Wave Energy Hyperbaric Device for Electricity Production

Wave energy is a renewable and non-polluting source and its use is being studied in different countries. The paper presents an overview on the harnessing of energy from waves and the activities associated with setting up a plant for extracting energy from waves in Port of Pecem, on the coast of Ceara State, Brazil. The technology employed is based on storing water under pressure in a hyperbaric chamber, from which a controlled jet of water drives a standard turbine. The wave resource at the proposed location is presented in terms of statistics data obtained from previous monitoring. The device components are described and small scale model tested under regular waves representatives of the installation region. Based on the experimental results values of prescribed pressures are identified in order to optimize the power generation.

Continuum Finite Element Methods to Establish Compressive Strain Limits for Offshore Pipelines in Ice Gouge Environments

In the design process for offshore pipelines in ice gouge environments, compressive strain limits provide a basis to assess pipeline mechanical integrity for design load events. A parametric study, using the continuum finite element methods, has been conducted to assess the global pipeline moment-curvature response for displacement-based loading conditions through the post-buckling regime. The purpose of this study was to investigate the accuracy and efficiency of some computational parameters in simulating the stability characteristics of thick pipes. For that, the study used a pipe that has been the subject of a comprehensive and extensive experimental investigation. In specific, the study selected the exact geometric, material, loadings, boundary conditions and operational parameters similar to the BPXA Northstar pipeline system. The numerical analysis examined the effect of element type, mesh density, internal pressure, axial load, end moment, and geometric imperfection mode on the predicted post-buckling response. The analysis demonstrated the importance of element type, mesh density and characteristics of initial geometric imperfections on the post-buckling response of a thick-walled pipeline subject to combine loads. In addition, element performance and solution efficiency was examined.

An Efficient Numerical Model of Hyperbolic Mild-Slope Equation

Introduction of an effective wave elevation function, the simplest time-dependent hyperbolic mild-slope equation has been presented and an effective numerical model for the water wave propagation has been established combined with different boundary conditions in this paper. Through computing the effective wave elevation and transforming into the real transient wave motion, then related wave heights are computed. Because the truncation errors of the presented model only induced by the dissipation terms, but those of Lin’s model (2004) contributed by the convection terms, dissipation terms and source terms, the error analysis shows that calculation stability of this model is enhanced obviously compared with Lin’s one. The tests show that this model succeeds to the merit in Lin’s one and the computer program simpler, computational time shorter because of calculation stability enhanced efficiently and computer memory decreased obviously. The presented model has the capability of simulating exactly the location of transient wave front by the speed of wave propagation in the first test, which is important for the real-time prediction of the arrival time of water waves generated in the deep sea. The model is validated against experimental data for combined wave refraction and diffraction over submerged circular shoal on a flat bottom in the second test. Good agreements are gained. The model can be applied to the theory research and engineering applications about the wave propagation in the coastal waters.

Wave Setup in Inlets: Some Practical Considerations

For the determination maximum flood elevations, a number of components contributing to the total water level need to be considered. For instance, astronomical tide, storm surge, relative changes in mean sea level, wave setup, wave runup and wave splash. In this study, numerical models were used to evaluate under which conditions wave setup penetrates into an idealized inlet. A number of idealized inlet/lagoon configurations were tested. A coupled wave-current model was used to assess the static component of the wave setup. A Boussinesq wave model was used to assess the influence of the dynamic oscillating component of the wave setup. This study demonstrates how numerical modeling tools can be effectively used to assess how wave setup develops depending on a specific inlet configuration.

Certification of Marine Energy Converters: The Experience So Far

In the past few years, DNV has been involved in a variety of projects related to marine energy converters. All projects have been characterised for the handling of technical uncertainties due to the application of new technology or proven technology in different area of application. A systematic approach based on the DNV RP-A203 Qualification of New Technology [1] was applied combined with the Guidelines for Design and Operation of Wave Energy Converters [2] to steer the third party activity, but, more importantly, to allow developers to systematically identify and deal with the risks in a rational manner with traceability of decisions throughout the development of the energy converter. From the very start of our engagement, it was clear that the handling of technical uncertainties was affected, not only by the technical barriers, but also by financial and time constraints. The establishment of the safety and functional targets to be achieved by the energy converter are to be based, not only on the safety and asset integrity aspects, but also on the financial / business model. The experience of using the Qualification process and the Guidelines on these projects, achieving the right balance between the constraints, handling of uncertainties, financial targets and safety and functional requirements, are briefly described in this paper as well as the future steps to be taken to improve the process and consolidate the experience so far. In this paper, it is also addressed the use of the DNV OSS-312 [3] on the certification process of marine energy converters.

