Hydrokinetic Turbine Research Articles

Physically based formula for the maximum scour depth induced by a propeller jet

In the last two decades, many studies have been dedicated to the employment of predictive formulas able to assess the maximum scour depth produced by propeller jets. Owing to the complexity of the phenomenon, most of the literature formulas were built on empirical arguments, making them susceptible to scale issues and not fully coherent with the physics underpinning the scouring problem. Recent studies exploited the phenomenological theory of turbulence and the paradigms of sediment incipient-motion theory to derive a predictive formula of the maximum equilibrium scour depth in different cases: scour produced by jet, scour at bridge piers, and scour downstream of hydrokinetic turbines. In the present study, using the same considerations of the aforementioned works, we propose a new model that allows the derivation of a predictive physically based formula that includes all the relevant parameters controlling the scouring process induced by the propeller rotation. The theory is validated at the laboratory scale with experimental published data: a good agreement between theoretical predictions and literature data is shown. The proposed design formula clearly indicates that, when tested against experimental data, it leads to lower scattering levels than those obtained with empirical literature formulas.

Dynamic characteristic studies of novel flexible flip-type Savonius hydrokinetic turbine

Savonius turbine can be considered for power extraction device which extracts power from all water flowing areas like tidal, river, wave, and open channel. Savonius is one of the simplest turbines and equipped with easy fabrication and installation. In order to improve the power coefficient, the flexible flips were attached with 0.2 overlap Savonius. The experimental investigations were carried out by varying the flip variables such as flip radius (R34, R42, and R62), secondary overlap (0.53, 0.93, and 1.33) and flip oscillation limit (a-b, a-c, and a-d) at a constant water velocity of 0.8 m/s in the laboratory water channel. Experimental results shown that maximum power coefficient (Cp) of 0.116 obtained in 0.53 flip overlap, 42 mm radius and a-c oscillation limit (0.53OL R42 a-c) configuration which is relatively a higher value than the 0OL conventional Savonius Cp of 0.105.

Performance investigations of hybrid hydrokinetic turbine rotor with different system and operating parameters

Performance investigations of hybrid hydrokinetic turbine rotor with different system and operating parameters

The Influence of Deflector on the Performance of Cross-Flow Savonius Turbine

Several factors, including the accessibility of energy sources, influence the movement of human activities in this era. However, humans still rely on fossil energy sources. For example, petroleum is non-renewable and can pollute the environment. As a result, researchers have recently been competing to produce various forms of using renewable energy sources. Ocean current energy is one of Indonesia's greatest energy potentials and a hydrokinetic turbine is a device that can harness it. Due to its ability to run on low-speed currents, the vertical-type Savonius turbine has been developed by numerous researchers up until this point. However, there has not yet to be much advancement in the cross-flow type Savonius turbine. The turbine's performance is investigated in this study by adding a flow deflector because the water flow that propels the returning blade is diverted and intensifies the advancing blade flow. Computational Fluid Dynamics (CFD) software has been used to conduct the analysis. The deflector has been added, and the results have showed an average performance improvement of 12% in overall variations. The maximum Cp of 0.299 has been achieved with a deflector configuration angle of 42° at a TSR of 0.74.

Multi-Array Design for Hydrokinetic Turbines in Hydropower Canals

The design of hydrokinetic plants in hydropower canals involves the choice of the array layout, rotor geometry, turbine spacing, and array spacing, and necessitates the control of the resultant backwater to avoid upstream flooding hazards. Several works in the literature have shown that array power optimization is feasible with small spacings between the arrays, disregarding the limitation in the power output induced by backwater upstream. In this study, a 1-D channel model with a Double Multiple Streamtube code and wake sub-models are integrated to predict an array layout that will maximize the array power. The outputs of the conducted sensitivity analysis confirm that this design enabled improved power conversion with closely spaced turbines and largely spaced arrays, thus allowing for a partial recovery of the total head variation for a new array deployed upstream. In addition to the quantitative assessment of the mechanical power converted, the tool enables depth control from the downstream undisturbed flow station to the backwater exhaustion far upstream, thereby increasing its flexibility. Furthermore, it overcomes the limitations of actuator disc models by considering rotor’s fluid dynamic losses. The results show that power output linearly scales for a limited number of arrays (≤5), whilst the variation in water depth variation follows a power law from the most downstream array towards upstream, regardless of the plant size. Finally, the maximum upstream inflow depth is demonstrated to become asymptotic for large multi-array plants under ideal conditions.

