Wave Power Generation Research Articles

Design and Performance Analysis of a Staggered Vernier Generator for Wave Power Generation

In this paper, a staggered vernier generator suitable for a counter-rotating self-adaptable WEC is proposed to meet the energy demand of the small-scale engineering equipment in the deep sea. According to the vernier effect of the magnetic gear, the generator modulates the low-order rotating magnetic field generated by the rotation of the low-speed permanent magnet rotor into a high-order magnetic field rotating at a high speed, thereby realizing the acceleration of the generator magnetic field. A staggered structure permanent magnet vernier generator with 18 teeth/28 poles is designed. The main magnetic flux path on the staggered structure in the staggered vernier generator is analyzed, and the air-gap magnetic field distribution of the generator is analyzed with the help of numerical simulation software. The influence of different design parameters on the vernier generator is discussed. The staggered vernier structure can improve the main magnetic flux of the generator, reduce the magnetic flux leakage, and improve the performance of the generator without adding additional structures and materials.

Wave attenuation and focusing performance of parallel twin parabolic arc floating breakwaters

The hybrid system consisting of floating breakwater and point absorber wave energy converters provides a promising solution for shoreline protection and wave power generation. In the hybrid system, the breakwater plays an important role in protecting the sheltered area on the lee side and focusing high waves for better energy harvesting on the weather side. To improve the wave attenuation and focusing performance, a twin-breakwater consisting of a pair of parallel parabolic pontoons is proposed. Based on the potential flow theory of linear waves, the influences of gap width and connection method applied between the two pontoons are studied in the frequency domain, with an emphasis on the so-called critical mode around which both wave attenuation and focusing could be improved. Results show that the rigidly connected twin-breakwater is superior to the unconnected twin-breakwater with the same configuration in both wave attenuation and focusing. A second critical mode with lower frequency is also found under particular gap width, providing a potential for the defense of long waves. An optimal attenuation could be obtained by applying a proper gap width.

Development of the Reciprocating Airflow Generator for Wave Power Generator and Study on the Vertical Axis Turbine Characteristics in Reciprocating Airflow

Development of the Reciprocating Airflow Generator for Wave Power Generator and Study on the Vertical Axis Turbine Characteristics in Reciprocating Airflow

Optimal design of linear switched reluctance motor for sea wave power generation

The switchless reluctance motor’s non-permanent magnet structure design ensures its high reliability in the marine environment; thus, it is a feasible solution for the generator of a sea wave power generation system. However, the corresponding thrust density and efficiency remain insufficient. This study focused on a new type of flat linear switched reluctance motor (LSRM), using the finite element software to establish a structural model, and optimized the design with the goal of improving the efficiency and energy density. The entropy method was adopted for sensitivity stratification to objectively select weights to avoid the influence of subjectively selected different proportional weights on the optimization results. Based on the entropy method, the sensitivity of different structural parameters was stratified, and the simulated annealing algorithm, response surface method, and single parameter scanning method were combined for optimization. Finally, the optimal structural size parameters of the motor were determined. Based on the two-dimensional finite element method, to simulate the electromagnetic performance of the reluctance motor under different operating conditions, such as thrust, loss, and efficiency, changes in motor performance before and after optimization were compared to verify the high power generation efficiency and energy density of the optimized linear motor.

Conceptual Design Study Based on Reliability Assessment of Secondary Energy Conversion Mechanical System in Movable Object Type Wave Power Generator

Movable object type wave power generators produce energy through the process of primary energy conversion, which converts the potential and kinetic energy of the waves into mechanical energy, secondary energy conversion that converts it into energy for generator operation using a mechanical system or hydraulic system, and final energy conversion, the last step in power generation. The secondary energy conversion system that transmits and amplifies energy according to the primary energy conversion needs to secure durability while power generation performance varies greatly depending on how the secondary energy conversion system is built. As a result, reliability assessment of systems based on system engineering are a very important issue. Therefore, in this study, for the conceptual design based on reliability assessment of the secondary energy conversion system, the system concept was established using the integrated computer-aided manufacturing (ICAM) definition for function modeling (IDEF0), a system analysis method, while necessary equipment and process flow diagrams (PFD) were derived. In addition, the database (DB) and formula of the secondary energy conversion system were constructed, and reliability assessment algorithms and programs were developed. Finally, the PFD and reliability assessment program were verified by applying them to a representative movable object type wave power generator.

