Search Results (1,364)

As the new energy strategy progresses, desert, Gobi, and wasteland areas have become key areas for photovoltaic (PV) development, inevitably bringing new environmental challenges. Although PV power stations act as obstacles with some wind and sand control effects, aeolian erosion remains a problem, especially in localized areas where erosion intensifies. To address this issue, this study uses the PV power station layout in the semi-arid wind and sand region of Yudaokou, Hebei, as a case study. Using computational fluid dynamics (CFD) numerical simulations, a combined layout of PV panels and sand barriers is proposed. It is first assumed that this combined layout improves wind protection compared to photovoltaic arrays. The impact of different sand barrier configurations on the airflow field is analyzed to explore their role in controlling aeolian erosion. By analyzing the airflow field, areas of intensified and potentially intensified aeolian erosion are identified. Based on this, sand barriers are strategically placed in key protective zones on the windward side of the PV array, and the combined layout of PV panels and sand barriers is optimized to improve aeolian erosion control effectiveness and promote the sustainable development of PV power stations. The results indicate that PV panels significantly reduce wind speed by altering local airflow and flow patterns, with the impact primarily concentrated in the first 3 to 4 rows on the windward side of the PV array. By establishing sand barriers beneath the PV panels on the windward side, aeolian erosion can be effectively reduced, with the effect on the airflow field primarily occurring within the 0–0.3 m height above the ground. Continuously establishing sand barriers up to the third row of PV panels effectively reduces wind speed, with further extension not significantly improving wind protection, indicating that the third row of PV panels serves as the critical point for sand barrier establishment. This configuration provides the ideal layout for achieving effective protection and offers theoretical and practical guidance for improving the layout of combined PV power stations. Comprehensive analysis suggests that the optimized configuration of PV arrays and sand barrier layout effectively controls aeolian erosion, with the Model 3, which places sand barriers up to the third row of PV panels, ensuring efficient resource utilization. This study offers a practical approach to reducing damage from wind and sand by optimizing the layout of sand barriers and PV panels, thereby providing important guidance for the sustainable development of PV power stations in arid areas. Full article

Addressing the issues of the complex mechanical responses and significant spatial effects of asymmetric large-span cable-stayed steel box girder bridges with shared public-rail traffic under operational loads (live load, static wind, and structural temperature differences), this paper uses the Lijiatuo Yangtze River Double-Line Bridge on Chongqing Metro Line 18 as the engineering background to construct multi-scale finite element models for the entire bridge and the closure segment, and validates them against GNSS displacement and strain monitoring data from the actual bridge. The study shows that the spatiotemporal asymmetry of operational live loads induces significant lateral bias effects in the main bridge, resulting in reverse displacements in the mid-span section, and with stress distributions characterized by “oscillation in the side spans and concentration in the mid-span.” The study also shows that, under static wind loads, the bridge’s lateral displacement approximately increases linearly with wind speed, and the mid-span response is higher than that of the side spans, showing significant spatial sensitivity to wind loads. Finally, the study shows that, although the system temperature difference causes small overall displacements, it still induces symmetrical lateral deformations and local stress concentrations near the closure segment. Local refined analyses further reveal the displacement distribution mechanism of the closure segment under operational loads. The health monitoring data agree well with the simulation results, validating the reliability of the numerical model. The research systematically reveals the spatial mechanical behavior of such bridges under operational loads, providing theoretical basis and engineering references for the design optimization and safety monitoring of similar asymmetric cable-stayed bridges. Full article

With the relentless expansion of installed capacity in renewable energy (RE) sources, including wind and photovoltaic power, the operational landscape of the power system has witnessed a substantial surge in uncertainty and complexity. The conventional unit commitment (UC) model falls short when it comes to addressing the challenges posed by a high proportion of RE integration and the collaborative involvement of multiple entities, especially within the electricity market framework. UC now faces a dual challenge: it must not only grapple with the pronounced uncertainty on the source–load side but also harmonize the operational characteristics of emerging entities, such as independent energy storage (ES) systems and virtual power plants. All of this must be achieved while strictly adhering to market regulations and grid safety constraints. To tackle these issues, this paper proposes an intelligent scheduling model built upon a composite neural network. This model enables real-time optimization of scheduling for thermal power, renewable energy, and ES systems through multi-agent collaboration. By doing so, it effectively mitigates the uncertainty associated with RE sources and enhances the safety, economic efficiency, and flexibility of the power system. Full article

