Performance of a High Tip Speed Ratio H-Darrieus in the Skewed Flow on a Roof

Mertens, Sander; Kuik, Gijs van; Bussel, Gerard van

doi:10.1115/wind2003-523

Cited by 7 publications

(11 citation statements)

References 2 publications

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“…In recent years, interest in the VAWT design has been boosted by an increasing desire for the integration of wind energy into the built environment, where the VAWT presents several potential advantages over the more common HAWT (horizontal axis wind turbine): the VAWT avoids the requirement for yaw (turn to face the wind), may have lower sound emission (due lower tip speed ratio operation, [1]), and shows increased performance in skewed flow [2] -a likely flow scenario over a roof-top. However, while the HAWT is highly developed and is currently used for all large-scale wind farms and numerous small-scale applications in rural locations, the VAWT concept is considerably less-developed.…”

Section: Nomenclature 1 Introductionmentioning

confidence: 99%

PIV measurements and CFD simulation of the performance and flow physics and of a small‐scale vertical axis wind turbine

2013

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The aerodynamics generated by a small small-scale vertical axis wind turbine (VAWT) are illustrated in detail as a NACA0022 rotor blade carries out a complete rotation at three tip speed ratios. These aerodynamic details are then linked to the wind turbine performance. This is achieved by using detailed experimental measurements of performance and near blade PIV and also using a 2D RANS based CFD model. Uniquely therefore, the CFD model is validated against both PIV visualisations and performance measurements.At low tip speed ratios ( = 2), the flow field is dominated by large scale stalling behaviour as shown in both the experimental results and simulations. The onset of stall appears to be different between the experiment and simulation, with the simulation showing a gradual separation progressing forwards from the trailing edge, while the experiment shows a more sudden leading edge roll-up. Overall, similar scales of vortices are shed at a similar rate in both. The most significant CFD-PIV differences are observed in predicting flow reattachment. At a higher tip speed ratio ( = 3), the flow separates slightly later than in the previous condition and as occurs in the lower tip speed ratio, the main differences between the experiment and the simulation are in the flow reattachment process, specifically that the simulations predicts a delay in the process. At a tip speed ratio of 4, smaller predicted flow separation in the latter stages of the upwind part of the rotation is the main difference in comparison to the experiment.

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Section: Nomenclature 1 Introductionmentioning

confidence: 99%

PIV measurements and CFD simulation of the performance and flow physics and of a small‐scale vertical axis wind turbine

2013

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“…Analogous to the work of Mertens et al [15][16], the numerical model for the performance estimation of an H-Darrieus turbine in skewed flow developed in this study was conceived with a theoretical approach based on the Momentum Models [22][23][24][25]. This theoretical approach was thought to provide an acceptable level of accuracy coupled with a reduced computational cost; moreover, due to the direct relationship between thrust through the rotor and the aerodynamic loads on the blades, the influence of relevant design parameters can be straightforwardly estimated with this method, especially as regards the effect of the aerodynamic characteristics of the airfoils, which are particularly critical in the evaluation of skewed flow effects.…”

Section: Proposed Model 41 Theoretical Approachmentioning

confidence: 87%

“…( On the other hand, recent experimental investigations on Darrieus turbines surprisingly showed an opposite behavior of this typology of rotors in skewed flow conditions [15][16][17][18]; in Darrieus rotors, the performance is enhanced for relatively small yaw angles (up to approximately 25°-30°, with a dependence on the geometric proportions of the rotor),…”

Section: An Improved Model For the Performance Estimation Of An H-darmentioning

confidence: 99%

“…Mertens et al [15,16] first investigated the physics connected to a skewed flow by means of a wind tunnel campaign with performance measurements on a low-solidity two-bladed H-Darrieus turbine. The experimental data were also compared with a numerical model, based on the Momentum Models, which was based on a modified evaluation of both the turbine swept area and the aerodynamic efficiency of the airfoils.…”

Section: State-of-the-artmentioning

confidence: 99%

“…Moreover, in order to accurately describe the different energy extraction of each section of the turbine, the rotor was divided into three sectors of height ( Figure 4) [15]. Figure 4: Rotor's model proposed by Mertens et al [15][16].…”

