Showing papers on "Wave power published in 2000"

Ion Cyclotron Wave Dissipation in the Solar Corona: The Summed Effect of More than 2000 Ion Species

Abstract: In this paper the dissipation of ion cyclotron resonant Alfven waves in the extended solar corona is examined in detail. For the first time, the wave damping arising from more than 2000 low-abundance ion species is taken into account. Useful approximations for the computation of coronal ionization equilibria for elements heavier than nickel are presented. Also, the Sobolev approximation from the theory of hot-star winds is applied to the resonant wave dissipation in the solar wind, and the surprisingly effective damping ability of "minor" ions is explained in simple terms. High-frequency (10-10,000 Hz) waves propagating up from the base of the corona are damped significantly when they resonate with ions having charge-to-mass ratios of about 0.1, and negligible wave power would then be available to resonate with higher charge-to-mass ratio ions at larger heights. This result confirms preliminary suggestions from earlier work that the waves that heat and accelerate the high-speed solar wind must be generated throughout the extended corona. The competition and eventual equilibrium between wave damping and wave replenishment may explain observed differences in coronal O VI and Mg X emission line widths.

Step wave power converter

Abstract: A single- or multi-phase step wave power converter includes multiple transformers configured to receive DC voltage from one or more power sources. Each of the transformers includes a primary winding and a secondary winding. The transformers are each configured to supply a step for a step wave AC output. Bridge circuits are supplied for controlling input of DC voltage into the primary windings of the transformers. Steps for the step wave AC output are output from the secondary windings based upon the input provided to the primary windings. DC source management circuitry manages which DC power source(s) supplies DC voltage input to each of the bridge circuits. The management circuitry provides seamless power switching between the plurality of DC power sources based on each power source's performance characteristics. A pulse-width modulator can also be provided to the step wave power converter to modulate the input into a selected primary winding. In this way, the step wave AC output can be fine-tuned in substantial conformance with an ideal AC waveform.

Perforated Wall Breakwater with Internal Horizontal Plate

Abstract: The hydrodynamic performance of a perforated wall breakwater with an internal horizontal plate is studied. It is suggested that a horizontally submerged plate be installed inside the wave chamber to enhance the stability of the structure. Based on the linear wave theory, the 2D problem is formulated to analyze the wave reflection with different porosity, physical dimensions, and wave conditions. The method of matched eigenfunction expansions is used to obtain the solution. Generally, the hydrodynamic performance of a wave chamber is similar with or without an internal horizontal plate. However, the minimum reflection occurs at some particular ratios of the length of the wave chamber to the wavelength, which are less than the corresponding ratios for a wave chamber without the plate, because the waves become shorter over the submerged plate. Thus, the size of the wave chamber can be reduced. It is also found that a moderate porosity is optimal to dissipate the wave energy. By investigating the wave-induced force and moment, such breakwaters with an internal horizontal plate can be designed and constructed with a higher degree of confidence and reliability.

Wave power flux and ray-tracing in regions of resonant absorption

Abstract: The propagation of waves in weakly dissipative plasmas is investigated. A new expression for the wave energy flux is obtained, which is proportional to ´mode / k , where ´mode is the real part of the eigenvalue of the dispersion tensor corresponding to the wave mode. Significant differences from the usual definition of dielectric wave energy flux occur in case of a non-negligible anti-Hermitian contribution to the dielectric tensor. This occurs, for example, near electron cyclotron resonance. The direction of the corrected wave energy flux is consistent with that of the trajectory of a wave beam crossing the EC resonance as obtained in Westerhof (Westerhof E 1997 Plasma Phys. Control. Fusion 39 1015). It is shown that ray-tracing near cyclotron resonance can be performed with the use of ´mode as ray-Hamiltonian.

Concerning the local time asymmetry of Pc5 wave power at the ground and field line resonance widths

Abstract: A statistical analysis of transverse wave activity in the Pc 5 frequency band using satellite magnetic field data from a 6 month interval shows a symmetric distribution along the geostationary orbit in the magnetosphere, whereas observations on the ground display an asymmetric distribution with regard to the noon sector with maximum wave activity on the morningside. As a possible cause of these different local time variations of the wave activity, the ionospheric screening effect is discussed, which depends on the radial scale lengths or resonance width of the waves as well as on their azimuthal wave number. It is suggested in this study that a local time variation of the resonance width of the waves is caused by a variation of the radial gradient of the plasma density along the geostationary orbit, leading to a slowly varying efficiency of the ionospheric screening effect with local time. Local time variations of the resonance width thus will be of equal importance to explain the observed asymmetry as, for example, local time variations of wave sources causing local time variations of the azimuthal wave number.

