WorldWideScience

Sample records for wind load measurements

  1. Assessment of wind turbine load measurement instrumentation

    Energy Technology Data Exchange (ETDEWEB)

    Morfiadakis, E.; Papadopoulos, K. [CRES (Greece); Borg, N. van der [ECN, Petten (Netherlands); Petersen, S.M. [Risoe, Roskilde (Denmark); Seifert, H. [DEWI, Wilhelmshaven (Germany)

    1999-03-01

    In the framework of Sub-Task3 `Wind turbine load measurement instrumentation` of EU-project `European Wind Turbine Testing Procedure Development`, the load measurement techniques have been assessed by laboratory, full scale and numerical tests. The existing methods have been reviewed with emphasis on the strain gage application techniques on composite materials and recommendations are provided for the optimisation of load measurement techniques. (au) EU. 14 refs.

  2. Influence of wind conditions on wind turbine loads and measurement of turbulence using lidars

    NARCIS (Netherlands)

    Sathe, A.R.

    2012-01-01

    Variations in wind conditions influence the loads on wind turbines significantly. In order to determine these loads it is important that the external conditions are well understood. Wind lidars are well developed nowadays to measure wind profiles upwards from the surface. But how turbulence can be

  3. Load Measurements

    DEFF Research Database (Denmark)

    Kock, Carsten Weber; Vesth, Allan

    The report describes Load measurements carried out on a given wind turbine. The aim of the measurement program regarding the loads on the turbine is to verify the basic characteristics of the wind turbine and loads on the blades, the rotor and the tower, using [Ref 1], [Ref2] and [Ref 3]. Regarding...... the fatigue loads, the rotor, blades and tower moments are presented. The fatigue loads are evaluated using rainflow counting described in detail in Ref. [1]. The 1Hz equivalent load ranges are calculated at different wind speeds. All information regarding the instrumentation is collected in [ref 4] and [ref...

  4. Wind Loads on Structures

    DEFF Research Database (Denmark)

    Dyrbye, Claes; Hansen, Svend Ole

    Wind loads have to be taken into account when designing civil engineering structures. The wind load on structures can be systematised by means of the wind load chain: wind climate (global), terrain (wind at low height), aerodynamic response (wind load to pressure), mechanical response (wind...... pressure to structural response) and design criteria. Starting with an introduction of the wind load chain, the book moves on to meteorological considerations, atmospheric boundary layer, static wind load, dynamic wind load and scaling laws used in wind-tunnel tests. The dynamic wind load covers vibrations...... induced by wind turbulence, vortex shedding, flutter and galloping. The book gives a comprehensive treatment of wind effects on structures and it will be useful for consulting engineers designing wind-sensitive structures. It will also be valuable for students of civil engineering as textbook...

  5. Wind Structure and Wind Loading

    DEFF Research Database (Denmark)

    Brorsen, Michael

    The purpose of this note is to provide a short description of wind, i.e. of the flow in the atmosphere of the Earth and the loading caused by wind on structures. The description comprises: causes to the generation of windhe interaction between wind and the surface of the Earthhe stochastic nature...... of windhe interaction between wind and structures, where it is shown that wind loading depends strongly on this interaction...

  6. Calibration procedures for improved accuracy of wind turbine blade load measurement

    Energy Technology Data Exchange (ETDEWEB)

    Dahlberg, J.Aa. [Aeronautical Research Inst. of Sweden, Bromma (Sweden); Johansson, Hjalmar [Teknikgruppen AB, Sollentuna (Sweden)

    1996-12-01

    External loads acting on wind turbine blades are mainly transferred via the hub to the rest of the structure. It is therefore a normal approach to measure the loads acting on the turbine by load measurements in the blade roots. The load measurement is often accomplished by measurements of strain on the surface of the blade or the hub. The strain signals are converted to loads by applying calibration factors to the measurements. This paper deals with difficulties associated with load measurements on two different wind turbines; one with strain gauges applied to a steel hub where a linear stress-load relationship is expected and the other with strain gauges applied to the GFRP blade close to the bearings where strong non-linearity`s and temperature effects are expected. This paper suggests calibration methods to overcome these problems. 2 refs, 11 figs

  7. Influence of wind loading

    OpenAIRE

    MAVLONOV RAVSHANBEK ABDUJABBOROVICH; VAKKASOV KHAYRULLO SAYFULLAHANOVICH

    2015-01-01

    Each wind load is determined by a probabilistic-statistical method based on the concept of “equivalent static wind load”, on the assumption that structural frames and components/cladding behave elastically in strong wind.

  8. Power and loads for wind turbines in yawed conditions. Analysis of field measurements and aerodynamic predictions

    Energy Technology Data Exchange (ETDEWEB)

    Boorsma, K. [ECN Wind Energy, Petten (Netherlands)

    2012-11-15

    A description is given of the work carried out within the framework of the FLOW (Far and Large Offshore Wind) project on single turbine performance in yawed flow conditions. Hereto both field measurements as well as calculations with an aerodynamic code are analyzed. The rotors of horizontal axis wind turbines follow the changes in the wind direction for optimal performance. The reason is that the power is expected to decrease for badly oriented rotors. So, insight in the effects of the yaw angle on performance is important for optimization of the yaw control of each individual turbine. The effect of misalignment on performance and loads of a single 2.5 MW wind turbine during normal operation is investigated. Hereto measurements at the ECN Wind Turbine Test Site Wieringermeer (EWTW) are analyzed from December 2004 until April 2009. Also, the influence of yaw is studied using a design code and results from this design code are compared with wind tunnel measurements.

  9. Extreme Design Loads Calibration of Offshore Wind Turbine Blades through Real Time Measurements

    DEFF Research Database (Denmark)

    Natarajan, Anand; Vesth, Allan; Lamata, Rebeca Rivera

    2014-01-01

    moment is extrapolated. This is found to possess smaller scaling factors in measurements over six months as compared to both the flap and edge moments, indicating that the contemporaneous load component of an extrapolated load should possess much smaller magnitude than its maxima.......Blade Root flap and Edge moments are measured on the blades of a 3.6MW offshore wind turbine in normal operation. Ten minute maxima of the measurements are sampled to determine the extreme blade root flap moment, edge moment and resultant moment over six month duration. A random subset...... root flap moment, edge moment obtained by extrapolation. The validation yields valuable information on prescribing the slope of the local extrapolation curve at each mean wind speed. As an alternative to determining the contemporaneous loads for each primary extrapolated load, the blade root resultant...

  10. Performance enhancement and load reduction on wind turbines using inflow measurements

    Energy Technology Data Exchange (ETDEWEB)

    Abildgaard Kragh, K.

    2013-06-15

    Wind energy is being applied at a larger and larger scale worldwide, and is one of the technologies eligible for accommodating the increasing demand for renewable energy. However, wind energy is still not competitive compared to technologies that are based on fossil energy sources. Therefore, much wind energy research is focused on decreasing the cost of the energy that can be produced from the wind. The cost of energy can for example be decreased by ensuring that wind turbines are operated in a way that ensures that the maximum amount of energy is extracted, and that the turbines are not loaded excessively. The operation of a wind turbine is governed by a number of controllers that are based on a series of sensors and actuators. Classical wind turbine control utilizes sensors for measuring turbine parameters such as rotor speed, power and shaft torque, as well as actuators for applying generator torque and collective pitch angle changes. Thus, classical wind turbine control schemes are based on measurements of the effects of the inflow on the turbine. Therefore, the reactions of the control system to the inflow changes are inherently delayed compared to the actual inflow changes. Because of the inherent delay of the control system, the ability of the system to react promptly to inflow changes is limited. Control schemes that are based on inflow measurements have been developed to overcome the limitations of the classical wind turbine control system. By measuring the inflow directly, actuation can be initiated instantly as the inflow changes. If the inflow is measured upstream of the turbine, actuation can be initiated prior to the occurrence of a wind speed change at the turbine. Hereby, even the actuator delay can be compensated for. Upstream inflow measurements could for example be acquired using ''Light Detection and Ranging''. In this thesis, the potentials for improving the power production and decreasing the load variations of horizontal axis upwind turbines

  11. Validation of Simplified Load Equations Through Loads Measurement and Modeling of a Small Horizontal-Axis Wind Turbine Tower

    Energy Technology Data Exchange (ETDEWEB)

    Dana, Scott [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Van Dam, Jeroen J [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Damiani, Rick R [National Renewable Energy Laboratory (NREL), Golden, CO (United States)

    2018-04-24

    As part of an ongoing effort to improve the modeling and prediction of small wind turbine dynamics, the National Renewable Energy Laboratory (NREL) tested a small horizontal-axis wind turbine in the field at the National Wind Technology Center. The test turbine was a 2.1-kW downwind machine mounted on an 18-m multi-section fiberglass composite tower. The tower was instrumented and monitored for approximately 6 months. The collected data were analyzed to assess the turbine and tower loads and further validate the simplified loads equations from the International Electrotechnical Commission (IEC) 61400-2 design standards. Field-measured loads were also compared to the output of an aeroelastic model of the turbine. In particular, we compared fatigue loads as measured in the field, predicted by the aeroelastic model, and calculated using the simplified design equations. Ultimate loads at the tower base were assessed using both the simplified design equations and the aeroelastic model output. The simplified design equations in IEC 61400-2 do not accurately model fatigue loads and a discussion about the simplified design equations is discussed.

  12. Measuring footprints of wind turbine fatigue loads using monitoring methods. Final report

    Energy Technology Data Exchange (ETDEWEB)

    Soeker Holger [ed.; Oestman, Anders; Thor, Sven-Erik [Aeronautical Research Inst. of Sweden, Bromma (Sweden)

    2001-03-01

    In the described research project the fatigue monitoring technique is applied on three 500kW wind turbines of the same type operating under different external conditions i.e. stand alone, wind farm and complex terrain conditions. Respective sites have been selected in Germany (stand alone and wind farm) and in Greece (complex terrain). During the measurement campaigns three new data bases have been created holding on-line monitoring data sets and time series data of the wind turbines' key loads. As a fourth data source time series measurements from the wind farm at Alsvik, Sweden, have been used for the project work. The central aspect of the work has been to establish 'footprints' of the measured load quantities for varying external conditions and to develop and accumulate skills and experience in reading the load information stored in such fatigue load 'footprints'. The term 'footprint' refers to the rainflow cycle frequency spectra of the observed load quantity recorded during a representative time interval together with a set of parameters describing the external and operational conditions during that time interval. In fatigue monitoring the rainflow counting data reduction technique is applied to the measured load samples on-line, reducing hardware memory and off-line evaluation demands. It has been attempted to introduce a framework of few statistic parameters that describe the fatigue load footprint and also relate to external physical conditions (s.a. average wind speed, turbulence etc.). In addition to the traditional formulations of statistic parameters in terms of time series statistics, special parameters adapted to on-line rainflow counted data sets have been examined. On-line fatigue footprint monitoring has so far been applied as a diagnostic tool. In the project the development of a scheme has been started that shall enable to normalise the footprinting results and furthermore to extrapolate them to external

  13. Wind Load Assessment of a Large Radar Antenna using Measurements and Simulation

    Science.gov (United States)

    Weerasinghe, Rohitha; Bunn, Thomas

    2017-11-01

    Radar structures are subject to heavy wind loads due to the physical size of such structures. This paper contains the methodology and assessment of a project which set out to accomplish an improved method for modelling wind loads on a radar structure. The new method employs the use of computational fluid dynamics (CFD) to create a simulation of the conditions. Several studies on the approach to CFD testing were undertaken to optimise the process. Dimensions of domain volume and mesh density were examined for their effect on the computed solutions, as well as run time. Once an efficient set-up had been found, a scale model of the radar was analysed. Pressure distributions across the antenna face were studied from four cases, in which the prevailing wind approached from a different direction relative to the system (0°, 45°,90° and 180°). To validate the results from the CFD, a low-speed wind tunnel test was conducted. The experimental measurements were compared to the computed results and common trends were shown to exist between both sets of data.

  14. Performance Enhancement and Load Reduction on Wind Turbines Using Inflow Measurements

    DEFF Research Database (Denmark)

    Kragh, Knud Abildgaard

    excessively. The operation of a wind turbine is governed by a number of controllers that are based on a series of sensors and actuators. Classical wind turbine control utilizes sensors for measuring turbine parameters such as rotor speed, power and shaft torque, as well as actuators for applying generator...... “Light Detection and Ranging”. In this thesis, the potentials for improving the power production and decreasing the load variations of horizontal axis upwind turbines by applying inflow measurement based control are assessed. The potential for increasing the power output through improved yaw alignment...... is studied by analyzing operational data from different turbines, and through experiments with a modified yaw controller. The results demonstrate that there is no significant potential for increased power output through improved yaw alignment for well calibrated turbines. The potential for increasing...

  15. Wind Climate Parameters for Wind Turbine Fatigue Load Assessment

    DEFF Research Database (Denmark)

    Toft, Henrik Stensgaard; Svenningsen, Lasse; Moser, Wolfgang

    2016-01-01

    established from the on-site distribution functions of the horizontal mean wind speeds, the 90% quantile of turbulence along with average values of vertical wind shear and air density and the maximum flow inclination. This paper investigates the accuracy of fatigue loads estimated using this equivalent wind...... climate required by the current design standard by comparing damage equivalent fatigue loads estimated based on wind climate parameters for each 10 min time-series with fatigue loads estimated based on the equivalent wind climate parameters. Wind measurements from Boulder, CO, in the United States...... and Høvsøre in Denmark have been used to estimate the natural variation in the wind conditions between 10 min time periods. The structural wind turbine loads have been simulated using the aero-elastic model FAST. The results show that using a 90% quantile for the turbulence leads to an accurate assessment...

  16. Comparison of calculated and measured blade loads on a full-scale tilting proprotor in a wind tunnel

    Science.gov (United States)

    Johnson, W.

    1980-01-01

    The loads measured in a wind tunnel on a full-scale tilting proprotor are compared with calculated results. The data consists primarily of oscillatory beamwise bending moments at 35% radial station, oscillatory spindle chord bending moments, and oscillatory pitch link loads. The measured and calculated results as a function of thrust are compared over a range of nacelle angles from 0 to 75 deg, and a range of speeds from 80 to 185 knots.

  17. Wind Loads on Ships and Offshore Structures Determined by Model Tests, CFD and Full-Scale Measurements

    DEFF Research Database (Denmark)

    Aage, Christian

    1998-01-01

    Wind loads on ships and offshore structures have until recently been determined only by model tests, or by statistical methods based on model tests. By the development of Computational Fluid Dynamics or CFD there is now a realistic computational alternative. In principle, both methods should...... be validated systematically against full-scale measurements, but due to the great practical difficulties involved, this is almost never done. In this investigation, wind loads on a seagoing ferry and on a semisubmersible platform have been determined by model tests and by CFD. On the ferry, full......-scale measurements have been carried out as well. The CFD method also offers the possibility of a computational estimate of scale effects related to wind tunnel model testing. An example of such an estimate on the ferry is discussed. This work has been published in more details in Proceedings of BOSS'97, Aage et al...

  18. Variability of load and net load in case of large scale distributed wind power

    OpenAIRE

    Holttinen, Hannele; Kiviluoma, J.; Estanqueiro, Ana; Gómez-Lázaro, E.; Raw, Barry; Dobschinski, Jan; Meibon, Peter; Lannoye, Eamonn; Aigner, Tobias; Wan, Yih H.; Milligan, Michael

    2011-01-01

    Large scale wind power production and its variability is one of the major inputs to wind integration studies. This paper analyses measured data from large scale wind power production. Comparisons of variability are made across several variables: time scale (10-60 minute ramp rates),number of wind farms, and simulated vs. modeled data. Ramp rates for Wind power production, Load (total system load) and Net load (load minus wind power production) demonstrate how wind power increases the...

  19. Variability of load and net load in case of large scale distributed wind power

    OpenAIRE

    Holttinen, Hannele; Kiviluoma, Juha; Estanqueiro, Ana; Aigner, Tobias; Wan, Yih-Huei; Milligan, Michael R.

    2010-01-01

    Large scale wind power production and its variability is one of the major inputs to wind integration studies. This paper analyses measured data from large scale wind power production. Comparisons of variability are made across several variables: time scale (10-60 minute ramp rates), number of wind farms, and simulated vs. modeled data. Ramp rates for Wind power production, Load (total system load) and Net load (load minus wind power production) demonstrate how wind power increases the net loa...

  20. Variation of Loads on Offshore Wind Turbine Drivetrains During Measured Shutdown Events

    DEFF Research Database (Denmark)

    Natarajan, Anand

    2016-01-01

    -megawatt wind turbine located at an offshore wind farm are correlated with corresponding observations of shutdowns on surrounding wind turbines. The observed wind turbines have multiple shutdowns at high mean wind speeds due to wind speed variations near cut-out. Through the use of an Inverse First Order...

  1. Wind loads on solar energy roofs

    NARCIS (Netherlands)

    Geurts, C.P.W.; Bentum, C.A. van

    2007-01-01

    This paper presents an overview of the wind loads on roofs, equipped with solar energy products, so called Active Roofs. Values given in this paper have been based on wind tunnel and full scale measurements, carried out at TNO, and on an interpretation of existing rules and guidelines. The results

  2. Load prediction of stall regulated wind turbines

    Energy Technology Data Exchange (ETDEWEB)

    Bjoerck, A.; Dahlberg, J.Aa. [Aeronautical Research Inst. of Sweden, Bromma (Sweden); Carlen, I. [Chalmers Univ. of Technology, Goeteborg (Sweden). Div. of Marine Structural Engineering; Ganander, H. [Teknikgruppen AB, Sollentua (Sweden)

    1996-12-01

    Measurements of blade loads on a turbine situated in a small wind farm shows that the highest blade loads occur during operation close to the peak power i.e. when the turbine operates in the stall region. In this study the extensive experimental data base has been utilised to compare loads in selected campaigns with corresponding load predictions. The predictions are based on time domain simulations of the wind turbine structure, performed by the aeroelastic code VIDYN. In the calculations a model were adopted in order to include the effects of dynamic stall. This paper describes the work carried out so far within the project and key results. 5 refs, 10 figs

  3. Ultimate loading of wind turbines

    DEFF Research Database (Denmark)

    Larsen, Gunner Chr.; Ronold, K.; Ejsing Jørgensen, Hans

    1999-01-01

    An extreme loading study has been conducted comprising a general wind climate analysis as well as a wind turbine reliability study. In the wind climate analysis, the distribution of the (horizontal) turbulence standard deviation, conditioned on the meanwind speed, has been approximated by fitting......, a design turbulence intensity for off-shore application is proposed which, in the IEC code framework, is applicable for extreme as well as for fatigue loaddetermination. In order to establish a rational method to analyse wind turbine components with respect to failure in ultimate loading, and in addition...... to the event of failure in ultimate loading in flapwise bending in the normal operating condition of a site-specific turbine....

  4. Derivation of a new parametric impulse response matrix utilized for nodal wind load identification by response measurement.

    Science.gov (United States)

    Kazemi Amiri, A; Bucher, C

    2015-05-26

    This paper provides new formulations to derive the impulse response matrix, which is then used in the problem of load identification with application to wind induced vibration. The applied loads are inversely identified based on the measured structural responses by solving the associated discrete ill-posed problem. To this end - based on an existing parametric structural model - the impulse response functions of acceleration, velocity and displacement have been computed. Time discretization of convolution integral has been implemented according to an existing and a newly proposed procedure, which differ in the numerical integration methods. The former was evaluated based on a constant rectangular approximation of the sampled data and impulse response function in a number of steps corresponding to the sampling rate, while the latter interpolates the sampled data in an arbitrary number of sub-steps and then integrates over the sub-steps and steps. The identification procedure was implemented for a simulation example as well as an experimental laboratory case. The ill-conditioning of the impulse response matrix made it necessary to use Tikhonov regularization to recover the applied force from noise polluted measured response. The optimal regularization parameter has been obtained by L-curve and GCV method. The results of simulation represent good agreement between identified and measured force. In the experiments the identification results based on the measured displacement as well as acceleration are provided. Further it is shown that the accuracy of experimentally identified load depends on the sensitivity of measurement instruments over the different frequency ranges.

  5. Model of wind shear conditional on turbulence and its impact on wind turbine loads

    DEFF Research Database (Denmark)

    Dimitrov, Nikolay Krasimirov; Natarajan, Anand; Kelly, Mark C.

    2015-01-01

    fatigue load is achieved. The proposed wind shear model based on the wind measurements is thereby probabilistic in definition, with shear jointly distributed with wind turbulence. A simplified model for the wind shear exponent is further derived from the full stochastic model. The fatigue loads over......We analyse high-frequency wind velocity measurements from two test stations over a period of several years and at heights ranging from 60 to 200 m, with the objective to validate wind shear predictions as used in load simulations for wind turbine design. A validated wind shear model is thereby...... different turbine components are evaluated under the full wind measurements, using the developed wind shear model and with standard wind conditions prescribed in the IEC 61400-1 ed. 3. The results display the effect of the Wöhler exponent and reveal that under moderate turbulence, the effect of wind shear...

  6. Wind load reduction for light-weight heliostats

    OpenAIRE

    Pfahl, Andreas; Brucks, Antje; Holze, Carsten

    2014-01-01

    At SolarPACES 2012 conference a new heliostat concept was presented. It is equipped with wireless communication, sandwich facets, wind protection devices for wind load reduction, rim drives with winch wheels and ground anchor foundation. Crucial for the development of the light-weight structures is the precise determination of the maximum loads. By full scale wind load measurements the duration of the peak loads could be determined. They are caused by gusts with such short duration that their...

  7. Wind and load variability in the Nordic countries

    DEFF Research Database (Denmark)

    Holttinen, Hannele; Rissanen, Simo; Larsén, Xiaoli Guo

    This publication analysed the variability of wind production and load in Denmark, Finland, Sweden, and the Nordic region as a whole, based on real data measured from large-scale wind power during 2009–2011. The Nordic-wide wind power time series was scaled up such that Sweden had same amount...... the three years analysed in this publication there were few storm incidents and they did not produce dramatic wind power ramps in the Nordic region. Wind and load variations are not correlated between the countries, which is beneficial from the viewpoint of wind integration. The smoothing effect is shown...... as reduction of variability from a single country to Nordic-wide wind power. The impact of wind power on the variability that the system experiences is evaluated by analysing the variability of net load with different wind power penetration levels. The Nordic-wide wind power production increases the highest...

  8. The nature of wind turbine fatigue loads in wind farms

    DEFF Research Database (Denmark)

    Larsen, Gunner Chr.; Larsen, Torben J.; Aagaard Madsen, Helge

    2013-01-01

    agreements were found between the extend of wake affected direction regimes. As for the magnitude of the (mean) wake loading, the tower top moments were under-estimated with of the order 15%, whereas the tower bottom moments were found to agree well with the measured results.......The aim of the present paper is to further validate the predictive capability of the DWM/HAWC2 package for simulation of structural loadings in wind farms. The validation in particular focus on tower fatigue loading characteristics (i.e. equivalent moments) as function of turbine relative position...... tower top and bottom bending moments as well as tower the top torsion moment. The numerical predictions are based on a simulation package, where the Dynamic Wake Meandering model is interfaced with the in-house aeroelastic code HAWC2. Comparing simulated and measured tower fatigue loading, good...

  9. Load Extrapolation During Operation for Wind Turbines

    DEFF Research Database (Denmark)

    Toft, Henrik Stensgaard; Sørensen, John Dalsgaard

    2008-01-01

    In the recent years load extrapolation for wind turbines has been widely considered in the wind turbine industry. Loads on wind turbines during operations are normally dependent on the mean wind speed, the turbulence intensity and the type and settings of the control system. All these parameters...... must be taken into account when characteristic load effects during operation are determined. In the wind turbine standard IEC 61400-1 a method for load extrapolation using the peak over threshold method is recommended. In this paper this method is considered and some of the assumptions are examined...

  10. On the relationship between wind profiles and the STS ascent structural loads

    Science.gov (United States)

    Smith, Orvel E.; Adelfang, Stanley I.; Whitehead, Douglas S.

    1989-01-01

    The response of STS ascent structural load indicators to the wind profile is analyzed. The load indicator values versus Mach numbers are calculated with algorithms using trajectory information. The ascent load minimum margin concept is used to show that the detailed wind profile structure measured by the Jimsphere wind system is not needed to assess the STS rigid body structural wind loads.

  11. LIDAR Wind Speed Measurements of Evolving Wind Fields

    Energy Technology Data Exchange (ETDEWEB)

    Simley, E.; Pao, L. Y.

    2012-07-01

    Light Detection and Ranging (LIDAR) systems are able to measure the speed of incoming wind before it interacts with a wind turbine rotor. These preview wind measurements can be used in feedforward control systems designed to reduce turbine loads. However, the degree to which such preview-based control techniques can reduce loads by reacting to turbulence depends on how accurately the incoming wind field can be measured. Past studies have assumed Taylor's frozen turbulence hypothesis, which implies that turbulence remains unchanged as it advects downwind at the mean wind speed. With Taylor's hypothesis applied, the only source of wind speed measurement error is distortion caused by the LIDAR. This study introduces wind evolution, characterized by the longitudinal coherence of the wind, to LIDAR measurement simulations to create a more realistic measurement model. A simple model of wind evolution is applied to a frozen wind field used in previous studies to investigate the effects of varying the intensity of wind evolution. LIDAR measurements are also evaluated with a large eddy simulation of a stable boundary layer provided by the National Center for Atmospheric Research. Simulation results show the combined effects of LIDAR errors and wind evolution for realistic turbine-mounted LIDAR measurement scenarios.

  12. Design Load Basis for Offshore Wind turbines

    DEFF Research Database (Denmark)

    Natarajan, Anand; Hansen, Morten Hartvig; Wang, Shaofeng

    2016-01-01

    DTU Wind Energy is not designing and manufacturing wind turbines and does therefore not need a Design Load Basis (DLB) that is accepted by a certification body. However, to assess the load consequences of innovative features and devices added to existing offshore turbine concepts or new offshore...... turbine concept developed in our research, it is useful to have a full DLB that follows the current design standard and is representative of a general DLB used by the industry. It will set a standard for the offshore wind turbine design load evaluations performed at DTU Wind Energy, which is aligned...

  13. Wind loads on flat plate photovoltaic array fields (nonsteady winds)

    Science.gov (United States)

    Miller, R. D.; Zimmerman, D. K.

    1981-01-01

    Techniques to predict the dynamic response and the structural dynamic loads of flat plate photovoltaic arrays due to wind turbulence were analyzed. Guidelines for use in predicting the turbulent portion of the wind loading on future similar arrays are presented. The dynamic response and the loads dynamic magnification factor of the two array configurations are similar. The magnification factors at a mid chord and outer chord location on the array illustrated and at four points on the chord are shown. The wind tunnel test experimental rms pressure coefficient on which magnification factors are based is shown. It is found that the largest response and dynamic magnification factor occur at a mid chord location on an array and near the trailing edge. A technique employing these magnification factors and the wind tunnel test rms fluctuating pressure coefficients to calculate design pressure loads due to wind turbulence is presented.

  14. Preview-based Asymmetric Load Reduction of Wind Turbines

    DEFF Research Database (Denmark)

    Madsen, Mathias; Filsø, Jakob; Soltani, Mohsen

    2012-01-01

    Fatigue loads on wind turbines caused by an asymmetric wind field become an increasing concern when the scale of wind turbines increases. This paper presents a model based predictive approach to reduce asymmetric loads by using Light Detection And Ranging (LIDAR) measurements. The Model Predictive...... Controller (MPC) developed is based on a model with individual blade pitching to utilize the LIDAR measurements. The MPC must also maintain a given power reference while satisfying a set of actuator constraints. The designed controller was tested on a 5 MW wind turbine in the FAST simulator and compared...

  15. Effects of Icing on Wind Turbine Fatigue Loads

    International Nuclear Information System (INIS)

    Frohboese, Peter; Anders, Andreas

    2007-01-01

    The external conditions occurring at cold climate sites will affect wind turbines in different ways. The effects of ice accretion on wind turbines and the influence on the turbine fatigue loads are examined. The amount of icing prior to turbine installation needs to be estimated by using standard measurement data and considering the geometry of the proposed turbine. A procedure to calculate the expected ice accretion on wind turbines out of standard measurement data is explained and the results are discussed. Different parameters to describe the accreted ice on the turbine are examined separately in a fatigue load calculation. The results of the fatigue load calculation are discussed and selected cases are presented

  16. Combining Unsteady Blade Pressure Measurements and a Free-Wake Vortex Model to Investigate the Cycle-to-Cycle Variations in Wind Turbine Aerodynamic Blade Loads in Yaw

    Directory of Open Access Journals (Sweden)

    Moutaz Elgammi

    2016-06-01

    Full Text Available Prediction of the unsteady aerodynamic flow phenomenon on wind turbines is challenging and still subject to considerable uncertainty. Under yawed rotor conditions, the wind turbine blades are subjected to unsteady flow conditions as a result of the blade advancing and retreating effect and the development of a skewed vortical wake created downstream of the rotor plane. Blade surface pressure measurements conducted on the NREL Phase VI rotor in yawed conditions have shown that dynamic stall causes the wind turbine blades to experience significant cycle-to-cycle variations in aerodynamic loading. These effects were observed even though the rotor was subjected to a fixed speed and a uniform and steady wind flow. This phenomenon is not normally predicted by existing dynamic stall models integrated in wind turbine design codes. This paper couples blade pressure measurements from the NREL Phase VI rotor to a free-wake vortex model to derive the angle of attack time series at the different blade sections over multiple rotor rotations and three different yaw angles. Through the adopted approach it was possible to investigate how the rotor self-induced aerodynamic load fluctuations influence the unsteady variations in the blade angles of attack and induced velocities. The hysteresis loops for the normal and tangential load coefficients plotted against the angle of attack were plotted over multiple rotor revolutions. Although cycle-to-cycle variations in the angles of attack at the different blade radial locations and azimuth positions are found to be relatively small, the corresponding variations in the normal and tangential load coefficients may be significant. Following a statistical analysis, it was concluded that the load coefficients follow a normal distribution at the majority of blade azimuth angles and radial locations. The results of this study provide further insight on how existing engineering models for dynamic stall may be improved through

  17. Validation of wind loading codes by experiments

    NARCIS (Netherlands)

    Geurts, C.P.W.

    1998-01-01

    Between 1994 and 1997, full scale measurements of the wind and wind induced pressures were carried out on the main building of Eindhoven University of Technology. Simultaneously, a comparative wind tunnel experiment was performed in an atmospheric boundary layer wind tunnel. In this paper, the

  18. A model of rotationally-sampled wind turbulence for predicting fatigue loads in wind turbines

    Science.gov (United States)

    Spera, David A.

    1995-01-01

    Empirical equations are presented with which to model rotationally-sampled (R-S) turbulence for input to structural-dynamic computer codes and the calculation of wind turbine fatigue loads. These equations are derived from R-S turbulence data which were measured at the vertical-plane array in Clayton, New Mexico. For validation, the equations are applied to the calculation of cyclic flapwise blade loads for the NASA/DOE Mod-2 2.5-MW experimental HAWT's (horizontal-axis wind turbines), and the results compared to measured cyclic loads. Good correlation is achieved, indicating that the R-S turbulence model developed in this study contains the characteristics of the wind which produce many of the fatigue loads sustained by wind turbines. Empirical factors are included which permit the prediction of load levels at specified percentiles of occurrence, which is required for the generation of fatigue load spectra and the prediction of the fatigue lifetime of structures.

  19. Characterising Turbulence Intensity for Fatigue Load Analysis of Wind Turbines

    DEFF Research Database (Denmark)

    Hansen, Kurt Schaldemose; Larsen, Gunner Chr.

    2005-01-01

    Turbulence in wind velocity presents a major factor for modern wind turbine design as cost reduction as are sort for the dynamic structures. Therefore this paper contains a parametrisation of the turbulence intensity at given sites, relevant for the calculation of fatigue loading of wind turbines....... The parameterisation is based on wind speed measurements extracted from the “Database on Wind Characteristics” (www.winddata.com). The parameterisation is based on the LogNormal distribution, which has proven to be suitable distribution to describe the turbulence intensity distribution....

  20. Analysis of extreme wind events at Høvsøre and the effect on wind turbine loads

    DEFF Research Database (Denmark)

    Hannesdóttir, Ásta; Kelly, Mark C.; Mann, Jakob

    used to simulate wind turbine response in time domain. The simulations are made for the DTU 10 MW reference wind turbine. Load analysis shows that the maximum tilt moment on the tower yaw bearing correlates well with the wind shear of the measurements. When these loads are compared with the extreme...... wind shear load case of the IEC standards, it is seen that they are of similar magnitude and in one case even higher....

  1. Damping Wind and Wave Loads on a Floating Wind Turbine

    DEFF Research Database (Denmark)

    Christiansen, Søren; Bak, Thomas; Knudsen, Torben

    2013-01-01

    Offshore wind energy capitalizes on the higher and less turbulent wind speeds at sea. To enable deployment of wind turbines in deep-water locations, structures are being explored, where wind turbines are placed on a floating platform. This combined structure presents a new control problem, due...... to the partly unconstrained movement of the platform and ocean wave excitation. If this additional complexity is not dealt with properly, this may lead to a significant increase in the structural loads and, potentially, instability of the controlled system. In this paper, the wave excitation is investigated......, and we show the influence that both wind speed, wave frequencies and misalignment between wind and waves have on the system dynamics. A new control model is derived that extends standard turbine models to include the hydrodynamics, additional platform degrees of freedom, the platform mooring system...

  2. Load attenuating passively adaptive wind turbine blade

    Science.gov (United States)

    Veers, Paul S.; Lobitz, Donald W.

    2003-01-07

    A method and apparatus for improving wind turbine performance by alleviating loads and controlling the rotor. The invention employs the use of a passively adaptive blade that senses the wind velocity or rotational speed, and accordingly modifies its aerodynamic configuration. The invention exploits the load mitigation prospects of a blade that twists toward feather as it bends. The invention includes passively adaptive wind turbine rotors or blades with currently preferred power control features. The apparatus is a composite fiber horizontal axis wind-turbine blade, in which a substantial majority of fibers in the blade skin are inclined at angles of between 15 and 30 degrees to the axis of the blade, to produces passive adaptive aeroelastic tailoring (bend-twist coupling) to alleviate loading without unduly jeopardizing performance.

  3. Database on wind characteristics - Analyses of wind turbine design loads

    Energy Technology Data Exchange (ETDEWEB)

    Larsen, G.C.; Hansen, K.S.

    2004-06-01

    The main objective of IEA R and D Wind Annex XVII - Database on Wind Characteristics - has been to provide wind energy planners, designers and researchers, as well as the international wind engineering community in general, with a source of actual wind field data (time series and resource data) observed in a wide range of different wind climates and terrain types. Connected to an extension of the initial Annex period, the scope for the continuation was widened to include also support to the international wind turbine standardisation efforts.. The project partners are Sweden, Norway, U.S.A., The Netherlands and Denmark, with Denmark as the Operating Agent. The reporting of the continuation of Annex XVII falls in two separate parts. Part one accounts in details for the available data in the established database bank, and part two describes various data analyses performed with the overall purpose of improving the design load cases with relevance for to wind turbine structures. The present report constitutes the second part of the Annex XVII reporting. Both fatigue and extreme load aspects are dealt with, however, with the main emphasis on the latter. The work has been supported by The Ministry of Environment and Energy, Danish Energy Agency, The Netherlands Agency for Energy and the Environment (NOVEM), The Norwegian Water Resources and Energy Administration (NVE), The Swedish National Energy Administration (STEM) and The Government of the United States of America. (au)

  4. Wind Loads on Ships and Offshore Structures Estimated by CFD

    DEFF Research Database (Denmark)

    Aage, Christian; Hvid, S.L.; Hughes, P.H.

    1997-01-01

    Wind loads on ships and offshore structures could until recently be determined only by model tests, or by statistical methods based on model tests. By the development of Computational Fluid Dynamics or CFD there is now a realistic computational alternative available. In this paper, wind loads...... on a seagoing ferry and on a semisubmersible offshore platform have been estimated by CFD. The results have been compared with wind tunnel model tests and, for the ferry, a few full-scale measurements, and good agreement is obtained. The CFD method offers the possibility of a computational estimate of scale...... effects related to wind tunnel model testing. An example of such an estimate on the ferry is discussed. Due to the time involved in generating the computational mesh and in computing the solution, the CFD method is not at the moment economically competitive to routine wind tunnel model testing....

  5. Active load control techniques for wind turbines.

    Energy Technology Data Exchange (ETDEWEB)

    van Dam, C.P. (University of California, Davis, CA); Berg, Dale E.; Johnson, Scott J. (University of California, Davis, CA)

    2008-07-01

    This report provides an overview on the current state of wind turbine control and introduces a number of active techniques that could be potentially used for control of wind turbine blades. The focus is on research regarding active flow control (AFC) as it applies to wind turbine performance and loads. The techniques and concepts described here are often described as 'smart structures' or 'smart rotor control'. This field is rapidly growing and there are numerous concepts currently being investigated around the world; some concepts already are focused on the wind energy industry and others are intended for use in other fields, but have the potential for wind turbine control. An AFC system can be broken into three categories: controls and sensors, actuators and devices, and the flow phenomena. This report focuses on the research involved with the actuators and devices and the generated flow phenomena caused by each device.

  6. Wind effects on long-span bridges: Probabilistic wind data format for buffeting and VIV load assessments

    Science.gov (United States)

    Hoffmann, K.; Srouji, R. G.; Hansen, S. O.

    2017-12-01

    The technology development within the structural design of long-span bridges in Norwegian fjords has created a need for reformulating the calculation format and the physical quantities used to describe the properties of wind and the associated wind-induced effects on bridge decks. Parts of a new probabilistic format describing the incoming, undisturbed wind is presented. It is expected that a fixed probabilistic format will facilitate a more physically consistent and precise description of the wind conditions, which in turn increase the accuracy and considerably reduce uncertainties in wind load assessments. Because the format is probabilistic, a quantification of the level of safety and uncertainty in predicted wind loads is readily accessible. A simple buffeting response calculation demonstrates the use of probabilistic wind data in the assessment of wind loads and responses. Furthermore, vortex-induced fatigue damage is discussed in relation to probabilistic wind turbulence data and response measurements from wind tunnel tests.

  7. Behaviour of glass plates under wind loads

    Science.gov (United States)

    Gavanski, Eri

    Glazing damage during strong windstorms has been considered to result mainly from windborne debris. However, recent windstorm damage reports have revealed the necessity of studying fluctuating wind loads, which appear to be another factor contributing to this damage. From an experimental point of view, studies on this topic have been limited to the application of rather simple loading patterns. Moreover, there is an uncertainty surrounding both load resistance and design load used in the current North American window glass design codes. It is of concern that these regulations may not offer sufficient accuracy on account of the limited understanding of time-dependent glass strength derived from the technology available at the time of codification. Unprecedented full-scale glass breakage tests under realistic wind pressure loading were conducted to investigate these issues. The obtained results revealed significant new information about the behavior of glass plates under fluctuating loads. Along with these tests, a numerical simulation using the Monte-Carlo technique was also performed with a subtle modification of the initial glass strength. This adjustment resulted in better correspondence with test results. Using the test and numerical simulation results, the current window glass design method was examined. The calculation methods of LR, and the reference time conversion used in the codes, were found to require further investigation. By creating a particular wind pressure time history, the practice of using peak pressures from ASCE7-05 as the design load was investigated. The results showed that there are cases when the current practice may underestimate the design load because of the duration of windstorms. KEYWORDS: Glass, Fluctuating load, Full-scale test, Load resistance, Design load, Static fatigue, Numerical simulation, Monte-Carlo technique, Brown's integral.

  8. Development of Aeroservoelastic Analytical Models and Gust Load Alleviation Control Laws of a SensorCraft Wind-Tunnel Model Using Measured Data

    Science.gov (United States)

    Silva, Walter A.; Vartio, Eric; Shimko, Anthony; Kvaternik, Raymond G.; Eure, Kenneth W.; Scott,Robert C.

    2007-01-01

    Aeroservoelastic (ASE) analytical models of a SensorCraft wind-tunnel model are generated using measured data. The data was acquired during the ASE wind-tunnel test of the HiLDA (High Lift-to-Drag Active) Wing model, tested in the NASA Langley Transonic Dynamics Tunnel (TDT) in late 2004. Two time-domain system identification techniques are applied to the development of the ASE analytical models: impulse response (IR) method and the Generalized Predictive Control (GPC) method. Using measured control surface inputs (frequency sweeps) and associated sensor responses, the IR method is used to extract corresponding input/output impulse response pairs. These impulse responses are then transformed into state-space models for use in ASE analyses. Similarly, the GPC method transforms measured random control surface inputs and associated sensor responses into an AutoRegressive with eXogenous input (ARX) model. The ARX model is then used to develop the gust load alleviation (GLA) control law. For the IR method, comparison of measured with simulated responses are presented to investigate the accuracy of the ASE analytical models developed. For the GPC method, comparison of simulated open-loop and closed-loop (GLA) time histories are presented.

  9. Atmospheric stability and its influence on wind turbine loads

    DEFF Research Database (Denmark)

    Sathe, Ameya; Mann, Jakob; Barlas, Thanasis K.

    2012-01-01

    Simulations of wind turbine loads for the NREL 5 MW reference wind turbine under diabatic wind conditions are performed for mean wind speeds between 3 { 16 m/s at the turbine hub height. The loads are quantified as the cumulative sum of the damage equivalent load for different wind speeds...... that are weighted according to the wind speed and stability distribution. It is observed that atmospheric stability influences the tower and rotor loads. The difference in the calculated tower loads using diabatic wind conditions and those obtained assuming neutral conditions only is approximately 16%, whereas...... the difference for the rotor loads is up to 11%. The blade loads are hardly influenced by atmospheric stability, where the difference between the calculated loads using diabatic and neutral input wind conditions is less than 1%. The wind profiles and turbulence under diabatic conditions have contrasting...

  10. Wind turbine blade testing under combined loading

    DEFF Research Database (Denmark)

    Roczek-Sieradzan, Agnieszka; Nielsen, Magda; Branner, Kim

    2011-01-01

    The paper presents full-scale blade tests under a combined flap- and edgewise loading. The main aim of this paper is to present the results from testing a wind turbine blade under such conditions and to study the structural behavior of the blade subjected to combined loading. A loading method using...... anchor plates was applied, allowing transverse shear distortion. The global and local deformation of the blade as well as the reproducibility of the test was studied and the results from the investigations are presented....

  11. Sensor comparison study for load alleviating wind turbine pitch control

    DEFF Research Database (Denmark)

    Kragh, Knud Abildgaard; Hansen, Morten Hartvig; Henriksen, Lars Christian

    2014-01-01

    of angle of attack and relative velocity at a radial position of the blades, and upstream inflow measurements from a spinner mounted light detection and ranging (LiDAR) sensor that enables preview of the incoming flow field. The results show that for stationary inflow conditions, the three different......As the size of wind turbines increases, the load alleviating capabilities of the turbine controller are becoming increasingly important. Load alleviating control schemes have traditionally been based on feedback from load sensor; however, recent developments of measurement technologies have enabled...... control on the basis of preview measurements of the inflow acquired using, e.g., light detection and ranging. The potential of alleviating load variations that are caused by mean wind speed changes through feed-forward control have been demonstrated through both experiments and simulations in several...

  12. Inverse load calculation procedure for offshore wind turbines and application to a 5-MW wind turbine support structure: Inverse load calculation procedure for offshore wind turbines

    Energy Technology Data Exchange (ETDEWEB)

    Pahn, T. [Pahn Ingenieure, Am Seegraben 17b 03051 Cottbus Germany; Rolfes, R. [Institut f?r Statik und Dynamik, Leibniz Universit?t Hannover, Appelstra?e 9A 30167 Hannover Germany; Jonkman, J. [National Renewable Energy Laboratory, 15013 Denver West Parkway Golden Colorado 80401 USA

    2017-02-20

    A significant number of wind turbines installed today have reached their designed service life of 20 years, and the number will rise continuously. Most of these turbines promise a more economical performance if they operate for more than 20 years. To assess a continued operation, we have to analyze the load-bearing capacity of the support structure with respect to site-specific conditions. Such an analysis requires the comparison of the loads used for the design of the support structure with the actual loads experienced. This publication presents the application of a so-called inverse load calculation to a 5-MW wind turbine support structure. The inverse load calculation determines external loads derived from a mechanical description of the support structure and from measured structural responses. Using numerical simulations with the software fast, we investigated the influence of wind-turbine-specific effects such as the wind turbine control or the dynamic interaction between the loads and the support structure to the presented inverse load calculation procedure. fast is used to study the inverse calculation of simultaneously acting wind and wave loads, which has not been carried out until now. Furthermore, the application of the inverse load calculation procedure to a real 5-MW wind turbine support structure is demonstrated. In terms of this practical application, setting up the mechanical system for the support structure using measurement data is discussed. The paper presents results for defined load cases and assesses the accuracy of the inversely derived dynamic loads for both the simulations and the practical application.

  13. Wind Tunnel Measurements at LM Wind Power

    DEFF Research Database (Denmark)

    Bertagnolio, Franck

    2012-01-01

    The optimization of airfoil profiles specifically designed for wind turbine application was initiated in the late 80’s [67, 68, 30, 15]. The first attempts to reduce airfoil noise for wind turbines made use of airfoil trailing edge serration. Themodification of airfoil shapes targeted at noise...... reduction is more recent. An important effort was produced in this direction within the SIROCCO project. This latter work involved measurements on full size wind turbines and showed that trailing edge serration may proved a viable solution for mitigating wind turbine noise though it has not been implemented...... on commercial wind turbine yet. It should be mentioned here that the attenuation of turbulent inflow noise using wavy leading edge has recently been investigated [55], but this technique has still to be further validated for practical applications. In this paper, it is proposed to optimize an airfoil which...

  14. Wind loads on post-panamax container ship

    DEFF Research Database (Denmark)

    Andersen, Ingrid Marie Vincent

    2013-01-01

    An investigation of the influence of the container configuration on the deck of a 9000+ TEU container ship on wind forces has been carried out through a series of wind tunnel tests with a 1:450 scale model. An analysis of earlier studies was used to select a series of appropriate loading conditions...... are presented as two different types of non-dimensional coefficients. It was apparent, as expected, that the measured forces and moment depend on the container configuration on deck. The test results may provide a general idea of how the magnitude of the wind forces is affected by a given container...

  15. Wind Tunnel Measurements at LM Wind Power

    DEFF Research Database (Denmark)

    Bertagnolio, Franck

    2012-01-01

    This section presents the results obtained during the experimental campaign that was conducted in the wind tunnel at LM Wind Power in Lunderskov from August 16th to 26th, 2010. The goal of this study is to validate the so-called TNO trailing edge noise model through measurements of the boundary...... layer turbulence characteristics and the far-field noise generated by the acoustic scattering of the turbulent boundary layer vorticies as they convect past the trailing edge. This campaign was conducted with a NACA0015 airfoil section that was placed in the wind tunnel section. It is equipped with high...

  16. Convergence of Extreme Loads for Offshore Wind Turbine Support Structures

    OpenAIRE

    Stewart, Gordon; Lackner, Matthew; Arwade, Sanjay R.; Myers, Andrew T.; Hallowell, Spencer

    2015-01-01

    Extreme loads of wind turbines are historically difficult to predict through simulation due to uncertainty in input conditions as well as in the simulation models. In addition, many long time series must be simulated for the statistics of the peak loads to become stationary. Offshore wind turbines require even more simulation due to the addition of stochastic wave loading. Floating offshore wind turbines, the subject of this paper, experience free-body motion as a result of wind and wave load...

  17. Influence of atmospheric stability on wind turbine loads

    DEFF Research Database (Denmark)

    Sathe, Ameya; Mann, Jakob; Barlas, Thanasis K.

    2013-01-01

    at the turbine hub height. The loads are quantified as the cumulative sum of the damage equivalent load for different wind speeds that are weighted according to the wind speed and stability distribution. Four sites with a different wind speed and stability distribution are used for comparison. The turbulence...... turbulent energy. The tower base loads are mainly influenced by diabatic turbulence, whereas the rotor loads are influenced by diabatic wind profiles. The blade loads are influenced by both, diabatic wind profile and turbulence, that leads to nullifying the contrasting influences on the loads...

  18. Load alleviation on wind turbine blades using variable geometry

    DEFF Research Database (Denmark)

    Basualdo, Santiago

    2005-01-01

    ) wind turbines, which mainly operate under this flow condition. The results show evident reductions in the airfoil displacements by using simple control strategies having the airfoil position and its first and second derivatives as input, especially at the system's eigenfrequency. The use of variable...... in loads in real wind turbines. Keywords: Variable Geometry, Wind Turbine, Load Alleviation, Fatigue Load, Trailing Edge Flap....

  19. Wind loads for bar-truss structures

    Science.gov (United States)

    Katow, M. S.

    1981-01-01

    An analysis method developed to calculate the wind loads on the nodes or joints of the truss type support structure of the 64 meter antenna is described. The method uses the CBAR element and GRID coordinate cards of the NASTRAN or IDEAS structural analysis programs as inputs to the computer model of the structure. Cross flow principles and vector analysis are also used in the analysis. The algorithms used are described and probable accuracy of the solution is discussed.

  20. Load alleviation of wind turbines by yaw misalignment

    DEFF Research Database (Denmark)

    Kragh, Knud Abildgaard; Hansen, Morten Hartvig

    2014-01-01

    Vertical wind shear is one of the dominating causes of load variations on the blades of a horizontal axis wind turbine. To alleviate the varying loads, wind turbine control systems have been augmented with sensors and actuators for individual pitch control. However, the loads caused by a vertical...... wind shear can also be affected through yaw misalignment. Recent studies of yaw control have been focused on improving the yaw alignment to increase the power capture at below rated wind speeds. In this study, the potential of alleviating blade load variations induced by the wind shear through yaw...... be applied without power loss for wind speeds above rated wind speed. In deterministic inflow, it is shown that the range of the steady-state blade load variations can be reduced by up to 70%. For turbulent inflows, it is shown that the potential blade fatigue load reductions depend on the turbulence level...

  1. Investigation of UH-60A Rotor Structural Loads from Flight and Wind Tunnel Tests

    Science.gov (United States)

    2016-05-19

    Investigation of UH-60A Rotor Structural Loads From Flight and Wind Tunnel Tests Hyeonsoo Yeo Mark Potsdam US Army Aviation Development Directorate...NFAC) 40- by 80-Foot Wind Tunnel (Ref. 14) provides an- other set of airloads and structural loads measurements. Fig- ure 2 shows the UH-60A rotor ...blades installed on the NFAC Large Rotor Test Apparatus (LRTA) in the wind tunnel test section. One of the objectives of the wind tunnel test was to

  2. Mean and peak wind load reduction on heliostats

    Energy Technology Data Exchange (ETDEWEB)

    Peterka, J.A.; Tan, L.; Bienkiewcz, B.; Cermak, J.E.

    1987-09-01

    This report presents the results of wind-tunnel tests supported through the Solar Energy Research Institute (SERI) by the Office of Solar Thermal Technology of the US Department of Energy as part of the SERI research effort on innovative concentrators. As gravity loads on drive mechanisms are reduced through stretched-membrane technology, the wind-load contribution of the required drive capacity increases in percentage. Reduction of wind loads can provide economy in support structure and heliostat drive. Wind-tunnel tests have been directed at finding methods to reduce wind loads on heliostats. The tests investigated both mean and peak forces, and moments. A significant increase in ability to predict heliostat wind loads and their reduction within a heliostat field was achieved. In addition, a preliminary review of wind loads on parabolic dish collectors was conducted, resulting in a recommended research program for these type collectors. 42 refs., 38 figs., 1 tab.

  3. Blade-Pitch Control for Wind Turbine Load Reductions

    DEFF Research Database (Denmark)

    Lio, Alan Wai Hou

    Large wind turbines are subjected to the harmful loads that arise from the spatially uneven and temporally unsteady oncoming wind. Such loads are the known sources of fatigue damage that reduce the turbine operational lifetime, ultimately increasing the cost of wind energy to the end-users. In re...

  4. Assessment of Wind Parameter Sensitivity on Ultimate and Fatigue Wind Turbine Loads: Preprint

    Energy Technology Data Exchange (ETDEWEB)

    Robertson, Amy N [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Sethuraman, Latha [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Jonkman, Jason [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Quick, Julian [National Renewable Energy Laboratory (NREL), Golden, CO (United States)

    2018-02-13

    Wind turbines are designed using a set of simulations to ascertain the structural loads that the turbine could encounter. While mean hub-height wind speed is considered to vary, other wind parameters such as turbulence spectra, sheer, veer, spatial coherence, and component correlation are fixed or conditional values that, in reality, could have different characteristics at different sites and have a significant effect on the resulting loads. This paper therefore seeks to assess the sensitivity of different wind parameters on the resulting ultimate and fatigue loads on the turbine during normal operational conditions. Eighteen different wind parameters are screened using an Elementary Effects approach with radial points. As expected, the results show a high sensitivity of the loads to the turbulence standard deviation in the primary wind direction, but the sensitivity to wind shear is often much greater. To a lesser extent, other wind parameters that drive loads include the coherence in the primary wind direction and veer.

  5. Assessment of Wind Parameter Sensitivity on Extreme and Fatigue Wind Turbine Loads

    Energy Technology Data Exchange (ETDEWEB)

    Robertson, Amy N [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Sethuraman, Latha [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Jonkman, Jason [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Quick, Julian [National Renewable Energy Laboratory (NREL), Golden, CO (United States)

    2018-01-12

    Wind turbines are designed using a set of simulations to ascertain the structural loads that the turbine could encounter. While mean hub-height wind speed is considered to vary, other wind parameters such as turbulence spectra, sheer, veer, spatial coherence, and component correlation are fixed or conditional values that, in reality, could have different characteristics at different sites and have a significant effect on the resulting loads. This paper therefore seeks to assess the sensitivity of different wind parameters on the resulting ultimate and fatigue loads on the turbine during normal operational conditions. Eighteen different wind parameters are screened using an Elementary Effects approach with radial points. As expected, the results show a high sensitivity of the loads to the turbulence standard deviation in the primary wind direction, but the sensitivity to wind shear is often much greater. To a lesser extent, other wind parameters that drive loads include the coherence in the primary wind direction and veer.

  6. Comparison of computer codes for calculating dynamic loads in wind turbines

    Science.gov (United States)

    Spera, D. A.

    1978-01-01

    The development of computer codes for calculating dynamic loads in horizontal axis wind turbines was examined, and a brief overview of each code was given. The performance of individual codes was compared against two sets of test data measured on a 100 KW Mod-0 wind turbine. All codes are aeroelastic and include loads which are gravitational, inertial and aerodynamic in origin.

  7. Work package 1B.2 under the European Commission: Integrated wind turbine design (UPWIND): Specification of long-term load measurement technique

    Energy Technology Data Exchange (ETDEWEB)

    Schmidt Paulsen, U.; Cutululis, N.; Soerensen, Poul

    2007-02-15

    The present report is the 12 month intermediate report of the UPWIND WP1B2 transmission and conversion. It describes the developed measurement technique for long-term load measurement technique, presents the hardware details, type of sensors and location, data storage and data analysis technique to verify design load assumptions. (au)

  8. Methods and apparatus for reduction of asymmetric rotor loads in wind turbines

    Science.gov (United States)

    Moroz, Emilian Mieczyslaw; Pierce, Kirk Gee

    2006-10-10

    A method for reducing load and providing yaw alignment in a wind turbine includes measuring displacements or moments resulting from asymmetric loads on the wind turbine. These measured displacements or moments are used to determine a pitch for each rotor blade to reduce or counter asymmetric rotor loading and a favorable yaw orientation to reduce pitch activity. Yaw alignment of the wind turbine is adjusted in accordance with the favorable yaw orientation and the pitch of each rotor blade is adjusted in accordance with the determined pitch to reduce or counter asymmetric rotor loading.

