Showing papers on "Wave power published in 2004"

Wave Power Generator

Abstract: An object is to provide a wave power generator which can convert wave energy to electric energy with high efficiency and supply electric power of a large capacity at low cost and has a simple structure and is low in construction cost. The wave power generator includes a heavy body 3 elastically supported by air springs 4 as elastic members in an enclosing wall 2 on a floating body 1 and an electromagnetic damper as a generating means 7 provided between the heavy body 3 and the floating body 1 . The spring constant of the air springs 4 is adjustable by providing auxiliary tanks in the piston 6 and the floating body 1 so that the undamped natural frequency of the air spring is equal to or close to the frequency of waves within a predetermined frequency ratio ω/ω 0 . Thus, the frequency of the spring system resonates with the frequency of waves, so that the relative movement of the power generating means 7 increases to a maximum and power generation is carried out with maximum efficiency.

The oscillating wave surge converter

Abstract: The Oscillating Wave Surge Converter (OWSC) is a novel shoreline or near-shore wave energy converter. The concept has developed from an analysis of the performance of the LIMPET shoreline oscillating water column. This analysis showed that the hydrodynamics of shoreline wave energy converters are highly non-linear and that they have a qualitatively different response to similar devices that are sited in deeper water. In particular, the water particle motion in shallow water is predominantly horizontal, with elongated wave troughs and heightened wave peaks. The OWSC is designed to couple strongly with the horizontal particle motion, permitting large amplitudes of motion of the working surface whilst minimising energy losses in associated water particle motions. The OWSC consists of a paddle rotating about a horizontal axis above the water surface and perpendicular to the direction of wave propagation. The paddle hangs at the mouth of a gully, effectively forming a 'water column' between the paddle and gully back wall. Thus, the OWSC is similar to the Japanese 'Pendulor' system; however the OWSC uses resonance of the water column rather than harbour resonance as its operating principle. A limited study of geometric parameters using a two-dimensional wave-tank model has been performed. Results from these experiments have shown that the 'water column' has an effect on the paddle dynamics and OWSC performance, with the OWSC having a higher power capture than both a shoreline oscillating water column (OWC) and Pendulor in shallow water. The potential for the OWSC in the shoreline and near-shore regions is also discussed, with implications for construction costs and the price for electricity generated by the OWSC. Potential control strategies for the OWSC are also discussed, together with their likely effect on operation and performance.

Correlation of Pc5 wave power inside and outside themagnetosphere during high speed streams

Abstract: . We show a clear correlation between the ULF wave power (Pc5 range) inside and outside the Earth's magnetosphere during high speed streams in 1995. We trace fluctuations beginning 200RE upstream using Wind data, to fluctuations just upstream from Earth's bow shock and in the magnetosheath using Geotail data and compare to pulsations on the ground at the Kilpisjarvi ground station. With our 5-month data set we draw the following conclusions. ULF fluctuations in the Pc5 range are found in high speed streams; they are non-Alfvenic at the leading edge and Alfvenic in the central region. Compressional and Alfvenic fluctuations are modulated at the bow shock, some features of the waveforms are preserved in the magnetosheath, but overall turbulence and wave power is enhanced by about a factor of 10. Parallel (compressional) and perpendicular (transverse) power are at comparable levels in the solar wind and magnetosheath, both in the compression region and in the central region of high speed streams. Both the total parallel and perpendicular Pc5 power in the solar wind (and to a lesser extent in the magnetosheath) correlate well with the total Pc5 power of the ground-based H-component magnetic field. ULF fluctuations in the magnetosheath during high speed streams are common at frequencies from 1–4mHz and can coincide with the cavity eigenfrequencies of 1.3, 1.9, 2.6, and 3.4mHz, though other discrete frequencies are also often seen. Key words. Interplanetary physics (MHD waves and turbulence) – Magnetospheric physics (solar wind-magnetosphere interactions; MHD waves and instabilities)

Wave power station

Abstract: A wave power plant arranged to be placed on or in the sea or a lake in order to produce energy, comprising a fixed or floating structure and at least one floating body (1) that moves vertically relative to the floating structure and is connected to the structure via energy transmission devices (11). The floating body (1) is designed to be held in a fixed position during part of the wave induced motion of the body (1), thus to increase the recovery of energy from the waves. A method is also disclosed, in which the body (1) is held in a fixed position during part of the time it takes for a wave crest or trough to pass the body (1).

