Study of Hydrodynamic Characteristics of A Sharp Eagle Wave Energy Converter

According to Newton＇s Second Law and the microwave theory, mechanical analysis of multiple buoys which form Sharp Eagle wave energy converter （WEC） is carried out. The movements of every buoy in three modes couple each other when they are affected with incident waves. Based on the above, mechanical models of the WEC are established, which are concerned with fluid forces, damping forces, hinge forces, and so on. Hydrodynamic parameters of one buoy are obtained by taking the other moving buoy as boundary conditions. Then, by taking those hydrodynamic parameters into the mechanical models, the optimum external damping and optimal capture width ratio are calculated out. Under the condition of the optimum external damping, a plenty of data are obtained, such as the displacements amplitude of each buoy in three modes （sway, heave, pitch）, damping forces, hinge forces, and speed of the hydraulic cylinder. Research results provide theoretical references and basis for Sharp Eagle WECs in the design and manufacture.

Research of Power Take-off System for “Sharp Eagle Ⅱ” Wave Energy Converter

The " Sharp Eagle” device is a wave energy converter of a hinged double floating body. The wave-absorbing floating body hinges on the semi-submerged floating body structure. Under the action of wave, the wave-absorbing floating body rotates around the hinge point, and the wave energy can be converted into kinetic energy. In this paper, the power take-off system of " Sharp Eagle Ⅱ” wave energy converter (the second generation of " Sharp Eagle”) was studied, which adopts the hydraulic type power take-off system. The 0-1 power generation mode was applied in this system to make the " Sharp Eagle Ⅱ” operate under various wave conditions. The principle of power generation was introduced in detail, and the power take-off system was simulated. Three groups of different movement period inputs were used to simulate three kinds of wave conditions, and the simulation results were obtained under three different working conditions. In addition, the prototype of " Sharp Eagle Ⅱ” wave energy converter was tested on land and in real sea conditions. The experimental data have been collected, and the experimental data and simulation results were compared and validated. This work has laid a foundation for the design and application of the following " Sharp Eagle” series of devices.

Single Mode Simulation Calculation of Oscillating Buoy Wave Energy Converter with A Slider

This paper presents an oscillating slider wave energy device which is based on a seabed anchoring and uses eagle beak as the absorber.The self-compiled program uses the boundary element theory based on the simple Green’s function to solve the wave forces and hydrodynamic parameters.And the equation of motion,the oscillation of the float and the capture width ratio are obtained by the modal method.The influences of the shape of the eagle beak,the angle of the slider and the wave heading on the capture ability of the device are investigated.According to the calculation results and the wave resources in the sea area,the optimal shape of the eagle beak and external damping can be selected to maximize the wave energy capture capability.

Development of OIST Wave Energy Converter Monitoring System for Maldives Island Experiment

This paper describes experiments with our self-built Wave Energy Convertor(WEC)monitoring system in the Maldives and demonstrates how we developed a horizontal-axis type,half-scale,wave energy converter(WEC)that generates electricity in the coastal breaking wave zone.In order to measure this power generator and turbine’s efficiency,voltage and current were measured by pulling the generator with a 35 cm diameter turbine(half scale).We obtained data showing 400 W peak power in water speed of 3.1 m/s.Consequently,we assembled two sets of WEC,placed them near the shoreline on Kandooma Island in the Maldives in May 2018,and measured the wave energy at the breaking wave zone.A monitoring system was set up in one rack for the two sets of WECs,connected simultaneously.Two outputs of the generators were rectified and connected to power resistors and internal LED displays.The outputs could also be switched to connect to 24 electric double layer capacitors(EDLC),in order to perform a continuous lighting test of external high-power LED lights.The wave power data were continuously saved by an automated data logger and could be transferred from the installation site,to Japan via the Internet.The wave power was measured on Kandooma Island in the Maldives for a long period,and is still ongoing.Examples of the obtained data are shown in this paper.

