Performance Of Hydrokinetic Turbine Research Articles

Effect of Semi-elliptical Outer Blade-surface on the Savonius Hydrokinetic Turbine Performance: A Numerical Investigation

Effect of Semi-elliptical Outer Blade-surface on the Savonius Hydrokinetic Turbine Performance: A Numerical Investigation

Enhancing savonius rotor model with additional grooves on hydrokinetic turbine performance

Hydrokinetic turbines use different rotors for technological and economic reasons. Even though it performs poorly, vertical-axis hydrokinetic turbines use the Savonius rotor. The object of research is a Savonius rotor model with additional grooves. The study addresses the need to improve the efficiency and overall performance of Savonius rotor models in hydrokinetic turbines, which are widely used for harnessing energy from flowing water currents. The problem involves understanding how different groove configurations affect the aerodynamic behavior and energy extraction efficiency of the Savonius rotor in hydrokinetic turbine applications. The test results revealed that incorporating grooves led to notable improvements in efficiency (ɳ) and coefficient of drag (CD). Grooved blades exhibited a maximum efficiency of 30.97 % and a maximum drag coefficient of 2.71. Notably, blades with a groove width of 12.5 mm emerged as the optimal model, demonstrating an efficiency peak of 35.66 % and a drag coefficient 3.08. This indicates a substantial increase in efficiency by 4.69 % and a corresponding rise in the drag coefficient by 0.37 for grooved blades. The grooves on grooved blades increase friction, improving performance. Grooved rotor blades improve turbine performance significantly. Savonius rotor models in hydrokinetic turbines extract more energy by optimizing groove width and arrangement to maximize drag coefficient and efficiency. This research affects hydrokinetic turbine design and optimization for renewable energy generation. Engineers and designers can improve the performance and efficiency of the Savonius rotor model in hydrokinetic turbine applications by applying this study’s findings

Evaluation of the performance of the Savonius hydrokinetic turbines in the straight and curved channels using advanced machine learning methods

Evaluation of the performance of hydrokinetic turbines is an essential subject in the renewable energy field. In this regard, advanced machine learning methods including hybrid CatBoost and standalone Catboost and linear regression were used for the first time for the straight channel data and channel bend data. The hybrid models were developed using whale optimization (WO), grey wolf optimization (GWO), and Bayesian optimization (BO) algorithms. Sensitivity analysis was also conducted to find the most influential parameters in the best model. Results showed that the hybrid models can predict the goal parameters, including the coefficient of the power (CP), the maximum value of the coefficient of the power (CPmax), and the tip speed ratio corresponding to the Cpmax (TSRmax) better than the standalone models. Among the models, GWO-CB is the best model, even in the k-fold cross-validation scenario. The R2 value of the GWO-CB reached 0.97, 0.94, and 0.84 for the CP, CPmax, and TSRmax, respectively. Among the effective parameters, the lateral position of the returning blade deflector and the number of stages had the maximum and minimum effects on the best model, respectively. The effect of the position of the turbines in the channel bend, which was considered in this research for the first time, was significant in the models.

Performance Analysis of Hydrokinetic Turbine Using Shroud Ratio Comparison under Yaw Misalignment Condition

This research aims to analyze the performance of hydrokinetic turbines under yaw misalignment conditions using descriptive statistical methods on coefficient of power (Cp) data. Tests were conducted at water velocities of 0.7, 0.9, and 1.1 m/s for three types of turbine shrouds consisting of turbines without shrouds, turbines with two different types of shrouds, at yaw angles from 0° to 25° with 5° intervals. The study concludes that the performance of each turbine type is significantly influenced by the combination of water flow velocity and yaw angle. The diffuser type has the highest Cp value at every yaw angle, but its performance decreases with increasing yaw angle. The Blade type has poorer performance compared to the diffuser at every yaw angle and has the best performance at a combination of 1.1 m/s velocity and 5° yaw angle. Meanwhile, the shroud type has more stable performance and is not greatly affected by variations in velocity and yaw angle. Based on the analysis of changes in average Cp values with changes in yaw angle at V 0.7 m/s, all three turbine types experienced an increase in Cp value at a yaw angle of 5, with the shroud experiencing the most significant increase. At V 0.9 m/s, the diffuser and shroud types were able to maintain their average Cp values at every yaw angle, while the blade type decreased with increasing yaw angle and experienced a significant decrease at a yaw angle of 25. At V 1.1 m/s, the diffuser and blade types experienced a decrease in performance with every increase in yaw angle, but the shroud type was able to maintain the same Cp value and even experienced a significant increase at a yaw angle of 5.

