ABSTRACT This work is conducted to study the solidification of a liquid undergoing a plane Couette flow between two flat and parallel plates with variable dynamic viscosity over temperature. The flow and thermal characteristics of the circulating liquid during the solidification phase change were predicted by solving analytically the non‐dimensional governing conservation equations of continuity, momentum and energy. The obtained analytical solution expresses the transient dimensionless temperatures of the different phases (solid and liquid), the instantaneous dimensionless solid layer thickness, the dimensionless thickness of the solid layer at the steady state, and the standardized instantaneous power required to maintain the uniform motion of the moving wall. The main parameters affecting the thermal behavior of the problem are then investigated through a parametric study, which reveals that the dimensionless solid layer thickness increases with time and reaches its maximum at the steady‐state regime. For fixed Brinkman number, Br, and dimensionless temperature, , the higher the Biot number, Bi, the higher the dimensionless solid layer thickness. However, increasing the Brinkman, Br, number and dimensionless temperature, , leads to a decrease in the dimensionless solid layer thickness. For 0 < Br ≤ 10, the relative decrease in the solid layer thickness at the steady state for is estimated at 75.53%, 74.92%, and 74.4%, respectively, for Bi = 5, 65.49%, 64.16%, and 62.93% for Bi = 20, and 62%, 60.67%, and 59.26% for the limit case, that is, . When the Brinkman number, Br, and Biot number, Bi, are held constant, increasing the moving wall dimensionless temperature, , leads to a reduction in the required power and therefore in the energy consumed, by as much as about 60%.

ABSTRACT Phase change materials (PCMs) are extensively explored for thermal energy storage (TES) applications. While paraffin wax is the most widely studied organic PCM, non‐paraffinic bio‐based fatty acids offer a more sustainable alternative. This study systematically evaluates seven palm fatty acids: caprylic, capric, lauric, myristic, palmitic, stearic, and oleic acids, focusing on thermal stability, reliability, and metal compatibility, compared with paraffin wax. In addition to standard thermal characterization, a heat absorption‐release test was performed to assess heat storage performance. PCM properties were analyzed before and after two thermal reliability assessments: thermal treatment (up to 700 h) and thermal cycling (up to 350 cycles). Differential scanning calorimetry (DSC) determined phase change temperature, latent heat, and specific heat capacity ( C p ), while thermogravimetric analysis (TGA) and Fourier transform infrared spectroscopy (FTIR) assessed thermal and chemical stability. The palm fatty acids exhibited slight variations in phase change temperature (0.03°C–3.6°C) and moderate melting latent heat reductions (−3.2% to −6.2% after thermal treatment, −7.5% to −13.8% after thermal cycling), comparable to paraffin wax (0.04°C–1.32°C, −7.0%, −10.3%, respectively). Similar to paraffin wax, changes in C p , heat storage performance, TGA, and FTIR results further confirmed the thermal reliability of palm fatty acids. Twelve‐week corrosion tests showed decreasing corrosion rates with time and confirmed the compatibility of all tested PCMs with stainless steel, aluminum, copper, and brass, with most corrosion rates remaining below the critical threshold for long‐term use. Overall, palm fatty acids demonstrate high thermal reliability, stability, and metal compatibility comparable to paraffin wax, establishing them as sustainable bio‐based PCMs for long‐term TES applications.

ABSTRACT The increased penetration of Renewable Energy Sources (RES) into the power system has introduced numerous challenges for grid operators. These challenges are primarily due to highly variable and intermittent production from RES, which depends on weather conditions. This variability in production causes instability and grid reliability issues, affecting overall performances of the grid. One of the most effective mechanisms to address these challenges involves the deployment of Battery Energy Storage Systems (BESS). Their advantages such as fast response, scalability, and geographical independence, make them suitable for supporting RES integration and providing various grid services. Optimal placement, sizing and scheduling control of BESS is an important aspect of their integration into power grids. An optimally planned BESS can improve performances of the grid, and increase its profitability. However, it is a very complex, nonlinear dynamic optimization problem with a large number of constraints, which requires robust optimization techniques to solve efficiently. This paper provides a comprehensive review of optimization methods for optimal planning, that is determining the optimal locations and sizes of BESS in an electric power system. Optimization techniques are classified into four groups, namely conventional, metaheuristic, hybrid and artificial intelligence‐based. Each technique has its advantages and disadvantages, which are highlighted in the paper. Overall, this review provides insights and guidelines that may be useful for selecting an appropriate optimization method for a specific BESS planning problem or for developing a more efficient and robust optimization approach for optimal integration of BESS into modern power grids.