This study presents an analysis of selected approaches to transforming the Polish power system towards a net-zero greenhouse gas (GHG) emission economy by 2060. The generation-side system models primarily comprise renewable energy sources (RES), supported by nuclear power plants. Two system balancing scenarios were examined: Model G, based on biomethane-fired gas turbines and electrolysers utilising surplus energy; and Model H, which relies primarily on reversible fuel cells (RFCs) operating in a Power-to-Power configuration. Both models were considered under two demographic projections for Poland in 2060: maintaining the current population level (100%) and a decline to 71%. Simulations were performed with an hourly time step over a nine-year period, starting from 2060, using weather data from 2015 to 2023. The total electricity demand in the analysed scenarios ranges from 352 to 542 TWh/year, representing 2.1–3.2 times the current level. The proposed systems include 64 GW of onshore wind capacity, 33 GW of offshore wind, 136 GW of PV, 10 GW of nuclear generation, and extensive storage systems for electricity, heat, and gases (biomethane and hydrogen). In Model G, biomethane and hydrogen storage play a crucial role, requiring storage capacities of 5.8–7.5 billion Nm³ for biomethane and 6.2–7.0 billion Nm³ for hydrogen. In Model H, long-term storage relies on hydrogen reservoirs (approximately 12.5 billion Nm³) integrated with RFC units. The results demonstrate that the choice of architecture dictates the scale and technical requirements of the storage infrastructure. Notably, hydrogen serves as an effective energy storage medium, enabling the elimination of peak gas turbines from the system. Consequently, biomethane resources can be redirected to support the decarbonisation of other sectors of the economy. Full article

Under extreme fault conditions or during maintenance restarts, DC collection wind farms may experience a total blackout due to protective isolation. Addressing the black-start challenges arising from the unidirectional power flow structure and weak damping characteristics inherent to DC step-up collection wind farms, this paper proposes a sequential black-start control scheme predicated on grid-source coordination. A representative topology and an equivalent black-start model of the DC collection system are established to analyze the start-up mechanism and to design an active voltage build-up strategy with virtual impedance for the grid-side Modular Multilevel Converter (MMC). Meanwhile, generator-side permanent-magnet direct-drive wind turbines exploit their self-excitation capability and optimized pitch control to realize islanded self-bootstrapping and stable rotational speed. In addition, we develop a two-stage soft cut-in strategy that combines open-loop voltage scanning for pre-synchronization with closed-loop constant-current ramping of DC/DC converters, together with control logic for sequentially connecting multiple units to the DC grid. Simulation results show that the proposed approach smoothly restores the system from a zero-energy state to the rated operating point without external power sources, confirming the feasibility of full-farm start-up using the grid-side converter station and unit self-bootstrapping. Full article

