Point Absorber Wave Energy Converters in Regular and Irregular Waves with Time Domain Analysis (original) (raw)
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Journal of Marine Science Research and Oceanography, 2020
A discrete control of latching is used to increase the bandwidth of the efficiency of the Wave Energy Converters (WEC) in regular and irregular seas. When latching control applied to WEC it increases the amplitude of the motion as well as absorbed power. It is assumed that the exciting force is known in the close future and that body is hold in position during the latching time. A heaving vertical-cylinder as a point-absorber WEC is used for the numerical prediction of the different parameters. The absorbed maximum power from the sea is achieved with a three-dimensional panel method using Neumann-Kelvin approximation in which the exact initial-boundary-value problem is linearized about a uniform flow, and recast as an integral equation using the transient free-surface Green function. The calculated response amplitude operator, absorbed power, relative capture width, and efficiency of vertical-cylinder compared with analytical results.
Control of Wave Energy Converters for Maximum Power Absorption with Time Domain Analysis
Journal of Fundamentals of Renewable Energy and Applications, 2017
A discrete control of latching is used to increase the bandwidth of the efficiency of the Wave Energy Converters (WEC) in regular and irregular seas. When latching control applied to WEC it increases the amplitude of the motion as well as absorbed power. It is assumed that the exciting force is known in the close future and that body is hold in position during the latching time. A heaving vertical-cylinder as a point-absorber WEC is used for the numerical prediction of the different parameters. The absorbed maximum power from the sea is achieved with a three-dimensional panel method using Neumann-Kelvin approximation in which the exact initial-boundary-value problem is linearized about a uniform flow, and recast as an integral equation using the transient free-surface Green function. The calculated response amplitude operator, absorbed power, relative capture width, and efficiency of vertical-cylinder compared with analytical results.
Time domain prediction of power absorption from ocean waves with latching control
Renewable Energy, 2010
A three-dimensional panel method using Neumann-Kelvin method is presented for the transient wavebody interaction problems in order to absorb maximum power from the sea. The exact initial boundary value problem is linearized about a uniform flow, and recast as an integral equation using the transient free-surface Green function. The hydrodynamics part of the solution including radiation and diffraction problem is solved as impulsive velocity problem. A discrete control of latching is used to increase the bandwidth of the efficiency of the wave energy converters (WEC). When latching control is applied to WEC in the case of off-resonance condition it increases the amplitude of the motion as well as absorbed power. It is assumed that the exciting force is known in the close future and that body is hold in position during the latching time. A heaving hemisphere as a point-absorber WEC is used for the numerical prediction of the different parameters. The calculated hydrodynamics coefficients, response amplitude operator, absorbed power, relative capture width of this device compared with analytical and other published results.
This paper presents, assesses, and optimizes a point absorber wave energy converter (WEC) through numerical modeling, simulation, and analysis in both frequency and time domain. Wave energy conversion is a technology especially suited for assisting in power generation in the offshore oil and gas platforms. A linear frequency domain model is created to predict the behavior of the heaving point absorber WEC system. The hydrodynamic parameters are obtained with AQWA, a software package based on boundary element methods. A linear external damping coefficient is applied to enable power absorption, and an external spring force is introduced to tune the point absorber to the incoming wave conditions. The external damping coefficient and external spring forces are the control parameters, which need to be optimized to maximize the power absorption. Two buoy shapes are tested and a variety of diameters and drafts are compared. Optimal shape, draft, and diameter of the model are then determined to maximize its power absorption capacity. Based on the results generated from the frequency domain analysis, a time domain analysis was also conducted to derive the responses of the WEC in the hydrodynamic time response domain. The time domain analysis results allowed us to estimate the power output of this WEC system.