  9. Wind models for the NSTS ascent trajectory biasing for wind load alleviation

    Science.gov (United States)

    Smith, O. E.; Adelfang, S. I.; Batts, G. W.

    1990-01-01

    New concepts are presented for aerospace vehicle ascent wind profile biasing. The purpose for wind biasing the ascent trajectory is to provide ascent wind loads relief and thus decrease the probability for launch delays due to wind loads exceeding critical limits. Wind biasing trajectories to the the profile of monthly mean winds have been widely used for this purpose. The wind profile models presented give additional alternatives for wind biased trajectories. They are derived from the properties of the bivariate normal probability function using the available wind statistical parameters for the launch site. The analytical expressions are presented to permit generalizations. Specific examples are given to illustrate the procedures. The wind profile models can be used to establish the ascent trajectory steering commands to guide the vehicle through the first stage. For the National Space Transportation System (NSTS) program these steering commands are called I-loads.

  10. Dynamic Response of Offshore Wind Turbines subjected to Joint Wave and Wind Loads

    DEFF Research Database (Denmark)

    Liu, Weiliang; Chen, Jianbing; Liu, Wenfeng

    2013-01-01

    into consideration. Wind and wave loads are generated by the physical random models. The aerodynamic loads on blades are calculated by the Blade Element Momentum (BEM) theory, and the wave loads are calculated by the linear theory of wave. The dynamic response of the NREL-5MW wind turbine system is carried out...

  11. Wind Measurement LIDAR, Phase I

    Data.gov (United States)

    National Aeronautics and Space Administration — Systems & Processes Engineering Corporation (SPEC) proposes a Wind Measurement LIDAR whose sensor assembly is composed of SPEC Gen IV LIDAR seeker, with 12.8...

  12. Numerical prediction of wind loads on low buildings | Ahmad ...

    African Journals Online (AJOL)

    In the present study, 2-D numerical simulation of wind loads on low-rise buildings has been carried out. The simulation was carried out under FLUENT package environment in which full-scale Reynolds number, boundary layer and turbulence properties have been simulated. Wind loading effect numerically obtained on flat ...

  13. Reliability analysis of wind turbines exposed to dynamic loads

    DEFF Research Database (Denmark)

    Sørensen, John Dalsgaard

    2014-01-01

    Wind turbines are exposed to highly dynamic loads that cause fatigue and extreme load effects which are subject to significant uncertainties. Further, reduction of cost of energy for wind turbines are very important in order to make wind energy competitive compared to other energy sources......, substructure and foundation considering especially fatigue loads. The function of a wind turbine is highly dependent on many electrical and mechanical components as well as a control system also reliability aspects of these components are discussed and it is described how there reliability influences...

  14. Validation of SWAY Wind Turbine Response in FAST, with a Focus on the Influence of Tower Wind Loads: Preprint

    Energy Technology Data Exchange (ETDEWEB)

    Koh, J. H.; Robertson, A.; Jonkman, J.; Driscoll, R.; Yin Kwee Ng, E.

    2015-04-23

    Need to modify simulated system behavior to the measured data, but the tower wind loads improved the comparison for nonoperating conditions. the SWAY system in both turbine operating and nonoperating conditions. Mixed results were observed when comparing the simulated system behavior to the measured data, but the tower wind loads improved the comparison for nonoperating conditions. without the new tower-load capability to examine its influence on the response characteristics of the system. This is important in situations when the turbine is parked in survival conditions. The simulation results were then compared to measured data from the SWAY system in both turbine operating and nonoperating conditions. Mixed results were observed when comparing the simulated system behavior to the measured data, but the tower wind loads improved the comparison for nonoperating conditions.

  15. Methods and apparatus for rotor load control in wind turbines

    Science.gov (United States)

    Moroz, Emilian Mieczyslaw

    2006-08-22

    A wind turbine having a rotor, at least one rotor blade, and a plurality of generators, of which a first generator is configured to provide power to an electric grid and a second generator is configured to provide power to the wind turbine during times of grid loss. The wind turbine is configured to utilize power provided by the second generator to reduce loads on the wind turbine during times of grid loss.

  16. An Optimal Control Scheme to Minimize Loads in Wind Farms

    DEFF Research Database (Denmark)

    Soleimanzadeh, Maryam; Wisniewski, Rafal

    2012-01-01

    This work presents a control algorithm for wind farms that optimizes the power production of the farm and helps to increase the lifetime of wind turbines components. The control algorithm is a centralized approach, and it determines the power reference signals for individual wind turbines...... such that the structural loads of the wind turbines in low frequencies are reduced. The controller is relatively easy to implement on a wind farm, and in here the results of simulating the controller on a small wind farm is presented....

  17. Morphological Response of Eight Quercus Species to Simulated Wind Load.

    Science.gov (United States)

    Wu, Tonggui; Zhang, Peng; Zhang, Lei; Wang, Geoff G; Yu, Mukui

    Leaf shape, including leaf size, leaf dissection index (LDI), and venation distribution, strongly impacts leaf physiology and the forces of momentum exerted on leaves or the canopy under windy conditions. Yet, little has been known about how leaf shape affects the morphological response of trees to wind load. We studied eight Quercus species, with different leaf shapes, to determine the morphological response to simulated wind load. Quercus trees with long elliptical leaves, were significantly affected by wind load (Pwind load, such as bigger leaf thickness, larger stem diameter, allocation to root biomass, and smaller stem height (Pwind can reduce drag and increase the mechanical strength of the tree. Leaf dissection index (LDI), an important index of leaf shape, was correlated with morphological response to wind load (Pwind load.

  18. 3D WindScanner lidar measurements of wind and turbulence around wind turbines, buildings and bridges

    Science.gov (United States)

    Mikkelsen, T.; Sjöholm, M.; Angelou, N.; Mann, J.

    2017-12-01

    WindScanner is a distributed research infrastructure developed at DTU with the participation of a number of European countries. The research infrastructure consists of a mobile technically advanced facility for remote measurement of wind and turbulence in 3D. The WindScanners provide coordinated measurements of the entire wind and turbulence fields, of all three wind components scanned in 3D space. Although primarily developed for research related to on- and offshore wind turbines and wind farms, the facility is also well suited for scanning turbulent wind fields around buildings, bridges, aviation structures and of flow in urban environments. The mobile WindScanner facility enables 3D scanning of wind and turbulence fields in full scale within the atmospheric boundary layer at ranges from 10 meters to 5 (10) kilometers. Measurements of turbulent coherent structures are applied for investigation of flow pattern and dynamical loads from turbines, building structures and bridges and in relation to optimization of the location of, for example, wind farms and suspension bridges. This paper presents our achievements to date and reviews briefly the state-of-the-art of the WindScanner measurement technology with examples of uses for wind engineering applications.

  19. Wind loads on flat plate photovoltaic array fields

    Science.gov (United States)

    Miller, R. D.; Zimmerman, D. K.

    1981-01-01

    The results of an experimental analysis (boundary layer wind tunnel test) of the aerodynamic forces resulting from winds acting on flat plate photovoltaic arrays are presented. Local pressure coefficient distributions and normal force coefficients on the arrays are shown and compared to theoretical results. Parameters that were varied when determining the aerodynamic forces included tilt angle, array separation, ground clearance, protective wind barriers, and the effect of the wind velocity profile. Recommended design wind forces and pressures are presented, which envelop the test results for winds perpendicular to the array's longitudinal axis. This wind direction produces the maximum wind loads on the arrays except at the array edge where oblique winds produce larger edge pressure loads. The arrays located at the outer boundary of an array field have a protective influence on the interior arrays of the field. A significant decrease of the array wind loads were recorded in the wind tunnel test on array panels located behind a fence and/or interior to the array field compared to the arrays on the boundary and unprotected from the wind. The magnitude of this decrease was the same whether caused by a fence or upwind arrays.

  20. Wind/Wave Misalignment in the Loads Analysis of a Floating Offshore Wind Turbine: Preprint

    Energy Technology Data Exchange (ETDEWEB)

    Barj, L.; Stewart, S.; Stewart, G.; Lackner, M.; Jonkman, J.; Robertson, A.

    2014-02-01

    Wind resources far from the shore and in deeper seas have encouraged the offshore wind industry to look into floating platforms. The International Electrotechnical Commission (IEC) is developing a new technical specification for the design of floating offshore wind turbines that extends existing design standards for land-based and fixed-bottom offshore wind turbines. The work summarized in this paper supports the development of best practices and simulation requirements in the loads analysis of floating offshore wind turbines by examining the impact of wind/wave misalignment on the system loads under normal operation. Simulations of the OC3-Hywind floating offshore wind turbine system under a wide range of wind speeds, significant wave heights, peak-spectral periods and wind/wave misalignments have been carried out with the aero-servo-hydro-elastic tool FAST [4]. The extreme and fatigue loads have been calculated for all the simulations. The extreme and fatigue loading as a function of wind/wave misalignment have been represented as load roses and a directional binning sensitivity study has been carried out. This study focused on identifying the number and type of wind/wave misalignment simulations needed to accurately capture the extreme and fatigue loads of the system in all possible metocean conditions considered, and for a down-selected set identified as the generic US East Coast site. For this axisymmetric platform, perpendicular wind and waves play an important role in the support structure and including these cases in the design loads analysis can improve the estimation of extreme and fatigue loads. However, most structural locations see their highest extreme and fatigue loads with aligned wind and waves. These results are specific to the spar type platform, but it is expected that the results presented here will be similar to other floating platforms.

  1. Load flow analysis for variable speed offshore wind farms

    DEFF Research Database (Denmark)

    Chen, Zhe; Zhao, Menghua; Blaabjerg, Frede

    2009-01-01

    A serial AC-DC integrated load flow algorithm for variable speed offshore wind farms is proposed. It divides the electrical system of a wind farm into several local networks, and different load flow methods are used for these local networks sequentially. This method is fast, more accurate, and many...... factors such as the different wind farm configurations, the control of wind turbines and the power losses of pulse width modulation converters are considered. The DC/DC converter model is proposed and integrated into load flow algorithm by modifying the Jacobian matrix. Two iterative methods are proposed...... and integrated into the load flow algorithm: one takes into account the control strategy of converters and the other considers the power losses of converters. In addition, different types of variable speed wind turbine systems with different control methods are investigated. Finally, the method is demonstrated...

  2. Database on wind characteristics - Analyses of wind turbine design loads

    DEFF Research Database (Denmark)

    Larsen, Gunner Chr.; Hansen, K.S.

    2004-01-01

    The main objective of IEA R&D Wind Annex XVII - Database on Wind Characteristics - has been to provide wind energy planners, designers and researchers, as well as the international wind engineering community in general, with a source of actual wind fielddata (time series and resource data) observed...... in a wide range of different wind climates and terrain types. Connected to an extension of the initial Annex period, the scope for the continuation was widened to include also support to the international windturbine standardisation efforts.. The project partners are Sweden, Norway, U.S.A., The Netherlands...... and Denmark, with Denmark as the Operating Agent. The reporting of the continuation of Annex XVII falls in two separate parts. Part one accounts in detailsfor the available data in the established database bank, and part two describes various data analyses performed with the overall purpose of improving...

  3. Wind shear estimation and wake detection by rotor loads — First wind tunnel verification

    Science.gov (United States)

    Schreiber, J.; Cacciola, S.; Campagnolo, F.; Petrović, V.; Mourembles, D.; Bottasso, C. L.

    2016-09-01

    The paper describes a simple method for detecting presence and location of a wake affecting a downstream wind turbine operating in a wind power plant. First, the local wind speed and shear experienced by the wind turbine are estimated by the use of rotor loads and other standard wind turbine response data. Then, a simple wake deficit model is used to determine the lateral position of the wake with respect to the affected rotor. The method is verified in a boundary layer wind tunnel using two instrumented scaled wind turbine models, demonstrating its effectiveness.

  4. Optimized Control Strategy For Over Loaded Offshore Wind Turbines

    DEFF Research Database (Denmark)

    Odgaard, Peter Fogh; Knudsen, Torben; Wisniewski, Rafal

    2015-01-01

    Abstract Optimized control strategy for overloaded offshore wind turbines Introduction Operation and maintenance cost are an important part of cost of energy especially for offshore wind farms. Typically unplanned service is called for due to detection off excessive loads on components, e.......g., the tower. In the process of decreasing the cost of energy of wind turbines it is relevant to continue some level of production while awaiting service and repair of the offshore wind turbine. This is typically done operating the wind turbine in a power de-rated operation mode, assuming that lower power...... generation results in lower loads on the wind turbine, which enables continued production until next service. Approach Recent results in Model Predictive Control (MPC) applied to wind turbines show a potential for presenting possible controller tunings which weighs multiple conflicting objectives...

  5. Monitoring fatigue loads on wind turbines using cycle counting data acquisition systems

    Energy Technology Data Exchange (ETDEWEB)

    Soeker, H.; Seifert, H. [Deutsches Windenergie-Institut (Germany); Fragoulis, A.; Vionis, P.; Foussekis, D. [Center for Renewable Energy Sources (Greece); Dahlberg, J.A.; Poppen, M. [The Aeronautical Research Institue of Sweden (Sweden)

    1996-09-01

    As in any industrial application, the duration of a wind turbine`s life is a key parameter for the evaluation of its economic potential. Assuming a service life of 20 years, components of the turbine have to withstand a number of load cycles of up to 10{sup 8}. Such numbers of load cycles impose high demands on the fatigue characteristics of both, the used materials and the design. Nevertheless, fatigue loading of wind turbine components still remains a parameter of high uncertainty in the design of wind turbines. The specific features of these fatigue loads can be expected to vary with the type of turbine and the site of operation. In order to ensure the reliability of the next generation of larger scale wind turbines improved load assumptions will be of vital importance. Within the scope of the presented research program DEWI, C.R.E.S. and FFA monitored fatigue loads of serial produced wind turbines by means of a monitoring method that uses on-line cycle counting techniques. The blade root bending moments of two pitch controlled, variable speed wind turbines operating in the Hamswehrum wind farm, and also that of a stall controlled, fixed speed wind turbine operating in CRES` complex terrain test site, were measured by DEWI and CRES. In parallel FFA used their database of time series measurements of blade root bending moments on a stall controlled, fixed speed turbine at Alsvik Windfarm in order to derive semi-empirical fatigue load data. The experience gained from application of the on-line measurement technique is discussed with respect to performance, data quality, reliability and cost effectiveness. Investigations on the effects of wind farm and complex terrain operation on the fatigue loads of wind turbine rotor blades are presented. (au)

  6. Aeroelastic Ground Wind Loads Analysis Tool for Launch Vehicles

    Science.gov (United States)

    Ivanco, Thomas G.

    2016-01-01

    Launch vehicles are exposed to ground winds during rollout and on the launch pad that can induce static and dynamic loads. Of particular concern are the dynamic loads caused by vortex shedding from nearly-cylindrical structures. When the frequency of vortex shedding nears that of a lowly-damped structural mode, the dynamic loads can be more than an order of magnitude greater than mean drag loads. Accurately predicting vehicle response to vortex shedding during the design and analysis cycles is difficult and typically exceeds the practical capabilities of modern computational fluid dynamics codes. Therefore, mitigating the ground wind loads risk typically requires wind-tunnel tests of dynamically-scaled models that are time consuming and expensive to conduct. In recent years, NASA has developed a ground wind loads analysis tool for launch vehicles to fill this analytical capability gap in order to provide predictions for prelaunch static and dynamic loads. This paper includes a background of the ground wind loads problem and the current state-of-the-art. It then discusses the history and significance of the analysis tool and the methodology used to develop it. Finally, results of the analysis tool are compared to wind-tunnel and full-scale data of various geometries and Reynolds numbers.

  7. Extreme load predictions for floating offshore wind turbines

    DEFF Research Database (Denmark)

    Jensen, Jørgen Juncher

    2009-01-01

    An effective stochastic procedure for extreme value predictions related to wave and wind induced stochastic loads is applied to a tension-leg concept for floating offshore wind turbines. The method is based on the First Order Reliability Method (FORM) and as the procedure makes use of only short...... time-domain simulations all kinds of non-linearities can be included. The procedure has been used previously for wave induced loads and is in this note extended to combined wave and wind loads....

  8. Modelling of a chaotic load of wind turbines drivetrain

    Science.gov (United States)

    Bielecki, Andrzej; Barszcz, Tomasz; Wójcik, Mateusz

    2015-03-01

    The purpose of this paper is to present a model of the load of the wind turbine gears for simulation of real, varying operational conditions for modelling of wind turbine vibration. The characteristics of the wind, which generates chaotically varying loads on the drivetrain components generating load in teeth and bearings of gears during torque transfer, are discussed. A generator of variable load of wind turbines drivetrain is proposed. Firstly, the module for generation of wind speed is designed. It is based on the approach in which the wind speed was considered as a time series approximated by the Weierstrass function. Secondly, the rotational speed of the main shaft is proposed as a function of the wind speed value. The function depends on a few parameters that are fitted by using a genetic algorithm. Finally, the model of torque of the main shaft is introduced. This model has been created by using a multi-layer artificial neural network. The results show that the proposed approach yields a very good fit for the experimental data. The fit brings about the proper reproducing of all the aspects of the load that are crucial for causing fatigue and, as a consequence, damaging of gears of the wind turbines.

  9. Thermal loading of wind power converter considering dynamics of wind speed

    DEFF Research Database (Denmark)

    Baygildina, Elvira; Peltoniemi, Pasi; Pyrhönen, Olli

    2013-01-01

    ), and the thermal stress of power devices is investigated from the frequency spectrum point of view of wind speed. It is concluded that because of the strong inertia effects by the aerodynamic behavior of wind turbines, thermal stress of the semiconductors is relatively more stable and only influenced by the low......The thermal loading of power semiconductors is a crucial performance related to the reliability and cost of the wind power converter. However, the thermal loading impacts by the variation of wind speeds have not yet been clarified, especially when considering the aerodynamic behavior of the wind...

  10. Offshore wind turbine foundation monitoring, extrapolating fatigue measurements from fleet leaders to the entire wind farm

    Science.gov (United States)

    Weijtens, Wout; Noppe, Nymfa; Verbelen, Tim; Iliopoulos, Alexandros; Devriendt, Christof

    2016-09-01

    The present contribution is part of the ongoing development of a fatigue assessment strategy driven purely on in-situ measurements on operational wind turbines. The primary objective is to estimate the remaining life time of existing wind farms and individual turbines by instrumenting part of the farm with a load monitoring setup. This load monitoring setup allows to measure interface loads and local stress histories. This contribution will briefly discuss how these load measurements can be translated into fatigue assessment of the instrumented turbine. However, due to different conditions at the wind farm, such as turbulence, differences in water depth and foundation design this turbine will not be fully representable for all turbines in the farm. In this paper we will use the load measurements on two offshore wind turbines in the Northwind offshore wind farm to discuss fatigue progression in an operational wind farm. By calculating the damage equivalent loads on the two turbines the fatigue progression is quantified for every 10 minute interval and can be analyzed against turbulence and site conditions. In future work these results will be used to predict the fatigue life progression in the entire farm.

  11. Grid faults' impact on wind turbine structural loads

    DEFF Research Database (Denmark)

    Hansen, Anca Daniela; Cutululis, Nicolaos Antonio; Iov, F.

    2007-01-01

    The objective of this work is to illustrate the impact of the grid faults on the wind turbine structural loads. Grid faults are typically simulated in detailed power system simulation tools, which by applying simplified mechanical models, are not able to provide a throughout insight...... on the structural loads caused by sudden disturbances on the grid. On the other hand, structural loads of the wind turbine are typically assessed in advanced aerolastic computer codes, which by applying simplified electrical models do not provide detailed electrical insight. This paper presents a simulation...... of the wind turbine during grid faults. The effect of a grid fault on the wind turbine flexible structure is assessed for a typical fixed speed wind turbine, equipped with an induction generator....

  12. Optimized Control Strategy For Over Loaded Offshore Wind Turbines

    DEFF Research Database (Denmark)

    Odgaard, Peter Fogh; Knudsen, Torben; Wisniewski, Rafal

    2015-01-01

    .g., the tower. In the process of decreasing the cost of energy of wind turbines it is relevant to continue some level of production while awaiting service and repair of the offshore wind turbine. This is typically done operating the wind turbine in a power de-rated operation mode, assuming that lower power...... controller tuning for a given wind turbine. It also enables a very safe and robust comparison between a new control strategy and the present one. Main body of abstract Is it true that power de-rating indeed the best way to reduce loads? The power de-rating approach has the drawback of only indirectly...... and service at offshore location, where accessibility can be problematic. The controller objectives are focused directly on the actual objective like lowering of fore aft fatigue loads, instead of using an indirect objective of de-rating the power production of the wind turbine. This means what the wind...

  13. Adaptive pitch control for load mitigation of wind turbines

    Science.gov (United States)

    Yuan, Yuan; Tang, J.

    2015-04-01

    In this research, model reference adaptive control is examined for the pitch control of wind turbines that may suffer from reduced life owing to extreme loads and fatigue when operated under a high wind speed. Specifically, we aim at making a trade-off between the maximum energy captured and the load induced. The adaptive controller is designed to track the optimal generator speed and at the same time to mitigate component loads under turbulent wind field and other uncertainties. The proposed algorithm is tested on the NREL offshore 5-MW baseline wind turbine, and its performance is compared with that those of the gain scheduled proportional integral (GSPI) control and the disturbance accommodating control (DAC). The results show that the blade root flapwise load can be reduced at a slight expense of optimal power output. The generator speed regulation under adaptive controller is better than DAC.

  14. Loads on Wind Turbines Access Platforms with Gratings

    DEFF Research Database (Denmark)

    Andersen, Thomas Lykke; Frigaard, Peter; Rasmussen, Michael R.

    2011-01-01

    The present paper deals with loads on wind turbine access platforms. The many planned new wind turbine parks together with the observed damages on platforms in several existing parks make the topic very important. The paper gives an overview of recently developed design formulae for different types...

  15. Load calculation methods for offshore wind turbine foundations

    DEFF Research Database (Denmark)

    Passon, Patrik; Branner, Kim

    2014-01-01

    Calculation of design loads for offshore wind turbine (OWT) foundations is typically performed in a joint effort between wind turbine manufactures and foundation designers (FDs). Ideally, both parties would apply the same fully integrated design tool and model for that purpose. However, such solu...

  16. Operation and Equivalent Loads of Wind Turbines in Large Wind Farms

    Science.gov (United States)

    Andersen, Soren Juhl; Sorensen, Jens Norkaer; Mikkelsen, Robert Flemming

    2017-11-01

    Wind farms continue to grow in size and as the technology matures, the design of wind farms move towards including dynamic effects besides merely annual power production estimates. The unsteady operation of wind turbines in large wind farms has been modelled with EllipSys3D(Michelsen, 1992, and Sørensen, 1995) for a number of different scenarios using a fully coupled large eddy simulations(LES) and aero-elastic framework. The turbines are represented in the flow fields using the actuator line method(Sørensen and Shen, 2002), where the aerodynamic forces and deflections are derived from an aero-elastic code, Flex5(Øye, 1996). The simulations constitute a database of full turbine operation in terms of both production and loads for various wind speeds, turbulence intensities, and turbine spacings. The operating conditions are examined in terms of averaged power production and thrust force, as well as 10min equivalent flapwise bending, yaw, and tilt moment loads. The analyses focus on how the performance and loads change throughout a given farm as well as comparing how various input parameters affect the operation and loads of the wind turbines during different scenarios. COMWIND(Grant 2104-09- 067216/DSF), Nordic Consortium on Optimization and Control of Wind Farms, Eurotech Greentech Wind project, Winds2Loads, and CCA LES. Ressources Granted on SNIC and JESS. The Vestas NM80 turbine has been used.

  17. Wind simulation for extreme and fatigue loads

    Energy Technology Data Exchange (ETDEWEB)

    Nielsen, M.; Larsen, G.C.; Mann, J.; Ott, S.; Hansen, K.S.; Pedersen, B.J.

    2004-01-01

    Measurements of atmospheric turbulence have been studied and found to deviate from a Gaussian process, in particular regarding the velocity increments over small time steps, where the tails of the pdf are exponential rather than Gaussian. Principles for extreme event counting and the occurrence of cascading events are presented. Empirical extreme statistics agree with Rices exceedence theory, when it is assumed that the velocity and its time derivative are independent. Prediction based on the assumption that the velocity is a Gaussian process underpredicts the rate of occurrence of extreme events by many orders of magnitude, mainly because the measured pdf is non-Gaussian. Methods for simulation of turbulent signals have been developed and their computational efficiency are considered. The methods are applicable for multiple processes with individual spectra and probability distributions. Non-Gaussian processes are simulated by the correlation-distortion method. Non-stationary processes are obtained by Bezier interpolation between a set of stationary simulations with identical random seeds. Simulation of systems with some signals available is enabled by conditional statistics. A versatile method for simulation of extreme events has been developed. This will generate gusts, velocity jumps, extreme velocity shears, and sudden changes of wind direction. Gusts may be prescribed with a specified ensemble average shape, and it is possible to detect the critical gust shape for a given construction. The problem is formulated as the variational problem of finding the most probable adjustment of a standard simulation of a stationary Gaussian process subject to relevant event conditions, which are formulated as linear combination of points in the realization. The method is generalized for multiple correlated series, multiple simultaneous conditions, and 3D fields of all velocity components. Generalization are presented for a single non-Gaussian process subject to relatively

  18. Ascent structural wind loads for the National Space Transportation System (NSTS)

    Science.gov (United States)

    Smith, O. E.; Adelfang, S. I.; Brown, R. P.

    1988-01-01

    An aerospace vehicle must withstand the design ascent structural load or be within any flight constraint to safely reach orbit. For the NSTS an assessment for flight readiness is made for each mission. This assessment for ascent loads and performance parameters is stated in terms of launch probability derived from samples of Jimsphere wind profiles. For the day of launch operations an allowance is made for the ascent load variability due to the wind profile variability over a 3.5-hour period. This is the current time period required to obtain a Jimsphere measurement and perform a complete load simulation prior to launch time. The load variability is derived from a sample of 3.5-hour Jimsphere wind profile pairs. It is applied as a conditional percentile value given the wind load at 3.5 hours prior to launch time. Probability models are used for these analyses. Application of the univariate, bivariate and conditional forms of the extreme value (Gumbel) probability distribution to the analysis of extreme wind speeds, wind shears and vehicle loads is described.

  19. Simulation of probabilistic wind loads and building analysis

    Science.gov (United States)

    Shah, Ashwin R.; Chamis, Christos C.

    1991-01-01

    Probabilistic wind loads likely to occur on a structure during its design life are predicted. Described here is a suitable multifactor interactive equation (MFIE) model and its use in the Composite Load Spectra (CLS) computer program to simulate the wind pressure cumulative distribution functions on four sides of a building. The simulated probabilistic wind pressure load was applied to a building frame, and cumulative distribution functions of sway displacements and reliability against overturning were obtained using NESSUS (Numerical Evaluation of Stochastic Structure Under Stress), a stochastic finite element computer code. The geometry of the building and the properties of building members were also considered as random in the NESSUS analysis. The uncertainties of wind pressure, building geometry, and member section property were qualified in terms of their respective sensitivities on the structural response.

  20. A review of the wind loading zones for flat roofs in code provisions

    NARCIS (Netherlands)

    Geurts, C.P.W.; Kopp, G.A.; Morrison, M.J.

    2013-01-01

    The provisions for wind loads on flat roofs differ considerably between current wind loading standards in different jurisdictions. For a number of major wind loading codes, both the definition of roof zones, and the values applied to determine the wind loads are discussed. This paper concentrates on

  1. Can Wind Lidars Measure Turbulence?

    DEFF Research Database (Denmark)

    Sathe, Ameya; Mann, Jakob; Gottschall, Julia

    2011-01-01

    and conical scanning. The predictions are compared with the measurements from the ZephIR, WindCube, and sonic anemometers at a flat terrain test site under different atmospheric stability conditions. The sonic measurements are used at several heights on a meteorological mast in combination with lidars...... errors also vary with atmospheric stability and are low for unstable conditions. In general, for both lidars, the model agrees well with the measurements at all heights and under different atmospheric stability conditions. For the ZephIR, the model results are improved when an additional low-pass filter...

  2. Model-Based Load Estimation for Predictive Condition Monitoring of Wind Turbines

    DEFF Research Database (Denmark)

    Perisic, Nevena; Pederen, Bo Juul; Grunnet, Jacob Deleuran

    The main objective of this paper is to present a Load Observer Tool (LOT) for condition monitoring of structural extreme and fatigue loads on the main wind turbine (WTG) components. LOT uses well-known methods from system identification, state estimation and fatigue analysis in a novel approach...... for application in condition monitoring. Fatigue loads are estimated online using a load observer and grey box models which include relevant WTG dynamics. Identification of model parameters and calibration of observer are performed offline using measurements from WTG prototype. Signal processing of estimated load...... signal is performed online, and a Load Indicator Signal (LIS) is formulated as a ratio between current estimated accumulated fatigue loads and its expected value based only on a priori knowledge (WTG dynamics and wind climate). LOT initialisation is based on a priori knowledge and can be obtained using...

  3. Work Package 1B.2 under the European Commission, Integrated Wind Turbine Design (UPWIND): Verification of long-term load measurement technique

    Energy Technology Data Exchange (ETDEWEB)

    Schmidt Paulsen, U.

    2011-02-15

    The present report is the final effort of tasks carried out under UPWIND WP1B2 transmission and conversion, which describes: 1) results and recommendations developed in the course of developing the long-term load measurement technique. 2) the hardware details, type of sensors and location, data storage and. 3) data analysis technique to verify design load assumptions. The work is carried out under Contract no 019945 (SES6) 'UPWIND' within the European Commission The interaction between the mechanical and electrical generator subsystems is described rudimentarily, based primarily on HAWC2 simulations below stall of the mechanical system with simple generator and gearbox systems. The electrical system simulations were not carried out as intended in DOW[2], but indications of the conditions for establishing the interaction have been described by measurements and by argument, that this might have an effect as indicated. The hypothesis stating, that the power signal can be utilized as a basic signal for extended analysis of mechanical as well as electrical power signal with static and dynamic features, has been demonstrated on performance and dynamic bandwidth capability. It is however from present analysis obvious that improved signal conditions could be achieved with other mechanical joint solutions than with the present torque signal as measured with the cardan joint. For the reasons mentioned, the comparison with a signal showing the mechanical properties could be improved, with a likely gain on the accuracy as a result. (Author)

  4. Design of a wind tunnel scale model of an adaptive wind turbine blade for active aerodynamic load control experiments

    NARCIS (Netherlands)

    Hulskamp, A.W.; Beukers, A.; Bersee, H.E.N.; Van Wingerden, J.W.; Barlas, T.

    2007-01-01

    Within wind energy research there is a drive towards the development of a “smart rotor”; a rotor of which the loading can be measured and controlled through the application of a sensor system, a control system and an aerodynamic device. Most promising solutions from an aerodynamic point of view are

  5. Load Reduction of Wind Turbines Using Receding Horizon Control

    DEFF Research Database (Denmark)

    Soltani, Mohsen; Wisniewski, Rafal; Brath, Per

    2011-01-01

    Large scale wind turbines are lightly damped mechanical structures driven by wind that is constantly fluctuating. In this paper, we address the design of a model-based receding horizon control scheme to reduce the structural loads in the transmission system and the tower, as well as provide...... constant (or at least smooth) power generation. Our controller incorporates two optimization problems: one to predict or estimate mean wind speed, given LIDAR data, and the other to carry out receding horizon control to choose the control inputs. The method is verified against an existing wind turbine...... control system, and shows reductions in both extreme loads and power fluctuations by 80% and 90% respectively when compared to a conventional controller....

  6. Wind Turbine Controller to Mitigate Structural Loads on a Floating Wind Turbine Platform

    Energy Technology Data Exchange (ETDEWEB)

    Fleming, Paul A.; Peiffer, Antoine; Schlipf, David

    2016-06-24

    This paper summarizes the control design work that was performed to optimize the controller of a wind turbine on the WindFloat structure. The WindFloat is a semi-submersible floating platform designed to be a support structure for a multi-megawatt power-generating wind turbine. A controller developed for a bottom-fixed wind turbine configuration was modified for use when the turbine is mounted on the WindFloat platform. This results in an efficient platform heel resonance mitigation scheme. In addition several control modules, designed with a coupled linear model, were added to the fixed-bottom baseline controller. The approach was tested in a fully coupled nonlinear aero-hydroelastic simulation tool in which wind and wave disturbances were modeled. This testing yielded significant improvements in platform global performance and tower-base-bending loading.

  7. Impact of uncertainty in airfoil characteristics on wind turbine extreme loads

    DEFF Research Database (Denmark)

    Abdallah, Imad; Natarajan, Anand; Sørensen, John Dalsgaard

    2015-01-01

    Wind tunnel test measurements to characterize the static lift and drag coefficients of airfoils used in wind turbine blades are shown to possess large uncertainties, which leads to uncertainties in the aerodynamic loads on the rotor. In this paper a rational stochastic model is proposed to quantify...... the uncertainty in airfoil static lift and drag coefficients based on field and wind tunnel data, aero-servoelastic calculations and engineering judgment. The stochastic model is subsequently used to assess the effect of the uncertainty in airfoil static lift and drag coefficients on the prediction of extreme...... loads and structural reliability of large wind turbines. It is shown that the uncertainty in the static airfoil data has a significant impact on the prediction of extreme loads effects and structural reliability depending on the component, operating conditions (stand-still versus power production...

  8. Multivariate Modelling of Extreme Load Combinations for Wind Turbines

    DEFF Research Database (Denmark)

    Dimitrov, Nikolay Krasimirov

    2015-01-01

    We demonstrate a model for estimating the joint probability distribution of two load components acting on a wind turbine blade cross section. The model addresses the problem of modelling the probability distribution of load time histories with large periodic components by dividing the signal...... into a periodic part and a perturbation term, where each part has a known probability distribution. The proposed model shows good agreement with simulated data under stationary conditions, and a design load envelope based on this model is comparable to the load envelope estimated using the standard procedure...... for determining contemporaneous loads. By defining a joint probability distribution and full return-period contours for multiple load components, the suggested procedure gives the possibility for determining the most critical loading direction in a blade cross section, or for carrying out reliability analysis...

  9. Small-Signal Stability of Wind Power System With Full-Load Converter Interfaced Wind Turbines

    DEFF Research Database (Denmark)

    Knüppel, Thyge; Nielsen, Jørgen Nygaard; Jensen, Kim Høj

    2012-01-01

    Small-signal stability analysis of power system oscillations is a well established field within power system analysis, but not much attention has yet been paid to systems with a high penetration of wind turbines and with large wind power plants (WPP). In this paper a comprehensive analysis...... is presented which assesses the impact of full-load converter interfaced wind turbines on power system small-signal stability. The study is based on a 7 generator network with lightly damped inter-area modes. A detailed wind turbine (WT) model with all grid relevant control functions is used in the study...

  10. Wind profiles for Space Shuttle loads analysis

    Science.gov (United States)

    Adelfang, S. I.

    1978-01-01

    The small scale wind velocity perturbations in vertical wind profiles at Cape Kennedy, Florida were analyzed in order to derive information for simulations of space shuttle ascent through the perturbed atmosphere. The available statistical data does not permit specification of various aspects of idealized singularities and wavelike perturbations with a reasonable degree of confidence. The information developed as a result of the analysis described in Section 3 of this report is suitable for the further development of idealized models. The term perturbation is used instead of the more common term, gust. According to the conventional approach, a gust profile is calculated by applying a high pass digital filter to a Jimsphere profile; all the speeds in the filtered profile are defined as gusts. The high pass filtered profile is defined as a residual profile and the maximum residual in the vicinity of a specified reference height is defined as the gust. Gusts defined in this manner represent the perturbation peaks. A detailed discussion of the calculation of residual profiles and gusts is given. The meteorological coordinate system, the data sample, and Jimsphere profiles are also described. Recommendations and conclusions are presented.

  11. Model of analysis of maximum loads in wind generators produced by extreme winds

    International Nuclear Information System (INIS)

    Herrera – Sánchez, Omar; Schellong, Wolfgang; González – Fernández, Vladimir

    2010-01-01

    The use of the wind energy by means of the wind turbines in areas of high risk of occurrence of Hurricanes comes being an important challenge for the designers of wind farm at world for some years. The wind generator is not usually designed to support this type of phenomena, for this reason the areas of high incidence of tropical hurricanes of the planning are excluded, that which, in occasions disables the use of this renewable source of energy totally, either because the country is very small, or because it coincides the area of more potential fully with that of high risk. To counteract this situation, a model of analysis of maxims loads has been elaborated taken place the extreme winds in wind turbines of great behavior. This model has the advantage of determining, in a chosen place, for the installation of a wind farm, the micro-areas with higher risk of wind loads above the acceptable for the standard classes of wind turbines. (author)

  12. Wind Load Test of Earthbag Wall

    Directory of Open Access Journals (Sweden)

    Ryan Scott

    2013-08-01

    Full Text Available Earthbag construction is a sustainable, low-cost, housing option for developing countries. Earthbag structures are built of individual soil-filled fabric bags (i.e., sand bags stacked in a running bond pattern. Once stacked, earthbags are compacted and the soil inside the bags is dried in-place to form earthen bricks. Barbed wires are placed between each course to affect shear transfer within the wall. Results of an out-of-plane load test on a full-scale earthbag wall are presented in this paper. The wall was subjected to out-of-plane pressure up to 3.16 kPa, which resulted in plastic deformations up to 50 mm. The wall did not collapse during loading. Wall behavior and force transfer mechanisms are discussed.

  13. Wind Speed Preview Measurement and Estimation for Feedforward Control of Wind Turbines

    Science.gov (United States)

    Simley, Eric J.

    Wind turbines typically rely on feedback controllers to maximize power capture in below-rated conditions and regulate rotor speed during above-rated operation. However, measurements of the approaching wind provided by Light Detection and Ranging (lidar) can be used as part of a preview-based, or feedforward, control system in order to improve rotor speed regulation and reduce structural loads. But the effectiveness of preview-based control depends on how accurately lidar can measure the wind that will interact with the turbine. In this thesis, lidar measurement error is determined using a statistical frequency-domain wind field model including wind evolution, or the change in turbulent wind speeds between the time they are measured and when they reach the turbine. Parameters of the National Renewable Energy Laboratory (NREL) 5-MW reference turbine model are used to determine measurement error for a hub-mounted circularly-scanning lidar scenario, based on commercially-available technology, designed to estimate rotor effective uniform and shear wind speed components. By combining the wind field model, lidar model, and turbine parameters, the optimal lidar scan radius and preview distance that yield the minimum mean square measurement error, as well as the resulting minimum achievable error, are found for a variety of wind conditions. With optimized scan scenarios, it is found that relatively low measurement error can be achieved, but the attainable measurement error largely depends on the wind conditions. In addition, the impact of the induction zone, the region upstream of the turbine where the approaching wind speeds are reduced, as well as turbine yaw error on measurement quality is analyzed. In order to minimize the mean square measurement error, an optimal measurement prefilter is employed, which depends on statistics of the correlation between the preview measurements and the wind that interacts with the turbine. However, because the wind speeds encountered by

  14. High resolution climatological wind measurements for wind energy applications

    Energy Technology Data Exchange (ETDEWEB)

    Bergstroem, H. [Uppsala Univ. (Sweden). Dept. of Meteorology

    1996-12-01

    Measurements with a combined cup anemometer/wind vane instrument, developed at the Department of Meteorology in Uppsala, is presented. The instrument has a frequency response of about 1 Hz, making it suitable not only for mean wind measurements, but also for studies of atmospheric turbulence. It is robust enough to be used for climatological purposes. Comparisons with data from a hot-film anemometer show good agreement, both as regards standard deviations and the spectral decomposition of the turbulent wind signal. The cup anemometer/wind vane instrument is currently used at three sites within the Swedish wind energy research programme. These measurements are shortly described, and a few examples of the results are given. 1 ref, 10 figs

  15. Validation of Sodar Measurements for Wind Power

    DEFF Research Database (Denmark)

    Hansen, Kurt Schaldemose

    2006-01-01

    A ground-based SODAR has been tested for 1½ years together with a traditional measurement set-up consisting of cups and vanes for measuring wind data for wind power assessment at a remote location. Many problems associated to the operation of a remote located SODAR have been solved during...... the project and a new remote power system has been designed. A direct comparison between SODAR and cup measurements revealed a limitation for the SODAR measurements during different weather conditions, especially since the SODAR was not able to measure wind speeds above 15 m/s due to an increasing back......-ground noise. Instead, using the SODAR as a profiler to establish representative wind speed profiles was successful. These wind speed profiles are combined with low height reference measurements to establish reliable hub height wind speed distributions. Representative wind speed profiles can be establish...

  16. Using wind speed from a blade-mounted flow sensor for power and load assessment on modern wind turbines

    Directory of Open Access Journals (Sweden)

    M. M. Pedersen

    2017-11-01

    Full Text Available In this paper an alternative method to evaluate power performance and loads on wind turbines using a blade-mounted flow sensor is investigated. The hypothesis is that the wind speed measured at the blades has a high correlation with the power and loads such that a power or load assessment can be performed from a few hours or days of measurements.In the present study a blade-mounted five-hole pitot tube is used as the flow sensor as an alternative to the conventional approach, where the reference wind speed is either measured at a nearby met mast or on the nacelle using lidar technology or cup anemometers. From the flow sensor measurements, an accurate estimate of the wind speed at the rotor plane can be obtained. This wind speed is disturbed by the presence of the wind turbine, and it is therefore different from the free-flow wind speed. However, the recorded wind speed has a high correlation with the actual power production as well as the flap-wise loads as it is measured close to the blade where the aerodynamic forces are acting.Conventional power curves are based on at least 180 h of 10 min mean values, but using the blade-mounted flow sensor both the observation average time and the overall assessment time can potentially be shortened. The basis for this hypothesis is that the sensor is able to provide more observations with higher accuracy, as the sensor follows the rotation of the rotor and because of the high correlation between the flow at the blades and the power production. This is the research question addressed in this paper.The method is first tested using aeroelastic simulations where the dependence of the radial position and effect of multiple blade-mounted flow sensors are also investigated. Next the method is evaluated on the basis of full-scale measurements on a pitch-regulated, variable-speed 3.6 MW wind turbine.It is concluded that the wind speed derived from the blade-mounted flow sensor is highly correlated with the

  17. H∞ Based Control for Load Mitigation in Wind Turbines

    Directory of Open Access Journals (Sweden)

    Aron Pujana-Arrese

    2012-04-01

    Full Text Available This article demonstrates a strategy to design multivariable and multi-objective controllers based on the H∞ norm reduction applied to a wind turbine. The wind turbine model has been developed in the GH Bladed software and it is based on a 5 MW wind turbine defined in the Upwind European project. The designed control strategy works in the above rated power production zone and performs generator speed control and load reduction on the drive train and tower. In order to do this, two robust H∞ MISO (Multi-Input Single-Output controllers have been developed. These controllers generate collective pitch angle and generator torque set-point values to achieve the imposed control objectives. Linear models obtained in GH Bladed 4.0 are used, but the control design methodology can be used with linear models obtained from any other modelling package. Controllers are designed by setting out a mixed sensitivity problem, where some notch filters are also included in the controller dynamics. The obtained H∞ controllers have been validated in GH Bladed and an exhaustive analysis has been carried out to calculate fatigue load reduction on wind turbine components, as well as to analyze load mitigation in some extreme cases. The analysis compares the proposed control strategy based on H∞ controllers to a baseline control strategy designed using the classical control methods implemented on the present wind turbines.

  18. Reducing Turbine Mechanical Loads Using Flow Model-Based Wind Farm Controller

    DEFF Research Database (Denmark)

    Kazda, Jonas; Cutululis, Nicolaos Antonio

    WindFarm [2]. SimWindFarm allows for the simultaneous simulation of the turbulent hub height flow field in the wind farm, the turbine dynamics and the wind farm control. The tests show a reduction of loads when compared to other optimal wind farm control approaches. Future work shall enhance the controller......Cumulated O&M costs of offshore wind farms are comparable with wind turbine CAPEX of such wind farm. In wind farms, wake effects can result in up to 80% higher fatigue loads at downstream wind turbines [1] and consequently larger O&M costs. The present work therefore investigates to reduce...... these loads during the provision of grid balancing services using optimal model-based wind farm control. Wind farm controllers coordinate the operating point of wind turbines in a wind farm in order to achieve a given objective. The investigated objective of the control in this work is to follow a total wind...

  19. Comparison of analytical methods for calculation of wind loads

    Science.gov (United States)

    Minderman, Donald J.; Schultz, Larry L.

    1989-01-01

    The following analysis is a comparison of analytical methods for calculation of wind load pressures. The analytical methods specified in ASCE Paper No. 3269, ANSI A58.1-1982, the Standard Building Code, and the Uniform Building Code were analyzed using various hurricane speeds to determine the differences in the calculated results. The winds used for the analysis ranged from 100 mph to 125 mph and applied inland from the shoreline of a large open body of water (i.e., an enormous lake or the ocean) a distance of 1500 feet or ten times the height of the building or structure considered. For a building or structure less than or equal to 250 feet in height acted upon by a wind greater than or equal to 115 mph, it was determined that the method specified in ANSI A58.1-1982 calculates a larger wind load pressure than the other methods. For a building or structure between 250 feet and 500 feet tall acted upon by a wind rangind from 100 mph to 110 mph, there is no clear choice of which method to use; for these cases, factors that must be considered are the steady-state or peak wind velocity, the geographic location, the distance from a large open body of water, and the expected design life and its risk factor.

  20. Application of Load Carrying Sandwich Elements in Wind Turbine Blades

    DEFF Research Database (Denmark)

    Jensen, Jacob Fisker; Schultz, Jacob Pagh; Berggreen, Carl Christian

    2005-01-01

    The present work investigates the possibilities and drawbacks when applying sandwich as opposed to single skin composites in the flanges of the load carrying spar in a future 180 m wind turbine rotor. FEA is applied to investigate two basic designs with single skin and sandwich flanges respectively...

  1. Aerodynamic load control strategy of wind turbine in microgrid

    Science.gov (United States)

    Wang, Xiangming; Liu, Heshun; Chen, Yanfei

    2017-12-01

    A control strategy is proposed in the paper to optimize the aerodynamic load of the wind turbine in micro-grid. In grid-connection mode, the wind turbine adopts a new individual variable pitch control strategy. The pitch angle of the blade is rapidly given by the controller, and the pitch angle of each blade is fine tuned by the weight coefficient distributor. In islanding mode, according to the requirements of energy storage system, a given power tracking control method based on fuzzy PID control is proposed. Simulation result shows that this control strategy can effectively improve the axial aerodynamic load of the blade under rated wind speed in grid-connection mode, and ensure the smooth operation of the micro-grid in islanding mode.

  2. Assessment of Load Extrapolation Methods for Wind Turbines

    DEFF Research Database (Denmark)

    Toft, Henrik Stensgaard; Sørensen, John Dalsgaard; Veldkamp, Dick

    2011-01-01

    threshold method with two different threshold values. The comparisons show that the goodness of fit for the local distribution has a significant influence on the results, but the peak over threshold method with a threshold value on the mean plus 1.4 standard deviations generally gives the best results......In the present paper, methods for statistical load extrapolation of wind-turbine response are studied using a stationary Gaussian process model, which has approximately the same spectral properties as the response for the out-of-plane bending moment of a wind-turbine blade. For a Gaussian process......, an approximate analytical solution for the distribution of the peaks is given by Rice. In the present paper, three different methods for statistical load extrapolation are compared with the analytical solution for one mean wind speed. The methods considered are global maxima, block maxima, and the peak over...

  3. Assessment of load extrapolation methods for wind turbines

    DEFF Research Database (Denmark)

    Toft, H.S.; Sørensen, John Dalsgaard; Veldkamp, D.

    2010-01-01

    threshold method with two different threshold values. The comparisons show that the goodness of fit for the local distribution has a significant influence on the results, but the peak over threshold method with a threshold value on the mean plus 1.4 standard deviations generally gives the best results......In the present paper methods for statistical load extrapolation of wind turbine response are studied using a stationary Gaussian process model which has approximately the same spectral properties as the response for the flap bending moment of a wind turbine blade. For a Gaussian process...... an approximate analytical solution for the distribution of the peaks is given by Rice. In the present paper three different methods for statistical load extrapolation are compared with the analytical solution for one mean wind speed. The methods considered are global maxima, block maxima and the peak over...

  4. Structural investigation of composite wind turbine blade considering various load cases and fatigue life

    International Nuclear Information System (INIS)

    Kong, C.; Bang, J.; Sugiyama, Y.

    2005-01-01

    This study proposes a structural design for developing a medium scale composite wind turbine blade made of E-glass/epoxy for a 750 kW class horizontal axis wind turbine system. The design loads were determined from various load cases specified at the IEC61400-1 international specification and GL regulations for the wind energy conversion system. A specific composite structure configuration, which can effectively endure various loads such as aerodynamic loads and loads due to accumulation of ice, hygro-thermal and mechanical loads, was proposed. To evaluate the proposed composite wind turbine blade, structural analysis was performed by using the finite element method. Parametric studies were carried out to determine an acceptable blade structural design, and the most dominant design parameters were confirmed. In this study, the proposed blade structure was confirmed to be safe and stable under various load conditions, including the extreme load conditions. Moreover, the blade adapted a new blade root joint with insert bolts, and its safety was verified at design loads including fatigue loads. The fatigue life of a blade that has to endure for more than 20 years was estimated by using the well-known S-N linear damage theory, the service load spectrum, and the Spera's empirical equations. With the results obtained from all the structural design and analysis, prototype composite blades were manufactured. A specific construction process including the lay-up molding method was applied to manufacturing blades. Full-scale static structural test was performed with the simulated aerodynamic loads. From the experimental results, it was found that the designed blade had structural integrity. In addition, the measured results of deflections, strains, mass, and radial center of gravity agreed well with the analytical results. The prototype blade was successfully certified by an international certification institute, GL (Germanisher Lloyd) in Germany

  5. Validation of the dynamic wake meander model for loads and power production in the Egmond aan Zee wind farm

    DEFF Research Database (Denmark)

    Larsen, Torben J.; Aagaard Madsen, Helge; Larsen, Gunner Chr.

    2013-01-01

    is excellent regarding power production in both free and wake sector, and a very good agreement is seen for the load comparisons too. This enables the conclusion that wake meandering, caused by large scale ambient turbulence, is indeed an important contribution to wake loading in wind farms. Copyright © 2012......This paper investigates wake effects on load and power production by using the dynamic wake meander (DWM) model implemented in the aeroelastic code HAWC2. The instationary wind farm flow characteristics are modeled by treating the wind turbine wakes as passive tracers transported downstream using...... a meandering process driven by the low frequent cross-wind turbulence components. The model complex is validated by comparing simulated and measured loads for the Dutch Egmond aan Zee wind farm consisting of 36 Vestas V90 turbine located outside the coast of the Netherlands. Loads and production are compared...

  6. Comparison of wind pressure measurements on Silsoe ...

    African Journals Online (AJOL)

    Comparison of wind pressure measurements on Silsoe experimental building from full-scale observation, wind-tunnel experiments and various CFD techniques. ... for anisotropic turbulence and curvature related strain effects and the same have been compared with the full-scale and wind-tunnel data for the present study.

  7. Decentralized & Adaptive Load-Frequency Control Scheme of Variable Speed Wind Turbines

    DEFF Research Database (Denmark)

    Hoseinzadeh, Bakhtyar; Silva, Filipe Miguel Faria da; Bak, Claus Leth

    2014-01-01

    In power systems with high penetration of Wind Power (WP), transferring a part of Load Frequency Control (LFC) burden to variable speed Wind Turbines (WTs) is inevitable. The conventional LFC schemes merely rely on frequency information and since frequency is a common variable throughout the netw......In power systems with high penetration of Wind Power (WP), transferring a part of Load Frequency Control (LFC) burden to variable speed Wind Turbines (WTs) is inevitable. The conventional LFC schemes merely rely on frequency information and since frequency is a common variable throughout...... and therefore determining the contribution factor of each individual WT to gain an adaptive LFC approach. The Electrical Distance (ED) concept confirms that the locally measured voltage decay is a proper criterion of closeness to the disturbance place. Numerical simulations carried out in DigSilent Power...

  8. High resolution wind measurements for offshore wind energy development

    Science.gov (United States)

    Nghiem, Son Van (Inventor); Neumann, Gregory (Inventor)

    2013-01-01

    A method, apparatus, system, article of manufacture, and computer readable storage medium provide the ability to measure wind. Data at a first resolution (i.e., low resolution data) is collected by a satellite scatterometer. Thin slices of the data are determined. A collocation of the data slices are determined at each grid cell center to obtain ensembles of collocated data slices. Each ensemble of collocated data slices is decomposed into a mean part and a fluctuating part. The data is reconstructed at a second resolution from the mean part and a residue of the fluctuating part. A wind measurement is determined from the data at the second resolution using a wind model function. A description of the wind measurement is output.

  9. Floating wind generators offshore wind farm: Implications for structural loads and control actions

    International Nuclear Information System (INIS)

    Garcia, E.; Morant F, Quiles E.; Correcher, A.

    2009-01-01

    This paper describes the work currently carried out in the design of floating wind generators and their involvement in the future development of power generation in marine farms in depths exceeding 20 m. We discuss the main issues to be taken into account in the design of floating platforms, including the involvement of structural loads they bear. Also from a standpoint of control engineering are discussed strategies to reduce structural loads such a system to ensure adequate durability and therefore ensuring their economic viability. Finally, the abstract modeling tools for floating wind turbines that can be used in both structural design and the design of appropriate control algorithms

  10. Predicting the Extreme Loads on a Wind Turbine Considering Uncertainty in Airfoil Data

    DEFF Research Database (Denmark)

    Abdallah, Imad; Natarajan, Anand; Sørensen, John Dalsgaard

    2014-01-01

    The sources contributing to uncertainty in a wind turbine blade static airfoil data include wind tunnel testing, CFD calculations, 3D rotational corrections based on CFD or emprircal models, surface roughness corrections, Reynolds number corrections, expansion to the full 360-degree angle of attack...... range, validation by full scale measurements, and geometric distortions of the blade during manufacturing and under loading. In this paper a stochastic model of the static airfoil data is proposed to supplement the prediction of extreme loads effects for large wind turbines. It is shown...... that the uncertainty in airfoil data can have e significant impact on the prediction of extreme loads effects depending on the component, and the correlation along the span of the blade....

  11. WISPER and WISPERX: Final definition of two standardised fatigue loading sequences for wind turbine blades

    Science.gov (United States)

    Tenhave, A. A.

    1992-09-01

    Relevant information used to develop WISPER (Wind turbine reference Spectrum) and WISPERX, standardized variable amplitude test loading histories for use in the fatigue design of horizontal axis wind turbine blades, is presented. WISPER and WISPERX are based on flap load service measurements on nine different horizontal axis wind turbines, covering a wide range of materials, rotor diameters and geographical locations. Their backgrounds are reported, basic data and associated data handling procedures are described, and quantitative data analysis results and statistical information on both standards are presented. The information given will enable fatigue specialists to judge whether the standard will suit their test objectives and to check for correct application of the load sequences on their test equipment.

  12. Device Loading of Modular Multilevel Converter in Wind Power

    DEFF Research Database (Denmark)

    Popova, L.; Ma, Ke; Blaabjerg, Frede

    2015-01-01

    of the MMC to wind energy systems is studied. The converters used to connect the wind turbine to the grid, which have rated active powers of 2MW and 10MW, are proposed and investigated. The electrical losses and thermal loading of the power devices in the proposed converter solutions are analyzed based...... applications, and the losses are evenly distributed between the submodules of the MMC. However, inside a submodule, the losses of the power devices are not equal, which may lead to the de-rating of the converter....

