Horizontal Axis Marine Current Turbine Research Articles

Predictions of the Hydrodynamic Performance of Horizontal Axis Marine Current Turbines Using a Panel Method Program

The marine current turbine is the mechanical device that captures the kinetic energy of marine current to generate electrical power. This paper presents the application of an academic panel code based on potential flow theory for the analysis of marine current turbines. The aim of this work is also to analyze the effect of the addition of a duct on the hydrodynamic performance of the turbine. The numerical results show that the addition of duct improves significantly the efficiency of the turbine.

Collective pitch for horizontal axis marine current turbine

Marine current turbines need to operate at sea for a long time, facing a changeable marine environment and harsh working conditions, and are prone to component failures. Therefore, it is necessary to use efficient and reliable pitch technology to achieve unattended, stable, month-long operation corresponding to lunar rhythm, enhance redundancy and reliability, and extend the service life of the turbine. A hydraulic collective pitch system was designed for a 120 kW horizontal-axis marine current turbine, and a pitch angle redundant measurement scheme was proposed to measure the pitch angle directly and indirectly. Pitch control strategies were designed, including pitch-assisted launch, power-staged control, and two-way current energy harvesting, based on marine current reversal determination. A joint simulation was carried out using AMESim and MATLAB/Simulink software, and a sea test was performed based on the test platform. The simulation and sea test results demonstrated that the designed pitch system operates normally, and the pitch strategies can reduce pitch system loss and achieve month-long reliability.

Design and on-site implementation of an off-grid marine current powered hydrogen production system

In this work, an off-grid hydrogen production system powered by marine current energy was studied, which employed a horizontal axis marine current turbine (HAMCT) and a polymer electrolyte membrane (PEM) electrolyzer fed with ultrapure water. The fluid kinetic energy of the marine current will be captured by the turbine and finally stored as hydrogen energy through the electrolysis reaction in the electrolyzer. It is important to fully understand the characteristics of the electrolyzer for the stable and efficient operation of the system. Here, a dynamic model of PEM electrolyzers was developed, which is based on the Hammerstein structure. The particle swarm optimization (PSO) method and the least squares method were used to fit the static part and the dynamic part of the model, respectively. The experimental validation shows enough precision for engineering applications and the ability to characterize the transient behavior of the electrolyzer. Faraday’s efficiency of the stack was modeled using an empirical formula. The simulation of the proposed system was then carried out using the measured current velocity data as input. The results demonstrate that the system achieved the designed operating performance with the power coefficient of 0.42 and the estimated average energy conversion efficiency from marine current-to-hydrogen of 16.4%. Then, the sea trial was conducted in Zhoushan Archipelago. The power coefficient and the average energy conversion efficiency were found to be 0.35 and 11.9% respectively, with a decrease compared to the simulated results, which was attributed to the idealization of the simulation model and the degradation of the PEM electrolyzer. The performance degradation of the PEM electrolyzer throughout experiments and its effects were discussed. The principle and feasibility of the marine current-hydrogen system were successfully demonstrated.

Influences of Geometrical Parameters of Upstream Deflector on Performance of a H-Type Vertical Axis Marine Current Turbine

Marine current power is a kind of renewable energy that has attracted increasing attention because of its abundant reserves, high predictability, and consistency. A marine current turbine is a large rotating device that converts the kinetic energy of the marine current into mechanical energy. As a straight-bladed vertical axis marine current turbine (VAMCT) has a square or rectangular cross-section, it can thus have a larger swept area than that of horizontal axis marine current turbines (HAMCT) for a given diameter, and also have good adaptability in shallow water where the turbine size is limited by both width and depth of a channel. However, the low energy utilization efficiency of the VAMCT is the main bottleneck that restricts its application. In this paper, two-dimensional numerical simulations were performed to investigate the effectiveness of an upstream deflector on improving performance of the straight-bladed (H-type) marine current turbine. The effects of various key geometrical parameters of the deflector including position, length, and installation angle on the hydrodynamic characteristics of the VAMCT were then systematically analyzed in order to explore the mechanism underlying the interaction between the deflector and rotor of a VAMCT. As a result, the optimal combination of geometrical parameters of the deflector by which the maximum energy utilization efficiency was achieved was a 13.37% increment compared to that of the original VAMCT. The results of this work show the feasibility of the deflector as a potential choice for improving the energy harvesting performance of a VAMCT with simple structure and easy implementation.

