University of Skikda

Advancements in energy storage systems (ESS) are important to attaining a sustainable and resilient energy future. Despite significant advancements in battery technologies, including lithium-ion, sodium-ion, and redox flow batteries, numerous problems remain. These include low energy density, thermal instability, resource scarcity, high lifecycle costs, and ineffective recycling methods. Furthermore, the complexity of connecting battery systems to the grid while maintaining operational safety creates further impediments to implementation. Recent advancements, such as hybrid energy storage systems (HESS), better battery chemistries, and intelligent modeling tools based on MATLAB/Simulink R2025b, have shown promise in terms of performance, cost reduction, and more effective energy management. However, the scalability, recyclability, and real-world applicability of these systems require further exploration. The goal here is to provide a comprehensive overview of current and emerging battery technologies, focusing on technical performance, environmental sustainability, lifecycle cost modeling, and grid compatibility. This comprises a techno-economic study that employs process-based cost modeling (PBCM) and leveled cost of storage (LCOS), a thorough examination of green battery chemistries, and system-level modeling of battery and hybrid configurations. The study seeks to provide academics and stakeholders with a comprehensive framework that considers both the innovations and limitations of current ESS technologies in the context of global decarbonization targets.

Accurate evaluation of soil mechanical behavior remains a cornerstone of reliable geotechnical engineering and optimized foundation design. Among the key parameters that define soil deformability, the pressuremeter modulus (Ep) plays a crucial role in assessing the ground response and structural stability. However, conventional approaches for determining Ep through empirical correlations or in situ measurements are often labor intensive, costly, and subject to significant uncertainty. These limitations underscore the necessity for advanced predictive frameworks that can provide both accuracy and efficiency in geotechnical characterization. In the present work, response surface methodology (RSM) is applied as an advanced statistical modeling and optimization technique to improve the predictive capability of the pressuremeter modulus. The experimental investigation is structured via a central composite design (L35) framework, enabling the systematic evaluation of nonlinear interactions among the principal geotechnical variables, namely, depth (D), cohesion (C), internal friction angle (φ), and unit weight (γ). The developed model was rigorously validated through analysis of variance, which revealed a high level of statistical significance with an excellent coefficient of determination (R2 = 96.50

Porous gas bearings (PGBs) enable high-speed, oil-free operation in modern rotating machinery. This study develops a coupled thermo-hydrodynamic (THD) model for a cylindrical porous gas bearing lubricated with four working fluids-air, R-134a, helium and hydrogen. The modified Reynolds equation is derived by combining the Navier-Stokes and continuity equations with the Morgan-Cameron approximation, Darcy-Forchheimer law and Beavers-Joseph slip condition. Gas compressibility and vapour-liquid transition are represented through the Peng-Robinson equation of state. Steady-state and dynamic analyses are performed to evaluate the influence of permeability and slip on load capacity, pressure distribution, flow rate, friction torque, temperature field and stiffness and damping coefficients. Results show that increasing permeability decreases pressure and load capacity but promotes better thermal uniformity, whilst higher slip coefficients improve film stability and reduce shear losses. Amongst the gases considered, hydrogen exhibits the lowest film thickness due to its low viscosity, whereas helium yields superior thermal behaviour. The combined model provides a reliable computational framework for optimising porous gas bearings under realistic operating conditions.

In this work, melting characteristics and heat transfer enhancement of gallium as phase change material (PCM) surrounded by heterogeneous chamber filled with metal foam and Al2O3 nanoparticles under magnetic field are investigated. The main challenge rather is the low thermal conductivity of PCMs which in turn limits the performance of PCM based TESSs. Numerical simulations were performed using a 2D transient model developed by employing the enthalpy-porosity model and Darcy–Brinkman equations for the porous domain; where one of the boundary walls was kept at a heated temperature of 43 °C. It is found that the incorporation of metallic foam and nanoparticles greatly enhances both thermal conductivity and facilitates uniform melt. In addition, the magnetic field promotes such convective heat transfer, speeds up the melting rate, and raises the mean Nusselt number and surface heat flux. These results indicate that the integration of metal foams and nano/micro particles, and magnetic fields could be used to maximize the thermal performance of PCMs, which can lead to advanced TES applications with a high potential.

This study presents the effect of gamma rays of up to 2000 kGy on the chemical structure and the physical properties of a poly(butylene adipate-co-terephthalate) (PBAT) with 48% mol of terephthalic units. PBAT is a polymer with properties similar to polyethylene (PE) but it is biodegradable and not toxic to the environment, and it can be prepared with a renewable content of up to 68.6% weight, with uses in biomedicine and packaging. Previous studies found in the literature have been conducted using low doses and the results were contradictory. The results for gel content and crosslinking efficiency were in agreement with the results found in the literature. Molecular weight decreased and widened with the increase in dose. Proton NMR analysis was used for the first time in PBAT to determine the changes in chemical species, the formation of new chemical species, and the bonds more susceptible to be broken by gamma rays. Both thermal and mechanical properties were explained by the scission of the chains in the amorphous phase and at the boundaries of the crystallites. The thermal parameters most affected by irradiation were the crystallization temperature and temperature of melting after cooling from the melt. Stress and strain at break suffered a continuous decrease with dose until PBAT became fragile at high dose.