Design of the Mooring System for a Floating Wave Energy Converter

2018 ◽  
Vol 85 ◽  
pp. 1351-1355
Author(s):  
Xin He ◽  
Yougang Tang ◽  
Liqin Liu ◽  
Ruoyu Zhang
Keyword(s):  
Wave Energy ◽  
Wave Energy Converter ◽  
Mooring System ◽  
Energy Converter

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.

A submerged cylinder wave energy converter

2013 ◽  
Vol 716 ◽  
pp. 566-596 ◽  
Author(s):  
S. Crowley ◽  
R. Porter ◽  
D. V. Evans
Keyword(s):  
Wave Energy ◽  
Three Dimensional ◽  
Wave Energy Converter ◽  
Wave Crest ◽  
Maximum Efficiency ◽  
Passive Component ◽  
Mooring System ◽  
Energy Converter ◽  
Rotation Rates ◽  
Sea Bed

AbstractA novel design concept for a wave energy converter (WEC) is presented and analysed. Its purpose is to balance the theoretical capacity for power absorption against engineering design issues which plague many existing WEC concepts. The WEC comprises a fully submerged buoyant circular cylinder tethered to the sea bed by a simple mooring system which permits coupled surge and roll motions of the cylinder. Inside the cylinder a mechanical system of pendulums rotate with power generated by the relative rotation rates of the pendulums and the cylinder. The attractive features of this design include: making use of the mooring system as a passive component of the power take off (PTO); using a submerged device to protect it from excessive forces associated with extreme wave conditions; locating the PTO within the device and using a PTO mechanism which does not need to be constrained; exploiting multiple resonances of the system to provide a broad-banded response. A mathematical model is developed which couples the hydrodynamic waves forces on the device with the internal pendulums under a linearized framework. For a cylinder spanning a wave tank (equivalent to a two-dimensional assumption) maximum theoretical power for this WEC device is limited to 50 % maximum efficiency. However, numerical results show that a systematically optimized system can generate theoretical efficiencies of more than 45 % over a 6 s range of wave period containing most of the energy in a typical energy spectrum. Furthermore, three-dimensional results for a cylinder of finite length provide evidence that a cylinder device twice the length of its diameter can produce more than its own length in the power of an equivalent incident wave crest.

scholarly journals A Design of Mooring System for Floating Wave Energy Converter in Shallow Water

1997 ◽  
Vol 1997 (182) ◽  
pp. 341-348
Author(s):  
Hiroyuki Osawa ◽  
Yoshinori Nagata ◽  
Syogo Miyajima ◽  
Hisaaki Maeda
Keyword(s):  
Shallow Water ◽  
Wave Energy ◽  
Wave Energy Converter ◽  
Mooring System ◽  
Energy Converter

Experimental Study the Performance of a Compact Mooring System for a Dual Chamber Floating Oscillating Water Column Device

2020 ◽  
Author(s):  
Sheng Xu ◽  
K. Rezanejad ◽  
Shan Wang ◽  
J. F. M. Gadelho ◽  
C. Guedes Soares
Keyword(s):  
Water Column ◽  
Wave Energy ◽  
Degrees Of Freedom ◽  
Wave Energy Converter ◽  
Air Pressure ◽  
Mooring System ◽  
Oscillating Water Column ◽  
Energy Converter ◽  
Six Degrees Of Freedom ◽  
Motion Responses

Abstract A compact mooring system concept is proposed. This novel mooring is composed of submerged buoy and three segments of nylon ropes, which is suitable for the large wave energy converters and wave energy converter array due to its high flexibility and small mooring radius. The performance of this mooring concept was studied experimentally when it was moored to an oscillating water column. The damping of the oscillating water column was modelled by an orifice on top of the chamber. Both regular and irregular head sea wave tests were conducted. In order to study the influence of wave height on system dynamics, two series of regular wave tests with same periods but different wave heights were conducted. An optical tracking system was installed to capture six degrees of freedom motion responses of oscillating water column. The air pressure in the chamber was measured by the air pressure sensor. Two load cells were installed on the top of mooring lines to measure mooring tension time series. Besides, the wave surface elevations inside the chamber were measured by the wave gauges. According to the experimental results, the six degrees of freedom motion responses of floating wave energy converter and mooring tensions are analyzed. Besides, the energy conversion efficiency is evaluated based on the measured data.

