Wave Turbine Research Articles

Comprehensive influence of dimensionless wave velocity and expansion ratio on energy absorption characteristics of variable wavelength traveling wave turbine

Based on the traveling wave motion of fish, this paper introduces a new type of variable wavelength traveling wave turbine that significantly differs from traditional turbine designs in its mechanical structure. By developing a two-dimensional traveling wavy plate model and conducting numerical simulations, this study investigates the relationship between the dimensionless wave velocity, variable wavelength coefficient, and expansion ratio, as well as their combined effects on the energy absorption characteristics of the variable wavelength traveling wave turbine. The results reveal that energy absorption efficiency peaks at an optimal dimensionless wave velocity, which is unaffected by changes in the variable wavelength coefficient. Furthermore, the expansion ratio significantly influences both the dimensionless wave velocity and the variable wavelength coefficient, with an optimal ratio of π∗ = 2.5 achieving 90.42 % efficiency. The energy absorption characteristics of the plate with a larger variable wavelength coefficient are found to be constrained by the expansion ratio. Additional analysis reveals that flow characteristics, such as the pressure distribution, vortex street, and velocity field surrounding the traveling wavy plate, are closely related to its energy absorption performance. These findings provide valuable insights for the design of variable wavelength traveling wave turbine.

A Novel Approach to Wave Energy Conversion Using CFD Technique

Abstract This article details the development and evaluation of a novel wave energy converter (WEC) aimed at efficiently capturing wave energy for electricity production. The study employs Computational Fluid Dynamics (CFD) techniques, specifically the URANS method and the k-ω SST turbulence model, to solve the Navier-Stokes equations and capture the free surface using the Volume of Fluid (VOF) model. The CFD results are validated against experimental data to ensure accuracy. Various design parameters of the proposed device were tested, revealing that the arms and bottom angle significantly affect its performance. Unlike the floating Wave Dragon (WD) device, which utilises potential energy and is set in deep water, the new fixed-seabed device is positioned in the transitional wave region near the shore, where waves retain 80% of their energy. It can be constructed from environmentally friendly cement, making it resistant to hurricanes and suitable for any wave turbine in the open sea. The MP687 turbine was used to capture the wave energy in the proposed device, testing its performance in three positions: in the open sea, in the middle of the device, and at the device’s outlet. The results show that the device significantly enhances wave energy concentration, especially when the turbine is placed at the outlet. The proposed device offers numerous advantages, including its fixed position in a high-energy wave zone, the efficient use of turbulent kinetic energy, and robust construction that can withstand storms.

Numerical simulation of wave-number effects on the performance of traveling wave pump-turbine in turbine mode

Pumped storage represents an economically viable, highly efficient, and extensive energy storage solution, receiving substantial research attention worldwide. This study utilized the energy dissipation of fish swimming in the water, and the traveling wave plate was arranged in a vertical rectangular flow channel to obtain energy through reverse thinking. Numerical simulation was employed to investigate the performance characteristics of the traveling wave turbine under varying wave number across high and low water head. The results reveal that the efficiency at low water head starts to increase and then decreases with the increase of wave number. There is an optimal wave number N = 4 to maximize turbine efficiency, and the maximum efficiency under low water head condition is 89.35 %. The efficiency of the high head condition shows a continuous upward trend, with a maximum value of 92.27 % in the range of wave number studied. With the increase of wave number, the instantaneous mass flow coefficient and power coefficient become more stable. The advantage of increasing the wave number is that more traveling wave plates can participate in energy capture, which is conducive to reducing the force required by each traveling wave plate and making the pressure distribution in each working cavity more regular.

The influence of peak of wave-channel clearance on performance characteristics of traveling wave turbine

Energy transformation is crucial for sustainable development, with pumped storage playing a key role. Central to this system is the hydraulic turbine, necessitating innovation to overcome traditional issues like cavitation and vibration. This study proposes the traveling wave turbine, integrating a mechanism of traveling wave motion into a vertical rectangular flow channel. Gravitational potential energy of water flow propels the traveling wave plate and the traveling wave mechanism is elegantly modeled as a two-dimensional wave plate. Through numerical simulation, we explore the influence of peak of wave-channel clearance on traveling wave turbine performance. Results show that decreasing peak of wave-channel clearance coefficient enhances time-averaged efficiency, reduces volume loss coefficient, and weakens fluctuations in instantaneous mass flow and power coefficients. High sensitivity to peak of wave-channel clearance changes is observed under a high head condition. Reduction in peak of wave-channel clearance decreases pressure difference between front and rear of the traveling wave plate at t/T = 0 and increases it at t/T = 0.25. Simultaneously, decreasing clearance coefficient leads to reduced fluid velocity at the contraction point, causing a noticeable decrease in vortex scale and intensity.