  13. AC-DC integrated load flow calculation for variable speed offshore wind farms

    DEFF Research Database (Denmark)

    Zhao, Menghua; Chen, Zhe; Blaabjerg, Frede

    2005-01-01

    This paper proposes a sequential AC-DC integrated load flow algorithm for variable speed offshore wind farms. In this algorithm, the variable frequency and the control strategy of variable speed wind turbine systems are considered. In addition, the losses of wind turbine systems and the losses...... of converters are also integrated into the load flow algorithm. As a general algorithm, it can be applied to different types of wind farm configurations, and the load flow is related to the wind speed....

  14. Shear and Turbulence Estimates for Calculation of Wind Turbine Loads and Responses Under Hurricane Strength Winds

    Science.gov (United States)

    Kosovic, B.; Bryan, G. H.; Haupt, S. E.

    2012-12-01

    Schwartz et al. (2010) recently reported that the total gross energy-generating offshore wind resource in the United States in waters less than 30m deep is approximately 1000 GW. Estimated offshore generating capacity is thus equivalent to the current generating capacity in the United States. Offshore wind power can therefore play important role in electricity production in the United States. However, most of this resource is located along the East Coast of the United States and in the Gulf of Mexico, areas frequently affected by tropical cyclones including hurricanes. Hurricane strength winds, associated shear and turbulence can affect performance and structural integrity of wind turbines. In a recent study Rose et al. (2012) attempted to estimate the risk to offshore wind turbines from hurricane strength winds over a lifetime of a wind farm (i.e. 20 years). According to Rose et al. turbine tower buckling has been observed in typhoons. They concluded that there is "substantial risk that Category 3 and higher hurricanes can destroy half or more of the turbines at some locations." More robust designs including appropriate controls can mitigate the risk of wind turbine damage. To develop such designs good estimates of turbine loads under hurricane strength winds are essential. We use output from a large-eddy simulation of a hurricane to estimate shear and turbulence intensity over first couple of hundred meters above sea surface. We compute power spectra of three velocity components at several distances from the eye of the hurricane. Based on these spectra analytical spectral forms are developed and included in TurbSim, a stochastic inflow turbulence code developed by the National Renewable Energy Laboratory (NREL, http://wind.nrel.gov/designcodes/preprocessors/turbsim/). TurbSim provides a numerical simulation including bursts of coherent turbulence associated with organized turbulent structures. It can generate realistic flow conditions that an operating turbine

  15. Wind loads on stand-off photovoltaic systems on pitched roofs

    NARCIS (Netherlands)

    Geurts, C.P.W.; Blackmore, P.

    2013-01-01

    Stand-off photovoltaic systems are a popular measure for retrofitting of existing pitched roofs.Panels are generally mounted parallel to the existing roof coverings,usually roofing tiles.Full scale and wind tunnel experiments have been performed to determine the net uplift loads on these systems,

  16. Wind measurement via direct detection lidar

    Science.gov (United States)

    Afek, I.; Sela, N.; Narkiss, N.; Shamai, G.; Tsadka, S.

    2013-10-01

    Wind sensing Lidar is considered a promising technology for high quality wind measurements required for various applications such as hub height wind resource assessment, power curve measurements and advanced, real time, forward looking turbine control. Until recently, the only available Lidar technology was based on coherent Doppler shift detection, whose market acceptance has been slow primarily due to its exuberant price. Direct detection Lidar technology provides an alternative to remote sensing of wind by incorporating high precision measurement, a robust design and an affordable price tag.

  17. Wind Simulation for Extreme and Fatigue Loads

    DEFF Research Database (Denmark)

    Nielsen, Morten; Larsen, Gunner Chr.; Mann, Jakob

    2003-01-01

    by many orders of magnitude, mainly because the measured pdf is non-Gaussian. Methods for simulation of turbulent signals have been developed and theircomputational efficiency are considered. The methods are applicable for multiple processes with individual spectra and probability distributions. Non......-Gaussian processes are simulated by the correlation-distortion method. Non-stationary processes areobtained by Bezier interpolation between a set of stationary simulations with identical random seeds. Simulation of systems with some signals available is enabled by conditional statistics. A versatile method...... is formulated as the variational problem of finding the most probable adjustment of a standard simulation of a stationary Gaussian process subject to relevant event conditions, which are formulated as linear combination of pointsin the realization. The method is generalized for multiple correlated series...

  18. The determination of the extreme loads on wind turbines – some practical issues

    NARCIS (Netherlands)

    Bierbooms, W.A.A.M.

    2010-01-01

    The probabilistic method commonly applied to arrive at the ultimate loading is as follows: for several different mean wind speeds load simulations are performed. For each mean wind speed a conditional distribution can be fitted to the load maxima for that particular wind speed. The overall

  19. Load Sharing of Wind Based Microgrid in Autonomous Operation

    Directory of Open Access Journals (Sweden)

    Aarti Gupta

    2014-01-01

    Full Text Available Autonomous wind energy conversion systems sharing a common load consist of a number of voltage source converters operating in parallel. A suitable control system should ensure desired load sharing among these as a number of these sources operating in parallel are required to meet the load demand and load excursions should not lead to instability of the system. In absence of the grid there is no reference angle for synchronization. Hence, a control scheme for parallel-connected three-phase converters incorporating the desirable features needs to be developed in order to exploit the renewable energy sources, which are intermittent in nature as effectively as possible in case of an autonomous microgrid. A simple and effective droop control strategy without the use of conventional αβ technique incorporating only dq components has been proposed for load sharing among wind energy conversion systems connected by back to back voltage source converters in autonomous operation. The need for communication link should also be avoided, hence reducing the system cost. The system is modelled using Matlab and the control is authenticated by simulation results.

  20. Thermal loading and reliability of 10 MW multilevel wind power converter at different wind roughness classes

    DEFF Research Database (Denmark)

    Isidori, Andrea; Rossi, Fabio Mario; Blaabjerg, Frede

    2012-01-01

    This paper focuses on the design, thermal loading and reliability of a three-level Neutral Point Clamped (3-L NPC) back-to-back full scale converter for a 10 MW direct-drive wind turbine equipped with a Permanent Magnet Synchronous Generator (PMSG). The reliability performance of the three...

  1. Vertical Axis Wind Turbine Design Load Cases Investigation and Comparison with Horizontal Axis Wind Turbine

    DEFF Research Database (Denmark)

    Galinos, Christos; Larsen, Torben J.; Aagaard Madsen, Helge

    2016-01-01

    The paper studies the applicability of the IEC 61400-1 ed.3, 2005 International Standard of wind turbine minimum design requirements in the case of an onshore Darrieus VAWT and compares the results of basic Design Load Cases (DLCs) with those of a 3-bladed HAWT. The study is based on aeroelastic ...

  2. Active aerodynamic load control on wind turbines : Aeroservoelastic modeling and wind tunnel

    NARCIS (Netherlands)

    Barlas, A.

    2011-01-01

    This thesis investigates particular concepts and technologies that can alleviate fatigue loads on wind turbines by using distributed active aerodynamic devices on the blades, a concept briefly referred to as `smart blades'. Firstly, published research work on smart control devices is reviewed, and

  3. Doppler Lidar for Wind Measurements on Venus

    Science.gov (United States)

    Singh, Upendra N.; Emmitt, George D.; Yu, Jirong; Kavaya, Michael J.

    2010-01-01

    NASA Langley Research Center has a long history of developing 2-micron laser transmitter for wind sensing. With support from NASA Laser Risk Reduction Program (LRRP) and Instrument Incubator Program (IIP), NASA Langley Research Center has developed a state-of-the-art compact lidar transceiver for a pulsed coherent Doppler lidar system for wind measurement. The transmitter portion of the transceiver employs the high-pulse-energy, Ho:Tm:LuLiF, partially conductively cooled laser technology developed at NASA Langley. The transceiver is capable of 250 mJ pulses at 10 Hz. It is very similar to the technology envisioned for coherent Doppler lidar wind measurements from Earth and Mars orbit. The transceiver is coupled to the large optics and data acquisition system in the NASA Langley VALIDAR mobile trailer. The large optics consists of a 15-cm off-axis beam expanding telescope, and a full-hemispheric scanner. Vertical and horizontal vector winds are measured, as well as relative backscatter. The data acquisition system employs frequency domain velocity estimation and pulse accumulation. It permits real-time display of the processed winds and archival of all data. This lidar system was recently deployed at Howard University facility in Beltsville, Mary-land, along with other wind lidar systems. Coherent Doppler wind lidar ground-based wind measurements and comparisons with other sensors will be presented. A simulation and data product for wind measurement at Venus will be presented.

  4. Lidar Turbulence Measurements for Wind Energy

    DEFF Research Database (Denmark)

    Mann, Jakob; Sathe, Ameya; Gottschall, Julia

    2012-01-01

    Modeling of the systematic errors in the second-order moments of wind speeds measured by continuous-wave (ZephIR) and pulsed (WindCube) lidars is presented. These lidars use the velocity azimuth display technique to measure the velocity vector. The model is developed for the line-of-sight averaging...

  5. Lidar Turbulence Measurements for Wind Energy

    DEFF Research Database (Denmark)

    Mann, Jakob; Sathe, Ameya; Gottschall, Julia

    2012-01-01

    Modeling of the systematic errors in the second-order moments of wind speeds measured by continuous-wave (ZephIR) and pulsed (WindCube) lidars is presented. These lidars use the velocity azimuth display technique to measure the velocity vector. The model is developed for the line-of-sight averagi...

  6. Wake-Effect Minimising Optimal Control of Wind Farms, with Load Reduction

    DEFF Research Database (Denmark)

    Borchersen, Anders Bech; Larsen, Jesper Abildgaard; Sivabalan, Senthuran

    2014-01-01

    A power generating wind turbine causes a speed reduction and an added turbulence to the wind. Wind turbines in wind farms are often caught in these wakes and are found to have a higher structural load than non affected wind turbines. This article investigates the possibility of designing a contro...

  7. Effects of gain-scheduling methods in a classical wind turbine controller on wind turbine aeroservoelastic modes and loads

    DEFF Research Database (Denmark)

    Tibaldi, Carlo; Henriksen, Lars Christian; Hansen, Morten Hartvig

    2014-01-01

    The eects of dierent gain-scheduling methods for a classical wind turbine controller, operating in full load region, on the wind turbine aeroservoelastic modes and loads are investigated in this work. The dierent techniques are derived looking at the physical problem to take into account the chan......The eects of dierent gain-scheduling methods for a classical wind turbine controller, operating in full load region, on the wind turbine aeroservoelastic modes and loads are investigated in this work. The dierent techniques are derived looking at the physical problem to take into account...

  8. Full load estimation of an offshore wind turbine based on SCADA and accelerometer data

    Science.gov (United States)

    Noppe, N.; Iliopoulos, A.; Weijtjens, W.; Devriendt, C.

    2016-09-01

    As offshore wind farms (OWFs) grow older, the optimal use of the actual fatigue lifetime of an offshore wind turbine (OWT) and predominantly its foundation will get more important. In case of OWTs, both quasi-static wind/thrust loads and dynamic loads, as induced by turbulence, waves and the turbine's dynamics, contribute to its fatigue life progression. To estimate the remaining useful life of an OWT, the stresses acting on the fatigue critical locations within the structure should be monitored continuously. Unfortunately, in case of the most common monopile foundations these locations are often situated below sea-level and near the mud line and thus difficult or even impossible to access for existing OWTs. Actual strain measurements taken at accessible locations above the sea level show a correlation between thrust load and several SCADA parameters. Therefore a model is created to estimate the thrust load using SCADA data and strain measurements. Afterwards the thrust load acting on the OWT is estimated using the created model and SCADA data only. From this model the quasi static loads on the foundation can be estimated over the lifetime of the OWT. To estimate the contribution of the dynamic loads a modal decomposition and expansion based virtual sensing technique is applied. This method only uses acceleration measurements recorded at accessible locations on the tower. Superimposing both contributions leads to a so-called multi-band virtual sensing. The result is a method that allows to estimate the strain history at any location on the foundation and thus the full load, being a combination of both quasi-static and dynamic loads, acting on the entire structure. This approach is validated using data from an operating Belgian OWF. An initial good match between measured and predicted strains for a short period of time proofs the concept.

  9. Participation of Flexible Loads in Load Frequency Control to Support High Wind Penetration

    DEFF Research Database (Denmark)

    Uslu, Umur; Zhang, Boyang; Pillai, Jayakrishnan Radhakrishna

    2016-01-01

    The increasing amount of fluctuating wind power penetration in power systems presents many challenges to its operation and control. The new wind power plants are replacing many of the conventional large power plants that ensure power balancing and ancillary services for stable and reliable...... operation of the grid. Therefore, new solutions for power balancing reserves have to be explored and utilized by the grid utilities. To meet these challenges, large sizable loads like alkaline electrolysers, heat pumps and electric vehicles which are gaining popularity can provide system support to the grid...... through their inherent flexibility and energy storage characteristics. This paper investigates the possibilities and potential of such flexible loads to participate in power system frequency regulation in a wind dominated power system. The results show that these consumption units provide better...

  10. Inflow characteristics associated with high-blade-loading events in a wind farm

    Energy Technology Data Exchange (ETDEWEB)

    Kelley, N.D.

    1993-07-01

    The stochastic characteristics of the turbulent inflow have been shown to be of major significance in the accumulation of fatigue in wind turbines. Because most of the wind turbine installations in the US have taken place in multi-turbine or wind farm configurations, the fatigue damage associated with the higher turbulence levels within such arrangements must be taken into account when making estimates of component service lifetimes. The simultaneous monitoring of two adjacent wind turbines over a wide range of turbulent inflow conditions has given the authors more confidence in describing the structural load distributions that can be expected in such an environment. The adjacent testing of the two turbines allowed the authors to postulate that observed similarities in the response dynamics and load distributions could be considered quasi-universal, while the dissimilarities could be considered to result from the differing design of the rotors. The format has also allowed them to begin to define appropriate statistical load distribution models for many of the critical components in which fatigue is a major driver of the design. In addition to the adjacent turbine measurements, they also briefly discuss load distributions measured on a teetered-hub turbine.

  11. Planetary Load Sharing in Three-Point Mounted Wind Turbine Gearboxes: A Design and Test Comparison

    Energy Technology Data Exchange (ETDEWEB)

    Keller, Jonathan [National Renewable Energy Lab. (NREL), Golden, CO (United States); Guo, Yi [National Renewable Energy Lab. (NREL), Golden, CO (United States); Zhang, Zhiwei [Romax InSight, Nottingham, (United Kingdom); Lucas, Doug [The Timken Company, Jackson Township, OH (United States)

    2017-04-06

    This work compares the planetary load-sharing characteristics of wind turbine gearboxes supported by cylindrical roller bearings (CRBs) and preloaded tapered roller bearings (TRBs) when subjected to rotor moments. Planetary bearing loads were measured in field-representative dynamometer tests and compared to loads predicted by finite-element models. Preloaded TRBs significantly improved load sharing. In pure torque conditions, the upwind planet bearing load in the gearbox with preloaded TRBs was only 14% more than the assumed load compared to 47% more for the gearbox with CRBs. Consequently, the predicted fatigue life of the complete set of planetary bearings for the gearbox with preloaded TRBs is 3.5 times greater than that of the gearbox with CRBs.

  12. Fatigue of bridges with a horizontal rotation axle under random wind load

    NARCIS (Netherlands)

    Maljaars, J.; Steenbergen, R.D.J.M.

    2012-01-01

    The operating mechanisms of movable bridges are subjected to various types of fluctuating loads which may induce fatigue damage. Wind load acting on the bridge deck - when the bridge is open - is one of the important load types. A wind load model is proposed that can be used in the fatigue design

  13. Wind turbine wake measurement in complex terrain

    DEFF Research Database (Denmark)

    Hansen, Kurt Schaldemose; Larsen, Gunner Chr.; Menke, Robert

    2016-01-01

    SCADA data from a wind farm and high frequency time series measurements obtained with remote scanning systems have been analysed with focus on identification of wind turbine wake properties in complex terrain. The analysis indicates that within the flow regime characterized by medium to large...

  14. A FULL-SCALE MEASUREMENT OF WIND ACTIONS AND EFFECTS ON A SEA-CROSSING BRIDGE

    Directory of Open Access Journals (Sweden)

    Yi Zhou

    2017-10-01

    Full Text Available Wind loading is critical for the large-span and light-weight structures, and field measurement is the most effective way to evaluate the wind resistance performance of a specific structure. This study investigates the wind characteristics and wind-induced vibration on a sea-crossing bridge in China, namely Donghai Bridge, based on up to six years of monitoring data. It is found that: (1 there exists obvious discrepancy between the measured wind field parameters and the values suggested by the design code; and the wind records at the bridge site is easily interfered by the bridge structure itself, which should be considered in interpreting the measurements and designing structural health monitoring systems (SHMS; (2 for strong winds with high non-stationarity, a shorter averaging time than 10-min is preferable to obtain more stable turbulent wind characteristics; (3 the root mean square (RMS of the wind-induced acceleration of the girder may increase in an approximately quadratic curve relationship with the mean wind speed; and (4 compared to traffic load, the wind dominates the girder’s lateral vibration amplitude, while the heavy-load traffic might exert more influence on the girder’s vertical and torsional vibrations than the high winds. This study provides field evidence for the wind-resistant design and evaluation of bridges in similar operational conditions.

  15. Predicting extreme loads effects on wind turbines considering uncertainty in airfoil data

    DEFF Research Database (Denmark)

    Abdallah, Imad; Natarajan, Anand; Sørensen, John Dalsgaard

    2013-01-01

    The sources contributing to uncertainty in a wind turbine blade static airfoil data include wind tunnel testing, CFD calculations, 3D rotational corrections based on CFD or empirical models, surface roughness corrections, Reynolds number corrections, expansion to the full 360-degree angle of atta...... that the uncertainty in airfoil data can have a significant impact on the prediction of extreme loads effects depending on the component, and the correlation along the span of the blade.......The sources contributing to uncertainty in a wind turbine blade static airfoil data include wind tunnel testing, CFD calculations, 3D rotational corrections based on CFD or empirical models, surface roughness corrections, Reynolds number corrections, expansion to the full 360-degree angle of attack...... range, validation by full scale measurements, and geometric distortions of the blade during manufacturing and under loading. In this paper a stochastic model of the static airfoil data is proposed to supplement the prediction of extreme loads effects for large wind turbines. It is shown...

  16. Dynamics and Control of High-Rise Buildings under Multidirectional Wind Loads

    Directory of Open Access Journals (Sweden)

    Aly Mousaad Aly

    2011-01-01

    Full Text Available This paper presents a procedure for the response prediction and reduction in high-rise buildings under multidirectional wind loads. The procedure is applied to a very slender tall building that is instructive. The structure is exposed to both cross-wind and along-wind loads obtained from pressure measurements on a rigid model (scaled 1 : 100 that was tested in a wind tunnel with two different configurations of the surroundings. In the theoretical formulation, dynamic equations of the structure are introduced by finite element and 3D lumped mass modeling. The lateral responses of the building in the two directions are controlled at the same time using tuned mass dampers (TMDs and active tuned mass dampers (ATMDs commanded by LQR and fuzzy logic controllers, while the effects of the uncontrolled torsional response of the structure are simultaneously considered. Besides their simplicity, fuzzy logic controllers showed similar trend as LQR controllers under multidirectional wind loads. Nevertheless, the procedure presented in this study can help decision makers, involved in the design process, to choose among innovative solutions like structural control, different damping techniques, modifying geometry, or even changing materials.

  17. Validated Loads Prediction Models for Offshore Wind Turbines for Enhanced Component Reliability

    DEFF Research Database (Denmark)

    Koukoura, Christina

    are used for the modification of the sub-structure/foundation design for possible material savings. First, the background of offshore wind engineering, including wind-wave conditions, support structure, blade loading and wind turbine dynamics are presented. Second, a detailed description of the site...... is given and the metocean conditions are analyzed. The joint wind-wave distribution and the probability of the misalignment angles are estimated. Third, the calibration process of the different components is thoroughly depicted. The turbulence intensity implemented in the simulations is extracted from...... response of a boat impact. The first and second modal damping of the system during normal operation both from measurements and simulations are identified with the implementation of the Enhanced Frequency Domain Decomposition technique. The effect of damping on the side-side fatigue of the support structure...

  18. Field measurement of wind pressure and wind-induced vibration of large-span spatial cable-truss system under strong wind or typhoon

    Directory of Open Access Journals (Sweden)

    ZHANG Zhihong

    2013-10-01

    Full Text Available In order to ensure wind-resistance safety of large-span pre-stressed flexible system in southeast coast area of China,and to prepare something for revising of current codes of practice or technical standards,the present paper conducts field measurement of wind pressure and wind-induced vibration of a practical and typical large-span spatial cable-truss system-lunar stadium in Yueqing city.Wind loading and wind effects on full-scale structure under strong wind or typhoon in real architectural environment can be obtained directly and effectively.Field measurement is the best way to investigate the wind loading property,wind effects,and wind-structure interactions of large-span flexible system.Measured data will be highly valuable for scientific research and practical design.On the other hand,it also provides the basis of wind-resistance safety design of this kind of tension structures.If any creative development,it would dramatically improve the research level of large-span pre-stressed flexible system in our country.

  19. Wind measurements for wind energy applications. A review

    DEFF Research Database (Denmark)

    Mortensen, N.G.

    1994-01-01

    A review is given of the error sources and uncertainties in cup and sonic anemometry. In both cases the effects of the tower, boom and other mounting arrangements, as well as the siting of the anemometer, should be considered carefully. Cup anemometer measurements are inherently biased due...... to the turbulent nature of the wind, but these errors can be neglected in many applications if a well-designed, fast-responding anemometer is used. The response characteristics of sonic anemometers are fairly complicated. Based on wind tunnel investigations and field comparisons some of the associated errors...

  20. Measuring tropospheric wind with microwave sounders

    Science.gov (United States)

    Lambrigtsen, B.; Su, H.; Turk, J.; Hristova-Veleva, S. M.; Dang, V. T.

    2017-12-01

    In its 2007 "Decadal Survey" of earth science missions for NASA the U.S. National Research Council recommended that a Doppler wind lidar be developed for a three-dimensional tropospheric winds mission ("3D-Winds"). The technology required for such a mission has not yet been developed, and it is expected that the next Decadal Survey, planned to be released by the end of 2017, will put additional emphasis on the still pressing need for wind measurements from space. The first Decadal Survey also called for a geostationary microwave sounder (GMS) on a Precipitation and All-weather Temperature and Humidity (PATH) mission, which could be used to measure wind from space. Such a sounder, the Geostationary Synthetic Thinned Aperture Radiometer (GeoSTAR), has been developed at the Jet Propulsion Laboratory (JPL). The PATH mission has not yet been funded by NASA, but a low-cost subset of PATH, GeoStorm has been proposed as a hosted payload on a commercial communications satellite. Both PATH and GeoStorm would obtain frequent (every 15 minutes of better) measurements of tropospheric water vapor profiles, and they can be used to derive atmospheric motion vector (AMV) wind profiles, even in the presence of clouds. Measurement of wind is particularly important in the tropics, where the atmosphere is largely not in thermal balance and wind estimates cannot generally be derived from temperature and pressure fields. We report on simulation studies of AMV wind vectors derived from a GMS and from a cluster of low-earth-orbiting (LEO) small satellites (e.g., CubeSats). The results of two separate simulation studies are very encouraging and show that a ±2 m/s wind speed precision is attainable, which would satisfy WMO requirements. A GMS observing system in particular, which can be implemented now, would enable significant progress in the study of atmospheric dynamics. Copyright 2017 California Institute of Technology. Government sponsorship acknowledged

  1. Calculating the sensitivity of wind turbine loads to wind inputs using response surfaces

    DEFF Research Database (Denmark)

    Rinker, Jennifer M.

    2016-01-01

    at a low computational cost. Sobol sensitivity indices (SIs) can then be calculated with relative ease using the calibrated response surface. The proposed methodology is demonstrated by calculating the total sensitivity of the maximum blade root bending moment of the WindPACT 5 MW reference model to four......This paper presents a methodology to calculate wind turbine load sensitivities to turbulence parameters through the use of response surfaces. A response surface is a high-dimensional polynomial surface that can be calibrated to any set of input/output data and then used to generate synthetic data...... turbulence input parameters: a reference mean wind speed, a reference turbulence intensity, the Kaimal length scale, and a novel parameter reflecting the nonstationarity present in the inflow turbulence. The input/output data used to calibrate the response surface were generated for a previous project...

  2. A Wind Farm Controller for Load and Power Optimization in a Farm

    DEFF Research Database (Denmark)

    Soleimanzadeh, Maryam; Brand, Arno; Wisniewski, Rafal

    2011-01-01

    based on low and high wind speed. In low wind speed, the reference signals for rotor speed are adjusted, taking the trade-off between power maximization and load minimization into account. In high wind speed, the power and pitch angle reference signals are determined while structural loads are minimized....

  3. Wind-induced transmission tower foundation loads. A field study-design code comparison

    Energy Technology Data Exchange (ETDEWEB)

    Savory, E. [Department of Mechanical and Materials Engineering, University of Western Ontario, London, Ont. (Canada); Parke, G.A.R.; Disney, P.; Toy, N. [School of Engineering, University of Surrey, Guildford, Surrey GU2 7XH (United Kingdom)

    2008-06-15

    This paper presents a comparison between the wind-induced foundation loads measured on a type L6 transmission line tower during a field study in the UK and those computed using the UK Code of Practice for lattice tower and transmission line design (BS8100). In this work, the Code provisions have been generalised to give the wind-induced strain in each of the tower legs immediately above the foundation as a function of wind direction and wind speed at the top of the tower. The complete data set from the field monitoring has been decomposed to provide a similar formulation for comparison purposes. The analysis shows excellent agreement between the Code calculations and the measured results, within the overall accuracy of the field data. This indicates that, at least for the tower type examined here, the existing design Code provides a reliable transformation of the local wind speed at the top of the tower into tension and compression loads on the foundations. (author)

  4. Planetary Load Sharing in Three-Point-Mounted Wind Turbine Gearboxes: A Design and Test Comparison

    Energy Technology Data Exchange (ETDEWEB)

    Guo, Yi; Keller, Jonathan; Zhang, Zhiwei; Lucas, Doug

    2017-03-08

    The planetary load sharing characteristics of wind turbine gearboxes supported by cylindrical roller bearings (CRBs) and preloaded tapered roller bearings (TRBs) when subjected to rotor moments are compared in this work. Planetary bearing loads were measured in field-representative dynamometer tests and compared to loads predicted by finite-element models. Load sharing was significantly improved with preloaded TRBs. In pure torque conditions, the upwind planet bearing loads in the gearbox with preloaded TRBs were a maximum of 1.14 compared to 1.47 in the gearbox with CRBs. Consequently, the predicted fatigue life of the complete set of planetary bearings for the gearbox with preloaded TRBs is 3.5 times greater than that of the gearbox with CRBs.

  5. Improving Bending Moment Measurements on Wind Turbine Blades

    Energy Technology Data Exchange (ETDEWEB)

    Post, Nathan L.

    2016-03-15

    Full-scale fatigue testing of wind turbine blades is conducted using resonance test techniques where the blade plus additional masses is excited at its first resonance frequency to achieve the target loading amplitude. Because there is not a direct relationship between the force applied by an actuator and the bending moment, the blade is instrumented with strain gauges that are calibrated under static loading conditions to determine the sensitivity or relationship between strain and applied moment. Then, during dynamic loading the applied moment is calculated using the strain response of the structure. A similar procedure is also used in the field to measure in-service loads on turbine blades. Because wind turbine blades are complex twisted structures and the deflections are large, there is often significant cross-talk coupling in the sensitivity of strain gauges placed on the structure. Recent work has shown that a sensitivity matrix with nonzero cross terms must be employed to find constant results when a blade is subjected to both flap and lead-lag loading. However, even under controlled laboratory conditions, potential for errors of 3 percent or more in the measured moment exist when using the typical cross-talk matrix approach due to neglecting the influence of large deformations and torsion. This is particularly critical when considering a biaxial load as would be applied on the turbine or during a biaxial fatigue test. This presentation describes these results demonstrating errors made when performing current loads measurement practices on wind turbine blades in the lab and evaluating potential improvements using enhanced cross-talk matrix approaches and calibration procedures.

  6. A Wind Farm Active Power Dispatch Strategy for Fatigue Load Reduction

    DEFF Research Database (Denmark)

    Zhang, Baohua; N. Soltani, Mohsen; Hu, Weihao

    2016-01-01

    One of the biggest challenges in wind farm management is to cope with requirements from the grid companies and to optimize efficiency and minimize wear on wind turbines. This paper addresses an optimized active power dispatch strategy of a wind farm to reduce the fatigue load of wind turbines, wh...

  7. Variability and smoothing effect of wind power production compared to load variability in the Nordic countries

    DEFF Research Database (Denmark)

    Holttinen, Hannele; Rissanen, Simo; Giebel, Gregor

    2012-01-01

    the viewpoint of wind integration. The smoothing effect is shown as reduction of variability from a single country to Nordic wide wind power. The impact of wind power on the variability that the system sees is depicted by analysing the variability of net load with different wind power penetration levels...

  8. Wind Tunnel Investigation of Ground Wind Loads for Ares Launch Vehicle

    Science.gov (United States)

    Keller, Donald F.; Ivanco, Thomas G.

    2010-01-01

    A three year program was conducted at the NASA Langley Research Center (LaRC) Aeroelasticity Branch (AB) and Transonic Dynamics Tunnel (TDT) with the primary objective to acquire scaled steady and dynamic ground-wind loads (GWL) wind-tunnel data for rollout, on-pad stay, and on-pad launch configurations for the Ares I-X Flight Test Vehicle (FTV). The experimental effort was conducted to obtain an understanding of the coupling of aerodynamic and structural characteristics that can result in large sustained wind-induced oscillations (WIO) on such a tall and slender launch vehicle and to generate a unique database for development and evaluation of analytical methods for predicting steady and dynamic GWL, especially those caused by vortex shedding, and resulting in significant WIO. This paper summarizes the wind-tunnel test program that employed two dynamically-aeroelastically scaled GWL models based on the Ares I-X Flight Test Vehicle. The first model tested, the GWL Checkout Model (CM), was a relatively simple model with a secondary objective of restoration and development of processes and methods for design, fabrication, testing, and data analysis of a representative ground wind loads model. In addition, parametric variations in surface roughness, Reynolds number, and protuberances (on/off) were investigated to determine effects on GWL characteristics. The second windtunnel model, the Ares I-X GWL Model, was significantly more complex and representative of the Ares I-X FTV and included the addition of simplified rigid geometrically-scaled models of the Kennedy Space Center (KSC) Mobile Launch Platform (MLP) and Launch Complex 39B primary structures. Steady and dynamic base bending moment as well as model response and steady and unsteady pressure data was acquired during the testing of both models. During wind-tunnel testing of each model, flow conditions (speed and azimuth) where significant WIO occurred, were identified and thoroughly investigated. Scaled data from

  9. Online wind turbine measurement laboratory

    DEFF Research Database (Denmark)

    Hansen, K.S.; Helgesen Pedersen, K.O.; Schmidt Paulsen, U.

    2006-01-01

    conditions, 3) electrical quantities and 4) mechanical loads in terms of strain gauge signals. The data acquisition system has been designed and implemented by Risø together with students and teachers from DTU. It is based on LabVIEW© combined with a MySQL database for data management. The system enables...

  10. Towards a reliable design of facade and roof elements against wind loading

    NARCIS (Netherlands)

    Geurts, C.P.W.; Staalduinen, P.C. van; Wit, M.S. de

    2004-01-01

    The most vulnerable parts of buildings with respect to wind loading are facades and roofs. Current standards on wind loading provide data to determine design loads for the elements in facades and roofs. These data are available for a limited number of simple building shapes. Up to now there is no

  11. High-Resolution Wind Measurements for Offshore Wind Energy Development

    Science.gov (United States)

    Nghiem, Son V.; Neumann, Gregory

    2011-01-01

    A mathematical transform, called the Rosette Transform, together with a new method, called the Dense Sampling Method, have been developed. The Rosette Transform is invented to apply to both the mean part and the fluctuating part of a targeted radar signature using the Dense Sampling Method to construct the data in a high-resolution grid at 1-km posting for wind measurements over water surfaces such as oceans or lakes.

  12. Measuring training load in sports.

    Science.gov (United States)

    Lambert, Michael Ian; Borresen, Jill

    2010-09-01

    The principle of training can be reduced to a simple "dose-response" relationship. The "response" in this relationship can be measured as a change in performance or the adaptation of a physiological system. The "dose" of training, or physiological stress associated with the training load, is more difficult to measure as there is no absolute "gold standard" which can be used in the field, making it difficult to validate procedures. Attempts have been made to use heart rate as a marker of intensity during training, but the theoretical attractiveness of this method is not supported by the accuracy and the practicality of using this method during training or competition. The session RPE, based on the product of training duration and perceived intensity is more practical and can be used in a variety of sports. However, the score depends on a subjective assessment, and the intersubject comparisons may be inaccurate. The demands of different sports vary and therefore the methods of assessing training need to vary accordingly. The time has come to reach consensus on assessing training accurately in different sports. There is a precedent for this consensus approach with scientists having already done so for the assessment of physical activity, and for defining injuries in rugby, football and cricket. Standardizing these methods has resulted in the quality of research in these areas increasing exponentially.

  13. Stochastic Unit Commitment of Wind-Integrated Power System Considering Air-Conditioning Loads for Demand Response

    Directory of Open Access Journals (Sweden)

    Xiao Han

    2017-11-01

    Full Text Available As a result of extensive penetration of wind farms into electricity grids, power systems face enormous challenges in daily operation because of the intermittent characteristics of wind energy. In particular, the load peak-valley gap has been dramatically widened in wind energy-integrated power systems. How to quickly and efficiently meet the peak-load demand has become an issue to practitioners. Previous literature has illustrated that the demand response (DR is an important mechanism to direct customer usage behaviors and reduce the peak load at critical times. This paper introduces air-conditioning loads (ACLs as a load shedding measure in the DR project. On the basis of the equivalent thermal parameter model for ACLs and the state-queue control method, a compensation cost calculation method for the ACL to shift peak load is proposed. As a result of the fluctuation and uncertainty of wind energy, a two-stage stochastic unit commitment (UC model is developed to analyze the ACL users’ response in the wind-integrated power system. A simulation study on residential and commercial ACLs has been performed on a 10-generator test system. The results illustrate the feasibility of the proposed stochastic programming strategy and that the system peak load can be effectively reduced through the participation of ACL users in DR projects.

  14. Effects of normal and extreme turbulence spectral parameters on wind turbine loads

    DEFF Research Database (Denmark)

    Dimitrov, Nikolay Krasimirov; Natarajan, Anand; Mann, Jakob

    2017-01-01

    Loads simulations as performed to obtain design loads on wind turbines, requires wind turbulence as an input, characterized by parameters associated with the turbulence length scale, dissipation and anisotropy. The effect of variation in these turbulence spectral parameters on the magnitude...... the recommended values in the IEC 61400-1 Ed.3 that is used for wind turbine design. The present paper investigates the impact of Mann turbulence model parameter variations on the design loads envelope for 5 MW and 10 MW reference wind turbines. Specific focus is made on the blade root loads, tower top moments...

  15. Some aspects on wind turbines monitoring. General considerations and loads on horizontal wind turbines

    International Nuclear Information System (INIS)

    Cuerva, A.

    1996-01-01

    The concept Monitoring applied to the Wind Energy technology is similar to the definition used in other branches of Science or Engineering, this is knowing values of variables which have to do with a mechanic system, in our case a wind turbine. These mentioned parameters may have different relationships to our wind turbine; some of them come from the environment the machine is operating in, others, are a measure of how properly the machine is working, and finally, the rest are an assessment of the systems health during its life. In this chapter we will answer questions such as: What do we need to measure? Why is Monitoring mandatory (from the different points of view of people involved in this world)? How can we measure a wind turbine depending on our objectives (Technic, tools, guidance, recommendations, etc.)? And finally What can we expect in the near future? The author wants the reader to keep the idea in mind that Monitoring means the richest and most accurate knowledge on wind turbine's operation (Its environment, performances or health). This is the first step that allows us to optimize the operation mode of the machine and improve it (design, manufacturing, even the used modeling tools). When there is so much money involved, this fact becomes a must. (Author)

  16. Some aspects on wind turbines monitoring. General considerations and loads on horizontal wind turbines

    Energy Technology Data Exchange (ETDEWEB)

    Cuerva, A.

    1996-12-01

    The concept Monitoring applied to the Wind Energy technology is similar to the definition used in other branches of Science or Engineering, this is knowing values of variables which have to do with a mechanic system, in our case a wind turbine. These mentioned parameters may have different relationships to our wind turbine; some of them come from the environment the machine is operating in, others, are a measure of how properly the machine is working, and finally, the rest are an assessment of the ``system`s health`` during its ``life``. In this chapter we will answer questions such as: What do we need to measure? Why is Monitoring mandatory (from the different points of view of people involved in this world)? How can we measure a wind turbine depending on our objectives (Technic, tools, guidance, recommendations, etc)? And finally What can we expect in the near future?. The author wants the reader to keep the idea in mind that Monitoring means the richest and most accurate knowledge on wind turbine`s operation (Its environment, performances of health). This is the first step that allows us to optimize the operation mode of the machine and improve it (design, manufacturing, even the used modeling tools). When there is so much money involved, this fact becomes a must. (Author)

  17. Fiber Laser for Wind Speed Measurements

    DEFF Research Database (Denmark)

    Olesen, Anders Sig

    This PhD thesis evaluates the practical construction and use of a Frequency Stepped Pulse Train modulated coherent Doppler wind lidar (FSPT lidar) for wind speed measurement. The concept of Doppler lidar is introduced as a means to measure line of sight wind speed by the Doppler shift of reflected...... light from aerosols. Central concepts are introduced and developed, i.a. heterodyne detection, carrier-to-noise ratio, probe length, measuring distance, and velocity precision. On this basis the concepts of a FSPT lidar are introduced and its general setup explained. The Lightwave Synthesized Frequency...... Sweeper (LSFS) is introduced and analyzed as a light source for the FSPT lidar. The setup of the LSFS is discussed, and the necessary concepts for modeling and analyzing LSFS noise are developed. The model and measurements are then used to discuss the growth of optical noise in the LSFS and the impact...

  18. Determining the impact of wind on system costs via the temporal patterns of load and wind generation

    International Nuclear Information System (INIS)

    Davis, Clay D.; Gotham, Douglas J.; Preckel, Paul V.; Liu, Andrew L.

    2013-01-01

    Ambitious targets have been set for expanding electricity generation from renewable sources, including wind. Expanding wind power impacts needs for other electricity generating resources. As states plan for increasing levels of wind generation in their portfolio of generation resources it is important to consider how this intermittent resource impacts the need for other generation resources. A case study for Indiana estimates the value of wind capacity and demonstrates how to optimize its level and the levels of other generation resources. Changes are driven by temporal patterns of wind power output and load. System wide impacts are calculated for energy, capacity, and costs under multiple wind expansion scenarios which highlight the geographic characteristics of a systems portfolio of wind generation. The impacts of carbon prices, as proposed in the Bingaman Bill, are considered. Finally, calculations showing the effect increasing levels of wind generation will have on end use Indiana retail rates are included. - Highlights: • We estimate the value of wind capacity. • We determine wind generation's impact on the optimal mix of non-wind generation. • Optimal levels of wind and non-wind generation are determined. • We consider the impact of a carbon price on the optimal mix of resources. • The impact of additional wind capacity on Indiana residential rates is calculated

  19. On Small-Signal Stability of Wind Power System with Full-Load Converter Interfaced Wind Turbines

    DEFF Research Database (Denmark)

    Knüppel, Thyge; Akhmatov, Vladislav; Nielsen, Jørgen Nygård

    2010-01-01

    Small-signal stability analysis of power system oscillations is a well established field within power system analysis, but not much attention has yet been paid to systems with a high penetration of wind turbines and with large wind power plants. In this paper an analysis is presented which assess...... the impact of full-load converter interfaced wind turbines on power system small-signal stability. The study is based on a 7 generator network with lightly damped inter-area modes. A detailed wind turbine model with all grid relevant control functions is used in the study. Furthermore is the wind power plant...

  20. Determination of the wind power systems load to achieve operation in the maximum energy area

    Science.gov (United States)

    Chioncel, C. P.; Tirian, G. O.; Spunei, E.; Gillich, N.

    2018-01-01

    This paper analyses the operation of the wind turbine, WT, in the maximum power point, MPP, by linking the load of the Permanent Magnet Synchronous Generator, PMSG, with the wind speed value. The load control methods at wind power systems aiming an optimum performance in terms of energy are based on the fact that the energy captured by the wind turbine significantly depends on the mechanical angular speed of the wind turbine. The presented control method consists in determining the optimal mechanical angular speed, ωOPTIM, using an auxiliary low power wind turbine, WTAUX, operating without load, at maximum angular velocity, ωMAX. The method relies on the fact that the ratio ωOPTIM/ωMAX has a constant value for a given wind turbine and does not depend on the time variation of the wind speed values.

  1. Fully vs. Sequentially Coupled Loads Analysis of Offshore Wind Turbines

    Energy Technology Data Exchange (ETDEWEB)

    Damiani, Rick; Wendt, Fabian; Musial, Walter; Finucane, Z.; Hulliger, L.; Chilka, S.; Dolan, D.; Cushing, J.; O' Connell, D.; Falk, S.

    2017-06-19

    The design and analysis methods for offshore wind turbines must consider the aerodynamic and hydrodynamic loads and response of the entire system (turbine, tower, substructure, and foundation) coupled to the turbine control system dynamics. Whereas a fully coupled (turbine and support structure) modeling approach is more rigorous, intellectual property concerns can preclude this approach. In fact, turbine control system algorithms and turbine properties are strictly guarded and often not shared. In many cases, a partially coupled analysis using separate tools and an exchange of reduced sets of data via sequential coupling may be necessary. In the sequentially coupled approach, the turbine and substructure designers will independently determine and exchange an abridged model of their respective subsystems to be used in their partners' dynamic simulations. Although the ability to achieve design optimization is sacrificed to some degree with a sequentially coupled analysis method, the central question here is whether this approach can deliver the required safety and how the differences in the results from the fully coupled method could affect the design. This work summarizes the scope and preliminary results of a study conducted for the Bureau of Safety and Environmental Enforcement aimed at quantifying differences between these approaches through aero-hydro-servo-elastic simulations of two offshore wind turbines on a monopile and jacket substructure.

  2. Intercalibration of HRDI and WINDII wind measurements

    Directory of Open Access Journals (Sweden)

    M. D. Burrage

    Full Text Available The High Resolution Doppler Imager (HRDI and the Wind Imaging Interferometer (WINDII in- struments, which are both on the Upper Atmosphere Research Satellite, measure winds by sensing the Doppler shift in atmospheric emission features. Because the two observation sets are frequently nearly coincident in space and time, each provides a very e.ective validation test of the other. Discrepancies due to geophysical di.erences should be much smaller than for comparisons with other techniques (radars, rockets, etc., and the very large sizes of the coincident data sets provide excellent statistics for the study. Issues that have been examined include relative systematic o.sets and the wind magnitudes obtained with the two systems. A significant zero wind position di.erence of ~6 m s–1 is identified for the zonal component, and it appears that this arises from an absolute perturbation in WINDII winds of –4 m s–1 and in HRDI of +2 m s–1. Altitude o.sets appear to be relatively small, and do not exceed 1 km. In addition, no evidence is found for the existence of a systematic wind speed bias between HRDI and WINDII. However, considerable day-to-day variability is found in the quality of the agreement, and RMS di.erences are surprisingly large, typically in the range of 20±30 m s–1.

  3. Intercalibration of HRDI and WINDII wind measurements

    Directory of Open Access Journals (Sweden)

    M. D. Burrage

    1997-09-01

    Full Text Available The High Resolution Doppler Imager (HRDI and the Wind Imaging Interferometer (WINDII in- struments, which are both on the Upper Atmosphere Research Satellite, measure winds by sensing the Doppler shift in atmospheric emission features. Because the two observation sets are frequently nearly coincident in space and time, each provides a very e.ective validation test of the other. Discrepancies due to geophysical di.erences should be much smaller than for comparisons with other techniques (radars, rockets, etc., and the very large sizes of the coincident data sets provide excellent statistics for the study. Issues that have been examined include relative systematic o.sets and the wind magnitudes obtained with the two systems. A significant zero wind position di.erence of ~6 m s–1 is identified for the zonal component, and it appears that this arises from an absolute perturbation in WINDII winds of –4 m s–1 and in HRDI of +2 m s–1. Altitude o.sets appear to be relatively small, and do not exceed 1 km. In addition, no evidence is found for the existence of a systematic wind speed bias between HRDI and WINDII. However, considerable day-to-day variability is found in the quality of the agreement, and RMS di.erences are surprisingly large, typically in the range of 20±30 m s–1.

  4. Evaluation of MOSTAS computer code for predicting dynamic loads in two-bladed wind turbines

    Science.gov (United States)

    Kaza, K. R. V.; Janetzke, D. C.; Sullivan, T. L.

    1979-01-01

    Calculated dynamic blade loads are compared with measured loads over a range of yaw stiffnesses of the DOE/NASA Mod-0 wind turbine to evaluate the performance of two versions of the MOSTAS computer code. The first version uses a time-averaged coefficient approximation in conjunction with a multiblade coordinate transformation for two-bladed rotors to solve the equations of motion by standard eigenanalysis. The results obtained with this approximate analysis do not agree with dynamic blade load amplifications at or close to resonance conditions. The results of the second version, which accounts for periodic coefficients while solving the equations by a time history integration, compare well with the measured data.

  5. Wind Farm Active Power Dispatch for Output Power Maximizing Based on a Wind Turbine Control Strategy for Load Minimizing

    DEFF Research Database (Denmark)

    Zhang, Baohua; Hu, Weihao; Hou, Peng

    2015-01-01

    Inclusion of the wake effect in the wind farm control design (WF) can increase the total captured power by wind turbines (WTs), which is usually implemented by derating upwind WTs. However, derating the WT without a proper control strategy will increase the structural loads, caused by operation i...

  6. How good are remote sensors at measuring extreme winds?

    NARCIS (Netherlands)

    Sathe, A.R.; Courtney, M.; Mann, J.; Wagner, R.

    2011-01-01

    This article describes some preliminary efforts within the SafeWind project, aimed to identify the possible added value of using wind lidars to detect extreme wind events. Exceptionally good performance is now regularly reported in the measurement of the mean wind speed with some wind lidars in flat

  7. Modelling and Measuring Flow and Wind Turbine Wakes in Large Wind Farms Offshore

    DEFF Research Database (Denmark)

    Barthelmie, Rebecca Jane; Hansen, Kurt Schaldemose; Frandsen, Sten Tronæs

    2009-01-01

    Average power losses due to wind turbine wakes are of the order of 10 to 20% of total power output in large offshore wind farms. Accurately quantifying power losses due to wakes is, therefore, an important part of overall wind farm economics. The focus of this research is to compare different types...... power losses due to wakes and loads. The research presented is part of the EC-funded UpWind project, which aims to radically improve wind turbine and wind farm models in order to continue to improve the costs of wind energy. Reducing wake losses, or even reduce uncertainties in predicting power losses...... from wakes, contributes to the overall goal of reduced costs. Here, we assess the state of the art in wake and flow modelling for offshore wind forms, the focus so for has been cases at the Horns Rev wind form, which indicate that wind form models require modification to reduce under-prediction of wake...

  8. Wind farm electrical power production model for load flow analysis

    International Nuclear Information System (INIS)

    Segura-Heras, Isidoro; Escriva-Escriva, Guillermo; Alcazar-Ortega, Manuel

    2011-01-01

    The importance of renewable energy increases in activities relating to new forms of managing and operating electrical power: especially wind power. Wind generation is increasing its share in the electricity generation portfolios of many countries. Wind power production in Spain has doubled over the past four years and has reached 20 GW. One of the greatest problems facing wind farms is that the electrical power generated depends on the variable characteristics of the wind. To become competitive in a liberalized market, the reliability of wind energy must be guaranteed. Good local wind forecasts are therefore essential for the accurate prediction of generation levels for each moment of the day. This paper proposes an electrical power production model for wind farms based on a new method that produces correlated wind speeds for various wind farms. This method enables a reliable evaluation of the impact of new wind farms on the high-voltage distribution grid. (author)

  9. Ballistic Analysis of Capability to Parry the Wind Load at Initial Flight Path of Promising Aircrafts

    Directory of Open Access Journals (Sweden)

    S. N. Ilukhin

    2015-01-01

    Full Text Available The article describes a new approach to solving the problem of parrying the negative impact of the random wind loads at the initial stage of aircraft flight. Based on applied research and many years of practice is proved the usefulness of measures to eliminate the deviations caused by the wind at initial flight path.The paper provides a theoretical justification and formulates the basic law of control to parry the product reversal under the action of random wind. Via example of a modified ballistic target the logic of the functioning of a promising technique for correcting orbital speed is clearly illustrated. This study analyses the influence of the wind load on the dispersion characteristics of the product impact points. To identify the qualitative picture of the process under study was examined flight of the aircraft in the vertical plane. In comparison with uncorrectable case, a trivial example of a mathematical model is used to have an initial assessment of the proposed technique effectiveness. As a determining parameter, was considered a changing angle of the aircraft attack during flight. Using authors-developed algorithms, significant reduction in the dispersion of the product impact points was revealed upon performed calculations, thus bearing evidence of using this method in promising aircrafts of the class under consideration.

  10. Wind Atlas of Bay of Bengal with Satellite Wind Measurement

    DEFF Research Database (Denmark)

    Nadi, Navila Rahman

    footstep towards offshore wind energy analysis for this region. Generally, it is difficult to find offshore wind data relative to the wind turbine hub heights, therefore a starting point is necessary to identify the possible wind power density of the region. In such scenario, Synthetic aperture radars (SAR......The objective of this study is to obtain appropriate offshore location in the Bay of Bengal, Bangladesh for further development of wind energy. Through analyzing the previous published works, no offshore wind energy estimation has been found here. That is why, this study can be claimed as the first......) have proven useful. In this study, SAR based dataset- ENVISAT ASAR has been used for Wind Atlas generation. Furthermore, a comparative study has been performed with Global Wind Atlas (GWA) to determine a potential offshore wind farm. Additionally, the annual energy production of that offshore windfarm...

  11. Directionality Effects of Aligned Wind and Wave Loads on a Y-Shape Semi-Submersible Floating Wind Turbine under Rated Operational Conditions

    Directory of Open Access Journals (Sweden)

    Shengtao Zhou

    2017-12-01

    Full Text Available The Y-shape (triangular semi-submersible foundation has been adopted by most of the built full-scale floating wind turbines, such as Windfloat, Fukushima Mirai and Shimpuu. Considering the non-fully-symmetrical shape and met-ocean condition, the foundation laying angle relative to wind/wave directions will not only influence the downtime and power efficiency of the floating turbine, but also the strength and fatigue safety of the whole structure. However, the dynamic responses induced by various aligned wind and wave load directions have scarcely been investigated comparatively before. In our study, the directionality effects are investigated by means of combined wind and wave tests and coupled multi-body simulations. By comparing the measured data in three load directions, it is found that the differences of platform motions are mainly derived from the wave loads and larger pitch motion can always be observed in one of the directions. To make certain the mechanism underlying the observed phenomena, a coupled multi-body dynamic model of the floating wind turbine is established and validated. The numerical results demonstrate that the second-order hydrodynamic forces contribute greatly to the directionality distinctions for surge and pitch, and the first-order hydrodynamic forces determine the variations of tower base bending moments and nacelle accelerations. These findings indicate the directionality effects should be predetermined comprehensively before installation at sea, which is important for the operation and maintenance of the Y-shape floating wind turbines.

  12. Application of a new method to determine the modal parameters of tall buildings under random wind loading

    NARCIS (Netherlands)

    Steenbergen, R.D.J.M.; Lentzen, S.S.K.

    2011-01-01

    Modal properties of high rise buildings are mostly derived from measurements on existing buildings under dynamic random wind loading. Measured accelerometer signals are translated into values for the natural frequency and damping. In order to obtain reliable values for the modal properties, the

  13. Wake Influence on Dynamic Load Characteristics of Offshore Floating Wind Turbines

    DEFF Research Database (Denmark)

    Jeon, Minu; Lee, Soogab; Kim, Taeseong

    2016-01-01

    Because the flow conditions of an offshore floating wind turbine and onshore fixed wind turbine differ, it is debatable whether the aerodynamic load predictions of an offshore floating wind turbine using the conventional blade-element momentum theory, which does not consider the dynamic wake effe...

  14. Mitigation of Fatigue Loads Using Individual Pitch Control of Wind Turbines Based on FAST

    DEFF Research Database (Denmark)

    Zhang, Yunqian; Chen, Zhe; Cheng, Ming

    2011-01-01

    With the increase of wind turbine dimension and capacity, the wind turbine structures are subjected to prominent loads and fatigue which would reduce the lifetime of wind turbines. Individual pitch control (IPC) is used in this paper to attenuate the blade root bending moment and the tilt and yaw...

  15. Comparison of blade loads of fixed and free yawing wind turbine

    Science.gov (United States)

    Cheney, M. C.; Bielawa, R. L.

    1978-01-01

    The self regulating composite bearingless wind turbine utilizes an automatic pitch control concept and a completely unrestrained yawing degree of freedom. Aerodynamic moments caused by skewed flow provide the control to align the wind turbine with the wind. Model tests demonstrated the feasibility of the concept and analytical studies showed the free system to experience lower blade loads compared to the fixed system.

  16. Controller design for a Wind Farm, Considering both Power and Load Aspects

    DEFF Research Database (Denmark)

    Soleimanzadeh, Maryam; Wisniewski, Rafal

    2011-01-01

    turbine. The control algorithm determines the reference signals for each individual wind turbine controller in two scenarios based on low and high wind speed. In low wind speed, the reference signals for rotor speed are adjusted, taking the trade-off between power maximization and load minimization...

  17. Fault Detection and Load Distribution for the Wind Farm Challenge

    DEFF Research Database (Denmark)

    Borchersen, Anders Bech; Larsen, Jesper Abildgaard; Stoustrup, Jakob

    2014-01-01

    In this paper a fault detection system and a fault tolerant controller for a wind farm model is designed and tested. The wind farm model is taken from the wind farm challenge which is a public available challenge where a wind farm consisting of nine turbines is proposed. The goal of the challenge...

  18. An Optimization Framework for Load and Power Distribution in Wind Farms

    DEFF Research Database (Denmark)

    Soleimanzadeh, Maryam; Wisniewski, Rafal; Kanev, Stoyan

    2012-01-01

    by a system operator. Moreover, the reference signals are determined to reduce the load acting on wind turbines at low frequencies. Therefore, a trade-off is made for load and power control, which is formulated as an optimization problem. Afterwards, the optimization problem for the wind farm modeled...

  19. Minimum Thrust Load Control for Floating Wind Turbine

    DEFF Research Database (Denmark)

    Christiansen, Søren; Bak, Thomas; Knudsen, Torben

    2012-01-01

    — Offshore wind energy capitalizes on the higher and less turbulent wind at sea. Shallow water sites are profitable for deployment of monopile wind turbines at water depths of up to 30 meters. Beyond 30 meters, the wind is even stronger and less turbulent. At these depths, floating wind turbines...... become profitable, capable of accessing unexploited wind resources while reaching regions of new consumers. However, floating wind turbines are subject to reduced structural stiffness which results in instabilities when standard wind turbine control systems are applied. Based on optimal control, this paper...... presents a new minimum thrust control strategy capable of stabilizing a floating wind turbine. The new control strategy explores the freedom of variable generator speed above rated wind speed. A comparison to the traditional constant speed strategy, shows improvements in structural fore-aft oscillations...

