Search Results (39)

Extreme weather conditions impose significant challenges on distribution network inspection because UAV flight safety, energy consumption, vehicle mobility, and task coverage are strongly coupled under wind disturbances. To improve inspection efficiency and operational robustness, this paper proposes a weather-aware asynchronous vehicle–UAV cooperative scheduling method based on bi-level MODDPG–NSGA-II optimization. First, a dynamic wind field model and a wind-sensitive UAV energy model are established to describe the effects of background wind, vertical wind shear, and local gust disturbances on UAV motion and state-of-charge evolution. Then, an asynchronous vehicle–UAV collaboration mechanism is developed, allowing the vehicle to move toward downstream parking sites after UAV deployment while UAVs perform inspection and cross-site recovery under rendezvous and energy safety constraints. On this basis, a bi-level optimization framework is constructed, in which NSGA-II searches global coordination parameters and MODDPG learns adaptive multi-UAV scheduling policies in continuous decision spaces. Controlled wind-factor experiments show that, with the task scale fixed at 52 inspection tasks, the proposed method maintains 100% task coverage under 0–10 m/s wind conditions. As the reference wind speed increases from 0 m/s to 10 m/s, the mission completion time increases from 40.97 min to 70.24 min, while the minimum residual SOC decreases from 50.32% to 13.82%, which remains above the predefined safety threshold. Repeated stochastic trials and statistical significance analysis further indicate that the proposed method achieves shorter mission time and more stable task coverage than representative baselines under the same experimental conditions. The scope of this study is simulation-level validation; real-world flight tests and hardware-in-the-loop verification will be further investigated in future work. Full article

Compound and consecutive extreme events are increasingly understood as key contributors to climate risk, as their interactions can intensify impacts beyond those produced by individual hazards alone threatening the long-term sustainability of regional infrastructure. Compound coincident events involve multiple climate drivers or hazards that occur simultaneously or in close temporal proximity, exhibiting overlapping spatial and temporal characteristics. For assessing multi-hazards, information on critical thresholds of the events investigated (extreme precipitation and wind gusts in the presented study) is key, as is the time frame needed to determine the probability of event B after an event A. As this data is location-specific, stakeholder integration provides a potential tool for gathering this information to enable socially robust disaster risk management. The presented study displays a potential interdisciplinary approach to how multi-hazards and their occurrence can be investigated locally. Therefore, stakeholder integration is combined with climate model output and a copula-based analysis of compound coincident and consecutive extreme daily wind and precipitation events for the Salzburg region under different climate change scenarios (SSP1-2.6, SSP5-8.5). Through stakeholder integration, relevant thresholds and potential time frames were identified. Our findings indicate that the thresholds critical to the considered assets (properties, transport, energy) are well aligned between different stakeholders; however, the time frame of increased vulnerability due to a previous event differs strongly between them. Compared to the baseline scenarios, the ranges within the climate model used for rainfall and wind speed intensity under SSP1-2.6 and SSP5-8.5 scenarios are examined, and, for rainfall, have expanded to greater values for both compound coincident and consecutive events, highlighting challenges and future research needs for sustainable adaptation and regional policy. Full article

Turbulent wind conditions pose significant challenges to the blade structural reliability of small wind turbines. Different from the authors’ previous work, which mainly focused on the output characteristics of the same 5 kW prototype under variable inflow conditions, this study combines field-test observations with numerical simulations to further investigate the blade structural dynamic responses of a 5 kW variable-pitch wind turbine under both uniform inflow and extreme wind conditions. Owing to the unique pitch-regulation mechanism of the proposed turbine, two pitch-control modes, namely conventional power-limited pitch control and active stall pitch control, are comparatively analyzed to clarify their effects on blade load, stress, and displacement responses. The results indicate that, under uniform inflow conditions, stresses are concentrated near the leading edge of the blade mid-span, while the maximum displacement occurs at the blade tip. Both stress and displacement decrease with increasing conventional pitch angle. Under extreme wind conditions, increasing gust intensity causes a nonlinear growth in blade loads and aggravates blade structural response. During active stall pitch control, the load distribution pattern is generally consistent with that under conventional pitch control, whereas the blade structural response first decreases and then increases as the pitch angle is adjusted toward negative values. Under uniform inflow at the rated wind speed of 11 m/s, the blade-tip maximum displacement decreased from 56.51 mm under the +6° power-limited/reference pitch condition to 48.42 mm under the −6° active-stall-related pitch condition, corresponding to a reduction of approximately 14.3%. These results provide a useful reference for the blade structural design and control optimization of distributed small wind turbines under complex inflow conditions. Full article