Energy Conveyor Belt—A Detailed Analysis of a New Type of Hydrokinetic Device

Renewable energy technologies can help us combat climate change and hydrokinetic energy conversion systems could play a major role. The simplicity of hydrokinetic devices helps us to exploit renewable sources, especially in remote locations, which is not possible with conventional methods. A new type of hydrokinetic device called the Energy Conveyor Belt was designed, which works on the concept of conveyor belt technology. Numerical simulations are performed on the design of the Energy Conveyor Belt with Ansys FLUENT to optimize its performance. Some of the optimized models produced a maximum power slightly above 1 kW. The numerical results are then compared to the experimental results of other hydrokinetic turbines. The compactness and flexibility of the design give the Energy Conveyor Belt an advantage over other hydrokinetic devices in regions with fluctuating water levels. Further research has to be undertaken into cascading systems to increase the overall power generated by the system.

Numerical investigation on the performance of an innovative Airfoil-Bladed Savonius Hydrokinetic Turbine (ABSHKT) with deflector

Numerical investigation on the performance of an innovative Airfoil-Bladed Savonius Hydrokinetic Turbine (ABSHKT) with deflector

Flexible blades to improve Darrieus turbine performance and reduce cost

Low cost “sailwing” aerofoils of flexible nylon mounted between a rigid leading edge of circular cross section and a rigid flat trailing edge were investigated in the 1970s and 1980s. Wind tunnel measurements of lift and drag of these aerofoils over the full range of angles of attack were published, but no predictions were made for a complete wind turbine incorporating them. Another paper stated that a sailwing turbine with aerofoils incorporating pivoting aerodynamic profile leading edges was found to exert considerable starting torque. In the present paper, published lift and drag data have been used to predict the performance of a small Darrieus hydrokinetic or wind turbine with sailwing aerofoils, using a standard multiple streamtube model over the full range of tip-speed ratios (TSRs) from 0.5 to 3. To provide a fair comparison, this method is also used to predict the performance of the turbine with symmetrical NACA0018 and cambered Gö420 blade profiles. At all examined TSRs, average torque and power of the turbine with flexible blades are higher than the turbines with rigid blades. For instance, at TSR of 2.5, the flexible blade turbine achieved 55 % and 165 % higher average torque than the turbines with symmetrical and cambered blades, respectively. This finding is attributed to the fact that the flexible blade camber reverses with reversing incidence, producing high lift coefficients at low incidence. Drag is higher for the flexible aerofoil, probably due to separation at the circular cross section leading edge, and measures are suggested to improve this. The flexible aerofoils are very cheap and simple to fabricate, making them an attractive option for affordable hydrokinetic turbines.

Determinations and performance investigations of hybrid composite properties for hydrokinetic turbine blades

