Wide Range Of Wind Speeds Research Articles

Energy harvesting from wind-induced bridge vibrations via electromagnetic transduction

Energy harvesting from wind-induced vibrations of long-span bridges through electromagnetic devices is herein addressed. A coupled model, describing the bridge structure excited by aeroelastic wind forces and equipped with harvesting devices mounted along the bridge girder, is derived by reducing bridge dynamics via a modal analysis. The model is employed to maximise the harvested power with respect to the stiffness and the electromagnetic damping parameter of the harvesting devices, depending on the characteristics of the approaching wind flow. Numerical results obtained in the case of a bridge-like structure similar to the Great Belt East Bridge are presented and discussed, showing model soundness and effectiveness. The influence of the dynamical coupling among principal structure and harvesting devices on the harvesting process is investigated. Moreover, in order to overcome possible feasibility drawbacks related to a real-time adjustment of harvester parameters, a simplified tuning procedure is proposed, resulting effective in a wide wind-speed range.

Performance Analysis of a Speed Sensor-Less Grid Connected DFIG based Wind Energy Conversion System using Nine Switch Converter

This paper presents the performance study of a Double Fed Induction Generator (DFIG) based Wind Energy Conversion System (WECS) by using the Nine Switch Converter and a new phase locked loop based slip speed estimator is also proposed to obtain speed sensor-less stator field oriented vector control operation. The Nine switch converter having two sets of independent three phase output terminals at two different frequency levels, one set is connected to the rotor winding through slip ring and brushes and other set is connected to the grid through interfacing inductors and a PLL based slip estimator is incorporated with nine switch converter controller for speed sensor-less operation of variable speed wind energy conversion system. The nine switch converter based DFIG system is used for decoupled control of stator active and reactive power exchange between the stator of the DFIG and the grid to ensure maximizing the power generation at unity power factor under varying wind speed and speed sensor-less vector control is incorporated with optimal speed tracking and optimal pitch angle controllers to capture maximum wind energy when wind speed remains within the rated range; and to restrict the captured wind energy to the turbine’s rated level when speed crosses the rated limit to prevent overloading and outage of the wind turbine respectively like convetional back-to-back converter. As compared to conventional back-to-back ac/ac converters, the numbers of power semiconductor switches are reduced in the proposed nine switch converter. The proposed topology has the advantages of reduced cost, more efficient (reduced switching loss) and reduced installation area over back-to-back converter. Simulation has been carried out in MATLAB/Simulink environment and results have been analyzed. Results show that the proposed speed sensor-less DFIG based wind turbine using nine-switch converter can operate at its optimum energy level for a wide range of wind speed and is capable to control active and reactive power independently and reduces the number of switching devices thereby minimizing the cost of the system.

Modified Speed Sensor-less Grid Connected DFIG based WECS

This paper presents a new Phase Locked Loop (PLL) based slip speed estimator for speed sensor less field oriented vector control operation of variable speed grid connected Wind Energy Conversion System (WECS). Three phase rotor current is used to design a PLL based slip estimator for speed sensor-less vector control operation of rotor side converter. The proposed speed sensor-less grid connected Double Fed Induction Generator (DFIG) based WECS is used for decoupled control of stator active and reactive power to ensure maximizing the power generation at unity power factor under varying wind speed. The speed sensor-less Vector control scheme is also incorporated with an optimal speed tracking controller for maximum energy capture in the rated wind speed range and restrict the mechanical output power to the rated value using pitch angle control when the wind velocity crosses rated limit to prevent overloading and outage of the wind turbine. The proposed method does not require the information of rotor speed or position for speed sensor less DFIG based WECS unlike other published methods. Simulation has been carried out in MATLAB/Simulink environment and results have been analyzed. Results show that the proposed speed sensor-less DFIG system can operate at its optimum energy level for a wide range of wind speed and is capable for satisfactory operation of the variable speed WECS.

