The sluggish kinetics of Oxygen Evolution Reaction (OER) is a challenge for the development of efficient photoelectrochemical (PEC) systems for sustainable hydrogen production. In this work, α-Fe₂O₃/g-C₃N₄ photoanodes were prepared from g-C₃N₄ of different precursors (urea, melamine and/or dicyandiamide) to investigate the influence of hybrid precursor engineering on the photoelectrochemical properties of the heterostructures. The incorporation of hybrid precursor derived g-C₃N₄ modified the structural and optical properties of the composite photoanodes and resulted in enhanced PEC response compared to single precursor systems. The as prepared composite with g-C₃N₄ prepared from ternary hybrid precursors (urea, melamine and dicyandiamide) showed the best performance among the as prepared samples with lowest onset potential (0.01 V) and highest ΔE (0.88 V) under the present experimental conditions. Photoluminescence analysis indicated a lower emission intensity of the ternary hybrid precursor-derived sample, which was attributed to the inhibited charge carriers recombination. Furthermore, the addition of 5-hydroxymethylfurfural (HMF) as a model organic substrate increased the photocurrent density (~95%) with no change in the onset potential, demonstrating the effective hole scavenging ability of the HMF. Chronopotentiometry measurements confirmed stable operation during continuous illumination. These findings demonstrate that the hybrid precursor engineering of g-C₃N₄ can affect the PEC behavior of α-Fe₂O₃/g-C₃N₄ photoanodes under HMF-assisted conditions.
Pseudomonas cepacia lipase was immobilized on low-density polyglutaraldehyde–styrene-coated expandable polystyrene beads (PGlu–STY/EPS) and applied as a reusable biocatalyst for biodiesel production from soybean oil via ethanolysis. The catalyst system was developed through a progressive catalyst-engineering strategy involving floating-support design, support-density engineering, particle-size optimization, and coating-morphology refinement to improve catalyst distribution, interfacial accessibility, and operational stability. The immobilized lipase exhibited a protein-loading yield of 71.81% and a catalytic activity of 26.12 U g⁻¹ support. Smaller EPS particles and optimized PGlu–STY coating conditions improved enzyme-immobilization efficiency and catalytic performance by enhancing substrate accessibility and reducing diffusion limitations. Under optimized transesterification conditions—an oil-to-ethanol molar ratio of 1:5, a temperature of 40 °C, a reaction time of 24 h, and absolute ethanol—the maximum fatty acid ethyl ester (FAEE) conversion reached 92.8%. Biodiesel conversion was quantified using ¹H NMR spectroscopy. The immobilized catalyst retained substantial catalytic activity over more than 10 consecutive reaction cycles, indicating favorable operational stability and reusability. FT-IR analysis suggested successful covalent immobilization through Schiff-base interactions between aldehyde groups on the support and amino groups on the enzyme. The floating, low-density EPS architecture may improve catalyst distribution in the heterogeneous oil–alcohol reaction medium and reduce unfavorable sedimentation in glycerol-rich regions, thereby enhancing interfacial transesterification. Although advanced characterization techniques such as BET, XPS, and GC–MS were not available in the present study, the combined catalytic and morphological results demonstrate that PGlu–STY/EPS is a potentially useful support for reusable immobilized-lipase systems in enzymatic transesterification.
