Wind Direction Fluctuations Research Articles

On the importance of wind predictions in wake steering optimization

Abstract. Wake steering is a technique that optimizes the energy production of a wind farm by employing yaw control to misalign upstream turbines with the incoming wind direction. This work highlights the important dependence between wind direction variations and wake steering optimization. The problem is formalized over time as the succession of multiple steady-state yaw control problems interconnected by the rotational constraints of the turbines and the evolution of the wind. Then, this work proposes a reformulation of the yaw optimization problem of each time step by augmenting the objective function by a new heuristic based on a wind prediction. The heuristic acts as a penalization for the optimization, encouraging solutions that will guarantee future energy production. Finally, a synthetic sensitivity analysis of the wind direction variations and wake steering optimization is conducted. Because of the rotational constraints of the turbines, as the magnitude of the wind direction fluctuations increases, the importance of considering wind prediction in a steady-state optimization is empirically demonstrated. The heuristic proposed in this work greatly improves the performance of controllers and significantly reduces the complexity of the original sequential decision problem by decreasing the number of decision variables.

Externally motionless triboelectric nanogenerator based on vortex-induced rolling for omnidirectional wind energy harvesting

Wind-driven triboelectric nanogenerators (WTENGs) are an emerging technology that holds the potential for sustainable wind energy harvesting. Although recent efforts have proposed various strategies for developing WTENGs, realizing their practical utility, characterized by high output performance, lightweight design, compact dimensions, and omnidirectional energy capture, remains a formidable challenge. This study introduces an innovative WTENG that leverages a rolling-based mechanism to achieve effective omnidirectional wind energy harvesting. The distinctive design features a guide vane and a deformable rolling cylinder, both of which play pivotal roles in enhancing triboelectrification, optimizing power output, and ensuring consistent performance despite fluctuations in wind direction. Specifically, the guide vane generates a rotating flow, facilitating the rolling of the cylinder. The electrical energy is generated through triboelectrification occurring between the cylinder and the inner surface of the vane as the cylinder rolls during operation. Numerical simulations and experimental validation have underscored the critical significance of the design of the guide vane and the structural parameters of the rolling cylinder in determining the output performance of the device. Remarkably, the proposed WTENG has demonstrated a root-mean-square area power density of 89.723 mW/m2 at a wind speed of 8 m/s, thus attesting to its superior energy harvesting capabilities. Furthermore, the versatility of this device was evident as it effectively powered a wireless environmental monitoring system and functioned as a self-powered wind speed sensor. With a mere 42 g weight, a compact footprint of 22.062 cm2, and an internal rolling-based mechanism enabling motionless operation from an external perspective, this WTENG offers substantial advantages in spatial efficiency. Consequently, it is an ideal choice for deployment in constrained environments.

Fluctuating sea-level and reversing Monsoon winds drive Holocene lagoon infill in Southeast Asia

Many lagoons surrounded by reefs are partially or completely infilled with reef-derived detrital carbonate sediment. Sediment deposits in such restricted environments are archives of prevailing environmental conditions during lagoon infill. For Indonesia, no paleoenvironmental reconstructions based on Holocene lagoon sediments exist. Here we analyze the sedimentary record obtained from five percussion cores penetrating 10 m into the unconsolidated subsurface of a reef island in the Spermonde Archipelago, Indonesia. The combined compositional, textural and chronostratigraphic analyses reveal that the sedimentary infill of the lagoon underlying the island, starting 6900 years cal BP, was interrupted between 5800 and 4400 years cal BP, when sea level was ~ 0.5 m higher than at present, and monsoon intensity was lower. After the intensity of the monsoons increased to modern levels, and sea level dropped to its present position, lagoonal sedimentation was re-initiated and created the foundation for an island that built up since 3000 years cal BP. Our study provides the first geological evidence for the strong sensitivity of detrital carbonate systems in Indonesia to fluctuations in sea level and dominant wind direction. It thus sheds light on how changing environmental conditions in the context of global warming could affect the morphological development of reef systems, and thereby also habitable coastal areas.

