scholarly journals A Nonlinear Extension for Linear Boundary Element Methods in Wave Energy Device Modelling

2012 ◽  
Author(s):  
Alexis Merigaud ◽  
Jean-Christophe Gilloteaux ◽  
John V. Ringwood
Keyword(s):  
Boundary Element ◽  
Wave Energy ◽  
Linear Models ◽  
Boundary Element Methods ◽  
Hydrodynamic Models ◽  
Energy Device ◽  
Energy Capture ◽  
Energy Devices ◽  
Higher Order Terms ◽  
Device Modelling

To date, mathematical models for wave energy devices typically follow Cummins equation, with hydrodynamic parameters determined using boundary element methods. The resulting models are, for the vast majority of cases, linear, which has advantages for ease of computation and a basis for control design to maximise energy capture. While these linear models have attractive properties, the assumptions under which linearity is valid are restrictive. In particular, the assumption of small movements about an equilibrium point, so that higher order terms are not significant, needs some scrutiny. While this assumption is reasonable in many applications, in wave energy the main objective is to exaggerate the movement of the device through resonance, so that energy capture can be maximised. This paper examines the value of adding specific nonlinear terms to hydrodynamic models for wave energy devices, to improve the validity of such models across the full operational spectrum.

Comparison of Mooring Solutions and Array Systems for Point Absorbing Wave Energy Devices

2018 ◽  
Author(s):  
Jonas W. Ringsberg ◽  
Hanna Jansson ◽  
Shun-Han Yang ◽  
Martin Örgård ◽  
Erland Johnson
Keyword(s):  
Systems Engineering ◽  
Wave Energy ◽  
Ocean Energy ◽  
Mooring Lines ◽  
Energy Capture ◽  
Energy Devices ◽  
Structure Response ◽  
Energy Technologies ◽  
Cost Of Energy ◽  
Reference Installation

Most of the ocean energy technologies are considered to be in a pre-commercial phase and need technical development. This study focuses on design of mooring solutions and compares array systems of a specific floating point-absorbing wave energy converter (WEC) developed by the company Waves4Power. A full-scale prototype of the WEC is installed in Runde (Norway) where it is moored with three polyester mooring lines, each having one floater and one gravity anchor. Based on this reference installation, the method of systems engineering was used to propose twenty-two conceptual mooring solutions for different array systems. They were compared and reduced to four top concepts in a systematic elimination procedure using Pugh and Kesselring matrices. The top concepts were assessed in detail by means of LCOE (levelised cost of energy), LCA (life cycle analysis) and risk analyses. The fatigue life of the mooring lines and the energy capture were calculated using results obtained from coupled hydrodynamic and structure response analyses in the DNV-GL DeepC software. Two final concepts were proposed for the water depths 75 and 200 m.

Life cycle comparison of a wave and tidal energy device

2011 ◽  
Vol 225 (4) ◽  
pp. 325-337 ◽  
Author(s):  
S Walker ◽  
R Howell
Keyword(s):  
Life Cycle ◽  
Wave Energy ◽  
Tidal Energy ◽  
Development Stage ◽  
Payback Period ◽  
Energy Device ◽  
Energy Mix ◽  
Energy Devices ◽  
Marine Energy ◽  
Marine Current

Tidal and wave energy devices are often discussed as a future contributor to the UK’s energy mix. Indeed, marine energy resources are said to have the potential to supply up to 20 per cent of the nation’s electricity demand. However, these technologies are currently at the development stage and make no meaningful contribution to the national grid. A number of devices have been developed, but no single method has emerged as the leading technology. This paper aims to compare two promising devices, one wave device and one tidal device, and assess the life cycle properties of each. A life cycle assessment of the Oyster wave energy device was conducted as part of this study, and a comparison of this and the SeaGen marine current turbine was undertaken. In both cases a ‘cradle-to-grave’ assessment was carried out, calculating emissions from materials, fabrication, transport, installation, lifetime maintenance, and decommissioning (including recycling). The SeaGen tidal device was calculated to have an energy payback period of 14 months, and a CO2 payback period of 8 months. The equivalent figures for the Oyster device were 12 and 8 months, respectively. The respective energy and carbon intensities for the two devices were 214 kJ/kWh and 15 gCO2/kWh for the SeaGen and 236 kJ/kWh and 25 gCO2/kWh for the Oyster. The calculated intensities and payback periods are close to those of established wind turbine technologies, and low relative to the 400–1000 g CO2/kWh of typical fossil fuel generation. With further developments in construction and deployment efficiency these intensities are expected to fall, so the devices appear to have the potential to offer a viable contribution to the UK’s future energy mix.

