Search Results (114)

An analysis of entropy generation and a performance comparison are carried out for a solid oxide fuel cell with an embedded porous pipe in the air supply channel of a mono-block-layer-build geometry (MOLB-PPA SOFC) and a planar geometry with trapezoidal baffles inside the fuel and air channels (P-TBFA SOFC). The results for power density at different current densities are discussed. Also, a comparison of the field of species concentration, temperature, and current density on the electrode–electrolyte interface is analyzed at a defined power density. Finally, a comparison of maps of the local entropy generation rate and the global entropy generation due to heat transfer, fluid flow, mass transfer, activation loss, and ohmic loss are studied. The results show that the MOLB-PPA SOFC reaches a 7.5% higher power density than the P-TBFA SOFC. Furthermore, the P-TBFA SOFC has a more homogeneous temperature distribution than the MOLB-type SOFC. The entropy generation analysis indicates that the MOLB-PPA SOFC exhibits lower global entropy generation due to heat transfer compared to the P-TBFA SOFC. The entropy generation due to ohmic losses is predominant for both geometries. Finally, the total irreversibilities are 24.75% higher in the P-TBFA SOFC than in the MOLB-PPA SOFC. Full article

Electrochemical separations use an ionic current to drive the flow of ions across an ion exchange membrane to produce dilute and concentrated streams. The economics of these systems is challenging because passing an ionic current through a dilute solution often requires a small cell gap to lower the ionic resistance and the use of a low current density to minimize the voltage drop across the dilute product stream. Lower salt concentration in the product stream improves the fraction of the salt recovered but increases the electricity cost due to high ohmic losses. The electricity cost is managed by lowering the current density which greatly increases the balance of the plant. The cell configuration demonstrated in this study eliminates the need to pass an ionic current through the diluted product stream. Ionic current passes only through the concentrated product stream, which allows use of high current density and smaller balance of the plant. The cell has three chambers with an anion and cation membrane separating the cathode and anode, respectively, from the concentrated product solution. The device uses zero-gap membrane electrode assemblies to improve the cell voltage and system performance. As ions concentrate in the center compartment, the solution resistance decreases, and the product is recovered with a lower voltage penalty compared to traditional electrodialysis. This lower voltage drop allows for faster feed flow rates and higher current density. Additionally, the larger cell gap for the product provides opportunities for systems with solids suspended in solution. It was found that the ion collection efficiency increased with current due to enhanced convective mass transfer in the feed streams. Full article

Fresh-cut potatoes are highly perishable, requiring effective preservation strategies to maintain quality and extend shelf life. This study evaluated the use of edible coatings and the combination of osmotic dehydration and ohmic heating (OH-OD), both integrated with modified atmosphere packaging (MAP), to enhance microbial stability and reduce quality deterioration. Key quality parameters—including color stability, browning index, weight loss, microbial activity, and sensory attributes—were assessed. Results showed that coated samples (E-FP) had the lowest browning index (59.71) by day 8, compared to a value of 62.69 in control samples (C-FP). OH-OD-treated samples exhibited the least weight loss (6.73%) versus 17.75% in C-FP. Microbial analysis showed that E-FP samples maintained the lowest total viable count by day 8 (3.98 ± 0.02 log CFU/g), compared to OH-OD-FP (4.43 ± 0.13 log CFU/g) and C-FP (4.79 ± 0.06 log CFU/g), confirming the antimicrobial efficacy of the edible coating enriched with rosemary essential oil and ascorbic acid. Sensory evaluation further confirmed that coated samples retained superior sensory qualities, receiving the highest overall acceptance score of 8.86 ± 0.80, compared to values of 7.80 ± 0.98 for control samples (C-FP) and 2.80 ± 0.69 for OH-OD-FP samples, highlighting their enhanced consumer appeal. These findings highlight that combining advanced preservation techniques with MAP can significantly reduce moisture loss and microbial spoilage while maintaining freshness and sensory appeal. This integrated approach offers a promising solution for extending shelf life, reducing food waste, and supporting sustainability in response to consumer demand for minimally processed, high-quality fresh products. Full article

