Effects Of Blade Configuration On Flow Distribution And Power Output Of A Zephyr Vertical Axis Wind Turbine

Worldwide interest in renewable energy systems has increased dramatically, due to environmental concerns like climate change and other factors. Wind power is a major source of sustainable energy, and can be harvested using both horizontal and vertical axis wind turbines. This thesis presents studies of a vertical axis wind turbine performance for applications in urban areas. Numerical simulations with FLUENT software are presented to predict the fluid flow through a novel Zephyr vertical axis wind turbine(VAWT). Simulations of air flow through the turbine rotor were performed to analyze the performance characteristics of the device. Major blade geometries were examined. A multiple reference frame (MRF) model capability of FLUENT was used to express the dimensionless form of power output of the wind turbine as a function of the wind freestream velocity and the rotor's rotational speed. The simulation results exhibit close agreement with a stream-tube momentum model.

This multi-disciplinary book presents the most recent advances in exergy, energy, and environmental issues. Volume 1 focuses on fundamentals in the field and covers current problems, future needs, and prospects in the area of energy and environment from researchers worldwide. Based on selected lectures from the Seventh International Exergy, Energy and Environmental Symposium (IEEES7-2015) and complemented by further invited contributions, this comprehensive set of contributions promote the exchange of new ideas and techniques in energy conversion and conservation in order to exchange best practices in "energetic efficiency". Included are fundamental and historical coverage of the green transportation and sustainable mobility sectors, especially regarding the development of sustainable technologies for thermal comforts and green transportation vehicles. Furthermore, contributions on renewable and sustainable energy sources, strategies for energy production, and the carbon-free society constitute an important part of this book. Exergy for Better Environment and Sustainability, Volume 1 will appeal to researchers, students, and professionals within engineering and the renewable energy fields.

There is a growing global demand for "clean" energy due to an increased mandate to reduce greenhouse gases. Wind energy has established itself as an economically competitive source due to major developments made in the efficiency and reliability of conversion systems. Currently, horizontal axis wind turbines (HAWTs) dominate the wind energy conversion market because of their high efficiency. However, recent advances in vertical axis conversion systems are closing the gap in efficiency. A novel flexible blade concept with the ability to morph and adapt to changing flow conditions was proposed by A. Beyene and T. Ireland, to address part load and performance issues encountered in wind energy conversion systems. The extension of these benefits to a vertical axis wind turbine (VAWT) would make wind technology a more competitive player in the energy market. A straight bladed vertical axis wind turbine (SB-VAWT) rotor was manufactured, to accommodate flexible and rigid blades. The performance and flexible behavior was studied in the department of mechanical engineering's low speed wind tunnel using a test rig that was built for this study. A mathematical model, validated using a high speed camera and finite element analysis, was developed to predict the magnitude and direction of blade morph. The results show that the coefficient of performance (CP) greatly depends on the tip speed ratio (TSR), i.e., the rigid blade has CP of 0.11 for a TSR of 1.6, whereas the morphing blade achieved a CP of 0.06 at a TSR of 1.13. Overall, the modified morphing blade has better performance at low RPMs, but the rigid blade performed better at high RPMs. It was observed that the VAWT equipped with flexible blades self-started in the majority of the experiments. The flexible blade's production of power at relatively low TSRs is a rare occurrence in the field. At high RPM, the centrifugal force overwhelmed the lift force, bending the blade out of phase in an undesired direction increasing drag and therefore reducing the CP. These results suggest that alterations to the current design must be made in order to account for the inertial forces experienced by blades in a vertical axis configuration.

Wind energy is a promising renewable and clean energy source and wind turbines are the common devices to harvest this energy. Vertical-axis wind turbines (VAWTs), one kind of wind turbines, are concerned because of their congenital advantages of easy maintenance. However, one main issue of VAWTs is that the aerodynamic phenomenon of dynamic stall typically occurs under low tip-speed-ratio conditions, which negatively affects their power extraction performance. This study focuses on exploring a better blade design to improve the power coefficient of VAWTs. Two passive flow control designs: 1) serration design, 2) twist design are therefore employed to decrease these negative effects. A conventional H-type VAWT model is used as baseline in this study to compare the power output against the modified VAWT designs. The computational fluid dynamics (CFD) commercial software, STAR CCM+, is used to calculate the power coefficient of VAWTs. The Taguchi method is used as a statistical tool to find the optimum blade design given the prescribed range of design variable values under consideration. Interaction effects between design factors are observed during the data analysis, and the additive model is further developed to adapt this condition. The final analysis illustrates that the optimum model has a power coefficient of 26.47% compared with the baseline model power coefficient of 22.37% (18.3% improvement). It is shown that the twist design can also decrease the vibration of VAWTs. This effect is beneficial to maintain the structural integrity of VAWTs, and improve its lifespan due to lower vibrations. Flow field analysis verifies that the hybrid design inherits the advantages from the serration design and the twist design. The optimum model suppresses the dynamic stall and increases the power output.

Hydrokinetic energy contains the major uncontrolled source of renewable marine energy. The highest level of converter technology readiness offered in the last three decades is TRL8,Äì9, which is related to the first-generation horizontal axis converters. In low-depth calm waters, one of the best options to harvest tidal energy is vertical axis turbines. About 16% of the conceptual designs presented in the last 30¬†years apply this type of converter, which does not have a high level of technological readiness. In this study, a laboratory-designed vertical axis turbine has been introduced in which the effects of the number of blades, the blade profile, and attack angle on the performance of the turbine were analyzed. A 3D incompressible viscous turbulent computational finite volume approach is applied, with the spatial second-order and temporal first-order accuracies. The turbulent model k-œâ SST was used to obtain the flow inside the turbine. Rotors include two, three, and six blades with three different profiles, including NACA2421, NACA16021, and NACA0020. Computational results reveal that the turbine with three blades and an angle of attack of +8 using the NACA2421 profile has a maximum generation capacity of about 4¬†kW, with a strength factor of 0.4 and a power factor of about 20%. The capacity, however, was lower for a higher number of blades.

