On a self-start Darrieus wind turbine: blade design and field tests

This paper is about a design of an urban area Darrieus VAWT, having self-start ability due to an innovative profile design named EN0005, avoiding the need of extra components or external electricity feed-in. An approach is presented to study the ability of a blade profile to offer self-start ability. Methodologies applied for the blade body and for profile development are reported. Field tests and main conclusions are presented to persuade for the arrangement of this design. (C) 2015 Elsevier Ltd. All rights reserved.

Methodology for wind turbine blade geometry optimization

Nowadays, the upwind three bladed horizontal axis wind turbine is the leading player on the market. It has been found to be the best industrial compromise in the range of different turbine constructions. The current wind industry innovation is conducted in the development of individual turbine components. The blade constitutes 20-25% of the overall turbine budget. Its optimal operation in particular local economic and wind conditions is worth investigating. The blade geometry, namely the chord, twist and airfoil type distributions along the span, responds to the output measures of the blade performance. Therefore, the optimal wind blade geometry can improve the overall turbine performance. The objectives of the dissertation are focused on the development of a methodology and specific tool for the investigation of possible existing wind blade geometry adjustments. The novelty of the methodology presented in the thesis is the multiobjective perspective on wind blade geometry optimization, particularly taking simultaneously into account the local wind conditions and the issue of aerodynamic noise emissions. The presented optimization objective approach has not been investigated previously for the implementation in wind blade design. The possibilities to use different theories for the analysis and search procedures are investigated and sufficient arguments derived for the usage of proposed theories. The tool is used for the test optimization of a particular wind turbine blade. The sensitivity analysis shows the dependence of the outputs on the provided inputs, as well as its relative and absolute divergences and instabilities. The pros and cons of the proposed technique are seen from the practical implementation, which is documented in the results, analysis and conclusion sections.

Wind turbine blade pitch control system

The present invention provides an improvement for a wind turbine (20) having at least one blade (21) mounted on a hub (22) for controlled rotation about a blade axis (yb-yb) to vary the pitch of the blade relative to an airstream. The hub is mounted on a nacelle (23) for rotation about a hub axis (xh-xh). The wind turbine includes a main pitch control system for selectively controlling the pitch of the blade, and/or a safety pitch control system for overriding the main blade pitch control system and for causing the blade to move toward a feathered position in the event of an overspeed or fault condition. The improvement includes: an energy storage device (26) mounted on the nacelle and associated with the blade; a pitch-axis controller (25) mounted on the nacelle and associated with the blade and with the energy storage device; an electro-mechanical actuator (28) mounted on the hub and associated with the blade; and at least one slip ring (29) operatively arranged to transmit power and/or data signals between the pitch-axis controller and the electro-mechanical actuator; whereby the mass on the rotating hub may be reduced.

A nonlinear and non-ideal wind generator supporting structure

We present a simple mathematical model of a wind turbine supporting tower. Here, the wind excitation is considered to be a non-ideal power source. In such a consideration, there is interaction between the energy supply and the motion of the supporting structure. If power is not enough, the rotation of the generator may get stuck at a resonance frequency of the structure. This is a manifestation of the so-called Sommerfeld Effect. In this model, at first, only two degrees of freedom are considered, the horizontal motion of the upper tip of the tower, in the transverse direction to the wind, and the generator rotation. Next, we add another degree of freedom, the motion of a free rolling mass inside a chamber. Its impact with the walls of the chamber provides control of both the amplitude of the tower vibration and the width of the band of frequencies in which the Sommerfeld effect occur. Some numerical simulations are performed using the equations of motion of the models obtained via a Lagrangian approach.

