18,606 research outputs found
Experimental study of yawed inflow around wind turbine rotor
No full textIn this article, we present an experimental study in a wind tunnel of a three-bladed, Rutland 503 model, horizontal axis yawed wind turbine. Power measurement and an exploration downstream wake of the turbine using particle image velocimetry measurements are performed. The variation of power coefficient as a function of rotational velocity is presented for different yaw angles. The results show a loss of power from the wind turbine when the yaw angle increases. The velocity field of the downstream wake of the rotor is presented in an azimuth plane, which passes through the symmetry axis of the rotor. The instantaneous velocity field is measured and recorded to allow for obtaining the averaged velocity field. The results also show variations in the wake downstream due to decelerating flow caused by the yawed turbine rotor. Analysis of this data shows that the active control of yaw angles could be an advantage to preserve the power from the wind turbine and that details near rotor wake are important for wake theories and topredict the performance of wind turbines as well
Determination of wind turbine far wake using actuator disk
No full textThe growth in size of wind turbines over the last years is significant. The rotor diameter becomes somehow comparable to atmospheric boundary layer at the land surface. In this case the assumption of uniform velocity of upcoming wind cannot be valid. The aim of this paper is to create a simplified model of wind turbine rotor which can represent the aerodynamic inter-action of atmospheric boundary layer with a horizontal axis wind turbine. Such model will be also useful for the study of optimal placement of wind turbines in a wind farm when a large number of calculations is needed and when the time required for full CFD calculations be-comes prohibitive. In this study we adopt actuator disk model which takes in account with sufficient precision the influence of blade geometry on wind turbine aerodynamic performance. The proposed actuator disk model is tested in the case of horizontal axis wind turbine using wall-modelled large eddy simulation. The obtained results of aerodynamic performance and wake show the rapidity of calculation and the reliability of proposed approach
Computational Study of Stalled Wind Turbine Rotor Performance
No full textSimplification of the aerodynamic control of large horizontal
axis wind turbines (HAWTs) has been identified as an important step
towards improved reliability and reduced cost. At present the
majority of large HMrrs use active control to regulate power and
loads. A simpler strategy is to use the inherent stalling of the
rotor blades in high winds to limit power and loads.
Unfortunately the performance of stall regulated HAWTs 1S poorly
understood; current performance models often fail to correctly
predict peak power levels. The benefits of passive control of power
and loads cannot be utilised because of this uncertainty.
This study examines the possible reasons for the poor performance
of current prediction techniques 1n high winds with the objective of
fonmulating a new model.
The available experimental evidence suggests that rotor stall is
caused by turbulent separation at the rear of the blade aerofoil,
growing in extent from the root in increasing wind. This 'picture'
of the stalling HAW! rotor forms the basis of the approach. The new
model consists of a prescribed vortex wake, first order panel method
(extended to represent the viscous region of trailing edge
separation) and three dimensional integral boundary layer directly
coupled in an iterative scheme.
A sensitivity study of rotor
indicates that the most important
performance to wake geometry
factor is the rate at which the
wake is convected downstream. However, it is found that stalled
power levels are insensitive to wake geometry; the study concludes
that the problem of poor prediction of high wind performance lies on
the rotor blades.
Before using the complete code to calculate the performance of a
rotor it 1S first tuned for the aerofoils used on the blade.
Aerofoil perfonmance characteristics measured in a wind tunnel are
synthesised by the model. Ideally these characteristics should
include measured pressure profiles below and above stall.
Validation of the complete code against detailed measurements
taken under controlled conditions on a three metre diameter machine
indicates significant differences in the perfonmance of aerofoil
sections on a wind turbine blade when compared to the same section
when tested in a wind tunnel. Derived lift coefficients show a
reduced lift curve slope and more gentle delayed stall.
Similar results are found when the code is applied to two Danish
stall regulated machines. These two machines although having very
similar geometries and using the same family of aerofoils do however
show differences in derived post stall drag. This is thought to be
due to the different thickness distributions of the two rotors.