Anion exchange membrane electrolyzer (AEMEC) is a promising hydrogen production technology device. An electrochemical model is developed using MATLAB/Simulink to analyze the impact of factors such as anion exchange membrane (AEM) thickness, operating temperature, pressure, and gas diffusion layer (GDL) parameters including GDL thickness, porosity, and pore size. The results showed that as the thickness of AEM, operating pressure, and GDL decreased, the electrolysis efficiency significantly improved, and energy consumption decreased. When the thickness of AEM decreases from 70 microns to 65 microns, it will cause a decrease of 24 mV in cell voltage. This study also found that increasing pressure slightly increases voltage due to higher diffusion overpotential. In addition, changes in GDL porosity and pore size have a significant impact on performance. The lower porosity reduces ohmic loss and improves efficiency. This study highlights the importance of optimizing the design of AEMEC components to improve hydrogen production performance. Full article

Highly (0002)-oriented Al_1−xSc_xN thin films with different Sc doping concentrations (x = 0, 0.2, 0.25, 0.3, and 0.43) were prepared via a magnetron sputtering system. The effects of Sc doping on the crystal structure and electrical property of the as-prepared thin films were investigated experimentally. The results of synchrotron radiation grazing-incidence wide-angle X-ray scattering (GIWAXS) and X-ray diffraction (XRD) demonstrated that the Sc³⁺ substitution for Al³⁺ induced asymmetric lattice distortion: the a-axis exhibited monotonic expansion (reaching 3.46 Å at x = 0.43) due to the larger atomic radius of Sc (~0.87 Å), while the c-axis attained a maximum value of 5.14 Å at x = 0.2 and subsequently contracted as the bond angle reduction became dominant. The dielectric constant increased to 34.67 (225% enhancement) at x = 0.43, attributed to the enhanced polarization of Sc-N bonds and interfacial charge accumulation effects. Simultaneously, the dielectric loss increased from 0.15% (x = 0) to 6.7% (x = 0.43). Leakage current studies revealed that high Sc doping (x = 0.43) elevated the leakage current density to 10⁻⁶ A/cm² under an electric field of 0.2 MV/cm, accompanied by a transition from Ohmic conduction to space-charge-limited current (SCLC) at a low electric field strength (<0.072 MV/cm). Full article

Accurate real-time temperature measurement under extreme thermal-pressure conditions remains challenging in aerospace. Sapphire fiber Bragg gratings (FBGs), exhibiting temperature measurement capabilities up to 1900 °C, demonstrate suitability for such extreme environments. However, the development of a high-performance demodulation system capable of processing sapphire FBG signals over wide spectral ranges at elevated speeds remains a technical challenge. This study presents a real-time FBG signal demodulation system that incorporates an all-dielectric subwavelength grating edge filter. The designed grating, comprising a TiO₂/Si₃N₄ subwavelength unit array, modulates Mie-type electric and magnetic multipole resonances to achieve precisely tailored transmission and reflection spectra. Simulation results indicate that the grating exhibits low ohmic loss, excellent linearity, complementary transmission/reflection characteristics, a wide linear range, and angular-dependent tunability. The designed edge-filter-based demodulation system incorporates dual single-point detectors to simultaneously monitor the transmitted and reflected signals. Leveraging the functional relationship between the center wavelength of the FBG and the detected signals, this system enables high-speed, wide-range interrogation of the center wavelength, thus facilitating real-time demodulation for wide-range temperature sensing. The proposed method and system are validated through theoretical modeling, offering an innovative approach for sapphire FBG signal demodulation under extreme thermal-pressure conditions. Full article