scholarly journals KNSwing—On the Mooring Loads of a Ship-Like Wave Energy Converter

2019 ◽  
Vol 7 (2) ◽  
pp. 29
Author(s):  
Kim Nielsen ◽  
Jonas Thomsen
Keyword(s):  
Numerical Model ◽  
Wave Energy ◽  
Numerical Models ◽  
Breaking Waves ◽  
Wave Energy Converter ◽  
Experimental Results ◽  
Irregular Waves ◽  
Mooring System ◽  
Energy Converter ◽  
The Waves

The critical function of keeping a floating Wave Energy Converter in position is done by a mooring system. Several WECs have been lost due to failed moorings, indicating that extreme loads, reliability and durability are very important aspects. An understanding of the interaction between the WEC’s motion in large waves and the maximum mooring loads can be gained by investigating the system at model scale supported by numerical models. This paper describes the testing of a novel attenuator WEC design called KNSwing. It is shaped like a ship facing the waves with its bow, which results in low mooring loads and small motions in most wave conditions when the structure is longer than the waves. The concept is tested using an experimental model at scale 1:80 in regular and irregular waves, moored using rubber bands to simulate synthetic moorings. The experimental results are compared to numerical simulations done using the OrcaFlex software. The experimental results show that the WEC and the mooring system survives well, even under extreme and breaking waves. The numerical model coefficient concerning the nonlinear drag term for the surge motion is validated using decay tests. The numerical results compare well to the experiments and, thereby, the numerical model can be further used to optimize the mooring system.

scholarly journals Numerical modelling on the performance of a rolling-type wave energy converter with mooring system

2020 ◽  
Vol 461 ◽  
pp. 012035
Author(s):  
Yichen Jiang ◽  
Yuhao Peng ◽  
Peidong Zhao ◽  
He Zhang ◽  
Hongyun Zong ◽  
...  
Keyword(s):  
Numerical Modelling ◽  
Wave Energy ◽  
Wave Energy Converter ◽  
Mooring System ◽  
Energy Converter ◽  
Type Wave

Numerical study of a novel flex mooring system of the floating wave energy converter in ultra-shallow water and experimental validation

2018 ◽  
Vol 151 ◽  
pp. 342-354 ◽  
Author(s):  
Shuo Huang ◽  
Songwei Sheng ◽  
Yage You ◽  
Arnaud Gerthoffert ◽  
Wensheng Wang ◽  
...  
Keyword(s):  
Shallow Water ◽  
Wave Energy ◽  
Experimental Validation ◽  
Numerical Study ◽  
Wave Energy Converter ◽  
Mooring System ◽  
Energy Converter

Design of a Mooring System With Synthetic Ropes for the FLOW Wave Energy Converter

2009 ◽  
Author(s):  
Nuno Fonseca ◽  
Ricardo Pascoal ◽  
Tiago Morais ◽  
Renato Dias
Keyword(s):  
Wave Energy ◽  
Domain Boundary ◽  
Angular Separation ◽  
Development Stage ◽  
Wave Energy Converter ◽  
Design Solution ◽  
Mooring System ◽  
Energy Converter ◽  
Mooring Lines ◽  
Global Cost

Martifer Energia is developing a concept of a wave energy converter (WEC) to be used at near shore locations with water depths starting at around 40m. It is a floating device composed of two bodies connected by a one degree of freedom articulation. The energy is extracted at the articulation by a power takeoff system actuated by the relative motion between the bodies. One of the important components of many WECs is the mooring system, since usually the cost is large compared global cost of the device. In this case the WEC will be moored by a spread mooring that allows the device to weathervane with the environmental loads. The paper presents one design solution for the mooring system investigated during the development stage of the concept. It is composed of four hybrid lines, each one with a segment of nylon rope connected to the floating device and a part of chain that contacts with the sea bottom and ends at the anchor. The wave frequency hydrodynamics are first calculated with a frequency domain boundary element method. The nonlinear cable dynamics problem, which is coupled to the slow drift motions of the floater, is solved in the time domain by a finite difference method. The design considers the climatology of the future area of operation of the prototype. Since the loads on the lines depend on the characteristics of the lines themselves, the design solution is obtained iteratively. Appropriate safety factors are considered. The result is the number of mooring lines, their angular separation, length and diameter of each line component.

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