Meteo-Climatic Conditions of Wind and Wave in the Perspective of Joint Energy Exploitation: Case Study of Dongluo Island, Hainan

Combined wind and wave power generation has advantages such as energy synergy and complementarity and will play a leading role in the integrated development of offshore renewable energy. From the perspective of joint energy development, this study focuses on the meteo-climatic wind and wave conditions in Dongluo Island, Hainan, in the South China Sea. Based on the concurrent measurement from in situ monitoring system, hourly data from June 2020 to September 2021 are used to reveal typical climate characteristics associated with the weak (inverse) correlation between wind and wave. The energy flux density of wind and wave are also assessed to describe the energy pattern. Principal component analysis (PCA) shows the wind parameters contribute a larger variance to the matrix of the wind–wave dataset than the waves, suggesting a lower stability of the wind climate. The first three components via PCA are then classified into five clusters to represent different climatic characteristics. Among them, the dominating cluster symbolizes a climatic circumstance with weaker winds and waves below normal. This cluster, evenly distributed in different seasons, shows the lowest wave–wind correlation, suggesting a favorable condition of the synergy of the two energies throughout the year. The clusters with the second and third largest sample sizes are mainly dominated in spring and winter, respectively. The magnitudes of the wind and wave parameters in these two clusters yield to a relation of “as one falls, another rises”, implying a high interest in complementarity between the two resources to a certain extent. The energy features inferred by meteo-climatic clusters are further verified by direct assessment of energy density. There are generally consistent variations between wind–wave climate and energy, both in magnitude and in seasonality. Based on these results, differentiated exploitation schemes considering the complementarity or synergy of wind and wave according to different seasons are recommended.

A communication-free droop control scheme for distributed linear switched reluctance wave power generation system with adaptive voltage compensation

In wave energy generation systems, scaled and improved energy extraction can be realized by utilizing distributed linear switch reluctant generators (LSRGs). However, this type of power generation system often employs supercapacitors (SCs) as the energy storage media, and the system often suffers from output voltage variation and current fluctuation from the LSRGs. Meanwhile, the fixed droop factor also causes bus voltage deviation and aggravates energy imbalance of the energy storage system. In this paper, a communication-free droop control scheme with adaptive voltage compensation is proposed for the distributed linear switched reluctance wave power generation system. First, system stability is improved by applying a high droop factor. When the bus voltage fluctuation exceeeds the compensator threshold, this voltage information of the energy storage unit is introduced into the control loop. In addition, an adaptive voltage compensation algorithm is proposed for the system, and the control algorithm is able to reduce the bus voltage deviation and the energy imbalance of the storage unit, caused by the droop factor. The proposed control strategy can further improve the response and reliability of the energy storage units, and the bus voltage fluctuation can be regulated within ±3%.

Fully Coupled Analysis of an Integrated Floating Wind-Wave Power Generation Platform in Operational Sea-States

The offshore wind power exploitation has experienced rapid development in recent years and has gradually moved into deeper waters with the floating wind turbine technology getting mature. Due to the strong concurrence of the wind and wave power in offshore sites, the idea of combined utilization of wind and wave power by one integrated device has attracted tremendous interests worldwide and a number of concepts and designs have been proposed. This article describes a novel integrated floating wind-wave generation platform (FWWP) consisting of a DeepCwind semi-submersible floating offshore wind turbine (FOWT) and a point absorber wave energy convertor (PAWEC). Three models including the single PAWEC, single FOWT, and FWWP are considered to investigate the feasibility of the FWWP and its advantages over the single device. Hydrodynamic analyses are first conducted using the potential flow code AQWA with the viscous correction to investigate the hydrodynamic interactions effect of the integrated model. Then, a fully coupled model for the FWWP is established by calling OpenFAST in AQWA using the F2A method. The accuracy of the established coupled model is firstly validated with OpenFAST for analysing the dynamics of the single FOWT. Finally, fully coupled analyses of the FWWP are carried out for both regular and irregular waves in the operational sea-states. The coupled dynamics and wind and wave power generation of the FWWP are compared with those of the single PAWEC and FOWT for both the regular and irregular waves.

