Boosting cell performance and fuel utilization efficiency in a solar assisted methanol microfluidic fuel cell

Solar generated hydrogen from an optimized P25 thin film of 3.2 mg/cm² with 0.25% of platinum as co-catalyst improves the peak power output of a methanol microfluidic fuel cell operated with a methanol to water ratio of 1:1 almost ninefold, from 22 mW/cm² to 213 mW/cm². Different methanol to water ratios in the fuel tank generate similar amounts of hydrogen, but the cell performance has large variations due to the different oxidation kinetics of hydrogen and methanol in the fuel breathing anode, resulting in a mixed-potential anodic performance. The trade-off between power output and fuel utilization diminishes in this system. The methanol utilization efficiency at peak power operation increases from 50% (for 0.2 V) to 78% (for 0.5 V) for methanol to water ratio of 1:1. The result indicates that in-situ generation of hydrogen by solar light can be applied to both portable and large-scale stationary fuel cells.     

Thermo-mechanical Analysis of Friction Stir Welding:A Review on Recent Advances

In recent studies, critical research interest exists in the thermo-mechanical analysis of the friction stir welding(FSW) process by numerical simulation. In this review, the thermo-mechanical analysis for FSW is overviewed regarding the computational approaches, the heat generation, the temperature, and the material fl ow behavior. Current concerns, challenges, and opportunities in current studies are discussed considering the application of the thermo-mechanical analysis. Generally, larger computational scale and better computational effi ciency are required to allow better spatial resolution in future analysis. The concepts and approaches demonstrated in the thermo-mechanical analysis for FSW open up quantitative prospects for the design of the FSW process.     

基于功频下垂控制的光伏并网发电系统惯量阻尼机理研究

针对光伏以低惯量、弱阻尼的特征大规模接入电网，给电网稳定性带来不利影响的问题，基于功频下垂控制的光伏并网发电系统，借鉴经典电气转矩分析法，从物理机制层面上分析影响系统惯量、阻尼以及同步能力的作用规律。研究结果表明对于控制参数的影响规律而言，惯量特性主要受功率环的比例系数Kp影响，且随Kp的增大而增强；阻尼特性受频率下垂系数Dp影响比较明显，且随Dp的增大而减弱；同步特性只受功率环的比例积分系数Ki影响，且随Ki的增大而增强。通过仿真验证了理论分析的正确性。     

Pd nanoparticles anchoring to core-shell Fe3O4@SiO2-porous carbon catalysts for ammonia borane hydrolysis

A modified Stöber method is applied to synthesize the magnetic core-shell Fe₃O₄@SiO₂ particles, followed by compositing a series of porous glucose-derived carbon with ZnCl₂ as etchant. Then, ultrafine Pd nanoparticles (NPs) are successfully anchored to the resulting Fe₃O₄@SiO₂-PC composites with an in-situ reduction strategy. The particle sizes of Pd NPs are mainly centered in the range of 2.3–4.3 nm in the as-prepared Pd/Fe₃O₄@SiO₂-PC catalysts, owning a hierarchical porous structure with high specific surface area (S_BET = 626.0 m² g⁻¹) and large pore volume (V_p = 0.61 cm³ g⁻¹). Their catalytic behavior for the hydrogen generation from ammonia borane (AB) hydrolysis is investigated in details. The corresponding apparent activation energy is as low as 28.4 kJ mol⁻¹ and the reaction orders with AB and Pd concentrations are near zero and 1.10 under the present conditions, respectively. In addition, the magnetic catalysts, which could be easily separated out by a magnet, are still highly active even after nine runs, revealing their excellent reusability.     