Performance evaluation of the savonius hydrokinetic turbine using soft computing techniques

Savonius hydrokinetic turbine is a vertical axis turbine suitable for generating electrical power used in rivers and canals. The performance of the turbine is described in terms of power coefficient. The power coefficient (CP) depends on input variables such as aspect ratio, overlap ratio, blockage ratio, number of blades, blade arc angle, blade shape factor, twist angle, Reynolds number, and Tip Speed Ratio (TSR). In this study, different soft computing methods, namely CatBoost, Artificial Neural Network (ANN), Random Forests (RF), Multivariate Adaptive Regression Splines (MARS), Adaptive Neuro-Fuzzy Inference System (ANFIS), ANFIS-Genetic algorithm (ANFIS-GA), ANFIS-Slime Mold Algorithm (ANFIS-SMA), ANFIS-Marine Predators Algorithm (ANFIS-MPA) along with Linear Regression (LR) were used to predict the power coefficient of Savonius hydrokinetic turbines for the first time. In order to obtain appropriate data, experimental tests were conducted in an open water channel for different design configurations of Savonius turbines. Further, more data were collected from different references. These data were used for the training and testing process of the models. The precision of the methods was evaluated using multiple statistical indices. Three different training-testing scenarios were prepared to provide a reliable predictive model, and in all scenarios, the CatBoost method was superior. Sensitive analysis showed that aspect ratio is the most important design parameter among all effective parameters. As a result, the CatBoost is recommended to predict a Savonius hydrokinetic turbine's performance considering multi-input variables.

An automatic parallel scheme to design an augmented hydrokinetic river turbine using a simulation-based optimization approach

The effect of diffuser-enhanced flow on the energy extraction performance of hydrokinetic turbines is widely reported in the literature. In this context, this work combines automatic scripting for geometry construction and meshing, together with a simulation-based approach using particle-swarm optimization with Computational Fluid Dynamics (CFD) to design an augmented hydrokinetic river turbine (HKRT). The goal is to achieve an increase in mass flow in the throat of the diffuser and then to design an ad-hoc set of rotor blades. The optimization is performed in two separate stages: Continuous optimization for the diffuser and discrete optimization for the rotor blades. The complex shape of the rotor blades in terms of the chord, twist, and thickness distribution was parametrized with second-order Bezier curves, which facilitates the correlation between the blade’s shape and its performance, proving to be more intuitive to the experienced designer. Furthermore, a novel search and discrete arrangement of feasible design variables are proposed, which allows for reducing the computational costs of this large optimization problem. Results show that the optimized diffuser achieved a flow rate increase of 279%, and the ad-hoc 1.5 [m] in diameter rotor delivers a power of 11.98 [kW] with an efficiency of 0.3385%.

Numerical study of the effect of tip-speed ratio on hydrokinetic turbine wake recovery

The predictive capabilities of blade-resolved unsteady Reynolds averaged Navier-Stokes (URANS) and detached eddy simulation (DES), the most commonly used hybrid RANS/large eddy simulation (LES) model, are assessed for hydrokinetic turbine performance and mean and turbulent flows in the intermediate-wake region, and results for a range of tip-speed ratio encompassing design and off-design conditions are analyzed to understand the wake recovery mechanism. The performance predictions compared within 5% of the experimental data. Both URANS and DES models performed reasonably well for the near wake predictions, where the errors were <15%. DES outperformed URANS for both mean wake deficit and turbulence predictions in the intermediate-wake region and both quantities compared within 10% of the experiments. The improved prediction by DES is because of its ability to predict the tip vortex breakdown, which plays a critical role in the wake recovery, especially for higher tip speed ratios (λ). However, DES significantly underpredicted the turbulence predictions in the near-wake region, which could be partly due to the negligence of free-surface effects and partly due to modeling issues, namely modeled stress depletion. The study reveals that the tip vortex breakdown mechanism depends on λ. For lower values of λ, instabilities generated in the root vortex core are identified to be the cause of breakdown. For higher values, the breakdown occurred because of the instabilities generated during the vortex filament entanglement. Future work should focus on investigation of other hybrid RANS/LES models to address the limitations of the DES models, and extension of the study to include free-surface effects.