Floating Wave Energy Device With Two Oscillating Water Columns

2007 ◽  
Author(s):  
D. C. Hong ◽  
S. Y. Hong
Keyword(s):  
Green Function ◽  
Wave Energy ◽  
Numerical Results ◽  
The Body ◽  
Energy Device ◽  
Energy Devices ◽  
Damping Parameter ◽  
Absorbed Power ◽  
Linear Damping ◽  
Drift Force

The absorbed power, motion and drift force of a floating wave energy device with two oscillating water column (OWC) chambers are studied taking account of the interaction between two chambers within the scope of the linear wave theory. The oscillating surface-pressure in the OWC chamber is represented by a product of the air-flow velocity and an equivalent linear damping parameter. The two-dimensional potential problem is formulated as a hybrid Green integral equation using the Rankine Green function inside the chamber and the finite-depth free-surface Green function outside respectively. The present numerical method makes it possible to tune the OWC and the floating body motions to the incident waves that is essential to maximize the absorbed power. The absorbed powers are calculated by both the near-field and far-field methods for various values of the linear damping parameter in two chambers. The reflection and transmission coefficients of the body are also presented. The numerical results for one OWC devices where the OWC is placed in a backward and forward bent duct buoys (BBDB and FBDB) are also presented for comparison of the performance. The present floating wave energy devices can also be served as a good floating breakwater having small drift force. The present numerical results show that the existence of reverse time-mean horizontal wave drift force is not contradictory to the principle of wave energy conservation.

scholarly journals The MBARI-WEC: a power source for ocean sensing

2021 ◽  
Author(s):  
Andrew Hamilton ◽  
François Cazenave ◽  
Dominic Forbush ◽  
Ryan G. Coe ◽  
Giorgio Bacelli
Keyword(s):  
Frequency Domain ◽  
Wave Energy ◽  
Autonomous Underwater Vehicles ◽  
Domain Model ◽  
Monterey Bay ◽  
Hydrodynamic Models ◽  
Energy Device ◽  
Linear Frequency ◽  
Point Absorber ◽  
Wave Energy Converters

AbstractInterest in wave energy converters to provide autonomous power to various ocean-bound systems, such as autonomous underwater vehicles, sensor systems, and even aquaculture farms, has grown in recent years. The Monterey Bay Aquarium Research Institute has developed and deployed a small two-body point absorber wave energy device suitable to such needs. This paper provides a description of the system to support future open-source access to the device and further the general development of similar wave energy systems. Additionally, to support future control design and system modification efforts, a set of hydrodynamic models are presented and cross-compared. To test the viability of using a linear frequency-domain admittance model for controller tuning, the linear model is compared against four WEC-Sim models of increasing complexity. The linear frequency-domain model is found to be generally adequate for capturing system dynamics, as the model agreement is good and the degree of nonlinearity introduced in the WEC-Sim models is generally less than 2.5%.

scholarly journals Fluid-Structure-Soil Interaction of a Moored Wave Energy Device

2019 ◽  
Author(s):  
Joe G. Tom ◽  
Dirk P. Rijnsdorp ◽  
Raffaele Ragni ◽  
David J. White
Keyword(s):  
Cyclic Loading ◽  
Wave Energy ◽  
Significant Proportion ◽  
Interdisciplinary Approach ◽  
Cost Effective ◽  
Wave Flow ◽  
Energy Device ◽  
Subsequent Increase ◽  
Operational Conditions ◽  
Energy Devices