  20. Loads on Entrance Platforms for Offshore Wind Turbines

    DEFF Research Database (Denmark)

    Frigaard, Peter; Andersen, Thomas Lykke; Ramirez, Jorge Robert Rodriguez

    2010-01-01

    The present paper gives an overview of the performed large scale tests in GWK, Hannover for studying wave run-up generated forces on wind turbine entrance platforms. The run-up height and velocity was measured by use of high speed video recordings supplemented by some wave gauges mounted at the p......The present paper gives an overview of the performed large scale tests in GWK, Hannover for studying wave run-up generated forces on wind turbine entrance platforms. The run-up height and velocity was measured by use of high speed video recordings supplemented by some wave gauges mounted...... at the pile. Hereafter, the run-up generated impact forces were measured on two types of grates and a solid plate. The pressure distribution was also measured for the solid plate. In addition to this the wave generated backfilling of an initial scour hole and the strength of the backfilling soil was studied....... The purpose of all the tests was to study scale effects related to the above items by comparison with small scale tests and also to present new guidelines for design....

  1. Wind Tunnel Measurements at Virginia Tech

    DEFF Research Database (Denmark)

    Fischer, Andreas; Bertagnolio, Franck

    2012-01-01

    In this section, the wind tunnel configuration used for aerodynamic and aeroacoustic measurement is described. Then, the validation of the method for evaluating far-field noise from surface microphones as described in Section 5 is presented. Finally, the design concept proposed in Section 6 is ve...

  2. Wind Speed Measurement by Paper Anemometer

    Science.gov (United States)

    Zhong, Juhua; Cheng, Zhongqi; Guan, Wenchuan

    2011-01-01

    A simple wind speed measurement device, a paper anemometer, is fabricated based on the theory of standing waves. In providing the working profile of the paper anemometer, an experimental device is established, which consists of an anemometer sensor, a sound sensor, a microphone, paper strips, a paper cup, and sonic acquisition software. It shows…

  3. Assessment of the Uniqueness of Wind Tunnel Strain-Gage Balance Load Predictions

    Science.gov (United States)

    Ulbrich, N.

    2016-01-01

    A new test was developed to assess the uniqueness of wind tunnel strain-gage balance load predictions that are obtained from regression models of calibration data. The test helps balance users to gain confidence in load predictions of non-traditional balance designs. It also makes it possible to better evaluate load predictions of traditional balances that are not used as originally intended. The test works for both the Iterative and Non-Iterative Methods that are used in the aerospace testing community for the prediction of balance loads. It is based on the hypothesis that the total number of independently applied balance load components must always match the total number of independently measured bridge outputs or bridge output combinations. This hypothesis is supported by a control volume analysis of the inputs and outputs of a strain-gage balance. It is concluded from the control volume analysis that the loads and bridge outputs of a balance calibration data set must separately be tested for linear independence because it cannot always be guaranteed that a linearly independent load component set will result in linearly independent bridge output measurements. Simple linear math models for the loads and bridge outputs in combination with the variance inflation factor are used to test for linear independence. A highly unique and reversible mapping between the applied load component set and the measured bridge output set is guaranteed to exist if the maximum variance inflation factor of both sets is less than the literature recommended threshold of five. Data from the calibration of a six{component force balance is used to illustrate the application of the new test to real-world data.

  4. Automatic Multimodal Cognitive Load Measurement (AMCLM)

    Science.gov (United States)

    2011-06-01

    increasing, while F2 is decreasing, as cognitive load is increased. Classification results performed on the Stroop test database show that formant...Final Project Report Grant AOARD-10-4029 Automatic Multimodal Cognitive Load Measurement (AMCLM) June 2011 NICTA DSIM Team...past year. At the start of the project, we carried out a literature review on video based physiological measures of cognitive load, focusing on

  5. On Small-Signal Stability of Wind Power System with Full-Load Converter Interfaced Wind Turbines

    OpenAIRE

    Knüppel, Thyge; Akhmatov, Vladislav; Nielsen, Jørgen Nygård; Jensen, Kim H.; Dixon, Andrew; Østergaard, Jacob

    2010-01-01

    Small-signal stability analysis of power system oscillations is a well established field within power system analysis, but not much attention has yet been paid to systems with a high penetration of wind turbines and with large wind power plants. In this paper an analysis is presented which assess the impact of full-load converter interfaced wind turbines on power system small-signal stability. The study is based on a 7 generator network with lightly damped inter-area modes. A detailed wind tu...

  6. A Wind Power and Load Prediction Based Frequency Control Approach for Wind-Diesel-Battery Hybrid Power System

    Directory of Open Access Journals (Sweden)

    Chao Peng

    2015-01-01

    Full Text Available A frequency control approach based on wind power and load power prediction information is proposed for wind-diesel-battery hybrid power system (WDBHPS. To maintain the frequency stability by wind power and diesel generation as much as possible, a fuzzy control theory based wind and diesel power control module is designed according to wind power and load prediction information. To compensate frequency fluctuation in real time and enhance system disturbance rejection ability, a battery energy storage system real-time control module is designed based on ADRC (active disturbance rejection control. The simulation experiment results demonstrate that the proposed approach has a better disturbance rejection ability and frequency control performance compared with the traditional droop control approach.

  7. CFD-based design load analysis of 5MW offshore wind turbine

    Science.gov (United States)

    Tran, T. T.; Ryu, G. J.; Kim, Y. H.; Kim, D. H.

    2012-11-01

    The structure and aerodynamic loads acting on NREL 5MW reference wind turbine blade are calculated and analyzed based on advanced Computational Fluid Dynamics (CFD) and unsteady Blade Element Momentum (BEM). A detailed examination of the six force components has been carried out (three force components and three moment components). Structure load (gravity and inertia load) and aerodynamic load have been obtained by additional structural calculations (CFD or BEM, respectively,). In CFD method, the Reynolds Average Navier-Stokes approach was applied to solve the continuity equation of mass conservation and momentum balance so that the complex flow around wind turbines was modeled. Written in C programming language, a User Defined Function (UDF) code which defines transient velocity profile according to the Extreme Operating Gust condition was compiled into commercial FLUENT package. Furthermore, the unsteady BEM with 3D stall model has also adopted to investigate load components on wind turbine rotor. The present study introduces a comparison between advanced CFD and unsteady BEM for determining load on wind turbine rotor. Results indicate that there are good agreements between both present methods. It is importantly shown that six load components on wind turbine rotor is significant effect under Extreme Operating Gust (EOG) condition. Using advanced CFD and additional structural calculations, this study has succeeded to construct accuracy numerical methodology to estimate total load of wind turbine that compose of aerodynamic load and structure load.

  8. Model Based Open-Loop Wind Farm Control Using Active Power for Power Increase and Load Reduction

    OpenAIRE

    Hyungyu Kim; Kwansu Kim; Insu Paek

    2017-01-01

    A new wind farm control algorithm that adjusts the power output of the most upstream wind turbine in a wind farm for power increase and load reduction was developed in this study. The algorithm finds power commands to individual wind turbines to maximize the total power output from the wind farm when the power command from the transmission system operator is larger than the total available power from the wind farm. To validate this wind farm control algorithm, a relatively high fidelity wind ...

  9. Numerical Investigation of Aerodynamic Performance and Loads of a Novel Dual Rotor Wind Turbine

    Directory of Open Access Journals (Sweden)

    Behnam Moghadassian

    2016-07-01

    Full Text Available The objective of this paper is to numerically investigate the effects of the atmospheric boundary layer on the aerodynamic performance and loads of a novel dual-rotor wind turbine (DRWT. Large eddy simulations are carried out with the turbines operating in the atmospheric boundary layer (ABL and in a uniform inflow. Two stability conditions corresponding to neutral and slightly stable atmospheres are investigated. The turbines are modeled using the actuator line method where the rotor blades are modeled as body forces. Comparisons are drawn between the DRWT and a comparable conventional single-rotor wind turbine (SRWT to assess changes in aerodynamic efficiency and loads, as well as wake mixing and momentum and kinetic energy entrainment into the turbine wake layer. The results show that the DRWT improves isolated turbine aerodynamic performance by about 5%–6%. The DRWT also enhances turbulent axial momentum entrainment by about 3.3 %. The highest entrainment is observed in the neutral stability case when the turbulence in the ABL is moderately high. Aerodynamic loads for the DRWT, measured as out-of-plane blade root bending moment, are marginally reduced. Spectral analyses of ABL cases show peaks in unsteady loads at the rotor passing frequency and its harmonics for both rotors of the DRWT.

  10. Exercise Load Measurement Insole (ELMI) Project

    Data.gov (United States)

    National Aeronautics and Space Administration — The Exercise Load Measurement Insole (ELMI) is a system that is designed to measure normal and shear foot forces during exercise. The ELMI system is lightweight,...

  11. IDENTIFICATION OF WIND LOAD APPLIED TO THREE-DIMENSIONAL STRUCTURES BY VIRTUE OF ITS SIMULATION IN THE WIND TUNNEL

    Directory of Open Access Journals (Sweden)

    Doroshenko Sergey Aleksandrovich

    2012-10-01

    Full Text Available The authors discuss wind loads applied to a set of two buildings. The wind load is simulated with the help of the wind tunnel. In the Russian Federation, special attention is driven to the aerodynamics of high-rise buildings and structures. According to the Russian norms, identification of aerodynamic coefficients for high-rise buildings, as well as the influence of adjacent buildings and structures, is performed on the basis of models of structures exposed to wind impacts simulated in the wind tunnel. This article deals with the results of the wind tunnel test of buildings. The simulation was carried out with the involvement of a model of two twenty-three storied buildings. The experiment was held in a wind tunnel of the closed type at in the Institute of Mechanics of Moscow State University. Data were compared at the zero speed before and after the experiment. LabView software was used to process the output data. Graphs and tables were developed in the Microsoft Excel package. GoogleSketchUp software was used as a visualization tool. The three-dimensional flow formed in the wind tunnel can't be adequately described by solving the two-dimensional problem. The aerodynamic experiment technique is used to analyze the results for eighteen angles of the wind attack.

  12. Measurements of UWB Pulse Propagation Along a Wind Turbine Blade at 1 to 20 GHz

    DEFF Research Database (Denmark)

    Hejselbæk, Johannes; Syrytsin, Igor A.; Eggers, Patrick Claus F.

    2018-01-01

    This paper describes propagation measurements of an Ultra Wide Band (UWB) pulse along a full-scale wind turbine blade. The aim is to use the UWB channel characteristics to determine the deflection of the wind turbine blade under different wind loads. The frequency response is measured from 1 to 20...... the reflection originates a ray-tracing study incorporating a model of the curvature of the blade have been conducted. This showed the area causing the reflections depended highly on the placement of the antenna on the wind turbine blade....

  13. Wind atlas for South Africa: wind measurements and micro-scale modelling

    CSIR Research Space (South Africa)

    Szewczuk, S

    2010-08-01

    Full Text Available . This paper will discuss the wind atlas method, provide an overview of the wind resource in South Africa, wind measurements that are being undertaken as well as the micro-scale modelling that is planned to be done as part of the Wind Atlas for South Africa...

  14. Calculation of PVC windows for wind loads in high-rise buildings

    Science.gov (United States)

    Konstantinov, Aleksandr; Lambias Ratnayake, Maya

    2018-03-01

    In the following article we examine problems faced when designing PVC windows for high-rise buildings, which are usually not considered when constructing objects for massive sites, using a high-rise residential complex as an example. We address the matters related to wind loads on windows & statistical calculation of the impact of wind loads on them. We have presented variants of installing load-bearing elements of PVC windows which accept wind loads. We conducted a laboratory experiment by simulating wind loads on the window design, which is actually used for glazing the examined high-rise building. In the course of the experiment we determined additional factors which need to be considered when constructing PVC window structures for glazing high-rise buildings. We can determine that the following calculation method for the impact of wind load on PVC windows gives higher values of the desired statistical characteristics of load-bearing elements of a window compared to the results of laboratory experiments. We provide prerequisites to improve the analytical method of calculating impact of wind loads on load-bearing elements of PVC windows.

  15. Comparison of Speed-Up Over Hills Derived from Wind-Tunnel Experiments, Wind-Loading Standards, and Numerical Modelling

    Science.gov (United States)

    Safaei Pirooz, Amir A.; Flay, Richard G. J.

    2018-03-01

    We evaluate the accuracy of the speed-up provided in several wind-loading standards by comparison with wind-tunnel measurements and numerical predictions, which are carried out at a nominal scale of 1:500 and full-scale, respectively. Airflow over two- and three-dimensional bell-shaped hills is numerically modelled using the Reynolds-averaged Navier-Stokes method with a pressure-driven atmospheric boundary layer and three different turbulence models. Investigated in detail are the effects of grid size on the speed-up and flow separation, as well as the resulting uncertainties in the numerical simulations. Good agreement is obtained between the numerical prediction of speed-up, as well as the wake region size and location, with that according to large-eddy simulations and the wind-tunnel results. The numerical results demonstrate the ability to predict the airflow over a hill with good accuracy with considerably less computational time than for large-eddy simulation. Numerical simulations for a three-dimensional hill show that the speed-up and the wake region decrease significantly when compared with the flow over two-dimensional hills due to the secondary flow around three-dimensional hills. Different hill slopes and shapes are simulated numerically to investigate the effect of hill profile on the speed-up. In comparison with more peaked hill crests, flat-topped hills have a lower speed-up at the crest up to heights of about half the hill height, for which none of the standards gives entirely satisfactory values of speed-up. Overall, the latest versions of the National Building Code of Canada and the Australian and New Zealand Standard give the best predictions of wind speed over isolated hills.

  16. Measurements on Container Load Trailer

    DEFF Research Database (Denmark)

    Brincker, Rune; Hansen, Lars Pilegaard

    This report describes a series of measurements carried out for Danish Camp Supply (DCS), Nørre Sundby, Denmark during January and February 1990. The test series was departed into three sessions: the first pilot measurement session made on Friday 26. of January, the second pilot measurement made o...

  17. Tower Design Load Verification on a 1-kW Wind Turbine: Preprint

    Energy Technology Data Exchange (ETDEWEB)

    Prascher, D.; Huskey, A.

    2004-11-01

    Wind turbine testing at the National Wind Technology Center (NWTC) has been done to characterize both tower top loads and thrust loads for small wind turbines, which is part of an ongoing effort to model and predict small wind turbine behavior and the resulting stresses imposed on the supporting tower. To these ends, a 1-kW furling wind turbine mounted on a 10-meter tower was instrumented and monitored via a data acquisition system for nearly a year. This test was conducted to verify the design loads as predicted by the simple design equations provided in the draft revision of the International Electrotechnical Commission (IEC) Small Wind Turbine Safety Standard 61400-02 CDV (hereafter called ''the draft Standard''). Data were captured for several operating conditions covered by the draft Standard. This paper addresses the collected data and what conclusions can be made from it.

  18. Fatigue Load Sensitivity Based Optimal Active Power Dispatch For Wind Farms

    DEFF Research Database (Denmark)

    Zhao, Haoran; Wu, Qiuwei; Huang, Shaojun

    2017-01-01

    sensitivity are derived, which significantly improves the computation efficiency of the local WT controller. The proposed algorithm can be implemented in different active power control schemes. Case studies were conducted with a wind farm under balance control for both low and high wind conditions......This paper proposes an optimal active power dispatch algorithm for wind farms based on Wind Turbine (WT) load sensitivity. The control objectives include tracking power references from the system operator and minimizing fatigue loads experienced by WTs. The sensitivity of WT fatigue loads to power...... references is defined which simplifies the formulation of the optimal power dispatch problem. Since the sensitivity value is calculated at the local WT controller, the computation burden of the central wind farm controller is largely reduced. Moreover, explicit analytical equations of the fatigue load...

  19. Probabilistic model for multi-axial load combinations for wind turbines

    DEFF Research Database (Denmark)

    Dimitrov, Nikolay Krasimirov

    2016-01-01

    The article presents a model describing the joint probability distribution of multiple load components acting on a wind turbine blade cross section. The problem of modelling the probability distribution of load time histories with large periodic components is addressed by dividing the signal...... for determining contemporaneous loads. Using examples with simulated loads on a 10 MW wind turbine,the behavior of the bending moments acting on a blade section is illustrated under different conditions.The loading direction most critical for material failure is determined using a finite-element model...... of the blade cross section on which load combinations with different directions but with equal probability are applied. By defining a joint probability distribution and return-period contours for multiple load components,the suggested procedure is applicable to different aspects of the design of wind turbine...

  20. A zero torsional stiffness twist morphing blade as a wind turbine load alleviation device

    International Nuclear Information System (INIS)

    Lachenal, X; Daynes, S; Weaver, P M

    2013-01-01

    This paper presents the design, analysis and realization of a zero stiffness twist morphing wind turbine blade. The morphing blade is designed to actively twist as a means of alleviating the gust loads which reduce the fatigue life of wind turbine blades. The morphing structure exploits an elastic strain energy balance within the blade to enable large twisting deformations with modest actuation requirements. While twist is introduced using the warping of the blade skin, internal pre-stressed members ensure that a constant strain energy balance is achieved throughout the deformation, resulting in a zero torsional stiffness structure. The torsional stability of the morphing blade is characterized by analysing the elastic strain energy in the device. Analytical models of the skin, the pre-stressed components and the complete blade are compared to their respective finite element models as well as experimental results. The load alleviation potential of the adaptive structure is quantified using a two-dimensional steady flow aerodynamic model which is experimentally validated with wind tunnel measurements. (paper)

  1. Full two-dimensional rotor plane inflow measurements by a spinner-integrated wind lidar

    OpenAIRE

    Sjöholm, Mikael; Pedersen, Anders Tegtmeier; Angelou, Nikolas; Foroughi Abari, Farzad; Mikkelsen, Torben; Harris, Michael; Slinger, Chris; Kapp, Stefan

    2013-01-01

    IntroductionWind turbine load reduction and power performance optimization via advanced control strategies is an active area in the wind energy community. In particular, feed-forward control using upwind inflow measurements by lidar (light detection and ranging) remote sensing instruments has attracted an increasing interest during the last couple of years. So far, the reported inflow measurements have been along a few measurement directions or at most on a circle in front of the turbine, whi...

  2. Use of the WEST-1 wind turbine simulator to predict blade fatigue load distribution

    Science.gov (United States)

    Janetzke, D. C.

    1983-01-01

    To test the ability of WEST-1 to predict blade fatigue load distribution, actual wind signals were fed into the simulator and the response data were recorded and processed in the same manner as actual wind turbine data. The WEST-1 simulator was operated in a stable, unattended mode for six hours. The probability distribution of the cyclic flatwise bending moment for the blade was comparable to that for an actual wind turbine in winds with low turbulence. The input from a stationary anemometer was found to be inadequate for use in the prediction of fatigue load distribution for blade design purposes and modifications are necessary.

  3. Coordination of Voltage and Frequency Feedback in Load-Frequency Control Capability of Wind Turbine

    DEFF Research Database (Denmark)

    Hoseinzadeh, Bakhtyar; Silva, Filipe Faria Da; Bak, Claus Leth

    2014-01-01

    , sufficient reserve capacity should be procured. This paper addresses the Load-Frequency Control (LFC) scheme offered by VSWT. Feedback loop of locally measured voltage and frequency data is employed to improve transient and permanent response to achieve faster and more efficient LFC action and voltage...... regulation. The proposed scheme demonstrates remarkable improvement transient state of both voltage and frequency profiles in comparison with conventional LFC designs provided by Central Power Plants (CPP) or Wind Power Plants (WPP). Numerical simulations carried out in DigSilent Power- Factory confirm...

  4. Representivity of wind measurements for design wind speed estimations

    CSIR Research Space (South Africa)

    Goliger, Adam M

    2013-07-01

    Full Text Available Engineer in South Africa, January 1987. Wever, N., and G. Groen. 2009. Improving potential wind for extreme wind statistics. KNMI scientific report - wetenschappelijk rapport : WR 2009-02. KNMI. De Bilt. The Netherlands. 114 pp. Wieringa, J. 1986...

  5. ACCUWIND - Accurate wind speed measurements in wind energy - Summary report

    DEFF Research Database (Denmark)

    Friis Pedersen, Troels; Dahlberg, J.-Å.; Cuerva, A.

    2006-01-01

    been used by meteorologists for turbulencemeasurements, but have also found a role on wind turbine nacelles for wind speed and yaw control purposes. The report on cup and sonic anemometry deals with establishment of robustness in assessment and classification by focus on methods and proceduresfor...

  6. Modeling of quasi-static thrust load of wind turbines based on 1 s SCADA data

    Directory of Open Access Journals (Sweden)

    N. Noppe

    2018-03-01

    Full Text Available A reliable load history is crucial for a fatigue assessment of wind turbines. However, installing strain sensors on every wind turbine is not economically feasible. In this paper, a technique is proposed to reconstruct the thrust load history of a wind turbine based on high-frequency Supervisory Control and Data Acquisition (SCADA data. Strain measurements recorded during a short period of time are used to train a neural network. The selection of appropriate input parameters is performed based on Pearson correlation and mutual information. Once the training is done, the model can be used to predict the thrust load based on SCADA data only. The technique is validated on two different datasets, one consisting of simulation data (using the software FAST v8, created by Jonkman and Jonkman, 2016 obtained in a controllable environment and one consisting of measurements taken at an offshore wind turbine. In general, the relative error between simulated or measured and predicted thrust load barely exceeds 15 % during normal operation.

  7. Harmonic Propagation and Interaction Evaluation between Small-Scale Wind Farms and Nonlinear Loads

    Directory of Open Access Journals (Sweden)

    Cheng-Xiong Mao

    2013-07-01

    Full Text Available Distributed generation is a flexible and effective way to utilize renewable energy. The dispersed generators are quite close to the load, and pose some power quality problems such as harmonic current emissions. This paper focuses on the harmonic propagation and interaction between a small-scale wind farm and nonlinear loads in the distribution grid. Firstly, by setting the wind turbines as P – Q(V nodes, the paper discusses the expanding Newton-Raphson power flow method for the wind farm. Then the generalized gamma mixture models are proposed to study the non-characteristic harmonic propagation of the wind farm, which are based on Gaussian mixture models, improved phasor clustering and generalized Gamma models. After the integration of the small-scale wind farm, harmonic emissions of nonlinear loads will become random and fluctuating due to the non-stationary wind power. Furthermore, in this paper the harmonic coupled admittance matrix model of nonlinear loads combined with a wind farm is deduced by rigorous formulas. Then the harmonic propagation and interaction between a real wind farm and nonlinear loads are analyzed by the harmonic coupled admittance matrix and generalized gamma mixture models. Finally, the proposed models and methods are verified through the corresponding simulation models in MATLAB/SIMULINK and PSCAD/EMTDC.

  8. How do fungi measure wind speed?

    Science.gov (United States)

    Roper, Marcus; Tomasek, Michael; Lin, Yuxi; Dressaire, Emilie

    2017-11-01

    For successful dispersal, a fungus must push its spores through the boundary layer of nearly still air that clings to it. Some spores pass through this boundary layer by being forcibly ejected. But many spores and fungi have no mechanism for active ejection, and must be carried away passively by the wind. To facilitate dispersal, the spores are borne on the top of aerial structures. Regulating the height of these aerial structures is an engineering challenge; too long and the structures will collapse under their own weight; too short, and they may not reach high enough to cross the boundary layer. A fungus therefore benefits by knowing the wind speed (and therefore the boundary layer thickness). How does it make this measurement? I will show that the model filamentous fungus Neurospora crassa uses water evaporation rate to accurately measure wind speed. In addition to showing that fungi control and optimize even passive mechanisms for dispersal, our findings highlight the importance of physical conditions in controlling fungal growth and behavior.

  9. Estimation of Seismic Load Demand for a Wind Turbine in the Time Domain: Preprint

    Energy Technology Data Exchange (ETDEWEB)

    Prowell, I.; Elgamal, A.; Uang, C.; Jonkman, J.

    2010-03-01

    Turbines installed in seismically active regions such as the Pacific Rim or the Mediterranean must consider loads induced by base shaking from an earthquake. To account for this earthquake risk, current International Electrotechnical Commission (IEC) certification requirements provide a simplified method for calculating seismic loads which is intended to be conservative. Through the addition of capabilities, it is now possible to simulate earthquake loading of a wind turbine in conjunction other load sources such as wind and control system behavior using the FAST code. This paper presents a comparison of three earthquake loading scenarios of the National Renewable Energy Laboratory (NREL) offshore 5-MW baseline wind turbine: idling; continued operation through an earthquake; and an emergency shutdown initiated by an earthquake. Using a set of 22 earthquake records, simulations are conducted for each load case. A summary of the resulting tower moment demand is presented to assess the influence of operational state on the resulting structural demand.

  10. Ultimate Strength of Wind Turbine Blades under Multiaxial Loading

    DEFF Research Database (Denmark)

    Haselbach, Philipp Ulrich

    Modern wind turbine rotor blades are sophisticated lightweight structures, optimised towards achieving the best compromise between aerodynamic and structural design as well as a cost efficient manufacturing processes. They are usually designed for a lifetime of minimum 20 years, where they must...... endure a variety of weather conditions including uncontrollable, extreme winds without developing damage and fracture. The trend in the development of wind turbines is towards larger, more efficient wind turbines, placed offshore, where access is difficult and repairs costly. In consequence, failures...

  11. CTE Measurements for Loading Scenarios

    Energy Technology Data Exchange (ETDEWEB)

    Allen, Nicholas Charles [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

    2016-04-16

    The goals are to 1. understand full field thermal expansion of system parts by using strain gauges, DIC, and possibly ESPI. This is ultimately used to update a Finite Element Model relating to stockpile stewardship. 2. To verify the resolution of digital image correlation methods for thermal expansion measurements (CTE). A few conclusions: To this point, the DIC data shows more noise (less resolution) than we would like and Strain Gauge data is sound but it is more localized than full field.

  12. Results of Sexbierum Wind Farm: single wake measurements

    NARCIS (Netherlands)

    Cleijne, J.W.

    1993-01-01

    In the framework of the JOULE-0064 'Full-scale Measurements in Wind Turbine Arrays' in the period between June-November 1992 measurements have been performed in the Sexbierum Wind Farm. The aim of the measurements is to provide data for the validation of wake and wind farm models, which are being

  13. Offshore wind resources at Danish measurement sites

    Energy Technology Data Exchange (ETDEWEB)

    Barthelmie, R.J.; Courtney, M.S.; Lange, B.; Nielsen, M.; Sempreviva, A.M. [Risoe National Lab., Dept. of Wind Energy and Atmospheric Physics, Roskilde (Denmark); Svenson, J.; Olsen, F. [SEAS, Haslev (Denmark); Christensen, T. [Elsamprojekt, Fredericia (Denmark)

    1999-03-01

    In order to characterise wind and turbulence characteristics at prospective offshore wind energy sites, meteorological observations from a number of purpose-built offshore monitoring sites have been analyzed and compared with long wind speed time series. New analyses have been conducted on the data sets focussing on meteorology, turbulence, extreme winds and wind and wave interactions. Relationships between wind speed, turbulence and fetch are highly complex. Minimum turbulence intensity offshore is associated with wind speeds of about 12 m/s. At lower wind speeds, stability effects are important while at higher winds speeds wind and wave interactions appear to dominate. On average, turbulence intensity offshore at 48 m height is approximately 0.08 if no coastal effects are present. However, the effect of the coastal discontinuity persists in wind speed and turbulence characteristics for considerable distances offshore. The majority of the adjustment of appears to occur within 20 km of the coast. (au)

  14. Behavior of a nuclear power plant ventilation stack for wind loads

    International Nuclear Information System (INIS)

    Venkatachalapathy, V.

    2012-01-01

    This paper describes behavior of self supporting tall reinforced concrete (RC) ventilation stack of a nuclear power plant (NPP) for wind loads. Since the static and equivalent dynamic wind loads are inter-dependant on overall size of the stack, proper sizing of the stack geometry is important for reducing wind loads. The present study investigated the influence of engineered backfill soil on lateral response of ventilation stack. Ignoring backfill soil stiffness up to ground height does not allow to predict actual critical wind velocity causing across wind oscillation. The results show that proposed modification in the stack geometry modeled using 2D beam-spring elements is economical than that of single tapered geometry. Shaft diameter reduced in the proposed geometry indicates that there is a scope for overall space savings in the NPP layout. (author)

  15. Application genetic algorithms for load management in refrigerated warehouses with wind power penetration

    DEFF Research Database (Denmark)

    Zong, Yi; Cronin, Tom; Gehrke, Oliver

    2009-01-01

    Wind energy is produced at random times, whereas the energy consumption pattern shows distinct demand peaks during day-time and low levels during the night. The use of a refrigerated warehouse as a giant battery for wind energy is a new possibility that is being studied for wind energy integration...... as well as a way to store electricity produced during night-time by wind turbines. The controller for load management in a refrigerated warehouse with wind power penetration by GA-based is introduced in this paper. The objective function is to minimize the energy consumption for operating the refrigerated...... warehouse. It can be seen that the GA-based control strategy achieves feasible results for operating the temperature in refrigerated warehouse. Balancing the wind power production with refrigerated warehouse load management promises to be a clean and cost effective method. For refrigerated warehouse owners...

  16. Evaluation of MOSTAS computer code for predicting dynamic loads in two bladed wind turbines

    Science.gov (United States)

    Kaza, K. R. V.; Janetzke, D. C.; Sullivan, T. L.

    1979-01-01

    Calculated dynamic blade loads were compared with measured loads over a range of yaw stiffnesses of the DOE/NASA Mod-O wind turbine to evaluate the performance of two versions of the MOSTAS computer code. The first version uses a time-averaged coefficient approximation in conjunction with a multi-blade coordinate transformation for two bladed rotors to solve the equations of motion by standard eigenanalysis. The second version accounts for periodic coefficients while solving the equations by a time history integration. A hypothetical three-degree of freedom dynamic model was investigated. The exact equations of motion of this model were solved using the Floquet-Lipunov method. The equations with time-averaged coefficients were solved by standard eigenanalysis.

  17. Turbulence and turbulence-generated structural loading in wind turbine clusters

    Energy Technology Data Exchange (ETDEWEB)

    Frandsen, Sten

    2007-01-15

    Turbulence, in terms of standard deviation of wind speed fluctuations, and other flow characteristics are different in the interior of wind farms relative to the free flow and action must be taken to ensure sufficient structural sustainability of the wind turbines exposed to 'wind farm flow'. The standard deviation of wind speed fluctuations is a known key parameter for both extreme- and fatigue loading, and it is argued and found to be justified that a model for change in turbulence intensity alone may account for increased fatigue loading in wind farms. Changes in scale of turbulence and horizontal flow-shear also influence the dynamic response and thus fatigue loading. However, these parameters are typically negatively or positively correlated with the standard deviation of wind speed fluctuations, which therefore can, if need be, represent these other variables. Thus, models for spatially averaged turbulence intensity inside the wind farm and direct-wake turbulence intensity are being devised and a method to combine the different load situations is proposed. The combination of the load cases implies a weighting method involving the slope of the considered material's Woehler curve. In the context, this is novel and necessary to avoid excessive safety for fatigue estimation of the structure's steel components, and non-conservatism for fibreglass components. The proposed model offers significant reductions in computational efforts in the design process. The status for the implementation of the model is that it became part of the Danish standard for wind turbine design DS 472 (2001) in August 2001 and it is part of the corresponding international standard, IEC61400-1 (2005). Also, extreme loading under normal operation for wake conditions and the efficiency of very large wind farms are discussed. (au)

  18. 3D WindScanner lidar measurements of wind and turbulence around wind turbines, buildings and bridges

    DEFF Research Database (Denmark)

    Mikkelsen, Torben Krogh; Sjöholm, Mikael; Angelou, Nikolas

    2017-01-01

    WindScanner is a distributed research infrastructure developed at DTU with the participation of a number of European countries. The research infrastructure consists of a mobile technically advanced facility for remote measurement of wind and turbulence in 3D. The WindScanners provide coordinated ...

  19. Performance Analysis of Doubly Fed Induction Generator Based Wind turbine under Faulty and RLC Load Conditions

    OpenAIRE

    Rekha Parashar; Shashikant

    2015-01-01

    This paper presents the performance of Doubly Fed Induction Generator based wind turbine system during different types of grid fault. The doubly fed induction generator (DFIG) based wind turbine (WT) system provides better power delivery towards the demand. The design and response of the DFIG based wind turbine system during different fault conditions, various load conditions and integrated system consisting of DFIG based WT system have been verified using MATLAB/ Simulink. The simulation re...

  20. Reducing Wind Turbine Load Simulation Uncertainties by Means of a Constrained Gaussian Turbulence Field

    DEFF Research Database (Denmark)

    Dimitrov, Nikolay Krasimirov; Lazarov, Boyan Stefanov

    2015-01-01

    . A numerical study shows the application of the constrained turbulence method to load simulations on a 10MW wind turbine model, using two example lidar patterns – a 5-point pattern forming a square with a central point, and a circular one. Based on the results of this study, we assess the influence of applying...... the proposed method on the statistical uncertainty in wind turbine extreme and fatigue loads....

  1. The design of models for cryogenic wind tunnels. [mechanical properties and loads

    Science.gov (United States)

    Gillespie, V. P.

    1977-01-01

    Factors to be considered in the design and fabrication of models for cryogenic wind tunnels include high model loads imposed by the high operating pressures, the mechanical and thermodynamic properties of materials in low temperature environments, and the combination of aerodynamic loads with the thermal environment. Candidate materials are being investigated to establish criteria for cryogenic wind tunnel models and their installation. Data acquired from these tests will be provided to users of the National Transonic Facility.

  2. Wind loads for stability design of large multi-span duo-pitch greenhouses

    NARCIS (Netherlands)

    Bronkhorst, A.J.; Geurts, C.P.W.; Bentum, C.A. van; Knaap, L.P.M. van der; Pertermann, I.

    2017-01-01

    An atmospheric boundary layer wind tunnel study was performed to determine the overall horizontal wind load on multi-span duo-pitch greenhouses. The results of this study are intended for the stability design of inflexible Gladding system greenhouses (designated as Class A in EN 13031-1) with roof

  3. A simplified model predicting the weight of the load carrying beam in a wind turbine blade

    DEFF Research Database (Denmark)

    Mikkelsen, Lars Pilgaard

    2016-01-01

    Based on a simplified beam model, the loads, stresses and deflections experienced by a wind turbine blade of a given length is estimated. Due to the simplicity of the model used, the model is well suited for work investigating scaling effects of wind turbine blades. Presently, the model is used t...

  4. Assessment of the impact of frequency support on DFIG wind turbine loads

    DEFF Research Database (Denmark)

    Barahona Garzón, Braulio; You, Rui; Hansen, Anca Daniela

    2013-01-01

    This study presents models and tools for the assessment of the impact that providing frequency support has on doubly-fed generator (DFIG) wind turbine structural loads and drive train. The focus is on primary frequency support, aiming at quantifying the impact on wind turbines acting as frequency...

  5. Effect of blade flutter and electrical loading on small wind turbine noise

    Science.gov (United States)

    The effect of blade flutter and electrical loading on the noise level of two different size wind turbines was investigated at the Conservation and Production Research Laboratory (CPRL) near Bushland, TX. Noise and performance data were collected on two blade designs tested on a wind turbine rated a...

  6. Mechanical Loads Test Report for the U.S. Department of Energy 1.5-Megawatt Wind Turbine

    Energy Technology Data Exchange (ETDEWEB)

    Santos, Rick [Santos Wind Engineering Technologies, Inc., Portland, ME (United States); van Dam, Jeroen [National Renewable Energy Laboratory (NREL), Golden, CO (United States)

    2015-07-16

    The objective of the test was to obtain a baseline characterization of the mechanical loads of the DOE 1.5 wind turbine located at NREL. The test was conducted in accordance with the International Electrotechnical Commission (IEC) Technical Specification, IEC 61400-13 Wind Turbine Generator Systems – Part 13: Measurement of mechanical loads; First Edition 2001-06 [1]. The National Wind Technology Center (NWTC) at NREL conducted this test in accordance with its quality system procedures so that the final test report meets the full requirements of its accreditation by the American Association for Laboratory Accreditation (A2LA). NREL’s quality system requires that all applicable requirements specified by A2LA and International Standards Organization/IEC 17025 be met or to note any exceptions in the test report.

  7. Rotor equivalent wind speed for power curve measurement – comparative exercise for IEA Wind Annex 32

    DEFF Research Database (Denmark)

    Wagner, Rozenn; Cañadillas, B.; Clifton, A.

    2014-01-01

    A comparative exercise has been organised within the International Energy Agency (IEA) Wind Annex 32 in order to test the Rotor Equivalent Wind Speed (REWS) method under various conditions of wind shear and measurement techniques. Eight organisations from five countries participated in the exercise....... Each member of the group has derived both the power curve based on the wind speed at hub height and the power curve based on the REWS. This yielded results for different wind turbines, located in diverse types of terrain and where the wind speed profile was measured with different instruments (mast...... was the definition of the segment area used as weighting for the wind speeds measured at the various heights in the calculation of the REWS. This comparative exercise showed that the REWS method results in a significant difference compared to the standard method using the wind speed at hub height in conditions...

  8. Analysis of Anholt offshore wind farm SCADA measurements

    DEFF Research Database (Denmark)

    Hansen, Kurt Schaldemose; Volker, Patrick; Pena Diaz, Alfredo

    SCADA measurements from the Danish Anholt offshore wind farm (ANH) for a period of 2½ years have been qualified. ANH covers 12 km × 22 km and is located between Djursland and the island Anholt in Kattegat, Denmark. This qualification encompasses identification of curtailment and idling periods......, start/stop events and a power curve control for each wind turbine in the wind farm. Data also include wind speed measurements from a nearby WindCube lidar and simulations from the WRF model for the same period as the SCADA. An equivalent wind speed (wsi) is derived from the combined power and pitch...

  9. Calibration of a spinner anemometer for wind speed measurements

    DEFF Research Database (Denmark)

    Demurtas, Giorgio; Friis Pedersen, Troels; Zahle, Frederik

    2016-01-01

    constant related to wind speed measurements. The first and preferred method is based on the definition of the calibration constant and uses wind speed measurements during the stopped condition of the wind turbine. Two alternative methods that did not require the turbine to be stopped were investigated: one...

  10. Measuring Cognitive Load in Embodied Learning Settings

    Directory of Open Access Journals (Sweden)

    Alexander Skulmowski

    2017-08-01

    Full Text Available In recent years, research on embodied cognition has inspired a number of studies on multimedia learning and instructional psychology. However, in contrast to traditional research on education and multimedia learning, studies on embodied learning (i.e., focusing on bodily action and perception in the context of education in some cases pose new problems for the measurement of cognitive load. This review provides an overview over recent studies on embodied learning in which cognitive load was measured using surveys, behavioral data, or physiological measures. The different methods are assessed in terms of their success in finding differences of cognitive load in embodied learning scenarios. At the same time, we highlight the most important challenges for researchers aiming to include these measures into their study designs. The main issues we identified are: (1 Subjective measures must be appropriately phrased to be useful for embodied learning; (2 recent findings indicate potentials as well as problematic aspects of dual-task measures; (3 the use of physiological measures offers great potential, but may require mobile equipment in the context of embodied scenarios; (4 meta-cognitive measures can be useful extensions of cognitive load measurement for embodied learning.

  11. The Load Level of Modern Wind Turbines according to IEC 61400-1

    International Nuclear Information System (INIS)

    Freudenreich, K; Argyriadis, K

    2007-01-01

    The paper describes some effects on the load level of state-of-the art multi megawatt wind turbines introduced by the new edition of the standard IEC 61400-1:2005 W ind Turbines - Part 1: Design requirements . Compared to the previous edition, especially the extreme load determination has been modified by applying stochastic and statistical analyses. Within this paper the effect on the overall load level of wind turbines is demonstrated and occurring problems are discussed. Load simulations have been carried out for four state-of-the-art multi-megawatt wind turbines of different design concepts and from different manufacturers. The blade root bending moments and tip deflection have been determined by applying different extrapolation methods. Advantages and disadvantages of these methods and tail fittings for different load components and wind turbine technologies are discussed and interpreted. Further on, the application of the extreme turbulence model is demonstrated. The dependence of the load level on the turbulence intensity and control system, as well as the interaction with extrapolated loads is discussed and limitations outlined. The obtained load level is compared to the overall load level of the turbines according to the previous edition of the standard, IEC 61400-1:1999

  12. Doppler Wind Lidar Measurements and Scalability to Space

    Data.gov (United States)

    National Aeronautics and Space Administration — Global measurements of wind speed and direction from Doppler wind lidars, if available, would significantly improve forecasting of severe weather events such as...

  13. Outlier robustness for wind turbine extrapolated extreme loads

    DEFF Research Database (Denmark)

    Natarajan, Anand; Verelst, David Robert

    2012-01-01

    . Stochastic identification of numerical artifacts in simulated loads is demonstrated using the method of principal component analysis. The extrapolation methodology is made robust to outliers through a weighted loads approach, whereby the eigenvalues of the correlation matrix obtained using the loads with its...

  14. Wind Tunnel Analysis of the Aerodynamic Loads on Rolling Stock over Railway Embankments: The Effect of Shelter Windbreaks

    Science.gov (United States)

    Avila-Sanchez, Sergio; Lopez-Garcia, Oscar; Sanz-Andres, Angel

    2014-01-01

    Wind-flow pattern over embankments involves an overexposure of the rolling stock travelling on them to wind loads. Windbreaks are a common solution for changing the flow characteristic in order to decrease unwanted effects induced by the presence of cross-wind. The shelter effectiveness of a set of windbreaks placed over a railway twin-track embankment is experimentally analysed. A set of two-dimensional wind tunnel tests are undertaken and results corresponding to pressure tap measurements over a section of a typical high-speed train are herein presented. The results indicate that even small-height windbreaks provide sheltering effects to the vehicles. Also, eaves located at the windbreak tips seem to improve their sheltering effect. PMID:25544954

  15. Assessment of wind turbine drive-train fatigue loads under torsional excitation

    DEFF Research Database (Denmark)

    Gallego Calderon, Juan Felipe; Natarajan, Anand

    2015-01-01

    This paper establishes validated models that can accurately account for the dynamics of the gearbox, along with the external dynamics that excite the system. A drive-train model implementation is presented where the gearbox and generator are coupled to the wind turbine structure in a dynamic...... allows the computation of the bearing and gear-mesh loads. The proposed models are validated by experiments from a 750 kW test-rig. The drive-train model is configured for a 5 MW power capacity and coupled to the corresponding wind turbine and load simulations are carried out under turbulent wind...

  16. Grid Faults Impact on the Mechanical Loads of Active Stall Wind Turbine

    DEFF Research Database (Denmark)

    Iov, Florin; Cutululis, Nicolaos A.; Hansen, Anca D.

    2008-01-01

    Emphasis in this paper is on the fault ride-through operation impact on the wind turbines structural loads. Grid faults are typically simulated in power system simulation tools using simplified drive train mechanical model, approach which doesn't allow a thorough investigation of structural loads...... as the electrical design of the wind turbine response during grid faults. The two-step simulation procedure is assessed by means of a simulation example. The effect of a grid fault on the structural part of a typical fixed speed wind turbine, equipped with an induction generator, is assessed....

  17. A Case for Including Atmospheric Thermodynamic Variables in Wind Turbine Fatigue Loading Parameter Identification

    International Nuclear Information System (INIS)

    Kelley, Neil D.

    1999-01-01

    This paper makes the case for establishing efficient predictor variables for atmospheric thermodynamics that can be used to statistically correlate the fatigue accumulation seen on wind turbines. Recently, two approaches to this issue have been reported. One uses multiple linear-regression analysis to establish the relative causality between a number of predictors related to the turbulent inflow and turbine loads. The other approach, using many of the same predictors, applies the technique of principal component analysis. An examination of the ensemble of predictor variables revealed that they were all kinematic in nature; i.e., they were only related to the description of the velocity field. Boundary-layer turbulence dynamics depends upon a description of the thermal field and its interaction with the velocity distribution. We used a series of measurements taken within a multi-row wind farm to demonstrate the need to include atmospheric thermodynamic variables as well as velocity-related ones in the search for efficient turbulence loading predictors in various turbine-operating environments. Our results show that a combination of vertical stability and hub-height mean shearing stress variables meet this need over a period of 10 minutes

  18. Optimum Parameters of a Tuned Liquid Column Damper in a Wind Turbine Subject to Stochastic Load

    Science.gov (United States)

    Alkmim, M. H.; de Morais, M. V. G.; Fabro, A. T.

    2017-12-01

    Parameter optimization for tuned liquid column dampers (TLCD), a class of passive structural control, have been previously proposed in the literature for reducing vibration in wind turbines, and several other applications. However, most of the available work consider the wind excitation as either a deterministic harmonic load or random load with white noise spectra. In this paper, a global direct search optimization algorithm to reduce vibration of a tuned liquid column damper (TLCD), a class of passive structural control device, is presented. The objective is to find optimized parameters for the TLCD under stochastic load from different wind power spectral density. A verification is made considering the analytical solution of undamped primary system under white noise excitation by comparing with result from the literature. Finally, it is shown that different wind profiles can significantly affect the optimum TLCD parameters.

  19. Differential Effects of Cognitive Load on University Wind Students' Practice

    Science.gov (United States)

    Stambaugh, Laura A.

    2013-01-01

    The purpose of this study was to investigate the effects of cognitive load during practice on university wind students' learning. Cognitive load was manipulated through instrument family (woodwind or brass) and the amount of repetition used in practice (highly repetitive or random). University woodwind and valved-brass students (N = 46)…

  20. Approach to include load sequence effects in the design of an offshore wind turbine substructure

    NARCIS (Netherlands)

    Dragt, R.C.; Allaix, D.L.; Maljaars, J.; Tuitman, J.T.; Salman, Y.; Otheguy, M.E.

    2017-01-01

    Fatigue is one of the main design drivers for offshore wind substructures. Using Fracture Mechanics methods, load sequence effects such as crack growth retardation due to large load peaks can be included in the fatigue damage estimation. Due to the sequence dependency, a method is required that

  1. Unbalanced voltage faults: the impact on structural loads of doubly fed asynchronous generator wind turbines

    DEFF Research Database (Denmark)

    Barahona Garzón, Braulio; Cutululis, Nicolaos Antonio; Hansen, Anca Daniela

    2014-01-01

    , and control dynamics in an integrated simulation environment based on an aeroelastic code (HAWC2) and software for control design (Matlab/Simulink). In the present analysis, 1 Hz equivalent loads are used to compare fatigue loads, whereas maximum–minimum values are used to compare extreme loads. A control......This paper investigates the impact that unbalanced voltage faults have on wind turbine structural loads. In such cases, electromagnetic torque oscillations occur at two times the supply voltage frequency. The objectives of this work are to quantify wind turbine structural loads induced...... by unbalanced voltage faults relative to those during normal operation; and to evaluate the potential for reducing structural loads with the control of the generator. The method applied is integrated dynamic analysis. Namely, dynamic analysis with models that consider the most important aeroelastic, electrical...

  2. Economic emission dispatching with variations of wind power and loads using multi-objective optimization by learning automata

    International Nuclear Information System (INIS)

    Liao, H.L.; Wu, Q.H.; Li, Y.Z.; Jiang, L.

    2014-01-01

    Highlights: • Apply multi-objective optimization by learning automata to power system. • Sequentially dimensional search and state memory are incorporated. • Track dispatch under significant variations of wind power and load demand. • Good performance in terms of accuracy, distribution and computation time. - Abstract: This paper is concerned with using multi-objective optimization by learning automata (MOLA) for economic emission dispatching in the environment where wind power and loads vary. With its capabilities of sequentially dimensional search and state memory, MOLA is able to find accurate solutions while satisfying two objectives: fuel cost coupled with environmental emission and voltage stability. Its searching quality and efficiency are measured using the hypervolume indicator for investigating the quality of Pareto front, and demonstrated by tracking the dispatch solutions under significant variations of wind power and load demand. The simulation studies are carried out on the modified midwestern American electric power system and the IEEE 118-bus test system, in which wind power penetration and load variations present. Evaluated on these two power systems, MOLA is fully compared with multi-objective evolutionary algorithm based on decomposition (MOEA/D) and non-dominated sorting genetic algorithm II (NSGA-II). The simulation results have shown the superiority of MOLA over NAGA-II and MOEA/D, as it is able to obtain more accurate and widely distributed Pareto fronts. In the dynamic environment where the operation condition of both wind speed and load demand varies, MOLA outperforms the other two algorithms, with respect to the tracking ability and accuracy of the solutions

  3. Research on Power System Scheduling Improving Wind Power Accommodation Considering Thermal Energy Storage and Flexible Load

    Science.gov (United States)

    Zou, Chenlu; Cui, Xue; Wang, Heng; Zhou, Bin; Liu, Yang

    2018-01-01

    In the case of rapid development of wind power and heavy wind curtailment, the study of wind power accommodation of combined heat and power system has become the focus of attention. A two-stage scheduling model contains of wind power, thermal energy storage, CHP unit and flexible load were constructed. This model with the objective function of minimizing wind curtailment and the operation cost of units while taking into account of the total coal consumption of units, constraint of thermal energy storage and electricity-heat characteristic of CHP. This paper uses MICA to solve the problem of too many constraints and make the solution more feasible. A numerical example showed that the two stage decision scheduling model can consume more wind power, and it could provide a reference for combined heat and power system short-term operation

  4. Gearbox Fatigue Load Estimation for Condition Monitoring of Wind Turbines

    DEFF Research Database (Denmark)

    Perisic, Nevena; Pedersen, Bo Juul; Kirkegaard, Poul Henning

    2012-01-01

    control and data acquisition (SCADA) system. Estimated loads can be further used for prediction of remaining operating lifetime of turbine components, detection of high stress level or fault detection. An augmented Kalman filter is chosen as the fatigue load estimator because its characteristics well suit...

  5. Wind Energy Management System EMS Integration Project: Incorporating Wind Generation and Load Forecast Uncertainties into Power Grid Operations

    Energy Technology Data Exchange (ETDEWEB)

    Makarov, Yuri V.; Huang, Zhenyu; Etingov, Pavel V.; Ma, Jian; Guttromson, Ross T.; Subbarao, Krishnappa; Chakrabarti, Bhujanga B.

    2010-01-01

    The power system balancing process, which includes the scheduling, real time dispatch (load following) and regulation processes, is traditionally based on deterministic models. Since the conventional generation needs time to be committed and dispatched to a desired megawatt level, the scheduling and load following processes use load and wind and solar power production forecasts to achieve future balance between the conventional generation and energy storage on the one side, and system load, intermittent resources (such as wind and solar generation), and scheduled interchange on the other side. Although in real life the forecasting procedures imply some uncertainty around the load and wind/solar forecasts (caused by forecast errors), only their mean values are actually used in the generation dispatch and commitment procedures. Since the actual load and intermittent generation can deviate from their forecasts, it becomes increasingly unclear (especially, with the increasing penetration of renewable resources) whether the system would be actually able to meet the conventional generation requirements within the look-ahead horizon, what the additional balancing efforts would be needed as we get closer to the real time, and what additional costs would be incurred by those needs. To improve the system control performance characteristics, maintain system reliability, and minimize expenses related to the system balancing functions, it becomes necessary to incorporate the predicted uncertainty ranges into the scheduling, load following, and, in some extent, into the regulation processes. It is also important to address the uncertainty problem comprehensively by including all sources of uncertainty (load, intermittent generation, generators’ forced outages, etc.) into consideration. All aspects of uncertainty such as the imbalance size (which is the same as capacity needed to mitigate the imbalance) and generation ramping requirement must be taken into account. The latter

  6. Toward Isolation of Salient Features in Stable Boundary Layer Wind Fields that Influence Loads on Wind Turbines

    Directory of Open Access Journals (Sweden)

    Jinkyoo Park

    2015-04-01

    Full Text Available Neutral boundary layer (NBL flow fields, commonly used in turbine load studies and design, are generated using spectral procedures in stochastic simulation. For large utility-scale turbines, stable boundary layer (SBL flow fields are of great interest because they are often accompanied by enhanced wind shear, wind veer, and even low-level jets (LLJs. The generation of SBL flow fields, in contrast to simpler stochastic simulation for NBL, requires computational fluid dynamics (CFD procedures to capture the physics and noted characteristics—such as shear and veer—that are distinct from those seen in NBL flows. At present, large-eddy simulation (LES is the most efficient CFD procedure for SBL flow field generation and related wind turbine loads studies. Design standards, such as from the International Electrotechnical Commission (IEC, provide guidance albeit with simplifying assumptions (one such deals with assuming constant variance of turbulence over the rotor and recommend standard target turbulence power spectra and coherence functions to allow NBL flow field simulation. In contrast, a systematic SBL flow field simulation procedure has not been offered for design or for site assessment. It is instructive to compare LES-generated SBL flow fields with stochastic NBL flow fields and associated loads which we evaluate for a 5-MW turbine; in doing so, we seek to isolate distinguishing characteristics of wind shear, wind veer, and turbulence variation over the rotor plane in the alternative flow fields and in the turbine loads. Because of known differences in NBL-stochastic and SBL-LES wind fields but an industry preference for simpler stochastic simulation in design practice, this study investigates if one can reproduce stable atmospheric conditions using stochastic approaches with appropriate corrections for shear, veer, turbulence, etc. We find that such simple tuning cannot consistently match turbine target SBL load statistics, even though

  7. Electromagnetic damper system for ground wind load studies

    Science.gov (United States)

    Scott, L. P.

    1972-01-01

    The design, fabrication, and adaptation of a model damper system to the 5.5% aeroelastic model of the Saturn 1B/Skylab launch vehicle are reported. The damper is dynamically calibrated over the desired range of additive damping for model conditions prior to wind tunnel testing.

  8. Simulation Of Probabilistic Wind Loads On A Building

    Science.gov (United States)

    Chamis, Christos C.; Shah, Ashwin R.

    1994-01-01

    Method of simulating probabilistic windloads on building developed. Numerical results of simulation used to assess reliability of building and risk associated with tendencies of large gusts or high steady winds to cause building to sway, buckle, and/or overturn. Using method to analyze proposed design in iterative design cycle, building designed for specified reliability.

  9. Experimental data on load test and performance parameters of a LENZ type vertical axis wind turbine in open environment condition.

    Science.gov (United States)

    Sivamani, Seralathan; T, Micha Premkumar; Sohail, Mohammed; T, Mohan; V, Hariram

    2017-12-01

    Performance and load testing data of a three bladed two stage LENZ type vertical axis wind turbine from the experiments conducted in an open environment condition at Hindustan Institute of Technology and Science, Chennai (location 23.2167°N, 72.6833°E) are presented here. Low-wind velocity ranging from 2 to 11 m/s is available everywhere irrespective of climatic seasons and this data provides the support to the researchers using numerical tool to validate and develop an enhanced Lenz type design. Raw data obtained during the measurements are processed and presented in the form so as to compare with other typical outputs. The data is measured at different wind speeds prevalent in the open field condition ranging from 3 m/s to 9 m/s.