Inflatable structures have attracted increasing attention in recent years due to their light weight, translucency, rapid assembly or disassembly, mobility, and self-cleaning performance. Meanwhile, their flexible characteristics and low-damping behavior render the structures prone to significant deformation and vibration under wind and snow loads and may even lead to structural failure. Therefore, numerous researchers have conducted in-depth investigations into the mechanical response of such structures under wind and snow loads. However, existing studies on inflatable structures subjected to wind and snow loads have mainly focused on an air-supported form, and the mechanical behavior of inflatable ribbed arch structures has not yet been sufficiently investigated. To investigate the mechanical behavior and deformation patterns of inflatable ribbed arch structures subjected to wind and snow loads, static tests were conducted on three specimens with varying spans, heights, and cable arrangements. Following inflation to an internal pressure of 250 kPa and preloading with the tarpaulin weight, the wind load and snow load were converted to the equivalent concentrated loads and applied in five incremental stages. Displacement monitoring points (DMPs) were tracked using a total station. Under the wind load, a consistent wind-induced deformation pattern was observed across specimens characterized by inward displacement in Region I, upward displacement in Region II, and negligible change in Region III. The maximum horizontal displacements of Specimens A, B, and C were 76 mm, 140 mm, and 249 mm, respectively. Under snow load, the upper sections of all three specimens experienced significant downward displacement, while both sides demonstrated a slight tendency for outward expansion and upward lift. The maximum vertical displacements of Specimens A, B, and C were −27 mm, −233 mm, and −255 mm, respectively. The findings of this study provide deeper insights into the mechanical behavior of inflatable arch structures under wind and snow loads and can serve as a valuable reference for their design and optimization. Full article

Offshore wind energy offers substantial potential. However, its inherent intermittency leads to the frequent occurrence of offshore wind energy droughts, which pose challenges to electricity system stability. Mitigation measures aim to reduce the number, duration, or impacts of such droughts. Among the different mitigation approaches, supply-side strategies act directly on wind power generation at the wind farm level. Nevertheless, the effectiveness of supply-side mitigation strategies remains poorly understood. This study addresses these gaps by systematically quantifying the potential of three supply-side mitigation strategies: (i) spatial diversification of wind farm locations, (ii) advances in wind turbine technology, and (iii) reductions in downtime and wake losses, to minimize the number and duration of wind energy droughts across 40 key exclusive economic zones (EEZ) worldwide. Hourly, daily, and monthly drought characteristics for both moderate and extreme offshore wind energy droughts are analyzed using wind data from the ERA5 reanalysis for the period 1993–2022. The results show that spatial diversification across multiple sub-regions is the most effective strategy for mitigating offshore wind energy droughts at the EEZ scale. In addition, the effectiveness of all mitigation strategies exhibits pronounced scale-dependent limitations, which are most evident at the monthly time scale. Overall, this study provides a robust basis for energy-policy decisions and highlights the importance of supply-side mitigation for enhancing the reliability of future electricity systems. Full article

With the increasing penetration of inverter-based resources (IBRs), modern power systems are experiencing undesirable dynamics, such as sub-synchronous oscillations in weak grids. Conventional PI control schemes, however, exhibit limited robustness against nonlinearities arising from varying operating points in weak grids, leading to instability. To address this challenge, we propose a robust controller for the outer loop of grid-side converters in IBRs based on robust μ-synthesis control theory. Specifically, this paper utilizes μ-synthesis to handle linearized model parameters associated with operating-point variations. The proposed controller replaces the PI controllers in the outer loop while retaining the established dq-frame control philosophy. Furthermore, during controller synthesis, the controller is optimized with a 2-by-2 multi-input multi-output structure to explicitly account for cross-coupling effects between the d- and q-axes. Finally, the proposed controller was validated using electromagnetic transient simulations of a detailed type-IV wind farm model implemented in MATLAB/Simulink R2025a, and its performance was compared with that of a conventional PI-based outer control loop. The wind farm was tested under very weak grid conditions, and the proposed controller demonstrated robust stability against varying operating points by providing superior damping performance. Full article

