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1.
《Oceanic Engineering, IEEE Journal of》2009,34(2):123-127
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点吸收式波能转换装置是具有较好应用前景的一种波浪能开发利用装置,其参数设计直接影响到波浪能开发利用的可行性与有效性。作者针对青岛斋堂岛目标海域海况,通过数值模拟首先应用单因素敏感性分析法分析了双浮子点吸收式波能转换装置的结构尺寸、锚固形式、波流夹角、PTO阻尼、PTO刚度等参数对装置俘能功率的独立影响规律。之后考虑多参数的综合影响,通过运用稳健设计方法,以上述参数为控制因子并确定合理的变动水准,将俘能功率作为评价标准,选取合理的正交实验L矩阵,得到了不同参数组合情况下的装置俘能功率并进行统计分析。结果表明,浮子尺寸、PTO阻尼、波流夹角对装置俘能功率影响较大,而PTO刚度、锚链与铅垂线夹角、锚链与波浪在水平面内的夹角对俘能功率影响不明显。提出的参数研究方法可为其他海域点吸收式波能转换装置参数设计提供参考。 相似文献
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Dynamic analysis of wave energy converter by incorporating the effect of hydraulic transmission lines 总被引：1，自引：0，他引：1
A heaving-buoy wave energy converter equipped with hydraulic power take-off is studied in this paper. This wave energy converter system is divided into five subsystems: a heaving buoy, hydraulic pump, pipelines, non-return check valves and a hydraulic motor combined with an electric generator. A dynamic model was developed by considering the interactions between the subsystems in a state space form. The transient pressures caused by starting/stopping the buoy or closing/opening the check valves were predicted numerically using the established model. The simulation results show that transmission line dynamics play a dominant role in the studied wave energy converter system. The length of the pipeline will not only affect the amplitude of the transient pressures but also affect the converted power. The variation of the time-averaged converted electric power with the pipeline length is estimated using the simulation method for the buoy exposed to one irregular sea state. Finally, it is suggested how reduced power efficiency due to the pipelines may be ameliorated. 相似文献
4.
This paper concerns the design of feedback control systems to maximize power generation of a wave energy converter (WEC) in a random sea. In the literature on WEC control, most of the proposed feedback controllers fall into three categories. Many are static; i.e., they extract power by imposing an equivalent damping or resistive load on the power take-off (PTO) devices. Others are dynamic and are designed to maximize power generation at all frequencies, which results in an anticausal feedback law. Other dynamic control design methods are causal, and are tuned to achieve the anticausal performance at only a single frequency. By contrast, this paper illustrates that the determination of the true optimal causal dynamic controller for a WEC can be found as the solution to a nonstandard linear quadratic Gaussian (LQG) optimal control problem. The theory assumes that the control system must make power generation decisions based only on present and past measurements of the generator voltages and/or velocities. It is shown that unlike optimal anticausal control, optimal causal control requires knowledge of the stationary spectral characteristics of the random sea state. Additionally, it is shown that the efficiency of the generator factors into the feedback synthesis. The theory is illustrated on a linear dynamical model for a buoy-type WEC with significant resonant modes in surge and pitch, and equipped with three spatially-distributed generators. 相似文献
5.
Wave energy fluctuating a great deal endangers the security of power grid especially micro grid in island. A DC nano grid supported by batteries is proposed to smooth the output power of wave energy converters (WECs). Thus, renewable energy converters connected to DC grid is a new subject. The characteristics of WECs are very important to the connection technology of HPTO type WECs and DC nano grid. Hydraulic power take-off system (HPTO) is the core unit of the largest category of WECs, with the functions of supplying suitable damping for a WEC to absorb wave energy, and converting captured wave energy to electricity. The HPTO is divided into a hydraulic energy storage system (HESS) and a hydraulic power generation system (HPGS). A primary numerical model for the HPGS is established in this paper. Three important basic characteristics of the HPGS are deduced, which reveal how the generator load determines the HPGS rotation rate. Therefore, the connector of HPTO type WEC and DC nano grid would be an uncontrollable rectifier with high reliability, also would be a controllable power converter with high efficiency, such as interleaved boost converter-IBC. The research shows that it is very flexible to connect to DC nano grid for WECs, but bypass resistance loads are indispensable for the security of WECs.. 相似文献
6.
