Energy Science & Engineering最新文献

To address the problem of the chaos phenomenon caused by the parameter drift of a doubly-fed induction generator (DFIG) due to a changing operating environment, a fractional-order stator voltage/flux-oriented control model is developed, and bifurcation theory and numerical simulations reveal that the chaos mechanism originates from supercritical pitchfork bifurcation. First, the fractional-order DFIG model is constructed by introducing Caputo fractional-order derivatives and combining linear affine transformation and time-scale transformation. Second, we analyze the bifurcation characteristics of the system's equilibrium point under diverse axial rotor voltages. Third, we apply the central manifold theorem to reduce the system dimensions to derive an equivalent downscaling model and describe the bifurcation behavior near the equilibrium point. Finally, the dynamics of the DFIG system at different fractional orders are explored by employing different numerical simulation methods for the changes in the rotor d-axis voltage component and the wind turbine output torque. The analytical results indicate that the DFIG system plunges into chaos via supercritical pitchfork bifurcation. As the fractional order diminishes, the system transitions from chaotic conditions to stable conditions. Transient chaos can occur in the DFIG system under particular combinations of fractional orders and parameters.

The integration of hydrogen into existing natural gas networks represents a transformative approach to enhancing the utilization of renewable energy sources. This study focuses on the reliability of systems designed for hydrogen injection into the natural gas grid. We develop a representative system configuration and compile failure/repair data for all major components, then perform a component-level failure mode and effect analysis (FMEA) with exponential-rate assumptions to quantify subsystem and plant reliability. In the baseline (no redundancy), the overall mean time to failure (MTTF) is 186 h. Selective parallelization of pumps and compressors in Subsystems 2–5 (three units in parallel each) increases the plant-level MTTF to ~226 h (+21%), while additional parallel units show diminishing—and eventually negative—returns due to extra failure paths (valves, piping). A severity-probability (S–P) matrix pinpoints pumps and compressors as the dominant contributors to risk; control valves exhibit high impact but are not good candidates for redundancy, and the fresh water pump shows no benefit from duplication. These results provide practical guidance on where redundancy is worth the complexity and cost, and they outline priorities for future validation with hydrogen-specific field data.

To analyze the oil cavity lubrication characteristics of wind turbines sliding bearings with discontinuous flow in mixed lubrication wear caused by strong sudden changes and heavy loads, this paper aims to improve a method to analyze the pressure and temperature of different oil cavity shapes with different condition to enhance the lubrication reliability. This proposed method combining CFD simulation based on the Finite Volume Method with RNG k–ε model is demonstrated to analyze effectively the oil cavity lubrication characteristics with mixed lubrication wear. The different oil cavity shapes—circular cavity, sector cavity, and cross-shaped cavity, and different conditions including eccentricity, input pressure, temperature-viscosity, and surface roughness were analyzed to explore the effects on the maximum pressure, bearing capacity, and temperature. The study accurately evaluates the load-bearing support performance, temperature rise characteristics with different cavity shapes and different conditions. The results provide valuable references for optimizing lubrication reliability for wind power sliding bearing.

The phenomenon of annular pressure buildup (APB) is commonly observed in offshore gas wells, characterized by complex and coupled pressure types across multiple annuli. Field operations, including well shutdowns, pressure relief, and well interventions, further complicate the pressure dynamics, rendering traditional theoretical models incapable of accurately predicting annular pressure under the influence of these coupled conditions. Elevated annular pressure can lead to casing deformation and failure, posing significant risks to well integrity and production safety. This study addresses the challenge of predicting annular pressure under the coupling of multiple APB types by utilizing real-time monitoring data reflecting the annular pressure state of production wells and incorporating the influence of field operations. A convolutional neural network (CNN) is employed to optimize feature extraction, and a bidirectional long short-term memory (Bi-LSTM) network is established based on the optimized CNN kernels to predict annular pressure under complex coupling conditions. A dynamic management chart for APB is developed by incorporating the dynamic variation of wellbore pressure. The results demonstrate that the prediction accuracy of the CNN-optimized Bi-LSTM model exceeds that of the standalone LSTM model, with a mean error of 4.03% when compared with field-measured data. The inclusion of operational characteristic parameters enables the extraction of features related to human intervention, further improving the model's accuracy and reducing the mean error to 2.55%. The dynamic management chart, which incorporates the variation in wellbore pressure, provides effective guidance for field safety operations.

This study investigates the impact of uncertainty in building operation patterns on the design and techno-economic performance of solar photovoltaic (PV) systems in a commercial building in a hot arid region in Abu Dhabi, UAE. Utilizing the Design-Builder software, a model of a commercial hotel building was developed and calibrated to assess its energy demand. Three distinct operational scenarios—Austere, Baseline, and Wasteful—were analyzed in this study, each considering both grid-connected PV systems with and without energy storage solutions. The study employed sensitivity analyses to understand how variations in modeling inputs affect the levelized cost of energy (LCOE) and the levelized cost of storage (LCOS). The findings reveal significant variations in LCOE and LCOS across different scenarios, in which the minimum (LCOE) can be achieved at $0.165/kWh for the Baseline Case, $0.191/kWh for the Austere Case, and $0.162/kWh for the Wasteful Case, while the minimum (LCOS) can reach $0.30/kWh for Baseline case, $0.55/kWh for Austere case, and $0.19/kWh for Wasteful Case, underscoring the necessity of tailored PV system designs to optimize performance and economic feasibility. This study contributes to the growing body of knowledge of sustainable building energy solutions, highlighting the importance of incorporating operational uncertainties into the planning and design of renewable energy systems.