The validation and applications of the new model show that it can
accurately predict the peak power level of stall regulated machines
Characterisation of large changes in wind power for the day-ahead market using a fuzzy logic approach
No full textWind power has become one of the renewable resources with a major growth in the electricity market. However, due to its inherent variability, forecasting techniques are necessary for the optimum scheduling of the electric grid, specially during ramp events. These large changes in wind power may not be captured by wind power point forecasts even with very high resolution Numerical Weather Prediction (NWP) models. In this paper, a fuzzy approach for wind power ramp characterisation is presented. The main benefit of this technique is that it avoids the binary definition of ramp event, allowing to identify changes in power out- put that can potentially turn into ramp events when the total percentage of change to be considered a ramp event is not met. To study the application of this technique, wind power forecasts were obtained and their corresponding error estimated using Genetic Programming (GP) and Quantile Regression Forests. The error distributions were incorporated into the characterisation process, which according to the results, improve significantly the ramp capture. Results are presented using colour maps, which provide a useful way to interpret the characteristics of the ramp events
Impacto da estabilidade atmosférica no desempenho de um pequeno aerogerador em terreno complexo
No full textDissertação (mestrado) - Universidade Federal de Santa Catarina, Centro Tecnológico, Programa de Pós-Graduação em Engenharia Mecânica, Florianópolis, 2014Quando instalados em zonas urbanas, pequenos aerogeradores estão sujeitos a altos níveis de turbulência atmosférica, influenciados pela elevada complexidade do terreno. O presente trabalho avalia o impacto da estabilidade atmosférica no desempenho de um pequeno aerogerador em um terreno complexo e propõe uma análise de performance com a utilização da estabilidade atmosférica e intensidade de turbulência como parâmetros de análise. O comprimento de Obukhov é escolhido para representar a estabilidade, por ser capaz de quantificar os mecanismos de transporte turbulento de quantidade de movimento e calor ao longo da porção superficial da camada limite atmosférica. A bancada experimental utilizada como estudo de caso é composta de um pequeno aerogerador de 2,1kW de potência e uma torre anemométrica instrumentada com um anemômetro sônico 3D, ambos instalados a 18m ao lado de um prédio no campus da Universidade. Dois anos de dados anemométricos apontam para uma intensidade de turbulência média igual a 32% no local. A base de dados selecionada possui 4287h de dados brutos ao longo de seis meses. A curva de potência medida de acordo com as recomendações da IEC mostrou um desempenho 14% acima da curva do fabricante, mas com queda na potência próximo à velocidade nominal. A correlação entre maior geração em baixas velocidades e altos níveis de turbulência concorda com estudos prévios. Três classes de estabilidade atmosférica foram definidas de acordo com o comprimento de Obukhov. Curvas de potência para cada classe foram então comparadas com a média. Desvios de até 51% foram observados entre diferentes classes de estabilidade. Para velocidades acima de 8 m/s, a condição instável foi predominante e evidenciou a tendência de queda na potência, onde o parâmetro intensidade de turbulência não conseguiu resultados consistentes. Os resultados mostram a consistência da metodologia proposta para análise de desempenho de pequenos aerogeradores com base em parâmetros físicos e estatísticos. Por fim, a construção de superfícies de potência em função da estabilidade e turbulência demonstram bons resultados na descrição da potência extraída próxima à velocidade nominal.Abstract: Small wind turbines in urban environment conditions are usually under high levels of ambient turbulence, influenced by the terrain complexity at the site. The present work evaluates the impact of atmospheric stability on a small wind turbine in a complex terrain, proposing a performance assessment that uses both atmospheric stability and turbulence intensity as criteria. The Obukhov length is chosen as a classification parameter, which is able to quantify the turbulent transport of momentum and heat over the lower portion of the atmospheric boundary layer. The experimental setup used a 2.1 kW wind turbine along with a met mast instrumented with a 3D sonic anemometer, both installed at 19 m next to a two-story building with few nearby obstacles on the university campus. Two years of 10 min wind data show an average turbulence intensity of 32% on site. Therefore, an urban zone environment could be