Floating oscillating bodies constitute a large class of wave energy converters, especially for offshore deployment. Usually the Power-Take-Off (PTO) system is a directly linear electric generator or a hydraulic motor that drives an electric generator. The PTO system is simplified as a linear spring and a linear damper. However the conversion is less powerful with wave periods off resonance. Thus, a nonlinear snap-through mechanism with two symmetrically oblique springs and a linear damper is applied in the PTO system. The nonlinear snap-through mechanism is characteristics of negative stiffness and double-well potential. An important nonlinear parameter is defined as the ratio of half of the horizontal distance between the two springs to the original length of both springs. Time domain method is applied to the dynamics of wave energy converter in regular waves. And the state space model is used to replace the convolution terms in the time domain equation. The results show that the energy harvested by the nonlinear PTO system is larger than that by linear system for low frequency input. While the power captured by nonlinear converters is slightly smaller than that by linear converters for high frequency input. The wave amplitude, damping coefficient of PTO systems and the nonlinear parameter affect power capture performance of nonlinear converters. The oscillation of nonlinear wave energy converters may be local or periodically inter well for certain values of the incident wave frequency and the nonlinear parameter , which is different from linear converters characteristics of sinusoidal response in regular waves. 相似文献
7.
The energy efficiency of ocean-going vessels can be increased through various operational considerations, such as improved cargo arrangements and weather routing. The first step toward the goal of maximizing the energy efficiency is to analyze how the ship's powering performance changes under different operational settings and weather conditions. However, existing analytical models and empirical methods have limitations in reliably estimating the powering performance of full-scale ships in real operating conditions. In this study, machine learning techniques are employed to estimate the powering performance of a full-scale ship by constructing regression models using the ship's operational data. In order to minimize the risk of overfitting in the regression process, domain knowledge based on physical principles is combined into the regression models. Also, the uncertainty of the estimated performance is evaluated with consideration of the environmental uncertainties. The obtained regression models can be used to predict the ship speed and engine power under different operational settings and weather conditions. 相似文献
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波浪能发电装置的波能转换通常分为两级能量转换:第一级能量转换是波浪作用下波浪能装置部件发生相对运动驱动PTO做功捕获波浪能;第二级能量转换为将捕获的波浪能转换为电能。其中一级波浪能转换系统的优化设计是提高波浪能装置能量转换效率的重要手段和关键技术。波浪作用下波浪能装置的运动与PTO做功运动相互耦合和影响,本文通过对不同波浪要素环境下、不同PTO阻尼下波浪能装置的频域运动模拟,以迎波宽度比为尺度对波浪能装置的一级能量转换系统进行优化设计,获得波浪能装置的最优做功阻尼,为实型装置负载加载设计提供设计依据,提高波浪能装置能量转化效率。鹰式一号波浪能装置的实海况运动证明,通过对一级能量转换系统的优化设计,能够有效提高装置的发电效率和提高装置对波浪响应频带宽度。 相似文献
10.
An analytical theory is developed to study the effects of a coaxial tube-sector-shaped supporting structure on the conversion efficiency of a suspended, circular OWC converter. An eigen-function expansion method is employed in a cylindrical coordinate system to study wave interaction with an OWC converter in finite depth of water. Effects of the supporting structure, OWC dimensions, wave direction on energy conversion efficiency, and optimization of power-takeoff devices are discussed. Our results show that the coaxial tube-sector-shaped support with an opening in the range of π/2–5π/4 can significantly increase the conversion efficiency and widen the frequency range over which the conversion efficiency is high. 相似文献
11.
