Showing papers on "Wave power published in 2005"

Multiphysics simulation of wave energy to electric energy conversion by permanent magnet linear generator

Abstract: The possibility to use three-phase permanent magnet linear generators to convert sea wave energy into electric energy is investigated by multiphysics simulations. The results show a possibility, which needs to be further verified by experimental tests, for a future step toward a sustainable electric power production from ocean waves by using direct conversion. The results suggest that wave energy can have an impact on tomorrow's new sustainable electricity production, not only for large units, but also for units ranging down to 10 kW. This gives wave power a larger economical potential than previously estimated. The study demonstrates the feasibility of computer simulations to give a broad, and in several aspects a detailed, understanding of the energy conversion. The simulation results also give a useful starting point for future experimental work.

A Nearshore Wave Energy Atlas for Portugal

Abstract: The nearshore wave energy resource in Portugal has been assessed through the development of ONDATLAS. This is an electronic atlas, compatible with Internet access, containing comprehensive wave climate and wave energy statistics for 78 points at about 20 m water depth spaced variably ca. 5 km to 30 km, 5 points at deep water and 2 points at open ocean locations. The data were produced by a third-generation wind-wave model, complemented by an inverse-ray model that computes the directional spectra transformation from open ocean to the near-shore. Shoaling, refraction, bottom dissipation and shelter by the coastline and/or neighbouring islands are taken into account. ONDATLAS statistics comprise yearly and monthly values, variability and probability data for significant wave height, energy (mean) period, peak period and wave power, and directional histograms for wave and power direction. Joint probability distributions for various combinations of the above parameters are also available, as well as extreme values and return period for wave height and period parameters. A summary of the detailed verification of this model using long-term buoy measurements at four sites is presented. The main characteristics of ONDATLAS are described. The strong spatial variability that wave conditions exhibit at the coastal area are illustrated and a brief assessment of the nearshore resource at the Portugal mainland is presented.Copyright © 2003 by ASME

Design, modelling and test results of the AWS PM linear generator

Abstract: The Archimedes Wave Swing (AWS) is a system that converts ocean wave energy into electrical energy. A pilot plant of this system has been built. This paper describes the design of the permanent-magnet (PM) linear synchronous generator applied in the AWS. Based on a magnetic circuit model, it is concluded that saturation does not play an important role. The correlation between measured and calculated generator parameters and no-load voltage is reasonable, which indicates that the generator is adequate.

Wind wave statistics in Tallinn Bay

Abstract: The wind wave regime of Tallinn Bay, Gulf of Finland, is analysed with the use of a simplified method of long-term computations of wave fields based on a high-resolution nested WAM model and Kalbadagrund (1991-2000) wind data. The distributions of probabilities for wave heights, annual and seasonal mean wave heights, density of wave energy and its flux (wave power), and 1-year return wave heights as well as the wave field properties in extreme storms are computed. The mainland and surrounding islands together with numerous shallow areas shelter the bay from waves coming from the dominating strong wind directions. The average wave properties exhibit a significant seasonal and spatial variability. The highest waves occur in the vicinity of the Tallinn-Helsinki ship lane where the significant wave height exceeds 2 m each year and may reach 4 m in extreme NNW storms.

Ground observations of high‐latitude Pc3‐4 ULF waves

Abstract: [1] A detailed study has been undertaken of Pc3-4 waves recorded on the ground with the IMAGE magnetometer array (56° 0.6) across the entire station array. Most of these had well-defined wave packet appearance in time series records and a clear peak in power spectra. Their occurrence and frequency suggest the waves are generated by the upstream ion-cyclotron resonance mechanism, with no evidence of generation by the Kelvin-Helmholtz instability. For each event the amplitude, phase, coherence, ellipticity, azimuth angle, and degree of polarization across the ground array were examined. The coherence length, azimuthal wave number, and hence the apparent wave propagation velocity were thus determined, with emphasis on the precision and significance of these measurements. It was found that these daytime Pc3-4 pulsations usually have maximum amplitude near the magnetopause projection, meridional coherence lengths of order 1.5–2.0 × 103 km, and low azimuthal wave numbers during morning hours, averaging around −4.0 (indicating westward propagation). Over 80% of events propagated poleward and westward, with average equivalent ground velocity of 41 km/s N43°W for the H component. About 24–30% of the events are higher harmonics of field line resonances. There is no evidence that the remaining events arise from cavity modes or localized modulated electron precipitation. The observations instead suggest a mechanism involving mode coupling and field-guided propagation. In this model, fast mode waves in the Pc3-4 range entering near the subsolar point propagate earthward and due to the inhomogeneity of the magnetosphere couple to the field-guided Alfven mode. At certain latitudes, standing oscillations are established at harmonics of the local resonant frequency, while at other latitudes traveling waves convey energy to low altitudes. The expected L dependence of wave power and travel time agree well with observed amplitude and phase profiles.