  10. Model Predictive Control of Wind Turbines using Uncertain LIDAR Measurements

    DEFF Research Database (Denmark)

    Mirzaei, Mahmood; Soltani, Mohsen; Poulsen, Niels Kjølstad

    2013-01-01

    The problem of Model predictive control (MPC) of wind turbines using uncertain LIDAR (LIght Detection And Ranging) measurements is considered. A nonlinear dynamical model of the wind turbine is obtained. We linearize the obtained nonlinear model for different operating points, which are determined......, we simplify state prediction for the MPC. Consequently, the control problem of the nonlinear system is simplified into a quadratic programming. We consider uncertainty in the wind propagation time, which is the traveling time of wind from the LIDAR measurement point to the rotor. An algorithm based...... by the effective wind speed on the rotor disc. We take the wind speed as a scheduling variable. The wind speed is measurable ahead of the turbine using LIDARs, therefore, the scheduling variable is known for the entire prediction horizon. By taking the advantage of having future values of the scheduling variable...

  11. Investigation of piezoelectric flaps for load alleviation using CFD; Wind turbines

    Energy Technology Data Exchange (ETDEWEB)

    Heinz, J.C.

    2010-03-15

    Cost efficient wind power generation demands for large wind turbines with a long lifetime. These demands place high interests on sophisticated load control techniques such as deformable trailing edge flaps. In this work a previously tested prototype airfoil was investigated by using the 2D incompressible RANS solver EllipSys2D. The prototype was built with a Risoe-B1-18 airfoil where piezoelectric actuators THUNDER TH-6R were attached at the trailing edge to realize a movable flap. The results of the simulation were compared to measurements of the previous wind tunnel test and comprehensive steady state computations were conducted to gain information about the general airfoil properties. The model was subsequently used to investigate aero-servo-elastic effects on the 2D airfoil section exposed to a fluctuating inflow. It is explained how a fluctuating inflow was simulated with EllipSys2D and how the CFD solver was coupled with a 3 DOF structural model and with two different control algorithms. Control 1 used the measured AOA in front of the LE as input, Control 2 used the pressure difference between suction and pressure side as input. The model showed a substantial load reduction potential for the present prototype airfoil. For a wind step from 10 m/s to 10.5 m/s the standard deviation of the structural deflection normal to the rotor plane could be reduced with up to 98 % (Control 1) and 96 % (Control 2). A 4 s turbulent inflow with TI=2.2 % could be reduced with up to 81 % (Control 1) and 82 % (Control 2). For a 12 s inflow with TI=2.4 % the standard deviation could be reduced with up to 68 % (Control 1) and 67 % (Control 2). The influence of possible time lags inside the control loop on the reduction potential of the prototype was also investigated. For a 12 s inflow with a tripled turbulence intensity of TI=7.7 % the prototype airfoil could still reach a reduction of up to 54 %. For an extended flap range of -6 to +6 degrees the reduction could be returned to 66

  12. Comparison of different methods for evaluation of wind turbine power production based on wind measurements

    Directory of Open Access Journals (Sweden)

    Bezrukovs Valerijs

    2016-01-01

    Full Text Available Investigations of the wind shear up to the height of 200 (m on the Latvian coast of the Baltic Sea have been carried out using a Pentalum SpiDAR laser measuring complex. Based on wind speeds measurements for three levels – 30, 40 and 50 (m, assessment of the operational efficiency of the wind turbines for heights 100, 140 and 180 (m have been performed. For comparison, this analysis involves five different approaches: the Rayleigh frequency distribution, three different Weibull frequency distributions and method based on approximation of the cubic wind speed. Results are compared with measurements on the corresponding heights.

  13. Load inertia estimation using white and grey-box estimators for power systems with high wind penetration

    OpenAIRE

    Bank Tavakoli, M. Reza; Power, Michael; Ruttledge, Lisa; Flynn, Damian

    2012-01-01

    The increasing penetration of wind farms in power systems has increased concerns over the frequency behaviour and control of synchronous power systems due to a low contribution from modern wind turbines to overall system inertia. With this trend of conventional generators being displaced by variable speed wind turbines, the contribution from load inertia becomes more significant. The need for greater consideration towards load inertia estimation, or even on-line tracking of load inertia, seem...

  14. Wind Energy Management System Integration Project Incorporating Wind Generation and Load Forecast Uncertainties into Power Grid Operations

    Energy Technology Data Exchange (ETDEWEB)

    Makarov, Yuri V.; Huang, Zhenyu; Etingov, Pavel V.; Ma, Jian; Guttromson, Ross T.; Subbarao, Krishnappa; Chakrabarti, Bhujanga B.

    2010-09-01

    The power system balancing process, which includes the scheduling, real time dispatch (load following) and regulation processes, is traditionally based on deterministic models. Since the conventional generation needs time to be committed and dispatched to a desired megawatt level, the scheduling and load following processes use load and wind power production forecasts to achieve future balance between the conventional generation and energy storage on the one side, and system load, intermittent resources (such as wind and solar generation) and scheduled interchange on the other side. Although in real life the forecasting procedures imply some uncertainty around the load and wind forecasts (caused by forecast errors), only their mean values are actually used in the generation dispatch and commitment procedures. Since the actual load and intermittent generation can deviate from their forecasts, it becomes increasingly unclear (especially, with the increasing penetration of renewable resources) whether the system would be actually able to meet the conventional generation requirements within the look-ahead horizon, what the additional balancing efforts would be needed as we get closer to the real time, and what additional costs would be incurred by those needs. In order to improve the system control performance characteristics, maintain system reliability, and minimize expenses related to the system balancing functions, it becomes necessary to incorporate the predicted uncertainty ranges into the scheduling, load following, and, in some extent, into the regulation processes. It is also important to address the uncertainty problem comprehensively, by including all sources of uncertainty (load, intermittent generation, generators’ forced outages, etc.) into consideration. All aspects of uncertainty such as the imbalance size (which is the same as capacity needed to mitigate the imbalance) and generation ramping requirement must be taken into account. The latter unique

  15. Mean load effects on the fatigue life of offshore wind turbine monopile foundations

    DEFF Research Database (Denmark)

    Blasques, José Pedro Albergaria Amaral; Natarajan, Anand

    2013-01-01

    This paper discusses the importance of mean load effects on the estimation of the fatigue damage in offshore wind turbine monopile foundations. The mud line bending moment time series are generated using a fully coupled aero-hydro-elastic model accounting for non-linear water waves and sea current...... of the fatigue life of offshore wind turbine monopile foundations. Moreover, it is shown that a nonlinear hydrodynamic model is required in order to correctly account for the effect of the current....

  16. The Feasibility Study on Thermal Loading Control of Wind Power Converters with a Flexible Switching Frequency

    DEFF Research Database (Denmark)

    Qin, Zian; Wang, Huai; Blaabjerg, Frede

    2015-01-01

    of the IGBT modules, the power losses and thereby the thermal stresses can be controlled by varying the PWM switching frequency according to power loading conditions. This paper investigates the feasibility to apply this flexible modulation strategy in a 3 MW wind power converter application to reduce......Thermal loading of wind power converters is critical to their reliability performance. Especially for IGBT modules applied in a converter, both of the mean value and variation of the junction temperature have significant impact on the lifetime. Besides other strategies to reduce the thermal loading...... the temperature fluctuations due to wind speed variations. The trade-off between the reduced amplitude of temperature fluctuations and the additional power losses that may be introduced is quantitatively studied....

  17. Frequency-domain characteristics of aerodynamic loads of offshore floating vertical axis wind turbines

    DEFF Research Database (Denmark)

    Borg, Michael; Collu, M.

    2015-01-01

    The re-emerging interest in vertical axis wind turbines for floating offshore applications has led to a need to investigate the relatively complex dynamics of such floating offshore structures. Through the use of a coupled model of dynamics this article investigates the frequency-domain character......The re-emerging interest in vertical axis wind turbines for floating offshore applications has led to a need to investigate the relatively complex dynamics of such floating offshore structures. Through the use of a coupled model of dynamics this article investigates the frequency......-domain characteristics of floating vertical axis wind turbine aerodynamic loads. The impact of platform induced motion on aerodynamic loads is discussed in detail, with results indicating an increase in aerodynamic loads of several orders of magnitude over the range of frequencies usually containing significant wave...

  18. Experimental study of wind loads on unique buildings and structures in Russia

    Directory of Open Access Journals (Sweden)

    Poddaeva Olga

    2016-01-01

    Full Text Available Design and construction of unique buildings and structures (sports arenas, airport complexes, business centres, etc. from an engineering point of view is a very difficult task as in most cases these facilities have an original architectural form. Therefore, consideration of wind loads is an important part of the design. The paper presents the definition of wind load for two complex of airport. Researches was applied the combined calculation an experimental method. During the experimental study a wind tunnel architectural and construction type NRU MSUCE was used. Numerical simulations were performed using the software package ANSYS. The result of research on each object are integral aerodynamic loads on the object (coefficients Cx, Cy, Cmz and picture of the distribution of aerodynamic pressure coefficient Cp obtained in the numerical simulation. In conclusion, we discuss the possible formation of deposits of snow and recommendations to eliminate them from the roof of researched objects.

  19. A stochastic framework for the grid integration of wind power using flexible load approach

    International Nuclear Information System (INIS)

    Heydarian-Forushani, E.; Moghaddam, M.P.; Sheikh-El-Eslami, M.K.; Shafie-khah, M.; Catalão, J.P.S.

    2014-01-01

    Highlights: • This paper focuses on the potential of Demand Response Programs (DRPs) to contribute to flexibility. • A stochastic network constrained unit commitment associated with DR is presented. • DR participation levels and electricity tariffs are evaluated on providing a flexible load profile. • Novel quantitative indices for evaluating flexibility are defined to assess the success of DRPs. • DR types and customer participation levels are the main factors to modify the system load profile. - Abstract: Wind power integration has always been a key research area due to the green future power system target. However, the intermittent nature of wind power may impose some technical and economic challenges to Independent System Operators (ISOs) and increase the need for additional flexibility. Motivated by this need, this paper focuses on the potential of Demand Response Programs (DRPs) as an option to contribute to the flexible operation of power systems. On this basis, in order to consider the uncertain nature of wind power and the reality of electricity market, a Stochastic Network Constrained Unit Commitment associated with DR (SNCUCDR) is presented to schedule both generation units and responsive loads in power systems with high penetration of wind power. Afterwards, the effects of both price-based and incentive-based DRPs are evaluated, as well as DR participation levels and electricity tariffs on providing a flexible load profile and facilitating grid integration of wind power. For this reason, novel quantitative indices for evaluating flexibility are defined to assess the success of DRPs in terms of wind integration. Sensitivity studies indicate that DR types and customer participation levels are the main factors to modify the system load profile to support wind power integration

  20. A Cyber-Based Data-Enabled Virtual Organization for Wind Load Effects on Civil Infrastructures: VORTEX-Winds

    Directory of Open Access Journals (Sweden)

    Ahsan Kareem

    2017-08-01

    Full Text Available Despite many advances in the area of wind effects on structures in recent decades, research has been traditionally conducted within limited resources scattered geographically. With the trend toward increasingly complex designs of civil infrastructure combined with the escalating potential for losses by extreme wind events, a new culture of research needs to be established based on innovative and collaborative solutions for better management of the impact of extreme wind events. To address this change, this paper presents a new paradigm of a multiscale cyber-based laboratory framework for the analysis/design, modeling, and simulation of wind load effects based on an ongoing collaborative cyberinfrastructure-based platform, Virtual Organization for Reducing the Toll of EXtreme Winds (VORTEX-Winds, https://vortex-winds.org, and discusses its current status since its inception in 2007 and ongoing developments. This collaborative framework as it evolves would enable a paradigm shift by offering advanced cyber-enabled modules (e-modules for accelerating advances in research and education to achieve improved understanding and better modeling of wind effects on structures. Accordingly, it will enhance wind community’s analysis and design capabilities to address next-generation challenges posed by wind. Through empowering those without computational or experimental resources, the e-modules will encompass a large set of subject areas and topics categorized as Database-enabled design, Full-scale/Field site data repository, Statistical/Stochastic toolboxes, Tele-experimentation, Uncertainty modeling, Damage assessment, and Computational platforms. This prototype will allow access to the individual e-module, while it is envisaged that next level of development in VORTEX-Winds will have the capability for an automated and integrated analysis/design through a nexus of e-modules. A highlight of the e-modules currently completed or in development is presented

  1. Standards for measurements and testing of wind turbine power quality

    Energy Technology Data Exchange (ETDEWEB)

    Soerensen, P. [Risoe National Lab., Roskilde (Denmark); Gerdes, G.; Klosse, R.; Santjer, F. [DEWI, Wilhelmshaven (Germany); Robertson, N.; Davy, W. [NEL, Glasgow (United Kingdom); Koulouvari, M.; Morfiadakis, E. [CRES, Pikermi (Greece); Larsson, Aa. [Chalmers Univ. of Technology, Goeteborg (Sweden)

    1999-03-01

    The present paper describes the work done in power quality sub-task of the project `European Wind Turbine Testing Procedure Developments` funded by the EU SMT program. The objective of the power quality sub-task has been to make analyses and new recommendation(s) for the standardisation of measurement and verification of wind turbine power quality. The work has been organised in three major activities. The first activity has been to propose measurement procedures and to verify existing and new measurement procedures. This activity has also involved a comparison of the measurements and data processing of the participating partners. The second activity has been to investigate the influence of terrain, grid properties and wind farm summation on the power quality of wind turbines with constant rotor speed. The third activity has been to investigate the influence of terrain, grid properties and wind farm summation on the power quality of wind turbines with variable rotor speed. (au)

  2. Noise measurement in wind tunnels, workshop summary

    Science.gov (United States)

    Hickley, D. H.; Williams, J.

    1982-09-01

    In reviewing the progress made in acoustic measurements in wind tunnels over the 5-yr span of the workshops, it is evident that a great deal of progress has occurred. Specialized facilities are now on line, special measurement techniques were developed, and corrections were devised and proven. This capability is in the process of creating a new and more correct data bank on acoustic phenomena, and represents a major step forward in acoustics technology. Additional work is still required, but now, rather than concentrating on facilities and techniques, researchers may more profitably concentrate on noise-source modeling, with the simulation of propulsor noise source (in flight) and of propulsor/airframe airflow characteristics. Promising developments in directional acoustic receivers and other discrimination/correlation techniques should now be regularly exploited, in part for model noise-source diagnosis, but also to expedite extraction of the lone source signal from any residual background noise and reverberation in the working chamber and from parasitic noise due to essential rigs or instrumentation inside the airstream.

  3. Effects of rotor location, coning, and tilt on critical loads in large wind turbines

    Science.gov (United States)

    Spera, D. A.; Janetzke, D. C.

    1978-01-01

    Several large (1500 kW) horizontal rotor configurations were analyzed to determine the effects on dynamic loads of upwind downwind rotor locations, coned and radial blade positions, and tilted and horizontal rotor axis positions. Loads were calculated for a range of wind velocities at three locations in the structure: (1) the blade shank; (2) the hub shaft; and (3) the yaw drive. Blade axis coning and rotor axis tilt were found to have minor effects on loads. However, locating the rotor upwind of the tower significantly reduced loads at all locations analyzed.

  4. Load Coefficients on Grates used for Wind Turbine Access Platforms

    DEFF Research Database (Denmark)

    Andersen, Thomas Lykke; Rasmussen, Michael R.; Frigaard, Peter

    In this report is presented the results of tests carried out at Dept. of Civil Engineering, Aalborg University (AAU) on behalf of DONG Energy A/S and Vattenfall A/S, Denmark. The objective of the tests was to investigate the load coefficient on different platform grates and a solid plate for desi......In this report is presented the results of tests carried out at Dept. of Civil Engineering, Aalborg University (AAU) on behalf of DONG Energy A/S and Vattenfall A/S, Denmark. The objective of the tests was to investigate the load coefficient on different platform grates and a solid plate...

  5. Impacts of Providing Inertial Response on Dynamic Loads of Wind Turbine Drivetrains: Preprint

    Energy Technology Data Exchange (ETDEWEB)

    Girsang, I. P.; Dhupia, J.; Singh, M.; Gevorgian, V.; Muljadi, E.; Jonkman, J.

    2014-09-01

    There has been growing demand from the power industry for wind power plants to support power system operations. One such requirement is for wind turbines to provide ancillary services in the form of inertial response. When the grid frequency drops, it is essential for wind turbine generators (WTGs) to inject kinetic energy stored in their inertia into the grid to help arrest the frequency decline. However, the impacts of inertial response on the structural loads of the wind turbine have not been given much attention. To bridge this gap, this paper utilizes a holistic model for both fixed-speed and variable-speed WTGs by integrating the aeroelastic wind turbine model in FAST, developed by the National Renewable Energy Laboratory, with the electromechanical drivetrain model in SimDriveline and SimPowerSystems.

  6. Small-Signal Stability Analysis of Full-Load Converter Interfaced Wind Turbines

    DEFF Research Database (Denmark)

    Knüppel, Thyge; Akhmatov, Vladislav; Nielsen, Jørgen Nygård

    2009-01-01

    Power system stability investigations of wind farms often cover the tasks of low-voltage-fault-ride-through, voltage and reactive power control, and power balancing, but not much attention has yet been paid to the task of small-signal stability. Small-signal stability analysis needs increasing...... focus since the share of wind power increases substituting power generation from conventional power plants. Here, a study based on modal analysis is presented which investigate the effect of large scale integration of full-load converter interfaced wind turbines on inter-area oscillations in a three...... generator network. A detailed aggregated wind turbine model is employed which includes all necessary control functions. It is shown that the wind urbines have very low participation in the inter-area power oscillation....

  7. Thermal Loading and Lifetime Estimation for Power Device Considering Mission Profiles in Wind Power Converter

    DEFF Research Database (Denmark)

    Ma, Ke; Liserre, Marco; Blaabjerg, Frede

    2015-01-01

    As a key component in the wind turbine system, the power electronic converter and its power semiconductors suffer from complicated power loadings related to environment, and are proven to have high failure rates. Therefore, correct lifetime estimation of wind power converter is crucial for the re......As a key component in the wind turbine system, the power electronic converter and its power semiconductors suffer from complicated power loadings related to environment, and are proven to have high failure rates. Therefore, correct lifetime estimation of wind power converter is crucial....... Consequently, a relative more advanced approach is proposed in this paper, which is based on the loading and strength analysis of devices and takes into account different time constants of the thermal behaviors in power converter. With the established methods for loading and lifetime estimation for power...... devices, more detailed information of the lifetime-related performance in wind power converter can be obtained. Some experimental results are also included to validate the thermal behavior of power device under different mission profiles....

  8. Analyzing the Energy Performance, Wind Loading, and Costs of Photovoltaic Slat Modules on Commercial Rooftops

    Energy Technology Data Exchange (ETDEWEB)

    Van Geet, Otto D. [National Renewable Energy Lab. (NREL), Golden, CO (United States); Fu, Ran [National Renewable Energy Lab. (NREL), Golden, CO (United States); Horowitz, Kelsey A. [National Renewable Energy Lab. (NREL), Golden, CO (United States); Kurup, Parthiv [National Renewable Energy Lab. (NREL), Golden, CO (United States); MacAlpine, Sara M. [National Renewable Energy Lab. (NREL), Golden, CO (United States); Silverman, Timothy J. [National Renewable Energy Lab. (NREL), Golden, CO (United States)

    2018-02-13

    NREL studied a new type of photovoltaic (PV) module configuration wherein multiple narrow, tilted slats are mounted in a single frame. Each slat of the PV slat module contains a single row of cells and is made using ordinary crystalline silicon PV module materials and processes, including a glass front sheet and weatherproof polymer encapsulation. Compared to a conventional ballasted system, a system using slat modules offer higher energy production and lower weight at lower LCOE. The key benefits of slat modules are reduced wind loading, improved capacity factor and reduced installation cost. First, the individual slats allow air to flow through, which reduce wind loading. Using PV performance modeling software, we compared the performance of an optimized installation of slats modules to a typical installation of conventional modules in a ballasted rack mounting system. Based on the results of the performance modeling two different row tilt and spacing were tested in a wind tunnel. Scaled models of the PV Slat modules were wind tunnel tested to quantify the wind loading of a slat module system on a commercial rooftop, comparing the results to conventional ballasted rack mounted PV modules. Some commercial roofs do not have sufficient reserve dead load capacity to accommodate a ballasted system. A reduced ballast system design could make PV system installation on these roofs feasible for the first time without accepting the disadvantages of penetrating mounts. Finally, technoeconomic analysis was conducted to enable an economic comparison between a conventional commercial rooftop system and a reduced-ballast slat module installation.

  9. Wind Atlas for South Africa (WASA). Report on Measurements

    DEFF Research Database (Denmark)

    Mabille, Eugéne; Prinsloo, Eric; Mortensen, Niels Gylling

    The key to any good and accurate wind atlas is good quality data. To this end the 1st Verified Numerical Wind Atlas South Africa, for parts of the Northern and Eastern Capes as well as the Western Cape makes use of meteorological data from ten sites, distributed throughout the modelling domain......, to verify the results of the meso-scale modelling. The Measurements work package (WP2) is one of six work packages that collectively make up the Wind Atlas for South Africa (WASA) project. The measurements also provide observed wind climates at the measurement sites, which can be used by micrositing...

  10. Design of a new urban wind turbine airfoil using a pressure-load inverse method

    Energy Technology Data Exchange (ETDEWEB)

    Henriques, J.C.C.; Gato, L.M.C. [IDMEC, Instituto Superior Tecnico, Universidade Tecnica de Lisboa, Av. Rovisco Pais, 1049-001 Lisboa (Portugal); Marques da Silva, F. [LNEC - Laboratorio Nacional de Engenharia Civil, Av. Brasil, 101, 1700-066 Lisboa (Portugal); Estanqueiro, A.I. [INETI - Instituto Nacional de Engenharia, Tecnologia e Inovacao Estrada do Paco do Lumiar, 1649-038 Lisboa (Portugal)

    2009-12-15

    This paper presents the design methodology of a new wind turbine airfoil that achieves high performance in urban environment by increasing the maximum lift. For this purpose, an inverse method was applied to obtain a new wind turbine blade section with constant pressure-load along the chord, at the design inlet angle. In comparison with conventional blade section designs, the new airfoil has increased maximum lift, reduced leading edge suction peak and controlled soft-stall behaviour, due to a reduction of the adverse pressure gradient on the suction side. Wind tunnel experimental results confirmed the computational results. (author)

  11. Assessment of the Dynamic Behaviour of Saturated Soil Subjected to Cyclic Loading from Offshore Monopile Wind Turbine Foundations

    DEFF Research Database (Denmark)

    Damgaard, Mads; Bayat, Mehdi; Andersen, Lars Vabbersgaard

    2014-01-01

    The fatigue life of offshore wind turbines strongly depends on the dynamic behaviour of the structures including the underlying soil. To diminish dynamic amplification and avoid resonance, the eigenfrequency related to the lowest eigenmode of the wind turbine should not coalesce with excitation...... frequencies related to strong wind, wave and ice loading. Typically, lateral response of monopile foundations is analysed using a beam on a nonlinear Winkler foundation model with soil-pile interaction recommended by the design regulations. However, as it will be shown in this paper, the guideline approaches...... consequently underestimate the eigenfrequency compared to full-scale measurements. This discrepancy leads the authors to investigate the influence of pore water pressure by utilising a numerical approach and consider the soil medium as a two-phase system consisting of a solid skeleton and a single pore fluid...

  12. Harmonic models of a back-to-back converter in large offshore wind farms compared with measurement data

    DEFF Research Database (Denmark)

    Kocewiak, Lukasz Hubert; Hjerrild, Jesper; Bak, Claus Leth

    2009-01-01

    The offshore wind farm with installed back-to-back power converter in wind turbines is studied. As an example the Burbo Bank offshore wind farm with Siemens Wind Power wind turbines is taken into consideration. The wind farm is simulated in DIgSILENT Power Factory software in order to determine a...... results are compared with measurement data from the Burbo Bank offshore wind farm. The delimitations of both power converter models with referent to harmonic analysis are shown in this paper....... and assess harmonic emission in the point of common coupling. Different modelling methods of power electronic devices installed in wind turbines are presented. Harmonic load flow analysis and impedance frequency characteristics calculation are conducted to present differences between the models. Simulation...

  13. Temperature Effects on the Wind Direction Measurement of 2D Solid Thermal Wind Sensors

    Science.gov (United States)

    Chen, Bei; Zhu, Yan-Qing; Yi, Zhenxiang; Qin, Ming; Huang, Qing-An

    2015-01-01

    For a two-dimensional solid silicon thermal wind sensor with symmetrical structure, the wind speed and direction information can be derived from the output voltages in two orthogonal directions, i.e., the north-south and east-west. However, the output voltages in these two directions will vary linearly with the ambient temperature. Therefore, in this paper, a temperature model to study the temperature effect on the wind direction measurement has been developed. A theoretical analysis has been presented first, and then Finite Element Method (FEM) simulations have been performed. It is found that due to symmetrical structure of the thermal wind sensor, the temperature effects on the output signals in the north-south and east-west directions are highly similar. As a result, the wind direction measurement of the thermal wind sensor is approximately independent of the ambient temperature. The experimental results fit the theoretical analysis and simulation results very well. PMID:26633398

  14. Space Shuttle Damper System for Ground Wind Load Tests

    Science.gov (United States)

    Robinson, G. D.; Holt, J. R.; Chang, C. S.

    1973-01-01

    An active damper system which was originally developed for a 5.5% Saturn IB/Skylab Ground Winds Model was modified and used for similar purposes in a Space Shuttle model. A second damper system which was originally used in a 3% Saturn V/Dry Workshop model was also modified and made compatible with the Space Shuttle model to serve as a back-up system. Included in this final report are descriptions of the modified damper systems and the associated control and instrumentation.

  15. Analysis of Oscillations in a Cableway: Wind Load Effects

    Directory of Open Access Journals (Sweden)

    Jan Gustincic

    2013-06-01

    Full Text Available The purpose of this paper is to develop and investigate a non-linear model for analysing the reaction of a self-detachable cabin monocable ropeway exposed to a sudden deceleration and wind forces. The First and Second Newton's Law and Differential Equations are the basic tools for building the model. Furthermore a few basic considerations have been made about the air “dragging and lifting" forces that induce oscillations and vibrations in mechanical systems alike. All the numerical data used for the simulation was taken from a ropeway in the skiing site of Ravascletto-Zoncolan in the North- East of Italy.

  16. Spatial reliability analysis of a wind turbine blade cross section subjected to multi-axial extreme loading

    DEFF Research Database (Denmark)

    Dimitrov, Nikolay Krasimirov; Bitsche, Robert; Blasques, José Pedro Albergaria Amaral

    2017-01-01

    This paper presents a methodology for structural reliability analysis of wind turbine blades. The study introduces several novel elements by taking into account loading direction using a multiaxial probabilistic load model, considering random material strength, spatial correlation between materia...

  17. Reduction of aerodynamic load fluctuation on wind turbine blades through active flow control

    Science.gov (United States)

    Velarde, John-Michael; Coleman, Thomas; Magstadt, Andrew; Aggarwal, Somil; Glauser, Mark

    2015-11-01

    The current set of experiments deals with implementing active flow control on a Bergey Excel 1, 1kW turbine. The previous work in our group demonstrated successfully that implementation of a simple closed-loop controller could reduce unsteady aerodynamic load fluctuation by 18% on a vertically mounted wing. Here we describe a similar flow control method adapted to work in the rotating frame of a 2.5m diameter wind turbine. Strain gages at the base of each blade measure the unsteady fluctuation in the blades and pressure taps distributed along the span of the blades feed information to the closed-loop control scheme. A realistic, unsteady flow field has been generated by placing a cylinder upstream of the turbine to induce shedding vortices at frequencies in the bandwidth of the first structural bending mode of the turbine blades. The goal of these experiments is to demonstrate closed-loop flow control as a means to reduce the unsteady fluctuation in the blades and increase the overall lifespan of the wind turbine.

  18. Forces and Moments on Flat Plates of Small Aspect Ratio with Application to PV Wind Loads and Small Wind Turbine Blades

    Directory of Open Access Journals (Sweden)

    Xavier Ortiz

    2015-03-01

    Full Text Available To improve knowledge of the wind loads on photovoltaic structures mounted on flat roofs at the high angles required in high latitudes, and to study starting flow on low aspect ratio wind turbine blades, a series of wind tunnel tests were undertaken. Thin flat plates of aspect ratios between 0.4 and 9.0 were mounted on a sensitive three-component instantaneous force and moment sensor. The Reynolds numbers varied from 6 × 104 to 2 × 105. Measurements were made for angles of attack between 0° and 90° both in the free stream and in wall proximity with increased turbulence and mean shear. The ratio of drag to lift closely follows the inverse tangent of the angle of incidence for virtually all measurements. This implies that the forces of interest are due largely to the instantaneous pressure distribution around the plate and are not significantly influenced by shear stresses. The instantaneous forces appear most complex for the smaller aspect ratios but the intensity of the normal force fluctuations is between 10% and 20% in the free-steam but can exceed 30% near the wall. As the wind tunnel floor is approached, the lift and drag reduce with increasing aspect ratio, and there is a reduction in the high frequency components of the forces. It is shown that the centre of pressure is closer to the centre of the plates than the quarter-chord position for nearly all cases.

  19. Comparison of Second-Order Loads on a Tension-Leg Platform for Wind Turbines: Preprint

    Energy Technology Data Exchange (ETDEWEB)

    Gueydon, S.; Wuillaume, P.; Jonkman, J.; Robertson, A.; Platt, A.

    2015-03-01

    The first objective of this work is to compare the two floating offshore wind turbine simulation packages {DIFFRAC+aNySIM} and {WAMIT+FAST}. The focus is on second-order wave loads, and so first- and second-order wave loads are applied to a structure sequentially for a detailed comparison and a more precise analysis of the effects of the second-order loads. aNySIM does not have the capability to model flexible bodies, and so the simulations performed in this tool are done assuming a rigid body. FAST also assumes that the platform is rigid, but can account for the flexibility of the tower. The second objective is to study the effects of the second-order loads on the response of a TLP floating wind turbine. The flexibility of the tower must be considered for this investigation, and therefore only FAST is used.

  20. Optimizing Lidar Scanning Strategies for Wind Energy Measurements (Invited)

    Science.gov (United States)

    Newman, J. F.; Bonin, T. A.; Klein, P.; Wharton, S.; Chilson, P. B.

    2013-12-01

    Environmental concerns and rising fossil fuel prices have prompted rapid development in the renewable energy sector. Wind energy, in particular, has become increasingly popular in the United States. However, the intermittency of available wind energy makes it difficult to integrate wind energy into the power grid. Thus, the expansion and successful implementation of wind energy requires accurate wind resource assessments and wind power forecasts. The actual power produced by a turbine is affected by the wind speeds and turbulence levels experienced across the turbine rotor disk. Because of the range of measurement heights required for wind power estimation, remote sensing devices (e.g., lidar) are ideally suited for these purposes. However, the volume averaging inherent in remote sensing technology produces turbulence estimates that are different from those estimated by a sonic anemometer mounted on a standard meteorological tower. In addition, most lidars intended for wind energy purposes utilize a standard Doppler beam-swinging or Velocity-Azimuth Display technique to estimate the three-dimensional wind vector. These scanning strategies are ideal for measuring mean wind speeds but are likely inadequate for measuring turbulence. In order to examine the impact of different lidar scanning strategies on turbulence measurements, a WindCube lidar, a scanning Halo lidar, and a scanning Galion lidar were deployed at the Southern Great Plains Atmospheric Radiation Measurement (ARM) site in Summer 2013. Existing instrumentation at the ARM site, including a 60-m meteorological tower and an additional scanning Halo lidar, were used in conjunction with the deployed lidars to evaluate several user-defined scanning strategies. For part of the experiment, all three scanning lidars were pointed at approximately the same point in space and a tri-Doppler analysis was completed to calculate the three-dimensional wind vector every 1 second. In another part of the experiment, one of

  1. Rotor equivalent wind speed for power curve measurement - comparative exercise for IEA Wind Annex 32

    Science.gov (United States)

    Wagner, R.; Cañadillas, B.; Clifton, A.; Feeney, S.; Nygaard, N.; Poodt, M.; St. Martin, C.; Tüxen, E.; Wagenaar, J. W.

    2014-06-01

    A comparative exercise has been organised within the International Energy Agency (IEA) Wind Annex 32 in order to test the Rotor Equivalent Wind Speed (REWS) method under various conditions of wind shear and measurement techniques. Eight organisations from five countries participated in the exercise. Each member of the group has derived both the power curve based on the wind speed at hub height and the power curve based on the REWS. This yielded results for different wind turbines, located in diverse types of terrain and where the wind speed profile was measured with different instruments (mast or various lidars). The participants carried out two preliminary steps in order to reach consensus on how to implement the REWS method. First, they all derived the REWS for one 10 minute wind speed profile. Secondly, they all derived the power curves for one dataset. The main point requiring consensus was the definition of the segment area used as weighting for the wind speeds measured at the various heights in the calculation of the REWS. This comparative exercise showed that the REWS method results in a significant difference compared to the standard method using the wind speed at hub height in conditions with large shear and low turbulence intensity.

  2. Frequency swept fibre laser for wind speed measurements

    DEFF Research Database (Denmark)

    Pedersen, Anders Tegtmeier

    undertaken with a positive outcome encouraging an experimental trial to measure wind with a such construction. Therefore, a small telescope CW lidar designed for turbine blade integration has been tested in a high performance wind tunnel, and very good agreement with reference measurements has been obtained....

  3. Active load reduction using individual pitch, based on local blade flow measurements

    DEFF Research Database (Denmark)

    Larsen, Torben J.; Aagaard Madsen, H.; Thomsen, K.

    2005-01-01

    -of-the-art load-reducing concepts. Since the new flow-based concept deviates significantly from previous published load-reducing strategies, a comparison of the performance based on aeroelastic simulations is included. Advantages and drawbacks of the systems are discussed. Copyright (C) 2004 John Wiley Sons, Ltd.......A new load-reducing control strategy for individual blade control of large pitch-controlled wind turbines is presented This control concept is based on local blade inflow measurements and offers the possibility of larger load reductions, without loss of power production, than seen in other state...

  4. South African wind loading specifications: the Euro way?

    CSIR Research Space (South Africa)

    Goliger, Adam M

    2007-10-01

    Full Text Available at the time, was undertaken towards the end of 1999 (Goliger, 2000). The code was assessed as being comprehensive, inclusive and detailed. However, at that stage the document was clearly unfinished and contained several discrepancies, inconsistencies... limit state and working stress ), as well as the principle of an average return period of 1000 years. t prepara iminary analysis of the Australian code revea An initial set of comparative calculations indicated the loads stipulated according...

  5. Assessment and Optimization of Lidar Measurement Availability for Wind Turbine Control: Preprint

    Energy Technology Data Exchange (ETDEWEB)

    Davoust, S.; Jehu, A.; Bouillet, M.; Bardon, M.; Vercherin, B.; Scholbrock, A.; Fleming, P.; Wright, A.

    2014-05-01

    Turbine-mounted lidars provide preview measurements of the incoming wind field. By reducing loads on critical components and increasing the potential power extracted from the wind, the performance of wind turbine controllers can be improved [2]. As a result, integrating a light detection and ranging (lidar) system has the potential to lower the cost of wind energy. This paper presents an evaluation of turbine-mounted lidar availability. Availability is a metric which measures the proportion of time the lidar is producing controller-usable data, and is essential when a wind turbine controller relies on a lidar. To accomplish this, researchers from Avent Lidar Technology and the National Renewable Energy Laboratory first assessed and modeled the effect of extreme atmospheric events. This shows how a multirange lidar delivers measurements for a wide variety of conditions. Second, by using a theoretical approach and conducting an analysis of field feedback, we investigated the effects of the lidar setup on the wind turbine. This helps determine the optimal lidar mounting position at the back of the nacelle, and establishes a relationship between availability, turbine rpm, and lidar sampling time. Lastly, we considered the role of the wind field reconstruction strategies and the turbine controller on the definition and performance of a lidar's measurement availability.

  6. The Wind Profile in the Coastal Boundary Layer: Wind Lidar Measurements and Numerical Modelling

    DEFF Research Database (Denmark)

    Floors, Rogier; Vincent, Claire Louise; Gryning, Sven-Erik

    2013-01-01

    Traditionally it has been difficult to verify mesoscale model wind predictions against observations in the planetary boundary layer (PBL). Here we used measurements from a wind lidar to study the PBL up to 800 m above the surface at a flat coastal site in Denmark during a one month period in autu...

  7. Hot Wire Anemometer Turbulence Measurements in the wind Tunnel of LM Wind Power

    DEFF Research Database (Denmark)

    Fischer, Andreas

    Flow measurements were carried out in the wind tunnel of LM Wind Power A/S with a Dantec Streamline CTA system to characterize the flow turbulence. Besides the free tunnel flow with empty test section we also investigated the tunnel flow when two grids with different mesh size were introduced dow...

  8. Correlated wind-power production and electric load scenarios for investment decisions

    International Nuclear Information System (INIS)

    Baringo, L.; Conejo, A.J.

    2013-01-01

    Highlights: ► Investment models require an accurate representation of the involved uncertainty. ► Demand and wind power production are correlated and uncertain parameters. ► Two methodologies are provided to represent uncertainty and correlation. ► An accurate uncertainty representation is crucial to get optimal results. -- Abstract: Stochastic programming constitutes a useful tool to address investment problems. This technique represents uncertain input data using a set of scenarios, which should accurately describe the involved uncertainty. In this paper, we propose two alternative methodologies to efficiently generate electric load and wind-power production scenarios, which are used as input data for investment problems. The two proposed methodologies are based on the load- and wind-duration curves and on the K-means clustering technique, and allow representing the uncertainty of and the correlation between electric load and wind-power production. A case study pertaining to wind-power investment is used to show the interest of the proposed methodologies and to illustrate how the selection of scenarios has a significant impact on investment decisions.

  9. Loads Correlation of a Full-Scale UH-60A Airloads Rotor in a Wind Tunnel

    Science.gov (United States)

    Yeo, Hyeonsoo; Romander, Ethan A.

    2012-01-01

    Wind tunnel measurements of the rotor trim, blade airloads, and structural loads of a full-scale UH-60A Black Hawk main rotor are compared with calculations obtained using the comprehensive rotorcraft analysis CAMRAD II and a coupled CAMRAD II/OVERFLOW 2 analysis. A speed sweep at constant lift up to an advance ratio of 0.4 and a thrust sweep at constant speed into deep stall are investigated. The coupled analysis shows significant improvement over comprehensive analysis. Normal force phase is better captured and pitching moment magnitudes are better predicted including the magnitude and phase of the two stall events in the fourth quadrant at the deeply stalled condition. Structural loads are, in general, improved with the coupled analysis, but the magnitude of chord bending moment is still significantly underpredicted. As there are three modes around 4 and 5/rev frequencies, the structural responses to the 5/rev airloads due to dynamic stall are magnified and thus care must be taken in the analysis of the deeply stalled condition.

  10. Including load sequence effects in the fatigue damage estimation of an offshore wind turbine substructure

    NARCIS (Netherlands)

    Dragt, R.C.; Maljaars, J.; Tuitman, J.T.; Salman, Y.; Otheguy, M.E.

    2016-01-01

    Retardation is a load sequence effect, which causes a reduced fatigue crack growth rate after an overload is encountered. Retardation can be cancelled when the overload is followed by an underload. The net effect is beneficial to the fatigue lifetime of Offshore Wind Turbines (OWTs). To be able to

  11. Device loading of modular multilevel converter MMC in wind power application

    DEFF Research Database (Denmark)

    Popova, L.; Pyrhönen, J.; Ma, Ke

    2014-01-01

    . The converters used to connect the wind turbine to the grid having the rated active powers of 2MW and 10MW are designed and investigated. Electrical losses and thermal loading of the power devices in the proposed converter solutions are analyzed. The efficiency of the MMC converter under different P/Q boundaries...

  12. Influence of Nonlinear Irregular Waves on the Fatigue Loads of an Offshore Wind Turbine

    NARCIS (Netherlands)

    Van der Meulen, M.B.; Ashuri, T.; Van Bussel, G.J.W.; Molenaar, D.P.

    2012-01-01

    In order to make offshore wind power a cost effective solution that can compete with the traditional fossil energy sources, cost reductions on the expensive offshore support structures are required. One way to achieve this, is to reduce the uncertainty in wave load calculations by using a more

  13. Analysis of wind driven self-excited induction generator supplying isolated DC loads

    Directory of Open Access Journals (Sweden)

    Khaled S. Sakkoury

    2017-05-01

    Full Text Available This paper presents the analysis, modelling and simulation of wind-driven self-excited induction generator (SEIG. The three-phase SEIG is driven by a variable-speed prime mover to represent a wind turbine. Also, the paper investigates the dynamic performance of the SEIG during start-up, increasing or decreasing the load or rotor speed. The value of the excitation capacitance required for the SEIG is calculated to give suitable saturation level to assure self-excitation and to avoid heavy saturation levels. Matching of the maximum power available from the wind turbine is performed through varying the load value. The effect of AC–DC power conversion on the generator is investigated. The system simulation is carried out using MATLAB/SIMULINK toolbox program.

  14. Impact of fault ride-through requirements on fixed-speed wind turbine structural loads

    DEFF Research Database (Denmark)

    Hansen, Anca Daniela; Cutululis, Nicolaos Antonio; Markou, Helen

    2011-01-01

    simulation tools, which have expertise in different specialized wind turbines design areas. Two complimentary simulation tools are considered i.e. the detailed power system simulation tool PowerFactory from DIgSILENT and the advanced aeroelastic computer code HAWC2, in order to assess of the dynamic response...... by performing a rainflow and a statistical analysis for fatigue and ultimate structural loads, respectively. Two cases are compared i.e. one where the turbine is immediately disconnected from the grid when a grid fault occurs and one where the turbine is equipped with a fault ride-through controller...... faults. This article proposes a computer approach for the quantification of the wind turbines structural loads caused by the fault ride-through grid requirements. This approach, exemplified for the case of a 2MW active stall wind turbine, relies on the combination of knowledge from complimentary...

  15. Full scale investigation of the wind loads on a light-weight building-integrated photovoltaic system

    NARCIS (Netherlands)

    Geurts, C.P.W.; Bronkhorst, A.J.; Bentum, C.A. van

    2017-01-01

    The wind loads on solar energy systems are crucial for the engineering of the panels, substructure and fixings. There is a demand for aesthetically more acceptable solutions such as frameless solar systems. For these frameless systems, the wind loads are carried by the panels themselves. Combined

  16. Damage preventing measures for wind turbines. Phase 1- Reliability data

    Energy Technology Data Exchange (ETDEWEB)

    Carlsson, Fredrik; Eriksson, Emil; Dahlberg, Magnus

    2010-08-15

    The state of existing reliability and failure data in the public sources has been investigated. The prime goal has been to evaluate the data's usefulness for developing damage preventing measures. Some publicly available databases exist, and the data has been presented in several papers in the literature. The results from the investigation can seem quite negative. Detailed data are lacking and the level of detailed reporting has even been decreasing in recent years. Information on the impact of load condition on failures, which is an important question, are lacking throughout in the statistics. Some components dominate the failure statistics. These are for example the gearboxes, where failures lead to long down times. Failures of the electrical system lead to considerably shorter down times but the failure rate is much higher. Severe rotor failures seem to be rare, but they occur and the consequences can be dramatic. Operators and insurance companies are demanding improved insight in damage collection, maintenance and overall damage preventing measures. Closer cooperation with these parties could be a fruitful way of gathering more useful data. Improvements for future databases are suggested. A structure for damage collection is proposed. Comparing experience of damage preventing measures from other industries, knowledge about the nature of the damage mechanism and current practice in the wind industry will be an important tool in the evaluation of different damage preventing measures. This will be done in the following phases of this project

  17. Investigation of the dependency of wind turbine loads on the simulation time

    DEFF Research Database (Denmark)

    Tibaldi, Carlo; Henriksen, Lars Christian; Bak, Christian

    2014-01-01

    In this work the dependency of several wind turbine parameters with respect to the length of simulations used for their evaluation is investigated. The analysis is performed by computing the parameters with a different number of turbulent wind simulations, therefore simulation time, and repeating...... the computation with different turbulence realizations. The repetition of the computation is performed to identify the scatter of the parameters for a given number of turbulent seeds due to the different turbulence realization. The dependency on the simulation time of load variations due to changes...... in the collective pitch controller tuning is also investigated. Results show a significantly high dependency of the parameters and their variations on the turbulent wind realization. This dependency makes the use of turbulent wind simulation results not reliable for numerical optimization purposes....

  18. Simulation of Mechanical Behavior and Damage of a Large Composite Wind Turbine Blade under Critical Loads

    Science.gov (United States)

    Tarfaoui, M.; Nachtane, M.; Khadimallah, H.; Saifaoui, D.

    2018-04-01

    Issues such as energy generation/transmission and greenhouse gas emissions are the two energy problems we face today. In this context, renewable energy sources are a necessary part of the solution essentially winds power, which is one of the most profitable sources of competition with new fossil energy facilities. This paper present the simulation of mechanical behavior and damage of a 48 m composite wind turbine blade under critical wind loads. The finite element analysis was performed by using ABAQUS code to predict the most critical damage behavior and to apprehend and obtain knowledge of the complex structural behavior of wind turbine blades. The approach developed based on the nonlinear FE analysis using mean values for the material properties and the failure criteria of Tsai-Hill to predict failure modes in large structures and to identify the sensitive zones.

  19. Model Predictive Control of Wind Turbines using Uncertain LIDAR Measurements

    DEFF Research Database (Denmark)

    Mirzaei, Mahmood; Soltani, Mohsen; Poulsen, Niels Kjølstad

    2013-01-01

    The problem of Model predictive control (MPC) of wind turbines using uncertain LIDAR (LIght Detection And Ranging) measurements is considered. A nonlinear dynamical model of the wind turbine is obtained. We linearize the obtained nonlinear model for different operating points, which are determined...

  20. Scaling Issues in the Determination of Wind loads on Lattice Masts

    DEFF Research Database (Denmark)

    Koss, Holger; Srouji, Robin G.

    2015-01-01

    The paper presents a study conducted to investigate the influence of geometric scale and flow condition on the wind load coefficients for lattice masts structures. An initial study in 2008 on a full size mast section indicated a possible contingency, which could be used to add equipment...... reflecting model scale behavior than full scale aerodynamics. This reveals the main challenge if for reasons of economic production and operation of telecommunication towers and masts a more accurate wind load description is required: full size testing....... on telecommunication towers without further structural strengthening. This study focuses on the role of scaling. A 1:6 scaled mast model was tested in two different flow conditions and in three layout variations. It was found that scaling does play a large role and that some of the codified loads are in fact more...

  1. Artificial bee colony algorithm for economic load dispatch with wind power energy

    Directory of Open Access Journals (Sweden)

    Safari Amin

    2016-01-01

    Full Text Available This paper presents an efficient Artificial Bee Colony (ABC algorithm for solving large scale economic load dispatch (ELD problems in power networks. To realize the ELD, the valve-point loading effect, system load demand, power losses, ramp rate limits and prohibited operation zones are considered here. Simulations were performed on four different power systems with 3, 6, 15 and 40 generating units and the results are compared with two forms of power systems, one power system is with a wind power generator and other power system is without a wind power generator. The results of this study reveal that the proposed approach is able to find appreciable ELD solutions than those of previous algorithms.

  2. Performance and load data from Mod-0A and Mod-1 wind turbine generators

    Science.gov (United States)

    Spera, D. A.; Janetzke, D. C.

    1982-01-01

    Experimental data, together with supporting analysis, are presented on the power conversion performance and blade loading of large, horizontal-axis wind turbines tested at electric utility sites in the U.S. Four turbine rotor configurations, from 28 to 61 meters in diameter, and data from five test sites are included. Performance data are presented in the form of graphs of power and system efficiency versus free-stream wind speed. Deviations from theoretical performance are analyzed statistically. Power conversion efficiency averaged 0.34 for all tests combined, compared with 0.31 predicted. Round blade tips appeared to improve performance significantly. Cyclic blade loads were normalized to develop load factors which can be used in the design of rotors with rigid hubs.

  3. Linear parameter varying control of wind turbines covering both partial load and full load conditions

    DEFF Research Database (Denmark)

    Østergaard, Kasper Zinck; Stoustrup, Jakob; Brath, Per

    2009-01-01

    This paper considers the design of linear parameter varying (LPV) controllers for wind turbines in order to obtain a multivariable control law that covers the entire nominal operating trajectory.The paper first presents a controller structure for selecting a proper operating trajectory as a funct......This paper considers the design of linear parameter varying (LPV) controllers for wind turbines in order to obtain a multivariable control law that covers the entire nominal operating trajectory.The paper first presents a controller structure for selecting a proper operating trajectory...... as a function of estimated wind speed. The dynamic control law is based on LPV controller synthesis with general parameter dependency by gridding the parameter space.The controller construction can, for medium- to large-scale systems, be difficult from a numerical point of view, because the involved matrix...... operations tend to be ill-conditioned. The paper proposes a controller construction algorithm together with various remedies for improving the numerical conditioning the algorithm.The proposed algorithm is applied to the design of a LPV controller for wind turbines, and a comparison is made with a controller...

  4. Comparison of simulations and offshore measurement data of a prototype of a floating combined wind and wave energy conversion system

    DEFF Research Database (Denmark)

    Yde, Anders; Larsen, Torben J.; Hansen, Anders Melchior

    2015-01-01

    . The numerical model of the platform is based on the aeroelastic code, HAWC2, developed by DTU Wind Energy, which is coupled with a special external system that reads the output generated directly by the wave analysis software, WAMIT. The model also includes models for the dynamic mooring lines as well...... as the turbines non-linear yaw and teeter motion behavior. The main focus on the comparison will be on the statistical trends of the platform motion, mooring loads and turbine loads in measurements and simulations during different operational conditions such as increasing wind speed, wave height and wind...

  5. Short-Term Forecasting of Loads and Wind Power for Latvian Power System: Accuracy and Capacity of the Developed Tools

    Directory of Open Access Journals (Sweden)

    Radziukynas V.

    2016-04-01

    Full Text Available The paper analyses the performance results of the recently developed short-term forecasting suit for the Latvian power system. The system load and wind power are forecasted using ANN and ARIMA models, respectively, and the forecasting accuracy is evaluated in terms of errors, mean absolute errors and mean absolute percentage errors. The investigation of influence of additional input variables on load forecasting errors is performed. The interplay of hourly loads and wind power forecasting errors is also evaluated for the Latvian power system with historical loads (the year 2011 and planned wind power capacities (the year 2023.

  6. Comparison of wind pressure measurements on Silsoe ...

    African Journals Online (AJOL)

    user

    lence and curvature related strain effects and the same have been compared with the full-scale and wind-tunnel data for the present study. Better turbulence models that will be more accurately predict bluff body flow fields and that are numerically stable for complex geometries are of paramount importance if the uses of ...

  7. Detailed Load Analysis of the baseline 5MW DeepWind Concept

    DEFF Research Database (Denmark)

    Verelst, David Robert; Aagaard Madsen, Helge; Kragh, Knud Abildgaard

    that is reported here will be called version 2.2.0. The numbering system has just been introduced at the present design version, but the rst 5MW design called the "baseline design" [1] was developed in 2011 and this will therefore be called version 1.0.0. In this report, the design loads of the DeepWind 5 MW...... turbine are presented. The loads are calculated using Hawc2 (ver 11.8). The turbine controller is implemented according to principles outlined in work package 4 (Turbine operational control), only the normal production part of the controller is implemented. Hence, the calculated design loads only covers...... normal operations. In the Chapter 3 and 2 the modelled design is and simulation scenarios are introduced. In Chapter 5 the estimated loads are presented in the form of plots. In Appendix A the simulated loads are tabulated, and the input data for the numerical HAWC2 model is given in Appendix B....

  8. Simulation of the Impact of New Ocean Surface Wind Measurements on H*Wind Analyses

    Science.gov (United States)

    Miller, Timothy; Atlas, Robert; Black, Peter; Chen, Shuyi; Hood, Robbie; Johnson, James; Jones, Linwood; Ruf, Chris; Uhlhorn, Eric

    2008-01-01

    The H*Wind analysis, a product of the Hurricane Research Division of NOAA's Atlantic Oceanographic and Meteorological Laboratory, brings together wind measurements from a variety of observation platforms into an objective analysis of the distribution of surface wind speeds in a tropical cyclone. This product is designed to improve understanding of the extent and strength of the wind field, and to improve the assessment of hurricane intensity. See http://www.aoml.noaa.gov/hrd/data sub/wind.html. The Hurricane Imaging Radiometer (HIRAD) is a new passive microwave remote sensor for hurricane observations that is currently under development by NASA Marshall Space Flight Center, NOAA Hurricane Research Division, the University of Central Florida and the University of Michigan. HIRAD is being designed to enhance the current real-time airborne ocean surface winds observation capabilities of NOAA and USAF Weather Squadron hurricane hunter aircraft using the operational airbome Stepped Frequency Microwave Radiometer (SFMR). Unlike SFMR, which measures wind speed and rain rate along the ground track directly beneath the aircraft, HIRAD will provide images of the surface wind and rain field over a wide swath (approximately 3 x the aircraft altitude, or approximately 2 km from space). The instrument is described in a separate paper presented at this conference. The present paper describes a set of Observing System Simulation Experiments (OSSEs) in which measurements from the new instrument as well as those from existing instruments (air, surface, and space-based) are simulated from the output of a numerical model from the University of Miami, and those results are used to construct H*Wind analyses. Evaluations will be presented on the relative impact of HIRAD and other instruments on H*Wind analyses, including the use of HIRAD from 2 aircraft altitudes and from a space-based platform.

  9. Wind Turbine Rotor Simulation via CFD Based Actuator Disc Technique Compared to Detailed Measurement

    Directory of Open Access Journals (Sweden)

    Esmail Mahmoodi

    2015-10-01

    Full Text Available In this paper, a generalized Actuator Disc (AD is used to model the wind turbine rotor of the MEXICO experiment, a collaborative European wind turbine project. The AD model as a combination of CFD technique and User Defined Functions codes (UDF, so-called UDF/AD model is used to simulate loads and performance of the rotor in three different wind speed tests. Distributed force on the blade, thrust and power production of the rotor as important designing parameters of wind turbine rotors are focused to model. A developed Blade Element Momentum (BEM theory as a code based numerical technique as well as a full rotor simulation both from the literature are included into the results to compare and discuss. The output of all techniques is compared to detailed measurements for validation, which led us to final conclusions.

  10. Determination of brace forces caused by construction loads and wind loads during bridge construction.

    Science.gov (United States)

    2014-04-01

    The first objective of this study was to develop procedures for determining bracing forces during bridge construction. : Numerical finite element models and analysis techniques were developed for evaluating brace forces induced by construction loads ...

  11. Three-dimensional structure of wind turbine wakes as measured by scanning lidar

    Science.gov (United States)

    Bodini, Nicola; Zardi, Dino; Lundquist, Julie K.

    2017-08-01

    The lower wind speeds and increased turbulence that are characteristic of turbine wakes have considerable consequences on large wind farms: turbines located downwind generate less power and experience increased turbulent loads. The structures of wakes and their downwind impacts are sensitive to wind speed and atmospheric variability. Wake characterization can provide important insights for turbine layout optimization in view of decreasing the cost of wind energy. The CWEX-13 field campaign, which took place between June and September 2013 in a wind farm in Iowa, was designed to explore the interaction of multiple wakes in a range of atmospheric stability conditions. Based on lidar wind measurements, we extend, present, and apply a quantitative algorithm to assess wake parameters such as the velocity deficits, the size of the wake boundaries, and the location of the wake centerlines. We focus on wakes from a row of four turbines at the leading edge of the wind farm to explore variations between wakes from the edge of the row (outer wakes) and those from turbines in the center of the row (inner wakes). Using multiple horizontal scans at different elevations, a three-dimensional structure of wakes from the row of turbines can be created. Wakes erode very quickly during unstable conditions and can in fact be detected primarily in stable conditions in the conditions measured here. During stable conditions, important differences emerge between the wakes of inner turbines and the wakes of outer turbines. Further, the strong wind veer associated with stable conditions results in a stretching of the wake structures, and this stretching manifests differently for inner and outer wakes. These insights can be incorporated into low-order wake models for wind farm layout optimization or for wind power forecasting.