Optimal control of oscillation wave energy system using velocity premonition

Recently ocean wave energy draw much more attention for its widespread,abundant and highly energy flux density properties.Extracting energy from incident wave however,is limited for the random and unstable power input.Motion control for WEC is a promising method to improve the energy absorption and some practical applications are also verified such as latching control.In this paper,an active control strategy is proposed to achieve maximum energy capture.The mathematical description shows that the active control has the characteristic of anti-causal and the wave premonition is necessary for controller design.But the fact of premonition time horizon is still unclear.In this paper,the premonition nature is described mathematically based on hydrodynamic theory.Furthermore,a simulation is also performed to study the impacting of premonition time horizon on WEC's properties and give a more insightful understanding of WEC active control.

Wave Energy Assessment Along the Moroccan Atlantic Coast

The aim of the present work is to assess the offshore wave energy potential along the Atlantic coast of Morocco.Research works of this paper focus on the identification of the most energetic sites for wave energy converters(WECs)deployment.For this purpose,11 sites have been explored;all of them are located at more than 40m depth on the Moroccan Atlantic coast.The wave power at each site is computed on the basis of wave data records in terms of significant wave height and energy period provided by theWaveWatch three(WW3)model.Results indicate that the coast sites located between latitudes 30°30′N and 33°N are the most energetic with an annual average wave power estimated at about 30 kW?m^-1,whereas,in the other sites,the wave power is significantly lower.Moreover,the study of the monthly and seasonal temporal variability is found to be uniform in the powerful sites with values four times greater in winter than in summer.The directional investigation on the significant wave height has shown that for almost all the powerful sites,the incoming waves have a dominant sector ranging between Northern(N)and Western-Northern-Western(WNW)directions.

Optimization of an annular wave energy converter in a wind-wave hybrid system

A hybrid system of a spar-type floating offshore wind turbine and a heaving annular wave energy converter(WEC)provides a promising solution for collocated ocean renewable energy exploitation.The performance of the hybrid system depends on the dimensions of the WEC.Here an optimization method is proposed to determine the outer radius and the draft of the WEC under the wave condition in a randomly chosen operational site.First,three candidate models are selected based on three operational conditions of energy harvest:(1)The natural frequency of the system is matched with the peak wave frequency in the target site(referred to as synchronized mode),where the wind turbine and the WEC nearly heave together in a near-resonance condition,(2)The natural frequency of the WEC is matched with the peak wave frequency(ring mode),(3)The maximum wave power is harnessed under the peak wave frequency(target mode).Then the candidate modes are evaluated to obtain an optimum.Results show that the extracted wave power under the above operational conditions has an upper bound that can hardly be surpassed by enlarging the dimensions of the WEC only.The optimal annual wave energy production is achieved in the synchronized mode because of the superior performance of WEC over a wide bandwidth of effective energy conversion.

Evaluation and optimization of a hybrid wave energy converter using excited motion response in two degrees of freedom

As waves in China seas are not high,a wave energy converter consisting of a coaxial annular buoy and a cylindrical buoy that extracts wave energy using two generators through the relative heave motion between the buoys and the pitch motion of the cylinder could be a more efficient choice.A dynamic model considering constraints and assuming linear power take-off is established to evaluate the power performance of the device.The influences of two key factors,the diameter of the annular buoy and the power take-off stiffness of the pitching generator,and their couplings on the power performance are analyzed.The power of the pitching generator accounts for a major proportion of the total power.An increase in the annular buoy diameter increases the power of the heaving generator while greatly decreases the power of the pitching generator.An increase in the power take-off stiffness of the pitching generator greatly decreases its power while has little influence on the power of the heaving generator.These two factors also influence the peak period of the total power.Based on the findings and practical limitations,an optimization strategy is proposed.Further,the device is optimized based on a real wave environment in Shandong Province,China.

基于改进蜜獾算法的波能转换器阵列优化

针对波浪能转换器(WEC)阵列发电效率提升问题,提出一种基于改进蜜獾算法的三系WEC阵列优化方法.首先,为克服原始蜜獾算法(HBA)收敛速度慢、收敛精度低等缺陷,引入佳点集初始化、混沌机制和蜜獾种群变异3种策略对原始HBA进行改进.此外,为了验证改进蜜獾算法(IHBA)的先进性和有效性,开展2个浮标、10个浮标和20个浮标3个不同规模的WEC阵列优化实验.2浮标阵列仿真结果表明,WEC阵列优化存在多组最优解,且IHBA、HBA、遗传算法和粒子群优化算法都能以不同速度找到最优解.然而,随着WEC阵列规模的增大,3种对比算法都会陷入局部最优解.相反地,IHBA依然表现出较强寻优能力并能搜寻到全局最优解.最后,IHBA所获10浮标和20浮标的阵列q因子分别高达1.059和0.968,远优于其他3种算法.