Section: State-of-the-artmentioning

confidence: 99%

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An Improved Model for the Performance Estimation of an H-Darrieus Wind Turbine in Skewed Flow

et al. 2012

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Small turbines are considered one of the most promising technologies for an effective diffusion of renewable energy sources in new installation contexts with a high degree of integration with human activity (e.g. the urban environment). In these new installations, however, the real working conditions can be far from the nominal ones. In particular, the turbine functioning can be noticeably affected by misalignments between the oncoming flow and the axis of the rotor; differently from horizontal-axis wind turbines, whose performance is decreased by a skew angle, H-Darrieus turbines are thought to take advantage from this condition in some cases. In this study, an improved model for the performance prediction of H-Darrieus rotors under skewed flow was developed. In detail, a theoretical approach based on Momentum Models was properly modified to account for the variations induced by the new direction of the flow which invests the rotor. In particular, the modifications in the aerodynamic characteristics of the airfoils, the swept area and the streamtubes distribution were modeled. The performance predictions of the new model were compared both with experimental data available in the technical literature and with the results of wind tunnel tests purposefully carried out on a full scale model of an H-Darrieus turbine. Notable agreement has been constantly obtained between simulations and experiments.

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Innovative Power-Augmentation-Guide-Vane Design of Wind-Solar Hybrid Renewable Energy Harvester for Urban High Rise Application

Tong¹,

Maslan²,

Chew³

et al. 2010

AIP Conference Proceedings

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To generate greater quantities of energy from wind, the most efficient solution would be by increasing the wind speed. Also, due to the decreasing number of economic wind energy sites, there are plans to place wind turbines closer to populated areas. To site wind turbines out from rural areas, the current problems of wind turbines need to be resolved, especially visual impact, poor starting behavior in low wind speeds, noise and danger caused by blade failure. In this paper, a patented wind-solar hybrid renewable energy harvester is introduced. It is a compact system that integrates and optimizes several green elements and can be built on the top (or between upper levels) of high rise buildings or structures. This system can be used in remote and urban areas, particularly at locations where the wind speed is lower and more turbulent. It overcomes the inferior aspect on the low wind speed by guiding and increasing the speed of the high altitude free-stream wind through fixed or yaw-able power-augmentation-guidevane (PAGV) before entering the wind turbine (straight-bladed vertical axis wind turbine, VAWT in this project) at center portion. PAGV is an innovative design where its appearance or outer design can be blended into the building architecture without negative visual impact. From the studies, it is shown that the wind speed increment in the PAGV can be produced according to the Bernoulli's principle. Computational fluid dynamics (CFD) simulation is used to optimize the geometry of the PAGV and the simulation results demonstrated the technical possibility of this innovative concept. The PAGV replaces the free air-stream from wind by multiple channels of speed-increased and directional-controlled air-stream. With the PAGV, this lift-type VAWT can be self-started and its size can be reduced for a given power output. The design is also safer since the VAWT is enclosed by the PAGV. By integrating the PAGV with the VAWT (the diameter and height of the PAGV are 2 times larger than the VAWT's), the predicted power generated (at free-stream wind speed of 3.5 m/s) is 1.25 times higher than the VAWT that has the same size as the PAGV. This new wind energy generation configuration should generate interest in the international market, even for regions with weaker winds. The correlation between CFD simulation and wind tunnel test will be carried out and reported elsewhere.

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Performance of a High Tip Speed Ratio H-Darrieus in the Skewed Flow on a Roof

Cited by 7 publications

References 2 publications

PIV measurements and CFD simulation of the performance and flow physics and of a small‐scale vertical axis wind turbine

PIV measurements and CFD simulation of the performance and flow physics and of a small‐scale vertical axis wind turbine

An Improved Model for the Performance Estimation of an H-Darrieus Wind Turbine in Skewed Flow

Innovative Power-Augmentation-Guide-Vane Design of Wind-Solar Hybrid Renewable Energy Harvester for Urban High Rise Application

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