Wind Fluctuations Research Articles

Redox flow battery technology development from the perspective of patent applications: A review

With the continuous increase in global energy consumption, the development and utilization of renewable energy become imperative. However, the intermittency and fluctuation of wind and solar power generation prevent direct grid integration, resulting in energy waste. As a large-scale electrochemical energy storage technology, redox flow batteries (RFBs) can effectively store renewable energy and smooth the power output. This paper summarizes the development history of RFBs technology in China by analyzing relevant patent application data, elaborates on the working principles, advantages and disadvantages of various RFBs, and their latest research progress. It analyzes the technical challenges in current RFBs research and presents the application prospects of RFBs commercialization. The results show that although RFBs technology has made significant progress in China, it still faces issues like high battery cost and limited cycle life. To realize the efficient utilization of renewable energy and green low-carbon development, RFBs technology needs continuous optimization and upgrade. This paper can provide references for the development of RFBs technology.

A model of correlated interval–probabilistic conditional value-at-risk and optimal dispatch with spatial correlation of multiple wind power generations

The correlated uncertain variables with the probability density function have been conducted in previous studies. However, the probability density functions of random variables are not always available, but their boundaries are more readily obtained. Accordingly, this paper adopts the interval variables with spatial correlation in multiple wind generations to achieve more practical scheduling. First, a novel risk qualification model, that is, correlated interval-probabilistic-based conditional value-at-risk, can be proposed to reduce the conservativeness of the traditional risk assessment methods. Then, an uncertain optimization model is built that considers multiple uncertainties, including probabilistic uncertainties of the load and interval uncertainties of coupled adjacent wind farms. Moreover, two spinning reserves are developed and integrated into the dispatch model. Finally, the influence of the wind power generation's correlation and fluctuation levels on the dispatch results is also investigated. Simulations on IEEE-39 and IEEE-118 bus systems validate the accuracy of the proposed risk assessment method.

Capacity investment decisions of energy storage power stations supporting wind power projects

PurposeRapidly increasing the proportion of installed wind power capacity with zero carbon emission characteristics will help adjust the energy structure and support the realization of carbon neutrality targets. The intermittency of wind resources and fluctuations in electricity demand has exacerbated the contradiction between power supply and demand. The time-of-use pricing and supply-side allocation of energy storage power stations will help “peak shaving and valley filling” and reduce the gap between power supply and demand. To this end, this paper constructs a decision-making model for the capacity investment of energy storage power stations under time-of-use pricing, which is intended to provide a reference for scientific decision-making on electricity prices and energy storage power station capacity.Design/methodology/approachBased on the research framework of time-of-use pricing, this paper constructs a profit-maximizing electricity price and capacity investment decision model of energy storage power station for flat pricing and time-of-use pricing respectively. In the process, this study considers the dual uncertain scenarios of intermittency of wind resources and random fluctuations in power demand.Findings(1) Investment in energy storage power stations is the optimal decision. Time-of-use pricing will reduce the optimal capacity of the energy storage power station. (2) The optimal capacity of the energy storage power station and optimal electricity price are related to factors such as the intermittency of wind resources, the unit investment cost, the price sensitivities of the demand, the proportion of time-of-use pricing and the thermal power price. (3) The carbon emission level is affected by the intermittency of wind resources, price sensitivities of the demand and the proportion of time-of-use pricing. Incentive policies can always reduce carbon emission levels.Originality/valueThis paper creatively introduced the research framework of time-of-use pricing into the capacity decision-making of energy storage power stations, and considering the influence of wind power intermittentness and power demand fluctuations, constructed the capacity investment decision model of energy storage power stations under different pricing methods, and compared the impact of pricing methods on optimal energy storage power station capacity and carbon emissions.HighlightsElectricity pricing and capacity of energy storage power stations in an uncertain electricity market.Investment strategy of energy storage power stations on the supply side of wind power generators.Impact of pricing method on the investment decisions of energy storage power stations.Impact of pricing method, energy storage investment and incentive policies on carbon emissions.A two-stage wind power supply chain including energy storage power stations.