Mechanically improved polymeric membranes with high ionic conductivity (IC) and good permeability are highly desired for next-generation anion exchange membranes (AEMs) in order to reduce Ohmic losses and enhance water management in alkaline membrane fuel cells. To move towards the fabrication of such high-performance membranes, the creation of hydrophilic ion-conducting double gyroid (DG) nanochannels within block copolymer (BCP) AEMs is a promising approach. However, this attractive solution remains difficult to implement due to the complexity of constructing a well-developed ion-conducting DG morphology across the entire membrane thickness. To deal with this issue, water permeable polystyrene-block-poly(2-vinylpyridine)-block-poly(ethylene oxide) membranes with ion-conducting DG nanochannels were produced by combining a solvent vapor annealing (SVA) treatment with a methylation process. Here, the SVA treatment enabled the manufacture of DG-forming BCP AEMs while the methylation process allowed for the conversion of pyridine sites to N-methylpyridinium (NMP⁺) cations via a Menshutkin reaction. Following this SVA-methylation method, the IC value of water-permeable (~384 L h⁻¹ m⁻² bar⁻¹) DG-structured BCP AEMs in their OH⁻counter anion form was measured to be of ~2.8 mS.cm⁻¹ at 20 °C while a lower IC value was probed, under the same experimental conditions, from as-cast NMP⁺-containing analogs with a non-permeable disordered phase (~1.2 mS.cm⁻¹). Full article

Potential-induced degradation (PID) presents a critical reliability issue for solar photovoltaic (PV) modules, with three primary types identified in the literature, namely, PID_s (shunting type), PID_p (polarization type), and PID_c (corrosion type). Electrochemical/electrical impedance spectroscopy (EIS) is a highly effective but underutilized technique for differentiating between these PID mechanisms. When used alongside conventional I–V measurements (e.g., I_sc, V_oc, and FF), EIS offers direct insights into parameters such as R_s, R_p, and C_p, making it a valuable tool for PID type differentiation. In this study, two four-cell glass–glass modules were investigated using p-base PERC monofacial cells with EVA and POE encapsulants. Results indicate that V_oc and FF remained nearly unchanged under +1000 V stress for both EVA and POE modules, suggesting a minimal impact of PID stress on these parameters. However, I_sc was reduced by approximately 8.5% in the EVA module and 10% in the POE module. For the POE module, surface recombination (PID_p) is likely responsible for the I_sc loss, as R_s, R_p, and C_p showed no significant variation. Conversely, in the EVA module, the combined effects of surface recombination and junction recombination (PID_jr) are the probable cause of the I_sc loss, as evidenced by remarkable changes in R_p and C_p. The observed decrease in R_p for the EVA module is attributed to reduced dynamic diode resistance rather than ohmic shunt resistance. This reduction is linked to recombination currents induced by junction trap centers, formed by the positive voltage PID stress in the encapsulant, which contains trace amounts of oxidizable species such as CH₃COOH and/or H₂O. The objective of this study is to evaluate the impact of PID stress on the electrical characteristics of glass–glass PV modules with different encapsulants, utilizing a combined EIS and I–V approach to distinguish between PID mechanisms. The findings highlight the critical role of the encapsulant type in determining PID susceptibility, with the EVA module exhibiting significant degradation linked to junction recombination losses. These insights underscore the necessity of optimizing encapsulant materials to enhance PV module durability and reliability in real-world applications. Full article

