scholarly journals Multi-Objective Optimization of a Pitch Point Absorber Wave Energy Converter

Water ◽  
2019 ◽  
Vol 11 (5) ◽  
pp. 969 ◽  
Author(s):  
Rezvan Alamian ◽  
Rouzbeh Shafaghat ◽  
Mohammad Reza Safaei
Keyword(s):  
Wave Energy ◽  
Wave Energy Converter ◽  
Multi Objective Optimization ◽  
Energy Converter ◽  
The Caspian Sea ◽  
Multi Objective ◽  
Point Absorber ◽  
Wave Characteristics ◽  
Multi Objective Genetic Algorithm ◽  
Absorbed Power

In this paper, a pitch point absorber wave energy converter (WEC) is selected in order to be optimized for the wave characteristics of the Caspian Sea. The optimization process is a multi-objective optimization. For achieving the optimal WEC, mean absorbed power should be maximized while the construction cost should be minimized. The submerged surface area of the WEC is selected as a cost parameter. The amount of mean absorbed power depends on the installation site and also the shape of the WEC. For optimizing the shape of the WEC, various shapes are considered which are categorized into three different sections. A multi-objective genetic algorithm is used for optimization of the model, and the NEMOH software is used to simulate the wave-body interaction. The results show that the bottom flat and upside chamfered geometry with X:Y ratio of 10:1 is the best geometry for the desired application. Comparing the results from the final optimized shape with the optimized basic parallelepipedic hull shape reveals that much more extractable power can be achieved with less cost.

An empirical evaluation of the sea depth effects for various wave characteristics on the performance of a point absorber wave energy converter

2017 ◽  
Vol 137 ◽  
pp. 13-21 ◽  
Author(s):  
Rezvan Alamian ◽  
Rouzbeh Shafaghat ◽  
Mostafa Safdari Shadloo ◽  
Rasoul Bayani ◽  
Amir Hossein Amouei
Keyword(s):  
Wave Energy ◽  
Empirical Evaluation ◽  
Wave Energy Converter ◽  
Energy Converter ◽  
Point Absorber ◽  
Wave Characteristics ◽  
Depth Effects

scholarly journals A practical design procedure for initial sizing of heaving point absorber wave energy converters

2021 ◽  
Vol 1201 (1) ◽  
pp. 012018
Author(s):  
M B Jouybari ◽  
Y Xing
Keyword(s):  
Wave Energy ◽  
Design Procedure ◽  
The Body ◽  
Wave Energy Converter ◽  
Body Volume ◽  
Energy Converter ◽  
Point Absorber ◽  
Wave Energy Converters ◽  
Practical Design ◽  
Absorbed Power

Abstract Designing a wave energy converter with the proper size has always been challenging since it is a trade-off between many factors including cost, practicality, and energy output. In this paper a practical design procedure for sizing of heaving point absorbers wave energy converters is presented. Size can be represented by the body volume. Budal power bounds are deployed to obtain the body volume and annual mean absorbed power of the wave energy converter. Budal power bounds are determined for each sea state. Aiming a specific power capture ratio, several sets of design sea states with related design volume and annual mean absorbed power are defined. With the design objective of maximizing the ratio of mean power to submerged volume, and considering suitable design constraints, the best size is obtained. The proposed procedure will be then deployed for a case study and the design will be compared with an existing similar point absorber. The results show that the mean absorbed power does not depend on the size but is a function of selected sea states. Furthermore, the comparison study reveals that the proposed design procedure yields reasonable power characteristics.

Experimental Assessment of the Performance of CECO Wave Energy Converter in Irregular Waves

2019 ◽  
Vol 141 (4) ◽  
Author(s):  
Claudio A. Rodríguez ◽  
Paulo Rosa-Santos ◽  
Francisco Taveira-Pinto
Keyword(s):  
Wave Energy ◽  
Transfer Functions ◽  
Wave Energy Converter ◽  
Irregular Waves ◽  
Energy Converter ◽  
Energy Harvesters ◽  
Point Absorber ◽  
Model Scale ◽  
Absorbed Power ◽  
Incident Waves