Theoretical framework of feedback aerodynamic control of flutter oscillation for long-span suspension bridges by the twin-winglet system

This paper presents an active aerodynamic control method of flutter oscillation for long-span suspension bridges with a newly designed twin-winglet system. The key point of this paper is to establish the theoretical framework for active control of bridge flutter by a pair of rotatable winglets beyond the deck, of which motions are determined by the feedback control algorithm. Through utilizing aerodynamic forces generated by these winglets, this active control system can improve aerodynamic stability of long-span suspension bridges to some extent. The modeling and control of this system mainly focus on practical feasibility, in which the relative rotations rather than driving forces of both winglets are selected as the control variables in the paper. State space expression of the control system is proposed to handle problems of high order terms elimination and decoupling for control variables. Since the unobservability of aerodynamic states, model reduction technique is adopted in the design of observer and controller. The active control algorithm presented in this paper is verified by numerical simulations, and the stabilizing mechanism and energy consumption are discussed as well. It shows good effectiveness and robustness of this active aerodynamic control device in a wide range of wind speeds for flutter suppression.

Pinning of reaction fronts by burning invariant manifolds in extended flows

We present experiments on the behavior of reaction fronts in extended, vortex-dominated flows in the presence of an imposed wind. We use the ferroin-catalyzed, excitable Belousov-Zhabotinsky chemical reaction, which produces pulse-like reaction fronts. Two time-independent flows are studied: an ordered (square) array of vortices and a spatially disordered flow. The flows are generated with a magnetohydrodynamic forcing technique, with a pattern of magnets underneath the fluid cell. The magnets are mounted on a translation stage which moves with a constant speed Vd under the fluid, resulting in motion of the vortices within the flow. In a reference frame moving with magnets, the flow is equivalent to one with stationary vortices and a uniform wind with speed W = Vd. For a wide range of wind speeds, reaction fronts pin to the vortices (in a co-moving reference frame), propagating neither forward against the wind nor being blown backward. We analyze this pinning phenomenon and the resulting front shapes using a burning invariant manifold (BIM) formalism. The BIMs are one-way barriers to reaction fronts in the advection-reaction-diffusion process. Pinning occurs when several BIMs overlap to form a complete barrier that spans the width of the system. In that case, the shape of the front is determined by the shape of the BIMs. For the ordered array flow, we predict the locations of the BIMs numerically using a simplified model of the velocity field for the ordered vortex array and compare the BIM shapes to the pinned reaction fronts. We also explore transient behavior of the fronts (before reaching their steady state) to highlight the one-way nature of the BIMs.

Dual-branch reed for resonant cavity wind energy harvester with enhanced performances

A structure of dual-branch piezoelectric unimorph reed with the resonant cavity of a harmonica to harvest wind energy for the wireless sensor networks was introduced in this paper. After the experiments and simulation analysis, a new mathematical model was established for further research on this structure. The vibration of the reed in the resonant cavity was dealt with as the damping forced vibration of a triangular pulse excitation. This model well explained why the dual-branch reed can vibrate much stronger than the no-branch reed. The experiment proved that the proposed structure and model are feasible and efficacious, the dual-branch reed not only increases the vibration amplitude of the piezoelectric reed but also exhibits a wide wind speed range. A prototype wind energy harvester with a wind inlet dimension of 25 mm × 25 mm can generate an maximum power of 6.7 mW and have an efficiency of 3.5%, with wind speed from 3.2 m/s to 16 m/s.

Air–sea fluxes of oxygenated volatile organic compounds across the Atlantic Ocean

Abstract. We present air–sea fluxes of oxygenated volatile organics compounds (OVOCs) quantified by eddy covariance (EC) during the Atlantic Meridional Transect cruise in 2012. Measurements of acetone, acetaldehyde, and methanol in air as well as in water were made in several different oceanic provinces and over a wide range of wind speeds (1–18 m s−1). The ocean appears to be a net sink for acetone in the higher latitudes of the North Atlantic but a source in the subtropics. In the South Atlantic, seawater acetone was near saturation relative to the atmosphere, resulting in essentially zero net flux. For acetaldehyde, the two-layer model predicts a small oceanic emission, which was not well resolved by the EC method. Chemical enhancement of air–sea acetaldehyde exchange due to aqueous hydration appears to be minor. The deposition velocity of methanol correlates linearly with the transfer velocity of sensible heat, confirming predominant airside control. We examine the relationships between the OVOC concentrations in air as well as in water, and quantify the gross emission and deposition fluxes of these gases.