The world’s best practices in the development of aquaculture in the framework of the implementation of projects for the multipurpose use of the infrastructure of the fuel and energy complex

The article discusses the current international experience of integrating various aquaculture projects into the infrastructure of the fuel and energy complex. Against the background of the active growth in the production of aquaculture products, there is a tendency for the multipurpose use of energy sector facilities (oil platforms, wind farms, etc.) to obtain valuable aquaculture products both during their operation and after the completion of the project period of use. The specifics of the production and assortment of aquaculture facilities and farming methods in different regions of the world have been identified, which determined the features of the integration of aquaculture into fuel and energy facilities. The most common and has been used for many decades in many countries of the world is the cultivation of aquaculture facilities on the recycled water of thermal power plants and reservoirs of hydroelectric power plants. In the European region, there is an active use of offshore platforms for the extraction of hydrocarbons with simultaneous agricultural, aquaculture, scientific activities and the production of electricity through the installation of wind and wave turbines. Oxygen and hydrogen production is organized on some platforms. In North America, projects of hybrid systems “food-energy-water” are being developed using aquavoltaics technology, which allows maintaining the aquatic environment in optimal condition. Fish farming is combined with the cultivation of crustaceans and shellfish, oil platforms are often repurposed into artificial reefs. A patented project of an integrated floating system consisting of four vertical-axial wind turbines connected to a single system with a solar battery and a floating base for the placement of aquaculture facilities is being implemented in Asia. The development of such projects, in addition to the pronounced positive economic effect, also contributes to improving the level of food security of the regions. The use of engineering structures and other infrastructure facilities as new locations and substrates for the cultivation and free habitat of various hydrobionts can significantly reduce the negative impact of the fuel and energy industry on the environment.

Experimental Study of the Influence Wave Period on the Performance Darrieus Turbine with Modification of the Blade Angle

Indonesia has a long coastline that has the potential for renewable energy sources from waves to be used as an energy source for power generation. To take advantage of this potential, research has been carried out by testing the Darrieus-type vertical axis turbine model at the Indonesian Hydrodynamics Laboratory. The weakness of the wave turbine is that it cannot rotate due to the wave force due to the position of the turbine rotor which is perpendicular to the turbine axis. By changing the angle of the turbine blade in an inclined position, it is expected to produce optimal efficiency to produce rotor rotation. This paper describes the testing of a turbine model with an angled turbine blade that produces the best efficiency and rotation due to wave forces and ocean currents. The test is carried out by varying the angle of the turbine blade tilt (45°, 60°, and 75°). Each is given a variation in height and wave period but still, maintains the turbine rotor area. Furthermore, the torque, efficiency, rotation, and resulting power are measured. wave height of 0.15 meters with variations in wave periods ranging from 1.2 - 2.5 seconds. The test results show that a turbine with a rotor angle of 60° produces the best performance.

Study of aerodynamic performance of built-in variable wavelength traveling wave turbine

Turbines, as power sources for power generation, ships, etc. are capable of absorbing energy from high-temperature and high-pressure gas, converting thermal energy into mechanical energy. We propose a built-in variable wavelength traveling wave turbine that establishes a traveling wave mechanism in the rectangular flow channel. This device has the same function as a conventional turbine, extracting energy from incoming high-pressure gas, but it operates in a completely different way from axial flow and centripetal types. Numerical simulation is adopted to investigate the energy absorption characteristics and flow mechanism of the variable wavelength traveling wave turbine of two wave numbers. The traveling wave turbine is simplified to a two-dimensional traveling wave plate with analytical functions to control the motion parameters. The results show that influenced by variable wavelength, the motion waveform forms expansion type, equal wavelength type and contraction type. The curve of energy absorption rate of traveling wave turbine shows first increase and then decrease with the highest efficiency reaching 89.71%. The mass flow coefficients under two wave numbers correspond to the efficiency curves with approximately the same trend. There is the obvious distinction between pressure regions divided by the moving traveling wave plate, indicating that fluid energy is mainly transferred to traveling wave plate. The velocity varies prominently in X direction near the leading edge and trailing edge of the plate. Interestingly, as the variable wavelength changes, the vortex direction alters where the first formed vortex sheet shed the trailing part of the traveling wave plate. The area of vortex sheet varies significantly.

