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Navigating the Impact of Renewable Energy, Trade Openness, Income, and Globalization on Load Capacity Factor: The Case of Latin American and Caribbean (LAC) Countries
Considering relatively high but recently decreasing environmental quality in the LAC countries with regard to the world, this study uncovers the progress of environmental quality, which is proxied by load capacity factor (LCF). In this context, the study considers renewable energy, trade openness, income, and globalization as explanatory indicators; uses data from 1990 to 2018; applies pooled mean group autoregressive distributed lag (PMG-ARDL) approach as the main model; and performs panel Toda-Yamamoto (PTY) causality test as robustness model. This is important because the LAC countries have ecological reserves, whereas many countries have an ecological deficit. For this reason, the investigation of the LAC countries has significance for the environmental quality in the world. Also, this study has novelty in terms of examining LAC countries and using the LCF as the environmental quality. The results present that (i) renewable energy has an improving impact on the LCF in both the short run and the long run; (ii) trade openness has a stimulating impact on the LCF in the long run; (iii) however, globalization and economic growth have a degrading impact on the LCF in the long run. Hence, it can be drawn from the results that renewable energy and trade openness have a critical impact on preserving and developing environmental quality. In line with the empirical findings, it can be proposed that LAC countries should utilize renewable energy effectively, improve trade volume through trade openness, increase renewable energy technology import, and expand the use of renewable energy in foreign trade activities. Thus, effective renewable energy and foreign trade policies can promote the achievement of sustainable development goals (SDGs) in the LAC countries.
Thermal Management Analysis of Proton Exchange Membrane Fuel Cell Filled with Phase Change Material in Cooling Channel
Passive thermal management using a phase-change material (PCM) for proton exchange membrane fuel cells (PEMFCs) has been proposed and widely used in the thermal management of Li-ion batteries. A three-dimensional and nonisothermal numerical model of a PEMFC with a PCM cooling channel (PCC) is established in this study. The PCC is better than an air-cooling channel (ACC) in terms of reactant distribution and water removal. Its temperature at the interface of the gas diffusion layer and catalyst layer is lower, and the uniformity of temperature is better. The peak current and power density of the PCC are 4.60% and 5.14% higher than those of the ACC, respectively. Furthermore, the PCC does not increase parasitic power, unlike the ACC. In addition, owing to the high temperature near the outlet, the cooling effects of filling 1/3 PCM and filling 2/3 PCM near the outlet and filling of all PCM are investigated, which shows that the filling of 2/3 PCM provides a better cooling performance.
A Study of Copyrolysis Characteristics of Sewage Sludge and Waste Polypropylene
This study investigates the copyrolysis of sewage sludge (SS) and waste polypropylene (PP). SS exhibited low heating value and high ash content, whereas PP had a high heating value and volatile content. The properties of SS and PP were analyzed, and copyrolysis process, activation energy, synergistic effects, and gas yield were investigated using thermogravimetry combined with Fourier-transform infrared spectroscopy. The results showed the existence of a three-stage synergy, and showed maximum aromatic yield. The activation energy value for the blended fuel exhibited positive synergy. The Taguchi method was used to determine the operating conditions in a high-temperature furnace for the maximum C5–12/C19+ ratio and optimal pyrolysis oil quality. The PP : SS ratio was the most influencing parameter, followed by the pyrolysis temperature. 30% PP and 10% PP had the best C5–12/C19+ ratio and pyrolysis oil quality, respectively. We obtained a maximum C5–12/C19+ ratio of 9.1 and the optimal ratio of petrochemical product components () to worthless products () of 4.02. The optimal experimental parameters to achieve these two targets were operated with 10% HZSM-5 and activated alumina. HZSM-5 improved the heating value, oil yield, carbon-number ratio, and pyrolysis oil quality.
Ultrahigh Performance Piezoelectric Energy Harvester Using Lead-Free Piezoceramics with Large Electromechanical Coupling Factor
The output power of piezoelectric energy harvester (PEH) at the resonance frequency is dependent on the electromechanical coupling factor () of the piezoceramic, which is proportional to , where and are the piezoelectric change and dielectric constants, respectively. Therefore, the piezoceramic for the PEH should have a large and a small . -texturing can be used for developing piezoceramics for PEH because it generally increases without increasing . The 0.96(K0.5Na0.5)(N1-zSz)O3-0.03(Bi0.5Ag0.5)ZrO3-0.01SrZrO3 [KN(N1-zSz)-BAZ-SZ] piezoceramics were textured along the  orientation, and the piezoceramic () showed a large of 0.77, which is the largest for KNN-related piezoceramics reported in the literature. The cantilever-type PEH manufactured using the KN(N0.99S0.01)-BAZ-SZ piezoceramic exhibited a large output power density of 7.86 mW/cm3 at resonance frequency because of its large . To date, this is the largest power density for PEHs manufactured utilizing lead-free piezoceramics. Hence, the -textured KN(N0.99S0.01)-BAZ-SZ piezoceramic is an excellent candidate for PEH, and -texturing is a very efficient method for developing piezoceramics for PEH.
Effect of Posttreatment on the Catalytic Performances of Fe-N-C for Oxygen Reduction Reactions
Herein, we report the significance of posttreatment in the design of high-performance Fe-N-C-type catalysts for oxygen reduction reaction (ORR). Enhancing the catalytic performance of Fe-N-C requires a postprocess for removing the aggregated iron species formed during high-temperature pyrolysis since they have a negative effect on ORR. We were able to obtain a catalyst precursor for the Fe-N-C reaction via pyrolysis with iron-adsorbed 1,8-diaminonaphthalene (FeDN), which was then treated with a concentrated HCl solution for the removal of the aggregated iron species produced. The HCl-treated FeDN was subsequently annealed at various temperatures to investigate the effect of the annealing process on the physical properties and ORR performance. The annealing temperature was a critical factor affecting the residual contents of impurities, as well as the active component and the electronic state of nitrogen. We also examined the influence of different types of acid (HCl, H2SO4, and HNO3) on the catalytic performance. The type of acid used for removing aggregated iron species had an impact on both the Fe contents and the relative nitrogen species content. Among the catalysts tested, the catalyst prepared by annealing the HCl-treated FeDN at 700°C had the best ORR performance. Although its initial ORR performance in acidic conditions was lower than that of a commercial Pt/C, it was more durable. In alkaline conditions, it delivered a comparable initial ORR performance to Pt/C and also exhibited higher durability.
Numerical Simulation on Enhanced Heat Transfer and Flow Characteristics in Direct-Contact Heat Exchanger: A Novel Kenics Static Mixer
In this paper, a novel Kenics static mixer applied in a direct-contact heat exchanger (DCHE) was proposed in order to enhance the heat transfer efficiency. The computational fluid dynamics (CFD) simulation method was adopted to investigate the effect of the continuous phase and dispersed phase on direct-contact heat transfer (DCHT) in the Kenics static mixer. The perforation index (PI) was introduced to depict the performance of the Kenics static mixer, and the effect of different numbers of openings at three initial heat transfer temperature differences (at the inlet of the continuous and dispersed phases) was studied. The simulation results showed that under the same working conditions, a larger initial temperature difference would result in greater differences in the fluid uniformity index (UI), turbulence intensity, and time evolution of a gaseous working substance. The increase of hole numbers and decrease of hole diameters can optimize the DCHT. Under three initial temperature differences, the heat transfer efficiency for the 6-hole and 9-hole Kenics DCHEs was about 20% higher than the Kenics DCHE without holes.