Evidence for Fluctuating Wind in Shaping an Ancient Martian Dune Field: The Stimson Formation at the Greenheugh Pediment, Gale Crater

AbstractTemporal fluctuations of wind strength and direction can influence aeolian bedform morphology and orientation, which can be encoded into the architecture of aeolian deposits. These strata represent a direct record of atmospheric processes and can be used to understand ancient Martian atmospheric processes as well as those on Earth. The strata can: give insight to ancient atmospheric circulation, how the atmosphere evolved in response to global changes in habitability, and how ancient processes differ from modern processes. The Stimson formation at the Greenheugh pediment (Gale crater) records evidence of fluctuating wind across multiple temporal scales. The strata can be subdivided into three intervals–Gleann Beag, Ladder, and Edinburgh intervals. Internally, the intervals record changes of dune morphology and orientation, correlatable to wind fluctuations at multiple temporal scales. The basal Gleann Beag interval comprises compound cross‐strata, deposited by oblique compound dunes. These dunes record a bimodal wind regime, resulting in net sediment transport toward the north. The Ladder interval records a reversal of sediment transport to the south, where straight‐crested simple‐dunes shaped by a seasonally variable winds formed. Finally, the Edinburgh interval records sediment transport to the west, where a unimodal wind formed sinuous‐crested simple dunes. These observations demonstrate active and variable atmospheric circulation in Gale crater during the accumulation of the Stimson dune field, at multiple temporal scales from seasonally driven winds to much longer time‐frames, during the Hesperian. These observations can be used to further understand ancient atmospheric conditions and processes, at a high temporal resolution on Mars.

Practical and simplified measurements for representative photovoltaic array temperatures robust to climate variations

A precise and practical power generation forecasting method for outdoor photovoltaic (PV) arrays and its performance evaluation are essential for advancements in solar power generation. Specifically, accurate temperature measurements of each of the PV modules in an array, the entire outdoor PV array, and the power generation system are crucial regardless of climatic and irradiance conditions. However, outdoor PV temperatures are often affected by environmental factors, such as wind direction, wind speed, solar irradiance, and outdoor air temperature fluctuations. Hence, the temperature data vary greatly depending on the measurement point of the module, which is affected by the above environmental factors. The variations of and uncertainties in temperature often extend over long arrays of PV modules common to large-scale PV systems. Therefore, it is necessary to establish a straightforward and reproducible inspection method to determine a single and robust representative PV module temperature for an array. In this study, we have established one such inspection method for outdoor PV arrays. It was observed that the temperature at the center of the array was closest to the average temperature regardless of the measurement period and climatic conditions; thus, it can be considered as the unbiased and robust representative temperature for the PV array. Moreover, lower irradiance conditions are better for accurate and repeatable PV module temperature measurements. The mean temperature differences of the PV array from its average measured at the center of the array were 0.2 °C for low irradiance and 0.5 °C for high irradiance. The temperature difference observed will have 0.1% to 0.2% impact on the power estimation for monitoring purposes.

The Impacts of Gustiness on Air–Sea Momentum Flux

The exchange of momentum across the air–sea boundary is an integral component of the earth system and its parametrization is essential for climate and weather models. This study focuses on the impact of gustiness on the momentum flux using three months of direct flux observations from a moored surface buoy. Gustiness, which quantifies the fluctuations of wind speed and direction, is shown to impact air–sea momentum fluxes. First, we put forward a new gustiness formula that simultaneously evaluates the impact of fluctuations in wind direction and speed. A critical threshold is established using a cumulative density function to classify runs as either gusty or non-gusty. We find that, during runs classified as gusty, the aerodynamic drag coefficient is increased up to 57% when compared to their non-gusty counterparts. This is caused by a correlated increase in vertical fluctuations during gusty conditions and explains variability in the drag coefficient for wind speeds up to 20 m/s. This increase in energy is connected with horizontal fluctuations through turbulent interactions between peaks in the turbulent spectra coincident with peaks in the wave spectra. We discus two potential mechanistic explanations. The results of this study will help improve the representation of gustiness in momentum flux parameterizations leading to more accurate ocean models.