Sea-based hydrogen-oxygen generation system

Abstract: A method for generation of gasses contained in a salt solution in accomplished by disposing automated, floating wave power collection vessels in waters distant from shore, the vessels navigating within one or more predetermined geographic zones, having suitable wave conditions for such operation. The wave power devices generating electricity and the gasses are extracted from the salt solution by electrolysis. Automated storage vessels are used as shuttles to deliver the gasses to shore facilities.

Fluctuation, wave power generator

Abstract: The present invention relates to a power generator by using wave a energy source power. It is characterized by that it utilize the wave to drive internal elastic vibrator mechanism and make it operate so as to attain the goal of generating power. Said invention includes includes the following three systems: 1. magnetoelectric power generation system for producing alternative current; 2. piezoelectric power generation system for producing pulse current; and 3. static power generation system for producing direct current.

The STAFF-DWP wave instrument on the DSP equatorial spacecraft : description and first results

Abstract: . The STAFF-DWP wave instrument on board the equatorial spacecraft (TC1) of the Double Star Project consists of a combination of 2 instruments which are a heritage of the Cluster mission: the Spatio-Temporal Analysis of Field Fluctuations (STAFF) experiment and the Digital Wave-Processing experiment (DWP). On DSP-TC1 STAFF consists of a three-axis search coil magnetometer, used to measure magnetic fluctuations at frequencies up to 4 kHz and a waveform unit, up to 10 Hz, plus snapshots up to 180 Hz. DWP provides several onboard analysis tools: a complex FFT to fully characterise electromagnetic waves in the frequency range 10 Hz-4 kHz, a particle correlator linked to the PEACE electron experiment, and compression of the STAFF waveform data. The complementary Cluster and TC1 orbits, together with the similarity of the instruments, permits new multi-point studies. The first results show the capabilities of the experiment, with examples in the different regions of the magnetosphere-solar wind system that have been encountered by DSP-TC1 at the beginning of its operational phase. An overview of the different kinds of electromagnetic waves observed on the dayside from perigee to apogee is given, including the different whistler mode waves (hiss, chorus, lion roars) and broad-band ULF emissions. The polarisation and propagation characteristics of intense waves in the vicinity of a bow shock crossing are analysed using the dedicated PRASSADCO tool, giving results compatible with previous studies: the broad-band ULF waves consist of a superimposition of different wave modes, whereas the magnetosheath lion roars are right-handed and propagate close to the magnetic field. An example of a combined Cluster DSP-TC1 magnetopause crossing is given. This first case study shows that the ULF wave power intensity is higher at low latitude (DSP) than at high latitude (Cluster). On the nightside in the tail, a first wave event comparison - in a rather quiet time interval - is shown. It opens the doors to future studies, such as event timing during substorms, to possibly determine their onset location.