The use of renewable energy sources in distribution networks results in considerable environmental and economic benefits, but it introduces challenges related to uncertainty, intermittency, and system stability. A complete multi-objective optimization model is developed that integrates renewable energy units, battery energy storage systems, electric vehicles, demand response programs, and hydro turbine units to solve these problems. The proposed methodology achieves cost savings and reduces carbon footprint while maintaining operational stability in the system. The optimization model includes full mathematical representations of all components including photovoltaic and wind generation systems and battery energy storage system state-of-charge dynamics and electric vehicle charging and discharging schedules and controllable hydro generation. A time-of-use demand response scheme is adopted to model demand flexibility which allows for load shifting and increased renewable utilization. The model is employed in a case study of 150 customers; the framework shows its efficiency through comparative simulations that evaluate performance under scenarios with demand response and without demand response. The results show that demand response reduces peak demand, improves storage coordination, and increases renewable integration. The demand response lowered costs to $6,300-$11,150 and emissions to 12,825-12,860 kg. The configuration of electrical vehicle and battery energy storage systems are combined to achieve peak shaving allowing customers to support the grid and the hydro turbine can provide effective back up power when the renewables are unavailable. The results indicate that coordinated optimization of renewables with storage and demand flexibility leads to improvements in cost-emission performance while enhancing sustainability and system resiliency.
The growing global demand for renewable energy has increased the need to diversify electricity systems toward low-impact sources. In this context, run-of-river hydropower plants are increasingly recognized as promising options, as they can generate electricity with relatively limited environmental and social disruption. However, their potential in arid and semi-arid regions remains underexplored, especially under highly variable hydrological conditions. In this context, this study assesses the technical hydropower potential of the semi-arid Bouregreg watershed in Morocco using a distributed run-of-river scheme. The Soil and Water Assessment Tool model was used to simulate streamflow and establish power-duration curves throughout the watershed. These curves were then used to estimate the technical potential based on a modular turbine system consisting of an optimal number of identical Crossflow turbines operating in parallel. The calculations incorporated technical and environmental constraints and were complemented by a preliminary cost assessment. The potential was also evaluated under typical, extreme dry, and extreme wet hydrological conditions. The results indicate a total hydropower potential of 34.3 MW under typical conditions, increasing to 89 MW under wet conditions and decreasing to 12.5 MW under dry conditions. Although the cost analysis revealed values slightly higher than reported average small-hydropower costs, some sites remained within reasonable cost ranges, particularly in the Grou subwatershed, where the estimated annual energy production could potentially cover approximately 58% of its population’s annual electricity demand under normal hydrological conditions. These findings highlight the existence of underexploited potential of run-of-river systems in semi-arid basins and provide a preliminary framework for identifying viable hydropower opportunities.
The successful fabrication of composite hydrogel beads was realized through the integration of activated pomelo peel biochar (PBC) into a sodium alginate (NaAlg) polymeric matrix, a process facilitated by Ca2+-induced ionic cross-linking. Morphological evaluations of the resulting material confirmed a highly textured surface, demonstrating that the PBC particles were effectively and uniformly embedded within the alginate framework. In terms of performance, the composite formulation consisting of 3.3% (w/v) PBC and NaAlg exhibited exceptional adsorption affinity for both methylene blue (MB) and methyl orange (MO) dyes. The equilibrium data showed a superior fit to the Langmuir isotherm model, which implies a predominantly homogeneous monolayer adsorption process; under continuous flow conditions at 30°C, the maximum adsorption capacities were recorded at 279.68 mg/g for MB and 179.02 mg/g for MO. Furthermore, kinetic modeling indicated that the adsorption behavior strictly followed a pseudo-second-order mechanism, suggesting that the rate-limiting step is governed by chemisorption rather than physical forces alone. The fundamental removal mechanism is believed to be a synergistic interplay of various physicochemical forces, including pore-filling within the biochar structure, π-π interactions between aromatic rings, and the formation of hydrogen bonds between the dye molecules and the composite surface.
