Showing papers in "Wind Engineering in 2005"
TL;DR: In this article, the authors focus on the generation of electricity from clean and renewable sources, and show that wind energy has become the world's fastest growing energy source, and that renewable energy is the most promising energy source.
Abstract: As environmental concerns have focussed attention on the generation of electricity from clean and renewable sources, wind energy has become the world's fastest growing energy source. The authors dr ...
2,878 citations
TL;DR: A standardized protocol for the evaluation of short-term windpower prediction systems is proposed and a number of reference prediction models are described, and their use for performance comparison is analysed.
Abstract: Short-term wind power prediction is a primary requirement for efficient large-scale integration of wind generation in power systems and electricity markets. The choice of an appropriate prediction model among the numerous available models is not trivial, and has to be based on an objective evaluation of model performance.This paper proposes a standardized protocol for the evaluation of short-term wind-power prediction systems. A number of reference prediction models are also described, and their use for performance comparison is analysed. The use of the protocol is demonstrated, using results from both on-shore and offshore wind farms. The work was developed in the frame of the Anemos project (EU R&D project) where the protocol has been used to evaluate more than 10 prediction systems.
342 citations
TL;DR: In this paper, the aerodynamic characteristics of the Riso-B1-18 airfoil equipped with variable trailing edge geometry as produced by a hinged flap were investigated in both steady and unsteady flow conditions.
Abstract: A comprehensive computational study, in both steady and unsteady flow conditions, has been carried out to investigate the aerodynamic characteristics of the Riso-B1-18 airfoil equipped with variable trailing edge geometry as produced by a hinged flap. The function of such flaps should be to decrease fatigue-inducing oscillations on the blades. The computations were conducted using a 2D incompressible RANS solver with a k-w turbulence model under the assumption of a fully developed turbulent flow. The investigations were conducted at a Reynolds number of Re = 1.6 · 106. Calculations conducted on the baseline airfoil showed excellent agreement with measurements on the same airfoil with the same specified conditions. Furthermore, a more widespread comparison with an advanced potential theory code is presented. The influence of various key parameters, such as flap shape, flap size and oscillating frequencies, was investigated so that an optimum design can be suggested for application with wind turbine blades....
103 citations
TL;DR: The first person to use a wind powered machine to generate electricity, which operated for the first time during the winter of 1887, was Professor James Blyth, a Scottish academic of Anderson's College, Glasgow as mentioned in this paper.
Abstract: The American, Charles Brush is often credited with being the first person to use a wind powered machine to generate electricity, which operated for the first time during the winter of 1887. However, earlier in July 1887, Professor James Blyth, a Scottish academic of Anderson's College, Glasgow (which later became Strathclyde University) was undertaking very similar experiments to Brush, which culminated in a UK patent in 1891. Likewise the Dane, Poul La Cour, is known to have constructed relatively advanced wind turbines throughout the 1890s, which were also used to generate electricity which was then used to produce hydrogen.This paper investigates Professor Blyth's life, seeking to understand his motivation to generate electricity from the wind and his association with contemporaries, including Lord Kelvin. The paper argues that it was Blyth and not Brush, who was the first to produce wind-powered electricity.
85 citations
TL;DR: In this article, a two-dimensional theoretical study of the aeroelastic behavior of an airfoil has been performed, whose geometry can be altered using a rear-mounted flap.
Abstract: A two-dimensional theoretical study of the aeroelastic behaviour of an airfoil has been performed, whose geometry can be altered using a rear-mounted flap. This device is governed by a controller, whose objective is to reduce the airfoil displacements and, therefore, the stresses present in a real blade. The aerodynamic problem was solved numerically by a panel method using the potential theory, suitable for modelling attached flows. It is therefore mostly applicable for Pitch Regulated Variable Speed (PRVS) 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 airfoil geometry is an effective means of reducing the vibration magnitudes of an airfoil that represents a section of a wind turbine blade, when subject to stochastic wind signals. The results of this inv...
82 citations
TL;DR: In this paper, the authors pointed out that the spatial distance between the costs incurred and the benefits derived from wind power is a major barrier for turbine proposals in Sweden, and suggested that the perceived need for wind power, level of participation, individual considerations of visual impact and the amount to which the local community benefits determine the realisation of turbine proposals.
Abstract: Wind power is growing in Sweden, but the high-level of opposition to turbine proposals has meant that many proposals are never realised. This opposition in a country that has a measured 74% support for wind power leads to questions being raised as to what is causing this opposition. Many have suggested that it is due to prevalent NIMBY attitudes; this, however, is only one factor affecting the public acceptance of turbines. The over-riding factor is the spatial distance between the costs incurred and the benefits derived from wind power. Perceived need for wind power, level of participation, individual considerations of visual impact and the amount to which the local community benefits determine the realisation of turbine proposals.