Parametric Decay During HHFW on NSTX

Abstract: High Harmonic Fast Wave (HHFW) heating experiments on NSTX have been observed to be accompanied by significant edge ion heating (Ti >> Te). This heating is found to be anisotropic with Tperp > Tpar. Simultaneously, coherent oscillations have been detected with an edge Langmuir probe. The oscillations are consistent with parametric decay of the incident fast wave (ω > 13ωc) into ion Bernstein waves and an unobserved ion‐cyclotron quasi‐mode. The observation of anisotropic heating is consistent with Bernstein wave damping and the Bernstein waves should completely damp in the plasma periphery as they propagate toward a cyclotron harmonic resonance. The number of daughter waves is found to increase with rf power and to increase as the incident wave’s toroidal wavelength increases. The frequencies of the daughter wave are separated by the edge ion cyclotron frequency. Theoretical calculations of the threshold for this decay in uniform plasma indicate an extremely small value of incident power should be required to drive the instability. While such decays are commonly observed at lower harmonics in conventional ICRF heating scenarios they usually do not involve the loss of significant wave power from the pump wave. On NSTX an estimate of the power loss can be found by calculating the minimum power required to support the edge ion heating (presumed to come from the decay Bernstein wave). This calculation indicates at least 20–30% of the incident rf power ends up as decay waves.

Theory of dispersive shear Alfven wave focusing in Earth's magnetosphere

Abstract: [1] It is shown that perpendicular gradients in shear Alfven wave (SAW) dispersion regulate the localization of wave power on nightside geomagnetic L-shells where narrow Field Line Resonances (FLRs) form. We estimate the timescale for this process, ω0tc = 1/, and demonstrate that it is analogous to optical wave focusing. Here, β is the gradient in the global wave dispersion parameter across L-shells in the equatorial plane, and α is the gradient in the SAW eigenfrequency. It is demonstrated that dispersive SAWs with wave numbers and frequencies in a certain range, are subject to magnetospheric focusing onto L-shells where they reach large amplitude and are expected to dissipate. Our theory addresses a class of arc scales that are comparable to the electron inertial length near the ionosphere, or the ion gyroradius near the equatorial plane. We further demonstrate that when the gradient in the SAW frequency reverses across the edges of auroral density cavities, it naturally traps dispersive SAWs and focuses them down to the inertial scale.

Wave power technologies

Abstract: The oceans contain a vast amount of mechanical energy in form of ocean waves and tides The high density of oscillating water results in high energy densities, making it a favorable form of hydro power The total US available incident wave energy flux is about 2,300 TWh/yr The DOE Energy Information Energy (EIA) estimates 2003 hydroelectric generation to be about 270 TWh which is a little more than a tenth of the offshore wave energy flux into the US The fact that good wave and tidal energy resources can be found in close proximity to population centers and technologies being developed to harness the resource have a low visual profile, makes this an attractive source of energy Recent advances in offshore oil exploration technology and remote management of power generation systems has enabled significant progress in advancing technology development by simple technology transfer A few systems have made it to full-scale prototype stage allowing experience to be gained from operational aspects which is a critical aspect to develop economic models However, despite enormous progress over the past 5 years, current and wave power conversion technologies are at an immature stage of development This is shown by a lack of accepted standards, a wide range of technical approaches and large uncertainties on performance and cost of these systems

Energy storage considerations for a stand-alone wave energy plant

Abstract: Despite several wave energy plants based on oscillating water column concept having been tested worldwide, wave energy has not yet gained popularity as a renewable energy source because of highly intermittent nature of available wave power. Still maintaining a constant voltage and frequency at the output, requires embedding of energy storage devices of sufficient capacity into the system. As the first stage, an impulse turbine is used to convert differential air pressure due to the oscillating water column into mechanical shaft power. A permanent magnet based alternator driven by this turbine generates variable voltage variable frequency AC, which is rectified to DC by a diode bridge. At the second stage, a DC motor - alternator set converts this into fixed frequency, fixed voltage AC acceptable as a utility AC supply. Employing MATLAB-Simulink based steady-state model of the plant and assuming an adjustable load, PID control of the output load is carried out in order to estimate the energy storage requirement especially under different climatic conditions

Nonbreaking Wave Forces on Multiresonant Oscillating Water Column Wave Power Caisson Breakwater