Knowledge of the maximum gust expected over a period of years is essential for offshore structures design. Because long records of gust speed are not normally available, maximum gusts have traditionally been estimated by multiplying the maximum expected hourly or 10 min wind speed by a gust factor. That calculation ignores the possibility that the highest gust might not occur in the hour with the highest mean wind speed. A similar problem arises in the estimation of the maximum expected individual wave height. By analogy with the accepted method of calculating maximum wave heights, we demonstrate how maximum gusts can be calculated from time series of average wind speed and wind gust distributions. We used measurements from the IJmuiden meteorological mast offshore from The Netherlands to find wind gust distributions. The IJmuiden data is particularly useful for studying gusts because four years of measurements were made at a sampling frequency of 4 Hz. Those distributions were used to predict extreme values of gusts in a storm using methods similar to those used in wave height calculations. The resulting extreme values closely matched extreme values calculated directly from the measured maximum gusts in each storm. The methods described here can calculate extreme gust speeds more accurately than the methods currently in use. Full article

To address the scientific gap concerning optimal urban wind turbine morphology, this work presents an experimental performance comparison between two small-scale wind turbine designs: a conventional three-blade horizontal-axis wind turbine (HAWT) and a duct-equipped Ayanz-inspired screw-blade turbine. Both configurations were tested in a controlled wind tunnel under steady and transient wind conditions, including synthetic gusts designed to emulate urban wind patterns. The analysis focuses on power output, aerodynamic efficiency (via the power coefficient $C_P$), dynamic responsiveness, and integration suitability. A key novelty of this study lies in the full-scale experimental comparison between a non-conventional Ayanz screw-blade turbine and a standard three-blade turbine, since experimental data contrasting these two geometries under both steady and gusty urban wind conditions are extremely scarce in the literature. Results show that while the three-blade turbine achieves a higher $C_P$ peak and greater efficiency near its optimal operating point, the Ayanz turbine exhibits a broader performance plateau and better self-starting behavior under low and fluctuating wind conditions. The Ayanz model also demonstrated smoother power build-up and higher energy capture under specific gust scenarios, especially when wind speed offsets were low. Furthermore, a methodological contribution is made by comparing the $C_P$ vs. tip speed ratio λ curves at multiple wind speeds, providing a novel framework (plateau width analysis) for realistically assessing turbine adaptability and robustness to off-design conditions. These findings provide practical insights for selecting turbine types in variable or urban wind environments and contribute to the design of robust small wind energy systems for deployments in cities. Full article

Because wildfire spread is strongly influenced by instantaneous gusts, models that use only mean wind speed typically underestimate spread. In contrast, incorporating suppression effects often leads to overestimation. To reduce these errors, this paper newly proposes the concepts of an effective wind speed (EWS) and an EWS coefficient that jointly account for short-range forecast mean wind speed and the maximum gust from numerical weather prediction. The EWS is defined as an EWS coefficient-weighted average of the mean wind speed and maximum gust, so that the simulated perimeter matches the observed wildfire perimeter as closely as possible. Here, EWS refers exclusively to near-surface horizontal wind speed; vertical wind components are not considered. The EWS coefficient is modeled as a function of elapsed time since ignition, thereby implicitly reflecting the level of suppression resource deployment. The proposed frameworks are described in detail using time-stamped perimeters from multiple large-scale wildfires that occurred concurrently in South Korea during a specific period. On this basis, an EWS coefficient suitable for operational use in South Korea is derived. Using the derived EWS for spread prediction, the Sørensen index increased by up to 0.4 compared with predictions based on maximum gust alone. Incorporating the proposed EWS and coefficient into Korean wildfire spread simulators can improve the accuracy and robustness of predictions under extreme weather conditions, supporting safer and more efficient wildfire response. Full article