Wave power assembly with an electromagnetic dampning means

Abstract: A wave power assembly comprising a hull and a linear electric generator. The rotor is connected to the hull and the stator is arranged to be anchored at a sea/lake bottom. The generator is provided with an electromagnetic damping means in order to keep the pulsations of the axial force exerted by the stator on the rotor at a relatively low level, which damping means comprises geometric arrangement adapted herefor of at least some one of the stator winding, the stator slots and the rotor magnets. The invention also relates to a wave power plant built up from wave power assemblies according to the invention. Furthermore, the invention relates to a use of the wave power assembly and a method for generation of electric energy.

Wave power assembly

Abstract: The invention relates to a wave power assembly having a hull and a linear electric generator. The rotor (7) is, by means of connection means (4), connected to the hull so that lifting force is transferred from the hull to the rotor (7). Spring means (11b) exerts a force on the rotor (7) that is counter-directed the lifting force. According to the invention, the spring means (11b) is arranged to, at a motion amplitude corresponding to 50 % of the maximum length of stroke of the rotor (7), exert a force, the size of which varies by a factor of 2,5 as a maximum. The invention also relates to a wave power plant built up from wave power assemblies according to the invention. Furthermore, the invention relates to a use of the wave power assembly and a method for the generation of electric energy.

Numerical Performance Investigation of an Array of Heaving Wave Power Converters in front of a Vertical Breakwater

Abstract: The present paper is dealing with the numerical prediction of the performance characteristics of an array of five wave energy heaving converters placed in front of a reflecting vertical breakwater. At a first stage, the appropriate mechanical system modeling is presented. Detailed insight into the system’s kinematical and power production characteristics is given. In the second part, the analytical method used for the evaluation of the hydrodynamic characteristics of the cylindrical floats moving in front of the breakwater is outlined, supplemented with representative numerical results concerning the hydrodynamic parameters in frequency and in time domain. Hydrodynamic interactions among the floats and the adjacent breakwater are exactly taken into account using the method of images. The third part of the paper is devoted to the numerical integration algorithm for solving the coupled non–liner equations of motion taking into account both linear and non-linear couplings with the power take-off mechanism.

Discharge lamp lighting apparatus

Abstract: The present invention relates to a discharge lamp lighting apparatus in which overshoot occurring when the polarity of AC rectangular wave voltage/current is inverted is suppressed. An inverter converts DC power supplied by a converter to AC rectangular wave power and outputs the AC rectangular wave power. A power calculation unit generates a power detection signal based upon a voltage detection signal and a current detection signal detected on the output side of the converter. A control target value setting unit outputs an output power command value to be used to control the DC power so as to achieve a target value. A correction signal generation unit outputs a correction signal to be used to correct the output power command value in conformance to the power detection signal in synchronization with a polarity inversion of the AC rectangular wave power. A converter control signal generation unit outputs a signal corresponding to the error of the power detection signal relative to the output power command value. A pulse width control unit implements pulse width control on the converter based upon the signal provided by the converter control signal generation unit.

Performance of Wave Power Generating System Installed In Breakwater At Sakata Port In Japan

Abstract: The wave power generating system using the Wells turbine is installed in the breakwater in Sakata port, Japan, and consists of the air chamber, turbine, generator and safety devices. The purposes of this paper are to reveal the characteristics of each component in this system with the experimental data in the real sea, and to evaluate the accuracy of numerical models used in the simulation. The performance of Wells turbine is examined in detail for the unsteady and full-scale condition, comparing the data of the 1/4 scale model with the steady full-scale one. As for the motion of water in the air chamber, the eigenfunction expansion method is introduced, and the wave height measured 275m away from the chamber is employed for the input of the simulation. It is found that the performance of the system for the wave can be evaluated accurately with the steady-characteristics of the turbine, in the condition that the stall does not happen on the rotor. The angle of attack for the stall depends on the wave characteristics such as the magnitude of unsteadiness, requiring many trials to get the stall angle used by the calculations. The error of the simulation for the total system is finally predicted to be less than 20% when the wave comes within the region of about 20 degree deviation angle.

