Search Results (53)

With the rapid expansion of ground-mounted photovoltaic power stations, the wind-induced response and reinforcement of existing photovoltaic support structures have become increasingly important. This study investigates an existing ground-mounted photovoltaic support in Yuli County, Xinjiang, China. A fluctuating wind model based on the Davenport spectrum was established, and a one-way fluid–structure interaction method was used to analyze wind pressure distribution, displacement response, and weak components under different wind direction angles. The results indicate that the 0° wind direction is the most unfavorable condition, and that the purlins and their connection regions are the dominant weak components under fluctuating wind loads. To address the reinforcement needs of existing in-service photovoltaic power stations, a low-disturbance in situ reinforcement method was proposed by inserting internal auxiliary members into the original purlins, which can be implemented without dismantling photovoltaic modules, purlins, or existing support components. Parameter analysis showed that a 2.5 mm-thick internal reinforcement member provided an effective balance between stiffness improvement and material use. Array-scale verification demonstrated that the maximum displacement of the first-row support decreased from 5.9738 mm to 3.9377 mm after reinforcement, corresponding to a reduction of approximately 34.1%. The proposed method provides a practical, low-disturbance reinforcement strategy for existing photovoltaic support structures. Full article

With the large-scale development of renewable energy such as wind, solar and ocean energy, the demand for energy storage is more urgent. Pumped hydro energy storage (PHES) is one of the fundamental solutions to the problem of intermittent supply of renewable energy. The large-capacity/low-head pumped hydro energy storage (LL-PHES) system with the use of tubular pump turbine is a beneficial extension of traditional PHES systems owing to large flow rate and cheaper civil structures. However, the continuous competition between the “static water pressure difference caused by gravity” and the “pressure increase caused by accelerated impeller rotation” leads to prominent instability in the start-up process of the LL-PHES system under pump conditions. An explicit coupling algorithm is proposed for analyzing the transient characteristics in the start-up process of the LL-PHES system under pump conditions. This algorithm is based on the idea of dimensional transformation, and performs 3D flow calculations and 2D rigid body dynamics equation solution in the pump domain and the flap gate domain, respectively. This algorithm avoids the problems of high computational cost and poor convergence that exist in existing fully three-dimensional coupling algorithms and ensures the efficiency of transient hydraulic characteristic calculation. A comprehensive analysis of the transient characteristics of the LL-PHES system during pump start-up process is conducted using the proposed new algorithm. The entire process of the increase in rotational speed, valve opening, flow rate, and the continuous evolution of blade surface pressure during the start-up process is quantitatively described. The amplitude and spectral characteristics of the alternating pressure on multiple blades are clarified. The evolution law of blade load during the stage of severe pressure fluctuations during the start-up process is explained. The load distribution characteristics of “high in the leading and trailing edge areas and low in the middle” in the blade stream direction is presented. The research results have a direct guiding role in improving the hydraulic design and enhancing the operational stability of LL-PHES systems. Full article

Arched plastic-film greenhouses are widely used in agricultural production because of their low cost and strong adaptability. However, their lightweight and flexible characteristics make them highly vulnerable to wind-induced damage. Although previous studies have investigated greenhouse wind loads under different structural forms and wind directions, the combined influence of terrain-induced turbulence intensity and oblique wind direction on local wind pressure characteristics remains insufficiently understood. Therefore, wind tunnel experiments were carried out on a 1:10 scale model of an arched plastic-film greenhouse under three terrain categories and multiple wind directions. The local mean, fluctuating, and peak wind pressure coefficients on the greenhouse surface were analyzed to identify the governing wind directions, critical pressure zones, and turbulence amplification effects. The results show that wind direction is the dominant factor controlling the spatial distribution of local pressure on the arched roof. The most unfavorable condition occurs under oblique wind at about 60°, where the windward leading-edge corner exhibits the largest absolute values of mean suction, fluctuating pressure, and negative peak pressure coefficient. Increasing terrain-induced turbulence intensity tends to increase the mean negative pressure, fluctuating pressure, and peak pressure on the greenhouse surface. However, the amplification effect is much more pronounced for fluctuating and peak pressures than for mean pressure, and the terrain effect on mean pressure is mainly evident under oblique wind directions. The windward roof edge, roof corner, and near-gable ridge-end regions are therefore the most critical areas for wind-resistant design. Full article