Abstract: Experimental measurements of in-line wave forces on a 1:50 scale model of an array of multiresonant oscillating water columns (MOWCs), a free-standing wave energy caisson, are reported. Wave forces on a vertical wall were measured and compared with Sainflou's and Goda's formulas, which serve as base for studying wave forces on an MOWC array. A range of hydrodynamic parameters with different damping of the OWC chamber and center-to-center (c/c) spacing were used. In general, the force on the MOWC caisson array is twice that of the vertical wall for maximum damping of the OWC chamber. Reduction of damping of the OWC air chamber reduces the force on the array of caissons by 35-60% of the force on a vertical wall. It is found that shoreward force magnitude is greater than seaward. For spacing of 2-3 times the harbor width, the OWC array acts like a perforated breakwater, experiencing 60% of wave forces on the vertical wall, while for a c/c spacing range of 4-5, it behaves like a vertical wall. Incorporation of an air pressure release by pass system for the OWC chamber is recommended, as this will reduce in-line wave forces on a caisson array to a range of about 35-40%. The nonlinear response of the OWC on wave forces warrants the use of a numerical model and further investigation.

Gravity type foundation for off-shore wind power generation device

Abstract: PROBLEM TO BE SOLVED: To install an off-shore wind power generation device in open-sea where the off-shore wind power generation device can show great power generation capacity by enabling the off-shore wind power generation device to be installed with relatively low capacity caisson, minimizing construction time on sea, making acting wave power small, and making slide resistance force large in a gravity type foundation for the off-shore wind power generation device using the caisson. SOLUTION: The pre-cast gravity type caisson 3 manufactured beforehand in an on-shore yard or the like is composed of a round bottom plate 4, a cylindrical lower part side wall 5 rising as one unit from an outer circumference part of the bottom plate 4, an upper side wall 6 of a small diameter cylinder shape, and a truncated conical taper side wall 7 connecting the lower part side wall 5 and the upper part side wall 6 as one unit. Acting wave power is made small by making area to be resistance close to still water level and using a cylindrical surface on which wave power acting is small, and sliding resistance force of the caisson 3 is made large by making friction resistance large by a friction increase mat 8 on a caisson bottom surface, increasing grounding force by using high specific gravity material 9 as a material filled in. COPYRIGHT: (C)2007,JPO&INPIT

Lower Hybrid Wave Current Drive Efficiency on the HT-7 Tokamak

Abstract: Lower hybrid (LH) wave current drive efficiency on our HT-7 tokamak has been investigated based on the hot electrical conductivity theory. The interaction of the residual toroidal electric field with fast electrons has been included in the determination of current drive efficiency. The LH wave power scan was performed in the plasma parameter ranges of Ip = 50–156 kA, e = 0.5×1019–1.6×1019 m−3, PLH = 50–350 kW. The current drive efficiency is derived to be about 0.1×1019–0.4×1019 Am−2W−1 on the HT-7 tokamak, which depends on the electron density and the LH wave phase velocity. At the electron density of about 1.5×1019 m−3, with the LH wave parallel refraction index peaked at 1.8, the highest current drive efficiency was obtained. A more generally normalized method is introduced to analyse the experimental data, which combines all the data in one curve. The normalized parameters are independent of the plasma parameters.

Spatial significant wave height variation assessment and its estimation

Abstract: Significant wave height is a very important variable used in ocean engineering studies. Spatial variation of the significant wave height is very important for wave energy abstraction studies which is highly dependent on the wave climate. Significant wave height and period are two of the most important wave features that directly affect the energy production. In nature these two variables exhibit temporal randomness and spatial changes. These variations cause heterogeneous regional dispersion of wave energy. In order to assess regional energy distribution, it is necessary to use the concept of regionalized variables through geostatistical methods. The main purpose of this paper is to evaluate the spatial characteristics of significant wave height by the point cumulative semivariogram approach leading to a standard regional dependence function (SRDF) based on concepts of the semivariogram. It is also possible to estimate the unmeasured station value from the closest stations by using SRDF and determine the optimum station intervals. The SRDFs are obtained from available spatial data decreasing with distance for a given set of sites. The wave energy resource in a region of the Pacific Ocean off the west coast of the United States has been evaluated as the application of proposed methodology. It is found that spatial modeling of the region considered can be achieved by using the SRDF function in acceptable error limits.