This paper presents, assesses, and optimizes a point absorber wave energy converter (WEC) through numerical modeling, simulation, and analysis. Wave energy conversion is a technology uniquely suited for assisting in power generation in the offshore oil and gas platforms. A linear frequency domain model is created to predict the behavior of the heaving point absorber WEC system. The hydrodynamic parameters are obtained with AQWA, a software package based on boundary element methods. A linear external damping coefficient is applied to enable power absorption and an external spring force is introduced to tune the point absorber to the incoming wave conditions. The external damping coefficient and external spring forces are the control parameters, which need to be optimized to maximize the power absorption. Two buoy shapes are tested and a variety of diameters and drafts are compared. Optimal shape, draft, and diameter of the model are then determined to maximize its power absorption capacity. Downloaded From: http://energyresources.asmedigitalcollection.asme.org/ on 05/23/2014 Terms of Use: http://asme.org/terms
Ocean Engineering, 2020
A parametric optimization study is carried out to find an optimal design to capture the maximum energy in a target area off the Turkish coast of the Black Sea. A heaving point absorber wave energy converter is analyzed by taking into account different float geometries with various dimensions and several hydraulic Power TakeOff parameters. The calculations are carried out in time domain by modeling each sea state observed in the target area. The effects of the geometry, mass, and the dimensions of the floats and the parameters of the Power TakeOff system on the energy generated from the waves are investigated and discussed. The analyses showed that the maximum pressure of the hydraulic accumulator, the cross-sectional area of the hydraulic piston, and the flow rate of the hydraulic fluid can be selected to combine the values of those which the WEC performs best in the sea state that possesses nearly similar energy as the annual average of all sea states observed in the target area. The cost of energy is also evaluated and it is found that the most economical WEC differs by float geometry.
International Journal of Marine Engineering Innovation and Research
⎯ this research investigates the optimal buoy shape for a conceptual point absorber Wave Energy Converter (WEC) for harnessing low amplitude sea waves characteristic of the Gulf of Guinea coast. It has been established that shape of buoy is one of the main parameter affecting the efficiency of a point absorber WEC. Based on best buoy shapes as reported in literature, two shapes are selected for comparison: cone-cylinder composite buoy and Concave wedge shaped buoy. The WEC's buoy and the power take off were mathematically modelled as a mass-spring-damper system. The buoys hydrodynamic coefficients were computed using strip theory, while the simulation in the time domain was executed using MATLAB. Impute parameters referred to as the sea states, in five levels, were described by the significant wave height Hs and the corresponding energy period Te, typical of the gulf. Output parameters are displacement, velocity, acceleration and force of the buoys, as well as the instantaneous power output of the WEC. For the levels considered, the optimum sea state for the two buoys peaked at level 4 (Hs = 1.5 m, Te = 14 s), with concave wedge buoy having an optimal power output of 8 kW while that of cone-cylinder being 3.7 kW. For the other levels the wedge buoy also consistently gives relatively greater power output than the cone cylinder buoy.
Control of a point absorber wave energy converter
International Journal of Renewable Energy Research, 2019
This paper deals with the optimization of a bottom fixed wave energy converter of heaving point absorber type (PAWEC). The PAWEC consists of a unique horizontal cylinder of radius R and length L, connected to the seabed through an extensible Power Take Off device. In this work, an original control strategy is used in order to optimize the PAWEC. The proposed method links the damping coefficient of the power take off device to the relative velocity between the buoy and the wave. This study focus on the comparison of the two cases where a passive control is adopted and where the damping coefficient is a constant. The performance of the WEC in different wave conditions for each of the two cases is investigated. The results show that the recovered energy is considerably increased owing to the adaptation of the damping coefficient with the buoy speed
Development and Testing of a Point Absorber Wave Energy Conversion
Volume 5: Ocean Space Utilization; Ocean Renewable Energy, 2011
Wave energy conversion as a means for small scale energy production is approaching commercial viability. This paper presents the undergoing development of a wave energy conversion device at the University of Hawaii at Manoa. The device is a three part point absorber with two buoys, one floating and absorbing incoming waves; the other maintaining tension on the third mechanism, the submerged power-takeoff unit. This design is discussed as three concept configurations for WEC construction. The analytical solution is developed, and the buoys response is computed due to a selected and analyzed sea-state.
Buoy Analysis in a Point-Absorber Wave Energy Converter
IEEE Journal of Oceanic Engineering
In this paper, a single-body point absorber system is analyzed to enhance its power absorption performance. The wave energy converter consists of a single floating body coupled to a direct-drive power takeoff system placed on the seabed. The geometry of a cylindrical buoy with large draft is modified, obtaining a particular geometry that is used to enhance the power absorption of the wave converter at a given site and at a finite depth. A numerical analysis tool (NEMOH) is used to obtain the buoy's frequency-dependent hydrostatic parameters; in addition, the buoy's dimensions are parameterized to tune the natural frequency of the oscillating system toward the frequency of dominant incident waves, thus enhancing wave power absorption for a specific wave frequency range. Furthermore, the damping influence of the power takeoff system on the performance of the wave energy converter is also considered.