Collision risk modelling for tidal energy devices: A flexible simulation-based approach

The lifespan and economic viability of tidal energy devices are constrained, in part, by the complex degradation of the tidal turbine blade materials due to prolonged immersion in a hostile sub-sea environment. Seawater penetration is a significant degradation mechanism in composite materials. This work aims to investigate the influence of microstructure and hydrostatic pressure on water absorption in four polymer composites which are candidate materials for use in tidal energy devices. These materials are: a glass fibre powder epoxy, a carbon fibre powder epoxy, glass fibre Ampreg epoxy and a chopped fibre glass fibre Polyether Ether Ketone. X-ray computed tomography is used to characterise the voids, resin-rich areas and other manufacturing defects present in each material. These defects are known to significantly alter the rate of moisture diffusion, as well as the total uptake of water at saturation. The samples are then exposed to accelerated water aging and hydrostatic pressurisation in order to simulate a range of expected sub-sea operating conditions. The material micro-structure, the matrix material and pressurisation level are shown to strongly influence both the moisture absorption rate and total water uptake. Significant volumetric changes are also noted for all samples, both during and after aging. X-ray computed tomography scans of specimens also provide a unique insight into the role of voids in storing water once a material has reached saturation.

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Multiobjective Optimization Based Vessel Collision Avoidance Strategy Optimization

Mathematical Problems in Engineering ◽

10.1155/2014/914689 ◽

2014 ◽

Vol 2014 ◽

pp. 1-9 ◽

Cited By ~ 5

Author(s):

Qingyang Xu ◽

Chuang Zhang ◽

Ning Wang

Keyword(s):

Multiobjective Optimization ◽

Collision Avoidance ◽

Collision Risk ◽

Nsga Ii ◽

Great Loss ◽

Marine Traffic ◽

Simulation Based ◽

International Regulations ◽

Avoidance Strategy ◽

Rudder Angle

The vessel collision accidents cause a great loss of lives and property. In order to reduce the human fault and greatly improve the safety of marine traffic, collision avoidance strategy optimization is proposed to achieve this. In the paper, a multiobjective optimization algorithm NSGA-II is adopted to search for the optimal collision avoidance strategy considering the safety as well as economy elements of collision avoidance. Ship domain and Arena are used to evaluate the collision risk in the simulation. Based on the optimization, an optimal rudder angle is recommended to navigator for collision avoidance. In the simulation example, a crossing encounter situation is simulated, and the NSGA-II searches for the optimal collision avoidance operation under the Convention on the International Regulations for Preventing Collisions at Sea (COLREGS). The simulation studies exhibit the validity of the method.

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Good noise, bad noise: A tricky case of balancing risk of physical injury against acoustic disturbance for marine mammals and tidal energy devices

The Journal of the Acoustical Society of America ◽

10.1121/1.4988861 ◽

2017 ◽

Vol 141 (5) ◽

pp. 3921-3921

Author(s):

Ben Wilson ◽

Brett Marmo ◽

Paul A. Lepper ◽

Denise Risch ◽

Steven Benjamins ◽

...

Keyword(s):

Marine Mammals ◽

Tidal Energy ◽

Physical Injury ◽

Acoustic Disturbance ◽

Energy Devices

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Marine Scour and Offshore Wind: Lessons Learnt and Future Challenges

Volume 5: Ocean Space Utilization; Ocean Renewable Energy ◽

10.1115/omae2011-50117 ◽

2011 ◽

Cited By ~ 5

Author(s):

John M. Harris ◽

Richard J. S. Whitehouse ◽

James Sutherland

Keyword(s):

Hazard Assessment ◽

Wind Farms ◽

Tidal Energy ◽

Offshore Wind ◽

Commercial Development ◽

Offshore Wind Farms ◽

Energy Devices ◽

Lessons Learnt ◽

Future Challenges ◽

Scour Hazard

The drive for developing marine offshore renewables has led to specific requirements for scour hazard assessment relating to the associated foundation structures and the cabling necessary for in-field transmission and power export. To date within the United Kingdom (UK) a number of demonstrator projects have been constructed covering wind, wave and tidal generation. However, only offshore wind has been developed at large-scale at present as part of two rounds of commercial development of offshore wind farms (OWFs). In June 2008, The Crown Estate, responsible for licensing seabed use, announced proposals for a third round of offshore wind farms to develop an additional 25 GW of energy to the 8 GW already planned for under Rounds 1 and 2. The size of these Round 3 developments will vary, but the largest of these zones will involve the construction of around 2500 seabed foundation structures. Under Round 1 and 2 developments monopile and jacket type foundations have been used, although several other European (non UK) wind farms have been built using gravity base foundations. For a wind turbine the foundations may account for up to 35% of the installed cost. Therefore, one of the future challenges for large volume installation of offshore wind is the control and minimization of these costs. For tidal energy devices one of the principal requirements for many of the devices proposed is their placement in areas of strong tidal energy, and this has implications not only for the stability of the foundation option, but also for the construction methodology. Similarly wave energy devices are designed to be located in shallow, coastal environments as either floating or bottom mounted systems. These devices, by design, are intended to be located in environments with strong wave action. This may be substantial during storm events, which has implications for the integrity of the anchoring system keeping the wave device on station or the design of the device if it is seabed mounted. This paper will explore the lessons learnt from existing offshore wind farm developments as this represents the principal body of collected monitoring data. Using these data the paper will outline some of the challenges facing the offshore renewable industry in respect of the foundation designs and specifically the requirements for scour hazard assessment using the combined experience from those developments currently operational or under construction.