Abstract This paper explores the response of a wave energy device during extreme and operational conditions and the effect of this response on the geotechnical stability of the associated taut moorings. The non-hydrostatic wave-flow model SWASH is used to simulate the response of a taut-moored wave energy converter. The predicted forces acting on the mooring system are used to compute the build-up of excess pore pressures in the soil around the mooring anchor and the resulting changes in strength and capacity. An initial loss of strength is followed by a subsequent increase in capacity, associated with long-term cyclic loading and hardening due to consolidation. The analyses show how cyclic loading may actually benefit and reduce anchoring requirements for wave energy devices. It demonstrates the viability of a close interdisciplinary approach towards an optimized and cost-effective design of mooring systems, which form a significant proportion of expected capital expenditures.

Design of Mooring Solutions and Array Systems for Point Absorbing Wave Energy Devices—Methodology and Application

2019 ◽  
Vol 142 (3) ◽  
Author(s):  
Jonas W. Ringsberg ◽  
Hanna Jansson ◽  
Martin Örgård ◽  
Shun-Han Yang ◽  
Erland Johnson
Keyword(s):  
Systems Engineering ◽  
Wave Energy ◽  
Ocean Energy ◽  
Mooring Lines ◽  
Energy Capture ◽  
Energy Devices ◽  
Structure Response ◽  
Energy Technologies ◽  
Cost Of Energy ◽  
Reference Installation

Abstract Most of the ocean energy technologies are considered to be in a pre-commercial phase and need technical development. This study focuses on the design of mooring solutions and compares array systems of a specific floating point-absorbing wave energy converter (WEC) developed by the company Waves4Power. A full-scale prototype of the WEC is installed in Runde (Norway) where it is moored with three polyester mooring lines, each having one floater and one gravity anchor. Based on this reference installation, the method of systems engineering was used to propose 22 conceptual mooring solutions for different array systems. They were compared and reduced to four top concepts in a systematic elimination procedure using Pugh and Kesselring matrices. The top concepts were assessed in detail by means of levelized cost of energy (LCOE), life cycle analysis (LCA), and risk analyses. The fatigue life of the mooring lines and the energy capture were calculated using results obtained from coupled hydrodynamic and structure response analyses in the dnv-gl deepc software. Two final concepts were proposed for the water depths 75 and 200 m.

scholarly journals On Wave-Induced Elastic Deformations of a Submerged Wave Energy Device

2020 ◽  
Vol 19 (3) ◽  
pp. 317-338
Author(s):  
Shuijin Li ◽  
Masoud Hayatdavoodi ◽  
R. Cengiz Ertekin
Keyword(s):  
Nonlinear Wave ◽  
Wave Energy ◽  
Structural Integrity ◽  
Accurate Determination ◽  
Elastic Response ◽  
Wave Loads ◽  
Extreme Wave ◽  
Energy Device ◽  
Energy Devices ◽  
Wave Induced

Abstract Structural integrity has remained a challenge for design and analysis of wave energy devices. A difficulty in assessment of the structural integrity is often laid in the accurate determination of the wave-induced loads on the wave energy devices and the repones of the structure. Decoupled hydroelastic response of a submerged, oscillating wave energy device to extreme nonlinear wave loads is studied here. The submerged wave energy device consists of an oscillating horizontal disc attached to a direct-drive power take-off system. The structural frame of the wave energy device is fixed on the seafloor in shallow water. Several extreme wave conditions are considered in this study. The nonlinear wave loads on members of the submerged structure are obtained by use of the level I Green-Naghdi equations and Morison’s equation for cylindrical members. Distribution of Von Mises stresses and the elastic response of the structure to the extreme wave loads are determined by use of a finite element method. The decoupled hydroelastic analysis of the structure is carried out for devices built by four different materials, namely stainless steel, concrete, aluminium alloy, and titanium alloy. The elastic response of these devices is studied and results are compared with each other. Points of maximum stress and deformations are determined and the structural integrity under the extreme conditions is assessed. It is shown that the proposed approaches provide invaluable information about the structural integrity of wave energy devices.

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