Search Results (100)

This study investigates the downstream wake characteristics of a helical hydrokinetic turbine through combined experimental and numerical analyses. A four-bladed helical turbine with a 20 cm rotor diameter and blockage ratio of 53.57% was tested in an open water channel under a flow rate of 180 m³/h, corresponding to a Reynolds number of approximately 90 × 10³. Velocity measurements were collected at 13 downstream cross-sections using an Acoustic Doppler Velocimeter, with each point sampled repeatedly. Standard error analysis was applied to quantify measurement uncertainty. Complementary numerical simulations were conducted in ANSYS Fluent using a steady-state k-ω Shear Stress Transport (SST) turbulence model, with a mesh of 4.7 million elements and mesh independence confirmed. Velocity deficit and turbulence intensity were employed as primary parameters to characterize the wake structure, while the analysis also focused on the recovery of cross-sectional velocity profiles to validate the extent of wake influence. Experimental results revealed a maximum velocity deficit of over 40% in the near-wake region, which gradually decreased with downstream distance, while turbulence intensity exceeded 50% near the rotor and dropped below 10% beyond 4 m. In comparison, numerical findings showed a similar trend but with lower peak velocity deficits of 16.6%. The root mean square error (RMSE) and mean absolute error (MAE) between experimental and numerical mean velocity profiles were calculated as 0.04486 and 0.03241, respectively, demonstrating reasonable agreement between the datasets. Extended simulations up to 30 m indicated that flow profiles began to resemble ambient conditions around 18–20 m. The findings highlight the importance of accurately identifying the downstream distance at which the wake effect fully dissipates, as this is crucial for determining appropriate inter-turbine spacing. The study also discusses potential sources of discrepancies between experimental and numerical results, as well as the limitations of the modeling approach. Full article

This research investigates enhancing the performance of an Archimedes screw-type hydrokinetic turbine (ASHT). A 3D transient computational model employing the six degrees of freedom (6-DOF) methodology within the ANSYS Fluent software 2022 R1, was selected for this purpose. A central composite design (CCD) methodology was applied within the response surface methodology (RSM) to enhance the turbine’s power coefficient ($C_p$). Key independent factors, including blade length (L), blade inclination angle ($\gamma$), and external diameter ($D_e$), were systematically varied to determine their optimal values. The optimization process yielded a maximum $C_p$ of 0.337 for L, $\gamma$, and $D_e$ values of 168.921 mm, 51.341°, and 245.645 mm, respectively. Experimental validation was conducted in a hydraulic channel, yielding results that demonstrated a strong correlation with the numerical predictions. This research underscores the importance of geometric design optimization in improving the energy capture efficiency of the ASHT, contributing to its potential viability as a competitive renewable energy solution in the pre-commercial phase of development. Full article

This study investigated the performance of Savonius hydrokinetic turbine blades through three-dimensional computational fluid dynamics simulations conducted at a fixed tip speed ratio of 0.87. A multi-factor experimental design was employed to construct 45 V-shaped rotor blade models, systematically examining the effects of a V-angle (30–140°) and straight-edge length (0.24 L–0.62 L) on hydrodynamic performance, where L = 25.46 mm (the baseline length of the straight edge). The results indicate that, as the V-angle and the straight-edge length vary independently, the performance of each blade first increases and then decreases. At TSR = 0.87, the maximum power coefficient (C_P) of 0.2345 is achieved by the blade with a 70° V-Angle and a straight edge length of 0.335 L. Pressure and velocity field analyses reveal that appropriate geometric adjustments can optimize the high-pressure zone on the advancing blade and suppress negative torque on the returning blade, thereby increasing net output. The influence mechanisms of the V-angle and straight-edge length variations on blade performance were further explored and summarized through a comparative analysis of the vorticity characteristics. This study established a detailed performance dataset, providing theoretical and empirical support for V-shaped rotor blade design studies and offering engineering guidance for the effective use of low-flow hydropower. Full article