Traveling wave turbine - An internal flow energy absorption mode based on the traveling wave motion

The plate with traveling wave motion can obtain energy from fluid under certain motion parameters. This energy absorption method, which imitates motion of fish, is called traveling wave energy absorption method. In order to improve the energy absorption efficiency, the traveling wave plate is arranged in the rectangular flow channel and is driven by the high pressure gas coming through the inlet. This internal flow mode is called traveling wave turbine. The traveling wave plate is simplified as a two-dimensional plate. The aerodynamic characteristics of traveling wave turbine are studied by numerical simulation. The results show that: Benefiting from the confinement effects of the rectangular flow channel, the incoming flow can maintain high pressure. Therefore, the time-averaged energy absorption efficiency of traveling wave turbine can reach 62.84%. The pressure of the fluid is high before the traveling wave plate, but it becomes low when the fluid flows through the plate. This means that the energy of the fluid is absorbed by the traveling wave plate. There are vortexes in the traveling wave turbine and the vortexes with opposite rotating directions will accelerate the fluid between them.

Design Optimization of a Direct-Drive Electrically Excited Synchronous Generator for Tidal Wave Energy

In the field of marine renewable energies, the extraction of marine currents by the use of tidal current turbines has led to many studies. In contrast to offshore wind turbines, the mass minimization is not necessarily the most important criterion. In that case, Direct-Drive Electrically Excited Synchronous Generators (EESG) can be an interesting solution in a context where the permanent magnet market is more and more stressed. In the particular case of a tidal turbine, the electric generator operates at variable torque and speed all the time. Its sizing must therefore take into account the control strategy and check that all the constraints are respected during the working cycle, particularly the thermal one because its permanent regime is never reached. There is no solution today that can completely solve such a sizing problem. The paper presents a specific solution. In particular, we will see that the method presented allows an avoidance of an oversizing of the generator compared to conventional methods while finding the optimal control strategy. Thus, the design optimization of an EESG is conducted considering the variable torque and speed profiles related to marine currents. The analytical model used in the paper is presented at first. In a second step, the innovative and original method that allows solving at the same time the design optimization and the control strategy (dq stator currents and rotor current) are presented. It shows how it is possible to minimize both the lost energy during the working cycle and the mass while fulfilling all the constraints (especially the thermal constraint with its transient temperature response) and keeping a reduced computation time. The case of a 2 MW tidal wave turbine is chosen to illustrate this study. Finally, the optimal design selected is validated by a 2D magnetic Finite Element Analysis (FEA).

A new framework and tool for ecological risk assessment of wave energy converters projects

Marine renewable energy has considerable potential for enhancing the diversity of renewable sources, to reduce our reliance on fossil fuels and combat climate change. While the technological development of wave energy converters is progressing rapidly, their environmental impacts are still largely unknown, which is a barrier that could hinder their deployment. This research contributes to the state-of-the-art by introducing a framework for quantifying and analysing the ecological risks of three technologies (oscillating water columns, oscillating wave surge converters, and wave turbines). Based on a literature review, expert consultation process, and the development of a web tool, the potential pressures and the ecosystem elements that might be affected during the life cycle of a generic wave farm (an array of wave energy converters) are investigated. The main pressures are found to be physical disturbance, physical loss, hydrological change, and noise. The ecosystem elements sustaining the largest number of pressures and, therefore, at higher ecological risk are fish and cephalopods species, and benthic and pelagic habitats. The ecological risk assessment framework is operationalized into a free-access web tool (https://aztidata.es/wec-era/) for the interactive assessment and visualisation of the pressures and ecological risks. The tool is intended to be used by managers, decision makers, scientists or promoters during the Strategic Environmental Assessment and Environmental Impact Assessment of wave energy projects. The novel approach presented in this work is more sophisticated than previous risk assessment matrices, enabling to better capture the complexity of the interactions between a wave farm and the environment.

A new approach for integrating wave energy to the grid by an efficient control system for maximum power based on different optimization techniques

In this paper, a Wave Energy Conversion (WEC) model consisting of a Savonius type wave turbine plus DC generator, Battery Energy Storage System (BESS), inverter, and Inductance-Capacitance-Inductance (LCL) filter is designed. In this study, the optimization techniques are used to maximize Savonius type wave turbine self-efficiency considering different factors such as the height, depth, length, and time period of the wave. Four meta‐heuristic optimizations are competing in this article for obtaining the optimum parameter design based on the output electrical power of the wave. These are Whale Optimization Algorithm (WOA), Artificial Immune System (AIS), Bat Algorithm (BA), and Particle Swarm Optimization (PSO) algorithm. The comparative results verify the reliability of WOA in maximizing the overall electrical output power from the wave turbine while confining with the constraints. Moreover, an efficient control system is designed to operate in Islanded Mode (IM) and Grid-Connected (GC) operations according to the matching between the maximum estimated output power from the WEC system and the system load. A proposed control scheme is performed for adjusting the system frequency and voltage in islanded mode operation and ensuring active power-sharing in grid-connected mode. The islanded control scheme consists of three levels; droop control, inner voltage, and current control, outer control based on model predictive control (MPC) to maintain the system frequency and voltage to their nominal values. WOA is also proposed to improve the performance index by optimally evaluate the control signal and tracking error weighted parameters. The GC control scheme is based on the Active/Reactive Power (P/Q) controller to ensure active power-sharing. The effectiveness of the proposed controller has been verified by considering system parameters uncertainties.

