scholarly journals Enhanced power absorption of a point absorber wave energy converter using a tuned inertial mass

2020 ◽  
Author(s):  
Ruriko Haraguchi ◽  
Takehiko Asai
Keyword(s):  
Power Generation ◽  
Energy Absorption ◽  
Wave Energy ◽  
Inertial Mass ◽  
Wave Energy Converter ◽  
Primary System ◽  
Energy Converter ◽  
Power Absorption ◽  
Point Absorber ◽  
Power Generation Performance

A novel point absorber wave energy converter with a tuned inertial mass (TIM), which is capable of significantly increasing the energy absorption and broadening the effective bandwidth, is proposed in this paper. The mechanism of the TIM has originally been introduced in the field of civil engineering as a passive energy absorber for structures subjected to external loadings such as earthquakes. It relies on attaching an additional tuning spring and a rotational inertial mass to the primary system, to improve the energy absorption performance by amplifying the displacement of the damper. Thus, considering typical point absorbers modeled as a mass-spring-dashpot system similar way to civil structures, the application of the TIM to wave energy converters can be expected to have a significant effect. In this paper, numerical investigation on the power generation performance of a point absorber with the TIM is conducted under random sea waves. The amplitude response and power generation performance are compared with the conventional point absorber, considering both non-resonant and resonant buoy cases. It is shown that by properly designing the tuning spring stiffness and generator damping, the rotation of the generator can be amplified compared to the buoy, increasing the power absorption drastically.

Power Absorption Modeling and Optimization of a Point Absorbing Wave Energy Converter Using Numerical Method

2014 ◽  
Vol 136 (2) ◽  
Author(s):  
Jeremiah Pastor ◽  
Yucheng Liu
Keyword(s):  
Wave Energy ◽  
Wave Energy Converter ◽  
Domain Model ◽  
Boundary Element Methods ◽  
Damping Coefficient ◽  
Energy Converter ◽  
Incoming Wave ◽  
Power Absorption ◽  
Point Absorber ◽  
Spring Force

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.

scholarly journals Numerical evaluation of a two-body point absorber wave energy converter with a tuned inerter

2020 ◽  
Author(s):  
Takehiko Asai ◽  
Keita Sugiura
Keyword(s):  
Power Generation ◽  
Wave Energy ◽  
Structural Control ◽  
Resonance Effect ◽  
Wave Energy Converter ◽  
Energy Converter ◽  
Peak Period ◽  
Point Absorber ◽  
Linear Damping ◽  
Body Point

To increase the amount of energy captured from a vibrating buoy in the ocean with a simple mechanism, this paper proposes a two-body point absorber wave energy converter (WEC) with a tuned inerter. The tuned inerter mechanism consists of a spring, a linear damping element, and a component called inerter. This mechanism was originally proposed in the field of civil engineering as a structural control device which can absorb energy from vibrating structures effectively by taking advantage of the resonance effect of the inerter part. In addition to this mechanism where a generator is used as the linear damping element, the current of the generator for the power take-off system is controlled based on the algorithms proposed in literature to achieve further improvement of the power generation capability. In this research, a detailed analytical model of the proposed WEC is introduced and developed. Then the power generation performances of full scale WEC models are assessed through numerical simulation studies using WAMIT software and it is shown that the current controlled WEC with the proposed mechanism achieves 88% increase compared to the conventional one for the JONSWAP spectrum with 6 s peak period and 1 m significant wave height

scholarly journals Shallow water effects on wave energy converters with hydraulic power take-off system

2016 ◽  
Vol 7 (3) ◽  
pp. 108-117 ◽  
Author(s):  
Ashank Sinha ◽  
D Karmakar ◽  
C Guedes Soares
Keyword(s):  
Water Depth ◽  
Wave Energy ◽  
Wave Energy Converter ◽  
Energy Converter ◽  
Hydraulic Power ◽  
Power Absorption ◽  
Point Absorber ◽  
Effect Of Water ◽  
Wave Energy Converters ◽  
Energy Converters

The effect of water depth on the power absorption by a single heaving point absorber wave energy converter, attached to a hydraulic power take-off system, is simulated and analysed. The wave energy flux for changing water depths is presented and the study is carried out at a location in the north-west Portuguese coast, favourable for wave power generation. This analysis is based on a procedure to modify the wave spectrum as the water depth reduces, namely, the TMA spectrum (Transformation spectrum). The present study deals with the effect of water depth on the spectral shape and significant wave heights. The reactive control strategy, which includes an external damping coefficient and a negative spring term, is used to maximize power absorption by the wave energy converter. The presented work can be used for making decisions regarding the best water depth for the installation of point absorber wave energy converters in the Portuguese nearshore.

