Stochastic modeling of long-term and extreme value estimation of wind and sea conditions for probabilistic reliability assessments of wave energy devices

2014 ◽  
Vol 89 ◽  
pp. 243-255 ◽  
Author(s):  
Simon Ambühl ◽  
Jens Peter Kofoed ◽  
John Dalsgaard Sørensen
Author(s):  
Lin Li ◽  
Zhen Gao ◽  
Torgeir Moan

The design of wind turbines requires information about joint data for wind and wave conditions. Moreover, combining offshore wind and wave energy facilities is a potential way to reduce the cost of offshore wind farms. To design combined offshore renewable energy concepts, it is important to choose sites where both wind and wave energy resources are substantial. This paper deals with joint environmental data for five European offshore sites which serve as basis for the analysis and comparison of combined renewable energy concepts developed in the EU FP7 project—MARINA Platform. The five sites cover both shallow and deep water, with three sites facing the Atlantic Ocean and two sites in the North Sea. The long-term joint distributions of wind and wave parameters are presented for these sites. Simultaneous hourly mean wind and wave hindcast data from 2001 to 2010 are used as a database. The joint distributions are modeled by fitting analytical distributions to the hindcast data. The long-term joint distributions can be used to estimate the wind and wave power output from each combined concept and to estimate the fatigue lifetime of the structure. The marginal distributions of wind and wave parameters are also provided. Based on the joint distributions, contour surfaces are established for combined wind and wave parameters for which the probability of exceedance corresponds to a return period of 50 years. The design points on the 50-year contour surfaces are suggested for extreme response analysis of combined concepts.


2014 ◽  
Vol 140 (9) ◽  
pp. 04014061 ◽  
Author(s):  
M. F. Huang ◽  
Wenjuan Lou ◽  
Xiaotao Pan ◽  
C. M. Chan ◽  
Q. S. Li

Energies ◽  
2021 ◽  
Vol 14 (4) ◽  
pp. 920
Author(s):  
Yue Hong ◽  
Irina Temiz ◽  
Jianfei Pan ◽  
Mikael Eriksson ◽  
Cecilia Boström

Wave energy converters (WECs), which are designed to harvest ocean wave energy, have recently been improved by the installation of numerous conversion mechanisms; however, it is still difficult to find an appropriate method that can compromise between strong environmental impact and robust performance by transforming irregular wave energy into stable electrical power. To solve this problem, an investigation into the impact of varied wave conditions on the dynamics of WECs and to determine an optimal factor for WECs to comply with long-term impacts was performed. In this work, we researched the performance of WECs influenced by wave climates. We used a permanent magnet linear generator (PMLG)-based WEC that was invented at Uppsala University. The damping effect was first studied with a PMLG-type WEC. Then, a group of sea states was selected to investigate their impact on the power production of the WEC. Two research sites were chosen to investigate the WEC’s annual energy production as well as a study on the optimal damping coefficient impact. In addition, we compared the WEC’s energy production between optimal damping and constant damping under a full range of sea states at both sites. Our results show that there is an optimal damping coefficient that can achieve the WEC’s maximum power output. For the chosen research sites, only a few optimal damping coefficients were able to contribute over 90% of the WEC’s annual energy production. In light of the comparison between optimal and constant damping, we conclude that, for specific regions, constant damping might be a better choice for WECs to optimize long-term energy production.


Author(s):  
Pedro C. Vicente ◽  
Anto´nio F. O. Falca˜o ◽  
Paulo A. P. Justino

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.


Author(s):  
Thiago S. Hallak ◽  
José F. Gaspar ◽  
Mojtaba Kamarlouei ◽  
Miguel Calvário ◽  
Mário J. G. C. Mendes ◽  
...  

This paper presents a study regarding a novel hybrid concept for both wind and wave energy offshore. The concept resembles a semi-submersible wind platform with a larger number of columns. Wave Energy Devices such as point absorbers are to be displayed around the unit, capturing wave energy while heaving and also enhancing the stability of the platform. In this paper, a first numerical study of the platform’s hull, without Wave Energy Converters, is carried out. Experiments in wave basin regarding the same unit have been conducted and the results are presented and compared to the numerical ones. Both stability and seakeeping performances are assessed and compared.


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