Extreme Operational Gusts (EOGs) are critical for assessing the effects of extreme winds on Wind Energy Conversion Systems (WECSs). In regions like La Ventosa, Oaxaca, Mexico—characterized by strong and frequent gusts—the performance and reliability of low-power WECSs can be severely impacted. Traditionally, EOG effects have been analyzed using mathematical models from the IEC 61400-2 standard, which assumes a symmetric gust taxonomy. However, field data have revealed inconsistencies with this model, leading to the development of new asymmetrical taxonomies, such as Manwell’s. This study presents a taxonomic characterization of EOGs in La Ventosa using 1 Hz wind speed data collected over one year (December 2017–November 2018), during which 1655 events were detected. A dedicated detection method was implemented to capture gusts with amplitudes and durations exceeding the IEC range, allowing systematic classification of previously unrecognized patterns. Based on these results, a new taxonomy and a mathematical model were developed to simulate any identified gust. These tools provide more realistic simulations for improving WECS protection under extreme conditions. The analysis shows that Manwell’s taxonomy represents 50.39% of events, the proposed classification 37.04%, and IEC 61400-2 only 12.57%, underscoring its limited applicability to high-wind sites like La Ventosa. Full article

Extreme sea conditions, particularly extreme operation gusts (EOGs), present a substantial threat to structures like floating offshore wind turbines (FOWTs) due to the intense loads they exert. In this work, we simulate EOGs and analyze the dynamic response of floating wind turbines. We conduct separate analyses of the operational state under the rated wind speed, the operational state, and the shutdown state under the EOG, focusing on the motion of the floating platform and the tension of the mooring lines of the FOWT. The results of our study indicate that under the influence of EOGs, the response of the FOWT changes significantly, especially in terms of the range of response variations. After the passage of an EOG, there are notable differences in the average response of each component of the wind turbine under the shutdown strategy. When compared to normal operation during EOGs, the shutdown strategy enables the FOWT to reach the extreme response value more rapidly. Subsequently, it also recovers response stability more quickly. However, a FOWT operating under normal conditions exhibits a larger extreme response value. Regarding pitch motion, the maximum response can reach 10.52 deg, which may lead to overall instability of the structure. Implementing a stall strategy can effectively reduce the swing amplitude to 6.09 deg. Under the action of EOGs, the maximum mooring tension reaches 1376.60 kN, yet no failure or fracture occurs in the mooring system. Full article

This paper introduces a novel pitch adjustment device applicable to small wind turbines. To validate its feasibility under high wind speeds and analyze the impact of pitch angle on the power output characteristics of small wind turbines, a prototype model was manufactured for wind tunnel experiments. Additionally, we conducted simulations to analyze the stress and displacement responses of key components under uniform airflow, shear airflow, and Extreme Operated Gust conditions. The numerical simulation results were compared with experimental results based on actual measurement points in the wind tunnel experiment, demonstrating that the simulation data accurately reflect the experimental test results, with an overall discrepancy of around 10%, thereby validating the accuracy of the load and constraint settings in the transient dynamics analysis. This study found that, as the pitch angle increased, the structural dynamic response of key wind turbine components under uniform airflow conditions exhibited a decreasing trend, which was proportional to wind speed. Under shear airflow conditions, the response of key components was positively correlated with the shear index, while Extreme Operated Gust significantly increased the amplitude of the response fluctuations. Furthermore, this research revealed that, with an increase in pitch angle, the maximum stress value of the gear under uniform airflow conditions decreased from 27.42 MPa to 7.64 MPa, a reduction of 72.1%. Under shear airflow conditions, the root stress of the gear decreased from 14.441 MPa to 8.879 MPa, a reduction of 49.60%. Under Extreme Operated Gust conditions, the maximum stress of the gear decreased from 17.82 MPa to 15.18 MPa, a reduction of 22.99%. Full article