This study investigates the application of photovoltaic (PV) systems in 30-meter high-rise residential buildings in Tehran, evaluating the impact of four geographical orientations (north, south, east, and west). Using PV*SOL software, system energy production and performance were simulated based on Tehran's specific climatic conditions and solar radiation data. The primary goal is to assess the influence of panel orientation on energy efficiency, cost-effectiveness, and environmental benefits. Results show that south-facing systems, receiving 2151.86 kWh/m² of global radiation, achieved the highest energy yield of 57,937 kWh annually, with a 6.9-year payback period. In contrast, north-facing systems generated only 36,328 kWh/year and required 11.1 years for cost recovery. South-oriented systems also achieved the greatest environmental benefit, reducing CO₂ emissions by 27,196 kg per year. The economic analysis demonstrates that optimized orientation significantly improves long-term financial viability. This study highlights the strategic importance of rooftop PV deployment in high-rise buildings to enhance energy efficiency and reduce urban energy consumption. The findings also provide a valuable reference for urban renewable energy planning in cities with similar climate conditions. Future research should include the integration of energy storage systems and assess long-term dust accumulation impacts on PV system performance in dense urban settings.

Due to characteristics such as low permeability, low pressure, low gas saturation, low water content, and high structural stress, Yuwang coalbed methane (CBM) is prone to issues such as well leakage, coal sensitivity to water, and coal fines blockage. Conventional drilling fluids can cause irreversible damage to the coal reservoir, whereas gas drilling can effectively protect it. In this study, nitrogen was used for drilling horizontal wells, and drilling operations were conducted in Yuwang Township, Fuyuan County, Qujing City, Yunnan Province. Directional test wells and horizontal production test wells were drilled. Using proprietary software, various construction parameters such as gas injection rate, injection pressure, torque under different conditions, and erosion and wear of the drill string were calculated, and the results were consistent with the actual geological conditions. In actual construction, the total length of the directional well was 882 m, and the total length of the horizontal well was 1019.59 m. The gas injection rate ranged from 90 to 120 m³/min, and the drilling pressure ranged from 20 to 40 kN. It is noteworthy that the mechanical drilling speed using nitrogen drilling was 11.64 m/h, approximately three times faster than conventional drilling. The stability of gas pressure during drilling in this experiment demonstrates the effectiveness of this technology in preventing well leakage accidents. Valuable experience in gas drilling and important considerations were obtained from this experiment, providing valuable insights for future applications.

In this study, the ZnOS thin films have been fabricated by the spin coating technique for applying as an effective electron transport layer (ETL) for halide double perovskite solar cells (PSCs). The impact of the number of coatings and/or thickness variations on ZnOS thin films' properties has been analyzed in terms of surface morphology, crystal structure, elemental, and optoelectronic characteristics, and has been found to have a substantial impact on the properties of prepared thin films. For better understanding, an undoped ZnO thin film has also been analyzed alongside the ZnOS thin films. Also, the performance variation of halide double PSCs has been investigated utilizing ZnOS as an effective ETL by means of a solar cell capacitance simulator one-dimensional software. The highest power conversion efficiency (PCE) with the configuration of FTO/ZnOS/Cs₂AgBi_0.75Sb_0.25Br₆/Cu_xO/Au of 16.21% was obtained for single-coated ZnOS thin films. The result implies that ZnOS can more efficiently extract the charge carriers from the absorber layer of PSCs than pure ZnO. We anticipate that the findings of this study will lead to fresh insights into the practical applications of ZnOS as the optimum ETL for halide double PSCs.

The increasing global population and declining freshwater availability have intensified the need for sustainable water treatment solutions, particularly in arid and semiarid regions. Solar desalination ponds offer a cost-effective and environmentally friendly alternative for freshwater production; however, their efficiency remains limited by conventional materials and designs, such as the use of steel plates for the pond base and standard insulation without advanced thermal enhancement features. This study presents a comparative laboratory and theoretical investigation of two solar desalination ponds: a conventional system using steel plates and an Fe₂O₃-enhanced configuration. The modified pond demonstrated a significant improvement in thermal behavior, freshwater yield, and energy utilization. Specifically, the modified system produced up to 60% more freshwater than the conventional unit during peak summer conditions, with an average annual productivity increase of 21%. Furthermore, the highest energy and exergy efficiencies were observed in July, whereas the lowest occurred in January, underscoring the seasonal performance dynamics. Exergy efficiency consistently trailed energy efficiency by approximately 39%, highlighting system irreversibilities. This study introduces a scalable, low-cost material innovation that leverages the thermal and optical advantages of nano-ferric oxide to substantially improve desalination performance under real-world climatic conditions.

Vertical axis wind turbine (VAWT) is a suitable renewable power generation tool for use in urban areas, especially at low wind speeds and with low noise level. However, an approach with accurate results, acceptable time consumption, and cost for optimizing this turbine is not reported in the literature. The aim of this study is to propose an approach for optimizing a VAWT with three straight blades. In the first step, the air forces acting on the turbine blades are estimated by computational fluid dynamics (CFD). Three effective parameters, that is, turbine diameter, tip speed ratio, and airfoil chord length, were changed, and 180 CFD runs were performed. In the second step, to save running time and cost, an artificial neural network (ANN) method was used, and the turbine power coefficient, which was the ANN output, was predicted just by specifying the above three effective parameters. In the third step, the Genetic Algorithm optimization technique was used to find the maximum value of the power coefficient of the vertical axis wind turbine ($��\; ��C_P��$) as the objective function and the above three effective parameters as design variables in the specified range. The optimum value of power coefficient for the optimized VAWT by the use of the procedure proposed here was 0.319 (15.16% increase in comparison with 0.277 for the existing VAWT). The optimum values of design variables were also obtained: 2.5 m for diameter (instead of 1.7 m), 0.213 m (instead of 0.246 m) for the airfoil chord length, and 2.3 for the blade tip speed ratio (instead of 2.23).