  12. Short-term load and wind power forecasting using neural network-based prediction intervals.

    Science.gov (United States)

    Quan, Hao; Srinivasan, Dipti; Khosravi, Abbas

    2014-02-01

    Electrical power systems are evolving from today's centralized bulk systems to more decentralized systems. Penetrations of renewable energies, such as wind and solar power, significantly increase the level of uncertainty in power systems. Accurate load forecasting becomes more complex, yet more important for management of power systems. Traditional methods for generating point forecasts of load demands cannot properly handle uncertainties in system operations. To quantify potential uncertainties associated with forecasts, this paper implements a neural network (NN)-based method for the construction of prediction intervals (PIs). A newly introduced method, called lower upper bound estimation (LUBE), is applied and extended to develop PIs using NN models. A new problem formulation is proposed, which translates the primary multiobjective problem into a constrained single-objective problem. Compared with the cost function, this new formulation is closer to the primary problem and has fewer parameters. Particle swarm optimization (PSO) integrated with the mutation operator is used to solve the problem. Electrical demands from Singapore and New South Wales (Australia), as well as wind power generation from Capital Wind Farm, are used to validate the PSO-based LUBE method. Comparative results show that the proposed method can construct higher quality PIs for load and wind power generation forecasts in a short time.

  13. Analysis of Damage in Laminated Architectural Glazing Subjected to Wind Loading and Windborne Debris Impact

    Directory of Open Access Journals (Sweden)

    Daniel S. Stutts

    2013-05-01

    Full Text Available Wind loading and windborne debris (missile impact are the two primary mechanisms that result in window glazing damage during hurricanes. Wind-borne debris is categorized into two types: small hard missiles; such as roof gravel; and large soft missiles representing lumber from wood-framed buildings. Laminated architectural glazing (LAG may be used in buildings where impact resistance is needed. The glass plies in LAG undergo internal damage before total failure. The bulk of the published work on this topic either deals with the stress and dynamic analyses of undamaged LAG or the total failure of LAG. The pre-failure damage response of LAG due to the combination of wind loading and windborne debris impact is studied. A continuum damage mechanics (CDM based constitutive model is developed and implemented via an axisymmetric finite element code to study the failure and damage behavior of laminated architectural glazing subjected to combined loading of wind and windborne debris impact. The effect of geometric and material properties on the damage pattern is studied parametrically.

  14. Wind Turbine Pitch Control and Load Mitigation Using an L1 Adaptive Approach

    Directory of Open Access Journals (Sweden)

    Danyong Li

    2014-01-01

    Full Text Available We present an application of L1 adaptive output feedback control design to wind turbine collective pitch control and load mitigation. Our main objective is the design of an L1 output feedback controller without wind speed estimation, ensuring that the generator speed tracks the reference trajectory with robustness to uncertain parameters and time-varying disturbances (mainly the uniform wind disturbance across the wind turbine rotor. The wind turbine model CART (controls advanced research turbine developed by the national renewable energy laboratory (NREL is used to validate the performance of the proposed L1 adaptive controller using the FAST (fatigue, aerodynamics, structures, and turbulence code. A comparative study is also conducted between the proposed controller and the most popular methods in practice: gain scheduling PI (GSPI controls and disturbance accommodating control (DAC methods. The results show better performance of L1 output feedback controller over the other two methods. Moreover, based on the FAST software and LQR analysis in the reference model selection of L1 adaptive controller, tradeoff can be achieved between control performance and loads mitigation.

  15. Calculation of design load for the MOD-5A 7.3 mW wind turbine system

    Science.gov (United States)

    Mirandy, L.; Strain, J. C.

    1995-01-01

    Design loads are presented for the General Electric MOD-SA wind turbine. The MOD-SA system consists of a 400 ft. diameter, upwind, two-bladed, teetered rotor connected to a 7.3 mW variable-speed generator. Fatigue loads are specified in the form of histograms for the 30 year life of the machine, while limit (or maximum) loads have been derived from transient dynamic analysis at critical operating conditions. Loads prediction was accomplished using state of the art aeroelastic analyses developed at General Electric. Features of the primary predictive tool - the Transient Rotor Analysis Code (TRAC) are described in the paper. Key to the load predictions are the following wind models: (1) yearly mean wind distribution; (2) mean wind variations during operation; (3) number of start/shutdown cycles; (4) spatially large gusts; and (5) spatially small gusts (local turbulence). The methods used to develop statistical distributions from load calculations represent an extension of procedures used in past wind programs and are believed to be a significant contribution to Wind Turbine Generator analysis. Test/theory correlations are presented to demonstrate code load predictive capability and to support the wind models used in the analysis. In addition MOD-5A loads are compared with those of existing machines. The MOD-5A design was performed by the General Electric Company, Advanced Energy Program Department, under Contract DEN3-153 with NASA Lewis Research Center and sponsored by the Department of Energy.

  16. Measurement of rotor centre flow direction and turbulence in wind farm environment

    DEFF Research Database (Denmark)

    Friis Pedersen, Troels; Demurtas, Giorgio; Sommer, A.

    2014-01-01

    The measurement of inflow to a wind turbine rotor was made with a spinner anemometer on a 2 MW wind turbine in a wind farm of eight wind turbines. The wind speed, yaw misalignment and flow inclination angle was measured during a five months measurement campaign. Angular measurements were calibrat...

  17. Alternative wind power modeling methods using chronological and load duration curve production cost models

    Energy Technology Data Exchange (ETDEWEB)

    Milligan, M R

    1996-04-01

    As an intermittent resource, capturing the temporal variation in windpower is an important issue in the context of utility production cost modeling. Many of the production cost models use a method that creates a cumulative probability distribution that is outside the time domain. The purpose of this report is to examine two production cost models that represent the two major model types: chronological and load duration cure models. This report is part of the ongoing research undertaken by the Wind Technology Division of the National Renewable Energy Laboratory in utility modeling and wind system integration.

  18. Representativeness of wind measurements in moderately complex terrain

    Science.gov (United States)

    van den Bossche, Michael; De Wekker, Stephan F. J.

    2018-02-01

    We investigated the representativeness of 10-m wind measurements in a 4 km × 2 km area of modest relief by comparing observations at a central site with those at four satellite sites located in the same area. Using a combination of established and new methods to quantify and visualize representativeness, we found significant differences in wind speed and direction between the four satellite sites and the central site. The representativeness of the central site wind measurements depended strongly on surface wind speed and direction, and atmospheric stability. Through closer inspection of the observations at one of the satellite sites, we concluded that terrain-forced flows combined with thermally driven downslope winds caused large biases in wind direction and speed. We used these biases to generate a basic model, showing that terrain-related differences in wind observations can to a large extent be predicted. Such a model is a cost-effective way to enhance an area's wind field determination and to improve the outcome of pollutant dispersion and weather forecasting models.

  19. Simulation of Irregular Waves and Wave Induced Loads on Wind Power Plants in Shallow Water

    Energy Technology Data Exchange (ETDEWEB)

    Trumars, Jenny [Chalmers Univ. of Technology, Goeteborg (Sweden). Dept. of Water Environment Transport

    2004-05-01

    The essay gives a short introduction to waves and discusses the problem with non-linear waves in shallow water and how they effect an offshore wind energy converter. The focus is on the realisation of non-linear waves in the time domain from short-term statistics in the form of a variance density spectrum of the wave elevation. For this purpose the wave transformation from deep water to the near to shore site of a wind energy farm at Bockstigen has been calculated with the use of SWAN (Simulating Waves Near Shore). The result is a wave spectrum, which can be used as input to the realisation. The realisation of waves is done by perturbation theory to the first and second-order. The properties calculated are the wave elevation, water particle velocity and acceleration. The wave heights from the second order perturbation equations are higher than those from the first order perturbation equations. This is also the case for the water particle kinematics. The increase of variance is significant between the first order and the second order realisation. The calculated wave elevation exhibits non-linear features as the peaks become sharper and the troughs flatter. The resulting forces are calculated using Morison's equation. For second order force and base moment there is an increase in the maximum values. The force and base moment are largest approximately at the zero up and down crossing of the wave elevation. This indicates an inertia dominated wave load. So far the flexibility and the response of the structure have not been taken into account. They are, however, of vital importance. For verification of the wave model the results will later on be compared with measurements at Bockstigen off the coast of Gotland in the Baltic Sea.

  20. Wind measurement on the Linth plain; Windmessung in der Linthebene

    Energy Technology Data Exchange (ETDEWEB)

    Langraf, B.

    2003-07-01

    This comprehensive final report for the Swiss Federal Office of Energy (SFOE) presents the results of wind measurements made on the Linth plain, a flat alluvial plain in eastern Switzerland located between mountain ranges. The data, which were collected using temporary measurement masts at two locations are presented in the form of tables, diagrams and maps showing the wind-energy potential of various areas of the plain. The actual measurements are compared with prognoses from a geo-information system. The wind measurement equipment and installations are described, as are the software models for the calculation of wind direction, wind intensity and of a prognosis for energy production. Particular attention was also paid to the question of wind turbulence. Further factors investigated included the possibility of icing-up in winter and the choice of a meteorological station in the neighbourhood with similar characteristics that could be used as a reference station. The report also presents the results of the evaluation of various possible locations for wind turbines on the Linth plain. Visual, noise and shadow-casing factors are considered.

  1. Measurement and Assessment of Flow Quality in Wind Tunnels Project

    Data.gov (United States)

    National Aeronautics and Space Administration — New wind tunnel flow quality test and analysis procedures have been developed and will be used to establish standardized turbulent flow quality measurement...

  2. High-altitude wind prediction and measurement technology assessment

    Science.gov (United States)

    2009-06-30

    The principles and operational characteristics of balloon and radar-based techniques for measuring upper air winds in support of launches and recoveries are presented. Though either a balloon or radar system could serve as a standalone system, the sa...

  3. 3-D Wind and Turbulence Measurement System for UAV Project

    Data.gov (United States)

    National Aeronautics and Space Administration — In situ wind and turbulence measurements play a key role in the support and validation of Earth science missions using spaced-based technology. NASA has been using...

  4. Wind Ressources in Complex Terrain investigated with Synchronized Lidar Measurements

    Science.gov (United States)

    Mann, J.; Menke, R.; Vasiljevic, N.

    2017-12-01

    The Perdigao experiment was performed by a number of European and American universities in Portugal 2017, and it is probably the largest field campaign focussing on wind energy ressources in complex terrain ever conducted. 186 sonic anemometers on 50 masts, 20 scanning wind lidars and a host of other instruments were deployed. The experiment is a part of an effort to make a new European wind atlas. In this presentation we investigate whether scanning the wind speed over ridges in this complex terrain with multiple Doppler lidars can lead to an efficient mapping of the wind resources at relevant positions. We do that by having pairs of Doppler lidars scanning 80 m above the ridges in Perdigao. We compare wind resources obtained from the lidars and from the mast-mounted sonic anemometers at 80 m on two 100 m masts, one on each of the two ridges. In addition, the scanning lidar measurements are also compared to profiling lidars on the ridges. We take into account the fact that the profiling lidars may be biased due to the curvature of the streamlines over the instrument, see Bingol et al, Meteorolog. Z. vol. 18, pp. 189-195 (2009). We also investigate the impact of interruptions of the lidar measurements on the estimated wind resource. We calculate the relative differences of wind along the ridge from the lidar measurements and compare those to the same obtained from various micro-scale models. A particular subject investigated is how stability affects the wind resources. We often observe internal gravity waves with the scanning lidars during the night and we quantify how these affect the relative wind speed on the ridges.

  5. An MSc Course Module: Wind Turbine Measurement Techniques

    DEFF Research Database (Denmark)

    Hansen, Kurt Schaldemose; Pedersen, Knud Ole Helgesen

    2005-01-01

    The 2-year MSc in Wind power engineering at the Technical University of Denmark comprises modules from core engineering teaching and from other modules specifically designed to the MSc. This Note outlines the content of such a specific module on the subject of wind turbine measurement. The lectures......, practical exercises and work related to measurements from an operating 500 kW turbine are described....

  6. Short-term fatigue analysis for tower base of a spar-type wind turbine under stochastic wind-wave loads

    Directory of Open Access Journals (Sweden)

    Haoran Li

    2018-01-01

    Full Text Available Due to integrated stochastic wind and wave loads, the supporting platform of a Floating Offshore Wind Turbine (FOWT has to bear six Degrees of Freedom (DOF motion, which makes the random cyclic loads acting on the structural components, for instance the tower base, more complicated than those on bottom-fixed or land-based wind turbines. These cyclic loads may cause unexpected fatigue damages on a FOWT. This paper presents a study on short-term fatigue damage at the tower base of a 5 MW FOWT with a spar-type platform. Fully coupled time-domain simulations code FAST is used and realistic environment conditions are considered to obtain the loads and structural stresses at the tower base. Then the cumulative fatigue damage is calculated based on rainflow counting method and Miner's rule. Moreover, the effects of the simulation length, the wind-wave misalignment, the wind-only condition and the wave-only condition on the fatigue damage are investigated. It is found that the wind and wave induced loads affect the tower base's axial stress separately and in a decoupled way, and the wave-induced fatigue damage is greater than that induced by the wind loads. Under the environment conditions with rated wind speed, the tower base experiences the highest fatigue damage when the joint probability of the wind and wave is included in the calculation. Moreover, it is also found that 1 h simulation length is sufficient to give an appropriate fatigue damage estimated life for FOWT.

  7. Estimation of the Unsteady Aerodynamic Load on Space Shuttle External Tank Protuberances from a Component Wind Tunnel Test

    Science.gov (United States)

    Panda, Jayatana; Martin, Fred W.; Sutliff, Daniel L.

    2008-01-01

    At the wake of the Columbia (STS-107) accident it was decided to remove the Protuberance Aerodynamic Load (PAL) Ramp that was originally intended to protect various protuberances outside of the Space Shuttle External Tank from high buffet load induced by cross-flows at transonic speed. In order to establish the buffet load without the PAL ramp, a wind tunnel test was conducted where segments of the protuberances were instrumented with dynamic pressure transducers; and power-spectra of sectional lift and drag forces at various span-wise locations between two adjacent support brackets were measured under different cross flow angles, Mach number and other conditions. Additionally, frequency-dependent spatial correlations between the sectional forces were also established. The sectional forces were then adjusted by the correlation length to establish span-averaged spectra of normal and lateral forces that can be suitably "added" to various other unsteady forces encountered by the protuberance. This paper describes the methodology used for calculating the correlation-adjusted power spectrum of the buffet load. A second part of the paper describes wind-tunnel results on the difference in the buffet load on the protuberances with and without the PAL ramp. In general when the ramp height is the same as that of the protuberance height, such as that found on the liquid Oxygen part of the tank, the ramp is found to cause significant reduction of the unsteady aerodynamic load. However, on the liquid Hydrogen part of the tank, where the Oxygen feed-line is far larger in diameter than the height of the PAL ramp, little protection is found to be available to all but the Cable Tray.

  8. Should we build wind farms close to load or invest in transmission to access better wind resources in remote areas? A case study in the MISO region

    International Nuclear Information System (INIS)

    Lamy, Julian V.; Jaramillo, Paulina; Azevedo, Inês L.; Wiser, Ryan

    2016-01-01

    Wind speeds in remote areas are sometimes very high, but transmission costs to access these locations can be prohibitive. We present a conceptual model to estimate the economics of accessing high quality wind resources in remote areas to comply with renewable energy policy targets, and apply the model to the Midwestern grid (MISO) as a case study. We assess the goal of providing 40 TWh of new wind generation while minimizing costs, and include temporal aspects of wind power (variability costs and correlation to market prices) as well as total wind power produced from different farms. We find that building wind farms in North/South Dakota (windiest states) compared to Illinois (less windy, but close to load) would only be economical if the incremental transmission costs to access them were below $360/kW of wind capacity (break-even value). Historically, the incremental transmission costs for wind development in North/South Dakota compared to in Illinois are about twice this value. However, the break-even incremental transmission cost for wind farms in Minnesota/Iowa (also windy states) is $250/kW, which is consistent with historical costs. We conclude that wind development in Minnesota/Iowa is likely more economical to meet MISO renewable targets compared to North/South Dakota or Illinois. - Highlights: •We evaluate the economics of building wind farms in remote areas in MISO. •We present a conceptual wind site selection model to meet 40 TWh of new wind. •We use the model to compare remote windy sites to less windy ones closer to load. •We show break-even transmission costs that would justify remote wind development. •Comparing break-even values to historical costs, MN/IA sites are most economical.

  9. On the Use of Coupled Wind, Wave, and Current Fields in the Simulation of Loads on Bottom-Supported Offshore Wind Turbines during Hurricanes: March 2012 - September 2015

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Eungsoo [Univ. of Texas, Austin, TX (United States); Manuel, Lance [Univ. of Texas, Austin, TX (United States); Curcic, Milan [Univ. of Miami, Coral Gables, FL (United States); Chen, Shuyi S. [Univ. of Miami, Coral Gables, FL (United States); Phillips, Caleb [National Renewable Energy Lab. (NREL), Golden, CO (United States); Veers, Paul [National Renewable Energy Lab. (NREL), Golden, CO (United States)

    2016-06-01

    In the United States, potential offshore wind plant sites have been identified along the Atlantic seaboard and in the Gulf of Mexico. It is imperative that we define external conditions associated with hurricanes and severe winter storms and consider load cases for which wind turbines may need to be designed. We selected two hurricanes, Ike (2008) and Sandy (2012), and investigated the effect these tropical storms would have on bottom-supported offshore wind turbines that were hypothetically in or close to their path as they made landfall. For realistic turbine loads assessment, it is important that the coupled influences of the changing wind, wave, and current fields are simulated throughout the evolution of the hurricanes. We employed a coupled model--specifically, the University of Miami Coupled Model (UMCM)--that integrates atmospheric, wave, and ocean components to produce needed wind, wave, and current data. The wind data are used to generate appropriate vertical wind profiles and full wind velocity fields including turbulence; the current field over the water column is obtained by interpolated discrete output current data; and short-crested irregular second-order waves are simulated using output directional wave spectra from the coupled model. We studied two monopile-supported offshore wind turbines sited in 20 meters of water in the Gulf of Mexico to estimate loads during Hurricane Ike, and a jacket space-frame platform-supported offshore wind turbine sited in 50 meters of water in the mid-Atlantic region to estimate loads during Hurricane Sandy. In this report we discuss in detail how the simulated hurricane wind, wave, and current output data are used in turbine loads studies. In addition, important characteristics of the external conditions are studied, including the relative importance of swell versus wind seas, aerodynamic versus hydrodynamic forces, current velocity effects, yaw control options for the turbine, hydrodynamic drag versus inertia forces

  10. Effect of load eccentricity and stress level on monopile support for offshore wind turbines

    DEFF Research Database (Denmark)

    Klinkvort, Rasmus Tofte; Hededal, Ole

    2014-01-01

    on which load is applied with a large eccentricity. With centrifuge tests as the basis, this paper investigates the behaviour of a rigid pile loaded with a high eccentricity. A test series was carried out to simulate idealized monotonic load cases for monopiles supporting an offshore wind turbine...... analysis and Rankine’s passive earth pressure coefficient as a normalization parameter. The normalized ultimate soil resistance was unaffected by acceleration level and load eccentricity, indicating that the failure mechanism was the same for all tests. Based on the centrifuge tests, a reformulation...... of soil–pile interaction curves is presented. The normalized initial stiffness of the soil–pile resistance curves was seen to increase linearly with depth in the centrifuge tests. The reformulation differs from current guidelines in terms of the shape of the interaction curve and magnitude of ultimate...

  11. Development of SMA Actuated Morphing Airfoil for Wind Turbine Load Alleviation

    Science.gov (United States)

    Karakalas, A.; Machairas, T.; Solomou, A.; Riziotis, V.; Saravanos, D.

    Wind turbine rotor upscaling has entered a range of rotor diameters where the blade structure cannot sustain the increased aerodynamic loads without novel load alleviation concepts. Research on load alleviation using morphing blade sections is presented. Antagonistic shape memory alloy (SMA) actuators are implemented to deflect the section trailing edge (TE) to target shapes and target time-series relating TE movement with changes in lift coefficient. Challenges encountered by the complex thermomechanical response of morphing section and the enhancement of SMA transient response to achieve frequencies meaningful for aerodynamic load alleviation are addressed. Using a recently developed finite element for SMA actuators [1], actuator configurations are considered for fast cooling and heating cycles. Numerical results quantify the attained ranges of TE angle movement, the moving time period and the developed stresses. Estimations of the attained variations of lift coefficient vs. time are also presented to assess the performance of the morphing section.

  12. Load consequences when sweeping blades - A case study of a 5 MW pitch controlled wind turbine

    Energy Technology Data Exchange (ETDEWEB)

    Verelst, D.R.S.; Larsen, Torben J.

    2010-08-15

    The generic 5 MW NREL wind turbine model is used in Risoe's aeroelastic simulator HAWC2 to investigate 120 different swept blade configurations (forward and backward sweep). Sensitivity for 2 different controllers is considered as well. Backward sweep results in a pitch to feather torsional moment of the blade, effectively reducing blade twist angles under increased loading. This behaviour results in decreased flap-wise fatigue and extreme loads, an increase for edge-wise fatigue loading and status quo or slight decrease in extreme loads (depending on the controller). Tower base and shaft-end bending moments are reduced as well. Forward sweep leads to an increase in angle of attack under loading. For a pitch controlled turbine this leads to an increase in fatigue and extreme loading in all cases. A controller inflicted instability is present for the more extreme forward swept cases. Due to the shape of considered sweep curves, an inherent and significant increase in torsional blade root bending moment is noted. A boomerang shaped sweep curve is proposed to counteract this problematic increased loading. Controller sensitivity shows that adding sweep affects some loadings differently. Power output is reduced for backward sweep since the blade twist is optimized as a rigid structure, ignoring the torsional deformations which for a swept blade can be significant. (author)

  13. Structural Load Alleviation Applied to Next Generation Aircraft and Wind Turbines

    Science.gov (United States)

    Frost, Susan

    2011-01-01

    Reducing the environmental impact of aviation is a goal of the Subsonic Fixed Wing Project under the Fundamental Aeronautics Program of NASAs Aeronautics Research Mission Directorate. Environmental impact of aviation is being addressed by novel aircraft configurations and materials that reduce aircraft weight and increase aerodynamic efficiency. NASA is developing tools to address the challenges of increased airframe flexibility created by wings constructed with reduced structural material and novel light-weight materials. This talk will present a framework and demonstration of a flight control system using optimal control allocation with structural load feedback and constraints to achieve safe aircraft operation. As wind turbines age, they become susceptible to many forms of blade degradation. Results will be presented on work in progress that uses adaptive contingency control for load mitigation in a wind turbine simulation with blade damage progression modeled.

  14. Assessment of extreme design loads for modern wind turbines using the probabilistic approach

    DEFF Research Database (Denmark)

    Abdallah, Imad

    as necessary, but no stronger [Veldkamp, 2006]. The original contributions of this research were:  • A comprehensive list of sources of uncertainties affecting the prediction of extreme loads on a wind turbine. Such a list is indeed subjective and subject to scrutiny and updating depending on a researcher......’s, scientist’s and engineer’s background, know-how and experiences.  • A fully encompassing stochastic model of aerofoil aerodynamic lift and drag coefficients, followed by a quantification of the effect of aerodynamic uncertainties on the extreme loads and an optimization of the partial safety factors...

  15. Optimized Power Dispatch in Wind Farms for Power Maximizing Considering Fatigue Loads

    DEFF Research Database (Denmark)

    Zhang, Baohua; N. Soltani, Mohsen; Hu, Weihao

    2018-01-01

    load of the shafts and the towers within a certain range from the values using traditional strategy, which adopts maximum power point tracking (MPPT) control for each WT. A WT derating control strategy is included in the WT controller and the fatigue load for the tower and shaft is evaluated offline...... at a series of turbulence intensity, mean wind speed and active power reference to form a lookup table, which is used for the WF control. The proposed strategy is compared with WT MPPT control strategy and WF MPPT control strategy. The simulation results show the effectiveness of the proposed strategy....

  16. Passive A-band Wind Sounder (PAWS) for measuring tropospheric wind velocity profile

    Science.gov (United States)

    Miecznik, Grzegorz; Pierce, Robert; Huang, Pei; Slaymaker, Philip A.; Kaptchen, Paul; Roark, Shane; Johnson, Brian R.; Heath, Donald F.

    2007-09-01

    The Passive A-Band Wind Sounder (PAWS) was funded through NASA's Instrument Incubator Program (IIP) to determine the feasibility of measuring tropospheric wind speed profiles from Doppler shifts in absorption O II A-band. It is being pursued as a low-cost and low-risk alternative capable of providing better wind data than is currently available. The instrument concept is adapted from the Wind Imaging Interferometer (WINDII) sensor on the Upper Atmosphere Research Satellite. The operational concept for PAWS is to view an atmospheric limb over an altitude range from the surface to 20 km with a Doppler interferometer in a sun-synchronous low-earth orbit. Two orthogonal views of the same sampling volume will be used to resolve horizontal winds from measured line-of-sight winds. A breadboard instrument was developed to demonstrate the measurement approach and to optimize the design parameters for the subsequent engineering unit and future flight sensor. The breadboard instrument consists of a telescope, collimator, filter assembly, and Michelson interferometer. The instrument design is guided by a retrieval model, which helps to optimize key parameters, spectral filter and optical path difference in particular.

  17. Wind, waves, and wing loading: Morphological specialization may limit range expansion of endangered albatrosses

    Science.gov (United States)

    Suryan, R.M.; Anderson, D.J.; Shaffer, S.A.; Roby, D.D.; Tremblay, Y.; Costa, D.P.; Sievert, P.R.; Sato, F.; Ozaki, K.; Balogh, G.R.; Nakamura, N.

    2008-01-01

    Among the varied adaptations for avian flight, the morphological traits allowing large-bodied albatrosses to capitalize on wind and wave energy for efficient long-distance flight are unparalleled. Consequently, the biogeographic distribution of most albatrosses is limited to the windiest oceanic regions on earth; however, exceptions exist. Species breeding in the North and Central Pacific Ocean (Phoebastria spp.) inhabit regions of lower wind speed and wave height than southern hemisphere genera, and have large intrageneric variation in body size and aerodynamic performance. Here, we test the hypothesis that regional wind and wave regimes explain observed differences in Phoebastria albatross morphology and we compare their aerodynamic performance to representatives from the other three genera of this globally distributed avian family. In the North and Central Pacific, two species (short-tailed P. albatrus and waved P. irrorata) are markedly larger, yet have the smallest breeding ranges near highly productive coastal upwelling systems. Short-tailed albatrosses, however, have 60% higher wing loading (weight per area of lift) compared to waved albatrosses. Indeed, calculated aerodynamic performance of waved albatrosses, the only tropical albatross species, is more similar to those of their smaller congeners (black-footed P. nigripes and Laysan P. immutabilis), which have relatively low wing loading and much larger foraging ranges that include central oceanic gyres of relatively low productivity. Globally, the aerodynamic performance of short-tailed and waved albatrosses are most anomalous for their body sizes, yet consistent with wind regimes within their breeding season foraging ranges. Our results are the first to integrate global wind and wave patterns with albatross aerodynamics, thereby identifying morphological specialization that may explain limited breeding ranges of two endangered albatross species. These results are further relevant to understanding past and

  18. Wind, waves, and wing loading: morphological specialization may limit range expansion of endangered albatrosses.

    Directory of Open Access Journals (Sweden)

    Robert M Suryan

    Full Text Available Among the varied adaptations for avian flight, the morphological traits allowing large-bodied albatrosses to capitalize on wind and wave energy for efficient long-distance flight are unparalleled. Consequently, the biogeographic distribution of most albatrosses is limited to the windiest oceanic regions on earth; however, exceptions exist. Species breeding in the North and Central Pacific Ocean (Phoebastria spp. inhabit regions of lower wind speed and wave height than southern hemisphere genera, and have large intrageneric variation in body size and aerodynamic performance. Here, we test the hypothesis that regional wind and wave regimes explain observed differences in Phoebastria albatross morphology and we compare their aerodynamic performance to representatives from the other three genera of this globally distributed avian family. In the North and Central Pacific, two species (short-tailed P. albatrus and waved P. irrorata are markedly larger, yet have the smallest breeding ranges near highly productive coastal upwelling systems. Short-tailed albatrosses, however, have 60% higher wing loading (weight per area of lift compared to waved albatrosses. Indeed, calculated aerodynamic performance of waved albatrosses, the only tropical albatross species, is more similar to those of their smaller congeners (black-footed P. nigripes and Laysan P. immutabilis, which have relatively low wing loading and much larger foraging ranges that include central oceanic gyres of relatively low productivity. Globally, the aerodynamic performance of short-tailed and waved albatrosses are most anomalous for their body sizes, yet consistent with wind regimes within their breeding season foraging ranges. Our results are the first to integrate global wind and wave patterns with albatross aerodynamics, thereby identifying morphological specialization that may explain limited breeding ranges of two endangered albatross species. These results are further relevant to

  19. LIDAR and SODAR Measurements of Wind Speed and Direction in Upland Terrain for Wind Energy Purposes

    Directory of Open Access Journals (Sweden)

    Eamon McKeogh

    2011-08-01

    Full Text Available Detailed knowledge of the wind resource is necessary in the developmental and operational stages of a wind farm site. As wind turbines continue to grow in size, masts for mounting cup anemometers—the accepted standard for resource assessment—have necessarily become much taller, and much more expensive. This limitation has driven the commercialization of two remote sensing (RS tools for the wind energy industry: The LIDAR and the SODAR, Doppler effect instruments using light and sound, respectively. They are ground-based and can work over hundreds of meters, sufficient for the tallest turbines in, or planned for, production. This study compares wind measurements from two commercial RS instruments against an instrumented mast, in upland (semi-complex terrain typical of where many wind farms are now being installed worldwide. With appropriate filtering, regression analyses suggest a good correlation between the RS instruments and mast instruments: The RS instruments generally recorded lower wind speeds than the cup anemometers, with the LIDAR more accurate and the SODAR more precise.

  20. Lifetime prediction of towers with respect to lateral and longitudinal wind load

    Czech Academy of Sciences Publication Activity Database

    Pospíšil, Stanislav; Hračov, Stanislav; Lahodný, J.; Janata, V.; Urushadze, Shota

    2014-01-01

    Roč. 55, č. 2 (2014), s. 117-126 ISSN 1028-365X R&D Projects: GA MPO(CZ) FR-TI3/654; GA ČR(CZ) GA103/09/0094; GA ČR(CZ) GP13-41574P Institutional support: RVO:68378297 Keywords : lifetime prediction * spectrum * towers * wind load * fatigue Subject RIV: JM - Building Engineering http://www.iass-structures.org/index.cfm/journal.article?aID=702

  1. Arctic wind energy

    International Nuclear Information System (INIS)

    Peltola, E.; Holttinen, H.; Marjaniemi, M.; Tammelin, B.

    1998-01-01

    Arctic wind energy research was aimed at adapting existing wind technologies to suit the arctic climatic conditions in Lapland. Project research work included meteorological measurements, instrument development, development of a blade heating system for wind turbines, load measurements and modelling of ice induced loads on wind turbines, together with the development of operation and maintenance practices in arctic conditions. As a result the basis now exists for technically feasible and economically viable wind energy production in Lapland. New and marketable products, such as blade heating systems for wind turbines and meteorological sensors for arctic conditions, with substantial export potential, have also been developed. (orig.)

  2. Arctic wind energy

    Energy Technology Data Exchange (ETDEWEB)

    Peltola, E. [Kemijoki Oy (Finland); Holttinen, H.; Marjaniemi, M. [VTT Energy, Espoo (Finland); Tammelin, B. [Finnish Meteorological Institute, Helsinki (Finland)

    1998-12-31

    Arctic wind energy research was aimed at adapting existing wind technologies to suit the arctic climatic conditions in Lapland. Project research work included meteorological measurements, instrument development, development of a blade heating system for wind turbines, load measurements and modelling of ice induced loads on wind turbines, together with the development of operation and maintenance practices in arctic conditions. As a result the basis now exists for technically feasible and economically viable wind energy production in Lapland. New and marketable products, such as blade heating systems for wind turbines and meteorological sensors for arctic conditions, with substantial export potential, have also been developed. (orig.)

  3. The sound power measurement and certification of wind turbines

    International Nuclear Information System (INIS)

    MacKinnon, A.; Henderson, R.

    1992-01-01

    It is anticipated that there will be a substantial growth in the exploitation of renewable energy from the wind over the next few years. A major factor in this expected growth is the environmental acceptance or otherwise of wind turbines and in particular their acoustic characteristics. It is generally accepted within the turbine community that reliable methods of measuring and quantifying a turbine's acoustic signature are essential if this exploitation is to be realised. This paper will seek to review current practice both in the UK and further afield and will describe the development of a practical and reliable test method, which will aid the wind turbine Manufacturer, Developer and Planner. (author)

  4. Cup anemometer response to the wind turbulence-measurement of the horizontal wind variance

    Directory of Open Access Journals (Sweden)

    S. Yahaya

    2004-11-01

    Full Text Available This paper presents some dynamic characteristics of an opto-electronic cup anemometer model in relation to its response to the wind turbulence. It is based on experimental data of the natural wind turbulence measured both by an ultrasonic anemometer and two samples of the mentioned cup anemometer. The distance constants of the latter devices measured in a wind tunnel are in good agreement with those determined by the spectral analysis method proposed in this study. In addition, the study shows that the linear compensation of the cup anemometer response, beyond the cutoff frequency, is limited to a given frequency, characteristic of the device. Beyond this frequency, the compensation effectiveness relies mainly on the wind characteristics, particularly the direction variability and the horizontal turbulence intensity. Finally, this study demonstrates the potential of fast cup anemometers to measure some turbulence parameters (like wind variance with errors of the magnitude as those deriving from the mean speed measurements. This result proves that fast cup anemometers can be used to assess some turbulence parameters, especially for long-term measurements in severe climate conditions (icing, snowing or sandy storm weathers.

  5. Wind gust measurements using pulsed Doppler wind-lidar: comparison of direct and indirect techniques

    DEFF Research Database (Denmark)

    wind vector, we need information from at least three different lines of sight pointing towards different directions. The instrument sensitivity depends on the amount of aerosol present and the velocity measurement uncertainty is directly related to the amount of signal. With the commercial lidars...... traditionally used today it takes several seconds to measure each line of sight with sufficient sensitivity and therefore the temporal resolution of the wind measurement is of the order of tens of seconds, which is not sufficient for gusts. Here we deploy a fast scanning lidar (temporal resolution for a scan...

  6. Study of Flexible Load Dispatch to Improve the Capacity of Wind Power Absorption

    Science.gov (United States)

    Yunlei, Yang; Shifeng, Zhang; Xiao, Chang; Da, Lei; Min, Zhang; Jinhao, Wang; Shengwen, Li; Huipeng, Li

    2017-05-01

    The dispatch method which track the trend of load demand by arranging the generation scheme of controllable hydro or thermal units faces great difficulties and challenges. With the increase of renewable energy sources such as wind power and photovoltaic power introduced to grid, system has to arrange much more spinning reserve units to compensate the unbalanced power. How to exploit the peak-shaving potential of flexible load which can be shifted with time or storage energy has become many scholars’ research direction. However, the modelling of different kinds of load and control strategy is considerably difficult, this paper choose the Air Conditioner with compressor which can storage energy in fact to study. The equivalent thermal parameters of Air Conditioner has been established. And with the use of “loop control” strategies, we can predict the regulated power of Air Conditioner. Then we established the Gen-Load optimal scheduling model including flexible load based on traditional optimal scheduling model. At last, an improved IEEE-30 case is used to verify. The result of simulation shows that flexible load can fast-track renewable power changes. More than that, with flexible load and reasonable incentive method to consumers, the operating cost of the system can be greatly cut down.

  7. Valence of wind power, photovoltaic and peak-load power plants as a part of the entire electricity system

    International Nuclear Information System (INIS)

    Schüppel, A.

    2014-01-01

    The transition to a higher share of renewable energy sources in the electricity sector leads to a multitude of challenges for the current electricity system. Within this thesis, the development of wind power and photovoltaics generation capacities in Germany is analysed based on the evaluation of technical and economic criteria. In order to derive those criteria, different scenarios with a separated and combined increase of wind and photovoltaics capacity are simulated using the model ATLANTIS. The results are compared to a reference scenario without additional wind and PV capacities. Furthermore, the value and functionality of the energy only market based on economic methods, as well as the value of peak load power plants based on opportunity costs are determined. The results of this thesis show, that the current market system is able to gain an additional annual welfare of four to six billion Euro at the best. This result shows that the task of optimising the power plant dispatch is well fulfilled by the current market design. However, the effects, e.g. fuel costs, which may influence this margin. The value of wind power and photovoltaics within the overall electricity system can be derived from the effort which is necessary to integrate these generation technologies into the existing system, and the changes in total costs of electricity generation. Based on the evaluation of time dependencies (seasonality of energy yield from wind and PV) as well as the development of total generation costs, the conclusion can be drawn that wind power is the more suitable RES generation technology for Germany. However, when it comes to grid integration measures, PV shows better results due to a higher generation potential in Southern Germany, which leads to a higher degree of utilisation. Therefore, there is no need to transport electricity from Northern to Southern Germany as it is the case with wind power. A common expansion of wind power and photovoltaics even shows slight

  8. Long-period gratings for selective monitoring of loads on a wind turbine blade.

    Science.gov (United States)

    Glavind, L; Buggy, S; Canning, J; Gao, S; Cook, K; Luo, Y; Peng, G D; Skipper, B F; Kristensen, M

    2014-06-20

    An optical fiber sensor based on long-period gratings (LPG) for selective measurements of flap- and edge-wise bending of a wind turbine blade is presented. Two consecutive LPGs separated by 40 mm interfere to improve resolution and reduce noise in a D-shaped fiber. The mode profile of the device was characterized experimentally to provide a model describing the mode couplings. The sensor was tested on a wind turbine blade.

  9. Noise measurement at wind power plants; Geraeuschmessung an Windenergieanlagen

    Energy Technology Data Exchange (ETDEWEB)

    Schoene, Ralph [Cirrus Research plc, Frankfurt am Main (Germany)

    2012-09-15

    Wind energy is a supporting pillar of the energy transition. For further expansion, it is important to reduce prejudices, for example by measurements as precise as possible and assessments of the often unobjectively discussed noise emissions. These measurements are based on instruments which can analyze and measure low-frequency sound.

  10. Comparison of Simulations and Offshore Measurement Data of a Combined Floating Wind and Wave Energy Demonstration Platform

    DEFF Research Database (Denmark)

    Yde, Anders; Larsen, Torben J.; Hansen, Anders Melchior

    2015-01-01

    In this paper, results from comparisons of simulations and measured offshore data from a floating combined wind and wave energy conversion system are presented. The numerical model of the platform is based on the aeroelastic code, HAWC2, developed by DTU Wind Energy, which is coupled with a special...... external system that reads the output generated directly by the wave analysis software WAMIT. The main focus of the comparison is on the statistical trends of the platform motion, mooring loads, and turbine loads in measurements and simulations during different operational conditions. Finally, challenges...

  11. Isolated systems with wind power. Results of measurements in Egypt

    DEFF Research Database (Denmark)

    Bindner, Henrik W.; Saleh, L.; Hafiez, S.A.

    2001-01-01

    The objective of the measurements were to characterise different types of consumer loads in order to be able to construct load patterns to be used in feasibility studies where the available data often will be incomplete, not available or not existing. Measurements have been carried out at five di...

  12. Wave loads on foundations for wind turbines. A literature survey; Vaaglaster paa fundament till vindkraftverk - systemdynamik och utmattning: Litteraturstudie

    Energy Technology Data Exchange (ETDEWEB)

    Carlen, Ingemar

    2001-05-01

    This report is an overview of literature covering the influence of wave loads on foundations for wind power plants. Relevant subjects are wave motion, wave forces on slender structures, wave statistics for the Swedish coast together with planning and certification.

  13. Measurements of Coastal Winds and Temperature. Sensor Evaluation, Data Quality, and Wind Structures

    Energy Technology Data Exchange (ETDEWEB)

    Heggem, Tore

    1997-12-31

    The long Norwegian coastline has excellent sites for wind power production. This thesis contains a documentation of a measurement station for maritime meteorological data at the coast of Mid-Norway, and analysis of temperature and wind data. It discusses experience with different types of wind speed and wind direction sensors. Accurate air temperature measurements are essential to obtain information about the stability of the atmosphere, and a sensor based on separately calibrated thermistors is described. The quality of the calibrations and the measurements is discussed. A database built up from measurements from 1982 to 1995 has been available. The data acquisition systems and the programs used to read the data are described, as well as data control and gap-filling methods. Then basic statistics from the data like mean values and distributions are given. Quality control of the measurements with emphasis on shade effects from the masts and direction alignment is discussed. The concept of atmospheric stability is discussed. The temperature profile tends to change from unstable to slightly stable as maritime winds passes land. Temperature spectra based on two-year time series are presented. Finally, there is a discussion of long-term turbulence spectra calculated from 14 years of measurements. The lack of a gap in the one-hour region of the spectra is explained from the overweight of unstable atmospheric conditions in the dominating maritime wind. Examples of time series with regular 40-minute cycles, and corresponding effect spectra are given. The validity of local lapse rate as a criterion of atmospheric stability is discussed. 34 refs., 86 figs., 11 tabs.

  14. Real-time POD-CFD Wind-Load Calculator for PV Systems

    Energy Technology Data Exchange (ETDEWEB)

    Huayamave, Victor [Centecorp; Divo, Eduardo [Centecorp; Ceballos, Andres [Centecorp; Barriento, Carolina [Centecorp; Stephen, Barkaszi [FSEC; Hubert, Seigneur [FSEC

    2014-03-21

    The primary objective of this project is to create an accurate web-based real-time wind-load calculator. This is of paramount importance for (1) the rapid and accurate assessments of the uplift and downforce loads on a PV mounting system, (2) identifying viable solutions from available mounting systems, and therefore helping reduce the cost of mounting hardware and installation. Wind loading calculations for structures are currently performed according to the American Society of Civil Engineers/ Structural Engineering Institute Standard ASCE/SEI 7; the values in this standard were calculated from simplified models that do not necessarily take into account relevant characteristics such as those from full 3D effects, end effects, turbulence generation and dissipation, as well as minor effects derived from shear forces on installation brackets and other accessories. This standard does not include provisions that address the special requirements of rooftop PV systems, and attempts to apply this standard may lead to significant design errors as wind loads are incorrectly estimated. Therefore, an accurate calculator would be of paramount importance for the preliminary assessments of the uplift and downforce loads on a PV mounting system, identifying viable solutions from available mounting systems, and therefore helping reduce the cost of the mounting system and installation. The challenge is that although a full-fledged three-dimensional computational fluid dynamics (CFD) analysis would properly and accurately capture the complete physical effects of air flow over PV systems, it would be impractical for this tool, which is intended to be a real-time web-based calculator. CFD routinely requires enormous computation times to arrive at solutions that can be deemed accurate and grid-independent even in powerful and massively parallel computer platforms. This work is expected not only to accelerate solar deployment nationwide, but also help reach the SunShot Initiative goals

  15. Effect of Coupled Non linear Wave Kinematics and Soil Flexibility on the Design Loads of Offshore Wind Turbines

    DEFF Research Database (Denmark)

    Kim, Taeseong; Natarajan, Anand

    2013-01-01

    The design driving loads on offshore wind turbine monopile support structures at water depths of 35m, which are beyond current monopile installation depths, are derived based on fully coupled aerohydroelastic simulations of the wind turbine in normal operation and in storm conditions in the prese...

  16. Advances in the Assessment of Wind Turbine Operating Extreme Loads via More Efficient Calculation Approaches

    Energy Technology Data Exchange (ETDEWEB)

    Graf, Peter; Damiani, Rick R.; Dykes, Katherine; Jonkman, Jason M.

    2017-01-09

    A new adaptive stratified importance sampling (ASIS) method is proposed as an alternative approach for the calculation of the 50 year extreme load under operational conditions, as in design load case 1.1 of the the International Electrotechnical Commission design standard. ASIS combines elements of the binning and extrapolation technique, currently described by the standard, and of the importance sampling (IS) method to estimate load probability of exceedances (POEs). Whereas a Monte Carlo (MC) approach would lead to the sought level of POE with a daunting number of simulations, IS-based techniques are promising as they target the sampling of the input parameters on the parts of the distributions that are most responsible for the extreme loads, thus reducing the number of runs required. We compared the various methods on select load channels as output from FAST, an aero-hydro-servo-elastic tool for the design and analysis of wind turbines developed by the National Renewable Energy Laboratory (NREL). Our newly devised method, although still in its infancy in terms of tuning of the subparameters, is comparable to the others in terms of load estimation and its variance versus computational cost, and offers great promise going forward due to the incorporation of adaptivity into the already powerful importance sampling concept.

  17. Planetary Load Sharing in Three-Point- Mounted Wind Turbine Gearboxes: Preprint

    Energy Technology Data Exchange (ETDEWEB)

    Guo, Yi [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Keller, Jonathan A [National Renewable Energy Laboratory (NREL), Golden, CO (United States)

    2017-09-15

    Wind turbine gearboxes do not achieve their expected design life. The cost of gearbox replacements and rebuilds and the downtime associated with these failures increase the cost of wind energy. In 2007, the U.S. Department of Energy established the National Renewable Energy Laboratory (NREL) Gearbox Reliability Collaborative (GRC). Its goals are to understand the root causes of premature gearbox failures and improve their reliability. To date, the GRC has focused on a 750-kW drivetrain with a three-stage, three-point-mounted gearbox. A nonproprietary version of the gearbox containing CRBs with C3 clearances in the planetary stage was customized. Two of these gearboxes, GB1 and GB2, were manufactured and then tested in the National Wind Technology Center's 2.5-MW dynamometer and in the field. Major GRC findings include the detrimental effect of rotor moments on planetary load sharing and predicted fatigue, and the risk of bearing sliding in low-torque conditions for three-point configuration drivetrains. Based on the knowledge gained from testing and analysis of the original design, the GRC gearbox was redesigned to improve its load-sharing characteristics and predicted fatigue. This new gearbox is named GB3. As shown in Figure 1, its key improvement is the incorporation of preloaded TRBs that support the planet carrier and planets. Roller loads can be optimized and bearing life maximized with a small preload [4]. These preloaded bearings, along with interference-fitted planet pins, improve alignments and load-sharing characteristics. A semi-integrated planet bearing design also increases capacity and eliminates outer race fretting. Romax Technology, with Powertrain Engineers and the Timken Company (Timken), completed the redesign. Timken manufactured and instrumented the planet gears and bearings. Brad Foote Gearing manufactured the other gearing and assembled the gearbox.

  18. Spectral tensor parameters for wind turbine load modeling from forested and agricultural landscapes

    DEFF Research Database (Denmark)

    Chougule, Abhijit S.; Mann, Jakob; Segalini, A.

    2015-01-01

    A velocity spectral tensor model was evaluated from the single-point measurements of wind speed. The model contains three parameters representing the dissipation rate of specific turbulent kinetic energy, a turbulence length scale and the turbulence anisotropy. Sonic anemometer measurements taken...

  19. Energy Coordinative Optimization of Wind-Storage-Load Microgrids Based on Short-Term Prediction

    Directory of Open Access Journals (Sweden)

    Changbin Hu

    2015-02-01

    Full Text Available According to the topological structure of wind-storage-load complementation microgrids, this paper proposes a method for energy coordinative optimization which focuses on improvement of the economic benefits of microgrids in the prediction framework. First of all, the external characteristic mathematical model of distributed generation (DG units including wind turbines and storage batteries are established according to the requirements of the actual constraints. Meanwhile, using the minimum consumption costs from the external grid as the objective function, a grey prediction model with residual modification is introduced to output the predictive wind turbine power and load at specific periods. Second, based on the basic framework of receding horizon optimization, an intelligent genetic algorithm (GA is applied to figure out the optimum solution in the predictive horizon for the complex non-linear coordination control model of microgrids. The optimum results of the GA are compared with the receding solution of mixed integer linear programming (MILP. The obtained results show that the method is a viable approach for energy coordinative optimization of microgrid systems for energy flow and reasonable schedule. The effectiveness and feasibility of the proposed method is verified by examples.

  20. Time Accurate Unsteady Pressure Loads Simulated for the Space Launch System at a Wind Tunnel Condition

    Science.gov (United States)

    Alter, Stephen J.; Brauckmann, Gregory J.; Kleb, Bil; Streett, Craig L; Glass, Christopher E.; Schuster, David M.

    2015-01-01

    Using the Fully Unstructured Three-Dimensional (FUN3D) computational fluid dynamics code, an unsteady, time-accurate flow field about a Space Launch System configuration was simulated at a transonic wind tunnel condition (Mach = 0.9). Delayed detached eddy simulation combined with Reynolds Averaged Naiver-Stokes and a Spallart-Almaras turbulence model were employed for the simulation. Second order accurate time evolution scheme was used to simulate the flow field, with a minimum of 0.2 seconds of simulated time to as much as 1.4 seconds. Data was collected at 480 pressure taps at locations, 139 of which matched a 3% wind tunnel model, tested in the Transonic Dynamic Tunnel (TDT) facility at NASA Langley Research Center. Comparisons between computation and experiment showed agreement within 5% in terms of location for peak RMS levels, and 20% for frequency and magnitude of power spectral densities. Grid resolution and time step sensitivity studies were performed to identify methods for improved accuracy comparisons to wind tunnel data. With limited computational resources, accurate trends for reduced vibratory loads on the vehicle were observed. Exploratory methods such as determining minimized computed errors based on CFL number and sub-iterations, as well as evaluating frequency content of the unsteady pressures and evaluation of oscillatory shock structures were used in this study to enhance computational efficiency and solution accuracy. These techniques enabled development of a set of best practices, for the evaluation of future flight vehicle designs in terms of vibratory loads.

  1. Flight Load Assessment for Light Aircraft Landing Trajectories in Windy Atmosphere and Near Wind Farms

    Directory of Open Access Journals (Sweden)

    Carmine Varriale

    2018-04-01

    Full Text Available This work focuses on the wake encounter problem occurring when a light, or very light, aircraft flies through or nearby a wind turbine wake. The dependency of the aircraft normal load factor on the distance from the turbine rotor in various flight and environmental conditions is quantified. For this research, a framework of software applications has been developed for generating and controlling a population of flight simulation scenarios in presence of assigned wind and turbulence fields. The JSBSim flight dynamics model makes use of several autopilot systems for simulating a realistic pilot behavior during navigation. The wind distribution, calculated with OpenFOAM, is a separate input for the dynamic model and is considered frozen during each flight simulation. The aircraft normal load factor during wake encounters is monitored at different distances from the rotor, aircraft speeds, rates of descent and crossing angles. Based on these figures, some preliminary guidelines and recommendations on safe encounter distances are provided for general aviation aircraft, with considerations on pilot comfort and flight safety. These are needed, for instance, when an accident risk assessment study is required for flight in proximity of aeolic parks. A link to the GitHub code repository is provided.

  2. Preliminary study of inphase gusts and moment force wind loads over the first 150 meters at KSC, Florida

    Science.gov (United States)

    Kaufman, J. W.

    1985-01-01

    A mathematical/statistical analysis of inphase gusts and wind velocity moment forces over the first 150 m at the Kennedy Space Center (KSC) is presented. The wind velocity profile data were acquired at the KSC 150 m ground wind tower. The results show that planetary boundary layer (PBL) winds can sustain near peak speeds for periods up to 60 sec and longer. This is proven from calculating the autocorrelation functions of moment forces for several 10 min cases of wind profile data. The results show that lower atmospheric planetary boundary layer winds have periodic variations for long periods of time. This flow characteristic is valuable as aerospace vehicle engineering and design criteria where wind loading must be determined.

  3. Measured wind speed trends on the west coast of Canada

    Science.gov (United States)

    Tuller, Stanton E.

    2004-09-01

    Trends in measured wind speed are discussed for four stations on the west coast of Canada. Periods of record vary with the station. They begin in the late 1940s or the 1950s and run through to the early to mid 1990s. The most prominent feature of the time series was a decline in mean annual and winter wind speeds at Cape St James, Victoria International Airport, and Vancouver International Airport during the middle portion of the record. Declines in mean annual wind speed are matched by increases in the percentage of calms and decreases in high wind speed observations. The pressure gradient between Victoria, Vancouver and Comox, the Pacific North American index, the Pacific decadal oscillation index, and other climate elements in British Columbia and the northwestern USA show trends at roughly the same time, indicating a natural cause of the wind speed decrease. Comox Airport mean wind speeds increased, however, perhaps the result of reduced friction in the vicinity of the anemometer outweighing the decrease in the regional pressure gradient.

  4. Thermal effects influencing measurements in a supersonic blowdown wind tunnel

    Directory of Open Access Journals (Sweden)

    Vuković Đorđe S.

    2016-01-01

    Full Text Available During a supersonic run of a blowdown wind tunnel, temperature of air in the test section drops which can affect planned measurements. Adverse thermal effects include variations of the Mach and Reynolds numbers, variation of airspeed, condensation of moisture on the model, change of characteristics of the instrumentation in the model, et cetera. Available data on thermal effects on instrumentation are pertaining primarily to long-run-duration wind tunnel facilities. In order to characterize such influences on instrumentation in the models, in short-run-duration blowdown wind tunnels, temperature measurements were made in the wing-panel-balance and main-balance spaces of two wind tunnel models tested in the T-38 wind tunnel. The measurements showed that model-interior temperature in a run increased at the beginning of the run, followed by a slower drop and, at the end of the run, by a large temperature drop. Panel-force balance was affected much more than the main balance. Ways of reducing the unwelcome thermal effects by instrumentation design and test planning are discussed.

  5. Effective Method for Determining Environmental Loads on Supporting Structures for Offshore Wind Turbines

    Directory of Open Access Journals (Sweden)

    Dymarski Paweł

    2016-01-01

    Full Text Available This paper presents a description of an effective method for determining loads due to waves and current acting on the supporting structures of the offshore wind turbines. This method is dedicated to the structures consisting of the cylindrical or conical elements as well as (truncates pyramids of polygon with a large number of sides (8 or more. The presented computational method is based on the Morison equation, which was originally developed only for cylindrically shaped structures. The new algorithm shown here uses the coefficients of inertia and drag forces that were calculated for non-cylindrical shapes. The analysed structure consists of segments which are truncated pyramids on the basis of a hex decagon. The inertia coefficients, CM, and drag coefficients, CD, were determined using RANSE-CFD calculations. The CFD simulations were performed for a specific range of variation of the period, and for a certain range of amplitudes of the velocity. In addition, the analysis of influence of the surface roughness on the inertia and drag coefficients was performed. In the next step, the computations of sea wave, current and wind load on supporting structure for the fifty-year storm were carried out. The simulations were performed in the time domain and as a result the function of forces distribution along the construction elements was obtained. The most unfavourable distribution of forces will be used, to analyse the strength of the structure, as the design load.