78 citations
TL;DR: In this paper, the authors describe a lack of confidence and knowledge among farmers and grass-roots activists concerning wind power in the UK and highlight the need for greater resources on dissemination of expertise about community wind power and support for feasibility/planning costs of some flagship schemes.
Abstract: Commercially sized community wind power schemes, whether owned by local farmers or by co-operatives, are very acceptable under the UK Renewables Obligation for a wide range of sites in the UK. Perceived ‘barriers' to such schemes include a lack of confidence and knowledge among farmers and grass-roots activists concerning wind power. By contrast knowledge, expertise and enthusiasm is spread much more widely in countries such as Germany, The Netherlands and Denmark. Nevertheless, an increasing number of community-based wind power initiatives are emerging in the UK. Greater resources on dissemination of expertise about community wind power and support for feasibility/planning costs of some flagship schemes need to be deployed by governmental and non-governmental organisations.
57 citations
TL;DR: In this paper, a feasibility study for a wind farm with fixed speed induction generators and having a STATCOM, combined with Mechanically Switched Capacitors, for reactive power control and fault recovery is presented.
Abstract: This paper describes a feasibility study for a wind farm with Fixed Speed Induction Generators and having a STATCOM, combined with Mechanically Switched Capacitors, for reactive power control and fault recovery. The turbine blade and generator inertia, coupled with a shaft of finite stiffness, are modelled to represent torsional oscillation. This is important to represent the dynamic behaviour of the system adequately.Dynamic simulations show that fault ride-though capability of a wind farm can be met by using a STATCOM, and switching in shunt capacitors, when the overspeed protection is set at 1.1 pu. However, the wind turbine must be designed to cope with the mechanical stress resulting from a fault in the AC system with a large magnitude of voltage dip. Successful fault recovery is demonstrated for symmetrical and asymmetrical faults. The control strategy proposed here can be adopted for different grid code requirements and various wind farms.
38 citations
TL;DR: In this article, a comparative study of different methods used to estimate Weibull parameters of a wind regime is presented, and the results obtained as a plot of error versus wind speed are similar in all the five methods, yet the method of standard deviation gives the best results.
Abstract: The Weibull probability function is a widely accepted tool to model wind regimes. This paper presents a comparative study of different methods used to estimate Weibull parameters of a wind regime. Five different methods are described and used for the estimation. Time series data of wind speed over a whole year for two sites have been used for the study. The results obtained as a plot of error versus wind speed are similar in all the five methods, yet the method of standard deviation gives the best results.
33 citations
TL;DR: In this article, the initial development of the design and operation of modern vertical and horizontal axis wind turbines, with the aim of comparing the development of two types, is reviewed, focusing on the Savonius rotor.
Abstract: This paper reviews the initial development of the design and operation of modern vertical and horizontal axis wind turbines, with the aim of comparing the development of the two types. Application in developing countries concentrates on the Savonius rotor. The review aims to record important early developments, including the years following the first oil crisis of 1973.
32 citations
TL;DR: In this paper, a parametrisation of the turbulence intensity at given sites, relevant for the calculation of fatigue loading of wind turbines, is presented, based on wind speed measurements extracted from the database on wind characteristics.
Abstract: 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.
TL;DR: In this paper, the effect of torsional vibrations on the damping of a direct-driven generator with a generator damping system was studied. But the generator dampness was not investigated for a directly-driven multipole synchronous generator with FEM simulations.
Abstract: Torsional vibrations may be a critical issue for those vertical axis wind turbines having long drive trains as compared with standard horizontal axis wind turbines. Such vibrations are studied by simulation for two different types of generators used with a vertical axis wind turbine, namely a conventional induction generator with a gearbox and a directly-driven multipole synchronous generator. The synchronous generator has been designed with FEM simulations. The didactic calculations show from first principles that a directly-driven generator is to be preferred when torsional vibrations are considered, since the eigenfrequency of the fundamental vibration is greater for a directly driven generator than otherwise. Thus, the risk of resonance is reduced in a stiff assembly. The generator damping of the vibrations for the simulated, directly-driven synchronous generator is also studied.
TL;DR: In this article, the authors examined the flow velocity characters around lift-based straight-wing vertical-axis wind turbines (SW-VAWT) by numerical simulation and confirmed the precision of the prediction technique.