Spectral break of the density power spectrum in solar wind turbulence

We use density measurements deduced from spacecraft potential to study the power spectral density (PSD) of compressive fluctuations in the solar wind. Typically, plasma measurements do not have a sufficiently high time resolution to resolve density fluctuations down to ion kinetic scales. However, the calibrated spacecraft potential allows for much higher time resolutions to resolve the spectral break between ion inertial and kinetic ranges. We used fast-survey mode data from Magnetospheric MultiScale when the spacecrafts were in the pristine solar wind. The density spectra’s morphology differs from the trace magnetic field fluctuations, with a flattening often occurring between inertial and kinetic ranges. We find that the spectral break of the trace magnetic field fluctuations occurs near the expected frequency for cyclotron resonance or magnetic reconnection. Meanwhile, the spectral break at the start of the ion kinetic range for density fluctuations is often at a higher frequency when compared to the trace magnetic field. We discuss possible interpretations for these observations.

Statistical Properties of Alfvén Ion Cyclotron Waves and Kinetic Alfvén Waves in the Inner Heliosphere

Alfvén ion cyclotron waves (ACWs) and kinetic Alfvén waves (KAWs) are found to exist at <0.3 au observed by Parker Solar Probe in Alfvénic slow solar winds. To examine the statistical properties of the background parameters for ACWs and KAWs and related wave disturbances, both wave events observed by Parker Solar Probe are selected and analyzed. The results show that there are obvious differences in the background and disturbance parameters between ACWs and KAWs. ACW events have a relatively higher occurrence rate but with a total duration slightly shorter than KAW events. The median background magnetic field magnitude and the related background solar wind speed of KAW events are larger than those of ACWs. The distributions of the relative disturbances of the proton velocity, proton temperature, the proton number density, and β cover wider ranges for ACW events than for KAW events. The results may be important for the understanding of the nature and characteristics of Alfvénic slow solar wind fluctuations at ion scales near the Sun, and provide the information of the background field and plasma parameters and the wave disturbances of ACWs and KAWs for further relevant theoretical modeling or numerical simulations.

Large-eddy simulation of vortex-excited force on a square cylinder with transverse wind fluctuations

This study utilized 3D Large-eddy simulation to investigate the crosswind drag force on a square cylinder subjected to transverse wind fluctuation. Two distinct methods were employed to generate the fluctuation: a prescribed sine function at the inlet boundary and an upwind barrier. The frequency was normalized in the same Strouhal number form. The transverse wind fluctuation with a normalized frequency above 0.05 tends to excite the square cylinder transversely with the same frequency band. The frequency effect also exists on the square cylinder located downwind an obstacle half the square cylinder’s size. However, an obstacle 2.5 times the size of the square cylinder generates a cross-wind fluctuation with the normalized frequency of 0.04, which cannot excite the square cylinder transversely. The frequency effect from the upwind barrier significantly dampens with the distance and disappears at 8–10 times the square cylinder size.

Linear Mode Decomposition in Magnetohydrodynamics Revisited

Small-amplitude fluctuations in the magnetized solar wind are measured typically by a single spacecraft. In the magnetohydrodynamics (MHD) description, fluctuations are typically expressed in terms of the fundamental modes admitted by the system. An important question is how to resolve an observed set of fluctuations, typically plasma moments such as the density, velocity, pressure, and magnetic field fluctuations, into their constituent fundamental MHD modal components. Despite its importance in understanding the basic elements of waves and turbulence in the solar wind, this problem has not yet been fully resolved. Here, we introduce a new method that identifies between wave modes and advected structures such as magnetic islands or entropy modes and computes the phase information associated with the eligible MHD modes. The mode-decomposition method developed here identifies the admissible modes in an MHD plasma from a set of plasma and magnetic field fluctuations measured by a single spacecraft at a specific frequency and an inferred wavenumber k m . We present data from three typical intervals measured by the Wind and Solar Orbiter spacecraft at ∼1 au and show how the new method identifies both propagating (wave) and nonpropagating (structures) modes, including entropy and magnetic island modes. This allows us to identify and characterize the separate MHD modes in an observed plasma parcel and to derive wavenumber spectra of entropic density, fast and slow magnetosonic, Alfvénic, and magnetic island fluctuations for the first time. These results help identify the fundamental building blocks of turbulence in the magnetized solar wind.