Optimizing vertical-axis hydrokinetic turbines is essential to enhance their energy conversion efficiency and structural reliability, particularly for decentralized renewable energy applications. This study focuses on identifying the most effective turbine design by evaluating the influence of three key parameters: aspect ratio ($AR$), solidity ($\sigma$), and the index of revolution (I). Specifically, the study considers Gorlov-type vertical-axis turbines, known for their helical design and favorable hydrodynamic characteristics. To achieve this, fifteen turbine configurations were analyzed using a combination of two methods: response surface methodology (RSM) and multi-criteria decision matrices. Both methods converged on the same optimal turbine model, characterized by an I of 0.1, a $\sigma$ of 0.40, and an $AR$ of 1.0, demonstrating superior energy efficiency and structural robustness, as the design achieved a power coefficient ($C_p$) of 40.8% at a tip speed ratio ($TSR$) of 1.01. The integration of numerical simulations and experimental validation provides comprehensive insights into turbine behavior, ensuring reliability in practical applications. These findings advance hydrokinetic energy technologies by identifying configurations that optimize both performance and manufacturability. Full article

Energy development based on renewable energy has gained widespread acceptance in society, especially in recent years. Among the initiatives currently being promoted are those promoted by higher education institutions that utilize available space on their campuses by configuring energy systems to incorporate renewable generation technologies. This study conducts a techno-economic analysis of a hybrid energy system that combines photovoltaic systems, wind turbines, hydrokinetic turbines, batteries, and fuel generators for the Center for Research, Innovation, and Technology Transfer of the Universidad Católica de Cuenca (UCACUE) in southern Ecuador. Using data collected on site, particularly from the CIITT campus meteorological station and recorded on the RESMUCC platform, the size of each renewable system configuration is optimized based on the three proposed energy control algorithms. The designs of the different configurations developed using the Homer Pro tool are then compared in terms of costs and energy generated. The results show that the system, which includes photovoltaic systems, wind turbines, hydrokinetic turbines, and fuel-powered generators, has the lowest cost, at USD 0.33/kWh. Full article

This review examines various methods for the design and optimization of horizontal-axis hydrokinetic turbines. A detailed analysis is presented of the results from numerical and experimental studies on small axial hydrokinetic turbines optimized through different methodologies. The influence of individual components of the flow passage on the turbine’s efficiency is emphasized. The energy performance of the studied turbines is compared with that of modern commercial hydrokinetic turbines. It is demonstrated that Computational Fluid Dynamics (CFD) can be used to optimize the geometry of the flow passage, achieving a higher power coefficient compared to commercial hydrokinetic turbines. All of this contributes to the future development of more efficient axial hydrokinetic turbines suitable for operation at lower flow velocities. Full article

Ocean energy represents a promising resource for renewable energy generation. Hydrokinetic turbines (HKTs) provide a sustainable method to extract energy from ocean currents. However, turbine efficiency remains limited, particularly in marine environments with low flow velocities. A parametric evaluation of blade configurations is conducted in this study to assess their effect on the power and torque performance of a double-stage drag-based Savonius HKT. Numerical simulations are conducted using the Unsteady Reynolds-Averaged Navier-Stokes (URANS) equations with the k-ω SST turbulence model. The numerical model is validated against published data, and analyses on mesh density, domain size, and time step are performed to ensure accuracy. Three blade configurations—(0°, 0°), (0°, 45°), and (0°, 90°) are evaluated under flow velocities of 0.6 m/s, 0.8 m/s, and 1.0 m/s. Results indicate that blade configuration significantly affects turbine performance. The (0°, 0°) configuration performs best at high flow velocity (1.0 m/s), while the (0°, 45°) setup achieves the highest efficiency at 0.6 m/s. The (0°, 90°) configuration performs the least effectively across all conditions. A similar performance trend is observed for the torque coefficient. This study recommends selecting blade configurations based on flow velocity, providing design guidance for double-stage HKTs operating in varying marine conditions. Full article

This paper presents an experimental investigation into the performance of a horizontal-axis turbine deployed in the Sinú River. The primary objective is to assess the turbine’s functionality under actual water flow conditions. The prototype is equipped with a rotor measuring 1.58 m in diameter, featuring three blades, which are specifically engineered to produce 1 kW of power at a flow velocity of 1.5 m/s. To evaluate the turbine’s efficiency, measurements of both the electrical power output and the kinetic energy present in the river flow were conducted. The findings reveal a power coefficient ($C_P$) of 0.4087 for the turbine. Before the integration of hydrokinetic technology can proceed, essential preliminary assessments must be undertaken, including a hydrokinetic energy resource evaluation. This process entails multiple stages of reconnaissance and prefeasibility studies to identify optimal locations along river courses for the technology’s deployment. Additionally, this work highlights the significant challenges associated with adapting hydrokinetic technology in developing nations, particularly in the context of Colombia. Full article