Numerical and experimental study of hydrofoil-flap arrangements for hydrokinetic turbine applications

In this work, the efficiency of two horizontal-axis hydrokinetic turbines, whose blades were designed with and without multi-element hydrofoil cross-sections, has been numerical and experimentally investigated for tip speed ratio (λ) values ranging between 2.5 and 9.0 to compare the experimental rotor performance with numerical results. The Eppler 420 hydrofoil was used for the design of the blades applying the blade element momentum (BEM) theory. The variation of the power coefficient curve of the turbines was analyzed by using computational fluid dynamics (CFD) and experimental tests through ANSYs Fluent software with six-degrees of freedom (6-DoF) user-defined function (UDF) method and an open hydraulic channel, respectively. Numerically, for the turbine with a multi-element hydrofoil and without a multi-element (traditional) hydrofoil, maximum power coefficients (CPmax) of 0.5050 and 0.419 (at a λ value equal to 7.129 and 6.739, respectively) were obtained. It is worth noting that a reasonable agreement between the numerical and the experimental results was achieved. In this regard, the blade with a multi-element hydrofoil has a positive influence on the hydrokinetic turbine performance; therefore, it can be used for power generation in river or marine systems.

Free energy-extraction using Savonius hydrokinetic rotor with dual splitters

Hydrokinetic energy is a broadly available form of low-grade energy in countries like India, where irrigation canals are available in huge areas. To utilize this energy, hydrokinetic turbines are used. Out of many hydrokinetic turbines, efforts are made to improve Savonius hydrokinetic turbine's performance in the present work. The Savonius rotor profile is modified by providing a dual splitter-like shape on the blade's concave side. The two cases were selected for finding the optimum splitter position of both the splitter. The upper (top) splitter kept fixed and radially placed the second splitter in the first case. In the second case, the lower (bottom) splitter fixed and moving another splitter radially. Validated Computational analysis was done to analyze performance after modification. The fluid material was taken as water with standard properties. The improvement was observed for the specific position of splitters by 7.3% from conventional design.

Assessment of turbine stages and blade numbers on modified 3D Savonius hydrokinetic turbine performance using CFD analysis

PurposeIn Southeast Asia, the renewable energy produced from hydropower systems has significant potential. Therefore, adequate development is needed to prevent future energy-related crises. This study, therefore, aims to determine the variations effects in geometry and the geometrical factors on turbine performance.Design/methodology/approachThe developed aspects are selected to determine the blade shape, its number and multistage requirements. The study was conducted in 3D simulation, with Ansys software used to calculate a series of computational fluid dynamic problems. The aspect ratio applied in this study utilized the ratio of the overall diameter of the rotor height (D / H), which is 1.FindingsThe results showed that the highest Cp-max value, number of blades and stages were 0.2, two and three, respectively. Furthermore, these attributes combined to improve the performance of hydroturbines.Research limitations/implicationsThe research was fully conducted using numerical simulation, which requires sustainable research in the form of laboratory experiments. Also, pioneer experiments were conducted using benchmarking to ensure the results obtained are reliable.Practical implicationsHydropower is one of the best renewable energy sources in Indonesia with a large potential in the archipelago and tropical countries due to rivers and various water sources. The current generated is a useful reference for Savonius design.Originality/valueThe originality of this study is to examine the three aspects of the geometry of the rotor, such as the number and shape of blades, as well as the stages in the same boundary conditions. Therefore, the comparison of the effects of changes in geometry on turbine performance is more acceptable and complete compared to the pioneer works, which focused on a parameter. This research combines several aspects to determine the effect of rivers and various water sources on the hydroturbine.

Experimental, Numerical and Application Analysis of Hydrokinetic Turbine Performance with Fixed Rotating Blades

In this study, a hydrokinetic turbine is designed for the high-altitude regions where local electricity network lines are difficult to reach. If there was a stream flow around, electricity production could be possible and necessary because of environmental reasons. The performance of the hydrokinetic turbine was investigated experimentally and numerically. The numerical analyses of the turbine system were performed via MATLAB/Simulink version R2014a. Except power-based performance characteristics, efficiency of the system in terms of installation and necessary investment costs were also investigated. It is calculated that the system to be established on a river with a water flow rate of 30 m3/h will meet the investment cost in approximately 8 years.

A computational investigation to analyze the effects of different rotor parameters on hybrid hydrokinetic turbine performance

Cross flow hydrokinetic turbines have been considered a decent choice for riverine applications. Under the present work, performance of hybrid rotor cross flow hydrokinetic has been investigated for different rotor parameters. The proposed hybrid rotor is the combination of two conventional turbine rotors (Savonius and Darrieus). Investigations have been performed by considering flow velocity varying in the range from 0.5 m/s to 2.0 m/s. The performance of hybrid rotor was assessed in term of power coefficient (CP) and torque coefficient (CT). Further, comparison of hybrid rotor and single Darrieus rotor has been carried out on the basis of their performance. Flow behaviour across the turbine vicinity is analyzed and discussed with the pressure, velocity contours and velocity streamlines. It has been found that radius ratio and attachment angle play a crucial role in performance enhancement with reduction in torque fluctuations. For the considered range of rotor parameters, the maximum power coefficient (CPmax) and average torque coefficient (CTavg) were obtained as 0.109 and 0.1276 corresponding to radius ratio of 0.6 at an attachment angle of 90°. Further, power coefficient and torque coefficient of hybrid rotor are found to be improved by 37.97% and 35.88% respectively as compared to single Darrieus rotor.