The exploitation of small horizontal axis wind turbines provides a clean, prospective and viable option for energy supply. Although great progress has been achieved in the wind energy sector, there is still potential space to reduce the cost and improve the performance of small wind turbines. An enhanced understanding of how small wind turbines interact with the wind turns out to be essential. This work investigates the aerodynamic design and analysis of small horizontal axis wind turbine blades via the blade element momentum (BEM) based approach and the computational fluid dynamics (CFD) based approach. From this research, it is possible to draw a series of detailed guidelines on small wind turbine blade design and analysis. The research also provides a platform for further comprehensive study using these two approaches. The wake induction corrections and stall corrections of the BEM method were examined through a case study of the NREL/NASA Phase VI wind turbine. A hybrid stall correction model was proposed to analyse wind turbine power performance. The proposed model shows improvement in power prediction for the validation case, compared with the existing stall correction models. The effects of the key rotor parameters of a small wind turbine as well as the blade chord and twist angle distributions on power performance were investigated through two typical wind turbines, i.e. a fixed-pitch variable-speed (FPVS) wind turbine and a fixed-pitch fixed-speed (FPFS) wind turbine. An engineering blade design and analysis code was developed in MATLAB to accommodate aerodynamic design and analysis of the blades. The linearisation for radial profiles of blade chord and twist angle for the FPFS wind turbine blade design was discussed. Results show that, the proposed linearisation approach leads to reduced manufacturing cost and higher annual energy production (AEP), with minimal effects on the low wind speed performance. Comparative studies of mesh and turbulence models in 2D and 3D CFD modelling were conducted. The CFD predicted lift and drag coefficients of the airfoil S809 were compared with wind tunnel test data and the 3D CFD modelling method of the NREL/NASA Phase VI wind turbine were validated against measurements. Airfoil aerodynamic characterisation and wind turbine power performance as well as 3D flow details were studied. The detailed flow characteristics from the CFD modelling are quantitatively comparable to the measurements, such as blade surface pressure distribution and integrated forces and moments. It is confirmed that the CFD approach is able to provide a more detailed qualitative and quantitative analysis for wind turbine airfoils and rotors. With more advanced turbulence model and more powerful computing capability, it is prospective to improve the BEM method considering 3D flow effects.

Wind turbines will play a crucial role in the global energy transition from a fossil fuel-based world to a renewable-based one. Horizontal-axis wind turbines (HAWTs) currently dominate the commercial sector, although a recent resurgence in interest and research has shown exciting opportunities for the future of vertical-axis wind turbines (VAWTs). Unique cyclical fluid physics results in additional complexity to VAWT blade aerodynamics. Unlike their horizontal-axis counterparts, the rotating blades of a VAWT produce varying torque depending on their location in the circular cycle. The aerodynamic relationship between the incoming wind flow and blade motion is such that the peak power is extracted when the blade and incoming wind are nearly perpendicular to each other during the windward side of the rotor. Recognizing this, the recently conceived dual-vertical-axis wind turbine (D-VAWT) extends a typical VAWT's windward region by having the blades rotate about two vertical axes. Introduced is a new path of purely rectilinear motion connecting the two axes, wherein the blade is designed to achieve optimal aerodynamic efficiency. Initial investigations into the D-VAWT's operation shows promising potential, with power coefficient values in the range of the most efficient VAWTs and even HAWTs. The current study seeks to further improve the performance of the D-VAWT through the incorporation of active blade pitch control throughout the blade path's distinct rotation and rectilinear regions. Computational fluid dynamics (CFD) is used to model a single-blade D-VAWT, and a user-defined method is devised to implement the blade pitch actuation as a function of cycle time location and blade centroid position. Numerical results reveal that strategic blade pitching can indeed increase performance in a specific region of the D-VAWT cycle, however the improvement can create undesired impacts on the flow field in other regions of the rotor. Emphasis is focused on the upstream and downstream flow interaction during active-pitch operation, offering important physical insight to the D-VAWT and VAWTs of similar geometric sizing.

The simulation of flow through vertical axis wind turbine (VAWT) is characterized by unsteady flow where the blade experiences varying angles of attack and Reynolds number as it completes a cycle. Therefore, the lift generated also varies as a function of its rotational position relative to the incoming freestream velocity. In order to improve the performance of these turbines the blade can take advantage of smart materials developed for control surface actuation. The aim of this paper is to investigate the effect of morphing blades on the aerodynamic performance of the turbine blades. The study uses commercial software Ansys Fluent pressure-based solver to investigate the flow past the turbine blades by solving the 2D Unsteady Reynolds-Averaged Navier-Stokes (URANS) equations. In order to simulate the morphing blade for VAWT, a sliding mesh method is used to simulate the VAWT rotation while a user-defined function (UDF) is written for the blade morphing flexure motion. This entails the use of dynamic mesh smoothing to prevent the mesh from having negative cell volumes. Although the dynamic mesh strategy has been successful in preserving the cell quality, it has been shown that the proposed method of simulating the morphing blade on VAWT is inadequate due to unphysical solutions. Finally, the effect of morphing the blade is tested on a static airfoil case instead, where it is shown that stall is alleviated by morphing the blade trailing edge.