In this experimental study, hybrid composite properties for hydrokinetic turbine blades were determined, and its performance was examined. The reinforcements included glass fiber, treated and untreated highland bamboo fiber, reinforced polyester-based composites and their hybrid composites, as well as row bamboo (bamboo culm). The row bamboo was prepared on the bamboo culm’s outer surface to get rid of any leftovers, before cutting in accordance with the specimen test standards. In order to make hybrid composite materials, polyester resin was mixed with fibers in the proportions of bamboo fiber/glass fiber (50%/50%), and fiber/matrix (30%/70%). The composite containing glass fiber has a flexural strength that is 12% and 21% higher than materials reinforced with alkali-treated and untreated highland bamboo fiber reinforced composites respectively. The alkali treatment of highland bamboo fiber improved its physical-mechanical properties, making it suitable for use different application. Alkaline treatment boosts the composite’s tensile and compressive strength by 37% and 3.4% for composite reinforced with untreated bamboo fiber, and 10.2% and 23.8% for composite reinforced with glass fiber, respectively. The fiber density of highland bamboo was increased by removing less dense non-cellulosic components (hemicellulose and lignin). However, the fiber’s moisture absorption is the main issue in using it in a composite that works submerged in water. This study investigated whether incorporating glass fiber in highland bamboo-glass fiber polyester hybrid composite reduces the composite material’s water uptake. A reduction was found, however, the density was increased. It is challenging to employ row bamboo for the construction of hydrokinetic turbine blades as water ingress of the composite must be avoided even in the presence of erosion caused by cavitation and impact with foreign bodies in the water.

Effect of waves on leading edge of modified Savonius rotor blades

The blade profile of the Savonius hydrokinetic turbine has a significant effect on the performance of the rotor. Many previous numerical and experimental research suggested different blade profiles. In the present work, a similar recommended blade profile selected, and two different configurations were namely, i. sharp edge outside and ii. sharp edge inside. The results were compared with the conventional rotor. The investigation concludes that a sharp edge outside delivers better performance than a sharp edge inside and traditional rotor. The best configuration was further tested for different wave amplitudes, i.e. P/λ. The waves on the blades further enhance the performance of the rotor. Compared to a previously proposed design, the present modified configuration indicated a 31% improvement in power coefficient and a 37% improvement compared to the conventional design.

Deep Learning-Based Prediction of Unsteady Reynolds-Averaged Navier-Stokes Solutions for Vertical-Axis Turbines

The following study investigates the effectiveness of a deep learning-based method for predicting the flow field and flow-driven rotation of a vertical-axis hydrokinetic turbine operating in previously unseen free-stream velocities. A Convolutional Neural Network (CNN) is trained and tested using the solutions of five two-dimensional (2-D), foil-resolved Unsteady Reynolds-Averaged Navier-Stokes (URANS) simulations, with free-stream velocities of 1.0, 1.5, 2.0, 2.5, and 3.0 m/s. Based on the boundary conditions of free-stream velocity and rotor position, the flow fields of x-velocity, y-velocity, pressure, and turbulent viscosity are inferred, in addition to the angular velocity of the rotor. Three trained CNN models are developed to evaluate the effects of (1) the dimensions of the training data, and (2) the number of simulations used as training cases. Reducing data dimensions was found to diminish mean relative error in predictions of velocity and turbulent viscosity, while increasing it in predictions of pressure and angular velocity. Increasing the number of training cases from two to three was found to reduce relative error for all predicted unknowns. With the best achieved CNN model, the variables of x-velocity, y-velocity, pressure, turbulent viscosity, and angular velocity were inferred with mean relative errors of 6.93%, 9.82%, 10.7%, 7.48%, and 0.817%, respectively.

Technoeconomic Analysis and Optimization of Hybrid Solar-Wind-Hydrodiesel Renewable Energy Systems Using Two Dispatch Strategies

Sustainable generation is impacted by the adoption of renewable energy, the growth of energy markets, and economic strategies. This paper offers a sustainable strategy and a technoeconomic analysis of off-grid hybrid energy systems (HES) in remote islands of Iran, including Lavan, Larak, and Failaka, utilizing PV module, wind turbine, and hydrokinetic turbines. Hourly wind speed, solar irradiation, and hydrovelocity have been implemented under load following (LF) and cycle charging (CC) dispatch strategies in order to ascertain the most appropriate systems. Lavan Island achieves the winning HES with a CC dispatch strategy, which consists of 3 hydroelectric turbines, 1 wind turbine, 349 kW of solar power, 150 kW of generator power, 316 kWh of batteries, and 287 kW of the converter. This ideal HES, which generates a consistent generation profile and reasonable net present cost (NPC) and cost of energy (COE) of M0.160$ and $0.013 kWh, respectively, can be practically attained in these areas. LF-controlled optimal solutions use less fuel than CC-based ones, leading to a higher share of renewable energy. Compared to Larak and Lavan, the CC- and LF-controlled options on Failaka Island generate cleaner electricity with emissions that are 57% and 44% lower. Regarding the ability to recoup the project’s initial investment costs, long-term energy production would be more financially viable than short-term. Short-term projects with higher financial uncertainty due to the salvage cost should use the CC method.