EFFECT OF FLOW STEERING ANGLE TOWARD THE HYDROKINETIC TURBINE PERFORMANCE

The kinetic turbine is one of the solutions for use in low-speed river flows ranging from 0.01–2.8 m/s. This kinetic turbine is used as a conversion equipment to convert the water kinetic energy into an electrical energy. The working principle of a kinetic turbine is utilizing and relies on the water kinetic energy. Water flowing into the turbine area will produce a momentum on the turbine blades. This momentum change would then push the turbine blades and finally spin the turbine runner. The aim of research is thedetermination of the effect of water flow steering angle (a) and water flow rate variation in the kinetic turbine performance. This research uses vertical axis kinetic turbines with eight curve blade attached to the turbine runner. The variables used are two values of water flow steering angle, namely 25°and 35°. The water flow rate variation of 30 m3/h, 35 m3/h, 40 m3/h and 45 m3/h. The method used in this study uses a real experimental method. These two variations would then compare with the result of a hydrokinetic turbine performance done on the previous research. The results show that the water flow steering angle a affected the kinetic turbine performance (power, efficiency and torque). From these several water flow steering angle and water flow rate variations, the turbine performance with a 35° water flow steering angle get the highest performance compared with the use of 25° and 14° water flow steering angle. The greater the flow angle and the greater the water flow rate, the greater the torque, power and efficiency. The highest turbine power produced, P=17.5 W, occurs on the 35° water steering angle, and on a Q=45 m3/h water flow rate and on a 80 rpm turbine rotation. While the highest turbine efficiency, h=27 %, occurred on the Q=30 m3/h water flow rate, on a 60 rpm turbine rotation and on a water flow steering angle a=35°. The highest turbine torque, 3.1 Nm, occurs at Q=45 m3/h water flow rate at a maximum turbine braking and on a water steering angle a=35°.

A numerical analysis to study the effect of radius ratio and attachment angle on hybrid hydrokinetic turbine performance

The performance of a hybrid hydrokinetic turbine rotor under different operating conditions is investigated in this study. The effects of radius ratio and attachment angle on the power coefficient, self-starting capability and flow behavior around the turbine were simulated using commercially available software, ANSYS, with FLUENT as the solver. Realizable k-ε turbulence model has been used to solve the unsteady Reynolds-Averaged Navier-Stokes (URANS) equations. We compared the performance of a hybrid hydrokinetic turbine with the identically designed hybrid wind turbine under similar input power conditions. The hydrokinetic turbine rotor showed better performance than that of wind turbine rotor. The maximum values of coefficient of power (CP) and torque (CT) occur at attachment angles of 30° and 60° for a radius ratio of 0.2. At an attachment angle of 90°, fluctuations in CT were minimized.

The power extraction by flapping foil hydrokinetic turbine in swing arm mode

In the present study the power extraction capability by flapping foil hydrokinetic turbine is investigated. The heaving motion of the foil is considered in two different motion patterns including the simple linear translational motion and the rotation of swing arm on which the foil is mounted. The laminar and incompressible flow around a NACA0012 foil is conducted using Computational Fluid Dynamics (CFD) method. It is shown that the power extraction is possible and more desirable in the lower reduced frequencies. Additionally, the swing arm mode may increase the amount of extracted power and improve the performance of hydrokinetic turbine. Changes in kinematics of flapping foil alter the angle of attack profile and the local Reynolds number on the surface of the foil. These two sensitive changes influence on the sub-layer flow near to surface of the foil and make the vortex structure to be complex during flapping cycle. In the other words, in swing arm mode the vortex creation, growth, separation and shedding occur with an alternative pattern compared to simple mode. Finally, it is shown that the importance of the swing arm mode is in a certain range of swing arm lengths.