Time Domain Modeling and Power Output for a Heaving Point Absorber Wave Energy Converter

2014 ◽  
Author(s):  
Jeremiah Pastor ◽  
Yucheng Liu
Keyword(s):  
Frequency Domain ◽  
Wave Energy ◽  
Time Domain ◽  
Power Output ◽  
Time Domain Analysis ◽  
Domain Analysis ◽  
Wave Energy Converter ◽  
Energy Converter ◽  
Power Absorption ◽  
Point Absorber

This paper presents, assesses, and optimizes a point absorber wave energy converter (WEC) through numerical modeling, simulation, and analysis in 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.

scholarly journals A Shape Optimization Method of a Specified Point Absorber Wave Energy Converter for the South China Sea

Energies ◽  
2018 ◽  
Vol 11 (10) ◽  
pp. 2645 ◽  
Author(s):  
Yadong Wen ◽  
Weijun Wang ◽  
Hua Liu ◽  
Longbo Mao ◽  
Hongju Mi ◽  
...  
Keyword(s):  
South China Sea ◽  
Shape Optimization ◽  
Energy Absorption ◽  
South China ◽  
Wave Energy ◽  
Optimization Method ◽  
Wave Energy Converter ◽  
Energy Converter ◽  
Point Absorber ◽  
Energy Absorbing

In this paper, a shape optimization method of a truncated conical point absorber wave energy converter is proposed. This method converts the wave energy absorption efficiency into the matching problem between the wave spectrum of the South China Sea and the buoy’s absorption power spectrum. An objective function which combines these two spectra is established to reflect the energy absorbing efficiency. By applying Taguchi design, the frequency domain hydrodynamic analysis and the response surface method (RSM), the radius, cone angle and draft of the buoy are optimized. Since the significant influence of power take-off system (PTO) on energy absorption, the optimal PTO damping under random wave conditions is also studied. The optimal shape is acquired by maximizing the energy absorbing efficiency. Four types of performance and the influence of each geometrical parameter are also obtained. In addition, the cause of the trend of performance as well as the effects of adjusting the input parameters are analyzed. This study can provide guidance for the shape optimization of multi-parameter buoys.

scholarly journals A Piezoelectric Wave-Energy Converter Equipped with a Geared-Linkage-Based Frequency Up-Conversion Mechanism

Sensors ◽  
2020 ◽  
Vol 21 (1) ◽  
pp. 204
Author(s):  
Shao-En Chen ◽  
Ray-Yeng Yang ◽  
Guang-Kai Wu ◽  
Chia-Che Wu
Keyword(s):  
Power Generation ◽  
Wave Energy ◽  
Wave Motion ◽  
Wave Energy Converter ◽  
Gear Train ◽  
Piezoelectric Composite ◽  
Maximum Height ◽  
Resistive Load ◽  
Linkage Mechanism ◽  
Energy Converter

In this paper, a piezoelectric wave-energy converter (PWEC), consisting of a buoy, a frequency up-conversion mechanism, and a piezoelectric power-generator component, is developed. The frequency up-conversion mechanism consists of a gear train and geared-linkage mechanism, which converted lower frequencies of wave motion into higher frequencies of mechanical motion. The slider had a six-period displacement compared to the wave motion and was used to excite the piezoelectric power-generation component. Therefore, the operating frequency of the piezoelectric power-generation component was six times the frequency of the wave motion. The developed, flexible piezoelectric composite films of the generator component were used to generate electrical voltage. The piezoelectric film was composed of a copper/nickel foil as the substrate, lead–zirconium–titanium (PZT) material as the piezoelectric layer, and silver material as an upper-electrode layer. The sol-gel process was used to fabricate the PZT layer. The developed PWEC was tested in the wave flume at the Tainan Hydraulics Laboratory, Taiwan (THL). The maximum height and the minimum period were set to 100 mm and 1 s, respectively. The maximum voltage of the measured value was 2.8 V. The root-mean-square (RMS) voltage was 824 mV, which was measured through connection to an external 495 kΩ resistive load. The average electric power was 1.37 μW.

scholarly journals Passive Model Predictive Control on a Two-Body Self-Referenced Point Absorber Wave Energy Converter

Energies ◽  
2021 ◽  
Vol 14 (6) ◽  
pp. 1731
Author(s):  
Dan Montoya ◽  
Elisabetta Tedeschi ◽  
Luca Castellini ◽  
Tiago Martins
Keyword(s):  
Model Predictive Control ◽  
Predictive Control ◽  
Wave Energy ◽  
Power Flow ◽  
Linear Constraints ◽  
Wave Energy Converter ◽  
Control Technique ◽  
Computational Time ◽  
Energy Converter ◽  
Point Absorber

Wave energy is nowadays one of the most promising renewable energy sources; however, wave energy technology has not reached the fully-commercial stage, yet. One key aspect to achieve this goal is to identify an effective control strategy for each selected Wave Energy Converter (WEC), in order to extract the maximum energy from the waves, while respecting the physical constraints of the device. Model Predictive Control (MPC) can inherently satisfy these requirements. Generally, MPC is formulated as a quadratic programming problem with linear constraints (e.g., on position, speed and Power Take-Off (PTO) force). Since, in the most general case, this control technique requires bidirectional power flow between the PTO system and the grid, it has similar characteristics as reactive control. This means that, under some operating conditions, the energy losses may be equivalent, or even larger, than the energy yielded. As many WECs are designed to only allow unidirectional power flow, it is necessary to set nonlinear constraints. This makes the optimization problem significantly more expensive in terms of computational time. This work proposes two MPC control strategies applied to a two-body point absorber that address this issue from two different perspectives: (a) adapting the MPC formulation to passive loading strategy; and (b) adapting linear constraints in the MPC in order to only allow an unidirectional power flow. The results show that the two alternative proposals have similar performance in terms of computational time compared to the regular MPC and obtain considerably more power than the linear passive control, thus proving to be a good option for unidirectional PTO systems.

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