This systematic review synthesizes passive and passive-first cooling strategies for greenhouses in hot–arid climates, organizing evidence across four domains: Airflow & Ventilation, Shading & Radiative Control, Thermal Storage & Ground Coupling, and Structural Design & Geometry. Drawing on the project corpus, we analyze 10–13 distinct techniques including ridge and side natural ventilation, windcatchers and solar chimneys, external shade nets, NIR-selective and transparent radiative-cooling films, and dynamic PV shading; earth-to-air heat exchangers (EAHE/GAHT), rock-bed sensible storage, phase-change materials (PCMs), and sunken or buried envelopes; as well as roof slope and shape, span number, and orientation. Across studies, cooling outcomes are reported as peak or daytime indoor air temperature reductions, defined relative either to outdoor conditions or to a control greenhouse, with the reference frame and temporal aggregation specified in the synthesis. Typical outcomes include ≈3–7 °C daytime reduction for optimized ventilation, ≈2–4 °C for shading and spectral covers while preserving PAR, ≈5–7 °C intake cooling for EAHE with winter pre-heating, and up to ≈14 °C peak attenuation for rock-bed storage under favorable conditions. Structural choices consistently amplify these effects by sustaining pressure head and limiting thermal heterogeneity. Performance is strongly context-dependent—governed by wind regime, diurnal amplitude, dust and UV exposure, and crop-specific light and temperature thresholds—and the most robust results arise from stacked, site-specific designs that combine skin-level radiative rejection, buoyancy-supportive geometry, and ground or latent buffering with minimal active backup. Smart controllers that modulate vents, shading, and targeted fogging or fans based on VPD or temperature differentials improve stability and reduce water and energy use by engaging actuation only when passive capacity is exceeded. We recommend standardized composite metrics encompassing temperature moderation, humidity stability, PAR availability, and water and energy use per unit yield to enable fair cross-study comparison, multi-season validation, and policy adoption. Collectively, the synthesized techniques provide a practical palette for improved greenhouse climate management under hot and arid conditions. Full article

In Shenzhen, a high-density city facing severe land scarcity, the proliferation of compact primary school campuses poses significant challenges to the outdoor wind environment, which is crucial for outdoor thermal comfort in a hot–humid climate. This study employs Computational Fluid Dynamics (CFD) to systematically evaluate wind comfort across a range of high-density primary school layouts. Typical design proposals are classified and analyzed based on three key planning aspects: education building forms, courtyard openness, and sports field configuration. Wind comfort area ratio and static wind zone area ratio are adopted as key performance indicators to evaluate outdoor wind performance. The findings demonstrate that decentralized teaching building forms, multi-courtyard layouts with openings oriented towards the prevailing summer wind, and juxtaposed sports field placement significantly enhance outdoor ventilation and comfort. Additionally, positioning the main entrance on the windward side and incorporating elevated voids or terraces to form coherent ventilation corridors are effective design strategies. This research provides theoretical guidance for designing high-density school campuses in hot–humid southern China. Full article

Leading-edge erosion of wind turbine blades caused by repeated raindrop impingement can significantly reduce power output and increase maintenance costs. This study develops a rain erosion atlas for Japan over 11 years from 2006 to 2016 based on the CRIEPI-RCM-Era2 dataset. The NREL 5 MW, DTU 10 MW, and IEA 15 MW wind turbines were employed to evaluate the incubation time (erosion onset time) of commercial polyurethane-based coating at the blade tip. Erosion progression was simulated using an empirical damage model that relates raindrop impingement and impact velocity to the incubation time. The rain erosion atlas reveals a clear correlation between wind turbine size and erosion risk: the NREL 5MW turbine shows an incubation time of 3–12 years, the DTU 10MW turbine 1–4 years, and the IEA 15MW turbine 0.5–2 years. Shorter incubation times are observed on the Pacific Ocean side, where annual precipitation is higher than on the Sea of Japan side. Additionally, the influence of coating degradation due to ultraviolet radiation was assessed using solar radiation data, revealing a further reduction in incubation time on the Pacific Ocean side. Finally, the potential of erosion-safe mode operation was examined, demonstrating its effectiveness in alleviating erosion progression. Full article