FEM and experimental analysis of a wind turbine blade

This paperwork compares the a numerical validation of the finite element model (FEM) with respect the experimental tests of a new generation wind turbine blade designed by TPI Composites Inc. called BSDS (Blade System Design Study). The research is focused on the analysis by finite element (FE) of the BSDS blade and its comparison with respect the experimental data from static and dynamic investigations. The goal of the research is to create a general procedure which is based on a finite element model and will be used to create an accurate digital copy for any kind of blade. The blade prototype was created in SolidWorks and the blade of Sandia National Laboratories Blade System Design Study was accurately reproduced. At a later stage the SolidWorks model was imported in Ansys Mechanical APDL where the shell geometry was created and modal, static and fatigue analysis were carried out. The outcomes of the FEM analysis were compared with the real test on the BSDS blade at Clarkson University laboratory carried out by a new procedures called Blade Test Facility that includes different methods for both the static and dynamic test of the wind turbine blade. The outcomes from the FEM analysis reproduce the real behavior of the blade subjected to static loads in a very satisfying way. A most detailed study about the material properties could improve the accuracy of the analysis.

COMPUTATIONAL ANALYSIS OF THE AEROELASTIC DYNAMICS OF A WIND TURBINE BLADE WITH VARIABLE-SPEED STALL CONTROL

The accuracy of simulating the aerodynamics and structural properties of the blades is crucial in the wind-turbine technology. Hence the models used to implement these features need to be very precise and their level of detailing needs to be high. With the variety of blade designs being developed the models should be versatile enough to adapt to the changes required by every design. We are going to implement a combination of numerical models which are associated with the structural and the aerodynamic part of the simulation using the computational power of a parallel HPC cluster. The structural part models the heterogeneous internal structure of the beam based on a novel implementation of the Generalized Timoshenko Beam Model Technique.. Using this technique the 3-D structure of the blade is reduced into a 1-D beam which is asymptotically equivalent. This reduces the computational cost of the model without compromising its accuracy. This structural model interacts with the Flow model which is a modified version of the Blade Element Momentum Theory. The modified version of the BEM accounts for the large deflections of the blade and also considers the pre-defined structure of the blade. The coning, sweeping of the blade, tilt of the nacelle and the twist of the sections along the blade length are all computed by the model which aren’t considered in the classical BEM theory. Each of these two models provides feedback to the other and the interactive computations lead to more accurate outputs. We successfully implemented the computational models to analyze and simulate the structural and aerodynamic aspects of the blades. The interactive nature of these models and their ability to recompute data using the feedback from each other makes this code more efficient than the commercial codes available. In this thesis we start off with the verification of these models by testing it on the well-known benchmark blade for the NREL-5MW Reference Wind Turbine, an alternative fixed-speed stall-controlled blade design proposed by Delft University, and a novel alternative design that we proposed for a variable-speed stall-controlled turbine, which offers the potential for more uniform power control and improved annual energy production.. To optimize the power output of the stall-controlled blade we modify the existing designs and study their behavior using the aforementioned aero elastic model.

Development of a grid connected micro wind generator. A practical activity for the course on electric generation with wind energy

This paper describes a practical activity, part of the renewable energy course where the students have to build their own complete wind generation system, including blades, PM-generator, power electronics and control. After connecting the system to the electric grid the system has been tested during real wind scenarios. The paper will describe the electric part of the work surface-mounted permanent magnet machine design criteria as well as the power electronics part for the power control and the grid connection. A Kalman filter is used for the voltage phase estimation and current commands obtained in order to control active and reactive power. The connection to the grid has been done and active and reactive power has been measured in the system.

Improved damage detectability in a wind turbine blade by optimal selection of vibration signal correlation coefficients

Piotr Omenzetter and Simon Hoell’s work within the Lloyd’s Register Foundation Centre for Safety and Reliability Engineering at the University of Aberdeen is supported by Lloyd’s Register Foundation. The Foundation helps to protect life and property by supporting engineering-related education, public engagement and the application of research.

Improved damage detectability in a wind turbine blade by optimal selection of vibration signal correlation coefficients

Piotr Omenzetter and Simon Hoell’s work within the Lloyd’s Register Foundation Centre for Safety and Reliability Engineering at the University of Aberdeen is supported by Lloyd’s Register Foundation. The Foundation helps to protect life and property by supporting engineering-related education, public engagement and the application of research.