Field study of film spreading on a sea surface

The results of a field study of surface film spreading on the sea surface are presented. The experiments were carried out in the coastal zone of the Black Sea in a wide range of wind speeds and wave conditions. Vegetable oil was used for preparing the surfactants. It was found that at moderate and strong wind speeds the slicks take on a shape similar to an ellipse and are orientated in the direction of the air flow. An increase in the speed of the spreading slick along its major axis with strong wind was discovered.

Efficient Direct-Drive Small-Scale Low-Speed Wind Turbine

Abstract There is growing need for the green, reliable, and cost-effective power solution for the expanding wireless microelectronic devices. In many scenarios, these needs can be met through a small-scale wind energy portable turbine (SWEPT) that operates near ground level where wind speed is of the order of few meters per second. SWEPT is a three-bladed, 40 cm rotor diameter, direct-drive, horizontal-axis wind turbine that has very low cut-in wind speed of 1.7 m/s. It operates in a wide range of wind speeds between 1.7 m/s and 10 m/s and produces rated power output of 1 W at wind speed of 4.0 m/s. The wind turbine is capable of producing electrical power up to 9.8 W at wind speed of 10 m/s. The maximum efficiency of SWEPT was found to be around 21% which makes it one of the most efficient wind turbines reported at the small scale and low wind speed. These advancements open many new opportunities for embedding and utilizing wireless and portable devices.

Numerical and experimental estimation of convective heat transfer coefficient of human body under strong forced convective flow

A human body may occasionally experience strong forced convective flow that exceeds 10m/s, such as walking in the vicinity of tall buildings with a strong wind blowing against, involving in a severe tropical storm or typhoon, climbing a mountain against strong wind, or in an industrial air-shower like system during purging treatment. The objective of this study is to investigate the convective heat transfer around the human body, especially in forced convective flow in the context of outdoor environment. Wind tunnel experiment was conducted with a thermal manikin covering a wide range of wind speeds from 1.08 to 12.67m/s. CFD simulation corresponding to the wind tunnel experimental setup was then carried out and its prediction accuracy was validated. Experimental results showed that the whole body convective heat transfer coefficient under a uniform velocity of 12.67m/s was 71W/m2/K and 76W/m2/K in case of facing the wind and crossing the wind direction, respectively.

Power Factor Control in a Wind Energy Conversion System via Synchronous Generator Excitation

This paper proposes a novel control technique to improve the power factor over a wide range of wind speeds in a wind energy conversion system (WECS) using a current source inverter (CSI) and an electrically excited synchronous generator. The system consists of diode rectifier on the generator side, while a pulsewidth modulated CSI is on the grid side. In the proposed control scheme, the generator excitation is controlled with the wind speed to improve the grid power factor, while the control freedoms of the CSI are used to regulate the power output of the WECS to meet maximum power point tracking of wind energy. Theoretical analysis is conducted to investigate the feasibility and limits of this approach. The simulation model for the proposed WECS is developed, and the simulation results confirm the validity of the theoretical analysis. With the proposed power factor control scheme, improvements of grid-side power factor are achieved over a wider range of wind speeds.

Simulation Study of Nonlinear PI-Controller with Quasi-Z-Source Derived Push-Pull Converter

Abstract This paper is focused on the control issues of the quasi-Z-source derived push-pull converter with integrated magnetic elements. The proposed converter is intended for applications that require a high gain of the input voltage and galvanic isolation, i.e. power conditioning systems for renewable energy sources, such as variable speed wind turbines with direct driven permanent magnet synchronous generators. Magnitude and frequency of the output voltage of such turbines are variable due to intermittent nature of the wind power. Despite number of advantages converter has complicated dynamic behavior. Simulations showed change of stability margin depending on current operation point of the wind turbine and output load. Closed loop control system should provide fast response and stable operation in the wide range of wind speeds. Simulations showed that the conventional PI-controller with saturation cannot satisfy those requirements. Nonlinear PI-controller was derived by adding adjustment block to the conventional PI-controller. Adjustment block is drastically changing proportional and integral gains of the controller according to sign of the output voltage error. Proposed controller is compared with conventional one by means of simulation in PSIM. Simulation results prove that proposed nonlinear control system has improved regulator performance.

