Output feedback control of supercapacitors parallel charging system for EV applications: Theoretical design and experimental validation

In this paper, the problem of controlling parallel charging system with supercapacitors for electric vehicle applications is considered. When the vehicle parks at the station, the charging process of supercapacitors needs to be completed in less than 30 seconds. The control objective is then to tightly regulate the supercapacitors state of charge (SOC) to a given reference constant and to ensure an adequate current sharing between different parallel chargers. Indeed, the current sharing is a critical issue for parallel charging system with supercapacitors, which is a nonlinear system with control inputs constraints. Besides, the SOC depends on the supercapacitors internal voltage, which is not accessible for measurement. Therefore, based on a large‐signal model of the parallel‐chargers‐supercapacitors system, an output feedback controller (combining a state observer and a nonlinear control laws) is designed. The controller is formally shown to meet all objectives, namely, closed‐loop stability, SOC reference tracking, and equal current sharing. The effectiveness of the proposed output feedback controller approach is verified both by simulation and by experimental tests.     

XRD evidence of macroscopic composition inhomogeneities in the graphite–lithium electrode

In situ and ex situ X-ray diffraction (XRD) measurements were carried out on lithiated graphite electrodes at different states of charge. Data were collected from both sides of electrode. We found macroscopic inhomogeneities in the lithium concentration along the electrode thickness even when the electrode was allowed to rest for 24 h. The electrode side facing the lithium counter electrode in the coin type half-cell displays higher lithium concentration as compared to the side opposed to the XRD window. Residual stage 2 compound is found in the supposedly fully lithiated and fully delithiated electrode. It seems that the differences in the chemical potential between stage 2 and stage 1 is too small to average the lithium composition through chemical diffusion at ambient temperature in reasonable times.     

Algerian Sahara Sand Dunes Characterization

For a possible use of Saharan sands, representative samples were collected and analysed by several physicochemical methods. The results show that quartz (98 %) is the most represented mineral, while the oxides of aluminium, potassium, iron, chromium and manganese probably are included in a clay phase. The granular analysis enabled the determination of uniformity coefficient (CU) and equivalent diameter. On the other hand, a comparison of the Infrared spectrum of the sand (washed and unwashed) was carried out as well as Scanning Electron Microscopy observations and X-Ray analysis.     

Mixed convection and entropy production of a hybrid nanofluid in a porous cylindrical enclosure with rotating top wall

A numerical study is carried out to investigate heat transfer and entropy production of a hybrid nanofluid in a porous cylindrical enclosure with a rotating top wall. The bottom wall of the cylinder is taken as hot, the sidewall is adiabatic, except the top wall is considered cold and rotates at an angular velocity (ΩR). The effects of a hybrid nanofluid flow on heat transfer and entropy generation are examined for an aspect ratio (H/R = 1). A FORTRAN program was elaborated for solving the governing equations based on the finite volume method. Good agreement was found when comparing results from this study against published data. Our results are presented for different Reynolds number values (100 ≤ Re ≤ 1500), nanoparticle fraction NP (0 ≤ ϕ ≤ 0.08), Darcy number (10⁻⁴ ≤ Da ≤ 10⁻¹) and porosity of the porous medium (0.2 ≤ ε ≤ 0.99) for Ri = 0.5, 1,5 and 8, where (Ri = Gr/Re2). They reveal that the heat transfer increases with Re, ϕ, Da, Ri, and decreasing ε. The simulation data were used to propose four different correlations for $\overline{\mathit{Nu}}$ and S_tot as Re, Da, Ri, ϕ, and ε.     

Numerical study on the effects of the macropatterned active surfaces on the wall-coated steam methane reformer performances

This paper deals with a numerical study on the steam methane reforming reaction performances into a wall-coated steam methane reformer (WC-SMR), intended to produce hydrogen. In this work a new catalytic pattern, purporting to enhance the WC-SMR efficiency, is proposed. A comparison study is made between the new inter-catalytic layers pattern and a conventional one with a continuous catalytic layer pattern. Both WC-SMR models operate at similar conditions and at the same design parameters, except the catalytic zone length which is monitored by taking into account the inter-catalytic layers spacing or not. Our results show that, by adopting a catalytic surface with an inter-catalytic spacing, the methane conversion could be enhanced and thus the hydrogen production is intensified.     

Multivariable fractional system approximation with initial conditions using integral state space representation

In this paper, we consider the approximation of general multivariable non commensurate fractional systems by integer order state space models. This work contains two main contributions. First, a new state space representation using the fractional integral operator is introduced. Second, the approximate model carries explicitly the initial conditions of the system. Two examples are given to illustrate the accuracy of the approximation.     

An integrated agro-ecosystem and livelihood systems approach for the poor and vulnerable in dry areas

More than 400 million people in the developing world depend on dryland agriculture for their livelihoods. Dryland agriculture involves a complex combination of productive components: staple crops, vegetables, livestock, trees and fish interacting principally with rangeland, cultivated areas and watercourses. Managing risk and enhancing productivity through diversification and sustainable intensification is critical to securing and improving rural livelihoods. The main biophysical constraints are natural resource limitations and degradation, particularly water scarcity and encroaching desertification. Social and economic limitations, such as poor access to markets and inputs, weak governance and lack of information about alternative production technologies also limit the options available to farmers. Past efforts to address these constraints by focusing on individual components have either not been successful or are now facing a declining rate of impact, indicating the need for new integrated approaches to research for development of dryland systems. This article outlines the characteristics of such an approach, integrating agro-ecosystem and livelihoods approaches and presents a range of empirical examples of its application in dryland contexts. The authors draw attention to new insights about the design of research required to accelerate impact by integrating across disciplines and scales.     

Synthesis and Characterization of Novel Surfactants: Combination Products of Fatty Acids,Hydroxycarboxylic Acids and Alcohols

The reaction of hydroxycarboxylic acids, such as citric, malic and tartaric species with an excess of fatty acid chlorides produces the corresponding O-acylated hydroxycarboxylic anhydrides in one step and in a near quantitative yield. These molecules are excellent electrophiles which react readily with a variety of nucleophiles including alcohols, diols and polyols. Their reaction with triethylene glycol and triethylene glycol monomethyl ether leads to two series of novel anionic surfactants, which are unsymmetrical gemini surfactants. The determination of their properties (CMC, foaming, HLB) revealed that these molecules are—depending on the chain length of the fatty acid—excellent emulsifiers, and that they also display interesting antimicrobial activity. These novel functional surfactants are of interest for applications in food and personal care products and for the formulation of pharmaceuticals.     

Sustainability of a wind power plant: Application to different Moroccan sites

In this paper, three main steps allowing the definition of the sustainability of a wind power plant (WPP) are described in detail. The first step is to choose a site with a good wind potential. In this respect, two approaches have been introduced: traditional wind statistical estimations based on the identification of the Weibull probability density function on specific sites; and an innovative Kriging approach based on artificial neural networks to reconstruct the profile of the mean wind speed of the territory. In the second step, given technical details, the energetic sustainability of a WPP installation is assessed according to a model computing the wind energy production per year, as well as the details of its efficiency. Finally, as third step, a cost/benefit evaluation on the overall reduction in CO₂ emissions with respect to traditional fossil fuel energy plants is reported. From a wind speed characterisation viewpoint, the case study is referred to the overall Moroccan territory. From a WPP model viewpoint, the case study is referred to the installation of a specific WPP, which would allow the production of more than 2 GWh per year in the south Atlantic coast and of nearly 1 GWh per year in the Mediterranean coast in the neighbourhood of Tangier.