Variations In Wind Velocity Research Articles

Energy and exergy based study on a box type solar cooker coupled with a Fresnel lens magnifier

ABSTRACT The variation of energy and exergy efficiency of a Box-type solar cooker (BTSC) incorporated with a Fresnel lens magnifier (FLMG) is evaluated in this study. The comparison in energy and exergy efficiency was investigated in the absence and presence of the FLMG to determine the efficiency variation of the BTSC by addition of the FLMG. With the implementation of FLMG, the average values of energy and exergy efficiencies had increased by 10% and 8.52%, respectively. The magnitude of energy efficiency with and without FLMG decreased with time, whereas the exergy efficiency enhanced with time for both cases. The manuscript discusses the effect of different thermodynamic parameters like temperature difference, energy and exergy output, absorber mean plate temperature, and heat losses in the modified cooker. The total heat loss coefficient ranged from 5.48 to 8.44 W/m2K and depended on the variation of wind velocity. The maximum heat loss and mean plate temperature were found to be 120 kJ and 128.3°C, respectively. The time for sensible heating was reduced by 16 mins by the implementation of the FLMG. The addition of the lens showed an increase in the Area concentration ratio (AR) of the BTSC by 48.7%. By comparing the cost and energy usage of LPG (Liquefied Petroleum Gas), the payback period and the quantity of carbon dioxide reduced per month were calculated as 3.19 years and 8.265 kg, respectively.

Performance Comparison of Different Building Shapes Using a Wind Tunnel and a Computational Model

A building-integrated wind turbine (BIWT) is an alternative way to assess renewable energy. BIWTs produces their own energy without relying on fossil fuels. However, only a few researchers have studied BIWTs. Greater wind velocity (V) results in greater potential energy (P). The aerodynamic design has an important role to play in increasing wind velocity and reducing turbulence intensity. CFD simulations taken from previous research have revealed that round-shaped buildings increase velocity up to 30%. This study focuses on the wind response of square and top-rounded-shaped building models, and their optimization based on variations in wind velocity. Wind tunnel studies were conducted to study wind flow around the building, followed by a computer simulation to verify the results. In a wind tunnel, three BIWT models (1:150 in scale) located in Seoul, South Korea (terrain B), were evaluated. The results of the study show that the streamline should be followed when installing wind turbines on rectangular rooves with flat surfaces. This method allows wind speed to be elevated significantly, when compared to a turbine at a higher height. In addition, round corners can produce wind velocity that is up to 34% greater than sharp corners beside a building. In summary, this paper presents a five-step analysis framework that can be used by researchers who wish to analyze BIWTs through wind tunnel experiments and CFD.

Dynamic behaviour of pre-stressed concrete transmission poles under synoptic wind loading

A numerical model capable of predicting the dynamic response of pre-stressed concrete transmission poles under both the mean and fluctuating components of synoptic wind loads is developed in this study. A full non-linear dynamic analysis is conducted under a time history variation of wind velocity. The peak total responses, such as conductors’ reactions and poles’ base moments, are determined from this analysis. The same analysis is repeated in a quasi-static manner. Dynamic amplification factors (DAF), defined as the ratio between the maximum response based on a non-linear dynamic analysis and the corresponding value based on a quasi-static analysis, are calculated for the poles and the conductors to quantify the dynamic impact of synoptic wind loads. This factor is used to assess the importance of including the resonant component while estimating the response of the transmission poles. In addition, gust response factors (GRF) defined as the ratio between the peak and mean responses are evaluated and compared to GRF recommended by ASCE-74 (2010). A parametric study is conducted on three pre-stressed concrete transmission line systems. The mean value of the incoming wind speed is the main variable included in the parametric study. It is found that the resonant effect is dominant in the conductors at low wind speeds and the poles exhibit high dynamic response at higher wind speeds.