This study investigates the impact of meteorological conditions on unplanned outages of overhead transmission lines (OHTL) in Lithuania’s 0.4–35 kV power grid from January 2013 to March 2023. Data from the Lithuanian electricity distribution network operator and the Lithuanian Hydrometeorological Service were integrated to attribute outage events with weather conditions. A Bayesian change point analysis identified thresholds for these meteorological factors, indicating points at which the probability of outages increases sharply. The analysis reveals that wind gust speeds, particularly those exceeding 21 m/s, are significant predictors of increased outage rates. Precipitation also plays a critical role, with a 15-fold increase in the relative number of outages observed when 3 h accumulated rainfall exceeds 32 mm, and a more than 50-fold increase for 12 h snowfall exceeding 22 mm. This study underscores the substantial contribution of lightning discharges to the number of outages. In forested areas, the influence of meteorological conditions is more significant. Furthermore, the research emphasizes that combined meteorological factors, such as strong winds accompanied by rain or snow, significantly increase the risk of outages, particularly in these forested regions. These findings emphasize the need for enhanced infrastructure resilience and targeted preventive measures to mitigate the impact of extreme weather events on Lithuania’s power grid. Full article

The increasing frequency of wind turbine failures due to extreme weather conditions necessitates the implementation of new solutions to enhance their operational reliability. This paper presents an automatic rotor drop system specifically designed for wind turbines equipped with the Onipko rotor. The system aims to protect turbines from damage caused by critical wind speeds, reducing maintenance costs and extending the equipment’s lifespan. The unique design of the Onipko rotor allows it to operate at wind speeds as low as 0.1 m/s. However, its high drag coefficient and lack of aerodynamic optimization make it susceptible to mechanical stress and structural instability under strong gusts, requiring additional protective measures. The paper presents a calculation of the critical wind speed at which protective measures must be initiated. Through mathematical modeling, this study demonstrates the effectiveness of the rotor drop system in ensuring safe operation at wind speeds reaching 23.5 m/s. The optimization of the PI controller parameters provides a rapid response and stability, significantly enhancing the resilience of wind turbines to adverse weather conditions. Full article

To ensure the safe and stable operation of small and medium-sized wind turbine generators within distributed energy systems, a new active pitch adjustment method for a 1.5 kW distributed pitch wind turbine generator is proposed in this article. The stress and displacement responses of blades under uniform inflow and extreme operating gust inflow conditions were calculated and analyzed using a two-way fluid–structure coupling method. The results showed that under the two different flow conditions, as the pitch angle increased, the stress and displacement responses of the wind turbine blades both significantly decreased, and the decrease was greater with increasing wind speed. The feasibility of the proposed variable-pitch adjustment for blade load reduction under different inflow conditions was further illustrated. The peak of the blade stress response was located at the leading-edge position in the middle of the blades (0.55R) for the different inflow conditions, while the displacement response of the blades was mainly along the waving direction. Through comparative analysis of the blade stress and displacement responses at the same wind speed under different flow conditions, it was found that the maximum mean ratio of the blade displacement and stress responses reached 1.66 and 1.67, respectively. Full article

