefaction index showed higher values of 91.67 % and 1.379 respectively compared to untorrefied pellets.

The burning of fossil fuels in power sectors for energy generating purposes and in agricultural country like Pakistan the residues of crops on large area of land are burnt every year that results in continuous addition of CO2 in environment. CO2 capture through solid based adsorbents is one of the best valued, echo friendly and techno-economic processes. The present research involves the development of activated carbons using five different waste biomass materials through single step chemical activation for effective CO2 adsorption, study of isosteric heat of adsorption and change in these values with a change in level of CO2 adsorbed. Chemical activation with single-step method was carried out to prepare the adsorbents. The samples were characterized and compared for the textural properties by recording isotherms of nitrogen adsorption at temperature of 77 K while CO2 adsorption curves at 273 K then at 298 K. SEM was brought into use to investigate morphological characters, surface morphology of activated carbons that confirms the presence of random micro-pores. Nonlinear density functional theory (NDLFT) strengthen the fact that CO2 adsorption depends upon the volume of pores. Samples have pore volume ranging from 0.11 cm3 to 0.44 cm3, whereas BET surface area values were observed from 439 m2/g up to 979 m2/g. Among the prepared activated carbons, the sample with date seeds as base material showed the uppermost uptake of 5.8 mmol/g at 273 K. Linear fitting of the curve between CO2 adsorbed and pore volume at a temperature of 273 K and 298 K with R2 values greater than 0.9 demonstrate the strong relation between pore volume, temperature and CO2 adsorbed. Isosteric heat of adsorption (IHA) values were found to be in the assortment of 44 KJ/mol with minimum value of 14.3 KJ/mol that decreases with increase of CO2 adsorption. High isosteric heat means strong interaction of CO2 molecules and prepared adsorbents. Obtained results confer base to use waste biomass materials for development of solid based adsorbents and use of these adsorbents in effective carbon capture applications to reduce the carbon footprints in the environment and avoid the waste burning of biomass residues. © 2021 Elsevier Ltd

