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Power Industry
ABSTRACT Electric output characteristics of a new wave power conversion system are discussed. In this system, water valves, not mechanically operated, are combined with air chambers. The advantage of this system is that the rectifying water valves, with no moving parts, suffer less frequent failures. The demonstration test for practical use has been carrying out at Haramachi site since '96. The test plant consists of four air chambers, four water valve chambers, one turbine generator and so on. Air chambers are about 40m in length, 24m in breadth and 24m in height. The electricity, 130kW in specifications, is transmitted to the distribution line. In the demonstration test, we are measuring wave height, pressure in air chambers, water valve chambers and turbine room, electric output and so on. We obtained over 100 time series data from '96 to '98 on condition that the submerged depth of water valve is 10cm. In this paper, typical electric output data are shown and the relationships between sea condition and averaged or fluctuating electric output are discussed. We are planning to change the submerged depth of water valves and number of air chambers in the next phase of demonstration test. These plans are also discussed in the paper. INTRODUCTION Japan is a marine country of insularity surrounded by sea. The mean energy of the waves available at the Japanese seacoast is estimated to be about 6,4–7 kW/m, and the gross value of such energy is estimated to be about 13,400,000 kW(Sugawara, K. et al. 1986). The wave energy is of a low density, the fluctuation of which is high. However, it is clean and is one of those infinitely available.
- Energy > Renewable > Ocean Energy (1.00)
- Energy > Power Industry (1.00)
The Offshore Floating Type Wave Power Device "Mighty Whale": Open Sea Tests
Washio, Y. (Japan Marine Science and Technology Center) | Osawa, H. (Japan Marine Science and Technology Center) | Nagata, Y. (Japan Marine Science and Technology Center) | Fujii, F. (Japan Marine Science and Technology Center) | Furuyama, H. (Japan Marine Science and Technology Center) | Fujita, T. (Japan Marine Science and Technology Center)
Abstract JAMSTEC completed the construction of the prototype device Mighty Whale by May 1998 for open sea tests to investigate practical use of wave energy. Following construction, the prototype was towed to the test location near the mouth of Gokasho Bay in Mie Prefecture. The open sea tests were begun in September 1998, after final positioning and mooring operations were completed. The tests are expected to continue for approximately 2 years. This paper presents an overview of the open sea tests, and summarizes the characteristics of power generation based on the results so far. Introduction JAMSTEC has been engaged in development of ocean-wave energy extraction technology for many years now. In particular, work began in 1987 on "Mighty Whale", which is a floating wave energy device based on the oscillating water column (OWC) principle. It converts wave energy into electric energy, and produces a relatively calm sea behind. This calm area can be utilized for varied applications such as fish farming. Theoretical investigations and model tests in 2 and 3 dimensional wave tanks led to an understanding of the hydrodynamic behavior of the device, and provided information that allowed safe and economical design of the prototype for open sea tests (Length 50m, Breadth 30rn, Depth 12m). Detailed design was completed in 1996. Construction began in January 1997 at the Ishikawajima Harima Heavy Industries Co., Ltd. (IHI) shipyard in Aioi City, Hyogo Prefecture. Prototype construction was completed by May 1998. Following construction, the prototype was towed to the test location near the mouth of Gokasho Bay in Mie Prefecture. Tests were begun in September 1998, after final positioning and mooring operations were completed. The experiments are expected to continue for approximately 2 years. Results are expected to provide a realistic understanding of the performance, safety, and economic features of the device.
- Energy > Renewable > Ocean Energy (1.00)
- Energy > Power Industry (1.00)
Experimental Study On Wave Loads And Responses of a Barge-Mounted Plant With Dolphin-Fender Mooring System
Choi, Yoon-Rak (Korea Research Institute of Ships and Ocean Engineering) | Hong, Seok-Won (Korea Research Institute of Ships and Ocean Engineering) | Kim, Hyun-Joe (Korea Research Institute of Ships and Ocean Engineering) | Kim, Jin-Ha (Korea Research Institute of Ships and Ocean Engineering)
Abstract Model experiment was carried out for a barge mounted plant to assess its safety in harsh environment. The barge mounted plant model was composed of floating structure, dolphin-fender system and mooring cables. The rubber-made fender model was devised to achieve nonlinear characteristics such as hysteresis and buckling behavior of the prototype. The accelerations of platform, reaction forces of fenders, and tensions of mooring cables were measured in regular and irregular waves for various wave directions. The interaction between the floating structure and quay was also investigated using perforated and solid plate quay models. Impulsive response was observed which were caused by the gap between the fender and the dolphin. The responses were analyzed statistically to estimate extreme loads and motion responses. The quay effects somewhat increased the responses. Introduction A research project for utilizing the ocean space and resources in Korea has been started in 1995 (Chung & Chung, 1996). The object of this project is to design and construct a large floating structure, on which plants such as trash burner, electric power plant or desalination plant, etc. are mounted. In the first stage of project, a floating structure was designed as a pilot plant to demonstrate its feasibility and operability (see Fig. I). Assessment of dynamic loads and responses in waves is essential for the design of reliable floating structure and mooting system. A numerical study on the hydrodynamics of the floating structure was already performed, which predicts linear and non-linear wave force and response (Hong et al. 1999). An experimental work on the total system, composed of the floating body and the mooring system, is carried out to validate its safety in harsh environment. This paper contains the results of those model tests in waves.