A novel Green Leaf‐hopper Flame optimization algorithm for competent frequency regulation in hybrid microgrids

AbstractA proficient frequency regulation scheme has been explored in this work for two interconnected hybrid microgrids () comprised of multiple renewable energy sources, like solar‐thermal units, wind turbine generator units, solar photovoltaic, biogas turbine, biodiesel generator, and storage units. A new optimization algorithm has been formulated to replicate the photo‐tactic swarming behavior of green leafhoppers named Green Leaf‐hopper Flame optimization algorithm (GLFOA) to tune the system controllers (proportional integral (PI)/proportional derivative (PD)/proportional integral derivative (PID) controllers). The superiority of GLFOA is confirmed by comparing the performance with several popular optimization algorithms. To assess the stability of the several rigorous tests have been conducted considering availability/nonavailability of renewable resources, gusty wind, real‐time variation of solar radiation and wind velocities along with the random load disturbances. GLFOA tuned PID controllers were found to be the best to contain the frequency deviations. The maximum peak overshoot, undershoot, and settling time obtained by GLFOA tuned PID controllers are 0.01051 Hz, −0.00764 Hz, and 14.15 s, respectively, which are within an acceptable limit. Further, there is an improvement of 0.15% in the performance index obtained by GLFOA over its counterpart obtained by grey wolf optimization, confirming the superiority of the GLFOA tuned controller.

An SSM-PSO Based MPPT Scheme for Wind Driven DFIG System

In this work, a searching space minimization-based particle swarm optimization (SSM-PSO) scheme has been proposed for maximum power point tracking (MPPT) in a doubly fed induction generator (DFIG) based wind energy conversion system (WECS). DFIG displays non-linearity in <i>P</i> &#x2013; &#x03C9; characteristics. So different types of conventional and optimization-based schemes are developed for MPPT. The drawbacks in the conventional perturb and observe (P&#x0026;O) scheme has been successfully abolished by the proposed SSM-PSO method. Because of its weather-insensitive nature, the conventional P&#x0026;O MPP tracking scheme results in the fluctuation of DFIG output under a sudden change in wind speed. To avoid this problem, maximum and minimum limits for the optimal rotor speed have been determined in the proposed SSM-PSO scheme. Further, the obtained limits for rotor speed are employed to improve the searching space within the non-linear <i>P</i> &#x2013; &#x03C9; curve. This initial confinement of particles to a limited searching space in SSM-PSO results in a faster response of the system. Since the proposed SSM-PSO is atmosphere sensitive, it avoids fluctuations under an abrupt variation in wind velocity. The improved initialization part of SSM-PSO leads to better dynamic characteristics compared to existing P&#x0026;O and optimization-based schemes. The proposed SSM-PSO scheme is implemented for a 2MW DFIG system in MATLAB Simulink atmosphere and showed satisfactory results.

Performance of Gradient-Based Optimizer for Optimum Wind Cube Design

Renewable energy is a safe and limitless energy source that can be utilized for heating, cooling, and other purposes. Wind energy is one of the most important renewable energy sources. Power fluctuation of wind turbines occurs due to variation of wind velocity. A wind cube is used to decrease power fluctuation and increase the wind turbine’s power. The optimum design for a wind cube is the main contribution of this work. The decisive design parameters used to optimize the wind cube are its inner and outer radius, the roughness factor, and the height of the wind turbine hub. A Gradient-Based Optimizer (GBO) is used as a new metaheuristic algorithm in this problem. The objective function of this research includes two parts: the first part is to minimize the probability of generated energy loss, and the second is to minimize the cost of the wind turbine and wind cube. The Gradient-Based Optimizer (GBO) is applied to optimize the variables of two wind turbine types and the design of the wind cube. The metrological data of the Red Sea governorate of Egypt is used as a case study for this analysis. Based on the results, the optimum design of a wind cube is achieved, and an improvement in energy produced from the wind turbine with a wind cube will be compared with energy generated without a wind cube. The energy generated from a wind turbine with the optimized cube is more than 20 times that of a wind turbine without a wind cube for all cases studied.