Modifying flap geometry to reduce trailing-edge turbulence is an effective approach to lower wind-turbine blade aerodynamic noise. Based on the NACA0018 airfoil, a new bionic serrated flap was designed by mimicking the owl wing structure. Numerical methods were employed to investigate its noise reduction mechanism, utilizing Improved Delayed Detached Eddy Simulation (IDDES) and the Ffowcs Williams-Hawkings (FW-H) method. The aerodynamic and aeroacoustic performance of the baseline airfoil, a flat-plate Gurney flap (PGF), a standard serrated flap (SGF), and the bionic flap (BGF) were calculated at different inflow wind speeds (Re = 7×104, 1.4×105 and 2.1×105) under various inflow angles (0°, 6°, 10° and 15°). Numerical results demonstrate that the proposed BGF configuration mitigates the additional noise induced by the traditional Gurney flap, with reductions observed in the overall sound pressure levels across the monitored directivity points. Compared to the baseline airfoil, the BGF demonstrates noise reduction at low angles of attack (AoA < 6°), with a peak OASPL decrease of 4.6 dB. However, this aeroacoustic advantage diminishes rapidly as the AoA exceeds 6°, suggesting that the noise-suppression effectiveness of the bionic contour is highly sensitive to the inflow angle. Analysis of wake vortex structures and turbulence intensity reveals that the curved bionic flap effectively suppresses vortex clusters and turbulence intensity, leading to reduce the airfoil's aerodynamic noise.
This study proposes a hybrid metaheuristic that combines the Coyote Optimization Algorithm (COA) and the Water Cycle Algorithm (WCA) to improve multi-objective optimization of a hybrid renewable energy microgrid (HRES) for Nusa Penida Island. Such islanded systems must balance investment cost, operational reliability, and renewable curtailment while facing stochastic weather and demand. The optimization therefore targets simultaneous minimization of cost of energy (COE), loss of power supply probability (LPSP), and dummy load (DL) as key indicators of affordability, adequacy, and energy-utilization efficiency. A sequential Hybrid COA–WCA framework is implemented using an annual time-series of electrical demand and local renewable-resource profiles. Candidate solutions encode the main HRES components, including photovoltaic generation, wind generation, battery storage, and conventional backup biodiesel generation, while respecting practical operating limits. Multi-objective optimization is handled using a weighted-sum formulation, subject to standard power-balance, component-operating, and reliability constraints. The proposed approach is benchmarked against standalone COA, WCA, and WOA under multiple uncertainty scenarios that perturb techno-economic parameters and resource–load conditions. The Hybrid COA–WCA achieved the lowest mean objective value (mean f = 0.87274; min = 0.82136; max = 0.92409) and the best final-iteration mean of 0.87258 compared with COA (0.87303), WCA (0.87367), and WOA (0.87756). The optimized design delivered COE = 1.388, LPSP = 0.03180, and DL = 6,609.025 on average across scenarios. Robustness analysis also indicates faster stabilization and the smallest end-of-run fluctuation range (0.82136–0.92409), confirming improved convergence stability relative to the benchmark algorithms. Overall, the Hybrid COA–WCA provides a stable and competitive optimization approach for HRES sizing under uncertainty, yielding consistently high-quality solutions that support planning and decision-making for island microgrids.
This study examines the trade-off between economic growth and renewable energy consumption in 31 Asian economies over the period 1996-2023, with a focus on the moderating role of governance quality. Using fixed-effects panel estimation, with country-clustered standard errors, we construct a multi-dimensional governance quality index based on Principal Component Analysis (PCA). The findings suggest that economic growth is associated with a statistically significant decline in the share of renewable energy consumption (β=-13.59, p<0.01). In semi-log terms, a 1% increase in GDP per capita is associated with a 0.136 percentage-point reduction in renewable energy consumption share, implying the presence of growth-induced fossil fuel dependence. However, the interaction term between growth and governance is positive and significant (β=1.73, p <0.05), indicating that stronger governance quality mitigates this adverse effect. Further analysis using an environmental Kuznets curve (EKC) specification reveals a U-shaped relationship between income and renewable energy consumption. Sensitivity analysis using disaggregated governance indicators shows that government effectiveness and regulatory quality are the key institutional dimensions driving this moderating effect. Subsample analysis further uncovers significant heterogeneity across income groups. While the trade-off is prominent in lower-middle and upper-middle income economies, high-income countries exhibit a positive growth-renewable energy consumption nexus. The results remain robust when using lagged explanatory variables. This study contributes to the literature by providing cross-country evidence of a fossil lock-in effect in Asia and by identifying governance quality as a moderating institutional mechanism shaping the energy transition. The findings underscore the importance of strengthening institutional quality to align economic growth with renewable energy development in heterogeneous Asian contexts.