- Research Report > New Finding (0.40)
- Research Report > Experimental Study (0.40)
ABSTRACT Tidal currents offer a potentially significant source of renewable energy. Studies commissioned by government agencies such as the Department of Trade and Industry in the United Kingdom (UK) and the European Union (EU), through its framework of non-nuclear energy programmes, have shown that the European resource potentially exceeds 12.5 GW installed capacity. Until now, however, estimates of the size of the potential resource and the cost of its exploitation have not taken into account benefits associated with optimisation of operational system characteristics in the context of the local conditions. This on-going project aims to develop a methodology for the optimal matching, both electrical and economic, of tidal current driven turbines to the nature of local flow conditions. INTRODUCTION The need for electricity consumption in factories and domestic requirements is greater than ever as the third millennium nears. At present, the world's electricity production is still heavily reliant upon oil, gas and coal power turbines. Fossil fuels have only a finite lifetime and so alternative sources of energy must be developed. The safety of nuclear installations and general public perception and apathy puts the use of nuclear power in jeopardy with no major plants likely to be constructed in the UK or within the EU countries, it is therefore reasonable to look at alternative sources of electricity production with the active encouragement in terms of research funding by UK and EU governments. Increasingly, electricity generation from renewable sources is being sought and the most promising sources have been hydro-dams, wind and solar. The enormous potential of wave and tidal power however has not been fully exploited. Unlike wind and wave power, tidal currents are virtually inexhaustible though intermittent but predictable and reliable for driving power generation turbines.
ABSTRACT This paper proposes a new type of machine, in which two-stage runners counter-drive, respectively, the outer and the inner rotors of a generator without the usual stator, and discusses performances and internal flow conditions of the model machine. The maximum output power is obtained at the same counter-rotational speeds as expected in the design. Such a machine is suitable for boarding on a floating buoy supplied for the tidal current power generation, because the rotational torques of the machine are counter-balanced themselves. The desirable profile of the buoy is also investigated. INTRODUCTION To cope with the warming global environment, the hydropower should occupy the attention of the electric power generation system as clean and cool energy sources. In such a situation, the tidal current has scarcely been utilized for the power generation, for instance, the Kanmon Straits in Japan has about 54 MW hydraulic energy. It may be suitable, for the tidal current power generation, to apply the high specific speed hydroturbine such as usual axial-flow types, cross-flow types (Toyokura et al.,1990) and/or Darrieus types (Furukawa et al, 1998). It is also desirable to make the machine compact size and simple composition, but the usual generator may reject such desires. That is, it is necessary, for getting sufficiently the electric power, to make the rotor diameter large or equip with the accelerator such as a gear-box, because the electric power is in proportion to the rotational speed in the magnetic field. Therefore, the authors have proposed and developed a new type of generator with counterrotating rotors instead of the usual mechanism, which can make the generator diameter small on account of relatively double the rotational speed.
