Fédération de Recherche FCLAB

The TiMn1.5 intermetallic alloy in powder form is a good medium for the reversible storage of hydrogen in a solid form. Since the 1980s, it has been known that optimizing its storage properties requires time-consuming and costly annealing at 1100 °C for 20 h. However, the effects induced by heat treatment and the link between micro modification and macro functional properties are still not clearly established. The present work aims at bringing insights on the changes at the micro scale which can explain the observed improvement of hydrogen storage properties (capacity from 1.42 wt %H to 1.75 wt %H, lower transformation pressure and flattening of PCI plateau). The particles morphology and size, the phase-structural composition and microstructure were characterized by SEM microscopy, EDS and XRD techniques before and after annealing. During the treatment, the particles’ morphology drastically changes, gradually forming foamy, “coral-like” particles from grounded faceted particles, increasing the active surface. Inside the faceted particles, we observe a counterintuitive increase of the amount of the TiMnα phase, known to poorly desorb hydrogen but acting as a catalyst during the absorption process. EDS shows a Mn-enrichment of the Laves phase, while crystal lattice broadening measured by XRD is very slight. The Rietveld refinement on the still predominant C14 phase shows that the lattice strain decreases from 2.03 × 10–3 to 8.3 × 10–4 highlighting a relaxation phenomenon. Based on these observations, we conclude that the combination of these phenomena plays an essential role in the improvement of the storage capacity and pressure during the annealing process.

Deploying Proton Exchange Membrane Fuel Cells (PEMFC) in heavy-duty vehicles to achieve zero greenhouse gas emissions requires individual components and assembled stacks to have exceptionally long lifespans, up to 30,000 hours. Therefore, test and analysis methods must be developed to accurately simulate real-world operating conditions while significantly accelerating the aging process for components and stacks. Within this context, a method to monitor two of the most critical internal states of the PEMFC, Electrochemical Surface Area and PEM thickness, based on sequential polarization (I-V) curves is proposed. Moreover, a process is used to deduce the I-V curves from dynamic data to avoid losing durability information and/or accurately determining the characterization intervals.

Yttrium-doped barium zirconate is a commonly used electrolyte material for Protonic Ceramic Fuel Cells (PCFC) due to its high protonic conductivity and high chemical stability. However, it is also known for its poor sinterability and poor grain boundary conductivity. In this work, in response to these issues, reactive magnetron sputtering was strategically chosen as the electrolyte deposition technique. This method allows the creation of a 4 µm tick electrolyte with a dense columnar microstructure. Notably, this technique is not widely utilized in PCFC fabrication. In this study, a complete cell is elaborated without exceeding a sintering temperature of 1350 °C. Tape casting is used for the anode, and spray coating is used for the cathode. The material of interest is yttrium-doped barium zirconate with the formula BaZr0.8Y0.2O3−δ (BZY). The anode consists of a NiO-BZY cermet, while the cathode is composed of BZY and Ba0.5Sr0.5Co0.8Fe0.2O3−δ (BSFC) in a 50:50 weight ratio. The electrochemical impedance spectroscopy analysis reveals a global polarization resistance of 0.3 Ω cm2, indicating highly efficient interfaces between electrolytes and electrodes.

By offering promising solutions to two critical issues – the integration of renewable energies into energy systems and the decarbonization of existing hydrogen applications – green hydrogen production through water electrolysis is set to play a crucial role in addressing the major challenges of the energy transition. However, the successful integration of renewable energy sources relies on gaining accurate insights into the impacts that intermittent electrical supply conditions induce on electrolyzers. Despite the rising importance of addressing intermittency issues to accelerate the widespread adoption of renewable energy sources, the state-of-the-art lacks research providing an in-depth understanding of these concerns. This paper endeavors to offer a comprehensive review of existing research, focusing on proton exchange membrane (PEM) and alkaline electrolysis technologies operating under intermittent operation. Despite growing interest over the last ten years, the review underscores the scarcity of industrial-scale databases for quantifying these impacts.