The development of cost-effective, highly efficient adsorbents for bioethanol dehydration is crucial to advancing sustainable biofuel integration, including the upcoming E10 fuel-blending mandates in Indonesia. This study evaluates the multifunctional capability of locally sourced Bangka kaolin as both a structural precursor and an active binder for the synthesis of binder-converted Zeolite 3A pellets, specifically tailored for ethanol-water azeotrope separation. The fabrication procedure followed a comprehensive two-stage method, commencing with the thermal calcination of raw kaolin at 600°C and 750°C to generate reactive metakaolin. Subsequently, a hydrothermal synthesis strategy was employed using different alkalinity settings, governed by H2O/Na2O molar ratios of 40, 43, and 45, corresponding to NaOH concentrations of 2.88 M, 2.67 M, and 2.55 M, respectively. This solution-gel matrix was homogenized with synthesized Zeolite Na-A powder, extruded into pellets, and subjected to an in-situ hydrothermal crystallization phase to transform the amorphous binder into a crystalline Zeolite A framework. Final structural modification was performed via successive liquid-phase potassium-ion exchanges using 21 wt.% and 11 wt.% chloride potassium solutions to shrink the effective pore opening to approximately 3A. Structural and compositional assessments via X-ray diffraction (XRD) and X-ray fluorescence (XRF) confirmed the successful formation of Zeolite A frameworks with no residual sodium oxide (0.00% Na2O), achieving significant potassium loading (30.15–34.58 wt.% K2O) and moderate relative crystallinities ranging from 55% to 74%. Textural diagnostics from N2 physisorption demonstrated that the synthesized pellets exhibit an IUPAC Type IV isotherm coupled with a Type H3 hysteresis loop, indicating a hierarchically organized pore structure with crucial secondary mesopores. Performance evaluation during dynamic ethanol-water separation confirmed that the synthesized Zeolite 3A pellets exhibit an enhanced water adsorption capacity of up to 27.97 wt.% for the ZKA-750-45 sample, yielding fuel-grade bioethanol with a peak purity of 99.7 wt.%.
In practical Battery–Supercapacitor Hybrid Power Source (Batt-SC HPS) applications for Electric Vehicles (EVs), parameter variations and actuator input constraints are unavoidable due to changing operating conditions, temperature effects, and physical limitations of power converters and switching devices. These conditions may degrade control performance and potentially lead to closed-loop instability. This paper proposes a control synthesis for a Batt-SC HPS system that guarantees closed-loop stability in the presence of parameter variations and input saturations. A polytopic linear parameter-varying (LPV) model is employed to represent parameter variations in the linearized system around its equilibrium point. Based on this model, a full state-feedback controller is synthesized using simultaneous linear matrix inequalities (LMIs) as sufficient conditions for robust stability across all system vertices. The formulated LMIs incorporate a common quadratic Lyapunov function, L2-gain performance, and sector nonlinearity to explicitly handle control input saturations. Numerical validation is performed under internal resistance variation scenarios using an LMI solver. Closed-loop simulation results show that the proposed controller reduces the battery current RMSE by 70.8% and the DC bus voltage RMSE by 87.4% compared with a conventional PID controller. In comparison with a nominal LTI controller, additional RMSE reductions of 38.31% for battery current and 2.82% for DC bus voltage are achieved. Moreover, the proposed controller maintains comparable energy consumption characteristics, with total energy differences of only 0.22% and 0.11% relative to the PID and LTI controllers. These results demonstrate the potential of the proposed controller for robust stabilization of Batt-SC HPS systems in EV applications.