In modern society, distributed photovoltaics are widely used, and overhead photovoltaic roofs are favored for their many advantages; however, they are vulnerable to failure during high-wind events. Parapets are common auxiliary structures on building rooftops. Wind tunnel testing was employed to investigate the effects of parapet configurations on wind pressures acting on overhead photovoltaic (PV) roofs. Results show that wind suction dominates, with maximum negative pressure consistently at the windward corner leading edge. A solid parapet significantly increases the maximum mean pressure coefficient, whereas perforated parapets have little effect. In most cases, parapets reduce fluctuating pressure coefficients. Extreme pressure distribution exhibits significant regional characteristics, with the most unfavorable area at the roof corner. The solid parapet increases unfavorable extreme values at the corner. Horizontal and rectangular grid parapets reduce extreme pressure coefficients at the high-eave corner with minimal impact on the low-eave corner, while the vertical parapet increases values at the low-eave corner. Under the conditions of this experiment, among the four parapet types, the horizontal and rectangular grid parapets have little effect on the mean wind pressure and significantly reduce the peak wind pressure, thereby helping to ensure the wind resistance safety of the photovoltaic roof. Full article

Chile stands out for its renewable energy resources and its commitment to developing green hydrogen. However, achieving cost parity with gray hydrogen remains an obstacle, mainly due to high capital costs and sensitivity to scale. This study assesses the technical and economic feasibility of green hydrogen production, using five different plants located in the Magallanes region in the south of the country as a reference. The model integrates a detailed framework of wind generation, PEM electrolysis, compression, and high-pressure storage subsystems, as well as a stochastic economic layer that combines the CAPEX, NPV, and LCOH assessments using Monte Carlo simulations. It also incorporates real-world capacity distributions and probabilistic fluctuations in systems. A sensitivity analysis confirms production scale as the main factor affecting profitability, with a break-even threshold of 0.5 MW. The results show that the LCOH decreases from 7.1 USD to 3.4 USD/kgH₂ as capacity increases. The analysis reveals that only 23.88% of small-scale configurations yield positive NPV, underscoring the need for scaling to achieve economic viability. Full article

Because of concentrated connection damage, the impact of sequential hazards on CLT shear wall systems is much more severe than that on traditional concrete and steel structures considering ductile component behaviors. The present paper evaluated the dynamic response of CLT wall structures in wind-only and sequential seismic–wind scenarios and compared the structural dynamic responses and damage levels of different CLT wall systems. The structural models were established separately based on an SOM benchmark structure, a SOFIE project three-story CLT shear wall structure, and a PT CLT wall platform structure from the NHERI Tall Wood project. The equivalent fluctuating wind load was calculated with the ASCE 7 average wind speed, the reference ESDU wind profile, calibrated wind pressure distribution, and simulated fluctuation from the NatHaz Online Wind Simulator. The sequential load was applied to the structural models in the order of seismic excitation, resting time, and then dynamic wind load. The dynamic responses of different CLT wall structures were compared among loading scenarios with increasing seismic and wind intensities. The wind-excited peak story displacement and acceleration for both CLT structures were significantly magnified in the sequential seismic–wind scenarios compared with the wind-only scenarios. The simulation results indicated that the sequential seismic–wind scenarios caused significant acceleration in damaged connections for the conventional CLT shear wall structure. The PT CLT wall structure had minor displacement and acceleration, which were linear to the wind loading factors. For the conventional CLT shear wall structure, the magnification of the acceleration was found to have a strong correlation with the natural frequencies of the damaged structure. This study demonstrated that the wind responses of the PT wall structures were in a safe range after the seismic event, and conventional CLT wall structures need to be re-evaluated under sequential scenarios for structural resilience assessment. Full article