Gravity storage has become an important development direction of physical energy storage technology due to its high energy conversion efficiency and low site selection difficulty. However, the existing gravity energy storage systems based on pure mechanical transmission still have shortcomings, such as low reliability and high operation and maintenance costs, which seriously limit their promotion. To overcome this obstacle, this paper proposes a linear-motor direct-drive gravity energy storage system (LMDD-GESS) with a simpler structure and higher energy conversion efficiency. The cableless flux-switching permanent magnet linear motor (SFPMLSM) is used to replace the traditional wire rope or chain transmission mechanism and fundamentally eliminates frictional losses. Firstly, in terms of the SFPMLSM, the thrust fluctuation is suppressed through the integrated design of the permanent magnet and armature winding on the mover side and the optimization of the end magnetic blocks. In terms of the system grid connection, the double-closed-loop PI control of the machine side and the three-level coordination strategy of the grid side are established, and the in-phase carrier PWM modulation and harmonic feedback compensation algorithm are used to improve the quality of grid connection. The speed curve optimization and multi-machine-switching scheme are designed to achieve smooth power output. The simulation results show that the proposed system significantly improves the operation efficiency and power output stability and provides a reliable gravity energy storage solution for the high proportion of new energy grids. Full article

To investigate the hypersonic boundary layer transition over complex three-dimensional configurations, this study conducted an experiment using infrared thermography, Rayleigh scattering visualization, and high-frequency pressure sensors in a Mach 6 Ludwieg wind tunnel. The infrared results indicate that increasing the Reynolds number promotes boundary layer transition on the model surface. Spectral analysis reveals a high-frequency peak centered at 250 kHz on the finless side of the windward surface. Comprehensive analysis indicates this represents high-frequency secondary instability triggered by the traveling crossflow mode in its nonlinear phase. On the finless side of the leeward surface, a typical Mack second-mode high-frequency instability amplification process is observed within the 140–280 kHz frequency band. Additionally, the spectrum results for the fin–cone junction became more complex. On the windward side, the primary energy concentration in the junction zone is observed between 80 and 200 kHz, with calculated wave packet velocities higher than those on the finless side. Wavelet analysis reveals that low-frequency modes are amplified first and gradually excite high-frequency components, with significant modal coupling appearing in the high-frequency region of the bicoherence. The leeward fin–cone junction exhibits dual-band characteristics at 60–120 kHz and 180–260 kHz, demonstrating stronger intermodal interactions. Both the windward and leeward surfaces of the fin show low-frequency transverse flow-like modes around 70–180 kHz. The spectral results for the windward and leeward sides are largely consistent, with only slight differences in amplitude levels and saturation positions. Full article

The Doubly fed induction generator (DFIG) occupies an important position in current wind turbines. With the continuous increase in wind power penetration, its Low-voltage ride-through (LVRT) capability becomes more important. When facing dynamic faults, traditional control strategies have the problems of slow response speed and insufficient control accuracy, which makes it difficult to meet the ride-through requirements. This article proposes a coordinated control strategy for LVRT of the DFIG based on Model predictive current control (MP-CC) combined with a crowbar circuit. This method first establishes a mathematical model of the doubly fed wind turbine and then uses the rolling optimization and constraint-handling capabilities of model predictive control to achieve rapid dynamic adjustment of the rotor current and grid-side power. The simulation results show that the optimized model predictive control strategy can more effectively control the rotor over current and make the system have better stability, which can effectively improve the LVRT capability of the system and is of great significance to the current rapidly developing wind power generation technology. Full article

With the aim of mitigating the impact of wind power integration and source-load-side uncertainties on an integrated energy system, we initially employed the Monte Carlo simulation in this study to randomly generate multiple wind power output/load scenarios in accordance with probability distribution functions. Additionally, we proposed a two-stage optimization method. In the first stage of our study, an enhanced African vulture optimization algorithm was applied to perform multi-objective optimization targeting fuel cost and carbon emissions across various scenarios, thereby solving the Pareto frontier to obtain multiple candidate solutions. In the study’s second stage, comprehensively considering fuel cost, carbon emission, and wind power penetration rate, evidential reasoning was utilized to determine the optimal operation strategy among the candidates. Finally, a combined heat and power system composed of the IEEE 30-bus system and a 32-node heating network was simulated. The results demonstrate that this decision-making approach can effectively reflect the merits of candidate solutions, thus validating the feasibility of the designed research methodology. Full article