Testing of hydrophobically coated composite materials with marine energy applications

Tidal turbine applications will place composite materials such as glass-fibre-reinforced polymers (GFRPs) and carbon-fibre-reinforced polymers under surprisingly high pressure due to the significant water depths they operate in (to depths of 50 m). The technical reliability of tidal turbines must be guaranteed despite the high dynamic loads resulting from the combination of plant operation, wind and waves with irregular swell. These external effects could lead to operation downtime and accelerated degradation. Research has already established that (unpressurised) moisture saturation is detrimental to both the tensile and fatigue strengths of a GFRP material compared with its dry laminate performance. This degradation has been shown to be stress dependent. It is possible that hydrophobic coatings could help protect the material while in service. Therefore, two commercially available coatings were applied to five variations of composite materials. These materials are commonly used in tidal and wave turbine blades, as they have excellent corrosion resistance and mechanical properties. All five were subjected to the same conditioning processes: non-pressurised and pressurised immersion conditioning in water. A glass-fibre epoxy (Ampreg) composite, along with a glass-fibre powdered epoxy composite, a glass-fibre polyether ether ketone composite and a carbon-fibre powdered epoxy composite, was investigated. The glass-fibre epoxy (Ampreg) was also subjected to static/fatigue tensile tests.

Numerical Optimization of the Blade Surface Geometry in a Wave Turbine System

Numerical Optimization of the Blade Surface Geometry in a Wave Turbine System

Numerical Modeling of a Wave Turbine and Estimation of Shaft Work

Wave rotors are periodic-flow devices that provide dynamic pressure exchange and efficient energy transfer through internal pressure waves generated due to fast opening and closing of ports. Wave turbines are wave rotors with curved channels that can produce shaft work through change of angular momentum from inlet to exit. In the present work, conservation equations with averaging in the transverse directions are derived for wave turbines, and quasi-one-dimensional model for axial-channel non-steady flow is extended to account for blade curvature effects. The importance of inlet incidence is explained and the duct angle is optimized to minimize incidence loss for a particular boundary condition. Two different techniques are presented for estimating the work transfer between the gas and rotor due to flow turning, based on conservation of angular momentum and of energy. The use of two different methods to estimate the shaft work provides confidence in reporting of work output and confirms internal consistency of the model while it awaits experimental data for validation. The extended wave turbine model is used to simulate the flow in a three-port wave rotor. The work output is calculated for blades with varying curvature, including the straight axial channel as a reference case. The dimensional shaft work is reported for the idealized situation where all loss-generating mechanisms except flow incidence are absent, thus excluding leakage, heat transfer, friction, port opening time, and windage losses. The model developed in the current work can be used to determine the optimal wave turbine designs for experimental investment.

DESIGN AND DEVELOPMENT OF WAVE TURBINE

The basic principle of Hydroelectric Generator is used in Electricity generation by Floating Hydro-Turbine. Every aspect of a hydro system revolves around Head and Flow. The generation of electricity is simply a conversion of one form of power to another one. This research describes design and development of wave turbine that could be used in local seashore of konkan region of Maharashtra, India

Enhancement of performance of wave turbine during stall using passive flow control: First and second law analysis

Wells turbine is the most common type of self-rectifying air turbine employed by Oscillating Water Column (OWC) wave energy devices due to its technical simplicity, reliability, and design robustness. Because it subjected to early stall, there were many endeavors to improve the energy extraction performance of Wells turbine within the stall regime. Using the multi suction slots as a passive flow control can help obtaining a delayed stall. Two, three and four suction slots were investigated to improve the performance of Wells turbine in the stall regime. In addition the commonly used first law analysis, the present study utilized an entropy generation minimization method to examine the impact of the multi suction slots method on the entropy generation characteristics around the turbine blade. The turbine blade with optimum suction slots number and location was investigated using the oscillating water system based on the real data from the site. To achieve this purpose, two-dimension numerical models for Wells turbine airfoils under sinusoidal wave flow conditions were built and analyze using (ANSYS FLUENT) solver. It is found that the airfoil with three suction slots located at 40%, 55% and 90% from leading edge in chord percentage give the highest torque coefficient by 26.7% before the stall and 51% after the stall.