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Tidal energy devices

Renewable Energies Offshore ◽

10.1201/b18973-9 ◽

2015 ◽

pp. 597-664 ◽

Cited By ~ 1

Keyword(s):

Tidal Energy ◽

Energy Devices

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Life cycle comparison of a wave and tidal energy device

Proceedings of the Institution of Mechanical Engineers Part M Journal of Engineering for the Maritime Environment ◽

10.1177/1475090211418892 ◽

2011 ◽

Vol 225 (4) ◽

pp. 325-337 ◽

Cited By ~ 6

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.

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Collision Risk Modelling

Offshore Risk Assessment ◽

10.1007/978-94-017-2471-5_10 ◽

1999 ◽

pp. 278-315

Author(s):

Jan Erik Vinnem

Keyword(s):

Collision Risk ◽

Risk Modelling

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Grid Integration of Wave and Tidal Energy

Volume 5: Ocean Space Utilization; Ocean Renewable Energy ◽

10.1115/omae2011-49953 ◽

2011 ◽

Author(s):

Anne Blavette ◽

Dara L. O’Sullivan ◽

Antony W. Lewis ◽

Michael G. Egan

Keyword(s):

Wind Energy ◽

Dynamic Models ◽

Dynamic Modelling ◽

Tidal Energy ◽

Energy Industry ◽

Grid Integration ◽

Ocean Energy ◽

Major Barrier ◽

Energy Devices ◽

Grid Connection

Wave and tidal energy provide a renewable source of electricity. However, their inherent fluctuations may have a negative impact on the power quality of a local electrical network. Grid operators assess this impact through the use of dynamic models of the generation units, which are inserted into the overall power system model. Providing these models is a compulsory step for any power generator to procure a grid connection above a specified power capacity. Significant issues were encountered in the wind energy industry regarding the dynamic modelling of devices, among which were model numerical instability, poor dynamic model quality and model incompatibility. Considering the large diversity of device types in the emerging ocean energy industry, these problems are considered as a major barrier to the larger scale grid-integration of marine energy converters. Dynamic models must clearly demonstrate the compliance of the actual power generation device and array of devices to the grid code requirements for grid-connection to be allowed. A further barrier to grid connection of ocean energy devices is that existing grid codes — mainly written in the context of wind energy — may be irrelevant or inadequate for ocean energy devices. This paper presents an overview of these issues, and details a radically different approach to the dynamic modelling of ocean energy devices that will assist in overcoming the issues previously encountered in the development of wind turbine models. It also highlights the gaps and inadequacy regarding grid code requirements for ocean energy devices, and provides some recommendations for a new ocean energy grid code.

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Energy Harvesting From the Tidal Currents Using a Mangrove-Like System

Volume 9: Ocean Renewable Energy ◽

10.1115/omae2020-18894 ◽

2020 ◽

Author(s):

Amirkhosro Kazemi ◽

Oscar Curet ◽

Daniel Gómez ◽

Eduardo E. Castillo

Keyword(s):

Energy Harvesting ◽

High Speed ◽

Oscillation Amplitude ◽

Tidal Energy ◽

Tidal Currents ◽

Electric Generator ◽

Hydrokinetic Energy ◽

Energy Devices ◽

Novel Device ◽

Mangrove Roots

Abstract Tidal energy has the potential for future electricity generation to be widely used in intercostal areas during the rise and fall of tides. Inspired by mangrove roots, we designed a novel device to harvest hydrokinetic energy from tidal currents. This device consists an oscillating cylinder, partially submerged in a flow of water and an electric generator composed of a fixed magnet and a coil attached to the cylinder pivoted at its top by a thin flexible steel plate. This energy harvesting system is considered as one-degree-of-freedom vortex-induced vibration (VIV). The oscillation amplitude of the cylinder tip was recorded with a high-speed camera and 2-D PIV measurements were made to explore the hydrodynamic interaction within the devices for Reynolds numbers ranging from 200 to 1500 (based on cylinder diameter) consistent with biological velocity in tidal flows. We analyzed the kinematics as well as the power generation of the device for different stiffness of the plate. We observed that the cylinder was unmoved for low water velocities; however, by increasing the flow velocity the oscillations increase and reached a maximum value; similar fashion was observed for all stiffness. It was found that for a specific range of reduced velocity (0 < Ur < 3.5) the device worked in its optimal range in which the amplitude of oscillations and the efficacy of the system reach the highest values. This analysis of VIV correlated with oscillations will be fundamental for future bio-inspired energy harvesting devices. These renewable energy devices could have applications to power small actuators or sensors to monitor coastal infrastructure.

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