ABSTRACT The multidisciplinary conversion of ocean wave power for a site off the Australian East Coast is considered. An Oscillating Water Column (OWC) capture device with a parabolic collector wall converts incident wave power to pneumatic power while subsequent conversion to electricity is facilitated by a new air turbine-generator unit. A simple methodology is presented for estimating the air turbine's output and longer-term productivity, according to its sizing. Consequently, a methodology is defined which can be used in determining the optimal turbine diameter for a given wave climate and capture device performance. It is predicted that a 0.73m turbine on the 10m wide Australian plant will have a rated capacity of 300kW and will export 770MWh annually at an average rate of 86kW. INTRODUCTION The beginning to the new millennium has seen a sharp increase in oil prices due to renewed OPEC activity; nuclear power fall from favor due to cost and safety issues; and coal decline further through international commitment to tightening global climate policies. Consequently, the cultural and economic shift towards renewable power continues unabated. The world's ocean waves contain enormous amounts of renewable energy that is dissipated along certain lengths of coastline, although capture devices can now be used to harness this for electricity generation. The Australian wave energy conversion plant presented herein uses a collector wall to concentrate the energy into a semi-submerged air chamber that vents to atmosphere via an air turbine-generator unit (Count, 1980; Ambli et al, 1982; Salter, 1988; French, 1994, Falcao et al, 1994; Whittaker et al, 1997). Initially, the chamber produces an oscillating column of water (OWC) that forces a reciprocating air flow through the turbine-generator unit. The axialflow air turbine is used to create a driving torque from the aerodynamic lift force generated on the blades, pitching and working efficiently in either flow regime.
- Europe (1.00)
- North America > United States (0.68)
- Oceania > Australia > New South Wales (0.28)
- Energy > Renewable > Ocean Energy (1.00)
- Energy > Power Industry (1.00)
ABSTRACT At 1:47 a.m. on September 21, 1999, Taiwan was slammed by its most powerful earthquake measuring 7.3 on the Richter scale in 100 years, struck central Taiwan near the small town of Chi-Chi, Pull Township just 6.9 km from the earth's surface near the epicenter. The shock source time function has a total duration of about 40-sec, the quake had caused over 10,000 casualties, including more than 2,000 deaths. Over 10,000 homes had collapsed. Roads throughout much of Taiwan were rendered impassable and rail traffic was disrupted. Rescue teams spent most weeks searching for survivors in the rubble, and towns across the island struggled to hold last rites and bury the victims. INTRODUCTION At 1.47 am on September 21, 1999, an earthquake measuring 7.3 on the Richter scale rolled outwards from its epicenter 12.5 km from Sun Moon Lake in mountainous central Taiwan, Nantou County. It was only 10.0 km below the Earth surface. The slip distribution thus obtained is quite consistent with the field as an average of about 2–3 m slip along the fault and a maximum slip of about 7–8 m at about 40 km to the north of the epicenter. There were extensive surface ruptures for about 85 km along the Chelungpu faultwith vertical and left lateral strike-slip olivet. The maximum displacement of about 9.8 meters is among some of the largest fault movement ever measured. I'HE EARTHQUAKES While three major quakes in just over a month since August 1999, the world is hit by 18 earthquakes measuring 7.0 or greater every year on average. The three recent large quakes were all probably difference in nature, Taiwan's quake is classified as the "thrust-fault" type. Where one plate slides under another, while Turkey's was a case of two plates grinding against each other.
- Asia > Taiwan (1.00)
- Asia > Middle East > Turkey (0.25)
ABSTRACT A numerical model is developed for 3-D floating body motions in fully nonlinear waves using the BEM. This BEM solves simultaneously the boundary integral equations for the velocity and acceleration fields and the motion equations of a floating body with six-degrees of freedom. The movement of the nodes on the free water surface is evaluated in accordance with the 3-D motion of fluid particle by the Mixed Eularian Lagrangian method (MEL) and it satisfies strictly satisfy the dynamic boundary condition on the water surface. After that, by the coordinate transformation of the six-degrees of freedom motions, the movement of arbitrary nodes on the body surface is evaluated and updated for the next time step. Validity of this numerical model is verified through comparisons with theoretical solutions of nonlinear waves such as the 5th order Stokes and the 3rd order Cnoidal waves, computed results by a fully nonlinear 2D-BEM, and 3-D experimental results of a moored floating plant barge. 1.INTRODUCTION It is necessary to develop a numerical model capable of reproducing fully nonlinear 3-D interactions between a moored floating structure and nonlinear waves. However, such numerical model is still being confined to fully nonlinear 2-D interactions using BEM and FEM. Especially, for the BEM, using boundary surfaces alone, surrounding the fluid domain, the problem of boundary values can be solved. So, the efficiency of computation is much better than the FEM and the BEM is more suitable for 3-D computation. For correct evaluation of floating body motions, it is necessary to correctly calculate the time variation of the fluid pressure acting on a floating body. However, the fluid pressure are affected by the motion acceleration of a floating body. So, the motion equation of the fluid must be strictly coupled up with the motion equation of the floating body.