  6. Turbulence descriptors for scaling fatigue loading spectra of wind turbine structural components

    Energy Technology Data Exchange (ETDEWEB)

    Kelley, N D

    1994-07-01

    The challenge for the designer in developing a new wind turbine is to incorporate sufficient strength in its components to safely achieve a 20- or 30-year service life. To accomplish this, the designer must understand the load and stress distributions (in a statistical sense at least) that the turbine is likely to encounter during its operating life. Sources of loads found in the normal operating environment include start/stop cycles, emergency shutdowns, the turbulence environment associated with the specific site and turbine location, and extreme or ``rare`` events that can challenge the turbine short-term survivability. Extreme events can result from an operational problem (e.g., controller failure) or violent atmospheric phenomena (tornadic circulations, strong gust fronts). For the majority of the operating time, however, the character of the turbulent inflow is the dominant source of the alternating stress distributions experienced by the structural components. Methods of characterizing or scaling the severity of the loading spectra (or the rate of fatigue damage accumulation) must be applicable to a wide range of turbulent inflow environments -- from solitary isolation to the complex flows associated with multi-row wind farms. The metrics chosen must be related to the properties of the turbulent inflow and independent of the nature of local terrain features.

  7. Renewable Generation (Wind/Solar and Load Modeling through Modified Fuzzy Prediction Interval

    Directory of Open Access Journals (Sweden)

    Syed Furqan Rafique

    2018-01-01

    Full Text Available The accuracy of energy management system for renewable microgrid, either grid-connected or isolated, is heavily dependent on the forecasting precision such as wind, solar, and load. In this paper, an improved fuzzy prediction horizon forecasting method is developed to address the issue of intermittence and uncertainty problem related to renewable generation and load forecast. In the first phase, a Takagi-Sugeno type fuzzy system is trained with many evolutionary optimization algorithms and established coverage grade indicator to check the accuracy of interval forecast. Secondly, a wind, solar, and load forecaster is developed for renewable microgrid test bed which is located in Beijing, China. One day and one step ahead results for the proposed forecaster are expressed with lowest RMSE and training time. In order to check the efficiency of the proposed method, a comparison is carried out with the existing models. The fuzzy interval-based model for the microgrid test bed will help to formulate the energy management problem with more accuracy and robustness.

  8. Integrity of reinforced concrete cooling towers under extreme loads: Wind and earthquake

    International Nuclear Information System (INIS)

    Louhi, Amine

    2015-01-01

    The authorities have planned to increase the lifetime of currently operating nuclear power plants. The ageing of reinforced concrete structures such as cooling towers should be evaluated and its impact on the bearing capacity calculated. In the case of significant damage, the strengthening must be considered to ensure the sustainability of these towers facing the risk of storms and earthquakes becoming more and more frequent. This work aims to quantify the adverse effects that can generate concrete cracks and rebar section loss induced by corrosion, especially on the bearing capacity of nuclear power plant cooling towers under monotonic or cyclic extreme load conditions (wind and earthquake). These loads are certainly the most severe, since they take the structure into the nonlinear domain and can induce or amplify cracking damage. Numerical simulations are proposed to determine the quasi-static or dynamic response of the structure, taking into account appearance of concrete cracks and their evolution via an appropriate material concrete law and rebar's yielding. In the case of a seismic load, the responses are evaluated by three different methods; the nonlinear response history analysis (NLRHA), the response spectrum analysis and the modal response history analysis (MRHA) in order to compare the earthquake modeling approaches and to evaluate the robustness of the results. Parametric studies on damping, load combinations and structural configurations, are also performed. In the case of a wind load, the strengthening technique using composite materials, such as carbon fiber reinforced plastic (CFRP) is modeled. The behavior of the damaged structure with an advanced corrosion rate is estimated in the pre- and post-cracking regime, compared to the undamaged structure. The drop of bearing capacity is quantified, a reinforcement designed is proposed to restore the integrity and thus increase the lifetime of the structure. (author)

  9. Simplified rotor load models and fatigue damage estimates for offshore wind turbines.

    Science.gov (United States)

    Muskulus, M

    2015-02-28

    The aim of rotor load models is to characterize and generate the thrust loads acting on an offshore wind turbine. Ideally, the rotor simulation can be replaced by time series from a model with a few parameters and state variables only. Such models are used extensively in control system design and, as a potentially new application area, structural optimization of support structures. Different rotor load models are here evaluated for a jacket support structure in terms of fatigue lifetimes of relevant structural variables. All models were found to be lacking in accuracy, with differences of more than 20% in fatigue load estimates. The most accurate models were the use of an effective thrust coefficient determined from a regression analysis of dynamic thrust loads, and a novel stochastic model in state-space form. The stochastic model explicitly models the quasi-periodic components obtained from rotational sampling of turbulent fluctuations. Its state variables follow a mean-reverting Ornstein-Uhlenbeck process. Although promising, more work is needed on how to determine the parameters of the stochastic model and before accurate lifetime predictions can be obtained without comprehensive rotor simulations. © 2015 The Author(s) Published by the Royal Society. All rights reserved.

  10. Reduction mechanism of dynamic loads on down wind rotor; Furyoku hatsuden system down wind rotor no doteki kaju no keigen kiko ni kansuru kenkyu

    Energy Technology Data Exchange (ETDEWEB)

    Seki, K.; Shimizu, Y.; Yasui, T. [Tokai University, Tokyo (Japan)

    1997-11-25

    Dynamic force on blades in a large wind mill changes with rotational speed for various reasons, such as wind shear that causes vertical distribution of wind velocity or titling angle. Therefore, a 2-blade system on a teetered hub is a practical selection for the coned, down-wind type. Use of teetered axis greatly reduces bending moment in the flap direction and that at the axis of rotation. An attempt was made to understand dynamic loads by inertial force resulting from oscillation of the blade rotating on the teetered axis, and thereby to avoid them. The in-plane load can be diminished to zero when the teetered axis is coincided with the center of gravity, but generally cannot be avoided when the blade is strained significantly, except it is operated at the rated condition. The in-plane load and bending moment can be avoided, when rotational freedom is given around the y axis. Dynamic load on a down-wind rotor can be avoided by use of universal joint. 3 refs., 6 figs.

  11. Open access wind tunnel measurements of a downwind free yawing wind turbine

    DEFF Research Database (Denmark)

    Verelst, David Robert; Larsen, Torben J.; van Wingerden, Jan-Willem

    2016-01-01

    A series of free yawing wind tunnel experiments was held in the Open Jet Facility (OJF) of the TU Delft. The ≈ 300 W turbine has three blades in a downwind configuration and is optionally free to yaw. Different 1.6m diameter rotor configurations are tested such as blade flexibility and sweep....... This paper gives a brief overview of the measurement setup and challenges, and continues with presenting some key results. This wind tunnel campaign has shown that a three bladed downwind wind turbine can operate in a stable fashion under a minimal yaw error. Finally, a description of how to obtain this open...... access dataset, including the post-processing scripts and procedures, is made available via a publicly accessible website....

  12. Design Loads on Platforms on Offshore wind Turbine Foundations with Respect to Vertical Wave Run-up

    DEFF Research Database (Denmark)

    Damsgaard, Mathilde L.; Gravesen, Helge; Andersen, Thomas Lykke

    2007-01-01

    Experiences have shown that the vertical run-up generated by waves meeting the offshore wind turbine foundations, can result in rather vigorous loads on appurtenances and platform structures. This study aims to provide a qualitative method of determining run-up height and the following loads...

  13. Modelling the drained response of bucket foundations for offshore wind turbines under general monotonic and cyclic loading

    DEFF Research Database (Denmark)

    Foglia, Aligi; Gottardi, Guido; Govoni, Laura

    2015-01-01

    the typical conditions of offshore wind turbines: very large cyclic overturning moment, large cyclic horizontal load and comparatively little, self-weight induced, vertical load. The experimental soil-foundation response is interpreted within the macro-element approach, using an existing analytical model...

  14. Optimal control of a fuel cell/wind/PV/grid hybrid system with thermal heat pump load

    CSIR Research Space (South Africa)

    Sichilalu, S

    2016-10-01

    Full Text Available This paper presents an optimal energy management strategy for a grid-tied photovoltaic–wind-fuel cell hybrid power supply system. The hybrid system meets the load demand consisting of an electrical load and a heat pump water heater supplying thermal...

  15. Detailed signal model of coherent wind measurement lidar

    Science.gov (United States)

    Ma, Yuechao; Li, Sining; Lu, Wei

    2016-11-01

    Lidar is short for light detection and ranging, which is a tool to help measuring some useful information of atmosphere. In the recent years, more and more attention was paid to the research of wind measurement by lidar. Because the accurate wind information can be used not only in weather report, but also the safety guarantee of the airplanes. In this paper, a more detailed signal model of wind measurement lidar is proposed. It includes the laser transmitting part which describes the broadening of the spectral, the laser attenuation in the atmosphere, the backscattering signal and the detected signal. A Voigt profile is used to describe the broadening of the transmitting laser spectral, which is the most common situation that is the convolution of different broadening line shapes. The laser attenuation includes scattering and absorption. We use a Rayleigh scattering model and partially-Correlated quadratic-Velocity-Dependent Hard-Collision (pCqSDHC) model to describe the molecule scattering and absorption. When calculate the particles scattering and absorption, the Gaussian particles model is used to describe the shape of particles. Because of the Doppler Effect occurred between the laser and atmosphere, the wind velocity can be calculated by the backscattering signal. Then, a two parameter Weibull distribution is used to describe the wind filed, so that we can use it to do the future work. After all the description, the signal model of coherent wind measurement lidar is decided. And some of the simulation is given by MATLAB. This signal model can describe the system more accurate and more detailed, so that the following work will be easier and more efficient.

  16. Analysis of Mexico wind tunnel measurements

    DEFF Research Database (Denmark)

    Schepers, J.G.; Boorsma, K.; Cho, T.

    This report describes the work performed within the first phase of IEA Task 29 Mexnext. In this IEA Task 29 a total of 20 organisations from 11 different countries collaborated in analysing the measurements which have been taken in the EU project ‘Mexico’. Within this Mexico project 9 European...

  17. Wind Profiling from a New Compact, Pulsed, 2-Micron, Coherent-Detection Doppler Lidar Transceiver during Wind Measurement Intercomparison

    Science.gov (United States)

    Singh, Upendra N.; Koch, Grady J.; Kavaya, Michael J.; Yu, Jirong; Beyon, Jeffrey Y.; Demoz, B.; Veneable, D.

    2009-01-01

    NASA Langley Research Center has a long history of developing 2-micron laser transmitter for wind sensing. With support from NASA Laser Risk Reduction Program (LRRP) and Instrument Incubator Program (IIP), NASA Langley Research Center has developed a state-of-the-art compact lidar transceiver for a pulsed coherent Doppler lidar system for wind measurement. This lidar system was recently deployed at Howard University facility in Beltsville, Maryland, along with other wind lidar systems. Coherent Doppler wind lidar ground-based wind measurements and comparisons with other lidars and other sensors will be presented.

  18. Robust Multimodal Cognitive Load Measurement (RMCLM)

    Science.gov (United States)

    2013-03-26

    3.2. Sub-Band Filtering The DWT provides a time-scale representation of a given signal, generated by dilation and translation of a mother Wavelet...natural interest by extensive audiovisual integration for real-life application, Image and Vision Computing 27 (12) (2009) 1760–1774. [42] C.M. Schulz, E... translating , and reviewing [Vanderberg and Swanson, 2007]. The cognitive load induced by these processes places a demand on working memory re- sources from

  19. High resolution wind turbine wake measurements with a scanning lidar

    DEFF Research Database (Denmark)

    Herges, T. G.; Maniaci, D. C.; Naughton, B. T.

    2017-01-01

    High-resolution lidar wake measurements are part of an ongoing field campaign being conducted at the Scaled Wind Farm Technology facility by Sandia National Laboratories and the National Renewable Energy Laboratory using a customized scanning lidar from the Technical University of Denmark. One...

  20. Measurement based analysis of active and reactive power losses in a distribution network with wind farms and CHPs

    DEFF Research Database (Denmark)

    Lund, Torsten

    2007-01-01

    The paper presents an investigation of the active and reactive power losses in a distribution network with wind turbines and combined heat and power plants. The investigation is based on 15 min average power measurements and load flow calculations in the power system simulation tool PowerFactory...

  1. Full scale testing of wind turbine blade to failure - flapwise loading

    DEFF Research Database (Denmark)

    Jørgensen, E.R.; Borum, Kaj Kvisgaard; McGugan, Malcolm

    2004-01-01

    for the detection of damages in the blade during the test. The report contains measurements of the total deflection of the blade, the local deflection of the skinand the load carrying main spar and also measurement of strain all as a function of the applied load and up to failure of the blade. The “post mortem......” analysis and description of how the damages propagate du-ring the tests are reported in a separatereport....

  2. Adaptive optics in coherent lidar wind measurements: A feasibility study

    Science.gov (United States)

    Leland, Robert P.

    1991-01-01

    Laser Doppler radar (lidar) is widely used for remote sensing of wind velocities. Usable wavelengths for the laser are limited by the effects of atmospheric turbulence. An adaptive optical system is proposed to compensate for turbulence effects on signal power. The feasibility of an adaptive system is considered in light of the effects of speckle from the aerosol target. It is concluded that adaptive optics is a promising technique for improving the performance of a 2 micron lidar wind measurement system. The chief technical challenges are a laser that will give the required output and pulse repetition rate, a combined Hartmann sensor and heterodyne detector, and a suitable reconstruction algorithm.

  3. Vibration analysis of 1 MW gearbox for the Avedoere wind turbine. Test bed measurements

    International Nuclear Information System (INIS)

    Crone, A.

    1995-03-01

    The investigations had several purposes: Firstly, to determine and evaluate the structure-borne noise source strength of the gearbox, which is relevant for the final gear noise emission from the wind turbine. Secondly, to select the potentially least noisy gear set out of two, which have been made for the output gear stage. And Thirdly, to obtain the natural vibration modes of the gearbox structure, in order to determine if the structure-borne noise, transmitted to the wind turbine structure, will be amplified due to resonance conditions. Additional vibration tests were carried out. Among these, trials of 'in situ' measurement of the Transmission Error of the output gear stage, and measurements of the torsional vibrations of the input and output shaft. The test of the two output gear sets (from Flender AG and ELKRAFT A.m.b.A.) had the aim to determine the least noisy one of two different tooth profiles. Both gear sets were intended for the Avedoere Wind Turbine when it, in its first period of operation, is going to operate as a stall regulated turbine. After the first mesurements and the exchange of the Flender-designed gear set with the ELKRAFT-designed gear set, troubles with the backmost bearing of the intermediate shaft arose. The evaluation of the structure-borne noise source strength (expressed as the vibration velocity level), has in general been made at load conditions which correspond to the conditions in the wind turibne at a wind speed of 8 m/s, 10 m above terrain (v 10 ). This condition, is the one normally used when the noise emission from wind turbines is evaluated. At the comparison of the two gear sets against each other, the influence of the torque load on the source strength has also been considered. This comparison may indicate the load at which the profile correction is most effective, and may determine the noise potential of the gearbox at wind speeds lower than 8 m/s, which could also be of interest

  4. Development of a Wind Plant Large-Eddy Simulation with Measurement-Driven Atmospheric Inflow: Preprint

    Energy Technology Data Exchange (ETDEWEB)

    Quon, Eliot; Churchfield, Matthew; Cheung, Lawrence; Kern, Stefan

    2017-02-01

    This paper details the development of an aeroelastic wind plant model with large-eddy simulation (LES). The chosen LES solver is the Simulator for Wind Farm Applications (SOWFA) based on the OpenFOAM framework, coupled to NREL's comprehensive aeroelastic analysis tool, FAST. An atmospheric boundary layer (ABL) precursor simulation was constructed based on assessments of meteorological tower, lidar, and radar data over a 3-hour window. This precursor was tuned to the specific atmospheric conditions that occurred both prior to and during the measurement campaign, enabling capture of a night-to-day transition in the turbulent ABL. In the absence of height-varying temperature measurements, spatially averaged radar data were sufficient to characterize the atmospheric stability of the wind plant in terms of the shear profile, and near-ground temperature sensors provided a reasonable estimate of the ground heating rate describing the morning transition. A full aeroelastic simulation was then performed for a subset of turbines within the wind plant, driven by the precursor. Analysis of two turbines within the array, one directly waked by the other, demonstrated good agreement with measured time-averaged loads.

  5. Wind Turbine Wake Characterization from Temporally Disjunct 3-D Measurements

    Directory of Open Access Journals (Sweden)

    Paula Doubrawa

    2016-11-01

    Full Text Available Scanning LiDARs can be used to obtain three-dimensional wind measurements in and beyond the atmospheric surface layer. In this work, metrics characterizing wind turbine wakes are derived from LiDAR observations and from large-eddy simulation (LES data, which are used to recreate the LiDAR scanning geometry. The metrics are calculated for two-dimensional planes in the vertical and cross-stream directions at discrete distances downstream of a turbine under single-wake conditions. The simulation data are used to estimate the uncertainty when mean wake characteristics are quantified from scanning LiDAR measurements, which are temporally disjunct due to the time that the instrument takes to probe a large volume of air. Based on LES output, we determine that wind speeds sampled with the synthetic LiDAR are within 10% of the actual mean values and that the disjunct nature of the scan does not compromise the spatial variation of wind speeds within the planes. We propose scanning geometry density and coverage indices, which quantify the spatial distribution of the sampled points in the area of interest and are valuable to design LiDAR measurement campaigns for wake characterization. We find that scanning geometry coverage is important for estimates of the wake center, orientation and length scales, while density is more important when seeking to characterize the velocity deficit distribution.

  6. Measurements of Martian dust devil winds with HiRISE

    Science.gov (United States)

    Choi, D.S.; Dundas, C.M.

    2011-01-01

    We report wind measurements within Martian dust devils observed in plan view from the High Resolution Imaging Science Experiment (HiRISE) orbiting Mars. The central color swath of the HiRISE instrument has three separate charge-coupled devices (CCDs) and color filters that observe the surface in rapid cadence. Active features, such as dust devils, appear in motion when observed by this region of the instrument. Our image animations reveal clear circulatory motion within dust devils that is separate from their translational motion across the Martian surface. Both manual and automated tracking of dust devil clouds reveal tangential winds that approach 20-30 m s -1 in some cases. These winds are sufficient to induce a ???1% decrease in atmospheric pressure within the dust devil core relative to ambient, facilitating dust lifting by reducing the threshold wind speed for particle elevation. Finally, radial velocity profiles constructed from our automated measurements test the Rankine vortex model for dust devil structure. Our profiles successfully reveal the solid body rotation component in the interior, but fail to conclusively illuminate the profile in the outer regions of the vortex. One profile provides evidence for a velocity decrease as a function of r -1/2, instead of r -1, suggestive of surface friction effects. However, other profiles do not support this observation, or do not contain enough measurements to produce meaningful insights. Copyright 2011 by the American Geophysical Union.

  7. Time-Accurate Unsteady Pressure Loads Simulated for the Space Launch System at Wind Tunnel Conditions

    Science.gov (United States)

    Alter, Stephen J.; Brauckmann, Gregory J.; Kleb, William L.; Glass, Christopher E.; Streett, Craig L.; Schuster, David M.

    2015-01-01

    A transonic flow field about a Space Launch System (SLS) configuration was simulated with the Fully Unstructured Three-Dimensional (FUN3D) computational fluid dynamics (CFD) code at wind tunnel conditions. Unsteady, time-accurate computations were performed using second-order Delayed Detached Eddy Simulation (DDES) for up to 1.5 physical seconds. The surface pressure time history was collected at 619 locations, 169 of which matched locations on a 2.5 percent wind tunnel model that was tested in the 11 ft. x 11 ft. test section of the NASA Ames Research Center's Unitary Plan Wind Tunnel. Comparisons between computation and experiment showed that the peak surface pressure RMS level occurs behind the forward attach hardware, and good agreement for frequency and power was obtained in this region. Computational domain, grid resolution, and time step sensitivity studies were performed. These included an investigation of pseudo-time sub-iteration convergence. Using these sensitivity studies and experimental data comparisons, a set of best practices to date have been established for FUN3D simulations for SLS launch vehicle analysis. To the author's knowledge, this is the first time DDES has been used in a systematic approach and establish simulation time needed, to analyze unsteady pressure loads on a space launch vehicle such as the NASA SLS.

  8. Research of Short-range Missile Motion in Terms of Different Wind Loads

    Directory of Open Access Journals (Sweden)

    A. N. Klishin

    2015-01-01

    Full Text Available When modeling the aircraft motion it is advisable to choose a particular model of the Earth, depending both on the task and on the required accuracy of calculation. The article describes various models of the Earth, such as the flat Earth with a plane-parallel field of gravity, spherical and non-rotating Earth with a plane-parallel field of gravity, spherical and non-rotating Earth with a central gravitational field, spherical and non-rotating Earth, taking into account the polar flattening of the Earth, spherical Earth based compression and polar daily rotation. The article also considers the influence of these models on the motion of the selected aircraft.To date, there is technical equipment to provide highly accurate description of the Earthshape, gravitational field, etc. The improved accuracy of the Earth model description results in more correct description of the trajectory and motion parameters of a ballistic missile. However, for short ranges (10-20 km this accuracy is not essential, and, furthermore, it increases time of calculation. Therefore, there is a problem of choosing the optimal description of the Earth parameters.The motion in the model of the Earth, which takes into account a daily rotation of the planet and polar flattening, is discussed in more detail, and the geographical latitude impact on coordinates of the points of fall of a ballistic missile is analyzed on the basis of obtained graphs.The article individually considers a problem of the wind effect on the aircraft motion and defines dependences of the missile motion on the parameters of different wind loads, such as wind speed and height of its action.A mathematical model of the missile motion was built and numerically integrated, using the Runge-Kutta 4th order method, for implementation and subsequent analysis.Based on the analysis of the calculation results in the abovementioned models of the Earth, differences in impact of these models on the parameters of the

  9. Accounting for the speed shear in wind turbine power performance measurement

    DEFF Research Database (Denmark)

    Wagner, Rozenn; Courtney, Michael; Gottschall, Julia

    2011-01-01

    The current IEC standard for wind turbine power performance measurement only requires measurement of the wind speed at hub height assuming this wind speed to be representative for the whole rotor swept area. However, the power output of a wind turbine depends on the kinetic energy flux, which...

  10. Measurement campaign for wind power potential in west Greenland

    Science.gov (United States)

    Rønnow Jakobsen, Kasper

    2013-04-01

    . During the first years, the influence of instrument icing was not considered, but recently one of the sites was equipped with an ice rate sensor and a heated ultrasonic anemometer to study the ice influence. 3 Results The predominant wind direction for most sites is away from the ice cap at the center of the continent, but for some coastal sites it is north or south. The north-south wind pattern is expected from the synoptic patterns and the barrier effect of the ice cap. The sites where the predominant wind direction is away from the inland ice are dominated by katabatic wind systems from the ice cap and form valley systems. These sites also seem to have the highest wind resource and will be studied further. A good example of the influence of katabatic and thermal wind systems can be seen in the measurement data from Sarfannguit and Nanortalik 66 and 60 degrees northern latitude respectively. In future work, these katabatic flows and their impact on the wind resource will be studied using mesoscale modelling and microscale downscaling.

  11. The Skipheia Wind Measurement Station. Instrumentation, Wind Speed Profiles and Turbulence Spectra

    Energy Technology Data Exchange (ETDEWEB)

    Aasen, S.E.

    1995-10-01

    This thesis describes the design of a measurement station for turbulent wind and presents results from an analysis of the collected data. The station is located at Skipheia near the south-west end of Froeya, an island off the coast of Mid-Norway. The station is unique for studies of turbulent winds because of the large numbers of sensors, which are located at various heights above ground up to 100 m, a sampling rate of 0.85 Hz and storage of the complete time series. The frequency of lightning and atmospheric discharges to the masts are quite high and much effort has gone into minimizing the damage caused by lightning activity. A major part of the thesis deals with data analysis and modelling. There are detailed discussions on the various types of wind sensors and their calibration, the data acquisition system and operating experiences with it, the database, data quality control, the wind speed profile and turbulence. 40 refs., 78 figs., 17 tabs.

  12. Cognitive load measurement as a means to advance cognitive load theory

    NARCIS (Netherlands)

    Paas, F.; Tuovinen, J.E.; Tabbers, H.; van Gerven, P.W.M.

    2003-01-01

    This paper discusses cognitive load measurement techniques with regard to their contribution to cognitive load theory (CLT). CLT is concerned with the design of instructional methods that efficiently use people's limited cognitive processing capacity to apply acquired knowledge and skills to new

  13. Spatio-Temporal Measurements of Short Wind Water Waves

    Science.gov (United States)

    Rocholz, Roland; Jähne, Bernd

    2010-05-01

    Spatio-temporal measurements of wind-driven short-gravity capillary waves are reported for a wide range of experimental conditions, including wind, rain and surface slicks. The experiments were conducted in the Hamburg linear wind/wave flume in cooperation with the Institute of Oceanography at the University of Hamburg, Germany. Both components of the slope field were measured optically at a fetch of 14.4 m using a color imaging slope gauge (CISG) with a footprint of 223 x 104 mm and a resolution of 0.7 mm. The instrument was improved versus earlier versions (Jähne and Riemer (1990), Klinke (1992)) to achieve a sampling rate of 312.5 Hz, which now allows for the computation of 3D wavenumber-frequency spectra (see Rocholz (2008)). This made it possible to distinguish waves traveling in and against wind direction, which proved useful to distinguish wind waves from ring waves caused by rain drop impacts. Using a new calibration method it was possible to correct for the intrinsic nonlinearities of the instrument in the slope range up to ±1. In addition, the Modulation Transfer Function (MTF) was measured and employed for the restoration of the spectral amplitudes for wavenumbers in the range from 60 to 2300 rad/m. The spectra for pure wind conditions are generally consistent with previous measurements. But, the shape of the saturation spectra in the vicinity of k~1000 rad/m (i.e. pure capillary waves) stands in contradiction to former investigations where a sharp spectral cutoff (k^(-2) or k^(-3)) is commonly reported (e.g. Jähne and Riemer (1990)). This cutoff is reproduced by almost all semi-empirical models of the energy flux in the capillary range (e.g. Kudryavtsev et al. (1999), Apel (1994)). However, the new MTF corrected spectra show only a gentle decrease (between k^(-0.5) and k^(-1)) for k > 1000 rad/m. Therefore the question for the relative importance of different dissipation mechanisms might need a new assessment. References: J. R. Apel. An improved

  14. Analytical aeroelastic stability considerations and conversion loads for an XV-15 tilt-rotor in a wind tunnel simulation

    Science.gov (United States)

    Kottapalli, Sesi; Meza, Victor

    1992-01-01

    A rotorcraft analysis is conducted to assess tilt-rotor stability and conversion loads for the XV-15 rotor with metal blades within its specified test envelope. A 38-DOF flutter analysis based on the code by Johnson (1988) is developed to simulate a wind-tunnel test in which the rotor torque is constant and thereby study stability. The same analytical model provides the simulated loads including hub loads, blade loads, and oscillatory pitch-link loads with attention given to the nonuniform inflow through the proprotor in the presence of the wing. Tilt-rotor stability during the cruise mode is found to be sensitive to coupling effects in the control system stiffness, and a stability problem is identified in the XV-15 Advanced Technology Blades. The present analysis demonstrates that the tilt-rotor is stable within the specified test envelope of the NASA 40 x 80-ft wind tunnel.

  15. Wind-Tunnel Investigation of Wind Loads on a Post-Panamax Container Ship as a Function of the Container Configuration on Deck

    DEFF Research Database (Denmark)

    Andersen, Ingrid Marie Vincent

    2012-01-01

    An investigation of the wind forces acting on a 9,000+ TEU container ship has been carried out through a series of wind tunnel tests. It was investigated how the wind forces depend on the container configuration on the deck using a 1:450 scale model and a series of appropriate container...... are presented as nondimensional coefficients. It is concluded, that the measured forces and moment depend on the container configuration on deck, and the results may provide a general idea of how the magnitude of the wind forces is affected by a given container stacking configuration on a similar container ship....

  16. Wind Load Design of Hangar-Type Closed Steel Structures with Different Roof Pitches Using Abaqus CAE Software

    Directory of Open Access Journals (Sweden)

    Aybike Özyüksel Çiftçioğlu

    2017-05-01

    Full Text Available Structures convert the kinetic energy available in the air into potential energy which is in the form of pressure and suction forces reducing or fully stopping its motion. The potential impact of the wind depends on the geometric properties and pertinacity of a building, the angle of the wind flow, its strength and velocity. Design gains importance for tall buildings against the impact of the resonance along with the force based on pressure. Relevant calculations are made in Turkey based on the TS 498 Wind Load Velocity Criterion and this standard is currently being updated. This study develops the wind load design of hangar-type closed steel structures with different roof pitches using Abaqus CAE software.

  17. Wind-Tunnel Evaluation of the Effect of Blade Nonstructural Mass Distribution on Helicopter Fixed-System Loads

    Science.gov (United States)

    Wilbur, Matthew L.; Yeager, Jr, William T.; Singleton, Jeffrey D.; Mirick, Paul H.; Wilkie, W K.

    1998-01-01

    This report provides data obtained during a wind-tunnel test conducted to investigate parametrically the effect of blade nonstructural mass on helicopter fixed-system vibratory loads. The data were obtained with aeroelastically scaled model rotor blades that allowed for the addition of concentrated nonstructural masses at multiple locations along the blade radius. Testing was conducted for advance ratios ranging from 0.10 to 0.35 for 10 blade-mass configurations. Three thrust levels were obtained at representative full-scale shaft angles for each blade-mass configuration. This report provides the fixed-system forces and moments measured during testing. The comprehensive database obtained is well-suited for use in correlation and development of advanced rotorcraft analyses.

  18. Hover test of a full-scale hingeless helicopter rotor: Aeroelastic stability, performance and loads data. [wind tunnel tests

    Science.gov (United States)

    Peterson, R. L.; Warmbrodt, W.

    1984-01-01

    A hover test of a full-scale, hingeless rotor system was conducted in the NASA Ames 40- by 80-foot wind tunnel. The rotor was tested on the Ames rotor test apparatus. Rotor aeroelastic stability, performance, and loads at various rotational speeds and thrust coefficients were investigated. The primary objective was to determine the inplane stability characteristics of the rotor system. Rotor inplane damping data were obtained for operation between 350 and 425 rpm (design speed), and for thurst coefficients between 0.0 and 0.12. The rotor was stable for all conditions tested. At constant rotor rotational speed, a minimum inplane dampling level was obtained at a thrust coefficient approximately = 0.02. At constant rotor lift, a minimum in rotor inplane damping was measured at 400 rpm.

  19. Computer-aided optimization of an offshore jacket for a wind turbine with a simplified load model

    OpenAIRE

    Bakkom, Ole Edvard

    2015-01-01

    In this report the jacket structure of a 5MW reference offshore wind turbine has been explored in terms of structural redundancy and for optimisation of the node locations. This has been done by the creation and utilisation of fully parametric scripts that creates input and post processes results from Abaqus CAE. The dynamic nature of offshore wind turbine forms a basis for complex loading of the jacket structure. This makes the analysis work needed to fully understand such structures substan...

  20. Operating and Loading Conditions of a Three-Level Neutral-Point-Clamped Wind Power Converter Under Various Grid Faults

    DEFF Research Database (Denmark)

    Ma, Ke; Liserre, Marco; Blaabjerg, Frede

    2014-01-01

    In order to fulfill the growing demands from the grid side, full-scale power converters are becoming popular in the wind turbine system. The low-voltage ride-through (LVRT) requirements may not only cause control problems but also result in overstressed components for the power converter. However...... are analytically solved and simulated. It has been found that the operating and loading conditions of the converter under LVRT strongly depend on the types/severity values of grid voltage dips and also the chosen control algorithms. The thermal distribution among the three phases of the converter may be quite......, the thermal loading of the wind power converter under various grid faults is still not yet clarified, particularly at megawatt power level. In this paper, the impacts by three types of grid faults to a three-level neutral-point-clamped (3L-NPC) wind power converter in terms of operating and loading conditions...

  1. Sliding mode load frequency control for multi-area time-delay power system with wind power integration

    DEFF Research Database (Denmark)

    Mi, Yang; Hao, Xuezhi; Liu, Yongjuan

    2017-01-01

    The interconnected time-delay power system has become an important issue for the open communication network. Meanwhile, due to the output power fluctuation of integrated wind energy, load frequency control (LFC) for power system with variable sources and loads has become more complicated. The novel...... the hitting condition. At last, the SM controller is proved by using the real-time digital simulator device under different case of time delay, wind penetration, load disturbance and operating point. The test results show that the proposed SM LFC can reduce frequency deviation and tie-line power fluctuation...... decentralised sliding mode (SM) LFC strategy is proposed for multi-area time-delay power system with significant wind power penetration. The appropriate switching surface gain is selected to assure the stability of power system with mismatched uncertainties. The SM controller is constructed to satisfy...

  2. Transient pressure measurements at part load operating condition of ...

    Indian Academy of Sciences (India)

    Rahul Goyal

    hydraulic energy or demand of market. The turbine expe- riences unstable flow conditions during .... gate the pressure loading inside the turbine at a similar load. No measurements have been reported in the .... speed factor (nED) and discharge factor (qED) are 0.18 and. 0.15, respectively. The operating point selected for ...

  3. Analysis of Mexico wind tunnel measurements. Final report of IEA Task 29, Mexnext (Phase 1)

    Energy Technology Data Exchange (ETDEWEB)

    Schepers, J.G.; Boorsma, K. [Energy research Center of the Netherlands ECN, Petten (Netherlands); Cho, T. [Korea Aerospace Research Institute KARI, Daejeon (Korea, Republic of); Gomez-Iradi, S. [National Renewable Energy Center of Spain CENER, Sarriguren (Spain); Schaffarczyk, P. [A. Jeromin University of Applied Sciences, CEWind EG, Kiel (Germany); Shen, W.Z. [The Technical University of Denmark, Kongens Lyngby (Denmark); Lutz, T. [K. Meister University of Stuttgart, Stuttgart (Germany); Stoevesandt, B. [ForWind, Zentrum fuer Windenergieforschung, Oldenburg (Germany); Schreck, S. [National Renewable Energy Laboratory NREL, Golden, CO (United States); Micallef, D.; Pereira, R.; Sant, T. [Delft University of Technology TUD, Delft (Netherlands); Madsen, H.A.; Soerensen, N. [Risoe-DTU, Roskilde (Denmark)

    2012-02-15

    This report describes the work performed within the first phase of IEA Task 29 Mexnext. In this IEA Task 29 a total of 20 organisations from 11 different countries collaborated in analysing the measurements which have been performed in the EU project 'Mexico'. Within this Mexico project 9 European institutes carried out a wind tunnel experiment in the Large Low Speed Facility (LLF) of the German Dutch Wind Facilities DNW on a rotor with a diameter of 4.5 m. Pressure distributions were measured at five locations along the blade along with detailed flow field measurements around the rotor plane using stereo PIV. As a result of the international collaboration within this task a very thorough analysis of the data could be carried out and a large number of codes were validated not only in terms of loads but also in terms of underlying flow field. The detailed pressure measurements along the blade in combination with the detailed flow field measurements gave a unique opportunity to better understand the response of a wind turbine to the incoming flow field. Deficiencies in modelling have been established and directions for model improvement can be given.

  4. Fastener load tests and retention systems tests for cryogenic wind-tunnel models

    Science.gov (United States)

    Wallace, J. W.

    1984-01-01

    A-286 stainless steel screws were tested to determine the tensile load capability and failure mode of various screw sizes and types at both cryogenic and room temperature. Additionally, five fastener retention systems were tested by using A-286 screws with specimens made from the primary metallic alloys that are currently used for cryogenic models. The locking system effectiveness was examined by simple no-load cycling to cryogenic temperatures (-275 F) as well as by dynamic and static loading at cryogenic temperatures. In general, most systems were found to be effective retention devices. There are some differences between the various devices with respect to ease of application, cleanup, and reuse. Results of tests at -275 F imply that the cold temperatures act to improve screw retention. The improved retention is probably the result of differential thermal contraction and/or increased friction (thread-binding effects). The data provided are useful in selecting screw sizes, types, and locking devices for model systems to be tested in cryogenic wind tunnels.

  5. An analysis of offshore wind farm SCADA measurements to identify key parameters influencing the magnitude of wake effects

    Science.gov (United States)

    Mittelmeier, N.; Blodau, T.; Steinfeld, G.; Rott, A.; Kühn, M.

    2016-09-01

    Atmospheric conditions have a clear influence on wake effects. Stability classification is usually based on wind speed, turbulence intensity, shear and temperature gradients measured partly at met masts, buoys or LiDARs. The objective of this paper is to find a classification for stability based on wind turbine Supervisory Control and Data Acquisition (SCADA) measurements in order to fit engineering wake models better to the current ambient conditions. Two offshore wind farms with met masts have been used to establish a correlation between met mast stability classification and new aggregated statistical signals based on multiple measurement devices. The significance of these new signals on power production is demonstrated for two wind farms with met masts and validated against data from one further wind farm without a met mast. We found a good correlation between the standard deviation of active power divided by the average power of wind turbines in free flow with the ambient turbulence intensity when the wind turbines were operating in partial load.

  6. Turbulent wind field characterization and re-generation based on pitot tube measurements mounted on a wind turbine

    DEFF Research Database (Denmark)

    Pedersen, Mads Mølgaard; Larsen, Torben J.; Aagaard Madsen, Helge

    2015-01-01

    This paper describes a new method to estimate the undisturbed inflow field of a wind turbine based on measurements obtained from one or more five-hole pitot tubes mounted directly on the blades. Based on the measurements, the disturbance caused by the wind turbine is estimated using aerodymanic m...

  7. [Suspension-sedimentation of sediment and release amount of internal load in Lake Taihu affected by wind].

    Science.gov (United States)

    Pang, Yong; Yan, Run-run; Yu, Zhong-bo; Li, Yi-ping; Li, Rui-ling

    2008-09-01

    The water quality in Meiliang Bay of the Taihu Lake was totally tested five times in the four seasons. The suspension samples were obtained by using a sediment trap. The sediment settling flux and resuspended flux were calculated according to the observation data by using Gansith formula, and the relationships between these fluxes and wind speeds were established. Seven experiments were conducted in Laboratory for hydrostatic settling behavior of suspended matter affected by different wind speeds in Lake Taihu. The hydrostatic settling fluxes of suspended matter were calculated and the relationships between the fluxes and suspended matter concentrations were established. Base on these works, the suspension-sedimentation process was decomposed and generalized according to the critical wind speed of 3.7 m/s. Daily sediment resuspended amount and settling amount of the year 2005 was calculated and annual average release amount of internal load in Lake Taihu was estimated using the wind data of nearly 10 years. The results indicate that daily release amount of internal load in Lake Taihu significantly influenced by wind and have the same trend of change with wind, while the release amount of different nutrients in the same condition are different. The Lake Taihu has an annual average release amount of internal load with COD 49,600 t, TN 7773.0 t and TP 275.5 t, of which summer has the markedly highest release amount than other seasons.

  8. High resolution wind turbine wake measurements with a scanning lidar

    Science.gov (United States)

    Herges, T. G.; Maniaci, D. C.; Naughton, B. T.; Mikkelsen, T.; Sjöholm, M.

    2017-05-01

    High-resolution lidar wake measurements are part of an ongoing field campaign being conducted at the Scaled Wind Farm Technology facility by Sandia National Laboratories and the National Renewable Energy Laboratory using a customized scanning lidar from the Technical University of Denmark. One of the primary objectives is to collect experimental data to improve the predictive capability of wind plant computational models to represent the response of the turbine wake to varying inflow conditions and turbine operating states. The present work summarizes the experimental setup and illustrates several wake measurement example cases. The cases focus on demonstrating the impact of the atmospheric conditions on the wake shape and position, and exhibit a sample of the data that has been made public through the Department of Energy Atmosphere to Electrons Data Archive and Portal.

  9. Wind Turbine Performance Measurements by Means of Dynamic Data Analysis

    DEFF Research Database (Denmark)

    Friis Pedersen, Troels; Wagner, Rozenn; Demurtas, Giorgio

    curves could be made faster with 1Hz dataset. In the FastWind project the Langevin power curve method was used on real power curve measurement datasets with the purpose to evaluate the method for practical use. A practical guide to application of the method to real power curve measurement data was made....... The study showed that the method has a range of parameter settings that the user must consider. Additionally to the wind speed binning power binning is needed but power binning size is not specified. Determination of drift in each bin is described with a general formula but in practice several additional...... tools have been developed by authors to try to make the drift field and fixed point determination more robust. A sensitivity analysis with nacelle lidar data showed drift determination was not very dependent on the time steps applied, leading to use of time steps of 2-3 points for each dataset. Power...

  10. Comparing different CFD wind turbine modelling approaches with wind tunnel measurements

    Science.gov (United States)

    Kalvig, Siri; Manger, Eirik; Hjertager, Bjørn

    2014-12-01

    The performance of a model wind turbine is simulated with three different CFD methods: actuator disk, actuator line and a fully resolved rotor. The simulations are compared with each other and with measurements from a wind tunnel experiment. The actuator disk is the least accurate and most cost-efficient, and the fully resolved rotor is the most accurate and least cost-efficient. The actuator line method is believed to lie in between the two ends of the scale. The fully resolved rotor produces superior wake velocity results compared to the actuator models. On average it also produces better results for the force predictions, although the actuator line method had a slightly better match for the design tip speed. The open source CFD tool box, OpenFOAM, was used for the actuator disk and actuator line calculations, whereas the market leading commercial CFD code, ANSYS/FLUENT, was used for the fully resolved rotor approach.

  11. Using wind speed from a blade-mounted flow sensor for power and load assessment on modern wind turbines

    DEFF Research Database (Denmark)

    Pedersen, Mads M.; Larsen, Torben J.; Madsen, Helge Aa

    2017-01-01

    with the actual power production as well as the flap-wise loads as it is measured close to the blade where the aerodynamic forces are acting. Conventional power curves are based on at least 180 h of 10 min mean values, but using the blade-mounted flow sensor both the observation average time and the overall...... assessment time can potentially be shortened. The basis for this hypothesis is that the sensor is able to provide more observations with higher accuracy, as the sensor follows the rotation of the rotor and because of the high correlation between the flow at the blades and the power production...

  12. Velocity Measurement Systems for a Low-speed Wind Tunnel

    Science.gov (United States)

    2015-04-29

    SECURITY CLASSIFICATION OF: Funds were provided by the ARO for the purchase of TSI hot-wire anemometer equipment and a Dantec particle- image...Velocity Measurement Systems for a Low-speed Wind Tunnel Report Title Funds were provided by the ARO for the purchase of TSI hot-wire anemometer equipment...Funds were provided by the Army Research Office for the purchase of TSI hot-wire anemometer equipment and a Dantec particle-image velocimetry system

  13. Effect of vortex generators on the power conversion performance and structural dynamic loads of the Mod-2 wind turbine

    Science.gov (United States)

    Sullivan, T. L.

    1984-01-01

    Applying vortex generators from 20 to 100 percent span of the Mod-2 rotor resulted in a projected increase in annual energy capture of 20 percent and reduced the wind speed at which rated power is reached by nearly 3 m/sec. Application of vortex generators from 20 to 70 percent span, the fixed portion of the Mod-2 rotor, resulted in a projected increase in annual energy capture of about half this. This improved performance came at the cost of a small increase in cyclic blade loads in below rated power conditions. Cyclic blade loads were found to correlate well with the change in wind speed during one rotor revolution.

  14. Influence of Rigid Body Motions on Rotor Induced Velocities and Aerodynamic Loads of a Floating Horizontal Axis Wind Turbine

    DEFF Research Database (Denmark)

    de Vaal, Jacobus B.; Hansen, Martin Otto Laver; Moan, Torgeir

    2014-01-01

    This paper discusses the influence of rigid body motions on rotor induced velocities and aerodynamic loads of a floating horizontal axis wind turbine. Analyses are performed with a simplified free wake vortex model specifically aimed at capturing the unsteady and non-uniform inflow typically......, and captures the essential influences of rigid body motions on the rotor loads, induced velocities and wake influence....... experienced by a floating wind turbine. After discussing the simplified model in detail, comparisons are made to a state of the art free wake vortex code, using test cases with prescribed platform motion. It is found that the simplified model compares favourably with a more advanced numerical model...

  15. Multi-Temporal Decomposed Wind and Load Power Models for Electric Energy Systems

    Science.gov (United States)

    Abdel-Karim, Noha

    This thesis is motivated by the recognition that sources of uncertainties in electric power systems are multifold and may have potentially far-reaching effects. In the past, only system load forecast was considered to be the main challenge. More recently, however, the uncertain price of electricity and hard-to-predict power produced by renewable resources, such as wind and solar, are making the operating and planning environment much more challenging. The near-real-time power imbalances are compensated by means of frequency regulation and generally require fast-responding costly resources. Because of this, a more accurate forecast and look-ahead scheduling would result in a reduced need for expensive power balancing. Similarly, long-term planning and seasonal maintenance need to take into account long-term demand forecast as well as how the short-term generation scheduling is done. The better the demand forecast, the more efficient planning will be as well. Moreover, computer algorithms for scheduling and planning are essential in helping the system operators decide what to schedule and planners what to build. This is needed given the overall complexity created by different abilities to adjust the power output of generation technologies, demand uncertainties and by the network delivery constraints. Given the growing presence of major uncertainties, it is likely that the main control applications will use more probabilistic approaches. Today's predominantly deterministic methods will be replaced by methods which account for key uncertainties as decisions are made. It is well-understood that although demand and wind power cannot be predicted at very high accuracy, taking into consideration predictions and scheduling in a look-ahead way over several time horizons generally results in more efficient and reliable utilization, than when decisions are made assuming deterministic, often worst-case scenarios. This change is in approach is going to ultimately require new

  16. Customized DSP-based vibration measurement for wind turbines

    Energy Technology Data Exchange (ETDEWEB)

    LaWhite, N.E.; Cohn, K.E. [Second Wind Inc., Somerville, MA (United States)

    1996-12-31

    As part of its Advanced Distributed Monitoring System (ADMS) project funded by NREL, Second Wind Inc. is developing a new vibration measurement system for use with wind turbines. The system uses low-cost accelerometers originally designed for automobile airbag crash-detection coupled with new software executed on a Digital Signal Processor (DSP) device. The system is envisioned as a means to monitor the mechanical {open_quotes}health{close_quotes} of the wind turbine over its lifetime. In addition the system holds promise as a customized emergency vibration detector. The two goals are very different and it is expected that different software programs will be executed for each function. While a fast Fourier transform (FFT) signature under given operating conditions can yield much information regarding turbine condition, the sampling period and processing requirements make it inappropriate for emergency condition monitoring. This paper briefly reviews the development of prototype DSP and accelerometer hardware. More importantly, it reviews our work to design prototype vibration alarm filters. Two-axis accelerometer test data from the experimental FloWind vertical axis wind turbine is analyzed and used as a development guide. Two levels of signal processing are considered. The first uses narrow band pre-processing filters at key fundamental frequencies such as the 1P, 2P and 3P. The total vibration energy in each frequency band is calculated and evaluated as a possible alarm trigger. In the second level of signal processing, the total vibration energy in each frequency band is further decomposed using the two-axis directional information. Directional statistics are calculated to differentiate between linear translations and circular translations. After analyzing the acceleration statistics for normal and unusual operating conditions, the acceleration processing system described could be used in automatic early detection of fault conditions. 9 figs.

  17. The reliability of the Extra Load Index as a measure of relative load carriage economy.

    Science.gov (United States)

    Hudson, Sean; Cooke, Carlton; Lloyd, Ray

    2017-09-01

    The aim of this study was to measure the reliability of the extra load index (ELI) as a method for assessing relative load carriage economy. Seventeen volunteers (12 males, 5 females) performed walking trials at 3 km·h -1 , 6 km·h -1 and a self-selected speed. Trial conditions were repeated 7 days later to assess test-retest reliability. Trials involved four 4-minute periods of walking, each separated by 5 min of rest. The initial stage was performed unloaded followed in a randomised order by a second unloaded period and walking with backpacks of 7 and 20 kg. Results show ELI values did not differ significantly between trials for any of the speeds (p = 0.46) with either of the additional loads (p = 0.297). The systematic bias, limits of agreement and coefficients of variation were small in all trial conditions. We conclude the ELI appears to be a reliable measure of relative load carriage economy. Practitioner Summary: This paper demonstrates that the ELI is a reliable measure of load carriage economy at a range of walking speeds with both a light and heavy load. The ELI, therefore, represents a useful tool for comparing the relative economy associated with different load carriage systems.

  18. Flow field and load characteristics of the whole MEXICO wind turbine

    DEFF Research Database (Denmark)

    Xu, Haoran; Yang, Hua; Liu, Chao

    2017-01-01

    CFD(Computational Fluid Dynamics) method was used to perform steady numerical simulation investigation on the flow field and load characteristics of MEXICO(Model EXperiment In Controlled cOnditions) wind turbine under non-yawed condition. Circumferentially-Averaged method was used to extract...... the calculated axial, radial and tangential components of velocity along the axial direction, then these components were compared with the experimental data, the compared results show that the computational components agree well with the experimental data and the computational results are reliable. The flow...... characteristics around the blade was analyzed and the points of flow separation were found along the blade, the results show that the points of flow separation move towards trailing edge with the increase of radius. The distribution of vorticity in the wake of MEXICO rotor was also analyzed. The distribution...

  19. Framing Failures in Wood-Frame Hip Roofs under Extreme Wind Loads

    Directory of Open Access Journals (Sweden)

    Sarah A. Stevenson

    2018-02-01

    Full Text Available Wood-frame residential roof failures are among the most common and expensive types of wind damage. Hip roofs are commonly understood to be more resilient during extreme wind in relation to gable roofs. However, inspection of damage survey data from recent tornadoes has revealed a previously unstudied failure mode in which hip roofs suffer partial failure of the framing structure. In the current study, evidence of partial framing failures and statistics of their occurrence are explored and discussed, while the common roof design and construction practice are reviewed. Two-dimensional finite element models are developed to estimate the element-level load effects on hip roof trusses and stick-frame components. The likelihood of failure in each member is defined based on relative demand-to-capacity ratios. Trussed and stick-frame structures are compared to assess the relative performance of the two types of construction. The present analyses verify the common understanding that toenailed roof-to-wall connections are likely to be the most vulnerable elements in the structure of a wood-frame hip roof. However, the results also indicate that certain framing members and connections display significant vulnerability under the same wind uplift, and the possibility of framing failure is not to be discounted. Furthermore, in the case where the roof-to-wall connection uses hurricane straps, certain framing members and joints become the likely points of failure initiation. The analysis results and damage survey observations are used to expand the understanding of wood-frame residential roof failures, as they relate to the Enhanced Fujita Scale and provide assessment of potential gaps in residential design codes.

  20. Expected load spectra of prototype Francis turbines in low-load operation using numerical simulations and site measurements

    Science.gov (United States)

    Eichhorn, M.; Taruffi, A.; Bauer, C.

    2017-04-01

    The operators of hydropower plants are forced to extend the existing operating ranges of their hydraulic machines to remain competitive on the energy market due to the rising amount of wind and solar power. Faster response times and a higher flexibility towards part- and low-load conditions enable a better electric grid control and assure therefore an economic operation of the power plant. The occurring disadvantage is a higher dynamic excitation of affected machine components, especially Francis turbine runners, due to pressure pulsations induced by unsteady flow phenomena (e.g. draft tube vortex ropes). Therefore, fatigue analysis becomes more important even in the design phase of the hydraulic machines to evaluate the static and dynamic load in different operating conditions and to reduce maintenance costs. An approach including a one-way coupled fluid-structure interaction has been already developed using unsteady CFD simulations and transient FEM computations. This is now applied on two Francis turbines with different specific speeds and power ranges, to obtain the load spectra of both machines. The results are compared to strain gauge measurements on the according Francis turbines to validate the overall procedure.

  1. Double-Edge Molecular Technique for Doppler Lidar Wind Measurement

    Science.gov (United States)

    Flesia, Cristina; Korb, C. Laurence

    1998-01-01

    The double-edge lidar technique for measuring the wind using molecular backscatter is described. Two high spectral resolution edge filters are located in the wings of the Rayleigh-Brillouin profile. This doubles the signal change per unit Doppler shift, the sensitivity, and gives nearly a factor of two improvement in measurement accuracy. The use of a crossover region is described where the sensitivity of a molecular and aerosol-based measurement are equal. This desensitizes the molecular measurement to the effects of aerosol scattering over a frequency range of +/- 100 m/s. We give methods for correcting for short-term frequency jitter and drift using a laser reference frequency measurement and methods for long-term frequency correction using a servo control system. The effects of Rayleigh-Brillouin scattering on the measurement are shown to be significant and are included in the analysis. Simulations for a conical scanning satellite-based lidar at 355 nm show an accuracy of 2-3 m/s for altitudes of 2 to 15 km for a 1 km vertical resolution, a satellite altitude of 400 km and a 200 km x 200 km spatial resolution. Results of ground based wind measurements are presented.

  2. Double-edge molecular technique for Doppler lidar wind measurement

    Science.gov (United States)

    Flesia, Cristina; Korb, C. L.

    1998-08-01

    The double-edge lidar technique for measuring the wind based upon using molecular backscatter is described. The technique uses two high spectral resolution edge filters which are located in the wings of the Rayleigh-Brillouin profile. This doubles the signal change per unit Doppler shift, the sensitivity, and gives nearly a factor of two improvement in measurement accuracy relative to the single edge technique. The use of a crossover region is described where the sensitivity of a molecular and aerosol-based measurement are equal. This desensitizes the molecular measurement to the effects of aerosol scattering over a frequency range of plus or minus 100 m/s. We give methods for correcting for short- term, shot to shot, frequency jitter and drift using a laser reference frequency measurement and methods for long-term frequency correction using a servo control system. The effects of Rayleigh-Brillouin scattering on the measurement are shown to be significant and are included in the analysis. Simulations for a conical scanning satellite-based lidar at 355 nm show an accuracy of 2 - 3 m/s for altitudes of 2 to 15 km for a 1 km vertical resolution, a satellite altitude of 400 km and a 200 km X 200 km spatial resolution. Results for recent wind measurements, which show an accuracy of 1 m/s up to an altitude of 10 km, are given.

  3. Mesospheric winds measurements using three meteor radars in Brazil

    Science.gov (United States)

    Batista, Paulo; Clemesha, Barclay; Fátima Andrioli, Vânia; Paulino, Ana Roberta; Buriti, Ricardo; Schuch, Nelson Jorge

    Three meteor radars of the SkiYmet type have been installed in Brazil covering low, tropical and sub-tropical latitudes. The first at Cachoeira Paulista(22.7 S, 45.0 W) started in march 1999, the second at Cariri(7.4 S, 36.5 W) in May, 2005, and the last one at Santa Maria( 29.7 S, 53.8 W) in December, 2005. Coincident periods of measurements permitted the determination of the Mean Winds, Planetary Waves, Tides and Gravity Wave Variances for these different latitudes and their comparison. Amplitude and phase structures are similar for Cachoeira Paulista and Santa Maria, but differ from the near-equatorial site Cariri. Also the Lunar Semidiurnal Tides have been studied at the three sites for the period January 2005 to December 2008. Amplitudes between 1 and 8 m/s were determined with the meridional winds being larger than the zonal in the three sites. Wind measurements have been used also as subsidiary data in the studies involving the sodium layer and the mesospheric airglow though lidar, photometers and imagers.