Improved control strategy of dual star permanent magnet synchronous generator based tidal turbine system using sensorless field oriented control and direct power control techniques

ABSTRACT This paper presents a grid-connected tidal stream system with a focus on the reduction of the number of sensors needed by the control scheme. The electromechanical converter is a dual star permanent magnet synchronous generator (DS-PMSG) driven by a horizontal axis marine current turbine (HA-MCT). The generator is controlled via the field-oriented control (FOC) strategy, the speed and the position of the rotor are estimated using an extended Kalman filter (EKF), and the speed is regulated using a fuzzy logic controller. The grid side converter (GSC) consist of a two level voltage source inverter controlled by a virtual flux-based direct power control strategy (VF-DPC), and the current is filtered using an LCL filter. The system is simulated using Matlab/Simulink environment, the simulation results show the efficacy of the proposed control scheme, fuzzy speed regulator, and the EKF estimator, where relative mean error (MRE) of speed tracking is only 0.004, and MRE of estimated speed is as low as 7.3e-6, but a low rotor position estimation error of 1.76 degrees can be observed, however, the high number of pole pairs of the generator amplifies the effect of position error, causing divergences between the controlled dq currents seen by the control scheme and the real dq current that flows in the machine, and a decrease of system effeciency; however, the stability is not affected.

Marine current energy assessment and the hydrodynamic design of the hydrokinetic turbine for the Moroccan Mediterranean Coast

Generating electricity through renewable energies is growing increasingly to reduce the huge demand on electricity and the impact of fossil energies on the environment, the most common sources forms used are: the wind, the sun, the photovoltaic and the thermal, without forgetting hydropower by the bays of dams. Fortunately, 70% of our planet is covered by the seas and oceans, this area constitutes a huge potential for electricity production to be exploited. The scientific advances of recent years allow a better exploitation of these resources especially the marine current due to its reliability and predictability. The marine current energy is extracted using a hydrokinetic turbine (HKT) which transform the kinetic energy of water into an electrical energy. The exploitation of this resource needs in the first step the assessment of marine currents in the study area for implementing the HKT, and the second step is designing an adequate technology. The main goal of this study is the assessment of the marine current resource on the Moroccan Mediterranean coast to evaluate the suitable area to implement the HKT, and to determine the marine current speed intensities at different depths. As well as, to estimate an average potential existing in the site. Moreover, we will conduct a study based on the results of the assessment that was made to design a horizontal axis marine current turbine (HAMCT). Two hydrofoil profile were considered to design a HAMCT using the Blade Element Theory (BEM) and calculating their performances adapted to the site conditions Naca4415 and s8052. In addition, a comparison was made between this two HAMCT hydrofoil profile for deciding the best one for implementing in the studied area.

Experiments on the hydrodynamic performance of horizontal axis marine current turbines to confirm computational predictions

Experiments on the hydrodynamic performance of horizontal axis marine current turbines to confirm computational predictions

Two-Way Fluid–Solid Interaction Analysis for a Horizontal Axis Marine Current Turbine with LES

Operating in the harsh marine environment, fluctuating loads due to the surrounding turbulence are important for fatigue analysis of marine current turbines (MCTs). The large eddy simulation (LES) method was implemented to analyze the two-way fluid–solid interaction (FSI) for an MCT. The objective was to afford insights into the hydrodynamics near the rotor and in the wake, the deformation of rotor blades, and the interaction between the solid and fluid field. The numerical fluid simulation results showed good agreement with the experimental data and the influence of the support on the power coefficient and blade vibration. The impact of the blade displacement on the MCT performance was quantitatively analyzed. Besides the root, the highest stress was located near the middle of the blade. The findings can inform the design of MCTs for enhancing robustness and survivability.

