Showing papers on "Wave power published in 1999"

Coupled hydromagnetic wave excitation and ion acceleration at interplanetary traveling shocks and Earth's bow shock revisited

Abstract: A revised version of the self-consistent theory of ion diffusive shock acceleration and the associated generation of hydromagnetic waves is presented. The theory generalizes and corrects the theory of Lee [1982, 1983]. Lee assumed a linear dependence of the anisotropic part of the ion distribution function on the cosine of the ion pitch angle. Here the wave growth or damping rate is again calculated using linear theory, but a more general ion anisotropy is calculated using the pitch angle diffusion equation. The wave intensity satisfies a wave kinetic equation, and the ion omnidirectional distribution function satisfies the energetic particle transport equation. These coupled equations are solved numerically and compared with an analytical approximation similar to that derived by Lee. The analytical approximation provides an accurate representation of both the proton distribution and the wave intensity. A comparison is made between the predicted wave magnetic power spectral density adjacent to the shock as a function of frequency and the wave spectrum measured by ISEE 3 at the November 11–12, 1978, interplanetary traveling shock. There is excellent agreement between the predicted and measured power spectral density in the frequency range of 0.03–0.3 Hz. A comparison is also made between the predicted total wave energy density and that observed upstream of Earth's bow shock by the AMPTE/IRM satellite for a statistical survey of ∼400 near-to nose events from late 1984 and 1985. This comparison revises the result presented by Trattner et al. [1994]. The correlation between the observed wave power and that predicted, based on the observed energetic proton energy density, is very good with a correlation coefficient of 0.92. However, the average observed wave magnetic energy density is ∼63% of that predicted, suggesting possible wave dissipation which is not included in the theory.

An Overview of Wave Energy Technologies: Status, Performance and Costs

Abstract: Work on wave energy within the UK began in the early 1970s with a report from the Central Policy Review Staff, which identified the Government's responsibility to assess a wide range of possible energy options to ensure security of energy supplies The UK Department of Energy (DEn) funded extensive research into wave energy during the period 1974 to 1983 under its Wave Energy Programme The programme objectives were to establish the feasibility of extracting energy from ocean waves and to estimate the cost of energy if used on a large scale to supply UK needs The latter objective was addressed by setting a design aim to establish a 2 GW wave power station situated off South Uist in the Outer Hebrides of Scotland During the course of the programme a large number of devices were considered but found to be uneconomic (ETSU, 1985) With hindsight, the objective of that programme was over ambitious and resulted in massive devices, with corresponding high capital and generating costs

Resonant optical wave power control devices and methods

Abstract: An optical wave power control device and method enables signal control, such as modulation and switching, to be effected within an uninterrupted propagation element, e.g. an optical fiber or planar waveguide. The propagation element is configured such that a portion of its wave guided power encompasses the exterior surface of the element, intercepting the periphery of an adjacent high Q volumetric resonator. Power of a chosen resonant wavelength is coupled into the resonator, where it circulates with very low loss in accordance with the principles of a whispering gallery mode device, and returns energy to the propagation element. By introducing loss within the resonator, the propagated power can be varied between substantially full and substantially zero amplitudes. Loss factors can be maintained such that the resonator is overcoupled, i.e. parasitic losses are less than coupling losses, and a critical coupling condition exists in which a small swing in the control effect causes a disproportionate change in the optical output signal.

Fast wave current drive in H mode plasmas on the DIII-D tokamak

Abstract: Current driven by fast Alfven waves is measured in H mode and VH mode plasmas on the DIII-D tokamak for the first time. Analysis of the poloidal flux evolution shows that the fast wave current drive profile is centrally peaked but sometimes broader than theoretically expected. Although the measured current drive efficiency is in agreement with theory for plasmas with infrequent ELMs, the current drive efficiency is an order of magnitude too low for plasmas with rapid ELMs. Power modulation experiments show that the reduction in current drive with increasing ELM frequency is due to a reduction in the fraction of centrally absorbed fast wave power. The absorption and current drive are weakest when the electron density outside the plasma separatrix is raised above the fast wave cut-off density by the ELMs, possibly allowing an edge loss mechanism to dissipate the fast wave power since the cut-off density is a barrier for fast waves leaving the plasma.