ABSTRACT In recent years, the growth and popularity of electric vehicles (EVs) has soared owing to the facilitation of zero‐emission carbon for people commuting on the road, preserving the environment from air pollution and hazardous gases. However, uncertain EV energy demands and their dynamic arrival times impact the ancillary operations and stability of the charging station (CS). Thus, it becomes a challenging task to schedule EVs for charging with their dynamic charging prices, traveling time, and waiting time efficiently and optimally. Thus, we propose an optimal EV selection scheme for trustworthy charging by implementing the hybrid game theory. The hybrid game theory is bifurcated into stage 1 and stage 2, in which stage 1 includes a coalition game to generate EV clusters or coalitions based on the parameters of state‐of‐charge (SoC), energy demand, and penalty factor. Then, the trust values are determined to select the EV pair fairly. Furthermore, stage 2 highlights the zero‐sum game theory, which aims to optimize the payoff at saddle point and formulate strategies for EV pair (generated in stage 1), ensuring the optimal EV selection for trustworthy charging. Moreover, we have utilized the blockchain network to secure the EV optimal payoff by implementing smart contract in Remix Integrated Development Environment (IDE). The hybrid game theory ensures the optimal and efficient EV selection using coalition game to select EV pair then apply zero‐sum game to optimize the payoff at saddle point condition. Next, we implement the hybrid game theory in Python 3.9 to simulate the results with the help of various factors such as trust value comparison, profit comparison based on strategies, convergence comparison, and profit comparison with the traditional approach.

ABSTRACT [Ag(btt) 2 (NO 3 )] complex was synthesized using 1,2‐benzodithiol‐3‐thione (btt) as a ligand depending on one‐pot synthesis method. FTIR, 1 H‐NMR, elemental analysis, and molar conductivity were used to characterize the silver complex structure. The characterization results prove that btt ligand is attached to the silver center with mono‐dentate behavior through the exocyclic sulfur atom. The silver complex was utilized as a novel precursor for silver nanoparticles using ultrasound method on silver complex powder in 75 mL of deionized water and ultrasonication for 1 h at 90°C using an ultrasonic probe device with a power rating of 150 W. The solution underwent a noticeable color change to blackish‐red. UV–Vis spectrum, XRD pattern, and TEM underscore resulting silver nanoparticles with a diameter range of 47–105 nm, this result from the capping agent effect of btt ligand. The hydrogen storage behavior of [Ag(btt) 2 (NO 3 )] was investigated under different pressures (10–100 bar) at 223 K. The results showed maximum storage of 3.66 wt% at an equilibrium pressure of 88 bar within only 9 s. The kinetic studies were applied on the hydrogen uptake and the results prove that hydrogen storage follows the pseudo‐second‐order kinetic model, as it showed a strong correlation with a value of R 2 = 0.996 and K 2 = 0.117 wt% s −1 .

ABSTRACT Asymmetric hybrid supercapacitors integrating transition metal oxides with carbonaceous electrodes have attracted significant attention for advanced energy storage applications due to their ability to combine high energy density with rapid power delivery. In this study, an Al/Nb 2 O 5 cathode and a Cu/graphene oxide (GO) anode were fabricated via slurry casting and electrophoretic deposition (EPD), respectively, and assembled with a paper separator in aqueous potassium hydroxide (KOH) electrolytes of varying concentrations (1, 2, and 3 M). Structural and morphological analyses confirmed the orthorhombic phase of Nb 2 O 5 and the uniform deposition of GO films. Galvanostatic charge–discharge (GCD) and electrochemical impedance spectroscopy (EIS) measurements revealed a strong dependence of electrochemical performance on electrolyte concentration. The device operating in 2 M KOH exhibited the most favorable balance between energy and power densities, achieving a specific capacitance of 30.7 F g −1 , energy density of 36.5 Wh kg −1 , and power density of 295 W kg −1 , with a relaxation time constant of 0.634 ms. In contrast, 1 M KOH provided moderate energy storage capability, while 3 M KOH suffered from reduced capacitance due to increased viscosity and ion–ion interactions. Comparative analysis with literature data highlights the competitive performance of the Al/Nb 2 O 5 //Cu/GO configuration, particularly in terms of energy–power trade‐off. These findings underscore the critical role of electrolyte optimization and electrode design in advancing hybrid supercapacitors for sustainable energy storage applications.

