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.

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.

The Principle, Review and Prospect of Wave Energy Converter

2011 ◽  
Vol 347-353 ◽  
pp. 3744-3749
Author(s):  
Yu Jiong Gu ◽  
Li Jun Zhao ◽  
Jing Hua Huang ◽  
Bing Bing Wang
Keyword(s):  
Wave Energy ◽  
Wave Energy Converter ◽  
Wave Power ◽  
Power Development ◽  
Energy Converter ◽  
Basic Principles ◽  
Technology Application ◽  
Energy And Environment ◽  
Point Absorber ◽  
Wave Energy Converters

Abstract: Being confronted with the severity of the energy and environment problems, the world attaches more and more importance to the potential of wave energy. Based on the necessity and feasibility of wave power development, the basic principles of wave energy converter are in this paper firstly. Then some kinds of WEC’s principle, merits and drawbacks, technology application are reviewed, such as OWC, raft, Tapchan, point absorber, Salter, pendulum. After that, wave energy developing conditions in some typical countries are recommended. After reviewing the features of various wave energy converters and WEC application examples in some countries, prospect and a few problems in wave energy utilizing are stated briefly.

scholarly journals Coupled Mooring Analyses for the WEC-Sim Wave Energy Converter Design Tool

2016 ◽  
Author(s):  
Senu Sirnivas ◽  
Yi-Hsiang Yu ◽  
Matthew Hall ◽  
Bret Bosma
Keyword(s):  
Numerical Method ◽  
Wave Energy ◽  
Coupled Model ◽  
The Body ◽  
Wave Energy Converter ◽  
Irregular Waves ◽  
Lumped Mass ◽  
Energy Converter ◽  
Mooring Lines ◽  
Point Absorber

A wave-energy-converter-specific time-domain modeling method (WEC-Sim) was coupled with a lumped-mass-based mooring model (MoorDyn) to improve its mooring dynamics modeling capability. This paper presents a verification and validation study on the coupled numerical method. First, a coupled model was built to simulate a 1/25 model scale floating power system connected to a traditional three-point catenary mooring with an angle of 120 between the lines. The body response and the tension force on the mooring lines at the fairlead in decay tests and under regular and irregular waves were examined. To validate and verify the coupled numerical method, the simulation results were compared to the measurements from a wave tank test and a commercial code (OrcaFlex). Second, a coupled model was built to simulate a two-body point absorber system with a chain-connected catenary system. The influence of the mooring connection on the point absorber was investigated. Overall, the study showed that the coupling of WEC-Sim and the MoorDyn model works reasonably well for simulating a floating system with practical mooring designs and predicting the corresponding dynamic loads on the mooring lines. Further analyses on improving coupling efficiency and the feasibility of applying the numerical method to simulate WEC systems with more complex mooring configuration are still needed.

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 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.

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.

Power Characteristic Analysis and Optimization of Point Absorber Wave Energy Converter

2013 ◽  
Vol 313-314 ◽  
pp. 837-842 ◽  
Author(s):  
Xiong Bo Zheng ◽  
Jin Jiang ◽  
Liang Zhang
Keyword(s):  
Wave Energy ◽  
Research Result ◽  
Wave Theory ◽  
Wave Energy Converter ◽  
Power Characteristic ◽  
Characteristic Analysis ◽  
Energy Converter ◽  
Point Absorber ◽  
Wave Energy Converters ◽  
Numerical Calculation Method

Compared with other wave energy converters, point absorber wave energy converter (WEC)is more suitable for small wave conditions, and adapts to China’s coastal wavecharacteristics. Based on the linearregular wave theory, the power characteristic of point absorber WEC wasanalyzed in the paper. Using numerical calculation method based on linearpotential flow theory in frequency domain, we calculated the hydrodynamiccoefficients and response amplitude operator (RAO) of floater in wavecondition. And then the power of the point absorber WEC was calculated undergiven conditions. Based on the calculation, we studied the rule of influence of WEC’s major parameters to its output power. The research result offer importanttheory foundation for optimal design of point absorber WEC’s power characteristic.

Coupled dynamic analysis of hybrid offshore wind turbine and wave energy converter

2021 ◽  
pp. 1-40
Author(s):  
Rony JS ◽  
Debabrata Karmakar
Keyword(s):  
Dynamic Analysis ◽  
Wind Turbine ◽  
Wave Energy ◽  
Wave Energy Converter ◽  
Offshore Wind ◽  
Irregular Waves ◽  
Energy Converter ◽  
Point Absorber ◽  
Wave Energy Converters ◽  
Energy Converters

Abstract The combined offshore wind and wave energy on an integrated platform is an economical solution for the offshore energy industry as they share the infrastructure and ocean space. The study presents the dynamic analysis of the Submerged Tension-Leg Platform (STLP) combined with a heaving-type point absorber wave energy converter (WEC). The feasibility study of the hybrid concept is performed using the aero-servo-hydro-elastic simulation tool FAST. The study analyses the responses of the combined system to understand the influence of the WECs on the STLP platform for various operating conditions of the wind turbine under regular and irregular waves. A positive synergy is observed between the platform and the WECs, and the study also focuses on the forces and moments developed at the interface of the tower and platform to understand the effect of wind energy on the turbine tower and importance of motion amplitudes on the performance of the combined platform system. The mean and standard deviation for the translation and rotational motions of combined wind and wave energy converters are determined for different sea states under both regular and irregular waves to analyse the change in responses of the structure. The study observed a reduction in motion amplitudes of the hybrid floating system with the addition of the wave energy converters around the STLP floater to improve the energy efficiency of the hybrid system. The study helps in understanding the best possible arrangement of point absorber type wave energy converters at the conceptual stage of the design process.

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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