Novel QO-PFA governed FO-type-II fuzzy controller for LFC of thermo-electric generator based hybrid power system

The present article addresses various novel and advanced approaches to mitigate frequency oscillation issues in an integrated power system. The suggested model of the multi-source power system is basically a two-area power system, where area2 is completely a microgrid system. The diesel generator, thermo-electric generator, wind generator, solar PV system, micro-turbine and fuel cell are the basic power generating sources in the microgrid system. The microgrid also has been associated with various energy saving equipments like battery and flywheel energy storage (FES) system to improve the power quality of the system. The unpredictable wind speed variant and fluctuation in solar power incorporates oscillations in voltage and frequency profile of the interconnected power system. In challenging to above issues, this research article has designed an innovative Fractional Order-type-2 fuzzy controller (FO-T2FC) to supress unwanted errors in the frequency and voltage of the system. Further, the proposed controller parameters are selected optimally with suggesting a novel Quassi- Oppositional Path Finder Algorithm (QO-PFA) under different operatings. An analysis on relative study is exercised to validate strength of the FO-T2FC control strategy and QO-PFA algorithm. Owing to the performance analysis, it is justified that proposed QO-PFA designed FO-T2FC controller is proved to be most potential candidate and able to improve the dynamic frequency response of area1 (Δf1) by 251.74% and 418.74% as compared to Type1 fuzzy controller and conventional PID controller respectively.

Signatures of geostrophic turbulence in power spectra and third-order structure function of offshore wind speed fluctuations

We analyze offshore wind speeds with a time resolution of one second over a long period of 20 months for different heights above the sea level. Energy spectra extending over more than seven decades give a comprehensive picture of wind fluctuations, including intermittency effects at small length scales and synoptic weather phenomena at large scales. The spectra S(f) show a scaling behavior consistent with three-dimensional turbulence at high frequencies f, followed by a regime at lower frequencies, where fS(f) varies weakly. Lowering the frequency below a crossover frequency f_mathrm{scriptscriptstyle 2D}, a rapid rise of fS(f) occurs. An analysis of the third-order structure function D_3(tau ) of wind speed differences for a given time lag tau shows a rapid change from negative to positive values of D_3(tau ) at tau simeq 1/f_mathrm{scriptscriptstyle 2D}. Remarkably, after applying Taylor’s hypothesis locally, we find the third-order structure function to exhibit a behavior very similar to that obtained previously from aircraft measurements at much higher altitudes in the atmosphere. In particular, the third-order structure function grows linearly with the separation distance for negative D_3, and with the third power for positive D_3. This allows us to estimate energy and enstrophy dissipation rates for offshore wind. The crossover from negative to positive values occurs at about the same separation distance of 400 km as found from the aircraft measurements, suggesting that this length is independent of the altitude in the atmosphere.

Identification of two-dimensional aerodynamic admittance of a central-slotted box girder based on force-balance measurements

This paper presents an experimental investigation of buffeting lift forces on a central-slotted box girder in turbulent flow, and aims to identify the corresponding generalized aerodynamic admittance (generalized-AAF) and two-dimensional aerodynamic admittance (2D-AAF). The generalized-AAF is obtained using the one-wavenumber spectra of lift and wind fluctuations, while the 2D-AAF is obtained using an improved method based on force-balance measurement. The key to this improved method is separating out the three-dimensional effect of turbulence (3D-effect) from the generalized-AAF while considering the segment length of the force measurement and turbulence integral scale. The results indicate that the generalized-AAF of the central-slotted box girder is much less than the Sears function, which is consistent with most previous studies. However, the values of 2D-AAF decay more slowly in comparison with the Sears function. An empirical formula for the 2D-AAF of the central-slotted box girder is given based on the experimental data. Additionally, the study finds that the ratio of the turbulent integral scale to the characteristic dimension of the model plays a significant role in determining the 3D-effect of turbulence, resulting in the difference between the generalized-AAF and 2D-AAF. Therefore, the 2D-AAF is particularly useful for estimating the buffeting force of a bridge deck when the turbulence scale does not match the size of the model.