Optimization of a horizontal axis marine current turbine via surrogate models

Flow through a scaled horizontal axis marine current turbine was numerically simulated after validation and the turbine design was optimized. The computational fluid dynamics (CFD) code Ansys-CFX 16.1 for numerical modeling, an in-house blade element momentum (BEM) code for analytical modeling and an in-house surrogate-based optimization (SBO) code were used to find an optimal turbine design. The blade-pitch angle (o) and the number of rotor blades (NR) were taken as design variables. A single objective optimization approach was utilized in the present work. The defined objective function was the turbine\'s power coefficient (Cp). A 3x3 full-factorial sampling technique was used to define the sample space. This sampling technique gave different turbine designs, which were further evaluated for the objective function by solving the Reynolds-Averaged Navier–Stokes equations (RANS). Finally, the SBO technique with search algorithm produced an optimal design. It is found that the optimal design has improved the objective function by 26.5%. This article presents the solution approach, analysis of the turbine flow field and the predictability of various surrogate based techniques.

A performance analysis of tidal turbine conversion system based on control strategies

Energy efficient generation from renewable energy sources is of major concern nowadays. A horizontal axis marine current turbine (HAMCT) of diameter 1.9 m is modelled using the blade element momentum (BEM) scheme and the turbine output parameters are given as an input to the electrical system for a tip speed ratio (TSR) of 5 and a power coefficient of 0.4. The design aspects of a buck-boost converter with proportional integral (PI) and sliding mode controller (SMC) is investigated for HAMCT system, with the highest power output of about 15.6 kW for a water velocity of 3 m/s. A comparison between PI controller and SMC are analyzed for the tidal turbine conversion system to obtain the desired output voltage with high efficiency is discussed here. The dynamic variation on load side to be controlled with dual loop controller to regulate the output voltage and to optimize the input current. In this paper performance and resemblance of control techniques which include sliding mode controller and PI controller are analysed with step and bode plot response. The system is designed for an output voltage range of 0.38 kV to 2.4 kV which is suitable for DC microgrids. The performance of HAMCT coupled with PMSG and the power converter with a controller is modelled and designed under MATLAB/SIMULINK environment.

Hydrodynamic Assessment of a Dual-Rotor Horizontal Axis Marine Current Turbine

The hydrodynamic performance of a dual-rotor horizontal axis marine turbine (HAMCT) is investigated for the power gain in operating the rear rotor without blade-pitch control. This kind of turbine can be advantageous for a rectilinear tidal current of reversing directions, where each rotor blade is optimally fixed-pitched towards its upstream velocity. The blade element momentum (BEM) method is coupled with the Park wake model. A generic three-blade turbine is shown to gain up to 20% in the coefficient of power CP as relative to the front rotor CP when operating the rear rotor at the same tip speed ratio (TSR) as the front one, gaining overall CP up to 0.55. Analytic model is derived to backup the estimate of power gain. Plots for turbine performance variation with TSR and profile hydrodynamic efficiency are given, and analysed for lab and small-medium size turbines.

Flow Regime Algorithm (FRA): a physics-based meta-heuristics algorithm

In this research study, a physics-based optimization algorithm, namely Flow Regime Algorithm (FRA) is proposed. The main sources of inspiration are classical fluid mechanics and flow regimes. The flow regime usually is being divided into two categories which are laminar and turbulent flows. Reynolds number is the parameter which defines that the flow regime is laminar or turbulent. In this research study, a similar number to Reynolds has been defined which indicates the search type (global or local) of the algorithm and is called search type factor. For the purpose of developing the local and global searches equations, the concept of boundary layer in fluid mechanics has been used. The performance of the proposed algorithm has been evaluated using 26 benchmark functions and has been compared with seven popular and well-known algorithms which are simulated annealing, particle swarm optimization, firefly algorithm, cuckoo search, flower pollination algorithm, krill herd and monarch butterfly. Finally, the heat wheel optimization problem and horizontal axis marine current turbine (tidal turbine) problem, which are real-case engineering problems, have been solved using FRA. The results indicated that FRA can be a great candidate in solving complex engineering problems.