En raison de l'industrialisation rapide et de l'épuisement des combustibles fossiles, les ressources renouvelables alternatives sont obligatoires, l'énergie solaire thermique étant l'une des alternatives prometteuses. Dans cette étude, une enquête expérimentale a été menée pour analyser la performance thermique de différents modules photovoltaïques dans des conditions climatiques variables. Il s'agit notamment du diséléniure d'indium et de cuivre en plaque mince, du silicium monocristallin, du silicium micro-cristallin, du silicium amorphe et du silicium poly-cristallin. L'analyse s'est concentrée sur l'évaluation de l'efficacité du module, du taux d'absorption de l'irradiance solaire, de la puissance de sortie maximale, du rapport de performance, de l'efficacité de la puissance de sortie normalisée et de l'effet de la température sur chaque module dans des conditions extérieures opérationnelles réelles. Le module en silicium monocristallin a montré une efficacité moyenne élevée de 20,8 % et un rapport de performance moyen de 1,21 par rapport aux autres modules photovoltaïques. Il a été observé que tous les types de modules ont une température moyenne plus élevée en saison estivale et ont montré un faible rapport de performance et une faible efficacité du module par rapport à la saison hivernale. Puissance moyenne normalisée en silicium monocristallin 56,2% plus efficace que les autres modules. L'augmentation des performances thermiques du silicium monocristallin était liée à son taux d'absorption élevé et à son taux de conduction élevé. Ainsi, le module photovoltaïque en silicium monocristallin est le meilleur candidat potentiel pour la technique de capture solaire à utiliser dans diverses applications d'énergie solaire thermique. Debido a la rápida industrialización y al agotamiento de los combustibles fósiles, los recursos renovables alternativos son obligatorios, donde la energía solar térmica es una de las alternativas prometedoras. En este estudio, se realizó una investigación experimental para analizar el rendimiento térmico de diferentes módulos fotovoltaicos en diferentes condiciones climáticas. Estos incluyen diseleniuro de indio de cobre de placa delgada, silicio monocristalino, silicona microcristalina, silicio amorfo y silicio policristalino. El análisis se concentró en la evaluación de la eficiencia del módulo, la tasa de absorción de irradiancia solar, la salida de potencia máxima, la relación de rendimiento, la eficiencia de salida de potencia normalizada y el efecto de la temperatura en cada módulo en condiciones exteriores operativas reales. El módulo de silicio monocristalino mostró una alta eficiencia media del 20,8% y una relación de rendimiento media de 1,21 en comparación con los otros módulos fotovoltaicos. Se observó que todos los tipos de módulos tienen una temperatura media más alta en la temporada de verano y mostraron una baja relación de rendimiento y una baja eficiencia del módulo en comparación con la temporada de invierno. Potencia media normalizada a partir de silicio monocristalino un 56,2% más eficiente que los otros módulos. El aumento del rendimiento térmico del silicio monocristalino se relacionó con su alta tasa de absorción y alta tasa de conducción. Por lo tanto, el módulo fotovoltaico de silicio monocristalino es el mejor candidato potencial para la técnica de captura solar que se utilizará en diversas aplicaciones de energía solar térmica. Due to rapid industrialization, and depletion of fossil fuels, alternative renewable resources are mandatory, where solar thermal energy is one of the promising alternate. In this study, an experimental investigation was conducted to analyze the thermal performance of different photovoltaic-modules under varying climate conditions. These include thin plate Copper indium diselenide, mono-crystalline silicon, micro crystalline silicone, amorphous silicon and poly-crystalline silicon. The analysis was concentrated on the evaluation of module efficiency, solar irradiance absorption rate, maximum power output, performance ratio, normalized power output efficiency and temperature effect on each module at real operational outdoor conditions. Mono-crystalline silicon module showed high average efficiency of 20.8% and average performance ratio 1.21 compared to the other PV modules. It was observed that all types of modules have higher average temperature in summer season and showed low performance ratio and low module efficiency as compared to winter season. Average normalized power out of mono-crystalline silicon 56.2% more efficient than the other modules. The increased thermal performance of mono-crystalline silicon was related with its high absorption rate and high conduction rate. Thus, mono-crystalline silicon PV module is the best potential candidate for solar capturing technique to be utilize in diverse solar thermal energy applications. نظرًا للتصنيع السريع، ونضوب الوقود الأحفوري، فإن الموارد المتجددة البديلة إلزامية، حيث تعد الطاقة الحرارية الشمسية واحدة من البدائل الواعدة. في هذه الدراسة، تم إجراء تحقيق تجريبي لتحليل الأداء الحراري للوحدات الكهروضوئية المختلفة في ظل ظروف مناخية مختلفة. وتشمل هذه الصفائح الرفيعة ديسلينيد الإنديوم النحاسي، والسيليكون أحادي البلورة، والسيليكون البلوري الدقيق، والسيليكون غير المتبلور، والسيليكون متعدد البلورات. ركز التحليل على تقييم كفاءة الوحدة، ومعدل امتصاص الإشعاع الشمسي، والحد الأقصى لخرج الطاقة، ونسبة الأداء، وكفاءة خرج الطاقة الطبيعية وتأثير درجة الحرارة على كل وحدة في الظروف الخارجية التشغيلية الحقيقية. أظهرت وحدة السيليكون أحادية البلورة متوسط كفاءة مرتفع بنسبة 20.8 ٪ ومتوسط نسبة الأداء 1.21 مقارنة بالوحدات الكهروضوئية الأخرى. لوحظ أن جميع أنواع الوحدات لديها متوسط درجة حرارة أعلى في موسم الصيف وأظهرت نسبة أداء منخفضة وكفاءة منخفضة للوحدة مقارنة بموسم الشتاء. متوسط الطاقة الطبيعية من السيليكون أحادي البلورة 56.2 ٪ أكثر كفاءة من الوحدات الأخرى. كان الأداء الحراري المتزايد للسيليكون أحادي البلورة مرتبطًا بمعدل الامتصاص العالي ومعدل التوصيل العالي. وبالتالي، فإن وحدة السيليكون أحادية البلورة الكهروضوئية هي أفضل مرشح محتمل لتقنية التقاط الطاقة الشمسية لاستخدامها في تطبيقات الطاقة الحرارية الشمسية المتنوعة.