Matching between low-voltage high-current capacity battery/fuel cell with high-voltage lowcurrent motors in electric vehicles (EVs) requires paralleling-connection multi-stage power electronic converter with accurate modeling and control system. For high-voltage low-current drives of EVs with high-boosting/bucking gain, single-stage single-arm DC/DC converters suffer from unstable output voltage and the impractical choice of charging/discharging elements. Therefore, a multi-stage multi-arm DC/DC converter is researched to solve the problems of high boosting/bucking gain and minimized the voltage and current ripples. This paper presents parametric sizing, dynamic modeling, and analysis of all logical operational modes for a new high-gain DC/DC converter suitable for deployment in EV applications. The proposed topology composes of three-stage interleaved-input composed of cascaded two stages and double float-output as a third stage with bidirectional current capability. In this study, parametric design, and sizing for the three stages are performed according to the prerequisite ratings. Then, an analysis is conducted on rules of operating the DC/DC converter along with a discussion on considerations taken into account for such a critical design. An investigation of the dynamic behavior of the suggested DC/DC converter is carried out through a state-space model with switches' states. Furthermore, a simulation and measurement-based validation of the derived mathematical models are conducted. The theoretical based analysis, design, and boosting gains are confirmed through a constructed and tested prototype given data on power supply and load utilization. A discussion on the choice of semiconductor equipment and reactive elements is provided for the proposed DC/DC converter. The experimental results show that the three stages can be used in a separate mode or in a cascaded booster. DC-DC converters, double float-output converter, battery pack, voltage regulation, electric vehicles, interleaved boost converter. The associate editor coordinating the review of this manuscript and approving it for publication was Yuh-Shyan Hwang . NOMENCLATURE DC/DC Direct current/direct current. D Duty ratio. EV Electric vehicles.

A dual loop multivariable coordinated management (DLMCM) is proposed in this article dealing with the existed nonlinearity and strong coupling between operating parameters such as stack temperature and oxygen excess ratio, to achieve net power enhancement of proton exchange membrane fuel cell (PEMFC) system. The proposed optimization method includes: 1) outer net power optimization loop and 2) inner data-driven multivariable control loop. In solving the outer net power optimization, the experimental data based net power smooth surface model and the security constraints are proposed for maximum net power regulator design. Regarding inner data-driven multivariable control loop, first, pseudopartial derivative linearization (PPDL) is proposed for online modeling and estimation of the multi-input and multi-output system. Then, PPDL-based discrete adaptive integral terminal sliding mode control is proposed to achieve maximum net power trajectory tracking. Experimental tests carried out on 5-kW PEMFC system show that the proposed DLMCM has better tracking ability, and internal disturbance rejection compared with sliding mode control. Moreover, the comparative study with manual guided control, temperature control, and air flow control testifies the effectiveness of proposed DLMCM for net power enhancement with a low level of parasitic power consumption ratio.

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Nowadays, electric and hybrid vehicle technology has known large use in the world. This technology allows improving the main performances of conventional vehicles. In this research work, modeling and dynamic simulation of BMW-I3 electric vehicle based on Matlab/Simulink are developed. The dynamic simulation proposed is based on a forward approach. To simulate the electric vehicle model, different scenarios have been proposed. Specific parameters are defined to characterize each scenario. These parameters are sampling step, acceleration, and maximum speed. The developed vehicle simulator uses a specific scenario and feedback of the actual speed to generate desired outputs. The desired outputs of the simulation are acceleration-deceleration command, brake control and consumption rate of the vehicle. In this paper, two different cases of study have been considered taking into account a braking option. Integration of this option in the vehicle model allows recuperation of a significant quantity of energy. The recuperated quantity is estimated at around 25 percent. The obtained results show that the proposed approach ensures high quality of control.