Communication terminal, base station unit and communication method

Abstract: PROBLEM TO BE SOLVED: To provide a communication method, that can quickly decide proper wireless resource assignment and a communication system for conducting communication between a base station unit and a communication terminal. SOLUTION: A complex correlation section 110 applies complex multiplication of a known pattern, to distinguish a signal of each base station with a baseband signal resulting from applying frequency conversion to a known signal sent from a base station unit which is the object of a communication opposite party to have a baseband frequency to conduct inverse spread on the baseband signal and to obtain an amplitude. A desired wave power measurement section 111 averages the amplitude by a prescribed number of symbols, and an interference wave power measurement 112 suppresses the interference wave component for calculating the desired wave power and attenuates the desired wave power from the amplitude to separate the interference wave component. A division section 113 divides the desired wave by the interference wave, to calculate a CIR value and provided an output of it to transmission sections 102-1 to 102-n. The transmission sections 102-1 to 102-n apply processings required for wireless transmission, such as modulation, coding and frequency conversion to the CIR value and transmit the result via an antenna 103. COPYRIGHT: (C)2002,JPO

Controller of pendulum type wave power generator

Abstract: PROBLEM TO BE SOLVED: To obtain a highly economical and reliable controller performing matching control of the wave power energy and a power generation load in a pendulum type wave power generator having a high energy acquisition efficiency, in which unattended operation can be performed in a severe ocean environment without requiring an expensive and delicate electronic apparatus, e.g. a wave height meter, a computer or a servo valve, at all. SOLUTION: A pendulum type wave power generator comprises a pendulum plate 4 disposed rockingly in a water chamber, a rocking pump 5 secured to the rocking shaft of the pendulum plate, and variable capacity hydraulic motors 8 and 8' generating a rotational motion in a fixed direction by receiving pressure oil from the rocking pump. Controllers 10 and 10' being driven by the pressure of fluid in the pipeline control flow rate of the hydraulic motors to be sustained at a level proportional to the average pressure of the pump, and a pressure detector has a sufficient damper function.

A Comparison of Performances of Turbines for Wave Power Conversion

Abstract: A number of self-rectifying air turbines for wave power conversion have been proposed so far. This paper shows the comparison of the performances of all these turbines proposed for use in the near future. As a result, the impulse turbine with self-pitch-controlled guide vanes is found to have the best performance.

Floating wave energy converter

Abstract: A floating ocean wave electrical energy generating apparatus extracts the energy from the normal wave motion The apparatus includes a platform supported at the surface of the ocean by a plurality of buoyant hulls A plurality of ramps extend from below the surface of the ocean and receives the action of a wave and channel that wave power to a discharge end that is elevated with respect to the sea level That energy is harvested by allow the water to fall, by gravity, into water turbines to convert that potential energy into rotational movement The rotation of the turbine is coupled to an electrical generator to provide useful power from the apparatus In the preferred embodiment, each ramp is individually adjustable angularly to account for the frequency and strength of the waves at the particular location where the apparatus is sited

Waves in Rectangular Inlet with Reflecting or Absorbing Walls

Abstract: The behavior of water waves in the vicinity and within an inlet through an idealized barrier island is studied. Two mathematical approaches are used: the first treats the waves in the ocean and bay with Fourier transforms; and the second uses “buffer” domains, which permit the far-field waves to be treated by eigenfunction expansions. The first method is used to treat an inlet with reflective vertical sidewalls. In nature, inlets lined with armor stone absorb wave motion; therefore, the second method is used with impedance boundary conditions at the inlet sidewalls to reduce the wave energy propagating down the channel and into the bay. Wave patterns in the inlet can vary significantly with the angle of incident wave and so can the direction of the radiated wave field in the bay.

Converter for energy of water power, wave power and wind power

Abstract: PROBLEM TO BE SOLVED: To provide a device having a firm structure at a lower cost of equipment to be efficient further with an output of energy equalized to convert energy, in the device of strong structure converting energy of water power on the water surface and in the underwater, wave power and wind power. SOLUTION: In a structure positioned on the water surface or in the underwater to make buoyancy adjustable, this converter device for energy of wave power and wind power, by providing a wave back member in the forward of a wave advancing direction of this structure to generate a forward/backward flow in the water surface with a wave colliding against this wave back member also providing water turbine rotated by the forward/backward flow before the wave advancing direction of the wave back member, obtains energy by rotation of this water turbine, also, by arranging a wind direction member turned corresponding to a wind direction on the water surface in an upper part of the structure and providing a windmill in this wind direction member, obtains energy by rotation of this windmill.

One-dimensional Analysis of Impulse Turbine with Self-pitch-controlled Guide Vanes for Wave Power Conversion

Abstract: A classical one-dimensional analysis in turbomachinery was presented to estimate aerodynamic characteristics of an impulse turbine with self-pitch-controlled guide vanes which is proposed by the authors for ocean wave power conversion. With some simplified assumptions, the efficiency vs/flow-rate coefficient curves were calculated and compared with the experimental results both in a unidirectional steady flow condition and a sinusoidally oscillating flow condition. The estimated results reveal a behavior of the actual characteristics curve of the turbine. Possibility of further improvement in efficiency was discussed from a viewpoint of specific speed and specific diameter.