As the demand for energy continues to rise unabated, an examination of the constraints posed by finite fossil fuel reserves becomes crucial. There is need to explore and underscore the imperative shift towards renewable energy resources, where, solar energy is widely available and can readily be used in different applications, especially in water desalination applications. In the present research, photothermal performance of water based nanofluids containing graphene oxide (GO), zinc oxide (ZnO), iron oxide (FeO), and their composites (GO-ZnO and GO-FeO) have been studied under the natural sun to determine the potential for water desalination applications. All type of the nanofluid are prepared through a two-step method and are characterized morphologically using a scanning electron microscope (SEM). UV–visible spectroscopy is used to assess the optical absorbance of prepared nanofluids. The outcomes of this study show that pure GO nanofluids exhibited excellent absorption in the visible and near-infrared regions as compared to other nanofluids used in this research study, which makes them efficient nanofluids in converting solar energy into heat. For more assessment, a direct or volumetric solar thermal collector was used to evaluate the photothermal efficiency of water based nanofluids GO, ZnO, FeO, and their binary composites of GO-ZnO, and GO-FeO under natural solar flux at weight concentrations (0.01 wt%). The sensible heating efficiency due to the rise in temperature and latent heat of evaporation efficiency due to mass loss of nanofluid samples contributed towards photothermal efficiency. Pure GO nanofluids showed the highest photothermal efficiency, which is 71 % among all the nanofluids used in this study due to their carbon-based structure, highest optical absorption peak, excellent dispersion stability, and highest thermal conductivity. This experimental work also revealed that binary nanofluids containing composites of (GO-ZnO) and (GO-FeO) showed higher photothermal efficiency as compared to individual nanofluids ZnO and FeO except graphene oxide GO. According to the results and observation of this experimental work, pure GO-based nanofluids are potential candidates for direct absorption solar collection used in water desalination applications.

This study focused on evaluating the lubricity of diesel–biodiesel fuel with oxygenated alcoholic and nano-particle additives. Fuel injection system lubrication depended primarily on the fuel used in the diesel engine. Palm–sesame oil blend was used to produce biodiesel using the ultrasound-assisted technique. B30 fuel sample as a base fuel was blended with fuel additives in different proportions prior to tribological behavior analysis. The lubricity of fuel samples measured using HFRR in accordance with the standard method ASTM D6079. All tested fuels’ Tribological behavior examined through worn steel balls and plates using scanning electron microscopy (SEM) to assess wear scar diameter and surface morphology. During the test run, the friction coefficient was measured directly by the HFRR tribometer system. The results exhibited that B10 (diesel) had a very poor coefficient of friction and wear scar diameter, among other tested fuels. The addition of oxygenated alcohol (ethanol) as a fuel additive in the B30 fuel sample decreased the lubricity of fuel and increased the wear and friction coefficient, among other fuel additives. B30 with DMC showed the least wear scar diameter among all tested fuels. B30 with nanoparticle TiO2exhibited the best results with the least wear scar diameter and lowest friction coefficient among all other fuel samples. B30+DMC demonstrated significant improvement in engine performance (BTE) and carbon emissions compared to different tested samples. B30+TiO2 also showed considerable improvement in engine characteristics.

A cost-effective alternative for lowering carbon emissions from building heating is the use of flat-plate solar collectors (FPSCs). However, low thermal efficiency is a significant barrier to their effective implementation. Favorable nanofluids’ thermophysical properties have the potential to increase FPSCs’ effectiveness. Accordingly, this study evaluates the performance of an FPSC operating with Fe3O4-water nanofluid in terms of its thermo-hydraulic characteristics with operating parameters ranging from 303 to 333 K for the collector inlet temperature, 0.0167 to 0.05 kg/s for the mass flow rate, and 0.1 to 2% for nanoparticles’ volume fraction, respectively. The numerical findings demonstrated that under identical operating conditions, increasing the volume fraction up to 2% resulted in an improvement of 4.28% and 8.90% in energy and energy efficiency, respectively. However, a 13.51% and 7.93% rise in the friction factor and pressure drop, respectively, have also been observed. As a result, the performance index (PI) criteria were used to determine the optimal volume fraction (0.5%) of Fe3O4 nanoparticles, which enhanced the convective heat transfer, exergy efficiency, and energy efficiency by 12.90%, 4.33%, and 2.64%, respectively.