Employing Spectral Analysis to Obtain Dispersion Parameters in an Atmospheric Environment Driven by a Mesoscale Downslope Windstorm

Considering the influence of the downslope windstorm called “Vento Norte” (VNOR; Portuguese for “North Wind”) in planetary boundary layer turbulent features, a new set of turbulent parameterizations, which are to be used in atmospheric dispersion models, has been derived. Taylor’s statistical diffusion theory, velocity spectra obtained at four levels (3, 6, 14, and 30 m) in a micrometeorological tower, and the energy-containing eddy scales are used to calculate neutral planetary boundary layer turbulent parameters. Vertical profile formulations of the wind velocity variances and Lagrangian decorrelation time scales are proposed, and to validate this new parameterization, it is applied in a Lagrangian Stochastic Particle Dispersion Model to simulate the Prairie Grass concentration experiments. The simulated concentration results were shown to agree with those observed.

Overview of solar eclipse of 21st June 2020 and its impact on solar irradiance, surface ozone and different meteorological parameters over eight cities of India

• First time study of annular solar eclipse effect simultaneously at eight stations of India. • Stations are located nearly perpendicular to the eclipse axis with magnitude 98.6% to 77.2%. • Substantial reduction in solar radiation, surface ozone & temperature is evident. • Atmospheric cooling from eclipse induced dynamical changes to the meteorological parameters. The present study is aimed to investigate the variation in solar radiance, surface ozone, temperature, relative humidity and wind velocity during the most recent and one of the most significant annular solar eclipses of 21st June 2020. Effects of solar eclipse have been analyzed first time at eight different cities of India located nearly perpendicular to the eclipse axis having an eclipse magnitude from 98.6 % to 77.2 %. Significant reductions in solar irradiance at different stations were found during the maximum phase of the solar eclipse due to the occultation of the Sun by the Moon. With the progression of the solar eclipse, surface ozone concentrations were also found to be decreasing and reached to its minimum value during the maximum phase of eclipse and then after the end of the eclipse started regaining their original behavior. Overall, the change in ozone was found to be proportional to eclipse magnitude. A decrease of ozone levels ranged from 30 % to 65 % over all the stations. In addition to the above, atmospheric cooling from the solar eclipse of 21st June 2020 induced dynamical changes to the meteorological parameters (temperature, relative humidity and wind speed) with the change being most prominent during the maximum phase of the solar eclipse.

CFD modelling and prototype testing of a Vertical Axis Wind Turbines in planetary cluster formation

This study aims to improve the applicability of Vertical Axis Wind Turbines (VAWTs) by investigating their feasibility in a novel planetary cluster configuration by observing its effect on efficiency and overall power density. Computational Fluid Dynamics (CFD) simulations were carried out using a two-dimensional vertical axis wind turbine model in ANSYS Fluent 2020 R1. This software was used to solve the transient k-omega (SST) turbulence model. For the isolated VAWT the wind velocity, rotor radius and tip speed ratio were varied to find the optimum turbine performance at a given parameter. A peak efficiency of 34.05% was attained and equivalent configuration used as the “sun” turbine in the novel planetary design. The parametric study of the novel set up was conducted with the PCD (Pitch Circle Diameter) and oblique angular (ϕ) position of the smaller “planet” turbines being varied in relation to the “sun” turbine. The planetary system was then evaluated in terms of efficiency improvements against the isolated VAWT model. Use of the “planet” turbines resulted in power extraction from the free stream which in turn creates varying wind velocities and improved the efficiency of the central “sun” turbine. The optimal PCD was found to be 5D (3.75 m) and the optimum angular position of the “planets” was discovered at 30°. Ultimately this gave a percentage increase of 1.01% from 33.04% to 34.05% when comparing the “sun” turbine of the planetary arrangement to the optimum isolated respectively. An average improvement of 4% over the range of tip speed ratios (TSR) was found. Lastly, a scale model of the isolated VAWT was constructed and tested through wind tunnel experiments. The characteristic curve correlation was found between the CFD and experimental results which allowed validation of the CFD models.