Abstract: This research examines the flow velocity characters around lift-based straight-wing vertical-axis wind turbines (SW-VAWT) by numerical simulation. The precision of the prediction technique was confirmed. Furthermore, we estimate the flow behaviour during the wind turbine rotation by using this numerical simulation technique, and evaluate the flow around the SW-VAWT. This paper presents an outline of the work and gives the results of the calculations.
TL;DR: In this article, the authors present a method of identifying and estimating gross errors for linear dynamic systems, in particular the doubly-fed induction generator, which is applied to wind power.
Abstract: This paper presents a method of identifying and estimating gross errors for linear dynamic systems. The method is applied to wind power, in particular the doubly-fed induction generator. Measurements have errors, but it is possible to reduce the effect of such errors on control by exploiting relationships between the different variables of the system. Such analysis is called 'data validation'. Data validation uses a mathematical model, based on equations, to simulate the real dynamic system. An analysis of systematic errors is made using a measurement test. The method has the potential to support the on-line multi-parameter data analysis, and hence maintenance, of complex systems, such as wind turbines.
TL;DR: The paper concludes with the experiences gained in the connection of wind generation projects to theGB Transmission System both before and after the approval of new proposals to the GB Grid Code.
Abstract: This paper presents the development of Grid Code requirements for new and renewable forms of generation in Great Britain (GB). After briefly describing the background to the GB Transmission System and the volume of renewable generation which is anticipated to connect in the future, the paper discusses the Grid Code and Grid Code change process. In particular, the paper discusses the interfaces with key stakeholders, the technical issues considered in connecting other generation technologies to the Transmission network and the rationale for the final Grid Code requirements. The technical issues discussed include fault ride through, frequency range, frequency response, power/frequency characteristic, reactive range, voltage control and power quality. The paper concludes with the experiences gained in the connection of wind generation projects to the GB Transmission System both before and after the approval of new proposals to the GB Grid Code.
TL;DR: In this article, the authors compare the costs of using concrete foundations against steel monopile foundations for offshore wind turbines, and argue that concrete foundations will be cheaper than steel monopiles.
Abstract: This paper compares the costs of using concrete foundations against steel monopile foundations for offshore wind turbines, and argues that concrete foundations will be cheaper. Most offshore windfarms have steel monopile foundations, but in Denmark concrete gravity foundations have been used with success. Two projects have tendered for steel monopiles and for concrete foundations and have implemented the concrete foundations that proved cheaper. No project has tendered for both foundation concepts and chosen steel monopiles.Nysted Offshore Windfarm with concrete foundations has the cheapest foundations of any offshore windfarm so far. A conceptual foundation study carried out for the London Array West Offshore Windfarm indicates that the same method and very low-cost foundations as for Nysted can be used. Optimised design of light-weight concrete constructions is the key to low-cost installation. Cheap manufacture can be carried out near the site or at even lower cost in Eastern Europa from where it can b...
TL;DR: In this paper, the authors address the dynamic modelling of large (MW) capacity Doubly Fed Induction Generators (DFIG) wind turbines using Pscad/Emtdc and Matlab/Simulink.
Abstract: This paper addresses the dynamic modelling of large (MW) capacity Doubly Fed Induction Generators (DFIG) wind turbines using Pscad/Emtdc™ and Matlab/Simulink™. Suitable speed and reactive power controllers are implemented and described. Application studies are conducted to observe the performance of the DFIG during power system disturbances such as three-phase faults developing in different points of the network. These studies are used to determine the DFIG's fault current contribution and power converter rating required for fault ride-through capability and protection requirements. Simulations results are presented and discussed using typical turbine and network data for wind farm facilities.
TL;DR: In this article, the authors developed a method of transferring aerodynamic and inertial loads from the aeroelastic analysis output to the finite element (FE) model, and case studies were undertaken using an FE model of a 34m blade.
Abstract: The structural design of wind turbine blades is a rapidly evolving technology. Finite element (FE) modelling is used extensively by structural designers to assess the behaviour of wind turbine blades under operational and extreme load conditions. This paper develops a method of transferring aerodynamic and inertial loads from the aeroelastic analysis output to the FE model. Once a procedure is developed and verified, case studies are undertaken using an FE model of a 34m blade. Loads are applied using the newly developed method and various FE analysis results compared to the same blade analysed under more traditional load application techniques. The case study clearly demonstrates that the method of applying loads can influence some types of analysis results significantly.
TL;DR: In this paper, the extent to which a wind energy site is affected by a coastal cliff is presented by studying numerically a neutral Atmospheric Boundary Layer (ABL) flow using an RNG κ-ϵ model and different geometries.