Study on Characteristic of Standard Deviation of Wind Direction Fluctuation for Atmospheric Dispersion Simulation

Study on Characteristic of Standard Deviation of Wind Direction Fluctuation for Atmospheric Dispersion Simulation

Wind direction fluctuation analysis for wind turbines

Fluctuations are a key characteristic of the wind resource. It is important to quantitatively analyze wind direction fluctuation due to its influence on the optimization of wind turbine yaw control. Based on wind resource data available from SCADA systems, a method is proposed to describe wind direction fluctuations in terms of fluctuation amplitude A and fluctuation duration T. A Weibull distribution is employed to fit the marginal probability density of both these two measures of wind direction fluctuations, and a mixed Copula used to connect the marginal distributions, establishing the joint probability density function. This representation has been verified through comparison with the real operating SCADA data. A set of indicators are extracted from the probability distribution which can accurately quantify the local wind direction fluctuation characteristics of a wind turbine. These indicators can be helpful in the optimization of the yaw control system parameters, facilitating an improvement in the power generating performance of the wind turbine. • Wind direction fluctuations are studied with statistic method and SCADA data. • Weibull distribution and copula are used to model the wind direction fluctuations. • A set of indicators are extracted to quantify the wind direction fluctuations.

Three-Dimensional Wind Measurement Based on Ultrasonic Sensor Array and Multiple Signal Classification.

The wind power industry continues to experience rapid growth worldwide. However, the fluctuations in wind speed and direction complicate the wind turbine control process and hinder the integration of wind power into the electrical grid. To maximize wind utilization, we propose to precisely measure the wind in a three-dimensional (3D) space, thus facilitating the process of wind turbine control. Natural wind is regarded as a 3D vector, whose direction and magnitude correspond to the wind’s direction and speed. A semi-conical ultrasonic sensor array is proposed to simultaneously measure the wind speed and direction in a 3D space. As the ultrasonic signal transmitted between the sensors is influenced by the wind and environment noise, a Multiple Signal Classification algorithm is adopted to estimate the wind information from the received signal. The estimate’s accuracy is evaluated in terms of root mean square error and mean absolute error. The robustness of the proposed method is evaluated by the type A evaluation of standard uncertainty under a varying signal-to-noise ratio. Simulation results validate the accuracy and anti-noise performance of the proposed method, whose estimated wind speed and direction errors converge to zero when the SNR is over 15 dB.

Resurs latitudinalnog vetra u priobalnom pojasu države Tamil Nadu u Indiji

Globally, the wind power capacities are growing every passing year, which is an indicative of social and commercial acceptance of this technology by a larger section of the populations. In Indian perspective, the wind power capacities are also increasing with annual additions of new capacities and most of the development work is taking place in the southern part and that too in Tamil Nadu state. Research work in the area of accurate wind power assessment is being conducted to optimize the utilization of wind power and at the same time efforts are being exerted to enhance the operation and maintenance capabilities of the local skilled and semi-skilled work force. This study utilizes 38 years of hourly mean wind speed data from seven locations for providing the accurate wind power assessment and understanding the longitudinal behavior of its characteristics. The wind speed is found to be increasing with decreasing latitudes and having lesser variation in wind direction fluctuations, simply means conversing wind direction to narrower bands. Kanyakumari is identified as the most probable wind power deployment site with annual energy yield of 227.55 MWh and capacity factor of 34% followed by Vedaranyam, and Thoothukudi, as second and third priority sites with respective annual yields of 223.36 MWh and 218.73 MWh.