Influence of Zonal Wind Velocity Variation on Equatorial Plasma Bubble Occurrences Over Southeast Asia

AbstractThe present study aims to investigate the influence of the zonal wind velocity on equatorial plasma bubble (EPB) occurrences over Southeast Asia. The observation of the EPB occurrence is obtained from the GPS Rate of TEC change index. Meanwhile, the zonal winds were measured using a Fabry‐Perot interferometer located at Kototabang and Chiang Mai stations, and the height of F layer was acquired using an ionosonde at Chumphon station near the magnetic equator. This is the first study to report the influence of zonal wind velocity variation on EPB occurrences with the presence and absence of EPB using GPS data in the Southeast Asian sector. The results illustrated that the average magnitude of zonal wind velocity during the presence of EPB (78 ± 23 m/s) was higher than that of its absence (68 ± 21 m/s). It was observed using long‐term data analyses which led to in‐depth analyses. The analysis of temporal variation of zonal wind variation demonstrated that the zonal winds during EPB were higher in the evening compared to midnight and postmidnight periods from medium to high solar activities. The dependence of zonal wind velocity on EPB over local time was obtained based on the analysis which utilized the data collected during equinox in high solar activity. Besides that, a positive correlation was obtained between the zonal wind velocity and EPB occurrences during pre‐reversal enhancement (PRE) corroborated the effects of zonal wind influence on PRE, and thus EPB occurrences.

2D CFD Simulation Study on the Performance of Various NACA Airfoils

The wind is an energy source that has the properties of a clean, free, and readily available energy source. However, the efficiency of the existing rotors used to harness wind power is still not satisfactory. Thus, in this current study, the development and aerodynamic performance investigation of ten NACA airfoils comprising of five symmetrical and five non-symmetrical airfoils have been analyzed through the computational fluids dynamic (CFD) simulation approach. The main motive of this study was to investigate the aerodynamic performance of NACA airfoils to be used on a vertical axis wind turbine (VAWT), which will assist in further understanding the physics of the interaction between airflow and the wind turbine blades. The simulation was performed using two-dimensional computational models based on an unsteady state K-omega Shear Stress Transport (SST) turbulence model. This study covers a parametric study based on the variations of tip-speed ratios and constant wind velocity. The aerodynamic performances are evaluated in terms of torque, torque coefficient, and also power coefficient. The performance of NACA0018 was found to be the best among the other airfoils with a power coefficient of 0.3. NACA0010 displayed the lowest power coefficient among the other airfoils but had a more extensive operating range compared to the other airfoils. However, for non-symmetrical NACA airfoils, NACA2421 scored the highest power coefficient, followed by NACA4412. It was also found that most of the non-symmetrical NACA airfoils can operate at a higher range of tip-speed ratios compared to the symmetrical NACA airfoils.

Nursing Home Wind Environment Evaluation in Northern China - A Case Study in Dezhou

As the rapid development of institution-based care for the elderly people, the nursing home’s outdoor wind environment research has become an important topic including wind potential evaluation as well as wind comfort analysis. In this study, the wind environment of a nursing home located in Dezhou, northern China has been evaluated quantitatively according to CFD methods. The parameters related to the wind environment including average wind velocity, wind velocity variation range and area proportion of shadow wind, comfort wind and risky wind regions has been calculated. Results showed the annual average wind velocity of the nursing home’s outdoor environment was 1.69m/s and its variation range was 40.41%. The area proportions of shadow wind, comfort wind and risky wind regions were 23.00%, 75.35% and 1.65%. This indicated that the wind environment optimization of the nursing home should be focused on decreasing the shadow wind regions and dismiss the risky wind regions, and relative optimization suggestions were proposed.

Modeling and Stability Analysis of Dual Rotor Axial Flux PMG for Wind Turbine Applications

This paper focuses on mathematical modeling and stability analysis of double rotor xil flux generator. The wind generator is modeled using dq reference frame theory. The cogging torque and gravitational force during starting time is considered for the modeling of the generator. There re several type of generators have been suggested for wind turbine applications out of which dual rotor PM generator having the lot of advantages than the other types of the permanent magnet generator based direct driven wind energy conversion system. Modeling of dual rotor PM generator is developed in the MATLAB. The simulated model is analyzed for various input and output variables. The stability of the proposed system is also analyzed by deriving small signal model of the wind turbine systems. The input wind velocity variations and grid fault conditions are considered for analysis of the system. The results of the proposed system is analyzed for various values of turbine speed.