The growing demand for electricity in developing countries has called attention and interest to renewable energy sources to mitigate the adverse environmental effects caused by energy generation through fossil fuels. Among different renewable energy sources, such as photovoltaic, wind, and biomass, hydraulic energy represents an attractive solution to address the demand for electricity in rural areas of Colombia that are not connected to the electrical grid. In the current paper, the fluid–structure interaction (FSI) of a recently designed Vertical-Axis Hydrokinetic Turbine (VAHT) Straight-Bladed (SB) Darrieus-type, modified with symmetric winglets, was studied by implementing the sliding mesh method (SMM). By coupling with Computational Fluid Dynamics (CFD) numerical simulations, the FSI study demonstrated that the hydrodynamic loads obtained can cause potential fatigue damage in the blades of the Straight-Bladed (SB) Darrieus VAHT. Fatigue life was assessed using the stress–life (S-N) approach, and materials such as structural steel, short glass fiber reinforced composites (SGFRC), and high-performance polymers (HPP), such as PEEK, were studied as potential materials for the construction of the blades. FSI results showed that the biaxiality index (BI) provides a good understanding of the dominant stresses in the blades as the azimuth angle changes. It was also shown that structural steel and PEEK are good materials for the manufacturing of the blades, both from a fatigue resistance and modal perspective. Full article

Hydrokinetic turbines (HKTs) are a promising renewable energy source due to the consistency and high energy density in river and tidal resources. One of the primary barriers to the widespread adoption of HKT technologies is a high levelized cost of energy (LCOE). Considering the marine operating environment, the operation and maintenance costs are substantial. The power electronic converter, a key element in the electrical energy conversion system, is a common point of failure in direct-drive turbine applications—leading to increased maintenance efforts. This work presents a reinforcement learning (RL) method built within a quadratic feedback torque control framework to balance energy generation with power electronic device lifetime. The effectiveness of the RL-based control scheme is compared against a static baseline controller through two year-long tidal case studies. The results showed that the proposed method reduced cumulative damage on the device by upwards of 75% but reduced energy generation by up to 25.2%. Using a custom real-time cost estimation function that considers the sale of energy and an estimate of the costs associated with operating a device at a given temperature, it was found that the RL method can increase net income by up to 45.4% depending on the energy market conditions. Full article

In this paper, the aim is to optimise the hydrodynamic performance of the novel fin-ring horizontal axis hydrokinetic turbine (HAHK). The original unique fin-ring turbine is an unconventional marine current turbine that comprises seven concentric rings with 88 connecting cambered fins and a solid centre hub. To begin with, the hydrodynamic performance of the benchmark turbine is evaluated using CFD simulations and is validated against sea-test data available in the literature. Subsequently, three of the turbine design parameters, namely, the fins’ pitch angle, the fins’ camber length, and the fins’ aspect ratio, are optimised for maximum power generation. Further test simulations illustrated the existence of a laminar region of flow in the turbine flow field. The K-kL-ω transition-sensitive turbulence model is adopted to capture the influence of transition on the flow field with results compared against those of the fully turbulent K-ε turbulence model. A final fine-tuning in the turbine design is carried out by increasing the number of fins per ring in the outermost rings to further maximise the generated power. The turbine hydrodynamic performance is assessed by comparison against other conventional hydrokinetic turbines available in the literature. Very satisfactory results are obtained with an increase of about 35% in the turbine-generated C_P as compared to that of the benchmark turbine. The turbine performance compares very well with other conventional turbines, especially in terms of higher peak C_P values, wider operating TSR range, and less sensitivity to variations in the inflow current speeds. Full article

Seasonal velocity variations can significantly impact the total energy delivered to microgrids produced by river hydrokinetic turbines. These turbines typically use a diffuser to increase the velocity at the rotor section, adding weight and raising deployment costs. There is a need for practical solutions to improve the capacity factor of such turbines. Our solution involves using multiple turbine rotors that can be interchanged to match seasonal velocity changes, eliminating shrouds to simplify design and reduce costs. This solution requires turbines that are designed to have an easily interchanged rotor, which requires us to limit the rotor to a two-blade design to also lower costs. This approach adjusts the turbine power curve with different two-blade rotor sizes, enhancing the yearly capacity factor. BladeGen ANSYS Workbench is used to design three two-blade rotors for free stream velocities of 1.6, 2.2, and 2.8 m/s. For each turbine rotor, 3D simulation is applied to reduce aerodynamic losses and target a coefficient of performance of about 45%. Mechanical stress analyses assess the displacement and stress of the used composite materials. Numerical results show good agreement with experimental data, with rotor efficiencies ranging from 43% to 45% at a tip speed ratio of 4 and power output between 5.4 and 5.6 kW. Results show that rotor interchangeability significantly enhances the turbine capacity factor, increasing it from 52% to 92% by adapting to river seasonal velocity changes. Full article