Numerical simulation of wave power devices using a two-fluid free surface solver

Abstract: A generic two-fluid (water/air) numerical model has been developed and applied for the simulation of the complex fluid flow around a wave driven rotating vane near a shoreline in the context of a novel wave energy device OWSC (Oscillating wave surge converter). The underlying scheme is based on the solution of the incompressible Euler equations for a variable density fluid system for automatically capturing the interface between water and air and the Cartesian cut cell method for tracking moving solid boundaries on a background stationary Cartesian grid. The results from the present study indicate that the method is an effective tool for modeling a wide range of free surface flow problems.

Design and performance analysis of impulse turbine for a wave energy power plant

Abstract: Wave energy is the most abundant source of renewable energy in the World. For the last two decades, engineers have been investigating and defining different methods for power extraction from wave motion. Two different turbines, namely Wells turbine and impulse turbine with guide vanes, are most commonly used around the world for wave energy power generation. The ultimate goal is to optimize the performance of the turbine under actual sea conditions. The total research effort has several strands; there is the manufacture and experimental testing of new turbines using the Wave Energy Research Team's (WERT) 0.6 m turbine test rig, the theoretical and computational analysis of the present impulse turbine using a commercial software package and finally the prediction of the performance of the turbine in a representative wave power device under real sea conditions using numerical simulation. Also, the WERT 0.6 m turbine test rig was upgraded with a data acquisition and control system to test the turbine in the laboratory under real sea conditions using the computer control system. As a result, it is proven experimentally and numerically that the turbine efficiency has been raised by 7% by reducing the hub-to-tip ratio from 0.7 to 0.6. Effect of tip clearance on performance of the turbine has been studied numerically and designed tip clearance ratio of 1% has been validated. From the numerical simulation studies, it is computed that the mean conversion efficiency is reduced around 5% and 4.58% due to compressible flow and damping effects inside OWC device. Copyright © 2005 John Wiley & Sons, Ltd.

Effectiveness of a chamber-type water exchange breakwater and its ability of wave power exteractions by wave induced vortex flows

Abstract: In the previous study on the water exchange breakwater of a water-chamber type, we found out that unidirectional rotational flows are induced in the water chamber driven by wave induced vortex flows from the lower edge of a front curtain wall. In this study, we have examined the possibilities of such vortex flows for wave power extractions. Water mills with a few curved fms have been adopted as a device of wave energy extraction. By installing such water mills in the water chamber, rotational characteristics of the mill and its influences on the wave reflection and transmission as well as on the water exchange rate are clarified. Itwas confirmed that the water mill installed in the water chamber may be used as a wave power extraction device. It was also seen that the installation of the water mill in the water chamber has no influence on the original functions of the breakwater.

Wind power, wave power and solar energy integrated generating set at shallow sea reef area

Abstract: This invention relates to an integrated generating set with wind power, wave power and solar energy in shoal reef, which belongs to renewable energy sources generating field. The device comprises a normal wind-driven generator setting on the mount, a tractive generator operating with wave throw float gravity, solar battery setting in float and generator mount, and epeiric sea frame. The device gives priority to the tractive generator, and uses the normal wind-driven generator and solar photovoltaic battery to assist, by, which can realize synthesis generation. The device is more balance and stable compared with present generation with single renewable energy, and has high efficiency of resource using; meanwhile, it has a big difficulty of construction. ii

Arrangement for utilizing wave power

Abstract: An arrangement for utilizing wave power The arrangement (1) comprises means (4, 4a, 4b, 29a, 29b) for converting the kinetic energy of water into a reciprocating rotary motion The arrangement (1) comprises a conversion unit (8, 8a, 8b) of rotary motion that is arranged to convert the reciprocating rotary motion into a substantially continuous and unidirectional rotary motion, and a power take-off (18) for transferring the unidirectional and substantially continuous rotary motion The arrangement (1) is arranged to be substantially entirely below the surface of water

Surface wave sustained discharge in argon: two-temperature collisional-radiative model and experimental verification

Abstract: Two-temperature collisional-radiative model of surface-wave sustained discharge at atmospheric pressure in a capillary tube is presented. Division of microwave power within the discharge is analysed. Calculations are made for atmospheric pressure argon plasma created inside a quartz tube with and without a liquid cooling coat and a shielding grid. Wave attenuation characteristics and axial distributions of density of dissipated power are presented. The predicted dependence of discharge length on the total flux of wave power is compared with the experimental values.