Small-scale wind turbines offer sustainable solutions for distributed renewable energy generation in urban environments. However, their deployment is often limited by concerns related to noise, visual impact, and risks to flying wildlife. This study presents an experimental investigation of a novel origami-inspired reaction-type wind turbine designed to improve urban compatibility through a compact, aesthetic, and bladeless configuration that enhances operational safety. Unlike conventional lift- or drag-based turbines, the proposed design operates based on a reaction force generated by redirecting axial inlet airflow into tangential outlet flow through internal nozzle conduits. Two miniature prototypes were fabricated using 3D printing with rotor diameters of 10 cm and 8 cm, both designed with a nozzle aspect ratio of unity and incorporating four inlet openings. The performance of the turbines was evaluated experimentally and theoretically under four operating conditions: free rotation, generator operation without load, fixed load operation, and variable load operation. Key performance parameters including cut-in wind speed, rotational speed, power output, and power coefficient were assessed through wind tunnel testing. The results demonstrate that the proposed origami wind turbine achieves a maximum power coefficient of C_P=0.28 at a tip speed ratio of λ=1.21, which is comparable to conventional small-scale turbines despite its bladeless configuration. Importantly, this study establishes that a reaction-type, bladeless turbine can simultaneously deliver competitive aerodynamic performance while significantly improving safety, reducing noise, and minimizing environmental impact. These findings highlight the strong potential of origami-inspired reaction-type wind turbines as viable and sustainable solutions for urban energy systems.
Biodiesel plays an important role in making diesel engines more environmentally friendly and sustainable. Biodiesel use can significantly lower emissions of harmful pollutants, contributing to cleaner air and a reduced impact on climate change. Although there is an increasing body of research on non-edible biodiesel feedstocks, few studies have been able to systematically correlate fuel production, blend variation, and engine load optimization with a single statistical framework. This study fills this gap by combining ultrasonic-assisted two-step transesterification of tobacco seed oil (TSO) with response surface methodology to determine engine performance and emissions. Acid esterification was performed to produce TSO methyl ester, which was subjected to transesterification with NaOH under ultrasonic irradiation, to guarantee efficient conversion and low levels of free fatty acids. Indeed, TSO biodiesel and diesel fuel blends were tested on the engine under different loads. The findings indicate that the engine has a critical operating point of Engine Load (EL) = 96.90% and Lower Heating Value (LHV) = 41.82 MJ/kg, at which the engine has a peak thermal performance with BTE = 32.98% and BSFC = 0.27 kg/kWh. This indicates a very effective conversion of energy because of high in-cylinder temperature and pressure. Additionally, CO and HC emissions are significantly reduced, meaning that the combustion is almost complete. Nevertheless, NOx emissions increase dramatically to 657.74 ppm, proving the thermal penalty of high-temperature operation. This trade-off is validated by multi-objective optimization, which offers a strong framework to balance efficiency and emissions in biodiesel-powered engines.
LDPE plastics contributed 20-30% of the plastics use. Due to its non-biodegradable properties, plastic waste management is crucial. In the other hand, the LDPE plastics provide potential and benefits in the exploration of energy resources; they could be converted to liquid fuels through a catalytic hydrocracking. This study focuses on the effect of temperatures during the hydrocracking of LDPE using a Ni-Cu/HZSM-5 catalyst. The Ni-Cu/HZSM-5 catalyst was synthesized using the wet impregnation method assisted by an ultrasonic irradiation. The characteristics of the catalyst were evaluated prior to its use during the hydrocracking of LDPE. This study showed that the impregnation of Ni and Cu at HZSM-5 surface did not significantly affect the crystallinity of HZSM-5. Even though the peaks of Ni and Cu in the diffraction pattern were not clearly observed, their presence at HZSM-5 surface was well confirmed by the XRF spectrum. In addition, the hierarchical structure of HZSM-5 was also confirmed by the appearance of microporosity together with the type-IV hysteresis loop on the nitrogen adsorption-desorption isotherm. A considerable decrease (~25%) of the catalyst acidity was observed after the impregnation of Ni and Cu at HZSM-5 surface. The Ni-Cu/HZSM-5 catalyst showed a good activity during the hydrocracking of LDPE at temperatures of 275−400 °C, resulting in liquid, solid, and gaseous products. The yields of the liquid product increased by increasing the hydrocracking temperatures. It was observed that by increasing the hydrocracking temperatures, the yield of the kerosene and diesel fractions decreased, while the yield of the gasoline fraction increased, as supported by the density and calorific value that was close to the commercial gasoline. A further temperature increase would lead to more products with lighter fractions, reducing the yield of gasoline. This was also supported by the presence of alkenes, ketones, and esters formed after the catalytic hydrocracking as shown by the FTIR spectra of the liquid products.