Marine Turbine Hydrodynamics by a Boundary Element Method with Viscous Flow Correction

A computational methodology for the hydrodynamic analysis of horizontal axis marine current turbines is presented. The approach is based on a boundary integral equation method for inviscid flows originally developed for marine propellers and adapted here to describe the flow features that characterize hydrokinetic turbines. For this purpose, semi-analytical trailing wake and viscous flow correction models are introduced. A validation study is performed by comparing hydrodynamic performance predictions with two experimental test cases and with results from other numerical models in the literature. The capability of the proposed methodology to correctly describe turbine thrust and power over a wide range of operating conditions is discussed. Viscosity effects associated to blade flow separation and stall are taken into account and predicted thrust and power are comparable with results of blade element methods that are largely used in the design of marine current turbines. The accuracy of numerical predictions tends to reduce in cases where turbine blades operate in off-design conditions.

Assessment of Energy Production Potential from Tidal Stream Currents in Morocco

Energy extracted from the ocean can provide a source of regular and foreseeable electrical production at higher energy densities than any other renewable energy resource. The marine current resource is potentially great and is focused in several sites around the world. The knowledge of the energy potential, its constraints and availability are all prerequisites to determine the possibilities for the implementation of infrastructure to produce energy. They are also required to anticipate the structuring of energy routes and to respond to increasing technological needs. Several Moroccan regions want to take advantage by their coastal domain and play a role in the development of the tidal energy sector. They also want to benefit from the associated economic advantages knowing that the Mediterranean coast length is 550 km and the Atlantic length is 3000 km, respectively. The Copernicus Marine Service ocean products provide key input for such technologies, as they can be employed to help evaluate the accessible ocean energy devices and choose the most attractive sites to exploit the tidal energy projects in Morocco. The goal of this research was to evaluate and analyze the tidal marine current resource at the sites which are potentially suitable for the installation of Horizontal Axis Marine Current Turbines in Morocco. Distributions of available power of tidal energy in the Moroccan region are provided, and three possible areas are suggested for installing tidal energy conversion systems.

Performance of a horizontal axis marine current turbine– A comprehensive evaluation using experimental, numerical, and theoretical approaches

This study provides a comprehensive assessment of a 2 bladed horizontal axis marine current turbine using experiments on two scale models, compared to both theoretical and numerical models and previous experiments in other facilities. The experiments were performed in a towing tank and a circulating water channel on rotors of 500 mm and 800 mm diameter. The effect of model scale was investigated together with facility bias. The impact of facility bias on the performance assessment was found to be induced from blockage and the presence of a shear flow velocity profile in the circulating water channel. A BEM model was modified to consider shear velocity profile in the performance calculations. No significant changes were seen in the BEM model results by inserting the shear flow in the code. In addition, the QBlade software was employed as a tool to investigate the effect of Reynolds number. It can provide the performance outcomes for a range in which the results are sensitive to Reynolds number. A RANS CFD model was provided which simulates the turbine in steady flow conditions. The theoretical, numerical and physical models were used to study the effect of scaling. The BEM and CFD model both had good agreement with the experimental results, which provides a strong platform for more detailed study on the HAMCT hydrodynamics.