The mobility functions and their application in calculating power flow in coupled cylindrical shells

Abstract: The mobility functions of semi-infinite and finite cylindrical shells are useful in calculating the structural wave power flows in coupled pipeline systems. However, their expressions and characteristics are not available in the existing literature. In this paper, the mobility functions of elastic cylindrical in vacuo shells have been numerically studied and applied to estimate both the input power and the power flow in coupled finite cylindrical shell systems.

Wave energy absorber of the oscillating water column type

Abstract: A wave power generating apparatus is provided with a plurality of L-shaped ducts and floats. The ducts are composed of vertical and horizontal ducts. The vertical ducts each have an air chamber thereon where an impulse turbine and an electric power generator are installed. Each float has a vertical square pillar and a vertical rear half cylinder attached thereto, and is fixedly attached onto the horizontal duct. The apparatus has high efficiency to convert wave power to electric power and needs low mooring force to keep the apparatus on an offshore.

Performance Studies On a Scaled Model of Backward Bent Ducted Buoy (BBDB) Type Wave Energy Converter In Regular And Random Waves

Abstract: The National Institute of Ocean Technology (NIOT), in cooperation with IIT-Madras is actively engaged in research and development of ocean energy resources. As a part of the continuing research on wave energy converters and power systems, NIOT initiated a joint research project on floating Backward Bent Ducted Buoy converters, in collaboration with the Pacific Society, Japan. Using the model test results conducted elsewhere, a smaller model suitable for testing in the wave tank facility at IIT-Madras was designed. A number of parameters such as the pressure developed inside the device, the elevation inside the chamber, the pneumatic power that can be extracted and the average wave to pneumatic power conversion efficiency in real seas have been measured. This paper discusses the performance of a BBDB device under regular and random wave conditions.

Research on fundamental performance of multi-floats type wave energy conversion system

Abstract: To improve the wave energy conversion system previously reported, element technologies are examined with a small size model using a U tube to generate wave motion. The effect of inertia terms in the moving parts is examined by obtaining the period response of the electric power and the efficiency. The mathematical model to simulate the experimental conditions is constructed and the simulation results are compared with the experimental. Moreover, the new type is proposed to reduce the parts and the effect is examined.

Accumulated wind and wave power plant

Abstract: Disclosed are the components and processes to produce and install a functional accumulated power plant to convert and store marine wind and wave energy mechanically offshore, transmission of the energy by high pressure fluid means through a novel hydraulic, steam and pneumatic engine to a similar storage facility on land for end uses.

Tidal wave power generating method

Abstract: PROBLEM TO BE SOLVED: To generate a large electric power by collecting many waves and increasing a reciprocating air flow rate in an air chamber. SOLUTION: A high pedestal 6 is built on a shore or an off-shore, a water tank 1 is installed thereon, and an opening wall 2 pointing to an open sea is provided with a divergent side wall and an inclination bottom 4 to produce the concentrated effect and the shallow effect of a tidal wave. The divergent inclination bottom 4 is structured such that, for example, the long pieces of comb-tooth-form bottom plates positioned facing each other are engaged in an inserting state with each other and mounted alternately on two side walls, the inclination angle of the bottom is also changed according to the width thereof and the height of the pedestal and the height of an artificial small tidal wave is freely controlled. This constitution widely collects waves and more increases a wave height, as the more the wave approaches the water tank 1, pumps up water from the opening wall 2, moved according to a storage water level, to the water tank 1, and rotates a water turbine 7 by continuously running a large quantity of waves after dynamic energy of waves is converted to energy in a static position to generate a large electric power.

