Performance Improvement of a Drag Hydrokinetic Turbine (original) (raw)
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Performance analysis of a Savonius hydrokinetic turbine having twisted blades
Renewable Energy, 2017
In the quest for renewable energy sources, kinetic energy available in small water streams, river streams or human-made canals may provide new avenue which can be harnessed by using hydrokinetic turbines. Savonius hydrokinetic turbine is vertical axis turbine having drag based rotor and suitable for a lower flow velocity of the water stream. In order to enhance the efficiency of the turbine, this paper aims to analyze the performance of twisted blade Savonius hydrokinetic turbine. Using CFD analysis, an attempt has been made to optimize blade twist angle of Savonius hydrokinetic turbine. The simulation of a twisted Savonius hydrokinetic turbine having two blades has been carried out to investigate the performance. Commercial unsteady Reynolds-Averaged Navier-Stokes (URANS) solver in conjunction with realizable k-ε turbulence model has been used for numerical analysis. Fluid flow distributions around the rotor have been analyzed and discussed. It has been found that Savonius hydrokinetic turbine having a twist angle of 12.5° yields a maximum coefficient of power as 0.39 corresponding to a TSR value of 0.9 for a given water velocity of 2 m/s.
Development of horizontal axis hydrokinetic turbine using experimental and numerical approaches
2020
Hydrokinetic energy conversion systems (HECSs) are emerging as viable solutions for harnessing the kinetic energy in river streams and tidal currents due to their low operating head and flexible mobility. This study is focused on the experimental and numerical aspects of developing an axial HECS for applications with low head ranges and limited operational space. In Part I, blade element momentum (BEM) and neural network (NN) models were developed and coupled to overcome the BEM's inherent convergence issues which hinder the blade design process. The NNs were also used as a multivariate interpolation tool to estimate the blade hydrodynamic characteristics required by the BEM model. The BEM-NN model was able to operate without convergence problems and provide accurate results even at high tip speed ratios. In Part II, an experimental setup was developed and tested in a water tunnel. The effects of flow velocity, pitch angle, number of blades, number of rotors, and duct reducer were investigated. The performance was improved as rotors were added to the system. However, as rotors added, their contribution was less. Significant performance improvement was observed after incorporating a duct reducer. In Part III, a computational fluid dynamics (CFD) simulation was conducted to derive the optimum design criteria for the multi-turbine system. Solidity, blockage, and their interactive effects were studied. The system configuration was altered, then its performance and flow characteristics were investigated. The experimental setup was upgraded to allow for blockage correction. Particle image velocimetry was used to investigate the wake velocity profiles and validate the CFD model. The flow characteristics and their effects on the turbines performance were analyzed.
Numerical modeling of vertical-axis and transverse-flow hydrokinetic turbine in the Loire river
Hydrokinetic turbines can recover the kinetic energy of marine or river currents. The Hydrofluv research and development project (funded by FUI with the support of the Tenerrdis, DERBI and DREAM clusters) aims to demonstrate the feasibility and acceptability of vertical-axis and transverse-flow turbines. Members of the Hydrofluv project, Hydroquest, FOC Transmissions, ERNEO, Biotope, EDF, Artelia and the LEGI laboratory are working both on improving the machines and on a more complete commercial offer (administrative authorizations, impact studies and profitability). Numerical modeling conducted by the LEGI laboratory and Hydroquest has led to the definition of the machine’s characteristics and main parameters. The incorporation of these terms in a larger three-dimensional numerical model has enabled other parameters to be analyzed, such as head loss around the machine (variation in the free surface and current), the interactions between machines and hydrosedimentary impacts. Several academic studies have validated the developments made by comparing the models. The practical application concerns a study of the prototype scheduled to be placed in the Loire at Orleans at the end of 2014. The model accurately represents the impacts of a machine on its environment and has proved to be highly representative compared to more specific local models, which are for the moment two-dimensional and require longer calculation times.
Performance of a hydrokinetic turbine using a theoretical approach
Energy Reports, 2020
Regarding the interest in renewable energies, several sources of energy production have been studied and still under improvement. In this work, we are interested in harnessing marine energy currents exploiting the hydrokinetic turbines. The purpose of this study is to provide a comprehensive assessment of the hydrodynamic loads of a 3-blade horizontal-axis marine turbine using a rotor model adapted to the Moroccan potential. For that, the Blade Element Momentum (BEM) is used to calculate the hydrodynamic loads, to estimate the energetic performance, and to determine the blade optimal parameters for a turbine. In additions, the resulting equations are solved in order to obtain the hydrodynamic loads. For validation, a comparison of pressure coefficients along the chord length was made with the results of the Blade software. The Computations were accomplished for a specific NACA profile. c
2016
Tidal stream turbines offer a promising means of producing renewable energy at foreseeable times and of predictable quantity. However, the turbines may have to operate under wave-current conditions that cause high velocity fluctuations in the flow, leading to unsteady power output and structural loading and, potentially, to premature structural failure. Consequently, it is important to understand the effects that wave-induced velocities may have on tidal devices and how their design could be optimised to reduce the additional unsteady loading. This paper describes an experimental investigation into the performance of a scale-model threebladed HATT (horizontal axis tidal stream turbine) operating under different wave-current combinations and it shows how changes in the blade pitch angle can reduce wave loading. Tests were carried out in the recirculating water channel at the University of Liverpool, with a paddle wavemaker installed upstream of the working section to induce surface w...