Abstract: The extent to which a wind energy site is affected by a coastal cliff is presented by studying numerically a neutral Atmospheric Boundary Layer (ABL) flow using an RNG κ-ϵ model and different geometries. Initially, the classical flow over a forward-facing step is modelled, followed by the modelling of a neutral ABL over a rough plane in two and three dimensions with various types of ground conditions. Finally, the two and three-dimensional flows over a forward-facing step, representing a coastal cliff, in a neutral ABL were modelled and applied to the Atlantic Wind Test Site (AWTS), site composed of a wind turbine testing facility and a 13 MW wind farm, in the province of Prince Edward Island, Canada. After assessing that the model can predict classical flows and ABL with relatively good accuracy and robustness, the results show that the extent of the effect of a coastal cliff on the flow above the AWTS is limited to a distance of 5h downstream of the (height h = 10 m) cliff. Based on the sitting of the e...
TL;DR: In this article, the simulation model of a controller that enables an active-stall wind turbine to ride through transient faults is described and the turbine shall be able to sustain operation in case of such faults.
Abstract: This paper describes the simulation model of a controller that enables an active-stall wind turbine to ride through transient faults. The simulated wind turbine is connected to a simple model of a power system. Certain fault scenarios are specified and the turbine shall be able to sustain operation in case of such faults. The design of the controller is described and its performance assessed by simulations. The control strategies are explained and the behaviour of the turbine discussed.
TL;DR: In this article, the authors proposed a converter-connected asynchronous generator for wind turbines with pitch-controlled and variable-speed, which can support the grid voltage at short-circuit faults and improve the fault-ride-through capability of the wind turbines.
Abstract: Wind turbines equipped with full-load converter-connected asynchronous generators are a known concept. These have rating up to hundreds of kW and are a feasible concept for MW class wind turbines and may have advantages when compared to conventional wind turbines with directly connected generators. The concept requires the use of full-scale frequency converters, but the mechanical gearbox is smaller than in conventional wind turbines of the same rating. Application of smaller gearbox may reduce the no-load losses in the wind turbines, which is why such wind turbines with converter connected generators may start operation at a smaller wind speed. Wind turbines equipped with such converted connected asynchronous generators are pitch-controlled and variable-speed. This allows better performance and control. The converter control may be applied to support the grid voltage at short-circuit faults and to improve the fault-ride-through capability of the wind turbines, which makes the concepts relevant for large ...
TL;DR: In this paper, the authors presented the first wind resource assessment for offshore-wind energy off the mainland coasts of Saudi Arabia, despite the onshore wind resource being known, and utilized wind speed data from, in effect, an offshore meteorological station to study the annual and seasonal variation of wind speed, wind speed frequency distribution, energy yield and consequent opportunity for reduction in green house gases (GHG) emissions.
Abstract: This paper, to the best of author's knowledge, presents the first wind resource assessment for offshore-wind energy off the mainland coasts of Saudi Arabia, despite the onshore wind resource being known. The study utilized wind speed data from, in effect, an offshore meteorological station to study the annual and seasonal variation of wind speed, wind speed frequency distribution, energy yield and consequent opportunity for reduction in green house gases (GHG) emissions. These results were compared with contemporaneous data from a mainland location ∼ 10 km inland at the same longitude Energy yields were calculated using HOMER and RetScreen models. The annual mean wind measured at Abu Ali Island, the offshore location, was 5.43 m/s. This is larger than the 4.9 m/s measured over the same period at Abu Kharuf, the nearby inland location. Larger wind speeds were found in winter months than in summer months at both locations. At Abu Ali Island, the power of the wind could be extracted for 75% of the time at hu...
TL;DR: In this article, the effect of different design parameters, namely rotor shape, overlap between rotor blades, and overlap between the rotor blades was studied in a wind tunnel for an optimum configuration of a Savonius rotor wind turbine.
Abstract: Many tests have been conducted on models in a wind tunnel for an optimum configuration of a Savonius rotor wind turbine. Three types of Savonius rotor have been used (a simple Savonius rotor of mild steel, an overlapped Savonius rotor of mild steel and one overlapped Savonius rotors of aluminium). The effect of different design parameters, namely rotor shape, overlap between rotor blades was studied. The results have corroborated some of the original findings of Savonius.
TL;DR: In the oil and gas industry, the foundations of offshore platforms have, for decades, used the grouted technique and this technology has now been transferred into the offshore wind turbine industry as mentioned in this paper.
Abstract: In the oil and gas industry, the foundations of offshore platforms have, for decades, used the grouted technique. This technology has now been transferred into the offshore wind turbine industry. This paper gives details of the use of the technology in some of the first offshore windfarms in Europe and considers future design possibilities.