Camellia oleifera, a woody oil crop unique to China, plays a crucial role in alleviating the global pressure of edible oil supply and maintaining ecological security. However, it remains challenging to accurately forecast Camellia oleifera yield in complex landscapes using only remote sensing data. The aim of this study is to develop an interpretable deep learning model, namely Shapley Additive Explanations–guided Attention–long short-term memory (SALSTM), for estimating Camellia oleifera yield by integrating an improved spectral bloom index and environmental parameters. The study area is located in Hengyang City in Hunan Province. Sentinel-2 imagery, meteorological observation from 2019 to 2023, and topographic data were collected. First, an improved spectral bloom index (ISBI) was constructed as a proxy for flowering density, while average temperature, precipitation, accumulated temperature, and wind speed were selected to represent environmental regulation variables. Second, a SALSTM model was designed to capture temporal dynamics from multi-source inputs, in which the LSTM module extracts time-dependent information and an attention mechanism assigns time-step-wise weights. Feature-level importance derived from SHAP analysis was incorporated as a guiding prior to inform attention distribution across variable dimensions, thereby enhancing model transparency. Third, model performance was evaluated using root mean square error (RMSE) and coefficient of determination (R²). The result show that the constructed SALSTM model achieved strong predictive performance in predicting Camellia oleifera yield in Hengyang City (RMSE = 0.5738 t/ha, R² = 0.7943). Feature importance analysis results reveal that ISBI weight > 0.26, followed by average temperature and precipitation from flowering to fruit stages, these features are closely associated with C. oleifera yield. Spatially, high-yield zones were mainly concentrated in the central–southern hilly regions throughout 2019–2023, In contrast, low-yield zones were predominantly distributed in the northern and western mountainous areas. Temporally, yield hotspots exhibited a gradual increasing while low-yield zones showed mild fluctuations. This framework provides an effective and transferable approach for remote sensing-based yield estimation of flowering and fruit-bearing crops in complex landscapes. Full article

The structural characteristics of open-circuit wind tunnels result in internal static pressure instability, which can affect the accuracy of wind pressure coefficient measurements on rigid models of low-rise buildings. To address this issue, a Pitot tube and an ESP electronic pressure scanning system were used to collect data on reference static pressure variation and wind pressure on the roof of a low-rise building under Class B wind terrain and different temperature conditions. The results indicate that the reference static pressure decreases with increasing temperature and is significantly influenced by external airflow disturbances at the beginning of the experiment, and it tends to stabilize approximately 5 min after the wind tunnel is activated. The probability density of reference static pressure under different conditions mostly follows a Gaussian distribution, although a few samples exhibit heavy-tailed or skewed fluctuations. The sliding standard deviation and coefficient of variation of the reference static pressure are both relatively small, but occasional samples show extreme fluctuations. It is recommended to apply filtering techniques or repeated measurements to reduce experimental errors. At a wind direction angle of 0°, the fluctuating wind pressure coefficients on the roof calculated using reference static pressures from different samples exhibit good consistency. The average mean relative error of the fluctuating wind pressure coefficients across roof zones I–VIII was 3.71%, which is within an acceptable range. The research findings provide a useful reference for reducing result errors in wind pressure tests conducted in open-circuit wind tunnels. Full article