A Comparative Study of Wind Tunnel Tests and Design Codes in Evaluation of Along-Wind Effects on Towers

This study aims to estimate the wind loads acting on a tower structure by comparing and reviewing design codes and the results of wind tunnel tests. To this end, the modal properties of the tower were identified through short-term on-site measurements of the Busan Tower in Korea. The wind load acting on the tower was calculated using four design codes: KBC2009 (Korea), ASCE7-10 (USA), EUROCODE (Europe), and AIJ2004 (Japan). Additionally, force measurement tests and aeroelastic model tests were conducted for comparison. The results obtained indicated that the design wind velocity of each design code differed slightly, reflecting the individual characteristics of each country. The base shear force, base moment, and maximum displacement obtained from each design code were similar to those obtained in the wind tunnel tests. The magnitudes of the base moments and maximum displacements calculated by each design code were in the order of KBC &gt; AIJ ≈ EUROCODE &gt; ASCE7. The overall results indicate that each design code reasonably estimates the wind forces and the responses of the tower and also has an appropriate safety margin. The scatter in the predicted wind loads occurs primarily from the variations in the design wind velocity in the respective design codes.

An approach to minimize aircraft motion bias in multi-hole probe wind measurements made by small unmanned aerial systems

Abstract. A multi-hole probe mounted on an aircraft provides the air velocity vector relative to the aircraft, requiring knowledge of the aircraft spatial orientation (e.g., Euler angles), translational velocity and angular velocity to translate this information to an Earth-based reference frame and determine the wind vector. As the relative velocity of the aircraft is typically an order of magnitude higher than the wind velocity, the extracted wind velocity is very sensitive to multiple sources of error including misalignment of the probe and aircraft coordinate system axes, sensor error and misalignment in time of the probe and aircraft orientation measurements in addition to aerodynamic distortion of the velocity field by the aircraft. Here, we present an approach which can be applied after a flight to identify and correct biases which may be introduced into the final wind measurement. The approach was validated using a ground reference, different aircraft and the same aircraft at different times. The results indicate a significant reduction in wind velocity variance at frequencies which correspond to aircraft motion.

Effect of wind condition on unintended hydrogen release in a hydrogen refueling station

Ambient condition, especially the wind condition, is an important factor to determine the behavior of hydrogen diffusion during hydrogen release. However, only few studies aim at the quantitative study of the hydrogen diffusion in a wind-exist condition. And very little researches aiming at the variable wind condition have been done. In this paper, the hydrogen diffusion in different wind condition which including the constant wind velocity and the variable wind velocity is investigated numerically. When considering the variable wind velocity, the UDF (user defined function) is compiled. Characteristics of the FGC (flammable gas cloud) and the HMF (hydrogen mass fraction) are analyzed in different wind condition and comparisons are made with the no-wind condition. Results indicate that the constant wind velocity and the variable wind velocity have totally different effect for the determination of hydrogen diffusion. Comparisons between the constant wind velocity and the variable wind velocity indicate that the variable wind velocity may cause a more dangerous situation since there has a larger FGC volume. More importantly, the wind condition has a non-negligible effect when considering the HMF along the radial direction. As the wind velocity increases, the distribution of the HMF along the radial direction is not Gaussian anymore when the distance between the release hole and the observation line exceeds to a critical value. This work can be a supplement of the research on the hydrogen release and diffusion and a valuable reference for the researchers.