Integrating wind energy and compressed air energy storage for remote communities: A bi-level programming approach

The integration of compressed air energy storage and wind energy offers an attractive energy solution for remote areas with limited access to reliable and affordable energy sources. This study presents a design approach for an energy system comprising wind turbines, compressed air energy storage, and diesel generators. The proposed method is based on bi-level programming, enabling the simultaneous optimization of the size and operation of the system while considering the interaction between them. Detailed mechanical design and configuration of the compressed air energy storage system are considered, including the number and size of compressors and turbines, valves, recuperator operating conditions, etc. In contrast with conventional compressed air energy storage systems, operating once a day for peak shaving, the proposed compressed air energy storage system aims to mitigate wind fluctuations. Therefore, it would operate under partial load conditions most of the time, and as a result, the system's off-design modeling is also considered. The results indicate that the proposed system is a promising, cost-effective, reliable energy solution for remote areas, significantly decreasing the average daily total cost and CO2 emissions by 69 % and 76 %, respectively. Additionally, by studying the system's performance under both design and off-design conditions, it is concluded that considering the off-design conditions is critical to ensure a more realistic performance of the system as the system is less likely to utilize the compressed air energy storage in low charging and discharging opportunities.

Switchbacks, microstreams, and broadband turbulence in the solar wind

Switchbacks are a striking phenomenon in near-Sun coronal hole flows, but their origins, evolution, and relation to the broadband fluctuations seen farther from the Sun are unclear. We use the near-radial lineup of Solar Orbiter and Parker Solar Probe during September 2020 when both spacecraft were in wind from the Sun's Southern polar coronal hole to investigate if switchback variability is related to large scale properties near 1 au. Using the measured solar wind speed, we map measurements from both spacecraft to the source surface and consider variations with source Carrington longitude. The patch modulation of switchback amplitudes at Parker at 20 solar radii was associated with speed variations similar to microstreams and corresponds to solar longitudinal scales of around 5°–10°. Near 1 au, this speed variation was absent, probably due to interactions between plasma at different speeds during their propagation. The alpha particle fraction, which has recently been shown to have spatial variability correlated with patches at 20 solar radii, varied on a similar scale at 1 au. The switchback modulation scale of 5°–10°, corresponding to a temporal scale of several hours at Orbiter, was present as a variation in the average deflection of the field from the Parker spiral. While limited to only one stream, these results suggest that in coronal hole flows, switchback patches are related to microstreams, perhaps associated with supergranular boundaries or plumes. Patches of switchbacks appear to evolve into large scale fluctuations, which might be one driver of the ubiquitous turbulent fluctuations in the solar wind.

A Study of Turbulent Fluctuation of Three-Component Wind and Air Temperature in the Surface Layer of Baghdad Urban

Abstract In this study, the air temperature and velocity component means were also computed, as were the fluctuation values of the three component velocities (u, v, and w) and the air temperature (T). The instantaneous velocity can be broken down into its tally of varying and time-averaged contributions using a process known as Reynolds decomposition. The Reynolds decomposition depends on how you define the mean. The results show that the behaviors of the u, v, and w diurnal cycles are anticipated in ABL. The best fit is for air temperature because the correlation coefficient between time and temperature is large. The component fluctuated around zero, and the sum of the fluctuation averages equaled zero. The fluctuation of u was large, which increased because of the initial value of u and because of wind direction and friction velocity.

Spectrum of kinetic-Alfvén-wave turbulence: intermittency or tearing mediation?

ABSTRACT We investigate the spectral properties of the electromagnetic fluctuations of sub-ion scale turbulence in weakly collisional, low-beta plasmas using a two-field isothermal gyrofluid model. The numerical results strongly support a description of the turbulence as a critically balanced Kolmogorov-like cascade of kinetic Alfvén wave fluctuations, as amended by previous studies to include intermittency effects. The measured universal index of the energy spectra from systems with different flux-unfreezing mechanisms excludes the role of tearing mediation in determining the spectra. The fluctuations remain isotropic in the plane perpendicular to the strong background magnetic fields as they cascade to smaller scales, which explains the absence of tearing mediation. The calculation of high-order, multipoint structure functions of magnetic fluctuations suggests that the intermittent structures have a quasi-2D, sheet-type morphology. These results are useful for explaining recent observations of the spectrum and structure of magnetic and density fluctuations in the solar wind at sub-proton scales, and are relevant for modelling the energy dissipation in a broad range of astrophysical systems.