Tuulivoimalan lapojen huolto ja tarkastukset

Uusiutuva energia elää voimakasta kasvukautta ja hallituksen tekemien tukipäätösten vuoksi tuulivoimaa tullaan rakentamaan huomattavasti lisää tulevien vuosien aikana. Tuuligeneraattorin siipien huolto- ja tarkastustoiminta on uusi ja kehittyvä toimiala. Tämä diplomityö onkin tehty oppaaksi helpottamaan tuulivoimaa omistavien, rakentavien, tai tuulivoimapuiston perustamista harkitsevien tahojen huoltosuunnitelmien tekemistä varten. Diplomityössä käydään läpi yleisimmät tuulivoimaloiden lapojen vikaantu-miset, sekä työskentelytavat ja käytettävät laitteistot voimaloiden lapojen huoltoja ja tarkastuksia tehtäessä.

Wind turbine operation in cold climate

The goal of the master‘s thesis is to determine and estimate ice accretion influence on the wind turbine blade performance. The thesis describes the technique of ice accretion calculation on the wind turbine blade and determination characteristics of the turbine with ice accreted. The methodology of the classic Blade Element Moment Theory was used. Iced blade experimental data was investigated in order to calculate blade with ice characteristics. The obtained results shows that iced blade power coefficient is lower than clean blade one. The heating system implementation shows that in the particular site in the Lapland region it is efficient.

Low Voltage Ride-through in DFIG Wind Generators by Controlling the Rotor Current without Crowbars

Among all the different types of electric wind generators, those that are based on doubly fed induction generators, or DFIG technology, are the most vulnerable to grid faults such as voltage sags. This paper proposes a new control strategy for this type of wind generator, that allows these devices to withstand the effects of a voltage sag while following the new requirements imposed by grid operators. This new control strategy makes the use of complementary devices such as crowbars unnecessary, as it greatly reduces the value of currents originated by the fault. This ensures less costly designs for the rotor systems as well as a more economic sizing of the necessary power electronics. The strategy described here uses an electric generator model based on space-phasor theory that provides a direct control over the position of the rotor magnetic flux. Controlling the rotor magnetic flux has a direct influence on the rest of the electrical variables enabling the machine to evolve to a desired work point during the transient imposed by the grid disturbance. Simulation studies have been carried out, as well as test bench trials, in order to prove the viability and functionality of the proposed control strategy.

Concepção de uma pequena turbina eólica destinada ao segmento doméstico (simplificação e análise aerodinâmica das pás)

O trabalho que se apresenta incide sobre o estudo aerodinâmico das pás de uma turbina eólica de pequeno porte, com vista à simplificação geométrica, de forma a que estas sejam baratas e de fácil concepção. A teoria da quantidade de movimento do elemento de pá (BEMT), que é o modelo de referência para o projecto e análise aerodinâmica das pás das turbinas eólicas, foi utilizada neste trabalho de forma a projectar e analisar aerodinamicamente as pás da turbina. Sendo assim, desenvolveu-se um programa computacional em MATLAB, denominado de “Turbina”, de forma a implementar a teoria BEM. Introduzindo os dados dos parâmetros de projecto no programa (potência requerida, o número de pás, velocidade do vento, a TSR e o tipo de perfil alar), obtêm-se os parâmetros geométricos das pás (distribuição da corda ao longo da envergadura, o raio da pá e a distribuição da torção da pá), os parâmetros aerodinâmicos e de desempenho. Uma pá ideal foi calculada e de seguida foi modificada de forma a obter-se uma pá simples e menos carregada aerodinamicamente. Introduzidas as modificações na geometria da pá ideal, obtiveram-se duas configurações distintas. Uma configuração linear, onde a distribuição da corda e do ângulo de torção se tornam lineares, e outra configuração bi-linear, onde a distribuição da corda continua linear mas o ângulo de torção se torna bi-linear, isto é, a pá é composta por dois troços onde cada troço apresenta uma distribuição linear do ângulo de torção geométrica. As conclusões demonstram que a configuração bi-linear é uma boa alternativa a configuração ideal, apresentando uma redução do desempenho do rotor de 2.8% para um aumento do raio da pá em 1.41%, para se obter a mesma potência da configuração ideal. A análise aos perfis alares, utilizados neste trabalho, foi efectuada a partir dos programas comerciais ICEM e FLUENT. De forma a automatizar a análise de CFD, três programas foram desenvolvidos utilizando a linguagem de programação “C”. Os programas são denominados de “Malha2D”, “Calcula_Coeficientes” e “Plot_Graficos”. Finalmente, um estudo paramétrico foi feito de forma a avaliar a influências das variáveis de projecto no desempenho geral da turbina.