Access to electricity remains a major challenge in sub-Saharan Africa, particularly in rural areas where grid extension is often costly and unviable. Standalone photovoltaic (PV) and/or wind power systems with battery storage represent a promising solution, yet they still face technical and economic barriers, especially related to sizing and storage costs. This paper proposes an innovative methodology for the selection and optimal sizing of such systems, integrating a predictive battery aging model based on the analysis of real charge/discharge cycles using the Rainflow algorithm and Miner’s rule. The methodology relies on four main techno-economic performance indicators: the Loss of Power Supply Probability (LPSP), the Levelized Cost of Energy (LCOE), the Capacity Factor (CF) of a wind turbine, and the Weighted Index of Complementarity and Productivity (WICP). It accounts for available resources, the user’s hourly consumption profile, and local climatic conditions. The methodology is applied to a rural site in Nagréongo, Burkina Faso. The results show that only a PV/battery system is technically and economically viable, while wind and hybrid configurations are excluded due to low wind potential, as indicated by CF and WICP values below acceptable thresholds. Furthermore, the analysis demonstrates that the optimal system configuration strongly depends on the hourly consumption profile, even for identical daily energy demands. Finally, comparison with the classical intuitive sizing method and the widely used HOMER Pro software shows that the proposed approach reduces the LCOE by more than 50% and about 20%, respectively, by accurately accounting for real battery aging, demand variability, and system idle periods.
Digital technology enhances labor productivity by automating repetitive tasks and improving data-driven decision-making, while simultaneously increasing energy management efficiency through smart monitoring and optimization systems. Therefore, this study examines the impact of advanced digital technology (proxied by internet penetration) on labor productivity and energy management efficiency in Vietnam using ARDL analysis of annual data from 1990 to 2024. The model includes internet penetration, GDP per person employed (labor productivity), renewable energy consumption, and GDP growth. ADF and PP tests confirm a mixed order of integration, I (0)/I (1), justifying the use of ARDL bounds testing. Descriptive analysis indicates rapid digitalization, with internet penetration increasing from 0% to 84.15%, alongside steady productivity growth, while renewable energy consumption exhibits a strong negative correlation with the time trend (r = -0.9855), suggesting a declining pattern. ARDL results reveal very high persistence in labor productivity (lagged coefficient = 0.9929, p < 0.001). GDP growth exerts significant short-run effects, whereas internet penetration shows a delayed impact, with an insignificant contemporaneous coefficient but a positive lagged effect. Long-run estimates suggest continued productivity momentum and positive contributions from digitalization and macroeconomic growth. However, the error correction term is positive and statistically insignificant (0.1681, p = 0.597), indicating the absence of a stable long-run equilibrium relationship. Diagnostic tests confirm residual normality and homoscedasticity, while the Durbin–Watson statistic (1.5403) suggests mild positive autocorrelation. Overall, the findings highlight delayed productivity gains from digital infrastructure, emphasizing the need for complementary institutional and structural adjustments.