Comparative analysis of different wave turbine designs based on conditions relevant to northern coast of Egypt

Wave energy has a great potential to solve the unrelenting energy deficiency in Egypt. The present work recommends Wells turbine as a suitable choice for the Egyptian coasts due to its simple and efficient operation under low input air flow. In addition, the possibility of extracting the wave energy from the Egyptian coasts was investigated using the oscillating water system based on real data from the site. To achieve this purpose, two-dimensional numerical models for Wells turbine airfoils, functioning under sinusoidal wave flow conditions, were built. Moreover, the running and starting characteristics under sinusoidal-flow conditions were investigated using a mathematical code. The results were discussed using the first law analysis, in addition to the second law analysis by using the entropy generation minimization method. It was found that the NACA0015 airfoil always gives a global entropy generation rate that is less than other airfoils by approximately −14%, −10.3% and −14.7% for the sinusoidal wave with time periods equal to 4, 6 and 8 s respectively. Moreover, the effects of blade profile, time period and solidity on the output power (kW) value were discussed.

Marine electrical power industry with renewable energy carriers. Part 1. Wind and wave turbines of offshore power plants

The paper is devoted to offshore wind and wave power plants as an alternative to fossil hydrocarbon power engineering. It reports classifications and an analytical survey of the state-of-the-art of main types of offshore wind and wave turbines. The features of horizontal and vertical axes turbines constructions are described. Comparison of these two types of turbines has revealed the vertical axes design advantage since their height is two to three times less and its stability, accordingly, is higher. This allows expensive concrete tower constructions to be avoided and floating pontoons to be used, which is especially important for deep-water areas. The advantages of a two-contour wind turbine consisting of a fixed stator and a rotor directly connected with an electrical generator are highlighted. Due to the special “soaring in air” block construction of the turbine, the pressure on the seabed foundation is considerably reduced, allowing all the supporting structure for a floating pontoon to be replaced. The designs of wave turbines with direct and indirect operation are considered as well, the principles of harnessing marine wave energy are discussed and industrial prototypes of power plants of foreign firms are presented. With the help of analytical expressions, the evaluation of power performances is executed and a comparison of the power density criterion of wave energy with other kinds of renewable energy is indicated. It appears that the energy density of sea waves is an order greater of similar magnitude of wind and solar energy. On the basis of the idea of floating structures, the principles of designing hybrid and cluster offshore wind and wave power stations are suggested, where, with the help of power electronics and information technology, the electric energy of separate turbogenerators is integrated into a marine power pool system with HVDC underwater cable transmission to the consumers of a continental zone.

Performance analysis of a horizontal axis 3-bladed Savonius type wave turbine in an experimental wave flume (EWF)

The present experimental study investigates the generation and propagation of regular water waves and their interactions with an in-house fabricated horizontal-axis 3-bladed Savonius rotor in an experimental wave flume (EWF) equipped with a piston-type wave maker with active absorption capability to assess the rotor performance for different parametric conditions namely, wave height, wave period and submergence level in intermediate-to-shallow water depths. The motion of the wave particles around the Savonius rotor is observed during the experiments as well as measuring the power and torque performance of the rotor to make a reliable assessment of the water movement with the rotor positioning for different inflow wave boundary conditions. The wave-to-mechanical energy conversion efficiency (ECE) of the present device is determined for each case to suggest a possible optimum positioning accompanied with optimum wave heights and frequencies for the manufactured small scale prototype. The present results suggest that experimental solutions within the wave flume can provide a proper guideline for performance analysis of such devices in intermediate-to-shallow water depths for further studies of optimization of design of Savonius rotor type sea and/or ocean wave energy conversion devices for different operating conditions provided that optimum physical flow conditions are satisfied.

Extended wave power formulation by perturbation theory and its applications

Water wave is a powerful source of energy; the problem is harnessing and making use of it. Wave power is a renewable, pollution-free and sustainable energy source. Since wave power varies with the wave period and the square of significant wave height, it is necessary to quantify the variations and statistical characteristics of these parameters with time. The aim of this study was to derive a general wave power equation that can be used in order to determine the mean and the standard deviation of the wave parameters using perturbation approach. The result of the study showed that Weibull probability distribution function is able to accurately simulate wave power. The wave power equation developed in this study is a general formula and can be applied at any desired region. The equation was then applied to five stations and it was seen that the perturbation approach yields better statistical values compared to results determined using classical statistical approach. This indicates that it is necessary to use perturbation approach to achieve optimum wave turbine design.