Applied Energy, 2009
The energy in flowing river streams, tidal currents or other artificial water channels is being considered as viable source of renewable power. Hydrokinetic conversion systems, albeit mostly at its early stage of development, may appear suitable in harnessing energy from such renewable resources. A number of resource quantization and demonstrations have been conducted throughout the world and it is believed that both in-land water resources and offshore ocean energy sector will benefit from this technology. In this paper, starting with a set of basic definitions pertaining to this technology, a review of the existing and upcoming conversion schemes, and their fields of applications are outlined. Based on a comprehensive survey of various hydrokinetic systems reported to date, general trends in system design, duct augmentation, and placement methods are deduced. A detailed assessment of various turbine systems (horizontal and vertical axis), along with their classification and qualitative comparison, is presented. In addition, the progression of technological advancements tracing several decades of R&D efforts are highlighted.
Design Considerations of a Straight Bladed Darrieus Rotor for River Current Turbines
ISIE, 2006
Hydrokinetic turbines convert kinetic energy of moving river or tide water into electrical energy. In this work, design considerations of river current turbines are discussed with emphasis on straight bladed Darrieus rotors. Fluid dynamic analysis is carried out to predict the performance of the rotor. Discussions on a broad range of physical and operational conditions that may impact the design scenario are also presented. In addition, a systematic design procedure along with supporting information that would aid various decision making steps are outlined and illustrated by a design example. Finally, the scope for further work is highlighted.
Computational Fluid Dynamic Simulation of Vertical Axis Hydrokinetic Turbines
Computational Fluid Dynamics Simulations [Working Title]
Hydrokinetic turbines are one of the technological alternatives to generate and supply electricity for rural communities isolated from the national electrical grid with almost zero emission. These technologies may appear suitable to convert kinetic energy of canal, river, tidal, or ocean water currents into electricity. Nevertheless, they are in an early stage of development; therefore, studying the hydrokinetic system is an active topic of academic research. In order to improve their efficiencies and understand their performance, several works focusing on both experimental and numerical studies have been reported. For the particular case of flow behavior simulation of hydrokinetic turbines with complex geometries, the use of computational fluids dynamics (CFD) nowadays is still suffering from a high computational cost and time; thus, in the first instance, the analysis of the problem is required for defining the computational domain, the mesh characteristics, and the model of turbulence to be used. In this chapter, CFD analysis of a H-Darrieus vertical axis hydrokinetic turbines is carried out for a rated power output of 0.5 kW at a designed water speed of 1.5 m=s, a tip speed ratio of 1.75, a chord length of 0.33 m, a swept area of 0.636 m 2 , 3 blades, and NACA 0025 hydrofoil profile.
Hydrokinetic turbine array characteristics for river applications and spatially restricted flows
Renewable Energy, 2016
Multiple hydrokinetic turbines in three array configurations were characterized computationally by employing Reynolds Averaged Navier-Stokes equations. The simulations were conducted for pre-existing turbines operating at their optimum power coefficient of 0.43 which was obtained by design and optimization process. Mechanical power for two adjacent units was predicted for various lateral separation distances. An additional two-by-two turbine array was studied, mimicking a hydro-farm. Numerical simulations were performed using actual physical turbines in the field rather than using low fidelity models such as actuator disk theory. Steady state simulations were conducted using both Coupled and SIMPLE pressure-velocity solvers. Steady three dimensional flow structures were calculated using the k-u Shear Stress Transport (SST) turbulence model. At a lateral separation distance of 0.5D t , the turbines produced an average 86% of the peak power a single turbine producing. Interaction effects at lateral separation distances greater than 2.5D t were negligible. The wake interaction behind the upstream turbines causes a significant performance reduction for downstream turbines within 6D t longitudinal spacing. Downstream turbines employed for the present study performed around 20% or less of a single unit turbine performance for the same operating conditions. Downstream turbines yielded comparable reductions in power to that of experimental results.
Ocean Engineering, 2020
A Savonius turbine is a vertical axis hydrokinetic turbine (VAHT) utilizes in low-speed channels and rivers. In comparison with the other hydrokinetic turbines, the Savonius turbine is simple in construction and installation, and involves less installation cost; however, these turbines have low torque and power coefficients in comparison with other hydrokinetic turbines. The idea of this paper is utilizing a simple barrier to deviate the fluid flow from the reversing bucket of the Savonius turbine to enhance its generated power. In order to investigate the most appropriate length of the barrier, numerical modeling has been performed by applying computational fluid dynamics (CFD). The continuity, Reynolds Averaged Navier-Stokes-RANS equations and the SST transition turbulence model are numerically solved. The validation of the numerical simulation is assessed based on the experimental data of Sandia laboratories, and the results indicated good agreement with experimental data. Thereupon, the model is utilized for optimizing the length of the barrier in various cases. The power coefficient of different cases is compared with the obstacle-less conventional Savonius turbine. The results of this analysis reveal that utilizing a barrier in its optimum length increases the maximum generated power by about 18 percent.