The objective of this study is to numerically investigate the influence of climatic conditions, particularly ambient temperature and relative humidity, on the thermal and electrical performance of photovoltaic (PV) panels, and to evaluate the effectiveness of natural and forced convection cooling for both conventional and finned panel configurations. A multilevel computational fluid dynamics (CFD) model was developed using ANSYS Fluent 16.1 under realistic environmental conditions of Baghdad, Iraq. Two configurations were examined: a conventional flat panel and a modified panel equipped with longitudinal fins acting as a passive heat sink. Under both natural and forced convection, with an inlet air velocity of 1.5 m/s for forced cooling, the simulations took into account solar radiation, species transport to capture humidity effects, and the k–ω turbulence model. Under natural convection, the traditional panel attained a maximum surface temperature of 333.11 K with an electrical efficiency of 27.8%; forced convection lowered the temperature to 319.22 K and increased efficiency to 29.88% (7.5% improvement). Under natural cooling, the finned design lowered the temperature to 327.4 K, raising the efficiency to 28.66% (~3% increase). Under forced cooling, it further dropped to 315.5 K, reaching a maximum efficiency of 30.43%. This translates to advancements of 9.4% over the traditional natural cooling scenario and 6.17% over the finned natural cooling scenario. Yearly average results show that the finned design improves electrical efficiency by about 2% under natural convection and up to 6.53% under forced convection, whereas forced cooling of the conventional panel gives a 3.12% increase. The enhancement is primarily attributed to increased heat transfer surface area and improved convective mixing, particularly under natural convection where fin-induced vortices significantly enhance heat dissipation.
This study details the development of a high-performance microbial fuel cell (MFC) utilizing a nanofiber-coated carbon anode, fabricated through the electrospinning of polyvinyl alcohol (PVA) integrated with carbon quantum dots (CQDs). A dual-chamber H-type MFC, with a working volume of 50 mL for both anode and cathode compartments, was operated in batch mode using sterilized sugarcane juice, adjusted to a pH of 7.0, as the organic substrate. Two electrogenic bacteria, Bacillus subtilis and Escherichia coli, were separately immobilized within the PVA/CQD nanofiber matrix to assess their electrochemical performance. Structural and chemical characterizations using SEM, FTIR, and UV–Vis spectroscopy confirmed the successful incorporation of CQDs and effective bacterial colonization within the nanofiber network. Electrochemical studies, such as CV and EIS, indicated low charge transfer resistance and improved electron kinetics especially when B. subtilis was present and an Rct of about 400 ohms. MFCs based on B. subtilis reached a maximum power density of 1754 mW/m² on day four of operation at a fixed external resistance of 100 0 and the electrode surface area of 9.45 cm², about 3.5 times greater than the power density obtained with E. coli (491 mW/m²). This has been due to the high performance of B. subtilis which can form a robust conductive biofilm, releases endogenous redox mediators, and has the ability to metabolize sugar rich substrates efficiently. These findings underscore the potential of PVA/CQD nanofiber-coated carbon anodes as an effective strategy for enhancing MFC performance and provide a promising foundation for future optimization and scale-up toward sustainable energy generation from organic waste at the laboratory level.
Nowadays, proton exchange membrane fuel cells (PEMFCs) are acknowledged as promising energy solutions toward reaching net-zero emissions by 2050 due to their highlighted properties, such as high energy efficiency, high power density, low operating temperature, fast start-up, and zero emissions. To enhance electrochemical reactions and improve hydrogen utilization, the dead-end anode (DEA) configuration was employed to investigate the voltage and energy efficiency of an open-cathode PEMFC stack (100 W-20 cells) at optimal fan speed under varying purge intervals and operating current load levels with the step-by-step method. The hydrogen purge operation optimization was proposed by fitting experimental data and deriving the governing equation, considering voltage stability and hydrogen consumption. The results show that when the operating current and purge interval increased, the stack voltage decreased owing to impurities, water, and nitrogen buildup in the flow field anode channel. At optimal purge intervals of 540, 360, 280, and 60 s, the energy efficiency was achieved at 45.55%, 45.31%, 43.11%, and 35.05%, respectively. Compared to a previous study, these values represent increases of 25.22%, 12.91%, 9.15%, and 2.09% for operating currents of 1, 3, 5, and 8 A, respectively. These improvements were achieved by optimizing the fan speed, purge interval, and microcontroller unit power consumption. At a low load level of 1 A, the voltage decay rate decreased from 0.45 mV s−1 to 0.07 mV s−1, allowing for stable cell performance and higher hydrogen utilization at longer purging intervals. However, at higher load levels, both the voltage change of the stack and the voltage decay rate of the stack increased significantly compared to the 1 A case, with a steeper slope corresponding to higher current levels. This indicated that at higher reaction rates, the amount of water generated from the oxygen reduction reaction increases significantly. Consequently, the back diffusion phenomenon from the cathode to the anode, along with nitrogen buildup, leads to adverse conditions such as anode channel flooding and fuel starvation. This study provides meaningful insights into optimizing the energy efficiency of open-cathode PEMFC stacks across various load levels and purge operations.
