振荡水柱式波浪能供电浮标水动力学性能研究

提出一种振荡水柱式锥形中心管波浪能供电浮标。首先，介绍浮标的结构及工作原理，其次，设计3种模型方案。建立浮标在入射波下受迫运动的数学模型，进行数值模拟计算，获得浮标在设计工况下的附加质量、阻尼系数、波浪激励力、运动响应等水动力学参数。最后，通过物理模型试验，获得各设计方案在不同周期下的俘获宽度比，并与数值计算获得的俘获宽度比进行对比分析。结果显示：不同设计方案的浮标适应不同的水深条件，设计方案中模型1的俘获宽度比最大数值为47.8%。     

一种多浮体铰接式波浪能装置的运动分析与俘获特性研究

基于线性势流理论，利用总模态法对多浮体铰接波浪能装置“海星号”在波浪中的运动开展水动力学系数计算；然后基于矢量力学建立多浮体刚体运动学方程，并结合几何约束条件开展动态响应计算，获得最优俘获效率和最优负载阻尼；最后比较并分析“海星”波浪能装置的多浮体俘获效率，获得“海星”多浮体做功的俘获特性。研究表明：“海星”波浪能装置的多浮体四向迎波设计可拓宽装置最优俘获频带宽度，提高装置整体俘获效率；正向迎波与背向迎波俘获波浪能方式相比，小周期情况下，正向吸波浮体俘获效率较高，随着周期增大，正向吸波浮体俘获效率开始降低，背向吸波浮体俘获效率开始增大，极大周期情况下，正向吸波浮体和背向吸波浮体俘获效率趋于一致且趋近于零。     

锥形中心管浮标试验研究

该文研究了中心管结构对能量转化性能的影响,并得出提高波浪能俘获性能的若干方法。设计了3个不同直径的中心管模型进行试验。且进一步研究了锚系位置和喷嘴比对模型俘获性能的影响。试验结果表明,中心管面积占底面面积的比例与模型最高俘获宽度比有直接关系。锚链系于浮仓底部相对于其他位置,能使模型更加稳定,俘获效果更好。中心管最高俘获宽度比对应的喷嘴比为2%,且随着喷嘴比增大,通频带变宽。     

底铰摆式波浪能转换装置实验研究

通过理论分析和物理模型实验相结合的方法,系统研究底铰接摆式波浪能转换装置在双向和单向2种不同PTO阻尼作用下的最大功率及俘获效率等水动力性能,同时探究不同浮力摆摆板形式对装置输出功率的影响。实验结果表明:浮力摆在双向阻尼下,装置的能量转换效率和受力特性均优于单向阻尼作用时,建议对底铰摆式波能转换装置施加双向阻尼。     

直驱式波能装置振动及转换效率分析

波浪能利用装置一般是利用振动来获取波浪能量,如鸭式装置、点吸收式装置。点吸收技术是世界上目前研究得比较热门的一类波浪能利用技术,漂浮直驱式波能装置是点吸收技术的一种。文章首先通过物理过程分析,把由双圆柱浮体构成的漂浮直驱式波浪能装置当成一个双自由度振动系统,建立系统振动方程;然后,运用势流理论求解由双圆柱浮体的垂荡辐射问题和绕射问题,求解出振动分析所需要的水动力学参数。考虑波浪能装置通过粘性阻尼吸收波浪能,利用求得的水动力学参数,设定的外部阻尼和弹簧弹性系数,可求解出此情况下水面浮体和水下浮体的相对运动幅值,进而求得装置的转换效率。给定模型尺寸参数,在一些确定的外部阻尼值和弹簧弹性系数点,分别通过变化外部阻尼和弹簧弹性系数,分析装置的振动特性以及转换效率的变化,从而在不同波况下选择适合装置的外部阻尼系数和弹簧弹性系数。     

振荡滑杆式波能装置振动特性优化与试验

根据振动特性对振荡滑杆式波能转换系统进行优化,通过降低质量、增加弹性系数的方法减小吸波浮体运动与波浪的相位差,可实现波能捕获效率的提高。将优化前后的模型进行对比性试验,试验结果表明:低惯性波能转换装置水动力学响应明显优于普通惯性波能装置,波浪能俘获效率大幅增加,测得最优俘获宽度比由29.85%提升至51.73%,且对工作环境的适应性大大增强,能在不同波况下保持较高的能量转换效率。     

中心管底部形状对浮标波能转换性能影响的实验研究

为改善中心管振荡水柱式波力发电浮标的能量转换性能,对中心管底部设计了四4种模型并在造波水槽中进行实验研究。试验结果表明,直管型中心管俘获宽度比最小,实验测得最高为4.12%,底部有一定锥度的模型会提高俘获宽度比,目前实验最高为19.25%,并出现较高的双峰值,提高了通频带,峰值周期也随锥度的不同出现了移动。试验得到的较佳模型需要进一步优化和实验,为设计适应不同海况的发电浮标提供基础数据。     