studied with 20 Hz turbulent flux measurements. The selected dataset consists of 4287h of raw data covering a six-month period. Measured power curve following IEC recommendations shows an average performance 14% above the expected manufacturer curve, but with decreasing power output close to the rated wind speed. Values relating power collection increase at low wind speeds with high turbulence levels concur with previous studies. Atmospheric stability was divided into three classes, based on Obukhov length. Stability-dependent power curves were compared with the measured average. Deviations up to 51% in power output were observed between different stability conditions. Above 8 m/s, unstable conditions were predominant and evidenced the declining power tendency, where turbulence intensity was unable to give a consistent outcome. Results reported herein validate a suitable approach for small wind turbines assessment using both physical and statistical parameters as classification criteria. Power surfaces also shows why the proposed assessment better explains the turbine behavior close to rated conditions
Efeito da esteira de aerogeradores sobre a produção do parque eólico de beberibe
No full textDissertação (mestrado) - Universidade Federal de Santa Catarina, Centro Tecnológico, Programa de Pós-Graduação em Engenharia Mecânica, Florianópolis, 2015.A capacidade instalada da energia eólica, no Brasil e no mundo, vem aumentando a cada ano e, com isso, são necessários procedimentos de verificação da produção de energia de parques eólicos, com o intuito de quantificar se o que foi proposto está sendo entregue e como está o rendimento do parque. Por causa do alto custo de investimento, nem sempre é possível se ter uma torre anemométrica nos parques e, por isso, realizar a medição de acordo com a norma IEC 61400-12-1. Como alternativa para esta situação e pelo fato do parque eólico de Beberibe possuir apenas uma torre para 32 aerogeradores, o presente trabalho avalia a aplicação da função de transferência da velocidade do vento da nacele no cálculo da produção anual de energia e do fator de capacidade do parque. Também foram investigados quais os fatores, como velocidade e direção do vento, que mais influenciam na geração do parque. Os dados reais de velocidade e produção foram comparados com os calculados por meio do software WAsP. Por meio dos dados reais e das simulações, observou-se que alguns aerogeradores do parque possuíam produção abaixo da média deste, devido ao fato de trabalharem na esteira de aerogeradores vizinhos. Então, foram estudados e simulados alguns novos layouts e novos aerogradores para o parque de Beberibe, com o objetivo de se obter uma produção anual igual ou superior à atual com menor número de aerogeradores, através de uma melhora na disposição dos mesmos. Comisso, conseguiu-se reduzir o percentual de perdas por esteiras simuladas de 7,1% para 1,8% com uma das sugestões de layout. Abstract : The installed capacity of wind power in Brazil and in the world is increasingevery year and, procedures are necessary for verifying the energy production of wind farms. Because of the high cost of investment, is not always possible to have a meteorological mast in the wind farm and, therefore, to measure according to IEC 61400-12-1 standards. Beberibewind farm has only one mast for 32 wind turbines, so this work evaluatesthe application of a nacelle wind speed transfer function in thecalculation of annual energy production and the capacity factor of windfarm. The influence of wind speed and direction in power productionwas explored. Wind speed and power production data were comparedwith WAsP software outputs. Some wind turbines had low productionwhen compared with others, because of the wakes of neighboring windturbines. New layouts were explored to obtain the same or higher annualenergy production a lower number of turbines. The percentage of wake effects was reduced from 7.1% to 1.8% using new layout
Estudo do potencial eólico e previsão de ventos para geração de eletricidade em Santa Catarina
No full textDissertação (mestrado) - Universidade Federal de Santa Catarina, Centro Tecnológico. Programa de Pós-graduação em Engenharia MecânicaO trabalho é dividido em duas partes, na primeira delas o objetivo é a análise das principais características dos ventos em seis localidades do Estado de Santa Catarina visando a determinar o potencial eólico para geração de eletricidade, enquanto na segunda parte se faz um estudo sobre previsão de velocidade de ventos e geração eólica com base em dados de velocidade de vento gerados pelo modelo meteorológico de meso-escala Eta, do CPTEC / INPE. A primeira parte do trabalho refere-se ao tratamento estatístico dos dados de velocidade de vento, através da distribuição de Weibull, medidos nas estações