Most damage to buildings across the contiguous United States of America (USA) is caused by gusts in convective events associated with thunderstorms. Design rules for structures to resist these events rely on the integrity of meteorological observations and the methods of assessment. These issues were addressed for the US Automated Surface Observation System (ASOS) in six preliminary studies published in 2022 and 2023, allowing this present study to focus on the analysis and reporting of gust events observed between 2000 and 2023 at 642 well-exposed ASOS stations distributed across the contiguous USA. It has been recently recognized that the response of buildings to convective gusts, which are non-stationary transient events, differs in character from the response to the locally stationary atmospheric boundary gusts, requiring gust events to be classified and assessed by type. This study sorts the mixture of all observed gust events exceeding 20 kn, but excluding contributions from hurricanes and tropical storms, into five classes of valid meteorological types and two classes of invalid artefacts. The valid classes are individually fitted to optimal sub-asymptotic models through extreme value analysis. Classes are recombined into a joint mixture model and compared with current design rules. Full article

Simplified methods are often used for load estimations during the initial design of the foundations of offshore wind turbines (OWTs). However, the reliability of simplified methods for designing different OWTs needs to be studied. This paper provides a comparative study to evaluate the reliability of simplified approaches. The foundation loads are calculated for OWTs at the mudline level using a simplified approach and OpenFAST simulations and compared. Three OWTs, NREL 5 MW, DTU 10 MW, and IEA 15 MW, are used as reference models. An Extreme Turbulence Model wind load at a rated wind speed, combined with a 50-year Extreme Wave Height (EWH) and Extreme Operating Gust (EOG) wind load and a 1-year maximum wave height are used as the load combinations in this study. In addition, the extreme loads are calculated using both approaches for various metocean data from five different wind farms. Further, the pile penetration lengths calculated using the mudline loads via two methods are compared. The results show that the simplified method provides conservative results for the estimated loads compared to the OpenFAST results, where the extent of conservativism is studied. For example, the bending moment and shear force at the mudline using the simplified approach are 23% to 69% and 32% to 53% higher compared to the OpenFAST results, respectively. In addition, the results show that the simplified approach can be effectively used during the initial phases of monopile foundation design by using factors such as 1.5 and 2 for the shear force and bending moment, respectively. Full article

The entrance in the Sulina channel in the Black Sea is the target area of this study. This represents the southern gate of the seventh Pan-European transport corridor, and it is usually subjected to high navigation traffic. The main objective of the work is to provide a more comprehensive picture concerning the past and future expected dynamics of the environmental matrix in this coastal area, including especially the extreme wind and wave conditions in connection with the possible navigation risks. The methodology considered assumes analyses performed at three different levels. First, an analysis of some in situ measurements at the zero-kilometer point of the Danube is carried out for the 15-year period of 2009–2023. Together with the maximum wind speed and the maximum value of the wind gusts, the water level variation was analyzed at this point. As a second step, the analysis is based on wind speed data provided by regional climate models. Two periods, each spanning 30 years, are considered. These are the recent past (1976–2005), when comparisons with ERA5 reanalysis data were also performed, and the near future (2041–2070), when two different models and three climate scenarios were considered. The focus was on the extreme wind speed values, performing comparisons between the past and future expected extreme winds. Finally, the third analysis is related to the wave conditions. Thus, using as a forcing factor each of the wind fields that was previously analyzed, simulations employing a spectral wave model were carried out. The wave modeling system was focused using three different computational domains with increasing resolution towards the target area, and the nearshore wave conditions were evaluated. The results show that both the extreme wind and wave conditions are expected to slightly increase in the future. Especially in the wintertime, strong wind fields are often expected in this area, with wind gusts exceeding more than 70% of the hourly average wind velocity. With regard to the waves, due to the complex nearshore phenomena, considerable enhancements in terms of significant wave heights are induced, and there is also an elevated risk of the occurrence of rogue waves. This work is still ongoing, and taking into account the high navigation risks highlighted, the next step would be to elaborate the risk assessment of severe shipping conditions, particularly related to the likelihood or probability of adverse conditions with the potential of generating hazardous situations in this coastal environment. Full article