Experimental and multiphase modeling of small vertical-axis hydrokinetic turbine with free-surface variations

Vertical-axis hydrokinetic turbines are promising option to harness the low velocity currents. However, limited investigations have been carried out considering the interactions between the turbine rotor and the channel section, including the free-surface. Thus, a vertical-axis turbine model has been designed and manufactured, to be tested in an open channel. Also, a three-dimensional multiphase simulation has been carried out, using the volume of fluid (VOF) model, to capture the air–water interface and to investigate the free-surface variations effects on the turbine output. Experimentally, the turbine model has been characterized under different flow conditions and free-surface levels. The peak power coefficients are found to increase with the upstream velocity. This effect is directly linked to the blockage ratio and the Froude number. A reasonably good match has been found between the experimental and the numerical results. The VOF model is able to simulate the free-surface longitudinal variations, and the effect of the turbine blockage of the channel. The velocity field and the pressure coefficient distribution, around the turbine rotor, have been studied and correlated with the free-surface variations from upstream to downstream of the turbine. Finally, the vortex street generated by the blade–plate interaction has been analyzed.

ЭЛЕКТРОСНАБЖЕНИЕ МАЛОМОЩНЫХ ПОТРЕБИТЕЛЕЙ, УСТАНОВЛЕННЫХ НА НЕФТЕПРОВОДАХ В УДАЛЕННЫХ РАЙОНАХ КРАЙНЕГО СЕВЕРА

Relevance The power outage in remote and inaccessible areas of the Far North can have serious consequences, including technological and ecological disasters, fires, explosions, water pollution, impact on human health, and economic losses. To ensure power supply in harsh climate areas, various autonomous power sources are being considered, including a hydrokinetic turbine installed inside the pipeline, which converts the kinetic energy of the flow into electricity using an electromechanical generator. Object of study The research focuses on the efficient power supply of oil and gas pipeline consumers in remote and inaccessible areas of the Far North. A small-scale hydraulic power station is installed on the bypass line of the oil pipeline. Aim of research The main aim of the study is to assess the feasibility of using a hydrokinetic turbine inside the pipeline for efficient power supply to linear consumers of oil and gas pipelines in remote areas. Research methods During the research, an analysis of the field of existing small-scale power plants was carried out to determine the most promising and efficient approaches to electricity generation. Additionally, a theoretical solution in the form of a hydrokinetic turbine for electricity generation was proposed. Results The results and significance of the research propose the hydrokinetic turbine installed inside the pipeline as an autonomous power source for efficient power supply to consumers. A hybrid power station model is suggested, combining the hydrokinetic turbine with other energy sources to ensure uninterrupted power supply in remote areas. The obtained results have practical significance for the energy provision of oil and gas pipelines in remote and inaccessible areas of the Far North. A new approach to power supply is proposed, which, upon implementation of the developed equipment, can ensure uninterrupted operation of the energy module of the technological equipment installed on the pipelines and help prevent technological disasters and economic losses.

Experimental study of the flow induced by an axial hydrokinetic turbine

The renewable energy policy strongly encourages the use of all renewable sources of energy. The authors started to develop a new hydrokinetic turbine to be implemented in small rivers or water channels with a low investment cost. This paper presents velocity map distribution around a hydrokinetic turbine prototype. Experimental measurements were performed using a Particle Image Velocimetry system in a water channel, while the water velocity and turbine rotation speed were variated. Images are presented in the same rotor position and the rotational flow is captured downstream of the blades, at different turbine operating modes. This paper is part of a larger study on developing an innovative axial hydrokinetic turbine. The resulting velocity distribution will be used to validate the numerical model.

