Wind energy is the fastest growing alternate source of energy in the world since its purely economic potential is complemented by its great positive environmental impact. The wind turbine, whether it may be a Horizontal-Axis Wind Turbine (HAWT) or a Vertical-Axis Wind Turbine (VAWT), offers a practical way to convert the wind energy into electrical or mechanical energy. Although this book focuses on the aerodynamic design and performance of VAWTs based on the Darrieus concept, it also discusses the comparison between HAWTs and VAWTs, future trends in design and the inherent socio-economic and environmental friendly aspects of wind energy as an alternate source of energy.

Wind turbine design with emphasis on Darrieus concept Ion Paraschivoiu

Wind energy, together with other renewable energy sources, are expected to grow substantially in the coming decades and play a key role in mitigating climate change and achieving energy sustainability. One of the main challenges in optimizing the design, operation, control, and grid integration of wind farms is the prediction of their performance, owing to the complex multiscale two-way interactions between wind farms and the turbulent atmospheric boundary layer (ABL). From a fluid mechanical perspective, these interactions are complicated by the high Reynolds number of the ABL flow, its inherent unsteadiness due to the diurnal cycle and synoptic-forcing variability, the ubiquitous nature of thermal effects, and the heterogeneity of the terrain. Particularly important is the effect of ABL turbulence on wind-turbine wake flows and their superposition, as they are responsible for considerable turbine power losses and fatigue loads in wind farms. These flow interactions affect, in turn, the structure of the ABL and the turbulent fluxes of momentum and scalars. This review summarizes recent experimental, computational, and theoretical research efforts that have contributed to improving our understanding and ability to predict the interactions of ABL flow with wind turbines and wind farms.

https://link.springer.com/content/pdf/10.1007/s10546-019-00473-0.pdf

Wind-Turbine and Wind-Farm Flows: A Review

The Darrieus wind turbine: Proposal for a new performance prediction model based on CFD

Meeting future world energy needs while addressing climatic changes has led to greater strain on conventional power sources. One of the viable sustainable energy sources is wind. But the installation large scale wind farms has a potential impact on the climatic conditions, hence a decentralized small scale wind turbines is a sustainable option. This paper presents review of on different types of small scale wind turbines i.e., horizontal axis and vertical axis wind turbines. The performance, blade design, control and manufacturing of horizontal axis wind turbines were reviewed. Vertical axis wind turbines were categorized based on experimental and numerical studies. Also, the positioning of wind turbines and aero-acoustic aspects were presented. Additionally, lessons learnt from various studies/countries on actual installation of small wind turbines were presented.

A review on small scale wind turbines

Performance investigation of H-rotor Darrieus turbine with new airfoil shapes

This paper presents a model for the evaluation of optimal spatial grid node distribution in the CFD analysis of a Darrieus vertical axis micro wind turbine, by analyzing the trends over a 360° rotation of some indicators of near-blade mesh quality. To this purpose, a complete validation campaign has been conducted through a systematic comparison of numerical simulations with wind tunnel experimental data. Both two-dimensional and three-dimensional grids, characterized by average y+ values of 30 and 1, have been tested by applying some statistical techniques as a guidance in selecting the appropriate grid configuration and corresponding turbulence model. Finally, the tip downstream recirculation zone due to the finite blade extension and the influence of spokes have been analyzed, achieving a numerical quantification of the influence of induced drag and spokes drag on overall rotor performance.Copyright © 2010 by ASME

Modeling Strategy and Numerical Validation for a Darrieus Vertical Axis Micro-Wind Turbine

This paper presents a mean for reducing the torque variation during the revolution of a vertical-axis wind turbine (VAWT) by increasing the blade number. For this purpose, two- dimensional CDF analysis have been performed on a straight-bladed Darreius-type rotor. After describing the computati onal model, a complete campaign of simulations based on full RANS unsteady calculations is proposed for a three, four and five -bladed rotor architecture characterized by a NACA 0025 airfoil. For each proposed rotor configuration, flow field characteri stics are investigated at several values of tip speed ratio, allowing a quantification of the influence of blade number on flow geometric features and dynamic quantities, such as rotor torq ue and power. Finally, torque and power curves are compared for t he analyzed architectures, achieving a quantification of the ef fect of blade number on overall rotor performance.

/pdf/effect-of-blade-number-on-a-straight-bladed-vertical-axis-3gios02xcw.pdf

Effect of Blade Number on a Straight-Bladed Vertical-Axis Darreius Wind Turbine

This paper presents a model for the evaluation of energy performance and aerodynamic forces acting on a small helical Darrieus vertical axis wind turbine depending on blade inclination angle. It consists of an analytical code coupled to a solid modeling software capable of generating the desired blade geometry depending on the desired design geometric parameters, which is linked to a finite volume CFD code for the calculation of rotor performance. After describing and validating the model with experimental data, the results of numerical simulations are proposed on the bases of five machine architectures, which are characterized by an inclination of the blades with respect to the horizontal plane in order to generate a phase shift angle between lower and upper blade sections of 0 deg, 30 deg, 60 deg, 90 deg, and 120 deg for a rotor having an aspect ratio of 1.5. The effects of blade inclination on tangential and axial forces are first discussed and then the overall rotor torque is considered as a function of azimuthal position of the blades. Finally, the downstream tip recirculation zone due to the finite blade extension is analyzed for each blade inclination angle, achieving a numerical quantification of the influence of induced drag on rotor performance, as a function of both blade element longitudinal and azimuthal positions of the blade itself.

Marco Raciti Castelli

Papers

The Darrieus wind turbine: Proposal for a new performance prediction model based on CFD

Modeling Strategy and Numerical Validation for a Darrieus Vertical Axis Micro-Wind Turbine

Effect of Blade Number on a Straight-Bladed Vertical-Axis Darreius Wind Turbine

Effect of Blade Inclination Angle on a Darrieus Wind Turbine

Optimization of a Darrieus vertical-axis wind turbine using blade element – momentum theory and evolutionary algorithm