This study presents a critical review and optimization of a hybrid proton exchange membrane fuel cell (PEMFC) battery propulsion system for marine operations under dynamic working conditions. The proposed system incorporates the most current energy management methods such as model predictive control (MPC) and eco-cooling processes to maximize system performance, efficiency, and safety of its work. The system performance is tested during a typical marine load profile and compared to a conventional PEMFC-only baseline configuration that operates without hybrid energy storage or with sophisticated control systems. The findings prove that the hybrid system shows a significant enhancement in operational performance with an increase in efficiency to up to 52.6 % and a significant reduction in hydrogen consumption during the transient load conditions. Moreover, battery support is also integrated to improve load-following capabilities, and minimizing stresses on the fuel cell stack, which is essential for enhanced durability and system reliability. In addition, the given solution enhances thermal control and safety levels because the operating temperatures are kept constant, and fluctuations in the system variables are quickly reduced. The Hybrid design also facilitates a better distribution of the energy and lower auxiliary losses, hence contributing to the greater stability of the system. These results show the potential of hybrid energy storage and enhanced control measures in enhancing the efficiency, sustainability, and safety of marine propulsion systems and can provide a promising avenue to decarbonized maritime energy systems.
Indonesia is still heavily reliant on fossil fuels; however, the growth of renewable energy sources, such as biomass, offers a promising alternative energy source. Because of its high calorific value (6,500–7,600 kcal/kg) and widespread availability, coconut shell was selected for this investigation as bio-briquette. This study aimed to analyse how the properties of coconut shell bio-briquettes were affected by the carbonization time and the concentration of pine resin added as an additive. This study investigates the production and characterization of coconut shell bio-briquettes as a sustainable solid fuel. Coconut shell charcoal was carbonized at 600°C for 120, 180, and 240 min, then ground and sieved to a particle size of –60+80 mesh. Tapioca starch (5%) was used as a binder, and pine resin, derived from Pinus merkusii, was applied externally as an ignition-enhancing additive at concentrations of 2%, 4%, 6%, 8%, and 10%. The resulting bio-briquettes were analyzed for proximate parameters (moisture, ash, volatile matter, and fixed carbon) and combustion characteristics (calorific value, ignition time, and burning rate) following SNI 01-6235-2000 standards. At a carbonisation time of 240 min and a concentration of 8% pine resin, the best results were obtained in terms of moisture content (3.87%), ash (3%), volatile matter (10.80%), fixed carbon (82.33%), calorific value (7,761.21 cal/g), ignition time (63 s), and burning rate (0.1093 g/min). These findings demonstrate that pine resin can effectively enhance ignition performance without compromising the combustion stability. Coconut shell biobriquettes with the addition of pine resin show high potential as an environmentally friendly alternative fuel because they produce a high calorific value, low moisture and ash content, and fixed carbon content that meets SNI 01-6235-2000 standards and ISO 17225 for solid biofuel. These characteristic indicate that bio-briquettes can be used as a renewable energy source to replace fossil fuels for household needs and small-scale industries.