On the Transient Response of a Two-Dimensional Floating Runway During Airplane Take-Off

The transient response of a two-dimensional floating runway subject to dynamic moving load due to airplane landing and take-off is studied in this paper. This hydroelastic problem is formulated by directly coupling the structure with fluid, by use of the Level I Green-Naghdi theory for the fluid motion and the Kirchhoff thin plate theory for the runway. The coupled fluid-structure system, together with the appropriate jump conditions are solved by the finite difference method. The results, including hydroelastic deformation of the runway and the drag force on the airplane are predicted and compared with the available results. Favorable agreements are observed. Parametric studies are carried out to identify the important factors for the design of floating runways.

A Fundamental Study About an Activity Trend of NPO of the Seaside Chosen by a Private Sector Management System

Conventionally, the institutions which Autonomy owns do not consider the space requirement that the institution is located in. Therefore, there was not one effective inflection that only an administration method grieved at in all institutions. In 2005, By Local Government Act revision, A management method of the institution which a Autonomy owned was changed of from “Management Trust System” to “A Private Sector Management System”. By this law revision, Regulation was relaxed, and private enterprise/NPO is able to have come to enter it. With it, each institution plays a role as every space, and it is hoped that it is inflected effectively as a high institution of specialty. In this study, I ascertain an activity trend of NPO juridical person and an element of a private sector management system choice requirement, I am aimed at arriving at means to use institutions of Autonomy functionally.

Observations of Breaking and Grouping of Sea Waves

Breaking and grouping of surface waves are observed at Bohai Sea. The measurement system mainly consists of two hydrophones and a pressure sensor underwater. The broadband hydrophones are able to track breaking waves by passive detection of naturally generated ambient sound of breaking. The breaking criterion in terms of Sound Spectrum Level (SSL) is chosen to identify the breaking waves. The simultaneous wave elevation signals are measured with the pressure sensor, to get the wave group information. Special emphasis is put on the portable data acquisition system based on virtual instrumentation, which makes the in situ measurement convenient and user-friendly. By use of the field data, a wave age dependent model for wave breaking probability is reanalysed, and the result shows a good agreement; moreover, the relationship between breaking and grouping is tentatively investigated, the results are in agreement with the earlier findings that breaking was correlated strongly with group structure and occurred most commonly in the center of a group.

A Procedure for Predicting Energy From a Tidal Turbine Farm

A tidal current turbine is a device for harnessing energy from tidal current. A group of tidal current turbines, distributed schematically at a site, is called a tidal turbine farm. A tidal turbine farm has to be located in a confined channel or a straight where consistent high-velocity tidal current flow is available for the cost-effectiveness concern. This narrow geographical condition poses challenges for turbine farm planners to distribute turbines strategically. Turbines’ distribution in a farm affects power generation efficiency and the resultant tidal unit power cost. In this paper, we propose a procedure for predicting energy generation from a tidal turbine farm by investigating the optimal distribution of turbines at a given site. The objective of optimizing the turbines distribution is to maximize the power output efficiency. To fulfill this, we conducted a systematic analysis on power generation from a tidal turbine farm to identify the key factors affecting the optimal tidal turbines distribution with an emphasis on the turbines’ hydrodynamics analysis and briefed the turbine working principle. As a companion paper to Li and Calisal (2007) which discusses the principle of a stand alone turbine, turbine configuration and interactions (i.e. angle of attack, turbine relative distance and turbine size) are extended here. The main assumption of this discussion is that vortex shedding impact is the dominant factor causing the turbine efficiency loss. Considering the turbine design principle, a simplified relationship between turbines distribution and turbine farm efficiency is formulated. Then, numerical simulation results are presented for a given site in British Columbia together with extended general solution.

Preliminary Results of a Vortex Method for Stand-Alone Vertical Axis Marine Current Turbine

Tidal power technology has been dwarfed once to take hold in the late 1970’s, because the early generations were expensive at small scale and some applications (such as barrages) had negative environmental impacts. In a similar working manner as a wind turbine, a tidal current turbine has been recognized as a promising ocean energy conversion device in the past two decades. However, the industrialization process is still slow. One of the important reasons is lack of comprehensive turbine hydrodynamics analysis which can not only predict turbine power but also assess impacts on the surrounding areas. Although a lot can be learned from the marine propeller or the wind turbine studies, a systematic hydrodynamics analysis on a vertical axis tidal current turbine has not been reported yet. In this paper, we employed vortex method to calculate the performance of stand-alone vertical axis tidal turbine in term of power efficiency, torque and forces. This method focuses on power prediction, hydrodynamics analysis and design, which can provide information for turbines distribution planning in a turbine farm and other related studies, which are presented in Li and Calisal (2007), a companion paper in the conference. In this method, discrete vortex method is the core for numerical calculation. Free vortex wake structure, nascent vortex and vortex decay mechanism are discussed in detail. Good agreements in turbine efficiency comparison are obtained with both the newly-designed tidal turbine test in a towing tank and early wind turbine test.