Research on adaptive segmented control strategy used in direct-drive wave power generation systems

The problem of unstable output power in direct-drive wave power generation systems (DDWPGS) caused by violent power variation in one cycle of wave is common. The wave power fluctuates violently in a short time, and the lower the frequency, the higher the amplitude. Energy storage devices are usually applied to smooth the power and stabilize the system. This paper proposed an adaptive segmented control strategy (ASCS). It adaptively divided the system voltage into five symmetrical segments and regulated the reference power based on the VMD decompose results according to the different segments. The impedance analysis method (IAM) is implemented to verify its stability. The simulation results confirmed that it can not only automatically adjust the output of the energy storage device to adapt to the frequency and amplitude of wave power signal, but also ensure the safe operation of the system under the impact of charging load and wave power.

Technical Feasibility Analysis of the Patent Ondomotric Energy Generations System With Code BR 10 2016 016119 3 A2

With the industrial expansion arising from the national development process, and the current global trend towards the search for clean and renewable energy sources, the diversification of the energy matrix becomes vital in the process of renovation and strengthening of energy generating sources to meet the SIN (National Interconnected System). This work presents the technical feasibility analysis of the wave power generation prototype with patent code BR 10 2016 016119 3 A2. The simulations carried out in modeling software to evaluate the constructive aspects of the prototype allowed the analysis of data on the mass of the components, gravity centers, and moments of inertia. Finally, the positive and negative aspects and points for improvement of the project were presented, aiming to raise interest in the topic presented and develop new studies for the electricity sector.

Simulation and Optimization Design of Large Wave Power Generation Device Based on Group Array Module

Based on the research achievements of the Haiyuan 1 oscillating buoy wave power generation device, this paper proposes the innovation about a group array of the buoy to increase the output of power generation and realize large-scale power generation. Firstly, the conversion efficiency of wave energy captured by buoys of arrays 3, 6, and 9 for power generation is theoretically estimated. According to wave theory, the energy conversion efficiency of buoy increases with the increase of array number. Then, the modeling and simulation of the buoy array wave energy generation system are carried out by using AMESim simulation software. Through the simulation and optimization of the parameters of the components in the array buoy storage power generation system, the stability and efficiency of the wave power generation device under different array buoys are studied. The simulation results show that by adjusting the volume of the accumulator, precharge pressure and the displacement of the hydraulic motor, the power generation system can not only realize the continuous power output, but also the power output increases with the increase of the number of accumulators. It is proved that the feasibility and rationality of the designed buoy power generation system in group array module, and the research results can make a reliable technical reference for the construction and implementation of large-scale wave power generation system.

Propagation and attenuation of swell energy in the Pacific Ocean

Understanding the characteristics of swell propagation is practical for swell monitoring, early warning and wave power generation. In this study, the attenuation rate of swell energy during the propagation process is defined. Then, the propagation, attenuation and intraseasonal oscillation characteristics of swell energy in the Pacific Ocean are analyzed based on the 40-year European Centre for Medium-Range Weather Forecasts (ECMWF) reanalysis (ERA-40). Results show that (1) The swells generated from the North Pacific Ocean westerlies (NPOW) and the South Pacific Ocean westerlies (SPOW) usually propagate to the low latitude waters of the Pacific Ocean. (2) Swells in Hawaiian waters, Cologne Islands waters and Iquique waters mainly originate from the winter hemisphere. (3) It takes approximately 8 days for the swell to propagate from the SPOW to Cologne Islands waters. It takes approximately 7.5 days for the swell to travel from the NPOW to Cologne Islands waters. (4) An obvious attenuation of swell energy of 60%–90% occurs during the propagation process. (5) Swell energies in the SPOW, NPOW, Hawaiian waters, Cologne Islands waters and Iquique waters share a common quasi-biweekly oscillation. The attenuation rate of the swell energy has a significant quasi-weekly or quasi-biweekly oscillation.

Sea trial test on offshore integration of an oscillating buoy wave energy device and floating breakwater

Wave energy has not yet been commercialized due to its high cost and low efficiency. The combination of wave energy devices and breakwaters can greatly improve the utilization of breakwaters and also reduce the cost of wave power generation devices. In this paper, four oscillating buoy wave energy devices with different geometries are proposed, where a kind of dolphin buoy design method with excellent energy harvesting mechanism is formed. And the integrated method of wave energy device and floating breakwater is proposed and the integrated model is tested in the tank, and on the basis of that a one-year sea trial test of the prototype was carried out in the real sea area, and the power generation performances of the wave energy device under different sea conditions are analyzed. The sea trial results show that the average energy conversion efficiency of wave energy device can reach more than 18% when the significant wave height is from 0.5 m to 2 m and an average period is from 2 s to 6 s, and that can even reach 27.2% under the optimal sea state. The research and manufacturing process of sea trial prototype and the sea trial operation of the prototype show that the combination of oscillating buoy wave energy device and floating breakwater can reduce the construction cost of wave energy device and also improve reliability and energy conversion efficiency of that. The research results of this paper are of great significance for the further commercialization of wave energy devices.

