Miscellaneous

3D simulation of the vertical axis wind turbines

Michal Petruzela, Vojtech Blazek, May 2017 (Purchase or Member Only)

Computational fluid dynamics (CFD) is appropriate method to analyse aerodynamic flow in wind turbine. This is why we choose this method to compare static torque characteristics of two vertical axis wind turbines (VAWT), one with straight blade and the other one with helical blade. Analyses are realized by use of Ansys CFX software. At first, three-dimensional (3D) simulations of straight blade turbine with different meshes are carried out. To determine how much mesh parameters affect the accuracy of result and computational time. Then we perform 3D simulations of helical blade turbine and compare its results with straight blade one.

A Review of Numerical Modelling of Multi-Scale Wind Turbines and Their Environment

Katrina Calautit, Angelo Aquino, John Kaiser Calautit, Payam Nejat, Fatimeh Jomehzadeh and Ben Richard Hughes, March 2018

Global demand for energy continues to increase rapidly, due to economic and population growth, especially for increasing market economies. These lead to challenges and worries about energy security that can increase as more users need more energy resources. Also, higher consumption of fossil fuels leads to more greenhouse gas emissions, which contribute to global warming. Moreover, there are still more people without access to electricity. Several studies have reported that one of the rapidly developing source of power is wind energy and with declining costs due to technology and manufacturing advancements and concerns over energy security and environmental issues, the trend is predicted to continue. As a result, tools and methods to simulate and optimize wind energy technologies must also continue to advance. This paper reviews the most recently published works in Computational Fluid Dynamic (CFD) simulations of micro to small wind turbines, building integrated with wind turbines, and wind turbines installed in wind farms. In addition, the existing limitations and complications included with the wind energy system modelling were examined and
issues that needs further work are highlighted. This study investigated the current development of CFD modelling of wind energy systems. Studies on aerodynamic interaction among the atmospheric boundary layer or wind farm terrain and the turbine rotor and their wakes were investigated. Furthermore, CFD combined with other tools such as blade element momentum were examined.

CFD simulations of power coefficients for an innovative Darrieus style vertical axis wind turbine with auxiliary straight blades

F Arpino, G Cortellessa, M Dell’Isola, [...], M Rotondi, Journal of Physics Conference Series, November 2017

The increasing price of fossil derivatives, global warming and energy market instabilities, have led to an increasing interest in renewable energy sources such as wind energy. Amongst the different typologies of wind generators, small scale Vertical Axis Wind Turbines (VAWT) present the greatest potential for off grid power generation at low wind speeds. In the present work, Computational Fluid Dynamic (CFD) simulations were performed in order to investigate the performance of an innovative configuration of straight-blades Darrieus-style vertical axis micro wind turbine, specifically developed for small scale energy conversion at low wind speeds. The micro turbine under investigation is composed of three pairs of airfoils, consisting of a main and auxiliary blades with different chord lengths. The simulations were made using the open source finite volume based CFD toolbox OpenFOAM, considering different turbulence models and adopting a moving mesh approach for the turbine rotor. The simulated data were reported in terms of dimensionless power coefficients for dynamic performance analysis. The results from the simulations were compared to the data obtained from experiments on a scaled model of the same VAWT configuration, conducted in a closed circuit open chamber wind tunnel facility available at the Laboratory of Industrial Measurements (LaMI) of the University of Cassino and Lazio Meridionale (UNICLAM). From the proposed analysis, it was observed that the most suitable model for the simulation of the performances of the micro turbine under investigation is the one-equation Spalart-Allmaras, even if under the conditions analysed in the present work and for TSR values higher than 1.1, some discrepancies between numerical and experimental data can be observed.

Engineering and Economic Models of Vertical Axis Wind Turbines

Elhadji Alpha A. Bah, Lakshmi N. Sankar, Jechiel I. Jagoda, December 2017

The interest in sustainable forms of energy is being driven by the anticipated scarcity of traditional fossil fuels over the coming decades. There is also a growing concern about the effects of fossil fuel emissions on human health and the environment. Many sources of renewable energy are being researched and implemented for power production. In particular, wind power generation by vertical-axis wind turbines is one of the option often considered. This option offers a robust design because of the relative simplicity of its technology. However, it also presents challenges that are inherent to its very concept. These systems suffer from dynamic stall, noticeably one of the main causes of the loss of performance. A dual-element concept is proposed as a way of alleviating the losses due to the dynamic stall. An economic analysis is done to establish the economic viability of the model. The Great Coast of Senegal is selected as a site of operation in this study.

