Circulation control for the rotors of large horizontal axis wind turbines

Circulation control, augmenting aerofoil lift and reducing drag using air jets is long established but little considered for wind turbine applications. This is a top-level exploration of the basic concept which involves a substantial part of the rotor blade having low solidity, elliptical sections which generate little lift and drag when passive, greatly moderating extreme storm loads when the rotor is idling. The CC rotor can then be expanded in diameter by ~ 30% within the same loading envelop of a standard rotor with gain in energy capture to compensate for added cost in the rotor systems

Auditing the TPACK confidence of Australian pre-service teachers: the TPACK confidence survey (TCS)

This chapter describes the construction and validation of an instrument to measure teachers’ Technological Pedagogical Content Knowledge (TPACK). The TPACK Confidence Survey (TCS) contains scales that measure teachers’ attitudes toward using ICT; confidence to use ICT for teaching and learning tasks (TPACK); competency with ICT; Technology Knowledge (TK); and TPACK Vocational Self-efficacy. The scale measuring TPACK confidence uses the Learning With ICTs: Measuring ICT Use in the Curriculum instrument that has been evaluated and reported previously. This paper proposes that the TCS provides a valid and reliable instrument with which to audit teachers’ TPACK confidence

Top-level rotor optimisations based on actuator disc theory

Ahead of the elaborate rotor optimisation modelling that would support detailed design, it is shown that significant insight and new design directions can be indicated with simple, high-level analyses based on actuator disc theory. The basic equations derived from actuator disc theory for rotor power, axial thrust and out-of-plane bending moment in any given wind condition involve essentially only the rotor radius, R, and the axial induction factor, a. Radius, bending moment or thrust may be constrained or fixed, with quite different rotor optimisations resulting in each case. The case of fixed radius or rotor diameter leads to conventional rotor design and the long-established result that power is maximised with an axial induction factor, a = 1/3. When the out-of-plane bending moment is constrained to a fixed value with axial induction variable in value (but constant radially) and when rotor radius is also variable, an optimum axial induction of 1/5 is determined. This leads to a rotor that is expanded in diameter 11.6 %, gaining 7.6% in power and with thrust reduced by 10 %. This is the low-induction rotor which has been investigated by Chaviaropoulos and Voutsinas (2013). However, with an optimum radially varying distribution of axial induction, the same 7.6% power gain can be obtained with only 6.7% expansion in rotor diameter. When without constraint on bending moment, the thrust is constrained to a fixed value, and the power is maximised as a→0, which for finite power extraction would require R. This result is relevant when secondary rotors are used for power extraction from a primary rotor. To avoid too much loss of the source power available from the primary rotor, the secondary rotors must operate at very low induction factors whilst avoiding too high a tip speed or an excessive rotor diameter. Some general design issues of secondary rotors are explored. It is suggested that they may have the most practical potential for large vertical axis turbines avoiding the severe penalties on drivetrain cost and weight implicit in the usual method of power extraction from a central shaft

Evaluation of fatigue loads of horizontal up-scaled wind turbines

Wind turbines, especially for offshore applications, are continually being up-scaled on the basis that having fewer separate sites per installed MW will reduce balance of plant and O&M costs and hence may reduce cost of energy. Obviously the loads on a wind turbine increase with the size of the machine. However there is presently no generic, systematic study of how fatigue loads vary with wind turbine size. Both extreme and fatigue load evaluation is essential for the design of wind turbines. This paper however has its focus solely on fatigue loads.The aim is to investigate the dependency of fatigue loads (lifetime damage equivalent loads are employed to calculate the fatigue loads) on wind turbine scale and subsequently to develop generic fatigue load trends with scale, ideally in the form of simple power law curves.Seven wind turbine models were created from a reference model (Danish design) based on up-scaling with similarity. Such scaling does not accurately reflect commercial trends but is considered a best starting point to gain fundamental understanding. Fatigue loads in various design load cases (startups, power production, idling, and shutdowns) as specified in IEC standards are simulated and trend lines determined. This work is part of a much larger generic study of all the main influences on wind turbine loads

A systematic hub loads model of a horizontal wind turbine

The wind turbine industry has focused offshore on increasing the capacity of a single unit through up-scaling their machines. There is however a lack of systematic studies on how loads vary due to properties of a wind turbine and scaling of wind turbines. The purpose of this paper is to study how applied blade modifications, with similarities such as mass, stiffness and dimensions, influence blade root moments and lifetime damage equivalent loads (DELs) of the rotor blades. In order to produce fatigue load blade root moment trends based on the applied modifications. It was found that a linear trend of lifetime DELs based on the applied modifications of blades, which have effect on the natural frequency of blade of the original or reference model. As the control system was tuned for the specific frequency of the reference model. The linear trend of lifetime DELs was generated as long as the natural frequency of the reference model was preserved. For larger modifications of the wind turbine the controller would need retuning

Measuring the use of information and communication technologies (ICTs) in the classroom

In 2003, the ICT Curriculum Integration Performance Measurement Instrument was developed from an extensive review of the contemporary international and Australian research pertaining to the definition and measurement of ICT curriculum integration in classrooms (Proctor, Watson, & Finger, 2003). The 45-item instrument that resulted was based on theories and methodologies identified by the literature review. This paper describes psychometric results from a large-scale evaluation of the instrument subsequently conducted, as recommended by Proctor, Watson and Finger (2003). The resultant 20-item, two-factor instrument, now called Learning With ICTs: Measuring ICT Use in the Curriculum is both statistically and theoretically robust. This paper should be read in association with the original paper published in Computers in the Schools (Proctor, Watson & Finger, 2003) that described in detail the theoretical framework underpinning the development of the instrument

ESPecIaL an Embedded Systems Programming Language

Nowadays embedded systems, available at very low cost, are becoming more and more present in many fields such as industry, automotive and education. This master thesis presents a prototype implementation of an embedded systems programming language. This report focuses on a high-level language, specially developed to build embedded applications, based on the dataflow paradigm. Using ready-to-use blocks, the user describes the block diagram of his application, and its corresponding C++ code is generated automatically, for a specific target embedded system. With the help of this prototype Domain Specific Language (DSL), implemented using the Scala programming language, embedded applications can be built with ease. Low-level C/C++ codes are no more necessary. Real-world applications based on the developed Embedded Systems Programming Language are presented at the end of this document

Influence of lift to drag ratio on optimal aerodynamic performance of straight blade vertical axis wind turbines

This paper defines an effective lift to drag for a vertical axis wind turbine design based on averaged torque per cycle. This metric is used to characterise the relationship between overall optimum aerodynamic performance and design parameters. A double multiple streamtube aerodynamic prediction model is employed to demonstrate the effect of lift to drag ratio on optimal power performance for the H-rotor and the V-rotor concept VAWT. A further study looks at the effect of coning angle for the V-rotor

Estimation of the power electronics lifetime for a wind turbine

A comparison has been made of the converter lifetime for a 3MW horizontal axis wind turbine for different wind turbulence levels. Torque and speed of the turbine shaft were used to calculate voltage and current time series that those were used to calculate the junction temperatures of diode and IGBT in the generator-side converter by a thermal-electrical model. A rainflow counting algorithm of the junction temperature in combination with an empirical model of the lifetime estimation has been used to calculate the lifetime of the power electronic module in the turbine. The number of parallel converters for each wind condition to achieve 20 years life time also has been found. it is found greater turbulence levels will lead to less lifetime of the converter in the wind turbine