anemométricas da CELESC (Centrais Elétricas de Santa Catarina S.A.). São determinadas as velocidades médias, a regularidade, a direção preferencial dos ventos, assim como o fator de capacidade do local e a quantidade esperada de energia a ser gerada. Os dados de potência gerada pelos aerogeradores em operação, no Estado, foram comparados aos valores estimados através dos cálculos com as velocidades medidas em campo. Na segunda parte do estudo, os dados previstos pelo modelo Eta do CPTEC / INPE, serviram de base para o treinamento de redes neurais, a partir da comparação com os dados de campo da CELESC, possibilitando uma avaliação da capacidade de previsão de velocidade de vento e de potência para um horizonte de 6h. A questão da previsão de geração elétrica por fonte eólica tornar-se-á de grande importância à medida que aumente a sua participação no balanço energético do país. Os resultados mostram que a técnica de previsão por meio de redes neurais é adequada, apesar de ainda apresentar as limitações decorrentes do escasso banco de dados de velocidade e direção do vento. O estudo sobre o potencial eólico de Santa Catarina indica a existência de localidades com características de ventos adequadas à geração. Dentre as regiões analisadas, destacam-se Laguna e Urubici, que apresentaram valores de fator de capacidade, FC, de 0,40 e 0,34, respectivamente, com velocidades médias anuais em torno de 8 m/s, apesar do baixo valor do fator de forma, k, em torno de 1,8, e Água Doce, com valores de FC em torno de 0,24, velocidade média em torno de 6 m/s e k de 2,4, apresentando resultados satisfatórios para geração de eletricidade. Ainda, nas demais localidades, estimativas feitas com auxílio do programa WAsP mostram que todas apresentam regiões com valores de FC maiores ou iguais a 0,30. A metodologia desenvolvida neste trabalho, embora se restrinja a uma análise de caso para Santa Catarina, poderá ser estendida a todo o país. This study is divided in two parts, in the first one the objective is the analysis of the main wind characteristics for in six places in the State of Santa Catarina aiming to determine the wind power for energy generation, in the second one, a study about wind speed and wind power forecast is made based on CPTEC / INPE Eta mesoscale meteorological model wind speed data. The first part of this study refers to a statistical treatment of wind speed data collected by CELESC, using the Weibull Distribution. The average speeds, regularity, and the main wind direction are determined, as well as capacity factor, FC, of the locations and the estimated power generation potential. In this study, the power generation data collected from the operating wind turbines are also analyzed. These data are compared with the results calculated from the measured wind speeds. In the second part of the study, the predicted data from Eta model, served as a basis for the training of artificial neural networks, through comparison with the measured CELESC data. Their capacity to forecast power generation and wind speed within 6h is evaluated. The wind power forecast will be more important with the growth of the electricity generation by wind power in Brazil. The results show that techniques of forecast by means of neural networks are feasible, although more in-depth studies are limited by the scarse availability of wind speed and direction data. The study about wind potential in the State of Santa Catarina shows that there are areas with wind characteristics for energy generation. Based on the results of this work, the best places in Santa Catarina is Laguna and Urubici with 0.40 and 0.34 for FC values, respectively, and wind velocity near to 8 m/s, despite the low value of Weibull shape factor, k, near to 1.8, and Água Doce with FC values near to 0.24, 6 m/s wind velocity and k factor near to 2.4 show adequate results for electricity generation. In the other places, estimates with WAsP aid show that, there are areas with FC greater than 0.30 in all analyzed places. The method developed in this study will be able to apply in other regions of the country, in spite of being a study perform in the State of Santa Catarina
Modelling and control of a variable-speed switched reluctance generator based wind turbine
No full textThis paper studies the system modelling and control aspects of switched reluctance generator (SRG) based variable speed wind turbines. A control system is implemented to provide proper operation of the SRG as well as power tracking capabilities for varying wind speeds. The control system for the grid side inverter that will allow the SRG to properly generate power to the system is also presented. Studies are presented of both the SRG and inverter control systems capabilities during a balanced three-phase fault. The paper will demonstrate that the SRG based wind turbine presents a feasible variable wind speed solution with good fault response capabilities