Turbulent flow separation over lifting surfaces impacts high-lift systems such as aircraft, wind turbines, and turbomachinery, and contributes to noise, lift loss, and vibrations. Accurate detection of flow separation is therefore essential to enable active control strategies and to mitigate its adverse effects. Several machine learning models are compared for detecting flow separation from surface pressure fluctuations. The models were trained on experimental data covering various airfoils, angles of attack (0°–23°), and Reynolds numbers, with ${\mathrm{Re}}_c=0.8–4.5\times {10}^6$. For supervised learning, the ground-truth binary labels (attached or separated flow) were derived from static pressure distributions, lift coefficients, and the power spectral densities of surface pressure fluctuations. Three machine learning techniques (multilayer perceptron, support vector machine, logistic regression) were utilized with fine-tuned hyperparameters. Promising results are obtained, with the support vector machine achieving the highest performance (accuracy 0.985, Matthews correlation coefficient 0.975), comparable to other models, with advantages in runtime and model size. However, most misclassifications occur near separation onset due to gradual transition, suggesting areas for model refinement. Sensitivity to database parameters is discussed alongside flow physics and data quality. Full article

In our previous study, the transition behavior of a flared cone–swept fin configuration was investigated under an angle of attack (AoA) of 0°. To further explore the role of AoA in complex three-dimensional geometries with strong fin–body interactions, wind tunnel experiments were conducted at Ma = 9.3, Re = 1.36 × 10⁷/m, with AoA ranging from −6° to 6°. Global surface temperature distributions were obtained using temperature-sensitive paint (TSP), while localized heat flux and pressure fluctuations were captured using thin-film thermocouples and high-frequency pressure sensors. The results show that varying AoA shifts the location of high heat flux between the upper and lower surfaces of the flared cone and induces a switch from streamwise to separation vortices. The windward side exhibits stronger disturbance responses than the leeward side. The junction region between the flared cone and the near-horizontal surface is highly sensitive to AoA variations, consistently exhibiting pronounced second-mode instabilities. These findings provide experimental support for understanding transition mechanisms under the combined effects of shock/boundary layer interaction (SBLI), crossflow, and adverse pressure gradients, with implications for transition prediction and thermal protection system design. Full article

The high-proportion integration of renewable energy sources, represented by wind power and photovoltaics, into active distribution networks (ADNs) can effectively alleviate the pressure associated with advancing China’s dual-carbon goals. However, the high uncertainty in renewable energy output leads to increased system voltage fluctuations and localized voltage violations, posing safety challenges. Consequently, research on optimal dispatch for ADNs with a high penetration of renewable energy has become a current focal point. This paper provides a comprehensive review of research in this domain over the past decade. Initially, it analyzes the voltage impact patterns and control principles in distribution networks under varying levels of renewable energy penetration. Subsequently, it introduces optimization dispatch models for ADNs that focus on three key objectives: safety, economy, and low carbon emissions. Furthermore, addressing the challenge of solving non-convex and nonlinear models, the paper highlights model reformulation strategies such as semidefinite relaxation, second-order cone relaxation, and convex inner approximation methods, along with summarizing relevant intelligent solution algorithms. Additionally, in response to the high uncertainty of renewable energy output, it reviews stochastic optimization dispatch strategies for ADNs, encompassing single-stage, two-stage, and multi-stage approaches. Meanwhile, given the promising prospects of large-scale deep reinforcement learning models in the power sector, their applications in ADN optimization dispatch are also reviewed. Finally, the paper outlines potential future research directions for ADN optimization dispatch. Full article

Ground roughness is investigated for its influence on the propagation of wind turbine noise by using a proposed multiple scattering theory to predict the reflection of sound waves from a deterministic distribution of hemispheres. By using a distribution of hemispheres as an approximation for a realistic rough ground, a semi-analytical formulation for the reflected sound pressure is possible. Experiments are conducted within the University of Hull’s anechoic chamber and the results are compared against predictions from the proposed theory. Good agreement between the results is shown. The proposed multiple scattering theory also gives results consistent with a three-dimensional boundary element method, while having significantly shorter computation times and smaller memory requirements. Furthermore, results remain accurate up to the point where the radii of the hemispheres are comparable to the wavelengths of interest, which means that the scattering effect can be investigated more completely. When the proposed theory was applied to the unique source–receiver geometry of a wind turbine and a human height receiver, the excess attenuation calculated over an array of receivers showed significant fluctuations in sound pressure which were attributed to the ground roughness. Further works aim to incorporate weak refraction effects and ground absorption to analyze the relative influence of different parameters. Full article