基于改进秃鹰优化算法的海上混合光伏波浪能转换器阵列优化

近年来,海上能源发电技术备受瞩目,一种新兴趋势是将波浪能转换器(wave energy converter,WEC)与海上光伏(offshore floating photovoltaic,OFPV)相结合,形成混合光伏-波浪能转换器系统(hybrid PV-wave energy converter,HPV-WEC)。HPV-WEC具有提高海上空间利用率,降低成本以及实现功率稳定输出等优势。为了充分利用HPV-WEC系统之间的协同效应,在不增加新设备的情况下提高能源产量,提出了一种基于改进秃鹰优化算法(improved bald eagle search algorithm,IBES)的HPV-WEC阵列布局优化策略。IBES结合了莱维飞行策略和模拟退火(simulated annealing,SA)机制,以平衡局部开发和全局探索之间的关系。为了评估IBES在优化HPV-WEC阵列方面的有效性,进行了5个浮标和8个浮标规模的阵列优化,并将IBES与其他5种算法进行了比较。实验结果表明,IBES表现出实现最大总功率输出并具有显著的收敛特性。

Parametric Study of Two-Body Floating-Point Wave Absorber

In this paper, we present a comprehensive numerical simulation of a point wave absorber in deep water. Analyses are performed in both the frequency and time domains. The converter is a two-body floating-point absorber （FPA） with one degree of freedom in the heave direction. Its two parts are connected by a linear mass-spring-damper system. The commercial ANSYS-AQWA software used in this study performs well in considering validations. The velocity potential is obtained by assuming incompressible and irrotational flow. As such, we investigated the effects of wave characteristics on energy conversion and device efficiency, including wave height and wave period, as well as the device diameter, draft, geometry, and damping coefficient. To validate the model, we compared our numerical results with those from similar experiments. Our study results can clearly help to maximize the converter＇s efficiency when considering specific conditions.

Numerical examination of wave power absorption by the Edinburgh Duck wave energy converter device

A two-dimensional computational fluid dynamics(CFD)numerical model is developed to study the power takeoff(PTO)efficiency of an Edinburgh duck wave energy converter(WEC)device by using the OpenFOAM source package.After the numerical validations and the convergent verifications,the characteristics of the duck WEC device for the power takeoff in various incident wave periods are examined.The present numerical investigation indicates that the maximum absorbed power of the duck WEC device is attained in its resonant period,while the maximum efficiency is achieved in a lower period.The influence of the damping coefficient on the PTO is also investigated.The optimal damping coefficient for acquiring more power and better efficiency is determined from a numerical examination.

Experimental Study on Hydrodynamic Response of Semisubmersible Platform-Based Bottom-Hinged Flap Wave Energy Converter

A semisubmersible platform-based(SPB)bottom-hinged flap(BHF)wave energy converter(WEC)concept is presented in this paper,and its platform hydrodynamic response was studied experimentally.Aimed at studying the special WEC-mounted platform response problem,both regular and irregular wave experiments were conducted.The frequency domain results of regular wave experiments are described in the form of response amplitude operators.The time domain results of irregular wave experiments are treated by statistical analysis and fast Fourier transformation.Regular wave experiments and irregular wave experiments show good consistency.The mooring system strongly affects the whole system,which is a considerable factor for WEC design.The influences of BHF mounted on the platform are revealed in both statistic and frequency spectral ways.The results of experiments give a guide for SPB design aiming to support BHF-WEC.