U. A. Korde 《Ocean Engineering》1990,17(6)
A possible scheme for utilizing ocean wave energy to generate a high power laser is examined. Such a laser can be used (i) unguided communication under water or through the atmosphere, and (ii) in spacecraft propulsion. The natural frequencies and the frequency response of the proposed two degree-of-freedom primary energy converter are obtained by using Lagrange's equations. Further, it is shown that the basic principle used in primary energy conversion can be developed into a mechanism for roll stabilization of marine vessels. 相似文献
12.
A combined wind and wave energy converter concept, named STC concept was proposed. Model tests were performed in terms of operational and survival modes. Water entry and exit phenomena as well as green water on deck were observed during the survivability model tests. In this paper, a nonlinear numerical model based on a blended station-keeping potential-flow solver with a local impact solution for bottom slamming events and an approximated model for the water shipped on the deck is proposed to simulate these nonlinear phenomena. Physical investigation of the water entry and exit process was firstly carried out and uncertainty analysis of the model test results were performed. Numerical comparisons between the nonlinear solver and model test results are then performed in terms of mean, wave frequency and double wave frequency motion response components. The slamming and green water involved in the water entry process are specially investigated, in terms of the physical evolution and the effects on the dynamic motion responses. The validation work on the occurrence of slamming and water on deck as well as the slamming pressure are performed. 相似文献
13.
An operational passive sonar is required to detect signals from sources, which are subject to spatial and temporal coherence losses via modifications by the ocean environment. Furthermore, these signals are to be detected in the presence of frequency-dependent correlated noise fields. For a system which employs splitbeam cross-correlation processing, the spatial and spectral properties of the signal and noise are of significant import. Therefore, the exact probability density and cumulative distribution functions of the N-sampled correlator outputs of a splitbeam broadband passive sonar are derived for the case of Gaussian inputs which are described by arbitrary cross-spectral density matrices. The validity of approximating the exact probability density function (pdf) as a Gaussian distribution is investigated. The effect of signal coherence loss and noise correlation on the detection performance is considered and the associated processing loss is expressed as a degradation factor within the detection threshold equation 相似文献
14.
Based on blade element momentum theory and generator characteristic test, a dynamic simulation model of 150 kW horizontal-axis tidal current turbine was established. The matching of the dynamic characteristics between the turbine and generator under various current velocities is studied, and the influence of the pitch angle on the matching is analyzed. For the problem of maximum power output in case of low current speed and limiting power in high current speed, the relation between optimal pitch angle and output power is analyzed. On the basis of dynamic characteristic analysis, the variable pitch control strategy is developed. The performance of the turbine under various tidal conditions is simulated. The research results show that the designed controller enables the turbine to operate efficiently under the condition of low current speed, and achieve the goal of limited power at high current speed. 相似文献
15.
U. A. Korde 《Ocean Engineering》1999,26(7):627
This paper studies reactive control of wave-energy devices in irregular waves. Estimates of future velocity of the primary energy converter are based on a time history of past velocity measurements, and prediction of incident waves is not attempted. Time–domain computations for a single-degree-of-freedom oscillating water column in irregular waves reveal that control is not optimal; but would enhance efficiency at low peak frequencies where energy-rich swells predominate, and allow appreciably smaller devices to fulfill a given power requirement. 相似文献
16.
摆式波能装置具有结构简单和转化效率高等特点,本文应用AQWA 软件基于势流理论对相交圆柱摆式波能装置进行了数值模拟研究,分析了轴间距比、结构阻尼、净浮力比、水深、波浪特性及吃水深度等主要参数对相交圆柱摆式波能装置俘获效率的影响,并与直板摆式波能装置的俘获效率进行了对比。结果表明：同样条件下,相交圆柱摆式波能装置往往比直板摆式波能装置的俘获效率更高;在研究范围内,轴间距比越大俘获效率越高;潮汐导致的水深变化对底铰摆式波能装置的俘获效率具有明显的影响,在工程应用中应采取适当的措施进行处理。 相似文献
17.