The performance assessment of a wave energy converter (WEC) is a key task. Depending on the layout of the WEC system and type of power take-off (PTO) mechanism, the determination of the absorbed power at model scale involves several challenges, particularly when the measurement of PTO forces is not available. In irregular waves, the task is even more difficult due to the random character of forces and motions. Recent studies carried out with kinetic energy harvesters (KEH) have proposed expressions for the estimation of the power based only on the measured motions. Assuming that the WEC behaves as a KEH at model scale, the expressions for power estimation of KEHs have been heuristically adapted to WECs. CECO, a floating-point absorber, has been used as case study. Experimental data from model tests in irregular waves are presented and analyzed. Spectral analyses have been applied to investigate the WEC responses in the frequency domain and to derive expressions to estimate the absorbed power in irregular waves. The experimental transfer functions of the WEC motions demonstrated that the PTO damping is significantly affected by the incident waves. Based on KEH approach's results, absorbed power and PTO damping coefficients have been estimated. A linear numerical potential model to compute transfer functions has been also implemented and calibrated based on the experimental results. The numerical results allowed the estimation of combined viscous and losses effects and showed that although the KEH approach underestimated the absorbed power, qualitatively reproduced the WEC performance in waves.

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.

High-performance and robust bistable point absorber wave energy converter

2021 ◽  
pp. 108767
Author(s):  
Ru Xi ◽  
Haicheng Zhang ◽  
DaolinXu ◽  
Huai Zhao ◽  
Ramnarayan Mondal
Keyword(s):  
Wave Energy ◽  
High Performance ◽  
Wave Energy Converter ◽  
Energy Converter ◽  
Point Absorber

Optimization of a Torus-Shaped Wave Energy Converter Attached to a Hinged Arm

2021 ◽  
Author(s):  
Mojtaba Kamarlouei ◽  
Thiago S. Hallak ◽  
Jose F. Gaspar ◽  
Miguel Calvário ◽  
C. Guedes Soares
Keyword(s):  
Genetic Algorithm ◽  
Objective Function ◽  
Wave Energy ◽  
Wave Energy Converter ◽  
Prime Mover ◽  
Optimal Result ◽  
Energy Converter ◽  
Sea State ◽  
Absorbed Power ◽  
Spring System

Abstract This paper presents the adaptation of a torus wave energy converter prime mover to an onshore or nearshore fixed platform, by a hinged arm. An optimization code is developed to obtain the best torus and arm geometry, as well as the power take-off parameters, taking as objective function the maximization of total wave absorbed power. In this paper, the power take-off system is modelled as a simplified damper and spring system, where the parameters are optimized for the phase control of the wave energy converter in each sea state, whereas the optimization process is performed with a genetic algorithm. Finally, the optimal result for the productive sea state indicates that the absorbed power is relatively considerable while a better survivability performance is expected from a torus wave energy converter compared to a conventional truncated prime mover.

scholarly journals Linear and nonlinear hydrodynamic models for dynamics of a submerged point absorber wave energy converter

2020 ◽  
Vol 197 ◽  
pp. 106828 ◽  
Author(s):  
Benjamin W. Schubert ◽  
William S.P. Robertson ◽  
Benjamin S. Cazzolato ◽  
Mergen H. Ghayesh
Keyword(s):  
Wave Energy ◽  
Wave Energy Converter ◽  
Hydrodynamic Models ◽  
Energy Converter ◽  
Point Absorber ◽  
Linear And Nonlinear

scholarly journals Loads on a Point-Absorber Wave Energy Converter in Regular and Focused Extreme Wave Events

2020 ◽  
Author(s):  
Eirini Katsidoniotaki ◽  
Edward Ransley ◽  
Scott Brown ◽  
Johannes Palm ◽  
Jens Engström ◽  
...  
Keyword(s):  
Wave Energy ◽  
Wave Train ◽  
Offshore Structures ◽  
Wave Energy Converter ◽  
Extreme Waves ◽  
Extreme Wave ◽  
Energy Converter ◽  
Point Absorber ◽  
Wave Energy Converters ◽  
Extreme Loads

Abstract Accurate modeling and prediction of extreme loads for survivability is of crucial importance if wave energy is to become commercially viable. The fundamental differences in scale and dynamics from traditional offshore structures, as well as the fact that wave energy has not converged around one or a few technologies, implies that it is still an open question how the extreme loads should be modeled. In recent years, several methods to model wave energy converters in extreme waves have been developed, but it is not yet clear how the different methods compare. The purpose of this work is the comparison of two widely used approaches when studying the response of a point-absorber wave energy converter in extreme waves, using the open-source CFD software OpenFOAM. The equivalent design-waves are generated both as equivalent regular waves and as focused waves defined using NewWave theory. Our results show that the different extreme wave modeling methods produce different dynamics and extreme forces acting on the system. It is concluded that for the investigation of point-absorber response in extreme wave conditions, the wave train dynamics and the motion history of the buoy are of high importance for the resulting buoy response and mooring forces.

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