The accurate estimation of lithium-ion cell internal temperature is crucial for the safe operation of battery packs, especially during high discharge rates, as operating outside the safe temperature range can lead to accelerated degradation or catastrophic failures. Heat generation in lithium-ion cells arises primarily from ohmic losses and entropy change ($\Delta S$), yet the latter remains frequently overlooked in battery modelling. However, the impact of considering or discarding $\Delta S$ from electro-thermal modelling remains subject to debate. This research highlights the critical role of $\Delta S$ in improving the accuracy of electro-thermal models for lithium-ion batteries, particularly in high-fidelity thermal simulations. It presents a systematic integration, $\Delta S$, into electro-thermal models, leveraging the energetic macroscopic representation (EMR) approach to enhance predictive accuracy, a methodology not previously structured in this manner. This paper addresses this issue by performing a comparative analysis of an electro-thermal model (ETM) with and without $\Delta S$. The findings provide clear insights into the role of entropy in electro-thermal modelling, demonstrating that while entropy change has a minimal impact on electrical behaviour prediction, it plays a crucial role in accurately capturing temperature dynamics, helping define the conditions under which it must be considered in simulations. While entropy can be neglected for coarse heat generation estimation, its inclusion enhances temperature prediction accuracy by up to 4 °C, making it essential for applications requiring precise thermal management. This study offers a detailed analysis of the conditions under which $\Delta S$ becomes critical to model accuracy, providing actionable guidance for battery engineers and researchers. Full article

Optimal product synthesis in bioelectrochemical systems (BESs) requires a comprehensive understanding of the relationship between external voltage and microbial yield. While most studies assume constant growth yields or rely on empirical estimates, this study presents a novel thermodynamic model, linking anodic oxidation and cathodic carbon dioxide (${CO}_2$) reduction to methane (${CH}_4$) by growing microbial biofilm. Through integrating theoretical Gibbs free energy calculations, the model predicts electron and proton transfers for autotrophic methanogen and anode-respiring bacteria (ARB) growth, accounting for varying applied voltages and substrate concentrations. The findings identify an optimal applied cathodic potential of −0.3 V vs. the standard hydrogen electrode (SHE) for maximizing ${CH}_4$ production under standard conditions (pH 7, 25 °C, 1 atm) regardless of ohmic losses. The model bridges the stoichiometry of anodic and cathodic biofilms, addressing research gaps in simulating anodic and cathodic biofilm growth simultaneously. Additionally, sensitivity analyses reveal that lower substrate concentrations require more negative voltages than standard condition to stimulate microbial growth. The model was validated using experimental data, demonstrating reasonable predictions of biomass growth and ${CH}_4$ yield under different operating voltages in a multi substrate system. The results show that higher voltage inputs increase biomass yield while reducing ${CH}_4$ output due to non-optimal voltage. This validated model provides a tool for optimizing BES performance to enhance ${CH}_4$ recovery and biofilm stability. These insights contribute to finding optimum voltage for the highest ${CH}_4$ production for energy efficient ${CO}_2$ reduction for scaling up BES technology. Full article

This study examines the impact of incorporating obstacles in the electrode structure of an organic redox flow battery with a flow-through configuration. Two configurations were compared: A control case without obstacles (Case 1) and a modified design with obstacles to enhance mass transport and uniformity (Case 2). While Case 1 exhibited marginally higher discharge voltages (average difference of 0.18%) due to reduced hydraulic resistance and lower Ohmic losses, Case 2 demonstrated significant improvements in concentration uniformity, particularly at low state-of-charge (SOC) levels. The obstacle design mitigated local depletion of active species, thereby enhancing limiting current density and improving minimum concentration values across the studied SOC range. However, the introduction of obstacles increased flow resistance and pressure drops, indicating a trade-off between electrochemical performance and pumping energy requirements. Notably, Case 2 performed better at lower flow rates, showcasing its potential to optimize efficiency under varying operating conditions. At higher flow rates, the advantages of Case 2 diminished but remained evident, with better concentration uniformity, higher minimum concentration values, and a 1% average increase in limiting current density. Future research should focus on optimizing obstacle geometry and positioning to further enhance performance. Full article

The objective of this study was to examine the changes in starch processed under various ohmic heating (OH) conditions in relation to the characteristics of nixtamalized maize. Ground and dehydrated nixtamalized doughs (masas) were analyzed. Samples were prepared using both OH and traditional nixtamalization methods for comparison. The OH process variables included cooking temperature (85 and 90 °C), heating time (0, 5, and 10 min), and voltage (120 and 130 V). Starch modifications were assessed through viscosity measurements, differential scanning calorimetry (DSC), X-ray diffraction, and scanning electron microscopy (SEM). The results showed that viscosity in OH-treated samples was influenced by both thermal conditions (time and temperature) and the electric field (at 130 V), due to gelatinization and electroporation, evidenced by starch granule damage in SEM. DSC and X-ray diffraction revealed gelatinization and a loss of crystalline structures, along with new interactions between starch components that stabilized the system and reduced peak viscosity in the OH masa flours. Full article