TL;DR: In this paper, a very detailed 2D-solid finite element model is developed representing the load-carrying box girder of a wind turbine blade, and the overall cross-sectional behavior is analyzed for a simple compressive line load.
Abstract: A very detailed 2D-solid finite element model is developed representing the load-carrying box girder of a wind turbine blade. Using typical geometrical values for the girder dimensions and public available material data, the overall cross-sectional behaviour is analysed for a simple compressive line load. The results are compared with result from similar shell models, which typically are used for practical design. Usually, good agreement between the shell models and the detailed 2D-solid model is found for the deflections, strains and stresses in regions with loads from pure bending. However, large differences can exist in regions where the loading is dominated by shear. It is found that geometrical non-linearity starts to become important when deflections are of the same order as the laminate thickness.
TL;DR: In this paper, a statistical analysis gave the annual average wind speed as 3.80 m/s, in the range of 3.0 to 5.0m/s for 89% of the time.
Abstract: The wind speed at Inshas, Egypt in 2003 is considered as a case study. A statistical analysis gave the annual average wind speed as 3.80 m/s, in the range of 3.0 to 5.0 m/s for 89% of the time. Comparison among Weibull, Rayleigh, and actual data distributions of wind speed and wind power indicates that the Weibull distribution is the better fit. The mean monthly wind speed had its maximum in December and its minimum in February. The maximum wind energy potential was 63.6 W/m2 in December and, the annual mean value was 34.4 W/m2.
TL;DR: In this article, an application of the WAsP program in complex, forested terrain in the central North Island of New Zealand is described, where a potential wind farm located along a ridge in the forest estate, the size of forest clearings and the growth of trees over the wind farm lifetime are considered in view of expected annual energy yields.
Abstract: This paper describes an application of the WAsP program in complex, forested terrain in the central North Island of New Zealand. The work was carried out as part of a research project that investigated the viability of developing a wind farm for the Kinleith pulp and paper mill. Subsequent to an outline of the limitations of the WAsP program, the study area, its representation in WAsP through digital terrain data, and the wind data collection at three sites in the Kinleith Forest are described. A comparison of WAsP predictions with field measurements is found to qualitatively confirm the RIX concept. For the study area an adjusted relationship between site ruggedness and prediction error is derived. Studying a potential wind farm located along a ridgeline in the forest estate, the size of forest clearings and the growth of trees over the wind farm lifetime are considered in view of expected annual energy yields.
TL;DR: In this paper, the long-term wind resource at a potential windfarm site may be estimated by correlating short-term on-site wind measurements with data from a regional meteorological station.
Abstract: The long-term wind resource at a potential windfarm site may be estimated by correlating short-term on-site wind measurements with data from a regional meteorological station. Three correlation methods developed at Airtricity are described, and their accuracy assessed.
TL;DR: In this article, a model based on 2D sound ray theory for aerodynamic noise propagation from wind turbine rotating blades is introduced, which includes attenuation factors from geometric spreading, sound directivity of source, air absorption, ground deflection and reflection, as well as effects from temperature and airflow.
Abstract: A model based on 2-D sound ray theory for aerodynamic noise propagation from wind turbine rotating blades is introduced. The model includes attenuation factors from geometric spreading, sound directivity of source, air absorption, ground deflection and reflection, as well as effects from temperature and airflow. At a given receiver point, the sound pressure is corrected by taking into account these propagation effects. As an overall assumption, the noise field generated by the wind turbine is simplified as a point source placed at the hub height of the wind turbine. This assumtion is reasonable, for the receiver is located in the far field, at distances from the wind turbine that are much longer than the diameter of the rotor.
TL;DR: In this paper, the authors present results of voltage stability investigations carried out on a large power network model, where they make a distinction between local wind turbines and those in a large wind farm subject to the Grid Specifications of the transmission system operator.
Abstract: The article presents results of voltage stability investigations carried out on a large power network model. Presumably, around 50 per cent of electricity consumption is covered by wind turbines and by local combined heat and power (CHP) units. In investigations, a distinction is made between local wind turbines and those in a large wind farm subject to the Grid Specifications of the transmission system operator (Eltra, 2000). The main concerns of maintaining power system operation are (i) a risk of significant power loss due to tripping of local units and (ii) a risk of overvoltage at the periphery of the power network. This is contrary to previous investigations predicting that the main concern should be a risk of voltage collapse (Bruntt et al., 1999). As demonstrated, voltage collapse does not occur, because local wind turbines will trip when abnormal grid operation is indicated. This "eliminates" the problem of voltage-collapse. On the other hand, this introduces new problems with regard to (i) estab...