The Baja California Peninsula, a Significant Source of Dust in Northwest Mexico

Despite their impacts on ecosystems, climate, and human health, atmospheric emissions of mineral dust from deserts have been scarcely studied. This work estimated dust emission flux (E) between 1979 and 2014 from two desert regions in the Baja California Peninsula (BCP) using a modified dust parameterization scheme. Subsequently, we evaluated the processes controlling the variability of E at intra- and interannual scales. During the period 1979–2014 peak E were generally recorded in summer (San Felipe) and spring (Vizcaino), and the lowest emissions occurred in autumn (San Felipe) and winter (Vizcaíno). Intra- and interannual variability in E was associated with fluctuations in wind speed and direction, precipitation, and soil moisture, which, in turn, were controlled by the seasonal displacement of the North Pacific high-pressure center. Key drivers of the interannual variability of E are strong El Niño Southern Oscillation (ENSO) events. These climatic events and the hydrometeorological variables mentioned above played a major role in the onset and occurrence of dust events, with the highest annual emissions at Vizcaíno. Besides, a lag of 19 months (San Felipe) and 21 months (Vizcaino) was recorded between the occurrence of relevant E and ENSO events, apparently in response to the effect of this climatic event on precipitation. The climate variability of E in both desert regions was evidenced by the positive trends associated with increases in wind speed and air temperature, and with decreases in precipitation and soil moisture. Finally, our findings suggest that the BCP should be considered as a significant source of dust for the regional inventory of particulate matter emissions from the Earth’s surface.

Large-Eddy Simulation of the Effects of Wind-Direction Fluctuations on Turbulent Flow and Gas Dispersion Within a Cubical Canopy

Large-eddy simulation of turbulent flow and gas dispersion in a cubical canopy is used to investigate the effect of wind-direction fluctuations on gas dispersion. Square blocks are set at regular intervals on the bottom surface, with line sources placed within the first, second, third, fifth and seventh rows. Large-eddy simulation without wind-direction fluctuations produces a good prediction of the mean streamwise velocity component, and the standard deviations of the fluctuations in the streamwise and spanwise velocity components, obtained from a wind-tunnel experiment. Wind-direction fluctuations marginally affect the mean streamwise velocity component above the canopy in the first row, and do not significantly affect the component beyond the third row. The standard deviations of the fluctuations in the streamwise and spanwise velocity components above the canopy are also affected by wind-direction fluctuations, but within the canopy the components are less sensitive to the fluctuations beyond the third row. The spatially-averaged concentrations within the canyon with wind-direction fluctuations before the third row are marginally greater than concentrations without the fluctuations, but they are essentially identical beyond the fifth row. The low-frequency turbulent flow that passes through the canyon is generated with and without wind-direction fluctuations.

An investigation of the impact of wind speed and turbulence on small wind turbine operation and fatigue loads

This paper investigates the operation and loading of a 5 kW HAWT using the aeroelastic code FAST. Wind data from built environment site at Port Kennedy (PK) and from a flat terrain site in Östergarnsholm (OG), are analysed and compared with IEC 61400-2. The longitudinal turbulence intensity (TIu) in the PK wind field was 22%; which was higher than the estimated value in IEC 61400-2 Normal Turbulence Model. The TI in the flat terrain (OG) was below 18% for all mean wind speeds. The selected wind conditions from the two locations were used as input in FAST simulation to investigate the performance and loading of the turbine. The elevated turbulence in PK wind fields increased the output rotor power which was more than that predicted by the standard. Similarly, PK wind field also showed higher blade root flapwise bending moment resulting into twice as much damage load on the turbine blades due to large short-term fluctuations in both wind speed and direction. This value for OG was below the standard's prediction. We observe that the current IEC standard seems inadequate for urban siting of SWTs and requires modification for more reliable deployment in turbulent sites.

Performance Assessment of Dynamic Downscaling of WRF to Simulate Convective Conditions during Sagebrush Phase 1 Tracer Experiments

Large-Eddy Simulations (LES) corresponding to four convective intensive observation periods of Sagebrush Phase 1 tracer experiment were conducted with realistic boundary conditions using Weather Research and Forecast model (WRF). Multiple nested domains were used to dynamically downscale the conditions from domain with grid size of 24 km to local scales with grid size of 150 m. Sensitivity analysis of mesoscale model was conducted using three boundary layer, three surface layer and two micro-physics schemes. Model performance was evaluated by comparing the surface meteorological variables and boundary layer height from the mesoscale runs and observed values during tracer experiment. Output from mesoscale simulations was used to drive the LES domains. Effect of vertical resolution and sub-grid scale parameterizations were studied by comparing the wind speed and direction profiles along with turbulent kinetic energy at two different heights. Atmospheric stability estimated using the Richardson number and shear exponent evaluated between 8- and 60-m levels was found to vary between weakly unstable to unstable. Comparing the wind direction standard deviations coupled with the wind speeds showed that the WRF-LES underestimated the wind direction fluctuations for wind speeds smaller than 3-ms − 1 . Based on the strengths of convection and shear, WRF-LES was able to simulate horizontal convection roll and convective cell type features.