This research is based on the Savonius type Vertical Axis Wind Turbines (VAWTs). The VAWT design considered in the present study comprises of 12 rotor blades and 12 stator blades, where the wind speed of 4m/s has been considered. This wind speed is the average annual wind speed in Huddersfield, UK. Erosion is a serious issue in Vertical Axis Wind Turbines that causes roughness on the blades via airborne dirt, debris and insects. Erosion has been shown to degrade the performance characteristics of a VAWT significantly. A number of different strategies have been employed to analyse erosion in VAWTs, and with the advent of powerful and advanced computational methods, it has become possible to investigate erosion at microscopic levels. Hence, this study is based on the predictions from numerical simulations performed using a Computational Fluid Dynamics based solver.

Performance enhancements on vertical axis wind turbines using flow augmentation systems: A review

Kok Hoe Wong, Wen Tong Chong, Nazatul Liana Sukiman, [...], C.-T. Wang, June 2017 (Purchase Only)

There are many advantages of vertical axis wind turbines (VAWTs) compared with horizontal axis wind turbines (HAWTs). Research has shown that VAWTs are more suitable for turbulent wind flow and urban applications. However, the efficiency and low self-start ability of VAWTs are always the main drawbacks especially for the lift-type VAWTs. Unlike HAWTs, the rotor blades for VAWTs do not always provide positive torque during operation. Many innovative designs have been implemented to improve the performance of VAWTs, and this includes different configurations and blade profiles. This paper extensively reviews various flow augmentation systems and attempts to provide information to researchers on current augmentation techniques and other relevant research. The flow augmentation system is able to increase the coefficient of power, CP, hence improving the output power of different types of VAWTs. Some augmentation systems are able to increase the maximum power output by up to 910%. The methods and designs used to increase upwind velocity and to reduce negative torque created on the wind turbine have been discussed in detail. Additionally, the flow augmentation devices that are integrated with building structures are also reported in this paper.

Public receptiveness of vertical axis wind turbines

Iris Hui, Bruce E Cain, John O Dabiri Elsevier Ltd., October 24, 2017

Most of the scholarly focus to date has been on large horizontal axis rather than vertical axis wind turbines. It may be possible to improve the efficiency of vertical axis wind technology by deploying turbines in clusters. There might also be advantages to deploying vertical axis turbines at a smaller scale in urban or suburban areas and in places where the risk of bird damage is highest. Would these features increase public acceptance of new wind turbine installations and possibly open up new areas for wind energy development?

We conducted a public opinion poll in California to examine public receptiveness. We used experimental design to assess the willingness to accept vertical axis turbines in certain urban settings. We find that the visual differences between the vertical and conventional wind turbines did not matter very much in any of the hy- pothetical settings in which we placed them. However, the prospect of killing fewer birds registered strongly with our survey respondents, though it could be outweighed by concern for cost. We also show that certain segments of the population, particularly those who are more educated, may be open to a more extensive de- ployment of vertical axis turbines in urban communities.

Review Paper: Overview of the Vertical Axis Wind Turbines

E A D Kumara, N K Hettiarachchi, K G R M Jayathilake, August 2017

This paper gives an overview of a vertical axis wind turbine. The behaviour of the Vertical Axis Wind Turbine (VAWT), present technological state, new finding through modelling work and future direction of VAWTs were reviewed. It was observed that VAWT plays a vital role in the present energy crisis. Ones can foresee that human being dwelling in a world with wind turbines and solar panels due to present energy crisis with the non-renewable energy. Wind energy has been identified as a promising renewable option Although the full life cycle accounting shows VAWTs are advantageous on a cost basis or materials basis over horizontal axis wind turbines (HAWTs), Currently the VAWTs do not generate enough electricity due to some challenges which discussed in this paper. Drag driven VAWT (Savonius type), lift driven VAWT (Darrieus type) and hybrid of both (D+S) turbine efficiencies can be increased by adding the deflector system that guides the wind towards the turbine blades. A lot of researches are ongoing at present in this level. From the vast survey of the present technological states of VAWT, it was observed that China is the leading researcher in this field for the past few years while European countries serve their place in this research area.

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