Flexible Response Reduction on a Very Large Floating Structure due to OWC Wave Power Devices

Abstract: A very large floating structure has hydro-elastic responses that are an elastic deformation and a slowly varying drift motion. Generally, a breakwater is established to reduce the responses. However, it is very difficult to construct it from technical point of view and costs when the water depth increases. Therefore, it is necessary to develop the response reduction system for a very large floating structure even in open seas.In this paper, a new hydro-elastic responses reduction system of a very large floating structure by using wave energy absorption devices has been proposed. The characteristics of hydro-elastic responses of an elastic structure with wave energy absorption devices were investigated both experimentally and numerically. This new system was proved effective in reduction of hydro-elastic responses of a very large floating structure. Two numerical analysis methods were developed to estimate hydro-elastic responses of a very large floating structure. The results obtained by these methods give a good agreement with the experiment results.

A vibration detector and ultra sonic vibration generator for anti-scale of boiler

Abstract: PURPOSE: An apparatus for generating ultrasonic wave and detecting oscillation for preventing boiler scaling is provided to minimize the whole circuit arrangement and malfunction by adopting PLD(Programable Logic Device) and generating ultrasonic wave uniformly, and to improve the reliability of operation by adopting IGBT(Isolated Gate Bipolar Transistor) as a power switching element to increase the operation speed and expand the frequency range of the ultrasonic wave. CONSTITUTION: An apparatus for generating ultrasonic wave and detecting oscillation for preventing boiler scaling includes an ultrasonic wave power generation part(100) having a reference signal generating circuit(110) having frequency demultiplier, an ultrasonic wave generating circuit(120), an ultrasonic wave power driving circuit(130), an ultrasonic wave power amplification circuit(140), an ultrasonic wave oscillator(150), a current transformer(160), a display(170), an ultra wave frequency display(180), and a frequency display(190), and an ultrasonic wave oscillation detection and display part(200) having an oscillation sensor(210), a circuit for amplifying oscillation signal and driving cable(220), a connection cable(230), a circuit for receiving the ultrasonic wave and amplifying signals(240), and an oscillation display(250).

A statistical study of the dependence of the integrated wave power of geomagnetic pulsations between 0.1 Hz and 1.0 Hz upon the solar wind dynamic pressure

Abstract: We present a statistical study of the influence of the solar wind dynamic pressure on the power of geomagnetic pulsations in the frequency range of 0.1 to 1.0 Hz (around the superposition of the Pc1 and Pc1--2 frequency ranges). The solar wind parameters are calculated using data from the Solar Wind Experiment and from the Magnetic Field Instrument on board the WIND spacecraft. Using ground data from the Antarctic AGO arrays and northern hemisphere stations we have compared the integrated power of pulsations between 0.1 and 1.0 Hz with the variations of the solar wind dynamic pressure, on scales of several hours. On the dayside there is a better than 80% correlation between increases/decreases of solar wind dynamic pressure and enhancements/ depletions of wave power. Many wave events occur during periods of constant solar wind dynamic pressure. These results suggest that the wave production mechanism driven by the magnetospheric compression due to solar wind dynamic pressure represents a trigger of the ULF waves produced in the outer magnetosphere and recorded on the ground. The presence of the waves during periods of low constant solar wind pressure is not in contradiction with our proposed mechanism, it just means that the dynamic pressure is not the only compression mechanism.

Impulse Turbine with Air Flow Rectification System for Wave Power Conversion.

Abstract: In order to develop a high performance impulse turbine with air flow rectification system for wave power conversion, the impulse turbine has been designed and investigated experimentally by model testing. Then' the running and starting characteristics in irregular ocean waves have been evaluated by a computer simulation, taking account of energy conversion efficiency of oscillating water column. As a result, a suitable choice of design factors has been suggested for the setting angle of guide vane and rotor profile.

Basic Study of Pneumatic Wave Power Conversion System with Water Valve Rectifier.

Abstract: It is necessary to utilize natural energies positively to reduce CO2 in the atmosphere. Wave energy surging upon the Tohoku area coast estimated to total about 13 million kW is viewed as a future energy source. We discussed a practical generating system using wave power, and now propose an original method. We describe the composition of our power generating system with water valve rectifier and present experimental test results. We also discuss the basic characteristics of the wave power generating system using our model system.

A study on Dynamics of Ocean Observation Platform with Wave Power Devise

Abstract: Model experiments and numerical simulations on motions and mooring tensions of an ocean observation platform were made for the design of the mooring system and platform. The platform is under development for the study of green house effects and is planned to be moored in very rough sea area of 5000m depth. The performance of wave power device, which is installed in the platform to supply the electric power for instruments used in the chemical, biological and physical measurements, is also discussed based on pressure variations generated in the air chamber of the platform model.In general, results of numerical simulations showed good agreement with those of experiments, though a few points needing improvement were discussed.

Electron Heating in Tokamak LHCD Experiment

Abstract: Collisional damping and Landau damping of the lower hybrid wave in LHCD experiment are analytically studied. For a medium size tokamak like HL-1M and HT-7 where typical central electron temperature is around 1 keV, electron heating via collisional damping could be relatively large, while the absolute damping rate is usually small. The mode conversion of the slow wave to the fast wave due to the downshift of parallel refractive index would lead to edge heating. A quasi-linear wave power damping is estimated for a full LH driven plasma which is an order of magnitude smaller than the experimentally injected wave power for plasma with Te around 1 keV.