Parametric Decay during HHFW on NSTX

Abstract: High Harmonic Fast Wave (HHFW) heating experiments on NSTX have been observed to be accompanied by significant edge ion heating (T{sub i} >> T{sub e}) This heating is found to be anisotropic with T{sub perp} > T{sub par} Simultaneously, coherent oscillations have been detected with an edge Langmuir probe The oscillations are consistent with parametric decay of the incident fast wave ({omega} > 13{omega}{sub ci}) into ion Bernstein waves and an unobserved ion-cyclotron quasi-mode The observation of anisotropic heating is consistent with Bernstein wave damping, and the Bernstein waves should completely damp in the plasma periphery as they propagate toward a cyclotron harmonic resonance The number of daughter waves is found to increase with rf power, and to increase as the incident wave's toroidal wavelength increases The frequencies of the daughter wave are separated by the edge ion cyclotron frequency Theoretical calculations of the threshold for this decay in uniform plasma indicate an extremely small value of incident power should be required to drive the instability While such decays are commonly observed at lower harmonics in conventional ICRF heating scenarios, they usually do not involve the loss of significant wave power from the pump wave On NSTX an estimate of the power loss can be found by calculating the minimum power required to support the edge ion heating (presumed to come from the decay Bernstein wave) This calculation indicates at least 20-30% of the incident rf power ends up as decay waves

Numerical modeling of electron energy-time dispersions in the high-latitude part of the cusp region

Abstract: [1] We have constructed a one-dimensional numerical model of electron acceleration with dispersive Alfven waves using realistic parameters based on a rocket observation in the high-latitude part of the cusp region This paper demonstrates that our model could quantitatively reproduce important characteristics of observed electron energy-time dispersions, such as their fluxes, energy range, pitch angle distribution, and source altitudes The energy-time dispersion at the rocket altitude is produced by a time-of-flight effect of magnetosheath-originated electrons accelerated by the resonant interaction with inertial Alfven waves (IAWs) at altitudes of 2000 ∼ 6000 km The higher-energy electrons are generated at higher altitudes The energy-time dispersion changes according to three key parameters: wave power, perpendicular wavelength, and wave frequency The wave power affects the flux and the maximum electron energy, and the perpendicular wavelength affects the source altitude calculated by the time-of-flight analysis, while the wave frequency (time period) affects the time width of the energy-time dispersion We summarize a reasonable set of these parameters for a typical energy-time dispersion observed in the cusp/cleft region Finally, we suggest that the IAWs are generated at the dayside magnetopause in association with magnetic reconnection and then propagate toward the ionosphere along the open field line connected to the magnetosheath Their resonant acceleration of local electrons injected from the magnetosheath at altitudes of several thousand kilometers is the cause for multiple electron energy-time dispersions observed in the high-latitude part of the cusp region

METHOD OF SETTING mu WAVE POWER IN MANUFACTURE OF SEMICONDUCTOR BY USE OF PLASMA, EQUIPMENT FOR MANUFACTURING SEMICONDUCTOR DEVICE USING THE SETTING METHOD, AND METHOD OF MANUFACTURING SEMICONDUCTOR DEVICE USING THE SETTING METHOD

Abstract: PROBLEM TO BE SOLVED: To provide a μ wave power setting method and the like in the manufacture of a semiconductor by the use of plasma, wherein factors, such as the change with time, events or the like, causing fluctuations are eliminated. SOLUTION: An apparatus for manufacturing a semiconductor device is equipped with a Vpp measurement circuit 15 which measures the peak-to-peak voltage Vpp of bias high-frequency signals applied on plasma when a μ wave power is changed, μ wave power-dependent Vpp characteristics are previously grasped, a μ wave power value is set at a μ wave power supply control circuit 17 on the basis of the Vpp characteristics so as to make a Vpp situated in a stable region, and a μ wave power supply 10 is controlled by the μ wave power supply control circuit 17 to output a μ wave power set value so that processes hardly vary even when the processed wafers are increased in number. COPYRIGHT: (C)2005,JPO&NCIPI