Practice of Energy and Environmental Education in Okinawa

With the support of the "Energy Education Survey Project" of the Agency for Natural Resources and Energy, the "Okinawa Energy and Environmental Education Study Group" was established in 2006. Since then, we have been conducting practical research on energy and environmental education that takes advantage of the characteristics of the Okinawa region. The members of the study group are university teachers, elementary, junior high, and high school teachers, government officials, energy-related companies. We report on the energy teaching materials (wave power generation, PET bottle windmill, energy conversion experimental equipment, model condenser car, polymer electrolyte fuel cell, model fuel cell vehicle, etc.) developed so far, as well as the implementation of visiting classes, lectures and energy-related facilities tours.

A Communication-Free Droop Control Scheme for Distributed Linear Switched Reluctance Wave Power Generation System with Adaptive Voltage Compensation

A Communication-Free Droop Control Scheme for Distributed Linear Switched Reluctance Wave Power Generation System with Adaptive Voltage Compensation

System Modeling and Simulation of Oscillating Flapping-wing Wave Power Generation Device

System Modeling and Simulation of Oscillating Flapping-wing Wave Power Generation Device

Analysis of a Two-Degree-of-Freedom Vibration System Model of an Oscillating water column wave energy converter installed on a double-slit breakwater

Breakwaters protect beaches by absorbing wave energy. Double-slit breakwaters can be used as air chambers for oscillating water column wave energy converters. In this study, the oscillating water column-type wave power generator using the double-slit breakwater was treated as a two-degree-of-freedom oscillating system model. The differential equations of motion were derived from Newton's second law, and the frequency response characteristics of the vibration of the oscillating water column- type wave energy converter using the double-slit breakwater were investigated using Simulink in MATLAB.

A Review of the Optimization Design and Control for Ocean Wave Power Generation Systems

Ocean wave power generation techniques (converting wave energy into electrical energy) have been in use for many years. The objective of this paper is to review the design, control, efficiency, and safety of ocean wave power generation systems. Several topics are discussed: the current situation of ocean wave power generation system tests in real ocean waves; the optimization design of linear generator for converting ocean wave energy into electrical energy; some optimization control methods to improve the operational efficiency of ocean wave power generation systems; and the current policy and financial support of ocean wave power generation in some countries. Due to the harsh ocean environment, safety is another factor that ocean wave power generation systems will face. Therefore, before the conclusion of this review, a damping coefficient optimization control method based on the domain partition is proposed to improve the efficiency and safety of ocean wave power generation systems.

Design and research on the simulation platform of Oscillating Flapping-Wing Wave Energy Converter based on AMESim

It is a stochastic dynamic process for conversion of wave energy, which includes the coupling of multiphysics. Energy conversion efficiency and stable output are important objectives. In order to explore the mechanism of wave energy efficient conversion, a wave energy generation scheme of oscillating-flapping wing was proposed. Taking the conversion system of wave power generation device as the research object, the mechanical-hydraulic-circuit simulation platform of the system is established by the software AMESim. The proposed scheme is tested and verified. The results show that the wave energy conversion system can effectively convert wave energy, realize the stable output of electric energy and store it in the battery pack, which provides a theoretical basis for the development of wave energy generation converter of oscillating-flapping wing.

POWER GENERATOR FROM OCEAN WAVE ENERGY CONVERSION

The need for electrical energy has increased every year. On the other hand, the largest power plants in Indonesia still use non-renewable energy sources such as coal and petroleum, while these non-renewable energy sources will eventually run out. To anticipate running out of this energy, a renewable energy source is needed. This existence will not run out even though it is consumed every day. Renewable energy that can be used for conversion into electrical energy in coastal areas is wave power. The waves that always crash on the shoreline can be used to drive turbines. The turbine rotates due to the crashing waves connected to a DC generator. It will convert mechanical energy into electrical energy. The electrical energy generated by the DC generator is used to charge the battery. The purpose of this research is the know-how to design a wave power generator and to determine the performance. The experimental method is used in this study. In the results, the generator works optimally during the day with the resulting voltage of 10.6 V to 10.7 V with rotation speed of 623 Rpm to With 710 Rpm.