An integrated ultra short term power forecasting method for regional wind–pv–hydro

Renewable-based multi energy power system is the main trend for power system in the future. However, the randomness and fluctuation of wind and photovoltaic power, as well as the seasonality of hydropower, have an increasingly prominent impact on the stability of power system. Accurate power forecasting technology is the key to solve the above problems. At the same time, the output characteristics of heterogeneous energy sources are very different, and the existing forecasting methods are difficult to fully exploit their spatio-temporal correlation characteristics, which limits the improvement of prediction accuracy. In this paper, an integrated ultra short term power forecasting method for regional wind–pv–hydro is proposed, Firstly, it quantifies the differences and similarities among wind, pv and hydro in different scenarios based on empirical mode decomposition, and achieves the extraction of homogeneous features, on this basis, the integrated power forecasting models for wind, pv and hydro based on long short-term memory neural networks is constructed , and achieves regional-level integrated forecasting of wind, pv and hydro. The results show that the forecasting accuracy and modeling efficiency of the proposed integrated forecasting method are significantly improved compared with the traditional independent forecasting method, the forecasting accuracy is increased by 1%–3%, the modeling efficiency is increased by 6 times.

Wind variability across the North Humboldt Upwelling System

Surface wind is taken as the primary driver of upwelling in the eastern boundary upwelling systems. The fluctuation of momentum flux associated with the variation in wind regulates the nutrient supply to the euphotic surface layer via changing the properties of oceanic mixed layer depth, the coastal and offshore upwelling, and horizontal advection. Here, the spatial and temporal variability of the surface wind field over the last seven decades across the Peruvian upwelling system is investigated. Strong fluctuations in seasonal to decadal timescales are found over the entire upwelling system. A semi-periodic wind fluctuation on an interannual timescale is found, which is closely related to the regional sea surface temperature and can be attributed to the El Niño Southern Oscillation (ENSO). However, the wind anomaly patterns during positive and negative phases of ENSO are not opposite, which suggests an asymmetric response of local wind to ENSO cycles. In addition, a semi-regular fluctuation on the decadal timescale is evident in the wind field, which can be attributed to the Interdecadal Pacific Oscillation (IPO). Our results show that the sea surface temperature over the Humboldt Upwelling System is closely connected to local wind stress and the wind stress curl. The SST wind stress co-variability seems more pronounced in the coastal upwelling cells, in which equatorward winds are very likely accompanied by robust cooling over the coastal zones. Over the past seven decades, wind speed underwent a slightly positive trend. However, the spatial pattern of the trend features considerable heterogeneity with larger values near the coastal upwelling cells.

Operation Performance Analysis of a Novel Renewable Energy‐Driven Multienergy Supply System Based on Wind, Photovoltaic, Concentrating Solar Power, Proton Exchange Membrane Electrolyzers, and Proton Exchange Membrane Fuel Cell

In pursuing clean energy systems and carbon neutrality, the efficient use of renewable energy is key. This research introduces a novel wind–solar–hydrogen multienergy supply (WSH‐MES) system, powered by renewables, designed to stabilize power output through regulated concentrating solar power (CSP) and proton exchange membrane electrolyzers (PEMEs). An active regulation strategy for thermal and hydrogen storage is developed to counterbalance the volatility of wind and photovoltaic power. Key results reveal that the WSH‐MES system surpasses WP–PV and WP–PV–CSP systems in reliability, reducing power supply loss probability to 2.81%. This improvement is largely due to the controlled CSP and PEME, which effectively mitigates the stochastic fluctuations in wind and solar power generation, thereby ensuring more stable and reliable power output. Moreover, the system achieves an 80.97% primary renewable energy rate and a 0.12 power discard rate. In conclusion, this research comprehensively examines the operational characteristics of the WSH‐MES system, elucidates the practical advantages of the WSH‐MES system in terms of reliability, renewable energy utilization, and adaptability under various conditions. The results offer valuable insights into the design and operation of multienergy supply systems, potentially fostering the large‐scale implementation of renewable energy systems and leading toward a sustainable energy future.