后弯管模型多环节能量转换特性实验研究

后弯管（BBDB）技术从波浪能到电能的转换要经过多个环节,为提高后弯管技术能量转换性能,对一种新型的后弯管技术多环节阻尼形式展开了实验研究。水槽实验研究表明,在气流单向做功条件下,规则波下俘获宽度比（CWR）峰值为113.7%,随机波下CWR峰值为81.9%,而在气流双向做功时,规则波下CWR峰值为138.6%,随机波下CWR峰值为94.0%;相对于简单气孔阻尼模型,带有导叶、叶轮和发电机元件阻尼的试验模型的CWR稍高于简单纯气孔模型,两者CWR曲线变化的趋势接近。     

新型双浮体波浪能发电装置的频域分析与试验

针对海洋监测活动的需求,提出运用一种新型的双浮体波浪能发电装置(WEC),并应用基于三维势流理论的有限元软件AQWA对装置的垂荡特性进行了频域分析,即采用无阻尼的质量弹簧系统共振理论对能量转换装置(PTO)刚度和阻尼进行优化,分析了入射波浪频率和浮体初始吃水深度对装置的影响。结合我国渤海区域特定波况取相似因子为1∶15,对该双浮体波浪能发电装置进行了模型设计,并在华南理工大学造波水池进行试验,结果显示该装置在规则波作用下俘获宽度比达1.433,具有实际应用意义。     

一种漂浮铰接式波能装置的水动力学研究

主要研究包含水面浮体和水下浮体两部分的一种铰接式波能装置。由于其外形较复杂,为了计算得到波能装置的水动力学系数和波浪激励力,采用基于三维面元法的Hydrostar软件进行水动力学计算。对铰接式波能装置进行受力分析得到装置的力学方程。最后通过适当选取弹簧弹性系数和外部阻尼系数,可求得优化的水面浮体和水下浮体的相对运动幅度以及装置的俘获宽度比。     

单浮筒振荡浮子式波浪能装置的动力特性分析

针对振荡浮子式波浪能利用技术,提出一种单浮筒式波浪转换设计方案,对单浮筒随波浪的运动特性展开研究,将波浪能转换为振荡浮筒的摆动机械能,传递给PTO能量转换系统。通过采用Star-CCM流体仿真软件分析浮筒装置在不同PTO能量转换系统参数下的运动特性及受力情况,得到不同弹簧阻尼工况下浮筒装置的运动特性,以期为波浪能技术的装置结构优化及真实海况运行提供理论基础。     

Experimental and numerical comparisons of hydrodynamic responses for a combined wind and wave energy converter concept under operational conditions

The spar torus combination (STC) concept is a combined wind and wave energy converter concept that is composed of a spar floating wind turbine and a torus-shaped, heaving-body wave energy converter (WEC). The WEC is installed on the spar floater. Wave power can be absorbed by a power-take off (PTO) system through the relative heave motions between spar and torus. Numerical model was established to predict dynamic responses of the STC concept ​under different sea states. To validate the numerical model, a model test of the STC concept under operational conditions was performed. A two-body physical model at a 1:50 scaling ratio was built. A series of tests were performed to assess the performance of the concept. During the tests, different PTO damping levels were applied. When large power output was achieved, air compressibility of the PTO damper in the model matters, making relevant a suitable nonlinear PTO modeling in the numerical simulations. Wind conditions were considered to model the effect of the thrust force on the rotor using a wind drag disc. Numerical and experimental results are presented and compared. Good agreements are achieved.     

Wave‐current interaction effects on structural responses of floating offshore wind turbines

This paper proposes a model considering the wave‐current interactions in dynamic analyses of floating offshore wind turbines (FOWTs) and investigates the interaction effects on the FOWT responses. Waves when traveling on current are affected by the current, leading to frequency shift and shape modification. To include such interactions in FOWT analysis, which has not been considered by the researchers till date, a nonlinear hydrodynamic model for multicable mooring systems is presented that is able to consider the cable geometric nonlinearity, seabed contact, and the current effect. The mooring model is then coupled with a spar‐type FOWT model that handles the structural dynamics of turbine blades and tower, aerodynamics of the wind‐blade interaction, and wave‐current effects on the spar. The analytical wave‐current interaction model based on Airy theory considering the current effect is used in the computation of flow velocity and acceleration. Numerical studies are then carried out based on the NREL offshore 5‐MW baseline wind turbine supported on top of the OC3‐Hywind spar buoy. Two cases, (1) when the currents are favorable and (2) when the currents are adverse, are examined. Differences of up to 15% have been observed by comparing the cable fairlead tension obtained excluding and including the wave‐current interactions. In particular, when irregular waves interact with adverse current, a simple superposition treatment of the wave and the current effects seems to underestimate the spar motion and the cable fairlead tension. This indicates that the wave‐current interaction is an important aspect and is needed to be considered in FOWT analysis.     