ABSTRACT Thermal energy storage (TES) systems play a vital role in enhancing energy efficiency and reducing dependence on nonrenewable resources. This study investigates the synergistic integration of triangular fins and nanoparticle‐infused phase change materials (PCMs) to enhance heat transfer in a large triplex tube heat exchanger (TTHX). Numerical simulations, conducted using ANSYS Fluent 15 software, supported by experimental validation with an average deviation of around 2%, were used to evaluate fin placement, fin geometry, and the effect of 10 wt% Al 2 O 3 nanoparticles into the PCM. Results show that triangular fins significantly improve heat transfer, with external fins providing the fastest melting. The addition of nanoparticles increases thermal conductivity by nearly 25% and, when combined with optimized fins, reduces the melting time to 163 min. Energy‐performance analysis confirms that nano‐PCM accelerates charging due to enhanced conductivity, while pure PCM retains higher total stored energy. The optimal configuration, where eight external copper fins of 141 mm length and an 18% aspect ratio, delivered the best overall performance. These findings demonstrate that combining fin‐geometry optimization with nanoparticle enhancement substantially improves TES efficiency. The proposed approach is well‐suited for solar thermal systems, industrial waste‐heat recovery, and compact TES applications.

ABSTRACT Advancements in electrode materials with a high potential window and elevated energy density are essential to meet the growing demands of high‐performance supercapacitors. Ferrites are a promising family of electrode materials. Among them, calcium ferrite (CaFe 2 O 4 ) has excellent structural stability. However, the low specific capacitance and high agglomeration rate of CaFe 2 O 4 limit its applications. The addition of carbonaceous material to the ferrite host matrix is expected to modify the supercapacitor electrode characteristics. CaFe 2 O 4 has not been explored yet as a composite of CNTs. In this work, robust (CaFe 2 O 4 ) 1‐x (CNTs) x nanocomposites are synthesized through a simple sol–gel method via an ex‐situ approach with extraordinary electrochemical properties. The prepared nanocomposites have unambiguously shown a polycrystalline nature, defective vibrational bonding, and a tuned band gap towards the low‐frequency region due to the formation of heterojunctions, confirmed through XRD, FTIR, XPS, UV, and PL. The electrochemical studies reveal that the (CaFe 2 O 4 ) 0.8 (CNTs) 0.2 nanocomposites have the highest specific capacitance of 530.54 Fg −1 at 0.5 Ag −1 with the lowest ohmic and solution resistance, along with remarkable cyclic stability and columbic efficiency, making them an efficient electrode material.

ABSTRACT This study investigated metal‐free organic dyes having D‐π‐A and D‐A′‐π‐A frameworks for organic solar cells (OSCs). The influence of modifying the donor and internal acceptor in reference molecules ( N , O , and S ) on the structural, electronic, photovoltaic, and optical characteristics was analyzed by employing density functional theory (DFT). The UV–visible spectrum of the designed dyes was also simulated by employing time‐dependent DFT (TD‐DFT). The highest occupied molecular orbital (HOMO), lowest unoccupied molecular orbital (LUMO), and their energy gap (E gap ) are advantageous to understand the electron injection, electron transfer, and regeneration of the dye. The evaluated results suggest that short‐circuit current density (J SC ), energy for dye regeneration (ΔG reg ), electron injection driving force (ΔG inj ), light harvesting efficiency (LHE), open circuit voltage (V OC ), density of state (DOS), and power conversion efficiency (η) are affected by the insertion of donors and internal acceptors. The dye N with Carbazole donor has an efficacy of 4.15% at J SC of 15 mA cm −2 . The outcomes indicate that heteroatom‐doped donors and inserting internal acceptors have an impact on absorption energies and improve the photovoltaic characteristics in the D‐π‐A arrangement, suggesting that these dyes are better sensitizers for the assembly of OSCs.

ABSTRACT The increasing global population and rapid depletion of energy resources have intensified the demand for renewable energy and advanced energy storage solutions. Supercapacitors, with their high power density, long cycle life, and fast charging capability, are emerging as a promising alternative to conventional batteries. This study reports, for the first time, the capacitive performance of a bimetallic FeNi metal‐organic framework (MOF) combined with multi‐walled carbon nanotubes (MWCNTs) on a carbon felt electrode. The composite was synthesized via a hydrothermal route and applied through a drop‐casting method. Electrochemical performance was evaluated using cyclic voltammetry, electrochemical impedance spectroscopy, and galvanostatic charge–discharge techniques. The resulting electrode demonstrated a specific capacitance of about 180 F/g over a wide current density range, nearly 100% coulombic efficiency, a power density up to 3600 W/kg, and an energy density of about 91 Wh/kg. Moreover, it retained 90% of its capacity after 700 charge–discharge cycles, underscoring its stability. These findings highlight the FeNi MOF‐MWCNT composite as a promising candidate for high‐performance supercapacitor electrodes.