Non-contact acoustic detection methods for blades have gained significant attention due to their advantages such as easy installation and immunity to mechanical noise interference. Numerical simulation investigations on the aerodynamic noise mechanism of blade erosion provide a theoretical basis for acoustic detection. However, constructing a three-dimensional erosion model remains a challenge due to the uncertainty in external natural environmental factors. This study investigates a leading-edge erosion calculation model for wind turbine blades subjected to rain erosion. A rain erosion distribution model based on the Weibull distribution of raindrop size is first constructed. Then, the airfoil modification scheme combined with the erosion distribution model is presented to calculate leading-edge erosion mass. Finally, for a sample National Renewable Energy Laboratory 5 MW wind turbine, a three-dimensional erosion model is investigated by analyzing erosion mass related to the parameter of the attack angle. The results indicate that the maximum erosion amount is presented at the pressure surface near the leading edge, and the decrease in erosion on the pressure surface is more rapid than the suction side from the leading edge to the trailing edge. With an increase in the attack angle, the erosion on the pressure side is more severe. Furthermore, a separation vortex appears at the leading edge of the airfoil under computational non-uniform erosion. For aerodynamic noise, a larger sound pressure level with significant fluctuation occurs at 400–1000 Hz. Full article

This article investigates the effects of roof opening and closure conditions on the mean and fluctuating wind pressure coefficient of the roof surface through rigid model wind tunnel tests and further explores the non-Gaussian characteristics of wind pressure (skewness, kurtosis, and wind pressure probability density) under the two conditions. Then, based on the non-Gaussian characteristics under two working conditions, this paper constructs a Hermite moment model to solve the peak factor of the roof surface to evaluate the impact of roof opening and closure on the most unfavorable extreme wind pressure. The research results show that under the two working conditions of roof opening and closure, the windward leading edge’s mean and fluctuating wind pressure coefficients change most significantly, leading to an increase in the degree of flow separation at the windward leading edge. This causes the skewness, kurtosis, and probability density function of the wind pressure at the windward leading edge of the roof to deviate significantly from the standard Gaussian distribution, exhibiting strong non-Gaussian characteristics. Meanwhile, based on the Hermite moment model, it is found that the peak factor of most measuring points is concentrated between 3.5 and 5.0 under both roof opening and closure conditions, significantly higher than the recommended value of 2.5 in GB 50009-2012. In addition, under roof opening, the most unfavorable negative pressure coefficient is −4.54, and the absolute value of its most unfavorable negative pressure extreme is 1.3% higher than the roof opening closure condition. Full article

Measuring the airtightness of high-rise buildings presents significant challenges due to the effects of wind and thermal lift (stack effect). Small indoor/outdoor temperature differences, combined with the building’s height, can create substantial natural pressure differences on the building envelope, while winds induce pressure fluctuations. The international standard ISO 9972 provides insufficient guidelines for dealing with these high and fluctuating natural pressure differences. In addition, it is crucial to achieve a uniform internal pressure distribution during the test. This paper discusses the airtightness testing of high-rise buildings up to 125 m tall using portable blower door devices, following the “airtightness measurement of high-rise buildings” Passive House guideline. Differential pressure sensors were placed on the ground and top floors to record the effects of wind and thermal lift, and additional sensors helped to achieve a uniform pressure distribution within the building. The readings from the ground and top floors ensured full depressurization and pressurization during testing. The setup of the measuring fans, mainly on the ground floor, was supplemented with additional fans on higher floors to maintain pressure uniformity within a 10% tolerance. To be able to conduct a multi-point regression test, it is recommended to limit the product of the indoor/outdoor temperature difference and building height to ≤1250 mK and to achieve a coefficient of determination of 0.98 or higher, a wind speed ≤ 3 Beaufort. The study concludes that an airtight building envelope and larger internal flow paths, such as stairwells and elevator shafts, simplify the measurement. Full article