• 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.

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

Abstract Kaolinite nanotubes were synthesized by exfoliation and scrolling process for kaolinite sheets and then doped with potassium ions (K+/KNTs) forming a novel basic catalyst of promising activity in the transesterification reactions. The synthetic K+/KNTs catalyst displayed well-developed nanotube morphology with an average pore diameter of 14.5 nm, surface area of 112 m2/g, and total basicity of 7.43 mmol OH/g. The catalyst was applied in the transesterification of waste samples for sunflower cooking oil based on statistical design. The statistical design was built based on the response surface methodology in conjunction with the central composite design. The obtained results considering the interaction between the different factors (time, temperature, catalyst loading, and methanol-to-oil ratio) reflected achieving maximum biodiesel yield of 98%. This value was obtained after conducting the test for 4 h using 6 wt, of K+/KNTs as catalyst loading in the presence of 15:1 methanol-to-oil ratio at a reaction temperature of 90 °C. Considering the suggested optimization solutions from the design, K+/KNTs catalyst can achieve biodiesel yield of 99.4% if the conditions adjusted at 5.5 h as time interval, 4.96 wt, % as loading, 103.3 °C as temperature, and 14.64:1 as a methanol-to-oil ratio. The properties of the biodiesel sample at the best conditions match the technical limitations of both EN 14214 and ASTM D-6751 standards.

Electric Vehicles' Controller Area Network (CAN) bus serves as a legacy protocol for in-vehicle network communication. Simplicity, robustness, and suitability for real-time systems are the salient features of CAN bus. Unfortunately, the CAN bus protocol is vulnerable to various cyberattacks due to the lack of a message authentication mechanism in the protocol itself, paving the way for attackers to penetrate the network. This paper proposes a new effective anomaly detection model based on a modified one-class support vector machine in the CAN traffic. The proposed model makes use of an improved algorithm, known as the modified bat algorithm, to find the most accurate structure in the offline training. To evaluate the effectiveness of the proposed method, CAN traffic is logged from an unmodified licensed electric vehicle in normal operation to generate a dataset for each message ID and a corresponding occurrence frequency without any attacks. In addition, to measure the performance and superiority of the proposed method compared to the other two famous CAN bus anomaly detection algorithms such as Isolation Forest and classical one-class support vector machine, we provided Receiver Operating Characteristic (ROC) for each method to quantify the correctly classified windows in the test sets containing attacks. Experimental results indicate that the proposed method achieved the highest rate of True Positive Rate (TPR) and lowest False Positive Rate (FPR) for anomaly detection compared to the other two algorithms. Moreover, in order to show that the proposed method can be applied to other datasets, we used two recent popular public datasets in the scope of CAN bus traffic anomaly detection. Benchmarking with more CAN bus traffic datasets proves the independency of the proposed method from the meaning of each message ID and data field that make the model adaptable with different CAN datasets.

Due to recent advances in wireless gadgets and mobile computing, the location-based services have attracted the attention of computing and telecommunication industries to launch location-based fast and accurate localization systems for tracking, monitoring and navigation. Traditional lateration-based techniques have limitations, such as localization error, and modeling of distance estimates from received signals. Fingerprinting based tracking solutions are also environment dependent. On the other side, machine learning-based techniques are currently attracting industries for developing tracking applications. In this paper we have modeled a machine learning method known as Linear Discriminant Analysis (LDA) for real time dynamic object localization. The experimental results are based on real time trajectories, which validated the effectiveness of our proposed system in terms of accuracy compared to naive Bayes, k-nearest neighbors, a support vector machine and a decision tree.

Abstract Virtual synchronous generator (VSG) control scheme has received much attention from researchers as the introduction of rotational inertia to inverters. However, maintaining power-angle stability during the transient state of low inertia microgrids consisting of VSG based distributed generation units is a critical challenge. According to the equal-area criterion, the accelerating and decelerating area play an important role in power system stabilisation. Therefore, a new control strategy based on the equal-area criterion is proposed in this paper. According to the proposed control technique, the auxiliary inertia is incorporated into the governor unit of VSG with an additional power loop. The auxiliary inertia term minimises the difference between the governor unit of VSG and the governor unit of the conventional synchronous generator (SG). In contrast, the additional power loop supplies the auxiliary power during the transient process only when a significant fault occurs. Moreover, to enhance the transient stability, auxiliary inertia helps to improve the convergence time and dynamic characteristics of VSG, and additional power helps to shorten the acceleration area and widen the deceleration area. MATLAB/Simulink based simulations analysis and results validate the effectiveness of proposed control.

The solar absorption efficiency of water as a base-fluid can be significantly improved by suspending nanoparticles of various materials in it. This experimental work presents the photo thermal performance of water-based nano-fluids of graphene oxide (GO), zinc oxide (ZnO), copper oxide (CuO), and their hybrids under natural solar flux for the first time. Nanofluid samples were prepared by the two-step method and the photothermal performance of these nanofluid samples was conducted under natural solar flux in a particle concentration range from 0.0004 wt % to 0.0012 wt %. The photothermal efficiency of water-based 0.0012 wt % GO nanofluid was 46.6% greater than that of the other nanofluids used. This increased photothermal performance of GO nanofluid was associated with its good stability, high absorptivity, and high thermal conductivity. Thus, pure graphene oxide (GO) based nanofluid is a potential candidate for direct absorption solar collection to be used in different solar thermal energy conversion applications.

Abstract Four types of green alkali modified clinoptilolite (K, Na, Ca, and Mg) were prepared using green tea extracts as novel types of eco-friendly heterogeneous basic catalysts in the transesterification of commercial waste cooking oil into biodiesel. The modified products displayed significant enhancement in the total basicity, surface area, ion exchange capacity, and the morphological properties. The modified samples of K/clinoptilolite (K/Clino), Na/clinoptilolite (Na/Clino), Ca/clinoptilolite (Ca/Clino), and Mg/clinoptilolite (Mg/Clino) showed promising catalytic activities achieving biodiesel yields of 93.6%, 95.2%, 96.4%, and 98.7%, respectively. The best yields were recognized using 4 wt, % as catalysts loading, 16:1 as methanol-to waste oil molar ratio, and at 70 °C as temperature. The best transesterification intervals were identified at 120 min, 120 min, 180 min, and 150 min for K/Clino, Na/Clino, Ca/Clino, and Mg/Clino, respectively. The modified products also demonstrated high reusability properties and the resulted biodiesel in their transesterification systems are of technical properties within the accepted limits of EN 14214 and ASTM D-6751 standards.