Integrated dynamic modeling of a point absorber wave energy converter in regular and irregular waves

2015 ◽  
Author(s):  
Taofeek Orekan ◽  
Peng Zhang
Keyword(s):  
Dynamic Modeling ◽  
Wave Energy ◽  
Wave Energy Converter ◽  
Irregular Waves ◽  
Energy Converter ◽  
Point Absorber

Optimum Power Capture of a New Wave Energy Converter in Irregular Waves

2009 ◽  
Author(s):  
George A. Aggidis ◽  
Mohammad T. Rahmati ◽  
Robert V. Chaplin ◽  
Andrew P. McCabe ◽  
Majid A. Bhinder ◽  
...  
Keyword(s):  
Control System ◽  
Wave Energy ◽  
Wave Spectrum ◽  
Wave Energy Converter ◽  
Irregular Waves ◽  
Energy Converter ◽  
Mean Power ◽  
Peak Period ◽  
Point Absorber ◽  
Power Capture

This paper presents the optimum power capture of a new point-absorber wave energy converter, in irregular waves. A stepwise control system for the wave energy converter (WEC) is developed. The control system is used to efficiently extract power from irregular waves where amplitudes vary from wave to wave. The Bretschneider spectrum is used in the experiment and the device is ‘tuned’ to the peak period of the sea state. It is shown that this WEC has a reasonable capture width in irregular waves. However, the optimum mean power depends on the wave spectrum, the shape of the collector body, its freeboard and the device pivot depth.

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.

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.

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
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