Probing Gravity Waves in the Middle Atmosphere Using Infrasound From Explosions

AbstractThis study uses low‐frequency, inaudible acoustic waves (infrasound) to probe wind and temperature fluctuations associated with breaking gravity waves (GWs) in the middle atmosphere. Building on an approach introduced by Chunchuzov et al., infrasound recordings are used to retrieve effective sound‐speed fluctuations in an inhomogeneous atmospheric layer that causes infrasound backscattering. The infrasound was generated by controlled blasts at Hukkakero, Finland, and recorded at the IS37 infrasound station, Norway in the late summers 2014–2017. Our findings indicate that the analyzed infrasound scattering occurs at mesospheric altitudes of 50–75 km, a region where GWs interact under non‐linearity, forming thin layers of strong wind shear. The retrieved fluctuations were analyzed in terms of vertical wave number spectra, resulting in an approximate power law that corresponds to the “universal” saturated spectrum of atmospheric GWs. The power law wavenumber range corresponds to vertical atmospheric scales of 33–625 m. The fluctuation spectra were compared to theoretical GW saturation theories as well as to independent wind measurements by the Saura medium‐frequency radar near Andøya Space Center around 100 km west of IS37, yielding a good agreement in terms of vertical wavenumber spectrum amplitudes and slopes. This suggests that the radar and infrasound‐based effective sound‐speed profiles represent low‐ and high‐wavenumber regimes of the same “universal” GW spectrum. The results illustrate that infrasound allows for probing fine‐scale dynamics not well captured by other techniques, suggesting that infrasound can provide a complementary technique to probe atmospheric GWs.

Diurnal Cycle of Rapid Air Temperature Fluctuations at Jezero Crater: Probability Distributions, Exponential Tails, Scaling, and Intermittency

AbstractWe study the diurnal cycle of rapid thermal fluctuations observed by the Mars Environmental Dynamics Analyzer, onboard the Perseverance rover at Jezero Crater, as a function of local time and season. In this context, rapid refers to periods between 15 min and half a second. Some insight is also provided into wind fluctuations that are the base for most of the existing theories on turbulent flows. The results expand the observations from previous Mars missions, namely Viking, Mars Pathfinder, and Phoenix, and they add to our knowledge of near‐surface fluctuations on Mars. (a) Probability distribution functions of the fluctuations are determined and found to have exponential tails. This means that models that represent the interaction within the environment and with the surface as a stochastic forcing need to account for the sudden events responsible for the exponential tails. (b) Power density spectra are calculated and show several dynamical regimes with different slopes associated to forcing, an intermediate regime, and a higher frequency regime. All change with time of the day. The results imply that the fastest regime is not a universal scenario for the temperature fluctuations near the surface. (c) The scale dependence of the fluctuations confirms the existence of intermittent outbursts associated to the slower fluctuations, possibly associated to the larger scale structures, and explains why the spectral density slopes do not follow Kolmogorov's law. Understanding the role of larger scale structures would help refine scaling theories of the near‐surface Martian atmosphere and its interactions with the surface.

A new process-based and scale-aware desert dust emission scheme for global climate models – Part I: Description and evaluation against inverse modeling emissions

Abstract. Desert dust accounts for most of the atmosphere's aerosol burden by mass and produces numerous important impacts on the Earth system. However, current global climate models (GCMs) and land-surface models (LSMs) struggle to accurately represent key dust emission processes, in part because of inadequate representations of soil particle sizes that affect the dust emission threshold, surface roughness elements that absorb wind momentum, and boundary-layer characteristics that control wind fluctuations. Furthermore, because dust emission is driven by small-scale (∼ 1 km or smaller) processes, simulating the global cycle of desert dust in GCMs with coarse horizontal resolutions (∼ 100 km) presents a fundamental challenge. This representation problem is exacerbated by dust emission fluxes scaling nonlinearly with wind speed above a threshold wind speed that is sensitive to land-surface characteristics. Here, we address these fundamental problems underlying the simulation of dust emissions in GCMs and LSMs by developing improved descriptions of (1) the effect of soil texture on the dust emission threshold, (2) the effects of nonerodible roughness elements (both rocks and green vegetation) on the surface wind stress, and (3) the effects of boundary-layer turbulence on driving intermittent dust emissions. We then use the resulting revised dust emission parameterization to simulate global dust emissions in a standalone model forced by reanalysis meteorology and land-surface fields. We further propose (4) a simple methodology to rescale lower-resolution dust emission simulations to match the spatial variability of higher-resolution emission simulations in GCMs. The resulting dust emission simulation shows substantially improved agreement against regional dust emissions observationally constrained by inverse modeling. We thus find that our revised dust emission parameterization can substantially improve dust emission simulations in GCMs and LSMs.