波浪能发电装置的鹰式吸波浮体研究

为更好地开发利用波浪能,以“南鲲”号波浪能发电装置为例,对其中用于捕获波浪能的鹰式吸波浮体进行研究。阐述波浪能发电装置的发电原理,其先采用鹰式吸波浮体捕获波浪能,推动液压缸做功,再将产生的液压能转化为电能。阐述波浪能捕获装置鹰式吸波浮体的组成,以及各组成部分的设计要点和工艺特点;结合该装置各组成部分的工作原理详细分析鹰式吸波浮体在俘获波浪能方面的有效性。

鹰式波浪能发电装置发电系统研究

文章首先对鹰式波浪能发电装置能量转换系统进行分类,分析了各系统的组成及工作原理,设计了一种液压式和直驱式组合的发电系统,通过模型试验优化了系统中的参数配置,提高了能量转换效率,最后通过实海况试验验证了"鹰式一号"波浪能发电装置的发电系统设计方案的可行性。

100kW一基多体漂浮鹰式波浪能发电装置模型试验研究

一基多体漂浮鹰式波浪能装置是一种新型的利用波浪发电的离岸漂浮式波浪能装置群,该波浪能发电装置是对已经成功发电的"鹰式I号"波浪能装置的改进优化。文中介绍的一基多体漂浮鹰式波浪能装置由4个鹰头吸波浮体、浮力舱、波浪能母船(水下附体)、半潜船、能量转换系统、锚泊系统等组成。该波浪能装置特殊设计为4个鹰头吸波浮体对称安装在一个波浪能母船上,共享能量转换系统和锚泊系统。通过一系列水槽模型试验,获得匹配各个波浪要素最优负载,测得模型在不同波浪要素下的一、二级能量转换效率,以及锚泊系统的受力。试验结果表明,模型具有良好的水动力学性能,模型俘获波浪能的能力并不受入射波的来浪方向影响,锚泊系统对模型起到了稳固、提高波浪能俘获效率的作用。

100 kW鹰式波浪能发电装置“万山号”实海况试验

鹰式装置"万山号"为一大型漂浮式波浪能发电装置,装置采用2套独立并行的液压系统将不稳定的波浪能转换为相对稳定的电能,系统配置4台由液压马达驱动的30 kW永磁发电机,在不同浪况下分级启动发电。2015年11月～2016年6月,"万山号"在珠海万山海域已开展不同海况的实海况试验,海试经历小浪、中浪、大浪等多种环境动力输入,取得一系列试验数据和成果。根据已获的阶段成果,总结出改进措施,后续"万山号"将优化升级现有系统,扩展太阳能发电及海水淡化系统,并在开阔海域开展长期实海况试验,持续提高鹰式波浪能转换装置的可靠性、转换效率、环境适应性和经济性。

“鹰式一号”波浪能发电装置研究

为了在波浪能流密度较低的中国海域开发利用波浪能,研发了具有半潜驳特征的鹰式波浪能转换装置。以成功实现了在实海况条件下的稳定运行的"鹰式一号"波浪能发电装置为实例,首先分别介绍了装置总体的三个组成部分,并指出了各部分的设计要点;其次,阐述了能量转换系统研究重点转换原理、液压自治控制器的功能;再次,通过对比传统锚泊系统与装置采用的蓄能型锚泊系统,表明后者可有效地避免锚链断裂和走锚;最后,展示了实海况试验的图片资料,分析了大量试验数据,结果表明,"鹰式一号"波浪能发电装置实现了将高频不稳定的波浪能转换为相对稳定的电能的目标。

鹰式波浪能发电装置水动力学性能分析及优化

根据牛顿第二定律,对鹰式波浪能装置多个浮体进行了力学分析,基于微波理论,通过每个浮体之间三种模态的运动耦合,建立了流体力、阻尼力、铰接力、静水回复力等内外力之间的力学方程组。通过以运动浮体为边界条件求解多个浮体的水动力学参数,代入方程组中计算求得最优外加阻尼和最优俘获宽度比,从而优化设计方案,得到此时各浮体在纵荡、垂荡和纵摇三种运动模态下的位移幅值,以及阻尼力、铰接力、液压缸运动速度等相关参数。研究成果为鹰式波浪能装置的设计及制造提供了理论参考和依据。

波浪能发电技术应用发展现状及方向

海洋波浪能是取之不尽、用之不竭的清洁能源。波浪能发电技术日趋成熟,形式也多种多样,从波浪能发电技术分类着手,对国内外波浪能发电技术应用现状进行了综述和评价,分析了波浪能发电技术应用的发展方向,最后指出海洋能利用的意义和前景。