Tuulivoimalan staattoripakan puristusrakenteen kehittäminen

Diplomityössä tutkittiin voidaanko tuulivoimalan generaattorin staattoripakan puristamisessa hyödyntää komposiittista rakenneratkaisua. Tyypillisesti generaattorissa staattorin teräslevyt puristetaan erilaisilla teräsrakenteilla toisiaan vasten. Tavoitteena oli selvittää, voidaanko puristavan komposiittirakenteen osana hyödyntää liimaliitosta tai laminoitua liitosta. Tarkoitus oli etsiä rakenteeseen soveltuva liima ja liimaliitoksen arvot tai laminoitu rakenne ja sille soveltuvat materiaalit ja suoritustapa. Työssä on perehdytty erilaisiin tuulivoimalatyyppeihin, sekä niissä käytettäviin kesto- ja vierasmagnetoituihin generaattorityyppeihin. Tämän lisäksi on tarkasteltu niissä käytettävien staattorien valmistusvaihtoehtoja ja syitä miksi niissä olevat teräslevyt on puristettava toisiaan vasten. Samalla on luotu katsaus nykyisin käytössä oleviin rakenteisiin, joilla puristus voidaan toteuttaa. Liimauksesta on käsitelty perusteoriaa, sekä seikkoja jotka vaikuttavat liimaliitoksen kestoon. Työssä tutkittavaan liitokseen soveltuvien liimojen ominaisuuksia on käsitelty. Myös laminoituun liitokseen jo aiemmin kovettuneeseen komposiittiin on perehdytty. Tutkittavaan rakenteeseen soveltuvia hartsi- ja lasikuitutyyppejä on esitelty. Komposiittien mekaaniseen liittämiseen on lyhyesti perehdytty. Työssä suoritettiin useita vetokokeita, joilla selvitettiin puristusrakenteen tutkimista varten valmistettujen koekappaleiden suurin vetokuormankesto. Vetokokeiden perusteella voitiin valita soveltuvin rakenne staattorin puristamiseksi.

Sähköverkosta irti olevan pienhybridijärjestelmän toteutus

Lappeen siniset –partiolippukunnalla on käytössään leiripaikka Humaljärvellä, Lappeenrannassa. Leiripaikalla ei ole liityntää sähköverkkoon, joten leiripaikalle on asennettu kaksi erillistä aurinkovoimalla toimivaa sähköjärjestelmää. Leiripaikan sähköistetyt rakennukset ovat pääkämppä ja saunan sekä vanhan kämpän muodostama kokonaisuus. Aurinkopaneeleilla tuotettu sähköenergia varastoidaan akustoihin. Lippukunta on havainnot käytössä, ettei talvella tuotettu aurinkoenergia riitä kattamaan pääkämpän sähkönkulutusta, joten leiripaikalle on päätetty hankkia tuulivoimala lisäämään tuotantoa. Tässä kandidaatin työssä esitellään hybridijärjestelmään kuuluvien aurinko- ja tuulivoiman toimintaperiaatteita sekä näiden komponentteja. Aurinko- ja tuulivoimalla tuotetulle sähköenergialle lasketaan arviot, joita verrataan leiripaikan sähköjärjestelmän arvioituun kulutukseen. Leiripaikalle tulevaa tuuliturbiinia ja sen lataussäädintä testataan laboratoriossa, jotta varmistutaan niiden soveltuvuudesta sekä toimivuudesta kohteeseen. Testausten ja laitteiden datalehtien avulla suunnitellaan leiripaikalle toimiva hybridijärjestelmä, joka kattaa leiripaikan ympärivuotisen sähkönkulutuksen.