Power generation system based on wave power pump, and pumping system

Abstract: PROBLEM TO BE SOLVED: To provide a power generation system which enables continuous water supply and power generation, by using a circulation wafer feeding system of pumping up water stored in a lower tank in order to store it in an upper tank and drop it onto the lower tank according to upward and downward movement of the respective float devices provided on a plurality of wave power pumps. SOLUTION: When a float device 16 for each wave power pumps 10 provided on a plurality of erected columns 14 is moved upward and downward by wave motion, water W stored in a lower tank 3 is pumped up to be stored in an upper tank 2, and then, the water W stored in the upper tank 2 is dropped to the lower tank 3 so as to drive a hydraulic power generator 5. After driving, dropped water W is pumped up again from the lower tank 3 so as to be circulated.

Method and device for measuring electronic wave characteristic

Abstract: PROBLEM TO BE SOLVED: To accurately measure such electronic wave characteristics as desired wave power and interference wave power simply with a simple operation, by providing a means for estimating the characteristics of the propagation path of electronic waves from a received and demodulated reference signal in a signal-processing system. SOLUTION: A measuring device 10 of electronic wave characteristics being applied to, for example, a CDMA-system portable telephone for performing space diversity synthesis is provided by holding, in common, the demodulation part of an audio signal/a pilot signal corresponding to each of signal-processing systems 11 and 12 of the telephone and propagation path estimation parts 14 and 21. The propagation path estimation part 14 obtains a propagation estimation value including information on a phase rotation and an envelope by the method of moving averages or the like for data being inputted successively, and obtains a received power SI of a desired wave based on the value. Interference wave power I1 is obtained based on a residue being obtained by subtracting the propagation path estimation value from a demodulation signal PD1 of a pilot signal, and a synthesized, desired wave power S, an interference wave power I, and their ratio SIR are obtained from the output of both processing systems 11 and 12.

Wave power generating system by up and down motion of float

Abstract: PROBLEM TO BE SOLVED: To provide a wave power generating system capable of making use of natural energy to obtain electric power and contributing a pollution problem worldwide without providing any equipment having complicated structure in the present condition for testing a generating method making use of compressed air by wave motion of the sea at the present time. SOLUTION: In a state to always float a float 1 on the surface of the water, a vertically movable shaft 4 and a power transferring gear 6 are mounted to the upper part of the float 1, and when the float 1 makes up and down motion, a main shaft is rotated through one way gears 5. In order to obtain continuous power, a plurality of structures are interlocked (series) to make it possible to operate continuously. A plurality of one way gears 5 are used to obtain energy from both directions when the float 1 can be moved upward and downward.

Characteristic Velocities for Higher-Order Stokes Waves in Deep Water

Abstract: The accuracy of asymptotic expressions for phase, wave energy, and wave action velocities for steady, plane gravity waves progressing in deep water and with no ambient currents is investigated. The calculations are to a large extent based on Fenton’s fifth-order Stokes’ wave theory. Using the dispersion relation correct to sixth order for arbitrary water depth, the phase velocity is calculated to fourth order in wave steepness for infinitely deep water; this is in accordance with a number of previously found results. Potential and kinetic energy is calculated, which leads to the energy density correct to sixth order. Comparison with previous findings showed one discrepancy, which can however be explained. Also, the energy flux is found correct to sixth order, leading to a fourth-order expression for the wave energy velocity. From sixth-order action and action flux results, the wave action velocity is finally calculated correct to fourth order. Agreement with more accurate numerical results is excellent for all three velocities except near the wave of maximum steepness. Practical asymptotic formulas are introduced, enabling one to calculate the characteristic velocities explicitly from given wave height and period. Two new exact relations between integral properties for deep water with no current are presented.

Travelling Wave Discharges in Nitrogen: Modelling and Experiment

Abstract: This work is concerned with the study of travelling wave discharges in molecular gases. Specifically, as an illustrative example a theoretical and experimental study of a surface wave (SW) discharge in nitrogen is presented which incorporates a detailed self-consistent analysis of plasma kinetics and wave electrodynamics.