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.

Constrained Optimal Control of a Heaving Buoy Wave-Energy Converter

2010 ◽  
Vol 133 (1) ◽  
Author(s):  
Jørgen Hals ◽  
Johannes Falnes ◽  
Torgeir Moan
Keyword(s):  
Energy Absorption ◽  
Wave Energy ◽  
Optimal Operation ◽  
Wave Energy Converter ◽  
Irregular Waves ◽  
Energy Converter ◽  
Model Predictive Controller ◽  
Wave Energy Converters ◽  
Predictive Controller ◽  
Energy Converters

The question of optimal operation of wave-energy converters has been a key issue since modern research on the topic emerged in the early 1970s, and criteria for maximum wave-energy absorption soon emerged from frequency domain analysis. However, constraints on motions and forces give the need for time-domain modeling, where numerical optimization must be used to exploit the full absorption potential of an installed converter. A heaving, semisubmerged sphere is used to study optimal constrained motion of wave-energy converters. Based on a linear model of the wave-body interactions, a procedure for the optimization of the machinery force is developed and demonstrated. Moreover, a model-predictive controller is defined and tested for irregular sea. It repeatedly solves the optimization problem online in order to compute the optimal constrained machinery force on a receding horizon. The wave excitation force is predicted by use of an augmented Kalman filter based on a damped harmonic oscillator model of the wave process. It is shown how constraints influence the optimal motion of the heaving wave-energy converter, and also how close it is possible to approach previously published theoretical upper bounds. The model-predictive controller is found to perform close to optimum in irregular waves, depending on the quality of the wave force predictions. An absorbed power equal to or larger than 90% of the ideal constrained optimum is achieved for a chosen range of realistic sea states. Under certain circumstances, the optimal wave-energy absorption may be better in irregular waves than for a corresponding regular wave having the same energy period and wave-power level. An argument is presented to explain this observation.

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.

The Potential for Combining Floating Wind Turbines With Point Absorbing Wave Energy Converters

2021 ◽  
Author(s):  
David M. Skene ◽  
Nataliia Sergiienko ◽  
Boyin Ding ◽  
Benjamin Cazzolato
Keyword(s):  
Wind Turbine ◽  
Frequency Domain ◽  
Wave Energy ◽  
Two Dimensions ◽  
Offshore Wind ◽  
Offshore Wind Turbine ◽  
Specific Design ◽  
Energy Converter ◽  
Point Absorber ◽  
Wave Energy Converters

Abstract The potential for coupling a cylindrical point absorber type wave energy converter (WEC) to a 5MW spar type floating offshore wind turbine is investigated. The wind and WEC system is modelled in the frequency domain and in two dimensions under the simplifying assumption that wind and waves propagate in the same direction. Coupling of the bodies is considered with respect to all theoretical combinations that might be achieved rather than a single specific design. Results are analysed with respect to the maximum power that the WEC coupling can achieve. It is shown that for mild waves the WEC can theoretically produce power in the range of 0.2 to 0.6 MW, its optimal dimensions are such that the draft and radius are approximately 18.8 m, and that obtaining this power tends to marginally amplify the pitch of the spar.

Optimization of Mooring Configuration Parameters of Floating Wave Energy Converters

2011 ◽  
Author(s):  
Pedro C. Vicente ◽  
Anto´nio F. O. Falca˜o ◽  
Paulo A. P. Justino
Keyword(s):  
Wave Energy ◽  
Oil And Gas ◽  
Wave Energy Converter ◽  
Domain Model ◽  
Floating Point ◽  
Mooring System ◽  
Energy Converter ◽  
Energy Devices ◽  
Wave Energy Converters ◽  
Energy Converters

Floating point absorbers devices are a large class of wave energy converters for deployment offshore, typically in water depths between 40 and 100m. As floating oil and gas platforms, the devices are subject to drift forces due to waves, currents and wind, and therefore have to be kept in place by a proper mooring system. Although similarities can be found between the energy converting systems and floating platforms, the mooring design requirements will have some important differences between them, one of them associated to the fact that, in the case of a wave energy converter, the mooring connections may significantly modify its energy absorption properties by interacting with its oscillations. It is therefore important to examine what might be the more suitable mooring design for wave energy devices, according to the converters specifications. When defining a mooring system for a device, several initial parameters have to be established, such as cable material and thickness, distance to the mooring point on the bottom, and which can influence the device performance in terms of motion, power output and survivability. Different parameters, for which acceptable intervals can be established, will represent different power absorptions, displacements from equilibrium position, load demands on the moorings and of course also different costs. The work presented here analyzes what might be, for wave energy converter floating point absorber, the optimal mooring configuration parameters, respecting certain pre-established acceptable intervals and using a time-domain model that takes into account the non-linearities introduced by the mooring system. Numerical results for the mooring forces demands and also motions and absorbed power, are presented for two different mooring configurations for a system consisting of a hemispherical buoy in regular waves and assuming a liner PTO.