Hybrid Fuzzy Sliding Mode Control of a DFIG Integrated into the Network

This paper presents the study of a variable speed wind energy conversion system using a Doubly Fed Induction Generator (DFIG) based on a Fuzzy sliding mode control (FSMC) applied to achieve control of active and reactive powers exchanged between the stator of the DFIG and the grid to ensure a Maximum Power Point Tracking (MPPT) of a wind energy conversion system. However the principal drawback of the sliding mode, is the chattering effect which characterized by torque ripple, this phenomena is undesirable and harmful for the machines, it generates noises and additional forces of torsion on the machine shaft. In order to reduce the chattering effect, the Sign function of sliding mode controller’s discontinuous part is replaced by a fuzzy logic; we will have the fuzzy sliding mode controller (FSMC). The FSMC makes it possible to combine the performances of the two types of controllers (SMC and FLC) and eliminates the chattering effect. The proposed control algorithm is applied to a DFIG where the stator is directly connected to the grid and the rotor is connected to a three-level converter structure NPC to suppress low level harmonics, higher frequencies will be filtered out by the machine. Second goal of this paper is to extract a maximum of power; the rotor side converter is controlled by using a stator flux-oriented strategy. The decoupling created by the control between active and reactive stator power allows keeping the power factor close to unity. Simulation results show that the wind turbine can operate at its optimum energy for a wide range of wind speed. Both simulation and validation results show effectiveness of the proposed control strategy is in terms of power regulation. Moreover, the fuzzy sliding mode approach is arranged so as to reduce the chattering produced in the generated power that could lead to increased mechanical stress because of strong torque variations. DOI: http://dx.doi.org/10.11591/ijpeds.v3i4.4072

Electromagnetic resonant cavity wind energy harvester with optimized reed design and effective magnetic loop

We demonstrate a new electromagnetic resonant cavity wind energy harvester combined with dual-branch reed and turning fork vibrator to harvest wind energy for wireless sensor nodes. Compared with electromagnetic structures in the past, the proposed magnetic circuit has a better linearity and a magnetic loop that more effectively increases the rate of the change of magnetic flux. Moreover, the motion of the free magnet is directed vertically to the direction of the magnetic pole for a zero resistance startup mode and a compact construction. We also designed a tuning fork-like reed structure to reduce system losses. To achieve maximum output power, we defined a virtual resistance to deal with the decrease of the electromotive in the circuit caused by the Lorentz force between the magnet and the induced magnetic field of the coils when the circuit is turned on. The dimensions of the wind inlet were 60mm×60mm. The maximum output power and conversion efficiency can reach 56mW at wind speed of 20.3m/s and 2.3% at wind speed of 4m/s, respectively, with wind speed from 3.2m/s to 21.2m/s. The experiments show that this electromagnetic wind energy harvester has high output power and wide wind speed range.

The Effects of Leaf Area Density Variation on the Particle Collection Efficiency in the Size Range of Ultrafine Particles (UFP)

Carbonaceous particles were generated during a "sooting burn" experiment to explore how heterogeneity in horizontal leaf area density (LAD) within the canopy impacts the ultrafine particle (UFP) collection efficiency at the branch-scale. To address this goal, wind tunnel experiments and a particle-size resolving model, which couples the turbulent flow field within the vegetated volume and the collection efficiency, were presented. Three scenarios were examined in a wind-tunnel packed with Juniperus chinensis branches: An LAD that was uniformly distributed, linearly increasing and linearly decreasing along the longitudinal or mean wind direction. The concentration measurements were conducted at multiple locations within the vegetated volume to evaluate the performance of the proposed model needed in discerning the role of LAD heterogeneity on UFP collection. Differences not exceeding 20% were found between modeled and measured concentration for all particle sizes across a wide range of wind speeds. The overall particle collection efficiency was found to be primarily governed by the spatially integrated LAD when differences in aerodynamic attributes (e.g., foliage drag) were accounted for. When combined with earlier studies, the results suggest that one parameter linking the laminar boundary layer conductance to the Schmidt number depends on particle size.