Promoted hydrolysis performances and mechanism of Si-NaBH4-AlCl3 in deionized water

Si-based hydrolysis material system can be used in mobile/portable hydrogen source applications connected to fuel cells but is limited by alkaline solutions. In the present research, we reported an acid/alkaline free hydrolysis system combining silicon with NaBH₄. Samples with different ratios between Si and NaBH₄ are prepared via high energy ball milling and hydrolyzed in deionized water at different temperatures. Synergetic effect between silicon and NaBH₄ was found in the hydrolysis process. 2Si-NaBH₄ sample displays the best hydrolysis performances with the hydrogen yield of 1594 ml⋅g⁻¹ in deionized water at 70 °C. Thereafter, AlCl₃ is added into the 2Si-NaBH₄ sample to further improve its comprehensive properties. The effect of AlCl₃ content and promotion mechanism of the reaction are explored. 2Si-NaBH₄–5 wt% AlCl₃ sample shows a significant improvement with a high hydrogen yield of 1689 ml·g⁻¹ in deionized water at 70 °C and a corresponding conversion rate of 95.8%, indicating that the Si-NaBH₄-AlCl₃ composite is promising to be a hydrogen source in applications of mobile/portable fuel-cell-powered facilities.     

Hetero-nanostructured metal oxide-based hybrid photocatalysts for enhanced photoelectrochemical water splitting – A review

This review is mainly focused on nanostructured metal oxide-based efficient photocatalysts for photoelectrochemical (PEC) water splitting applications. Owing to their distinctive physical and chemical properties, metal-oxide nanostructures have attracted a wide research interest for solar power-stimulated water splitting applications. Hydrogen generation by solar energy-assisted water splitting is a clean and eco-friendly route that can solve the energy crisis and play a significant role in efforts to save the environment. In this review, synthesis strategies, control of morphology, band-gap properties, and photocatalytic application of solar water splitting using hierarchical hetero-nanostructured metal oxide-based photocatalysts, such as titanium dioxide (TiO₂), zinc oxide (ZnO), and tungsten/wolfram trioxide (WO₃), are discussed.     

Power generation potential of liquified natural gas regasification terminals

The share of liquified natural gas (LNG) in the international trade of natural gas (NG) is continually increasing. This presents increasing opportunities to build power plants to generate electricity at LNG regasification terminals rather than wasting the power generation potential of LNG at about −162°C by regasifying it by seawater, ambient air, or by burning NG. Typically, over 5% of the NG received at LNG plants is used to liquify the remaining incoming gaseous NG at environmental conditions. Theoretically, all the energy consumed at LNG liquefaction plants can be recovered at LNG regasification terminals. In this study, the theoretical and practical power generation potential of regasified LNG is investigated by performing energy and exergy analyses. It is shown that up to 0.191 kWh of electric power can be generated during the regasification of LNG per standard m³ of NG regasified. The potential economic gains associated with power generation at LNG regasification facilities are demonstrated by analyzing the 2018 LNG imports of Turkey as a case study and the world. It is shown that the 314 million tons of LNG imported globally in 2018 has the electric power generation potential of 88 billion kWh with a market value of over 10 billion USD. It also has the potential to offset 38 million tons of CO₂ emissions.     

Performance assessment of steam Rankine cycle and sCO2 Brayton cycle for waste heat recovery in a cement plant: A comparative study for supercritical fluids

The main objective of this study is to investigate the feasibility of a waste heat recovery (WHR) closed Brayton cycle (BC) working with supercritical carbon dioxide (sCO₂). For this aim, an actual WHR steam Rankine cycle (RC) in a cement plant was evaluated thermodynamically. After, a sCO₂-BC was theoretically adapted to the actual WHR system for the performance assessment. Both systems were analyzed comparatively in terms of energy and exergy. According to the results, the sCO₂-BC showed higher performance than the actual steam RC with a net electricity generation of 9363 kW where it was calculated as 8275 kW for the actual cycle. In addition, the energy efficiencies were found to be 27.6% and 24.18% where the exergy efficiencies were calculated as 58.22% and 51.39% for sCO₂-BC and steam RC, respectively. In the following part of the study, the closed BC was examined for different supercritical working fluids, namely, CO₂, pentafluoroethane (R125), fluoromethane (R41), and sulfur hexafluoride (SF6). Parametrical analyses were conducted to determine the effects of the system parameters such as turbine inlet temperature, compressor inlet temperature, and pressure ratio on the cycle performance. The simulation results of the comparative study showed that, among the supercritical fluids, the CO₂ demonstrated a higher performance for the closed BC with an energy efficiency of 27.9% followed by R41, SF6, and R125. As a result, the utilization of sCO₂-BC for WHR can be sustainably adapted and extended for environmentally friendly energy generation.