Optimization of Blade Geometry of Savonius Hydrokinetic Turbine Based on Genetic Algorithm

Optimization of Blade Geometry of Savonius Hydrokinetic Turbine Based on Genetic Algorithm

A deep-water in-situ power generation system based on chain-driven hydrokinetic turbine

Harnessing hydrokinetic energy from deep water to increase the operation periods of autonomous underwater vehicles and underwater moored platforms has received considerable attention in recent years. Hydrokinetic turbines should have a reliable startup performance for deployment in deep water with a prevailing average current speed of 0.5 m/s. In the present study, a deep-water in-situ power generation system based on a novel chain-driven hydrokinetic turbine is proposed for such low-speed current application. A numerical simulation was performed on the proposed turbine to investigate its hydrodynamic performance at different initial setting positions and tip speed ratios. No static dead band exists in the operation of the turbine, indicating a superior self-starting advantage over traditional drag-type turbines. Multi-objective optimization was performed on the proposed turbine to improve its power coefficient and startup performance. Compared with the initial design (Cp = 0.234, Ct,s = 0.520), the Cp and Ct,s in the Pareto front range from 0.103 to 0.325 and 0.565 to 0.712, respectively. All-process simulation was conducted based on Simulink to estimate the power supply capacity of a deep-water in-situ power generation system using the optimal chain-driven hydrokinetic turbine. The result shows that this system can generate the electricity at 218.45 Wh/day in the deep-water location with an average current speed of 0.334 m/s, providing enough energy to the power units of autonomous underwater vehicles.

Experimental study on the characterization of the self-starting capability of a single and double-stage Savonius turbine

The Savonius hydrokinetic turbine is a viable alternative for rural electrification despite its relatively low power coefficient. There are many ways to improve power performance, including the use of multiple-stage turbines. Although many studies have investigated the effects of multi-staging, few have captured their effect on three performance parameters combined: power efficiency, flow structure, and self-starting capability. Therefore, the current study explored and analyzed the extent of these parameters using a multi-stage conventional Savonius turbine in a wind tunnel facility with a varying flow speed of 5 m/s to 9 m/s. The findings suggested that adding a stage increased the power coefficient to a maximum of 138% at 5 m/s, but reached a plateau as the wind speed increased to 9 m/s. The double-stage was discovered to reduce the self-starting speed of the turbine at all rotor angles for self-starting capabilities. The coefficient of static torque results indicated that the maximum static torque for the single and double-stage configurations occurred at 45° and 45°/135° rotor angles, respectively. The qualitative study revealed that the double-stage turbine has a larger wake size at higher wind speeds, resulting in a reduced wake intensity at the rear side of the rotor. The reduced torque variation caused by the additional stage has improved the overall performance of the turbine, making the double-stage configuration more preferable than the single-stage, particularly for low speed, high depth, and narrow river applications.

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%.

Backwater assessment for the energy conversion through hydrokinetic turbines in subcritical prismatic canals

Hydrokinetic turbines exploit partially the total head variation created in natural and artificial waterways. In subcritical flows, the sum of the energy harvested mechanically and the energy dissipated by fluid-dynamic losses and viscous friction is balanced through a backwater extending far upstream. The latter depends on the turbine operating condition and, thus, on the thrust force generated.Only the downstream momentum is known, whilst upstream momentum and turbine thrust force are undetermined. To solve this problem, a method is developed to update the inflow factor for a single turbine, thus achieving a single physical solution. Froude number and blockage ratio are updated at each iteration and are used as independent variables for solving the turbine model. According to the actual canal geometry, a specific continuity equation allows to infer the backwater depth from the inflow factor. Hence, this method can be integrated with confined BEM and DMS models to extend the capability of the simulation tool.Experimental data of inflow depth are used to validate this model for single rotors in a subcritical environment, whilst its extension allows the assessment of turbine arrays in artificial canals exploited for hydropower purposes.