Deep-sea exploration relies heavily on autonomous underwater vehicles (AUVs) for data acquisition, but their operational endurance is limited by battery constraints. The Archimedes spiral hydrokinetic turbine (ASHT), as a novel type of horizontal-axis hydrokinetic turbine, has emerged as a promising solution for the harnessing of localized energy in the deep sea to power AUVs. This study explores the application of winglets on an ASHT to enhance its performance through computational fluid dynamics (CFD). The analysis focuses on the effects of the winglet angle and height ratio on the power and thrust, as well as the pressure distribution and flow characteristics. The findings indicate that strategically designed winglets, particularly those with angles greater than 90° and larger height ratios, can significantly improve the ASHT’s performance. This enhancement can be attributed to the winglets’ capacity to effectively reduce tip loss and expand the turbine’s swept area, thereby enhancing power extraction. The optimal configuration, determined at a winglet angle of 135° and a height ratio of 12–14%, demonstrates significant enhancements, including a minimum increase of 12.0% in power efficiency compared to the original ASHT. However, the study also acknowledges potential challenges; winglets with larger angles and height ratios may lead to increased load fluctuations, which require careful structural considerations. This study provides valuable insights into the design and optimization of ASHTs for deep-sea power generation, thereby contributing to the advancement of sustainable energy solutions for AUVs. Full article

The vertical axis hydrokinetic turbine is increasingly being used as a renewable energy device to harness tidal energy. In coastal regions with low tidal flow velocities, vertical-axis hydrokinetic turbines often exhibit low energy conversion efficiency, limiting their engineering applications. However, research in this field lacks systematic reviews and reliable solutions for improving efficiency. The paper, based on the traditional vertical axis hydrokinetic turbines, utilized numerical calculations and experimental methods to investigate the effects of blade helicity and airfoil curvature on the energy conversion efficiency of vertical axis hydrokinetic turbines in low flow velocity conditions. Additionally, an improved vertical-axis turbine model is proposed to enhance energy conversion efficiency in low-flow environments. The results indicate that increasing the blade helical angle and airfoil curvature can better optimize the flow conditions around the turbine, significantly improving the energy conversion efficiency of vertical axis turbines. The airfoil blade with a 20% curvature performs best at blade angle, with its power coefficient curve reaching higher peak values at several azimuth angles. At this point, the maximum efficiency reaches 24.42%. Compared to the conventional straight-blade design, the improved turbine model exhibits 6.13% increase in average energy capture efficiency, 3.70% increase in average dynamic torque, and 11.1% improvement in self-starting performance. Comparative analysis reveals that vertical-axis helical blade turbines exhibit superior hydrodynamic performance under low-flow conditions, effectively overcoming the limitations of conventional straight-blade turbines, including poor self-starting capability and low efficiency. This research provides valuable insights into improving the performance of vertical-axis turbines in low-flow environments and suggests innovative solutions for optimizing turbine design. Full article

The work presents an analysis of the Gorlov helical turbine (GHT) design using both computational fluid dynamics (CFD) simulations and response surface methodology (RSM). The RSM method was applied to investigate the impact of three geometric factors on the turbine’s power coefficient (C_P): the number of blades (N), helix angle ($\gamma$), and aspect ratio (AR). Central composite design (CCD) was used for the design of experiments (DOE). For the CFD simulations, a three-dimensional computational domain was established in the Ansys Fluent software, version 2021R1 utilizing the k-$\omega$ SST turbulence model and the sliding mesh method to perform unsteady flow simulations. The objective function was to achieve the maximum C_P, which was obtained using a high-correlation quadratic mathematical model. Under the optimum conditions, where N, $\gamma$, and AR were 5, 78°, and 0.6, respectively, a C_P value of 0.3072 was achieved. The optimal turbine geometry was validated through experimental testing, and the C_P curve versus tip speed ratio (TSR) was determined and compared with the numerical results, which showed a strong correlation between the two sets of data. Full article