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.

scholarly journals Hydrodynamic investigation on an OWC wave energy converter integrated into an offshore wind turbine monopile

2020 ◽  
Vol 162 ◽  
pp. 103731 ◽  
Author(s):  
Yu Zhou ◽  
Dezhi Ning ◽  
Wei Shi ◽  
Lars Johanning ◽  
Dongfang Liang
Keyword(s):  
Wind Turbine ◽  
Wave Energy ◽  
Wave Energy Converter ◽  
Offshore Wind ◽  
Offshore Wind Turbine ◽  
Energy Converter

scholarly journals Initial conceptual demonstration of control co-design for WEC optimization

2020 ◽  
Author(s):  
Ryan G. Coe ◽  
Giorgio Bacelli ◽  
Sterling Olson ◽  
Vincent S. Neary ◽  
Mathew B. R. Topper
Keyword(s):  
Design Optimization ◽  
Wave Energy ◽  
Wave Energy Converter ◽  
Short Paper ◽  
Energy Converter ◽  
Matlab Toolbox ◽  
Wave Energy Converters ◽  
Practical Engineering ◽  
Converter Design ◽  
Energy Converters

While some engineering fields have benefited from systematic design optimization studies, wave energy converters have yet to successfully incorporate such analyses into practical engineering workflows. The current iterative approach to wave energy converter design leads to suboptimal solutions. This short paper presents an open-source MATLAB toolbox for performing design optimization studies on wave energy converters where power take-off behavior and realistic constraints can be easily included. This tool incorporates an adaptable control co-design approach, in that a constrained optimal controller is used to simulate device dynamics and populate an arbitrary objective function of the user's choosing. A brief explanation of the tool's structure and underlying theory is presented. In order to demonstrate the capabilities of the tool, verify its functionality, and begin to explore some basic wave energy converter design relationships, three conceptual case studies are presented. In particular, the importance of considering (and constraining) the magnitudes of device motion and forces is shown.<br>

A Hybrid Power Generation Platform Combining Floating Wind Turbine and Oscillating Water Column Wave Energy Converters

2019 ◽  
Author(s):  
Zheng Chen ◽  
Weijian Zeng ◽  
Ming Tan ◽  
Dahai Zhang ◽  
Yulin Si
Keyword(s):  
Power Generation ◽  
Wind Turbine ◽  
Water Column ◽  
Wave Energy ◽  
Wind Farms ◽  
Offshore Wind ◽  
Oscillating Water Column ◽  
Offshore Wind Farms ◽  
Wave Energy Converters ◽  
Energy Converters

Abstract Recent years have seen rapid development in offshore wind technology. Particularly, floating offshore wind turbines possess great potential in deep water coastal places around the world, though they are now still in the demonstration phase. At the same time, the unused wave energy is also abundant at the sites of offshore wind farms, especially those in deep sea regions. Collecting wave energy in offshore wind farms might benefit both total energy production and reduce maintenance cost. Therefore, integrating offshore wind turbine with wave energy conversion devices could be a good idea to achieve higher efficiency and lower cost. In this paper, we report a combined wind and wave energy power generation concept called WindOWC, which constits of a 5MW wind turbine and three oscillating-water-column (OWC) wave energy converters (WECs). The wind turbine is mounted on a semi-submersible floating platform, which is similar to OC4-semibsubmersible, and the OWCs are located in its three offset columns. In this design, the wind turbine and WECs share the same supporting platform and the power transmission system, thus is expected to reduce the cost of energy. Also, it is possible the OWCs may improve the platform dynamic performance by providing positive damping through controlling the air turbine rotational speed. In this work, we describe the geometry properties of the proposed WindOWC concept and conduct preliminary hydrodynamic analysis using potential flow theory. The ANSYS AQWA is used to obtain the system dynamic responses in frequency and time domain, respectively. The OWC dynamics and expected positive damping from them will be investigated in the future.

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.

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