Wind power in the UK : a guide to the key issues surrounding onshore wind power development in the UK
No full textThis report is summarised in the Welsh language in 'Ynni gwynt : ateb eich cwestiynau'.This report is summarised in 'Wind power : your questions answered'.This report aims to help policy-makers and planners balance genuine local concerns with wider environmental and social needs, thereby allowing the benefits of renewable energy to be realised through careful design and consultation.Publisher PDFUpdated version. Previous version published May 2005
Estudos de Aspectos de Engenharia para Implantação de Torres Eólicas
No full textTCC (graduação) - Universidade Federal de Santa Catarina. Centro Tecnológico. Engenharia Civil.O potencial eólico da região sul do Brasil passa a ser explorado para geração de eletricidade. O crescimento da demanda por outras fontes de energia justifica os grandes investimentos na construção de parques eólicos. Essas grandes estruturas necessitam de alicerces que as sustentem, portanto soluções específicas de fundações devem ser projetadas. Existem peculiaridades desde o estudo de viabilidade, passando pelas sondagens e execução de estacas, com o intuito de garantir a eficiência da estrutura durante seu período de utilização. Torres eólicas podem ser posicionadas em área continental, onshore, ou no oceano próximas à costa, offshore, e a fundação dessas torres continentais pode ser profunda ou rasa, contudo projetos usuais no sul do País adotam a primeira como solução. A construção de cada base de aerogerador necessita aspectos logísticos de acesso ao canteiro de obras e, em muitos casos, estradas de acesso precisam ser construídas e devidamente compactadas para passagem de materiais e equipamentos. A locação das estacas em planta e a conexão com o bloco de fundação devem seguir determinadas especificações. Nesse contexto, alguns fenômenos, como a cicatrização de estacas, podem prejudicar, ou até beneficiar, o comportamento da estrutura solo-fundação. Portanto, o solo e suas propriedades são relevantes e determinantes para a escolha do tipo, dimensões e quantidades de estacas por base. Alguns dos carregamentos que atuam nos elementos de fundação são cíclicos, devido a incidência de ventos, ou ondas, na torre. Dessa forma, a verificação quanto à fadiga, torna-se de extrema importância na etapa de projeto. Reaterro devidamente compactado sobre o bloco de fundação se faz necessário para suportar as cargas do guindaste e dos elementos da torre armazenados ao lado de sua base. Com isso, o equipamento é capaz de içar as peças e montar a torre eólica por completo. Um exemplo de execução de toda a fundação de um aerogerador ilustra e apresenta todo esse processo.The potential of wind energy on the south region of Brazil begins to be explored for electricity production from wind turbines. The increase on the demand for other types of energy source justify the huge investments on the construction of wind farms. These big structures need foundations which can support them, then specific solutions must be designed. There are peculiarities since the process of viability studies, on the underground investigations and pile driving, until the efficiency of the hole structure during the use period. Wind towers can be settled onshore or offshore. The foundation of the onshore towers can be deep or slab, however usually the projects on the south of the country use the first option as solution. The construction of each wind turbine base need logistic planning for the access of the construction site. In many situations roads must be built and properly compacted for the passage of materials and equipments. The position of the pile on plant and its connection with the block must follow certain specifications, so the structure lifetime can be guaranteed. On this context, some phenomenons, as the pile setup, can affect or benefit the behaviour of the soil-foundation structure. That is one of the reasons that the soil and its properties are relevant to indicate the type, dimensions and number of piles per base. Some of the loads which affect the foundation elements are cyclic, due to the wind force, or waves, on the tower. Therefore, the fatigue verification becomes extremely important on the design step. Landfilling must be properly done over the foundation block to support the loads from the cranes and parts of the tower, which are placed by the side of the tower base. Then, the equipment will be capable of lifting the pieces and assembling all the parts of the wind turbine. An example of a wind tower foundation construction ilustrate all the process
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