Numerical Investigation of Terrain-Induced Turbulence in Complex Terrain by Large-Eddy Simulation (LES) Technique

In the present study, field observation wind data from the time of the wind turbine blade damage accident on Shiratakiyama Wind Farm were analyzed in detail. In parallel, high-resolution large-eddy simulation (LES) turbulence simulations were performed in order to examine the model’s ability to numerically reproduce terrain-induced turbulence (turbulence intensity) under strong wind conditions (8.0–9.0 m/s at wind turbine hub height). Since the wind velocity and time acquired from the numerical simulation are dimensionless, they are converted to full scale. As a consequence, both the standard deviation of the horizontal wind speed (m/s) and turbulence intensity evaluated from the field observation and simulated wind data are successfully in close agreement. To investigate the cause of the wind turbine blade damage accident on Shiratakiyama Wind Farm, a power spectral analysis was performed on the fluctuating components of the observed time series data of wind speed (1 s average values) for a 10 min period (total of 600 data) by using a fast Fourier transform (FFT). It was suggested that the terrain-induced turbulence which caused the wind turbine blade damage accident on Shiratakiyama Wind Farm was attributable to rapid wind speed and direction fluctuations which were caused by vortex shedding from Tenjogadake (elevation: 691.1 m) located upstream of the wind farm.

The influence of atmospheric cold fronts on larval supply and settlement of intertidal invertebrates: Case studies in the Cabo Frio coastal upwelling system (SE Brazil)

Atmospheric fronts such as cold fronts are dynamic mesoscale systems with potential effects on the ecology of marine communities. In this study, larval dynamics in subtropical rocky shore communities were evaluated under the influence of atmospheric frontal systems. The hypothesis is that these systems may promote favorable conditions for larval supply and settlement regardless of taxa or site, and that supply and settlement vary in association with fluctuations of meteorological and oceanographic conditions driven by the fronts. This study was carried out in the Southeastern Brazil littoral region under the influence of coastal upwelling events (Cabo Frio) and subject to weekly atmospheric frontal systems, cold polar fronts. The spatial and temporal variability of larvae and settlers of barnacles and mussels were assessed by collecting daily samples at three sites before, during and after atmospheric cold fronts, and the atmospheric and pelagic conditions were monitored. Contrasts among rates, events and sites were tested using discriminant function analysis, analyses of variance and correlation analysis. Atmospheric frontal systems were considered to influence the sites when wind direction changed to SW-S-SE and persisted for at least a day, and waves from SW-SW-SE increased in height. The results corroborate the hypothesis that cold fronts are important regulators of larval dynamics and intertidal communities on rocky shores of the studied area. Both larval supply and settlement were highly correlated with fluctuations in wind speed and direction. Higher settlement rates of barnacles occurred one-day prior, or on the onset of cold fronts. Mussels species tended to settle during all conditions, but on average, settlement rates were higher during the cold fronts. Some temporal trends were site specific and variability was detected among taxa and larval stages. Our findings suggest that mesoscale oceanographic/atmospheric systems are particularly relevant on the regulation and potentially forecasting of rocky shore invertebrates' ecology.