《中国海洋工程》2017,(5)
A novel floating pendulum wave energy converter(WEC) with the ability of tide adaptation is designed and presented in this paper.Aiming to a high efficiency,the buoy's hydrodynamic shape is optimized by enumeration and comparison.Furthermore,in order to keep the buoy's well-designed leading edge always facing the incoming wave straightly,a novel transmission mechanism is then adopted,which is called the tidal adaptation mechanism in this paper.Time domain numerical models of a floating pendulum WEC with or without tide adaptation mechanism are built to compare their performance on various water levels.When comparing these two WECs in terms of their average output based on the linear passive control strategy,the output power of WEC with the tide adaptation mechanism is much steadier with the change of the water level and always larger than that without the tide adaptation mechanism. 相似文献
18.
A novel floating pendulum wave energy converter (WEC) with the ability of tide adaptation is designed and presented in this paper. Aiming to a high efficiency, the buoy''s hydrodynamic shape is optimized by enumeration and comparison. Furthermore, in order to keep the buoy''s well-designed leading edge always facing the incoming wave straightly, a novel transmission mechanism is then adopted, which is called the tidal adaptation mechanism in this paper. Time domain numerical models of a floating pendulum WEC with or without tide adaptation mechanism are built to compare their performance on various water levels. When comparing these two WECs in terms of their average output based on the linear passive control strategy, the output power of WEC with the tide adaptation mechanism is much steadier with the change of the water level and always larger than that without the tide adaptation mechanism. 相似文献
19.
The oscillating water column (OWC) device is in a leading position for wave power extraction but has not achieved fully commercial at the current stage. In addition to enhancing the OWC performance, installing OWCs on floating breakwaters, which owns the merits of both cost-sharing and offshore power supply, is a practicality with high economic viability. In this study, a series of wave-flume experiments were conducted in regular waves to examine the wave power extraction of a floating box-type breakwater with dual pneumatic chambers. The flow characteristics of the orifices used to simulate the PTOs was pre-calibrated through another series of experiments, so the power extraction in this study can be obtained with only the pressure measurement. The effects of wave period, chamber draft, water depth and arrangement of chambers on the power extraction were examined. Our experimental results showed that the power extraction was mainly due to the water column oscillation inside the chamber, and differentiation in the designed natural periods of dual chambers could widen the efficiency bandwidth of power extraction. The front chamber always played the main role in power extraction and its natural period should be designed against the dominating period of the wave spectrum; in contrast, the power extraction of the rear chamber was only a supplement and its natural period should be designed against longer waves which were more easily transmitted, thus a PTO of small power capacity maybe more realistic. It was also worth noting that the water column oscillation was more dependent on the wave period rather than controlled by the wave scattering under different water depths. 相似文献
20.
The paper presents a concept of a wave energy converter and the numerical model to calculate the hydrodynamic responses in waves and the power produced by the power take off system. The system consists of an asymmetric floater with an interior U-tank partially filled with water and two lateral air chambers connected by a duct. The motion of the U-shaped oscillating water column, mainly induced by the rolling of the floater, forces the air through the duct where a Wells turbine is installed to absorb the wave energy.The wave-floater hydrodynamics is calculated with a Green's function panel method, while the oscillating water column motions hydro-mechanics are derived from the one-dimensional Euler's equation. The dynamics of the Wells turbine is realistically represented by one additional differential equation on the unknown air pressure fluctuation. This equation is derived assuming small amplitude motions of the water column and assuming the linear isentropic relation is valid for the air thermodynamics in the air chambers. The Wells turbine is characterized by a drastic drop of efficiency above a critical pressure value due to stalling on the blades. The effect of a by-pass valve to prevent stalling is introduced in the numerical model in a simplistic way. The numerical model is implemented and tested for a wave energy converter with a displacement of 1150 t, including 490 t for the interior water column, and an installed turbine with 2.3 m of diameter. An analysis of the influence of changing different design parameters on the system efficiency is also presented. 相似文献