Asymmetric Load Control Method for Individual Pitch of Horizontal Axis Marine Current Turbine

Asymmetric Load Control Method for Individual Pitch of Horizontal Axis Marine Current Turbine

Numerical assessment of a horizontal axis marine current turbine performance

Horizontal axis marine current turbine is a viable device which can harness kinetic energy from ocean currents. It is the closest concept to be commercialised among other marine turbines. Literature shows that computational fluid dynamics (CFD) models can accurately simulate turbine performance provided appropriate numerical techniques are employed. In this paper, the influence of different numerical approaches on the performance prediction of a two bladed turbine model was assessed by towing tank results from the USNA. Two turbulence models of k-ω SST and BSL EARSM as well as three boundary layer modeling techniques, including wall function, near wall region and transitional Gamma-Theta model, were compared. The effects of using steady state or transient solution methods by applying moving reference frame (MRF) and sliding mesh were investigated. Single blade simulation instead of whole turbine model was also evaluated together with the Reynold number effect. Although Transient solution with sliding mesh method offers a simulation closer to the real condition of turbine operation with accurate results, steady state MRF provides reasonable results while saving a significant computational time as well. Therefore, authors recommend utilising steady MRF simulation of whole turbine model using k-ω SST with wall-function model for performance prediction of horizontal axis marine current turbines in a balance between simulation time and results accuracy.

Damage prediction of horizontal axis marine current turbines under hydrodynamic, hydrostatic and impacts loads

Marine energy is one of the most exciting emerging forms of renewable energy. Tidal turbines are used to extract this energy and installed on the seabed at locations with catastrophic loading. The present paper employs the finite element method to simulate the behavior of GRP composite nozzle of a tidal turbine under low-velocity impact with implementation of a failure criterion. To investigate this situation, a parametric analysis is conducted which deals with the effect of velocity, energy and geometry of the impactor. The mechanical behavior has been analyzed as both kinematic effect due to deflection of the composite structure and dynamic effect caused by the interaction between the impactor and the hydrodynamic and hydrostatic pressures over the loading. The stress and the deformation distribution are presented. On the other hand, damage modeling was formulated based on Hashin criteria for intra-laminar damage. The effects of the impact velocity and the panel’s flexibility on the initiation and propagation of damage have been investigated.

Experiments on the magnetic coupling in a small scale counter rotating marine current turbine

Modern economies are dependent on energy consumption to ensure growth or sustainable development. Renewable energy sources provide a source of energy that can provide energy security and is renewable. Tidal energy is more predictable than other sources or renewable energy like the sun or wind. Horizontal axis marine current turbines are currently the most advanced and commercially feasible option for tidal current convertors. A dual rotor turbine is theoretically able to produce more power than a single rotor turbine at the same fluid velocity. Previous experiments for a counter rotating dual rotor horizontal axis marine current turbine used a mechanical oil seal coupling that caused mechanical losses when water entered through small gaps at the shaft. A new magnetic coupling assembly eliminates the need for a shaft to connect physically with the internal mechanisms and is water tight. This reduces mechanical losses in the system and the effect on the dual rotor performance is presented in this paper.

Augmented Diffuser for Horizontal Axis Marine Current Turbine

<span>The potential of renewable energy sources is enormous as they can make a major contribution to the future of energy needs. The ocean has a great potential to become a practical and predictable energy source compared to other energy resources such as solar, wind, and nuclear. It offers different sources of energy which can be utilized namely wave, tidal, offshore wind, thermal, and tidal current. Among these sources, marine tidal current has major advantages such as higher power availability and predictability. The main objective of this research work is to design and develop a horizontal axis marine current turbine (HAMCT) that suitable for operating within Malaysian ocean, which has low speed current (0.5 – 1 m/s average). A prototype of augmented diffuser 4-bladed HAMCT applying NACA 0014 was proposed in the current study. The turbine model has 0.666 m diameter, and it was designed to produce as much as power from flowing water current. Model was constructed and tested at Marine Technology Center (MTC) in three conditions, namely, free tow testing, ducted tow testing, and ducted diffuser tow testing in order to predict the power and efficiency of the turbine system. The results showed that the application of duct was significant to concentrate the flow and diffuser arrangement was effective when it was placed behind of the rotor in this condition of low water current speed. The maximum efficiency Cp obtained in the current system was 0.58.</span>