Modeling Hydrokinetic Turbine Performance in the Mississippi River

AbstractFree Flow Power has developed a renewable energy technology that can convert the kinetic energy flowing in a river to electricity without the use of dams. The company plans to install a specially made turbine directly into the flowing stream. This process, known as hydrokinetics, is an innovative approach that provides energy at a reliable and predictable rate as opposed to other intermittent renewable energy sources. There are currently two dozen hydrokinetic projects in the licensing process along the Mississippi River, which will account for 4,000 MW of power-generating capacity. Hydrokinetics could develop into a $1 billion a year industry.This article describes the modeling tool developed for Free Flow Power’s hydrokinetic sites along the Mississippi River. The performance models compare river velocity, power generation, reliability, maintenance costs, and finance options to establish a likely performance profile for a proposed site.These models calculate the expected returns for Mississippi River projects and can be used to perform a sensitivity analysis on all of the major variables for hydrokinetics. The unique aspect of this performance model is the incorporation of a reliability calculator, which estimates the lost revenue resulting from component failures. It can be used to develop the maintenance strategy for the array and to evaluate the total cost of reliability for components. The modeling tool described provides Free Flow Power with the ability to compare different design scenarios and quickly gives an estimate of a site’s performance.

A Simulation Study of Flow and Pressure Distribution Patterns in and around of Tandem Blade Rotor of Savonius (TBS) Hydrokinetic Turbine Model

Abstrac t—Th e performance of hydrokinetic turbines of Savonius using a Tandem Blade Savonius (TBS) rotor was studied. These were three types of TBS: Overlap (Type I), Symmetrically (Type II) and Convergence (Type III). Through a comprehensive bibliographical research, it is possible to identify the influenced parameters, and to show that the optimum efficiency of the Savonius rotor can be particularly improved their partition space between blade and tandem. This simulation shows the way of the flow characteristic and pressure distribution pattern in and around of the blade swept area. The results show that the convergence TBS (Type III) have a higher gap pressure between upstream and downstream, or they have best performance than other types.

Reliability analysis for hydrokinetic turbine blades

Reliability is an important element in the performance of hydrokinetic turbines. It is also a driving factor of the system lifetime cost. In this paper, we perform time-dependent reliability analysis for the blades of a river-based horizontal-axis hydrokinetic turbine. Based on the stochastic representation of the monthly river velocity and material strength, a limit-state function is established with the classical blade element momentum method. In the limit-state function, a failure is defined as the event when the flapwise bending moment exceeds the allowable moment that corresponds to the ultimate strength of the material. The upcrossing rate method is employed to calculate the time-dependent reliability of the hydrokinetic turbine blade over its design life period. The results indicate that setting a proper cut-out river velocity is important for the reliability of the hydrokinetic turbine blade.

Tests on ducted and bare helical and straight blade Darrieus hydrokinetic turbines

Despite much optimistic language on commercial websites, little data is available on actual performance of hydrokinetic turbines. This paper summarises the findings of a series of tests on several Darrieus type cross flow hydrokinetic turbines (HKTs). Although this type of hydrokinetic turbine (HKT) has some advantages over axial flow turbines, fixed pitch Darrieus HKTs also have some drawbacks, including inability to self-start under load, low efficiency and shaking. Variable pitch has been suggested to increase starting torque and efficiency, ducts to increase power output and helical blades to produce smooth torque. To assess each of these modifications, tests were conducted in Australia and Canada on HKTs with fixed and variable pitch straight blades, fixed helical blades, with and without a slatted diffuser, by mounting each turbine in front of a barge and motoring through still water at speeds ranging from less than 1 m/s up to 5 m/s. The diffuser increased the power output by a factor of 3 in one configuration but considerably less in others. A reason for this finding is suggested. The maximum coefficient of performance Cp of the fixed pitch straight blade and helical turbines without a diffuser ranged from about 0.25 at 1.5 m/s down to less than 0.1 at 5 m/s, while Cp for those with a diffuser ranged from about 0.45 down to about 0.3. Fixed blade turbines, both straight and helical, exhibited low starting torque, while variable pitch turbines started easily. Considerable differences in Cp were observed for the same turbine configuration at different speeds. The turbine with fixed pitch, straight blades was found to shake violently due to cyclical hydrodynamic forces on blades, while the helical and variable pitch turbines did not shake excessively. These findings suggest that variable pitch cross flow HKTs should be further investigated.

A numerical investigation into the effect of diffusers on the performance of hydro kinetic turbines using a validated momentum source turbine model

Kinetic hydropower involves the use of hydro turbines, submerged within existing currents for power generation. They are applicable to ocean and tidal currents, rivers, and human-made channels. This versatility gives them advantages over conventional hydropower, however they suffer from low power densities. This numerical study investigates the use of diffusers to enhance the performance and viability of kinetic hydro turbines. To simplify the problem, the turbine is modeled as a momentum source region, a strategy that is first validated against Betz theory. The diffuser configuration produces 3.1 times more power than the turbine with no diffuser. A scaling analysis also shows a turbine with a diffuser outperforms a larger size turbine with no diffuser.