Peeling is a key step in the industrial production of canned peeled tomatoes, vital for optimizing efficiency, yield, product quality, waste reduction, and environmental impact. This study presents a comparative assessment of the economic and environmental impacts of adopting innovative peeling technologies, including infrared (IR), ohmic heating-assisted lye (OH-lye), and ultrasound-assisted lye (US-lye) peeling, relative to conventional steam and lye peeling methods. Focusing on a medium-sized Italian tomato processor, the impacts of these methods on productivity, water and energy consumption, wastewater generation, and environmental footprint using Life Cycle Assessment (LCA) methodology, were evaluated. Findings indicated that adopting IR, OH-lye, and US-lye methods enhanced peelability (ease of peeling > 4.5) and increased production capacity by 2.6–9.2%, while reducing solid waste by 16–52% compared to conventional steam and lye methods. LCA results showed IR as the most environmentally favorable method, followed by steam, OH-lye, and US-lye, with conventional lye peeling being the least sustainable. OH-lye and IR methods also significantly reduce water and energy use, while US-lye shows higher demands in these areas. Additionally, OH-lye and IR methods require little or no NaOH, minimizing chemical consumption and wastewater production, which offers notable environmental and cost advantages. Overall, this preliminary study underscores economic and environmental potential for novel peeling technologies, encouraging industry consideration for adoption. Full article

Quantum well infrared photodetectors (QWIPs) are popular due to their following advantages: low cost, maturity of manufacturing, high uniformity, ease of wavelength adjustment, resistance to heat, and resistance to ionizing radiation. However, their low absorption efficiency due to their unique anisotropic absorption properties and ohmic loss of the metal grating severely limit their further adoption. We cleverly used cascaded dielectric metasurfaces to replace the traditional single-layer metal grating, which increased the absorption efficiency to near the upper limit of 100%. By analyzing the near-field profile of the electric field of the miniaturized device, we found that the upper grating, QWIP, and lower grating formed a high-efficiency FP cavity with a strong photon localization capability, allowing the microdevice to effectively achieve 99.3% absorption. In addition, QWIPs with cascade gratings can be incorporated into a polarimeter, allowing for the comprehensive detection of linear polarization information at a wavelength of 14 $\mathsf{\mu }\mathrm{m}$ through rational rotations. Our proposed double-layer grating coupling method can be considered a technology that can effectively address the low-absorption problem associated with QWIPs. Full article

A novel cell topology for a vertical 1200 V SiC planar double-implanted MOSFET (DMOSFET) is proposed in this work. Based on the conventional linear cell topology and the calibrated two-dimensional (2D) technology computer-aided design (TCAD) model parameters, a novel cell topology with the insertion of P+ body implanted regions over a fractional part of the channel and junction field effect transistor (JFET) regions was designed and optimized to achieve a low high-frequency figure of merit (HF-FOM, R_on × C_gd). Utilizing three-dimensional (3D) TCAD simulations, the new proposed cell topology with optimized selected structure parameters exhibits an HF-FOM of 328.748 mΩ·pF, which is 10.02% lower than the conventional linear topology. It also shows an improvement in the switching performance, with an 11.73% reduction in switching loss. Moreover, the impact of source ohmic contact resistivity on the performance of the proposed cell topology was highlighted, indicating the dependency of the source ohmic contact resistivity on the switching performance. This research provides a new perspective for enhancing the switching performance of SiC MOSFETs in high-frequency applications, considering practical factors such as contact resistivity. Full article