On the Exchange of Momentum over the Open Ocean

AbstractThis study investigates the exchange of momentum between the atmosphere and ocean using data collected from four oceanic field experiments. Direct covariance estimates of momentum fluxes were collected in all four experiments and wind profiles were collected during three of them. The objective of the investigation is to improve parameterizations of the surface roughness and drag coefficient used to estimate the surface stress from bulk formulas. Specifically, the Coupled Ocean–Atmosphere Response Experiment (COARE) 3.0 bulk flux algorithm is refined to create COARE 3.5. Oversea measurements of dimensionless shear are used to investigate the stability function under stable and convective conditions. The behavior of surface roughness is then investigated over a wider range of wind speeds (up to 25 m s−1) and wave conditions than have been available from previous oversea field studies. The wind speed dependence of the Charnock coefficient α in the COARE algorithm is modified to , where m = 0.017 m−1 s and b = −0.005. When combined with a parameterization for smooth flow, this formulation gives better agreement with the stress estimates from all of the field programs at all winds speeds with significant improvement for wind speeds over 13 m s−1. Wave age– and wave slope–dependent parameterizations of the surface roughness are also investigated, but the COARE 3.5 wind speed–dependent formulation matches the observations well without any wave information. The available data provide a simple reason for why wind speed–, wave age–, and wave slope–dependent formulations give similar results—the inverse wave age varies nearly linearly with wind speed in long-fetch conditions for wind speeds up to 25 m s−1.

Neural MPPT of Variable-Pitch Wind Generators With Induction Machines in a Wide Wind Speed Range

This paper proposes a maximum power point tracking (MPPT) technique for variable-pitch wind generators with induction machines (IMs), which can suitably be adopted in both the maximum power range and the constant-power range of the wind speed. To this aim, an MPPT technique based on the growing neural gas (GNG) wind turbine surface identification and corresponding function inversion has been adopted here to cover also the situation of variable-power region. To cope with the constant-power region, the blade pitch angle has been controlled on the basis of the closed-loop control of the mechanical power absorbed by the IM. The wind speed is then estimated in the constant-power region on the basis of the actual position of the blade pitch angle. The proposed methodology has been verified both in numerical simulation and experimentally on a properly devised test setup. In addition, a comparison between the proposed approach and the previously developed GNG-based MPPT has been performed on a real wind speed profile. Finally, the effect of the torsional stiffness of the mechanical transmission system has been analyzed.

A Gain Scheduled Method for Speed Control of Wind Driven Doubly Fed Induction Generator

This paper proposes a gain scheduled control method for a doubly fed induction generator driven by a wind turbine. The purpose is to design a variable speed control system so as to extract the maximum power in the region below the rated wind speed. Gain scheduled control approach is applied in order to achieve high performance over a wide range of wind speed. A double loop configuration is adopted. In the inner loop, the rotor speed is used as the scheduling parameter, while a function of wind and rotor speed is used as the scheduling parameter in the outer loop. It is verified in simulations that a high tracking performance has been achieved.

0624 広い風速域で運用可能な垂直軸風車ブレード(OS6-5 噴流,後流およびはく離流れ現象の探求と先端的応用,OS6 噴流,後流およびはく離流れ現象の探求と先端的応用)

0624 広い風速域で運用可能な垂直軸風車ブレード(OS6-5 噴流,後流およびはく離流れ現象の探求と先端的応用,OS6 噴流,後流およびはく離流れ現象の探求と先端的応用)

Simulation Analysis of Savonius Turbine with Self-Rotating Blades

This paper analyzed the advantages of traditional Savonius (S-type) turbine and the reasons of its low efficiency, proposed a new type of turbine with self-rotating blades and surrounded by a rectifier, and studied the aerodynamic performance by numerical simulations. The turbine is composed of a rectifier and a rotor, the rectifier consists by straight and arc segments which can accelerate the wind speed and adjust the inflow wind angle. The self-rotating blade can reduce the impacted area acting on the leeward blade by wind and arm of the impact torque, therefore reduces the resistant torque of the blade, and the driving torque acting on the windward blade is almost the same with traditional S-type turbine, which can increase the overall driving torque. The result shows that the new turbine has the advantages as below: wide range of wind speed for effective working, high power coefficient (Cp), suitable for low wind speed aera etc. Although the flow field in S-type turbine is complex separating flow, the performance of the turbine proposed in this paper is improved and is better than traditional S-type turbine in numerical simulation which is worth for spreading.