  4. Comparisons between LES and Wind Tunnel Hot-Wire Measurements

    DEFF Research Database (Denmark)

    Zhu, Wei Jun; Shen, Wen Zhong; Sørensen, Jens Nørkær

    2012-01-01

    is constructed in a wind tunnel similar to the LM wind tunnel where the experiment for an NACA 0015 airfoil was carried out. The goal of this study is to validate the mixed scale SGS turbulence model against detailed measurements. Simulations are performed with the in-house EllipSys3D code on high performance...... computers. The stability and accuracy of the LES simulations are studied on various mesh configurations. The spanwise grid spacing is found important to produce correct flow disturbances along the airfoil span, which can affect the turbulent energy distribution.......Large-eddy simulations (LES) are carried out for flows over a NACA 0015 airfoil at AoA = 8o and a chord based Reynolds number of 1.71 × 106. To accurately simulate the complex flow on the suction side of the airfoil, a reasonably large number of grid points is required. The computational mesh...

  5. An experimental study on a suction flow control method to reduce the unsteadiness of the wind loads acting on a circular cylinder

    Science.gov (United States)

    Chen, Wen-Li; Li, Hui; Hu, Hui

    2014-04-01

    An experimental investigation was conducted to assess the effectiveness of a suction flow control method for vortex-induced vibration (VIV) suppression. The flow control method uses a limited number of isolated suction holes to manipulate the vortex shedding in the wake behind a circular cylinder in order to reduce the unsteadiness of the dynamic wind loads acting on the cylinder. The experimental study was performed at Re ≈ 3.0 × 104, i.e., in the typical Reynolds number range of VIV for the cables of cable-stayed bridges. In addition to measuring the surface pressure distributions to determine the resultant dynamic wind loads acting on the test model, a digital particle image velocimetry system was used to conduct detailed flow field measurements to reveal the changes in the shedding process of the unsteady wake vortex structures from the test model with and without the suction flow control. The effects of important controlling parameters (i.e., the azimuthal locations of the suction holes in respect to the oncoming airflow, the spanwise spacing between the suction holes, and the suction flow rate through the suction holes) on the wake flow characteristics, the surface pressure distributions, and the resultant dynamic wind loads were assessed quantitatively. While a higher suction flow rate and smaller spanwise spacing between the suction holes were beneficial to the effectiveness of the suction flow control, the azimuthal locations of the suction holes were found to be very critical for reducing the fluctuating amplitudes of the dynamic wind loads acting on the test model using the suction flow control method. With the suction holes located at the proper azimuthal locations on the test model (i.e., at the azimuthal angle of θ = 90° and 270° for the present study), the characteristics of the wake flow behind the test model were found to change significantly along the entire span of the test model, even though only a limited number of the isolated suction

  6. Sensitivity analysis of nacelle lidar free stream wind speed measurements to wind-induction reconstruction model and lidar range configuration

    DEFF Research Database (Denmark)

    Svensson, Elin; Borraccino, Antoine; Meyer Forsting, Alexander Raul

    configurations. The wind speeds were reconstructed using both a onedimensional and two-dimensional induction model to test the sensitivity towards the wind-induction model. In all cases, the sensitivity of the reconstructed wind speed was determined from the wind speed error and root mean square error (RMSE...... based on the NKE sensitivity analysis results. Based on these results, it is recommended to configure nacelle lidars to measure at approximately 3-5 ranges. The minimum distance should be configured to roughly 0.5 rotor diameters (Drot) while it is recommended that the maximum range lay within 1-1.5Drot...

  7. Measurement of global oceanic winds from Seasat-SMMR and its comparison with Seasat-SASS and ALT derived winds

    Science.gov (United States)

    Pandey, Prem C.

    1987-01-01

    The retrieval of ocean-surface wind speed from different channel combinations of Seasat SMMR measurements is demonstrated. Wind speeds derived using the best two channel subsets (10.6 H and 18.0 V) were compared with in situ data collected during the Joint Air-Sea Interaction (JASIN) experiment and an rms difference of 1.5 m/s was found. Global maps of wind speed generated with the present algorithm show that the averaged winds are arranged in well-ordered belts.

  8. Utgrunden off-shore wind farm - Measurements of underwater noise

    International Nuclear Information System (INIS)

    Lindell, Hans

    2003-07-01

    Airicole, GE Wind Energy and SEAS/Energi E2 have initiated this project in order to achieve a better understanding on how offshore based wind farms effect the underwater noise. The main reason is to gain knowledge on how marine wildlife could be effected by this kind of installation. The measurements were performed at Utgrunden wind farm that is situated at the reef Utgrunden on the Swedish southeast coast. The farm consists of seven 1,5 MW turbines. Three hydrophones registered the underwater sound and four accelerometers the tower vibrations. The measurement campaign was conducted during a period from November 2002 to February 2003. The objectives with this project is to answer the following issues and its results are: 1. What is the character of sound from a single power station? - The turbines radiate sound mainly at a few dominating frequencies from 30 Hz up to 800 Hz. At frequencies below 3 Hz no contribution from the turbines can be detected due to the high background level from the waves and the low tower vibration level. 2. What are the sound generating mechanisms in the turbine? - Gearbox mesh frequency vibrations that are transmitted via the tower structure and radiated out to the water mainly generate the sound. Airborne blade sound is effectively dampened in the transition from air to water. 3. How does the sound attenuate with increasing distance at different frequencies? - The average attenuation per doubled distance for frequencies between 31 Hz and 722 Hz is approximately 4 dB in the measured positions. No clear frequency dependence could be found. 4. How does the sound pressure level vary with increasing wind speed? - With increasing wind speed, the sound pressure level increases and the dominating frequencies move upward due to increasing turbine rotational speed. 5. How does sound from different power stations interfere with each other and influence the over all sound image? - No clear tendencies of interference could be observed in this study

  9. Time-domain parameter identification of aeroelastic loads by forced-vibration method for response of flexible structures subject to transient wind

    Science.gov (United States)

    Cao, Bochao

    Slender structures representing civil, mechanical and aerospace systems such as long-span bridges, high-rise buildings, stay cables, power-line cables, high light mast poles, crane-booms and aircraft wings could experience vortex-induced and buffeting excitations below their design wind speeds and divergent self-excited oscillations (flutter) beyond a critical wind speed because these are flexible. Traditional linear aerodynamic theories that are routinely applied for their response prediction are not valid in the galloping, or near-flutter regime, where large-amplitude vibrations could occur and during non-stationary and transient wind excitations that occur, for example, during hurricanes, thunderstorms and gust fronts. The linear aerodynamic load formulation for lift, drag and moment are expressed in terms of aerodynamic functions in frequency domain that are valid for straight-line winds which are stationary or weakly-stationary. Application of the frequency domain formulation is restricted from use in the nonlinear and transient domain because these are valid for linear models and stationary wind. The time-domain aerodynamic force formulations are suitable for finite element modeling, feedback-dependent structural control mechanism, fatigue-life prediction, and above all modeling of transient structural behavior during non-stationary wind phenomena. This has motivated the developing of time-domain models of aerodynamic loads that are in parallel to the existing frequency-dependent models. Parameters defining these time-domain models can be now extracted from wind tunnel tests, for example, the Rational Function Coefficients defining the self-excited wind loads can be extracted using section model tests using the free vibration technique. However, the free vibration method has some limitations because it is difficult to apply at high wind speeds, in turbulent wind environment, or on unstable cross sections with negative aerodynamic damping. In the current

  10. Design of DC-DC Converter and its Control for a Wind Generation System Connected to an Isolated Load

    Directory of Open Access Journals (Sweden)

    Carlos A. Ramírez Gómez

    2013-11-01

    Full Text Available A method to design a Buck converter and its control, which are associated to a wind generation system that is feeding an isolated load, is presented in this paper. To design the converter a Thevenin equivalent is deduced, which represents the behavior of the wind turbine, the permanent magnet synchronous generator, and the rectifier. The design of the converter elements guarantees input/output voltages and inductor current ripples of 5 % or less. The output voltage control is developed with a proportional-integral-derivative controller and as design criteria a damping of 0,707 and cutoff frequency of 1/5 converter commutation frequency are selected. The designed controller regulates the output voltage faced load perturbations and wind speed variations. 

  11. Air-Loads Prediction of a UH-60A Rotor inside the 40- by 80-Foot Wind Tunnel

    Science.gov (United States)

    Chang, I-Chung; Romander, Ethan A.; Potsdam, Mark; Yeo, Hyeonsoo

    2010-01-01

    The presented research extends the capability of a loose coupling computational fluid dynamics (CFD) and computational structure dynamics (CSD) code to calculate the flow-field around a rotor and test stand mounted inside a wind tunnel. Comparison of predicted air-load results for a full-scale UH-60A rotor recently tested inside the National Full-Scale Aerodynamics Complex (NFAC) 40- by 80-Foot Wind Tunnel at Ames Research Center and in free-air flight are made for three challenging flight data points from the earlier conducted UH-60A Air-loads Program. Overall results show that the extension of the coupled CFD/CSD code to the wind-tunnel environment is generally successful.

  12. The effect of real-time pricing on load shifting in a highly renewable power system dominated by generation from the renewable sources of wind and photovoltaics

    Science.gov (United States)

    Kies, Alexander; Brown, Tom; Schlachtberger, David; Schramm, Stefan

    2017-04-01

    The supply-demand imbalance is a major concern in the presence of large shares of highly variable renewable generation from sources like wind and photovoltaics (PV) in power systems. Other than the measures on the generation side, such as flexible backup generation or energy storage, sector coupling or demand side management are the most likely option to counter imbalances, therefore to ease the integration of renewable generation. Demand side management usually refers to load shifting, which comprises the reaction of electricity consumers to price fluctuations. In this work, we derive a novel methodology to model the interplay of load shifting and provided incentives via real-time pricing in highly renewable power systems. We use weather data to simulate generation from the renewable sources of wind and photovoltaics, as well as historical load data, split into different consumption categories, such as, heating, cooling, domestic, etc., to model a simplified power system. Together with renewable power forecast data, a simple market model and approaches to incorporate sector coupling [1] and load shifting [2,3], we model the interplay of incentives and load shifting for different scenarios (e.g., in dependency of the risk-aversion of consumers or the forecast horizon) and demonstrate the practical benefits of load shifting. First, we introduce the novel methodology and compare it with existing approaches. Secondly, we show results of numerical simulations on the effects of load shifting: It supports the integration of PV power by providing a storage, which characteristics can be described as "daily" and provides a significant amount of balancing potential. Lastly, we propose an experimental setup to obtain empirical data on end-consumer load-shifting behaviour in response to price incentives. References [1] Brown, T., Schlachtberger, D., Kies. A., Greiner, M., Sector coupling in a highly renewable European energy system, Proc. of the 15th International Workshop on

  13. Study of wind change for the development of loads reduction techniques for the space shuttle

    Science.gov (United States)

    Adelfang, S. I.

    1987-01-01

    Wind change statistics are analyzed for Vandenberg AFB, California (VAFB) and Kennedy Space Center, Florida (KSC). Means and standard deviations of wind component change and vector wind change modulus within 3-9 and 9-16 km altitude bands are tabulated. The contribution to 3.5 hr wind component change by wind perturbations in various wavelength bands is evaluated. Probability distributions of maximum 3.5 hr wind change in an altitude band are presented and a model for wind change at a specified altitude is tested with data derived from six data bases from VAFB and Santa Monica, California.

  14. EA Annex XX. Comparison between calculations and measurements on a wind turbine in the NASA-Ames wind tunnel

    Energy Technology Data Exchange (ETDEWEB)

    Schepers, J.G. [ECN Wind Energy, Petten (Netherlands)

    2007-11-15

    This report describes a study in which calculational results from ECN's aeroelastic code PHATAS and the free wake lifting line code AWSM are compared with wind tunnel measurements which were carried out by NREL on a wind turbine, placed in the large NASA-Ames wind tunnel. Measurements have been taken at a large variety of conditions but in this report data at non-yawed conditions are considered only. The study was carried out within the framework IEA Annex XX 'Analysis of NASA-Ames windtunnel measurements'.

  15. Wind atlas for Egypt: Measurements, micro- and mesoscale modelling

    DEFF Research Database (Denmark)

    Mortensen, N.G.; Hansen, J.C.; Badger, J.

    2006-01-01

    with SRTM 3 elevation data and satellite imagery, provide the means for immediate WAsP wind resource assessments anywhere in Egypt. In addition to the very high wind resource in the Gulfs of Suez and Aqaba, the wind atlas has discovered a large region in the Western Desert with a fairly high resource......The results of a comprehensive, 8-year wind resource assessment programme in Egypt are presented. The objective has been to provide reliable and accurate wind atlas data sets for evaluating the potential wind power output from large electricity-producing wind turbine installations. The regional...... wind climates of Egypt have been determined by two independent methods: a traditional wind atlas based on observations from more than 30 stations all over Egypt, and a numerical wind atlas based on long-term reanalysis data and a mesoscale model (KAMM). The mean absolute error comparing the two methods...

  16. Update on the Comparison of Second-Order Loads on a Tension Leg Platform for Wind Turbines: Preprint

    Energy Technology Data Exchange (ETDEWEB)

    Gueydon, Sebastien; Jonkman, Jason

    2016-08-01

    In comparison to other kinds of floaters (like a spar or a semisubmersible), the tension leg platform has several notable advantages: its vertical motions are negligible, its weight is lighter, and its mooring system's footprint is smaller. Although a tension leg platform has a negligible response to first-order vertical wave loads, the second-order wave loads need to be addressed. This paper follows up on a verification study of second-order wave loads on a tension leg platform for wind turbines done by the Maritime Research Institute of The Netherlands and National Renewable Energy Laboratory and it brings some corrections to its conclusions.

  17. Simulation of the Impact of New Air-Based Ocean Surface Wind Measurements on H*Wind Analyses

    Science.gov (United States)

    Miller, Timothy; Atlas, Robert; Black, Peter; Case, Jonathan; Chen, Shuyi; Hood, Robbie; Jones, Linwood; Ruff, Chris; Uhlhorn, Eric

    2008-01-01

    The H'Wind analysis, a product of the Hurricane Research Division of NOAA's Atlantic Oceanographic and Meteorological Laboratory, brings together wind measurements from a variety of observation platforms into an objective analysis of the distribution of wind speeds in a tropical cyclone. This product is designed to improve understanding of the extent and strength of the wind field, and to improve the assessment of hurricane intensity. See http://www.aoml.noaa.gov/hrd/data sub/wind.html. The Hurricane Imaging Radiometer (HIRad) is a new airborne microwave remote sensor for hurricane observations that is currently under development by NASA Marshall Space Flight Center, NOAA Hurricane Research Division, the University of Central Florida and the University of Michigan. HIRad is being designed to enhance the real-time airborne ocean surface winds observation capabilities of NOAA and USAF Weather Squadron hurricane hunter aircraft using the operational airborne Stepped Frequency Microwave Radiometer (SFMR). Unlike SFMR, which measures wind speed and rain rate along the ground track directly beneath the aircraft, HIRad will provide images of the surface wind and rain field over a wide swath (approx. 3 x the aircraft altitude). The instrument is described in a paper presented to the Hurricanes and Tropical Meteorology Symposium. The present paper describes a set of Observing System Simulation Experiments (OSSEs) in which measurements from the new instrument as well as those from existing instruments (air, surface, and space-based) are simulated from the output of a numerical model from the University of Miami and those results are used to construct H*Wind analyses. Evaluations will be presented on the impact of the HIRad instrument on H'Wind analyses, both in terms of adding it to the full suite of current measurements, as well as using it to replace instrument(s) that may not be functioning at the future tame the HIRad instrument is implemented.

  18. Estimating the Wind Resource in Uttarakhand: Comparison of Dynamic Downscaling with Doppler Lidar Wind Measurements

    Energy Technology Data Exchange (ETDEWEB)

    Lundquist, J. K. [National Renewable Energy Lab. (NREL), Golden, CO (United States); Pukayastha, A. [National Renewable Energy Lab. (NREL), Golden, CO (United States); Martin, C. [Univ. of Colorado, Boulder, CO (United States); Newsom, R. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States)

    2014-03-01

    Previous estimates of the wind resources in Uttarakhand, India, suggest minimal wind resources in this region. To explore whether or not the complex terrain in fact provides localized regions of wind resource, the authors of this study employed a dynamic down scaling method with the Weather Research and Forecasting model, providing detailed estimates of winds at approximately 1 km resolution in the finest nested simulation.

  19. Research and analysis on response characteristics of bracket-line coupling system under wind load

    Science.gov (United States)

    Jiayu, Zhao; Qing, Sun

    2018-01-01

    In this paper, a three-dimensional finite element model of bracket-line coupling system is established based on ANSYS software. Using the wind velocity time series which is generated by MATLAB as a power input, by comparing and analyzing the influence of different wind speeds and different wind attack angles, it is found that when 0 degree wind acts on the structure, wires have a certain damping effect in the bracket-line coupling system and at the same wind speed, the 90 degree direction is the most unfavorable wind direction for the whole structure according to the three kinds of angle wind calculated at present. In the bracket-line coupling system, the bracket structure is more sensitive to the increase of wind speed while the conductors are more sensitive to the change of wind attack angle.

  20. Wind Field Reconstruction from Nacelle-Mounted Lidars Short Range Measurements

    OpenAIRE

    Borraccino, Antoine; Schlipf, David; Haizmann, Florian; Wagner, Rozenn

    2017-01-01

    Profiling nacelle lidars probe the wind at several heights and several distances upstream of the rotor. The development of such lidar systems is relatively recent, and it is still unclear how to condense the lidar raw measurements into useful wind field characteristics such as speed, direction, vertical and longitudinal gradients (wind shear). In this paper, we demonstrate an innovative method to estimate wind field characteristics using nacelle lidar measurements taken within the induction z...

  1. Comparison of Model Output of Wind and Wave Parameters with Spaceborne Altimeter Measurements

    National Research Council Canada - National Science Library

    Hwang, Paul

    1998-01-01

    .... While comparisons with point measurements from discrete and sparsely distributed wave buoys provide some measure of statistical confidence, the spatial distribution of the modeled wind and wave...

  2. Wind turbine influence on surfers wind conditions at Hanstholm

    DEFF Research Database (Denmark)

    Larsen, Torben J.; Andersen, Søren Juhl

    alter the wind conditions on the lee side, which is an important area for wind and kite surfers. The Dynamic Wake Meander Model is used to investigate the wind conditions north east of the planned new turbines at Hanstholm covering a surf area from a location called “Fish Factory” to a location called...... “Hamborg”. This model, which predicts instationary wind conditions behind one or more wind turbines, has previously been used to predict the changed power and load conditions for wind turbines in wind farm conditions. Avery fine agreement to measurements is seen and the model is therefore considered...

  3. Long-duration heat load measurement approach by novel apparatus design and highly efficient algorithm

    International Nuclear Information System (INIS)

    Zhu, Yanwei; Yi, Fajun; Meng, Songhe; Zhuo, Lijun; Pan, Weizhen

    2017-01-01

    Improving the surface heat load measurement technique for vehicles in aerodynamic heating environments is imperative, regarding aspects of both the apparatus design and identification efficiency. A simple novel apparatus is designed for heat load identification, taking into account the lessons learned from several aerodynamic heating measurement devices. An inverse finite difference scheme (invFDM) for the apparatus is studied to identify its surface heat flux from the interior temperature measurements with high efficiency. A weighted piecewise regression filter is also proposed for temperature measurement prefiltering. Preliminary verification of the invFDM scheme and the filter is accomplished via numerical simulation experiments. Three specific pieces of apparatus have been concretely designed and fabricated using different sensing materials. The aerodynamic heating process is simulated by an inductively coupled plasma wind tunnel facility. The identification of surface temperature and heat flux from the temperature measurements is performed by invFDM. The results validate the high efficiency, reliability and feasibility of heat load measurements with different heat flux levels utilizing the designed apparatus and proposed method. (paper)

  4. Long-duration heat load measurement approach by novel apparatus design and highly efficient algorithm

    Science.gov (United States)

    Zhu, Yanwei; Yi, Fajun; Meng, Songhe; Zhuo, Lijun; Pan, Weizhen

    2017-11-01

    Improving the surface heat load measurement technique for vehicles in aerodynamic heating environments is imperative, regarding aspects of both the apparatus design and identification efficiency. A simple novel apparatus is designed for heat load identification, taking into account the lessons learned from several aerodynamic heating measurement devices. An inverse finite difference scheme (invFDM) for the apparatus is studied to identify its surface heat flux from the interior temperature measurements with high efficiency. A weighted piecewise regression filter is also proposed for temperature measurement prefiltering. Preliminary verification of the invFDM scheme and the filter is accomplished via numerical simulation experiments. Three specific pieces of apparatus have been concretely designed and fabricated using different sensing materials. The aerodynamic heating process is simulated by an inductively coupled plasma wind tunnel facility. The identification of surface temperature and heat flux from the temperature measurements is performed by invFDM. The results validate the high efficiency, reliability and feasibility of heat load measurements with different heat flux levels utilizing the designed apparatus and proposed method.

  5. The influence of the Wind Speed Profile on Wind Turbine Performance Measurements

    DEFF Research Database (Denmark)

    Wagner, Rozenn; Antoniou, Ioannis; Pedersen, Søren M.

    2009-01-01

    . Assuming a certain turbine hub height, the profiles with hub-height wind speeds between 6 m s-1 and 8 m s-1 are normalized at 7 m s-1 and grouped to a number of mean shear profiles. The energy in the profiles varies considerably for the same hub-height wind speed. These profiles are then used as input...... the swept rotor area would allow the determination of the electrical power as a function of an equivalent wind speed where wind shear and turbulence intensity are taken into account. Electrical power is found to correlate significantly better to the equivalent wind speed than to the single point hub...

  6. Economic perspective of hybrid wind-diesel technology for commercial loads of Dhahran Saudi Arabia: A step towards sustainable future

    Directory of Open Access Journals (Sweden)

    Shaahid S.M.

    2015-01-01

    Full Text Available The governments world-wide are deliberating to promote renewable energy sources such as wind to mitigate increasing demand of energy and to overcome effects of pollution due to to use of fossil fuels. Integration of wind turbine generators (WTG with the diesel plants is pursued widely to reduce dependence on fossil-fuels and to reduce carbon emissions. Literature indicates that commercial/residential buildings in the Kingdom of Saudi Arabia (K.S.A consume an estimated 10 - 40% of the total electric energy generated. The aim of this study is to analyze wind-speed data of Dhahran (East-Coast, K.S.A. to assess the economic feasibility of utilizing hybrid wind-diesel power systems to meet the load requirements of a typical commercial building (with annual electrical energy demand of 620,000 kWh. The monthly average wind speeds range from 3.3 to 5.6 m/s. The hybrid systems simulated consist of different combinations of 100 kW commercial WTG supplemented with diesel generators. NREL’s (HOMER Energy’s HOMER software has been employed to perform the techno-economic analysis. The simulation results indicate that for a hybrid system comprising of 100 kW wind capacity together with 175 kW diesel system, the wind penetration (at 37 m hub-height, with 0% annual capacity shortage is 25%. The cost of generating energy (COE, $/kWh from this hybrid wind-diesel system has been found to be 0.121 $/kWh (assuming diesel fuel price of 0.1$/liter. The study exhibits that for a given hybrid configuration, the number of operational hours of diesel gensets decreases with increase in wind farm capacity. Emphasis has also been placed on wind penetration, un-met load, energy production and COE, excess electricity generation, percentage fuel savings and reduction in carbon emissions (relative to diesel-only situation of different hybrid systems, cost break-down of wind-diesel systems, COE of different hybrid systems, etc.

  7. Wind turbine pitch optimization

    DEFF Research Database (Denmark)

    Biegel, Benjamin; Juelsgaard, Morten; Stoustrup, Jakob

    2011-01-01

    We consider a static wind model for a three-bladed, horizontal-axis, pitch-controlled wind turbine. When placed in a wind field, the turbine experiences several mechanical loads, which generate power but also create structural fatigue. We address the problem of finding blade pitch profiles......% compared to any constant pitch profile while sacrificing at most 7% of the maximum attainable output power. Using iterative learning, we show that very similar performance can be achieved by using only load measurements, with no knowledge of the wind field or wind turbine model....... for maximizing power production while simultaneously minimizing fatigue loads. In this paper, we show how this problem can be approximately solved using convex optimization. When there is full knowledge of the wind field, numerical simulations show that force and torque RMS variation can be reduced by over 96...

  8. Upgrading the Arecibo Potassium Lidar Receiver for Meridional Wind Measurements

    Science.gov (United States)

    Piccone, A. N.; Lautenbach, J.

    2017-12-01

    Lidar can be used to measure a plethora of variables: temperature, density of metals, and wind. This REU project is focused on the set up of a semi steerable telescope that will allow the measurement of meridional wind in the mesosphere (80-105 km) with Arecibo Observatory's potassium resonance lidar. This includes the basic design concept of a steering system that is able to turn the telescope to a maximum of 40°, alignment of the mirror with the telescope frame to find the correct focusing, and the triggering and programming of a CCD camera. The CCD camera's purpose is twofold: looking though the telescope and matching the stars in the field of view with a star map to accurately calibrate the steering system and determining the laser beam properties and position. Using LabVIEW, the frames from the CCD camera can be analyzed to identify the most intense pixel in the image (and therefore the brightest point in the laser beam or stars) by plotting average pixel values per row and column and locating the peaks of these plots. The location of this pixel can then be plotted, determining the jitter in the laser and position within the field of view of the telescope.

  9. Aeroservoelastic Testing of Free Flying Wind Tunnel Models Part 2: A Centerline Supported Fullspan Model Tested for Gust Load Alleviation

    Science.gov (United States)

    Scott, Robert C.; Vetter, Travis K.; Penning, Kevin B.; Coulson, David A.; Heeg, Jennifer

    2014-01-01

    This is part 2 of a two part document. Part 1 is titled: "Aeroservoelastic Testing of Free Flying Wind Tunnel Models Part 1: A Sidewall Supported Semispan Model Tested for Gust Load Alleviation and Flutter Suppression." A team comprised of the Air Force Research Laboratory (AFRL), Boeing, and the NASA Langley Research Center conducted three aeroservoelastic wind tunnel tests in the Transonic Dynamics Tunnel to demonstrate active control technologies relevant to large, flexible vehicles. In the first of these three tests, a full-span, aeroelastically scaled, wind tunnel model of a joined wing SensorCraft vehicle was mounted to a force balance to acquire a basic aerodynamic data set. In the second and third tests, the same wind tunnel model was mated to a new, two degree of freedom, beam mount. This mount allowed the full-span model to translate vertically and pitch. Trimmed flight at10 percent static margin and gust load alleviation were successfully demonstrated. The rigid body degrees of freedom required that the model be flown in the wind tunnel using an active control system. This risky mode of testing necessitated that a model arrestment system be integrated into the new mount. The safe and successful completion of these free-flying tests required the development and integration of custom hardware and software. This paper describes the many systems, software, and procedures that were developed as part of this effort. The balance and free flying wind tunnel tests will be summarized. The design of the trim and gust load alleviation control laws along with the associated results will also be discussed.

  10. Dependence of thermospheric zonal winds on solar flux, geomagnetic activity, and hemisphere as measured by CHAMP

    Science.gov (United States)

    Zhang, Xiaofang; Liu, Libo; Liu, Songtao

    2017-08-01

    The thermospheric zonal winds measured by the CHAllenging Minisatellite Payload (CHAMP) satellite are used to statistically determine the climatology under quiet and active geomagnetic conditions. By collectively analyzing the bin-averaged wind trend with F10.7 and the solar-induced difference in wind structures, the solar flux dependence of global thermosphere zonal wind is determined. The increase of solar flux enhances the eastward winds at low latitudes from dusk to midnight. The increased ion drag reduces the nighttime eastward wind in the subauroral latitudes, and the daytime westward winds from 06 to 08 MLT at all latitudes decrease with increasing solar flux. Zonal winds show coupled seasonal/extreme ultraviolet (EUV) dependency. The equatorial zonal winds from 18 to 04 magnetic local time (MLT) indicate weaker eastward winds during the June solstice at high solar flux levels. Quiet time eastward winds at subauroral latitudes from 16 to 20 MLT are further decreased in the winter hemisphere. Influenced by asymmetries in solar illumination and the magnetic field, zonal winds show hemispheric asymmetries. Quiet daytime winds are additionally influenced by solar illumination effects, and the westward winds at the middle and subauroral latitudes are always stronger in the summer. The nighttime eastward winds are higher in the winter hemisphere during the solstices, as in the Southern Hemisphere during equinoxes, with the winter-summer asymmetry lessened or receding at the solar maxima. Storm-induced subauroral westward disturbance winds are higher in the summer hemisphere and in the Northern Hemisphere during equinoxes. At a high level of solar flux, the westward disturbance winds are comparable in the two hemispheres during December solstice. Geomagnetic disturbance wind observations from CHAMP agree well with the empirical geomagnetic disturbance wind model, except for stronger subauroral westward jets. Westward winds during the afternoon may be enhanced in

  11. Induced Torques on Synchronous Generators from Operation of Wind Power Plant based on Full-Load Converter Interfaced Wind Turbines

    DEFF Research Database (Denmark)

    Knüppel, Thyge; Nielsen, Jørgen N.; Jensen, Kim H.

    2011-01-01

    It is expected that large wind power plants (WPP) contribute to stable and reliable operation of the electric power system. This includes participation with delivery of system services such as voltage and frequency support. With variable-speed WPPs this can be achieved by adding auxiliary control...... be predicted with the presented method. The work is based on a nonlinear, dynamic model of the 3.6 MW Siemens Wind Power wind turbine....... properties from the closed-loop system. A method based on induced torque coefficients (ITC) is here presented for assessing the closed-loop behavior from the open-loop system. Results are presented using both modal analysis and ITC prediction, which demonstrate that the dominant closed-loop behavior can...

  12. Measurements and modeling of the wind profile up to 600 meters at a flat coastal site

    DEFF Research Database (Denmark)

    Batchvarova, Ekaterina; Gryning, Sven-Erik; Floors, Rogier Ralph

    2014-01-01

    This study shows long-term ABL wind profile features by comparing long-range wind lidar measurements and the output from a mesoscale model. The study is based on one-year pulsed lidar (Wind Cube 70) measurements of wind speed and direction from 100 to 600 meters with vertical resolution of 50......) and shape (k) parameters of the Weibull dis-tribution above 100 m. The latter signifies that the model suggests a wider distri-bution in the wind speed compared to measurements....... meters and time resolution of 10 minutes at a coastal site on the West coast of Denmark and WRF ARW (NCAR) simulations for the same period. The model evaluation is performed based on wind speed, wind direction, as well as statistical parameters of the Weibull distribution of the wind speed time series...

  13. Detection and Use of Load and Gage Output Repeats of Wind Tunnel Strain-Gage Balance Data

    Science.gov (United States)

    Ulbrich, N.

    2017-01-01

    Criteria are discussed that may be used for the detection of load and gage output repeats of wind tunnel strain-gage balance data. First, empirical thresholds are introduced that help determine if the loads or electrical outputs of a pair of balance calibration or check load data points match. A threshold of 0.01 percent of the load capacity is suggested for the identification of matching loads. Similarly, a threshold of 0.1 microV/V is recommended for the identification of matching electrical outputs. Two examples for the use of load and output repeats are discussed to illustrate benefits of the implementation of a repeat point detection algorithm in a balance data analysis software package. The first example uses the suggested load threshold to identify repeat data points that may be used to compute pure errors of the balance loads. This type of analysis may reveal hidden data quality issues that could potentially be avoided by making calibration process improvements. The second example uses the electrical output threshold for the identification of balance fouling. Data from the calibration of a six-component force balance is used to illustrate the calculation of the pure error of the balance loads.

  14. Implementation of internal model based control and individual pitch control to reduce fatigue loads and tower vibrations in wind turbines

    Science.gov (United States)

    Mohammadi, Ebrahim; Fadaeinedjad, Roohollah; Moschopoulos, Gerry

    2018-05-01

    Vibration control and fatigue loads reduction are important issues in large-scale wind turbines. Identifying the vibration frequencies and tuning dampers and controllers at these frequencies are major concerns in many control methods. In this paper, an internal model control (IMC) method with an adaptive algorithm is implemented to first identify the vibration frequency of the wind turbine tower and then to cancel the vibration signal. Standard individual pitch control (IPC) is also implemented to compare the performance of the controllers in term of fatigue loads reduction. Finally, the performance of the system when both controllers are implemented together is evaluated. Simulation results demonstrate that using only IMC or IPC alone has advantages and can reduce fatigue loads on specific components. IMC can identify and suppress tower vibrations in both fore-aft and side-to-side directions, whereas, IPC can reduce fatigue loads on blades, shaft and yaw bearings. When both IMC and IPC are implemented together, the advantages of both controllers can be used. The aforementioned analysis and comparisons were not studied in literature and this study fills this gap. FAST, AreoDyn and Simulink are used to simulate the mechanical, aerodynamic and electrical aspects of wind turbine.

  15. Systematic Wind Farm Measurement Data Filtering Tool for Wake Model Calibration

    DEFF Research Database (Denmark)

    Rethore, Pierre-Elouan Mikael; Johansen, Nicholas Alan; Frandsen, Sten Tronæs

    A set of systematic methods for characterizing the sensors of a wind farm and using these sensors to filter more accurately large volumes of measurement data is proposed. These methods are based on the experience accumulated while processing datasets from two large offshore wind farms in Denmark....... Both wake model developers and wind farm operators seeking to determine how the wind farm operates under specific conditions can find these methods valuable. The methods are general and can be applied successfully to any wind farm by taking into consideration the specific aspects of each wind farm....

  16. Wind Field Reconstruction from Nacelle-Mounted Lidars Short Range Measurements

    DEFF Research Database (Denmark)

    Borraccino, Antoine; Schlipf, David; Haizmann, Florian

    2017-01-01

    IR Dual Mode). The reconstructed wind speed was within 0.5 % of the wind speed measured with a mast-top-mounted cup anemometer at 2.5 rotor diameters upstream of the turbine. The technique described in this paper overcomes measurement range limitations of the currently available nacelle lidar technology.......Profiling nacelle lidars probe the wind at several heights and several distances upstream of the rotor. The development of such lidar systems is relatively recent, and it is still unclear how to condense the lidar raw measurements into useful wind field characteristics such as speed, direction......, vertical and longitudinal gradients (wind shear). In this paper, we demonstrate an innovative method to estimate wind field characteristics using nacelle lidar measurements taken within the induction zone. Model-fitting wind field reconstruction techniques are applied to nacelle lidar measurements taken...

  17. Iterative data-driven load control for flexible wind turbine rotors

    NARCIS (Netherlands)

    Navalkar, S.T.

    2016-01-01

    Wind energy has reached a high degree ofmaturity: for wind-rich onshore locations, it is already competitive with conventional energy sources. However, for low-wind, remote and offshore regions, research efforts are still required to enhance its economic viability. While it is possible to reduce the

  18. Review of climatic input data for wind load design in accordance with SANS 10160-3

    CSIR Research Space (South Africa)

    Goliger, Adam MW

    2017-12-01

    Full Text Available background information on South African conditions. The need for updating the map for the free field wind speed is related also to the improved representation of the mixed and complex strong wind climate of the country. Furthermore, strong wind probability...

  19. Adding concentrated solar power plants to wind farms to achieve a good utility electrical load match

    Science.gov (United States)

    Texas has the greatest installed wind turbine capacity of any state in the United States, the percentage of wind capacity approaches 10% of the utilities capacity (in 2010 the total wind generated capacity in Texas was 8%). It is becomimg increasingly difficult for the utility to balance the elec...

  20. A method for measuring mean wind velocities in a canyon with tracer balloons

    Science.gov (United States)

    Sheih, C. M.; Billman, B. J.; Depaul, F. T.

    1985-08-01

    A method using balloons as tracers for measuring mean wind velocity in street canyons or mountain valleys has been developed. Tests of the method with numerical experiments showed that the method reproduced an assumed wind field quite well provided that the buoyancy component of the balloon velocity was larger than the downward velocity component of the wind. Tests of the method with measurements of wind velocity in a street canyon of downtown Chicago showed that the method yielded flow patterns quite similar to photographic results of flow visualization of phisical simulations by other investigators. However, no direct measurements of wind velocity were available for quantitative comparison.

  1. Wind Turbine Loads Induced by Terrain and Wakes: An Experimental Study through Vibration Analysis and Computational Fluid Dynamics

    Directory of Open Access Journals (Sweden)

    Francesco Castellani

    2017-11-01

    Full Text Available A wind turbine is a very well-known archetype of energy conversion system working at non-stationary regimes. Despite this, a deep mechanical comprehension of wind turbines operating in complicated conditions is still challenging, especially as regards the analysis of experimental data. In particular, wind turbines in complex terrain represent a very valuable testing ground because of the possible combination of wake effects among nearby turbines and flow accelerations caused by the terrain morphology. For these reasons, in this work, a cluster of four full-scale wind turbines from a very complex site is studied. The object of investigation is vibrations, at the level of the structure (tower and drive-train. Data collected by the on-board condition monitoring system are analyzed and interpreted in light of the knowledge of wind conditions and operating parameters collected by the Supervisory Control And Data Acquisition (SCADA. A free flow Computational Fluid Dynamics (CFD simulation is also performed, and it allows one to better interpret the vibration analysis. The main outcome is the interpretation of how wakes and flow turbulences appear in the vibration signals, both at the structural level and at the drive-train level. Therefore, this wind to gear approach builds a connection between flow phenomena and mechanical phenomena in the form of vibrations, representing a precious tool for assessing loads in different working conditions.

  2. Does aquatic exercise reduce hip and knee joint loading? In vivo load measurements with instrumented implants.

    Science.gov (United States)

    Kutzner, Ines; Richter, Anja; Gordt, Katharina; Dymke, Jörn; Damm, Philipp; Duda, Georg N; Günzl, Reiner; Bergmann, Georg

    2017-01-01

    Aquatic exercises are widely used for rehabilitation or preventive therapies in order to enable mobilization and muscle strengthening while minimizing joint loading of the lower limb. The load reducing effect of water due to buoyancy is a main advantage compared to exercises on land. However, also drag forces have to be considered that act opposite to the relative motion of the body segments and require higher muscle activity. Due to these opposing effects on joint loading, the load-reducing effect during aquatic exercises remains unknown. The aim of this study was to quantify the joint loads during various aquatic exercises and to determine the load reducing effect of water. Instrumented knee and hip implants with telemetric data transfer were used to measure the resultant joint contact forces in 12 elderly subjects (6x hip, 6x knee) in vivo. Different dynamic, weight-bearing and non-weight-bearing activities were performed by the subjects on land and in chest-high water. Non-weight-bearing hip and knee flexion/extension was performed at different velocities and with additional Aquafins. Joint forces during aquatic exercises ranged between 32 and 396% body weight (BW). Highest forces occurred during dynamic activities, followed by weight-bearing and slow non-weight-bearing activities. Compared to the same activities on land, joint forces were reduced by 36-55% in water with absolute reductions being greater than 100%BW during weight-bearing and dynamic activities. During non-weight-bearing activities, high movement velocities and additional Aquafins increased the joint forces by up to 59% and resulted in joint forces of up to 301%BW. This study confirms the load reducing effect of water during weight-bearing and dynamic exercises. Nevertheless, high drag forces result in increased joint contact forces and indicate greater muscle activity. By the choice of activity, movement velocity and additional resistive devices joint forces can be modulated individually in the

  3. Applicability of hydraulic dynamometer for measuring load mass on forwarders

    Directory of Open Access Journals (Sweden)

    Pandur Zdravko

    2015-01-01

    Full Text Available In the last few years, with the start of wood biomass production from wood residues, the need for determining the quantity of extracted wood residuals on a landing site has appeared. The beginning of intensive usage of wood residues for wood biomass starts in lowland forest where all wood residues are extracted with forwarders. There are several ways to determine load mass on a forwarder, first and probably most accurate is the use of load cells which are installed between forwarder undercarriage and loading space. In Croatia, as far as it is known, there is no forwarder with such equipment, although manufacturers offer the installation of such equipment when buying a new forwarder. The second option is using a portable measuring platform (axle scale which was already used for research of axle loads of trucks and forwarders. The data obtained with the measuring platform are very accurate, while its deficiency is relatively great mass, large dimensions and high price. The third option is determining mass by using hydraulic dynamometer which is installed on crane between the rotator and the telescopic boom. The production and installation of such a system is very simple, and with the price it can easily compete with previously described measuring systems. The main deficiency of this system is its unsatisfying accuracy. The results of assortment mass measuring with hydraulic dynamometer installed on a hydraulic crane and discussion on factors influencing obtained results will be presented in this paper.

  4. Load and Flicker Mitigation of Grid-Connected Wind Turbines with DFIG

    DEFF Research Database (Denmark)

    Zhang, Yunqian

    , such as loss of a small amount of wind energy at low wind speeds and high demand of the pitch actuation system (PAS), are also pointed out. Taking advantage of the large inertia of the wind turbine rotor, a simple and effective method of Flicker mitigation by generator torque control of DFIG is proposed......, such that the power oscillation is stored as the kinetic energy of the wind turbine. Based on the flickermeter model, flicker level of the DFIG based wind turbine is investigated during continuous operation....

  5. Advanced Load Alleviation for Wind Turbines using Adaptive Trailing Edge Flaps: Sensoring and Control

    DEFF Research Database (Denmark)

    Andersen, Peter Bjørn

    The purpose of wind turbines and their predecessors the windmill, is to convert the energy in the wind to usable energy forms. Whereas windmills of the past focused on the conversion of wind power to torque for grinding, pumping and winching, modern wind turbines convert the wind energy into elec...... control. Active control is often considered costly but if the lifespan of the components can be increased it could be justifiable. This thesis covers various aspects of ‘smart control’ such as control theory, sensoring, optimization, experiments and numerical modeling....

  6. Summary Report: The Shadow effect of large wind farms: measurements, data analysis and modelling

    DEFF Research Database (Denmark)

    Frandsen, Sten Tronæs; Barthelmie, Rebecca Jane; Rathmann, Ole

    It was the goal of the project – by means of data from the demonstration wind farms Horns Rev and Nysted, analyses of these data and modelling – to facilitate prediction of the power losses from a wind farm should a new wind farm be built upwind relative to the prevailing wind direction......: • Measurements were carried out at the Nysted and Horns Rev demonstration wind farms for several years. Doing so included design, installation and operation of the measurement system • A data base was built from the incoming data. The data have been organized to facilitate verification of the models developed....... Or conversely, predict with adequate accuracy the production of a new wind farm built downwind of an existing wind farm. The project should be seen in the perspective of the two existing demonstration wind farms that extend 5-10 km in each direction. In order to e.g. use the existing electrical infrastructure...

  7. Remotely measuring the wind using turbine-mounted lidars: Application to power performance testing

    DEFF Research Database (Denmark)

    Borraccino, Antoine

    of the wind field reconstruction methods. Two wind models were developed in this thesis. The first one employs lidar measurement at a single distance – but several heights –, accounts for shear through a power law profile, and estimates hub height wind speed, direction and the shear exponent. The second model...... combines the wind model with a simple one-dimensional induction model. The lidar inputs were line-of-sight velocity measurements taken at multiple distances close to the rotor, from 0.5 to 1.25 rotor diameters. Using the combined wind-induction model, hub height free stream wind characteristics...... uncertainties were also quantified. Further, the annual energy production (AEP) was computed for a range of annual mean wind speeds. At 8ms−1, the lidar-estimated AEP was within 1% to the one obtained with the cup anemometer. The combined wind-induction reconstruction technique represents a paradigm shift...

  8. Quantification of rain gauge measurement undercatch and wind speed correction

    Science.gov (United States)

    Pollock, Michael; Quinn, Paul; Dutton, Mark; Wilkinson, Mark

    2014-05-01

    Hydrological processes are adversely affected by systematic rain gauge inaccuracy due to wind induced undercatching. The implications of this are discussed and addressed. Despite evidence of the undercatch problem being cited in the past and the difficulty in solving such a complex problem; it has become an inconvenient truth to hydrologists that major inaccuracies in rainfall measurement exist. A two year long experiment using new equipment and improved data logging and telemetery techniques enriches this formative work to redress the wilful neglect with which accurate rainfall measurement has been treated in recent decades. Results from this work suggest that the annual systematic undercatch can be in the order of 20 percent in the UK. During specific periods (measured at high temporal resolution), this can rise to as high as 50 percent for a single wind impacted event. As one organisation, responsible for the environment in the UK, moves towards using fewer instruments (15 percent fewer in the next year), it is scarcely possible to overstate the importance in solving this problem. It had been hoped that new equipment, such as acoustic distrometer and weighing gauge technologies, would be able to reduce the magnitude of the bias. However, through data gathered in the 2 year experiment and through secondary sources from the 1970s and 1980s, it is demonstrated that this is not the case and that the same problems with undercatching remain now as they did then. We further postulate that wider, denser networks of inexpensive telemetered equipment are now possible but they must still address the undercatch issue. There is little merit in pointing out an age old problem if no solution is put forward to fix it. The aforementioned experiment has furnished new ideas and further work has been commissioned to address this problem. This will be achieved via the medium of a Knowledge Transfer Partnership between Newcastle University and an innovative equipment manufacturer

  9. Advanced load alleviation for wind turbines using adaptive trailing edge flaps: Sensoring and control

    Energy Technology Data Exchange (ETDEWEB)

    Andersen, Peter Bjoern

    2010-02-15

    The purpose of wind turbines and their predecessors the windmill, is to convert the energy in the wind to usable energy forms. Whereas windmills of the past focused on the conversion of wind power to torque for grinding, pumping and winching, modern wind turbines convert the wind energy into electric power. They do so through incorporation of generators, which convert mechanical torque into electricity. Wind turbines are designed to keep the overall cost per produced Kilo Watt hour as low as possible. One way of improving the performance and lifetime of the wind turbine is through active flow control. Active control is often considered costly but if the lifespan of the components can be increased it could be justifiable. This thesis covers various aspects of 'smart control' such as control theory, sensoring, optimization, experiments and numerical modeling. (author)

  10. What's Powering Wind? Measuring the Environmental Benefits of Wind Generated Electricity

    OpenAIRE

    Cullen, Joseph

    2008-01-01

    Production subsidies for renewable energy have experienced intermittent support from the federal government. One reason for less than united support arises from uncertainty over the environmental impact of projects implemented because of such subsidies. Wind energy in particular has taken advantage of federal subsidies, but what has been the environmental impact? Taking investment in wind capacity as given, I am able to identify the short run substitution patterns between wind power and conve...

  11. Wind-stilling in the light of wind speed measurements: the Czech experience

    Czech Academy of Sciences Publication Activity Database

    Brázdil, Rudolf; Valík, A.; Zahradníček, Pavel; Řezníčková, Ladislava; Tolasz, R.; Možný, M.

    2018-01-01

    Roč. 74 (2018), s. 131-143 ISSN 0936-577X R&D Projects: GA MŠk(CZ) LO1415; GA ČR(CZ) GA15-11805S Institutional support: RVO:86652079 Keywords : universal anemograph * vaisala wind-speed sensors * wind speed * homogenisation * wind stilling * Czech Republic Subject RIV: DG - Athmosphere Sciences, Meteorology OBOR OECD: Meteorology and atmospheric sciences Impact factor: 1.578, year: 2016

  12. Implementation and Assessment of a Decentralized Load Frequency Control: Application to Power Systems with High Wind Energy Penetration

    Directory of Open Access Journals (Sweden)

    Irene Muñoz-Benavente

    2017-01-01

    Full Text Available This paper describes and assesses a decentralized solution based on a wireless sensor-actuator network to provide primary frequency control from demand response in power systems with high wind energy penetration and, subsequently, with relevant frequency excursions. The proposed system is able to modify the electrical power demand of a variety of thermostatically-controlled loads, maintaining minimum comfort levels and minimizing both infrastructure requirements and primary reserves from the supply side. This low-cost hardware solution avoids any additional wiring, extending the wireless sensor-actuator network technology towards small customers, which account for over a 30% share of the current power demand. Frequency excursions are collected by each individual load controller, considering not only the magnitude of the frequency deviation, but also their evolution over time. Based on these time-frequency excursion characteristics, controllers are capable of modifying the power consumption of thermostatically-controlled loads by switching them off and on, thus contributing to primary frequency control in power systems with higher generation unit oscillations as a consequence of relevant wind power integration. Field tests have been carried out in a laboratory environment to assess the load controller performance, as well as to evaluate the electrical and thermal response of individual loads under frequency deviations. These frequency deviations are estimated from power systems with a high penetration of wind energy, which are more sensitive to frequency oscillations and where demand response can significantly contribute to mitigate these frequency excursions. The results, also included in the paper, evaluate the suitability of the proposed load controllers and their suitability to decrease frequency excursions from the demand side in a decentralized manner.

  13. Rate of rotation measurement using back-EMFS associated with windings of a brushless DC motor

    Science.gov (United States)

    Howard, David E. (Inventor)

    2000-01-01

    A system and method are provided for measuring rate of rotation. A brushless DC motor is rotated and produces a back electromagnetic force (emf) on each winding thereof. Each winding's back-emf is integrated and multiplied by the back-emf associated with an adjacent winding. The multiplied outputs associated with each winding are combined to produce a directionally sensitive DC output proportional only to the rate of rotation of the motor's shaft.

  14. Comparison of Angle of Attack Measurements for Wind Tunnel Testing

    Science.gov (United States)

    Jones, Thomas, W.; Hoppe, John C.

    2001-01-01

    Two optical systems capable of measuring model attitude and deformation were compared to inertial devices employed to acquire wind tunnel model angle of attack measurements during the sting mounted full span 30% geometric scale flexible configuration of the Northrop Grumman Unmanned Combat Air Vehicle (UCAV) installed in the NASA Langley Transonic Dynamics Tunnel (TDT). The overall purpose of the test at TDT was to evaluate smart materials and structures adaptive wing technology. The optical techniques that were compared to inertial devices employed to measure angle of attack for this test were: (1) an Optotrak (registered) system, an optical system consisting of two sensors, each containing a pair of orthogonally oriented linear arrays to compute spatial positions of a set of active markers; and (2) Video Model Deformation (VMD) system, providing a single view of passive targets using a constrained photogrammetric solution whose primary function was to measure wing and control surface deformations. The Optotrak system was installed for this test for the first time at TDT in order to assess the usefulness of the system for future static and dynamic deformation measurements.

  15. Dynamic Reliability Analysis of Gear Transmission System of Wind Turbine in Consideration of Randomness of Loadings and Parameters

    Directory of Open Access Journals (Sweden)

    Lei Wang

    2014-01-01

    Full Text Available A dynamic model of gear transmission system of wind turbine is built with consideration of randomness of loads and parameters. The dynamic response of the system is obtained using the theory of random sampling and the Runge-Kutta method. According to rain flow counting principle, the dynamic meshing forces are converted into a series of luffing fatigue load spectra. The amplitude and frequency of the equivalent stress are obtained using equivalent method of Geber quadratic curve. Moreover, the dynamic reliability model of components and system is built according to the theory of probability of cumulative fatigue damage. The system reliability with the random variation of parameters is calculated and the influence of random parameters on dynamic reliability of components is analyzed. In the end, the results of the proposed method are compared with that of Monte Carlo method. This paper can be instrumental in the design of wind turbine gear transmission system with more advantageous dynamic reliability.

  16. Load estimation from planar PIV measurement in vortex dominated flows

    Science.gov (United States)

    McClure, Jeffrey; Yarusevych, Serhiy

    2017-11-01

    Control volume-based loading estimates are employed on experimental and synthetic numerical planar Particle Image Velocimetry (PIV) data of a stationary cylinder and a cylinder undergoing one degree-of-freedom (1DOF) Vortex Induced Vibration (VIV). The results reveal the necessity of including out of plane terms, identified from a general formulation of the control volume momentum balance, when evaluating loads from planar measurements in three-dimensional flows. Reynolds stresses from out of plane fluctuations are shown to be significant for both instantaneous and mean force estimates when the control volume encompasses vortex dominated regions. For planar measurement, invoking a divergence-free assumption allows accurate estimation of half the identified terms. Towards evaluating the fidelity of PIV-based loading estimates for obtaining the forcing function unobtrusively in VIV experiments, the accuracy of the control volume-based loading methodology is evaluated using the numerical data with synthetically generated experimental PIV error, and a comparison is made between experimental PIV-based estimates and simultaneous force balance measurements.

  17. Coordination Between Wind Power, Hydro Storage Facility and Conventional Generating Units According to the Annual Growth Load

    Directory of Open Access Journals (Sweden)

    Shahrokh Shojaeean

    2013-04-01

    Full Text Available Considering the growing trend of the consumption of the electric power and the global tendency to substitute new renewable sources of energy, this paper proposes a Monte Carlo based method to determine an optimal level of this change. Considering the limitation of the wind farms in continuous supply of electric power, hydrostatic power storage facilities are used beside wind farms so that the electric power could be stored and fed in a continuous flow into power systems. Due to the gradual exclusion of conventional generators and 5 percent annual load increments, LOLE index was used in order to calculate the amount of the wind power and the capacity of the necessary power storage facility. To this end, LOLE index was calculated for the first year as the reference index for the estimation of the amount of wind power and the capacity of the storage facility in consequent years. For the upcoming years, calculations have been made to account for the gradual exclusion of conventional generators in proportion to load increments. The proposed method has been implemented and simulated on IEEE-RTS test system.

  18. Quantitative analysis of impact measurements using dynamic load cells

    Directory of Open Access Journals (Sweden)

    Brent J. Maranzano

    2016-03-01

    Full Text Available A mathematical model is used to estimate material properties from a short duration transient impact force measured by dropping spheres onto rectangular coupons fixed to a dynamic load cell. The contact stress between the dynamic load cell surface and the projectile are modeled using Hertzian contact mechanics. Due to the short impact time relative to the load cell dynamics, an additional Kelvin–Voigt element is included in the model to account for the finite response time of the piezoelectric crystal. Calculations with and without the Kelvin–Voigt element are compared to experimental data collected from combinations of polymeric spheres and polymeric and metallic surfaces. The results illustrate that the inclusion of the Kelvin–Voigt element qualitatively captures the post impact resonance and non-linear behavior of the load cell signal and quantitatively improves the estimation of the Young's elastic modulus and Poisson's ratio. Mathematically, the additional KV element couples one additional differential equation to the Hertzian spring-dashpot equation. The model can be numerically integrated in seconds using standard numerical techniques allowing for its use as a rapid technique for the estimation of material properties. Keywords: Young's modulus, Poisson's ratio, Dynamic load cell

  19. Development of an instrument for measuring different types of cognitive load

    NARCIS (Netherlands)

    Leppink, J.; Paas, F.; Vleuten, C.P.M. van der; Gog, T.A.J.M. van; Merrienboer, J.J. Van

    2013-01-01

    According to cognitive load theory, instructions can impose three types of cognitive load on the learner: intrinsic load, extraneous load, and germane load. Proper measurement of the different types of cognitive load can help us understand why the effectiveness and efficiency of learning

  20. Parametric Study of Tuned Mass Dampers for Long Span Transmission Tower-Line System under Wind Loads

    Directory of Open Access Journals (Sweden)

    Li Tian

    2016-01-01

    Full Text Available A parametric study of tuned mass dampers for a long span transmission tower-line system under wind loads is done in this paper. A three-dimensional finite element model of transmission tower-line system is established by SAP2000 software to numerically verify the effectiveness of the tuned mass damper device. The wind load time history is simulated based on Kaimal spectrum by the harmony superposition method. The equations of motion of a system with tuned mass damper under wind load excitation are proposed, and the schematic of tuned mass damper is introduced. The effects of mass ratio, frequency ratio, damping ratio, the change of the sag of transmission line, and the robustness of TMD are investigated, respectively. Results show that (1 the change of mass ratio has a greater effect on the vibration reduction ratio than those of frequency ratio and damping ratio, and the best vibration reduction ratio of TMD is not the frequency ratio of 1; (2 the sag-span ratio has an insignificant effect on the vibration reduction ratio of transmission tower when the change of sag-span ratio is not large; and (3 the effect of ice should be considered when the robustness study of TMD is carried out.