A new binary variant with transfer functions of Harris Hawks Optimization for binary wind turbine micrositing

Harris Hawks Optimization (HHO) is a new algorithm proposed in 2019 for nontrivial, nature-inspired optimization problems. The original version of the HHO algorithm was proposed to solve continuous optimization problems. This study suggested a new binary variant of the HHO for the binary wind turbine micrositing problem, which was named as HHObin. The HHObin algorithm proposed for converting the continuous version of the HHO algorithm into binary version is equipped with ceil (T1), ceilRound (T2), ceilFloor (T3), Roundfloor (T4), moduleBase A (T5), moduleBase B (T6), T7 and T8 transfer functions. Thus, the original HHO algorithm was converted to the HHObin algorithm for using to solve any binary problems. In this study, the HHObin algorithm developed for using in solving binary wind turbines was placed on the turbines at the constant wind velocity, at the angular constant wind velocity and at the angular variable wind velocity on a 2000 × 2000 area with different grid methods. The performance of the HHObin algorithm was compared with other studies in the literature. The results obtained showed that HHObin algorithm was more successful than other methods.

Limited Power Point Tracking for a Small-Scale Wind Turbine Intended to Be Integrated in a DC Microgrid

Limited power point tracking (LPPT) is emerging as a new technology for power management controllers for small-scale wind turbines (SSWTs) thanks to its advantages in terms of operation flexibility, economy and system security. LPPT operates in such a way that power requested by the user can be extracted from the wind turbine while respecting constraints. However, operating in LPPT mode still requires a deep understanding to obtain a compromise between minimizing power oscillations and transient response. For that, three LPPT power control strategies for an SSWT intended to be integrated in a direct current (DC) urban microgrid are investigated. These methods concern perturb and observe (P&amp;O) with fixed step size, P&amp;O based on Newton’s method and P&amp;O based on the fuzzy logic (FL) technique. The experimental results highlight that all methods function correctly and reach the limited power point (LPP). The FL method improves dynamic performances with more steady oscillations around LPP compared to fixed step size and Newton’s methods. The sudden variation of wind velocity and power lead us to conclude that the FL method ensures a good balance between reducing oscillation of wind turbine (WT) output power around the operating point and convergence of rising time toward LPP.

Development of a sustainable energy system utilizing a new molten-salt based hybrid thermal energy storage and electrochemical energy conversion technique

In the present study, an integrated solar and wind based cogeneration system is developed for power and ammonia production. A new molten-salt based thermal energy storage and electrochemical energy conversion technique is utilized, which includes electrochemical ammonia synthesis, direct ammonia fuel cell, and thermal energy storage system. A transient energy and exergy analyses is performed on the developed system considering the hourly variations in wind velocities as well as solar intensities. The energy efficiency of the overall system on monthly average days varies between a minimum value of 29.4% and a maximum value of 38.7% across the year. In addition, the exergy efficiency of the developed system is found to vary between 30.2% and 39.8%. Furthermore, the daily ammonia production is found to reach peak value of 4292.3 kmol/day during the year. Moreover, the maximum discharge capacity of the molten salt-based direct ammonia fuel cell system attains a value of 31.8 MWh across the year. Several parametric studies are also performed to assess the effects of varying operating conditions on the performance of the developed system as well as subsystem units.

Event analysis and real‐time validation of doubly fed induction generator‐based wind energy system with grid reactive power exchange under sub‐synchronous and super‐synchronous modes

AbstractThe insertion of renewable power generators into the power system network has been promoted by the environment protection aspects. Doubly fed induction generator (DFIG)‐based wind energy system is one of the most viable technologies for sustained power generation. This paper focuses on the operational analysis of DFIG‐based wind energy conversion systems (WECS) with real‐time experimental validation. An event analysis is executed under sub‐synchronous and super‐synchronous speeds with the variation in wind velocity and reactive power exchange by controlling the rotor side converter and grid side converter under MATLAB/Simulink platform. The results of the analysis with reactive power exchange can be utilized for the enhanced control of power electronic converters of DFIG‐based WECS for better support to the grid. The validation of results is accomplished by emulation of 2 MW DFIG‐based three blade wind turbine system in the laboratory under a real‐time hardware‐in‐the‐loop platform.