A heaving point absorber‐based triboelectric‐electromagnetic wave energy harvester: An efficient approach toward blue energy

This paper presents a hybridized triboelectric‐electromagnetic generator based on heaving point absorbers to harvest the energy of water waves. The device consists of a cylindrical freestanding grating triboelectric generator (TENG) and a 3‐phase tubular electromagnetic generator (EMG). The proposed system incorporates a slider which is capable of moving through a stator under the motion of a floating buoy. The floating component can heave up and down while facing water waves without being affected by the wave direction. The performance of the TENG and EMG units and corresponding electrical outputs are evaluated under various structural, dynamical, and electrical conditions. It is shown that the number of segments in the TENG unit, phase number in the EMG unit, and motion frequency in both harvesters are the key elements in the outputs of the hybridized system. For the first time, the effect of irregular wave motion on the TENG harvester performance is systematically explored using a well‐known wave spectrum. Also, the performance of the hybridized system for charging a storage unit is evaluated in details. The presented energy harvester shows a great potential toward harvesting the energy of water waves as well as hydrodynamic sensing applications. In addition, this research provides a framework for the exploration of irregular wave motion in TENG‐based energy harvesters.     

Experimental investigation and ANN modeling on improved performance of an innovative method of using heave response of a non-floating object for ocean wave energy conversion

To convert wave energy into usable forms of energy by utilizing heaving body, heaving bodies (buoys) which are buoyant in nature and float on the water surface are usually used. The wave exerts excess buoyancy force on the buoy, lifting it during the approach of wave crest while the gravity pulls it down during the wave trough. A hydraulic, direct or mechanical power takeoff is used to convert this up and down motion of the buoy to produce usable forms of energy. Though using a floating buoy for harnessing wave energy is conventional, this device faces many challenges in improving the overall conversion efficiency and survivability in extreme conditions. Up to the present, no studies have been done to harness ocean waves using a non-floating object and to find out the merits and demerits of the system. In the present paper, an innovative heaving body type of wave energy converter with a non-floating object was proposed to harness waves. It was also shown that the conversion efficiency and safety of the proposed device were significantly higher than any other device proposed with floating buoy. To demonstrate the improvements, experiments were conducted with non-floating body for different dimensions and the heave response was noted. Power generation was not considered in the experiment to observe the worst case response of the heaving body. The device was modeled in artificial neural network (ANN), the heave response for various parameters were predicted, and compared with the experimental results. It was found that the ANN model could predict the heave response with an accuracy of 99%.     

Dynamics of offshore floating wind turbines—analysis of three concepts

This work presents a comprehensive dynamic–response analysis of three offshore floating wind turbine concepts. Models were composed of one 5 MW turbine supported on land and three 5 MW turbines located offshore on a tension leg platform, a spar buoy and a barge. A loads and stability analysis adhering to the procedures of international design standards was performed for each model using the fully coupled time domain aero‐hydro‐servo‐elastic simulation tool FAST with AeroDyn and HydroDyn. The concepts are compared based on the calculated ultimate loads, fatigue loads and instabilities. The loads in the barge‐supported turbine are the highest found for the three floating concepts. The differences in the loads between the tension leg platform–supported turbine and spar buoy–supported turbine are not significant, except for the loads in the tower, which are greater in the spar system. Instabilities in all systems also must be resolved. The results of this analysis will help resolve the fundamental design trade‐offs between the floating‐system concepts. Copyright © 2011 John Wiley & Sons, Ltd.     

实海况条件下磁流体波浪发电机的优化设计

以点吸收式波浪发电装置为例,考虑浮体和阻尼板在垂荡方向上的运动响应特性及磁流体发电机的发电特性,利用遗传算法优化不同规则波况下磁流体发电机的结构参数,得到装置投放于南海某岛屿附近时不同平均有效波高下的发电效率。然后,根据该岛屿全年波况的频率分布规律,计算得到全年发电量,年发电量最大时磁流体发电机结构参数最优。与传统按主波况进行结构参数优化相比,充分考虑不同平均有效波高的出现频率对装置输出功率的影响,对实海况条件下磁流体波浪发电装置的优化设计和经济效益的评估具有重要的指导意义。另外,磁流体波浪发电装置的启动波高低于1.0 m的行业标准,启动性能极好,可增加波浪的有效利用小时数,其极强的低海况响应能力尤其适合中国的低海况条件。     

Performance of OWC wave energy converters: influence of turbine damping and tidal variability

The performance of oscillating water column (OWC) systems depends on a number of factors in a complex manner. The objective of this work is to analyse the influence of the wave conditions, the damping caused by the turbine and the tidal level on the efficiency of the conversion from wave to pneumatic energy that occurs in the OWC chamber. To achieve this, a comprehensive experimental campaign is carried out, involving in total 387 tests of a model OWC under varying wave conditions (both with regular and irregular waves), damping coefficients and tidal levels. It is found that the damping exerted by the turbine is the factor that most affects the chamber efficiency—even more than the wave conditions. It follows that a proper selection of the turbine is crucial not only to the performance of the turbine itself but also to that of the chamber, which reflects the importance of the turbine–chamber coupling in OWC systems. The next factor in order of importance is the wave period. Finally, we find that the influence of the tidal level, which is examined in this work for the first time, is significant under certain conditions. Copyright © 2014 John Wiley & Sons, Ltd.