AIR QUALITY IN MINING AREAS: THE CASE OF STRATONI, CHALKIDIKI, GREECE

Air quality sampling tests are conducted on a 24h basis by “HELLENIC GOLD S.A.” in the Stratoni mining settlement. The settlement is located in the neighbourhood of a flotation plant where galena and sphalerite concentrates are produced after crushing and processing of Pb-Ag-Zn sulfide ore. Old piles of mineral waste occur close to the settlement. The mineralogy of mineral dust collected on filters of 3 air samplers from August to December 2008 was studied. Elemental analysis of mineral dust collected from January to December 2008 was conducted. The purpose of the study was to determine levels of air pollution, type of mineral particles as well as potential sources. Measurements of air quality included PM10. Statistical analysis of the collected data included tests to determine the control on daily particle concentration and mineralogy of fluctuations of temperature, humidity, wind direction and wind speed. Air quality was better than during 1998-2000. Air quality was typically at its worse during hot summer days when wind speed was high. The concentration of PM10 particulate matter was quite low when compared to International Air Quality Standards regulations, indicating that levels of air pollution in the area do not pose human health hazards.

Statistical parameters of the spatiotemporal variability of the wind direction in the surface layer

Multipoint measurements of wind direction were carried out during the expedition of the Institute of Atmospheric Physics, Russian Academy of Sciences (IPA RAS), in Tsimlyansk in 2012. Spatial correlation functions for the transverse direction and temporal correlation functions for the longitudinal direction are plotted under stable and unstable stratification of the atmosphere. The longitudinal correlation radius is much higher than the transverse one, and radii in daytime realizations are larger than in nighttime. To determine the stratification conditions, an ultrasonic anemometer–thermometer was used. Autospectra of wind direction fluctuations were plotted. They include long segments of power dependence on the frequency. The spectral correlation coefficients of variations in the wind direction versus intersensor distance in the transverse direction are also calculated. A set of fast-response thermometers was used in the experiment. They allowed temperature mapping, i.e., plotting the time variations in the isothermal surface altitude. That analysis was also applied to visualization of the spatiotemporal variability of wind direction. The resulting data were used for planning the helicity measurements in the Tsimlyansk expedition in 2014.

Power fluctuation evaluation of large‐scale wind turbines based on SCADA data

The random fluctuation of wind is the basic factor causing the power fluctuation of wind turbines. On the basis of the relationship model between wind and power, and considering the influences of wind speed fluctuation and wind direction fluctuation on power fluctuation, a novel fluctuation coefficient of wind speed, fluctuation coefficient of wind direction and the comprehensive influence factor are defined. The one-dimensional (1D) evaluation models of wind speed fluctuation to power fluctuation, wind direction fluctuation to power fluctuation and the 2D evaluation model of wind speed and wind direction fluctuation to power fluctuation are presented. The operating process of wind turbines is divided into three regions: the constant region of power coefficient, the transition region and the constant power region. In the constant region of power coefficient, wind speed fluctuation is the main factor affecting power fluctuation; wind direction fluctuation has little effect. In the transition region and the constant power region, both wind speed fluctuation and wind direction fluctuation have little effect on power fluctuation; especially in the constant power region in which power capture is limited by the pitch control technology, power fluctuation is not affected by wind speed fluctuation and wind direction fluctuation.

The Annual Averaged Atmospheric Dispersion Factor and Deposition Factor According to Methods of Atmospheric Stability Classification

Background: This study analyzes the differences in the annual averaged atmospheric dispersion factor and ground deposition factor produced using two classification methods of atmospheric stability, which are based on a vertical temperature difference and the standard deviation of horizontal wind direction fluctuation. Materials and Methods: Daedeok and Wolsong nuclear sites were chosen for an assessment, and the meteorological data at 10 m were applied to the evaluation of atmospheric stability. The XOQDOQ software program was used to calculate atmospheric dispersion factors and ground deposition factors. The calculated distances were chosen at 400 m, 800 m, 1,200 m, 1,600 m, 2,400 m, and 3,200 m away from the radioactive material release points. Results and Discussion: All of the atmospheric dispersion factors generated using the atmospheric stability based on the vertical temperature difference were shown to be higher than those from the standard deviation of horizontal wind direction fluctuation. On the other hand, the ground deposition factors were shown to be same regardless of the classification method, as they were based on the graph obtained from empirical data presented in the Nuclear Regulatory Commission’s Regulatory Guide 1.111, which is unrelated to the atmospheric stability for the ground level release. Conclusion: These results are based on the meteorological data collected over the course of one year at the specified sites; however, the classification method of atmospheric stability using the vertical temperature difference is expected to be more conservative.