Energy budget of Alfven wave interactions with the auroral acceleration region

Abstract: [1] We consider the interaction of Alfven waves with the auroral acceleration region (AAR), which is characterized by a mirror resistance and a related electric potential drop that supports a field-aligned upward current and the acceleration of electrons. An Alfven wave incident on the AAR from the magnetosphere partially reflects back and partially penetrates into the AAR. An analytical treatment of the interaction of Alfven waves with the combined magnetosphere-AAR-topside ionosphere-E layer system immersed into a converging dipole-like magnetic field has been made within the “thin” AAR approximation. The rate of wave reflection/transmission is estimated to be critically dependent on the wave transverse scale. Incident Alfven waves with spatial scales about the Alfven damping scale λA are absorbed most effectively in the AAR. Magnetospheric Alfven waves penetrating into the AAR can produce oscillatory variations of the field-aligned potential drop and field-aligned electron acceleration. Modeling the spatial spectrum of an Alfven burst by a power-law dependence ∝ k−p in the interval between low and high cutoff wave numbers indicates that the estimated rate of total wave power absorbed by the AAR is significant, up to 30–50% depending on p, when the ionospheric projection of the low cutoff wave number is on the order of the scale λA.

Wind and Wave Power Potential

Abstract: Renewable energy is accepted as a key source for the future, not only for Turkey, but also for the world. This study investigates the potential for wind and wave power around the world and in Turkey, and provides an overview of the historical development of both energy resources. Turkey has a considerably high level of renewable energy resources that can be a part of the total energy network in the country. Wind energy has received a lot of attention lately in Turkey as one of the most promising and economically feasible technologies for clean power generation, while the number of studies conducted on wave energy is relatively lower. Based on the values obtained from the latest Turkey Wind Atlas in 2002, Turkey's total theoretically available potential for wind power is found to be about 88,000 MW/yr. Besides this, Turkey's wave power potential is estimated to be around 18,500 MW/yr, with an average wave energy capacity of 140 billion kWh annually. These figures indicate that Turkey has considerable potential for generating electricity from wind and wave power. To date, 3 wind power plants were installed with a total capacity of 18.9 MW, while there is not any wave energy plants installed in the country as of yet. Taking into account the present applications, it may be concluded that wind energy in Turkey is a promising alternative. As the public recognizes the projects, the progress will continue.

Wave Dragon: wave power plant using low-head turbines

Abstract: The paper describes the wave energy converter Wave Dragon placed in a real sea environment. The energy converter in question is the 237-tonne Wave Dragon Nissum Bredning Prototype. Wave Dragon is an energy converter of the overtopping type, using a set of low-head Kaplan turbines as power take o system. A description of turbine performance in the salt sea water environment is given.

Simulated Response of a Linear Generator Wave Energy Converter

Abstract: Electric energy conversion is an important issue in today's society as our daily lives largely depend on the supplies of energy. Two energy sources are studied for conversion in the present thesis, ocean waves and hydropower. The work focuses on the generator and the transmission of its output to the electric grid.Different approaches have been used, over the years, to convert the energy in ocean waves, and the method presently used is based on a point absorber (buoy) directly coupled to a linear generator on the seabed. A varying alternating voltage is induced with such configuration, where both the amplitude and the frequency changes continuously. The target is to connect several units in a farm, and thereby decrease the fluctuations in power production. This is shown to be possible to accomplish with a rectifier connected to each generator. Transmission systems can be designed with converters and transformers to connect the farm to the electric grid onshore. Several aspects of the concept are considered as well as interconnection issues. Analytical calculations verified by finite element simulations and measured data are used to model the behaviour of a linear generator. A series expanded expression for the ideal no-load flux and EMF (electromotive force) is derived, which can be developed into an analytical transmission design tool.Hydropower has been used for more than a century. Today many of the stations from the mid 1900's are up for refurbishment. Studies with finite element calculations show that a higher electric efficiency can be obtained with a high voltage cable wound generator.

Analysis of Wave Energy Density for Korean Coastal Sea Area Based on Long-Term Simulated Wave Data

Abstract: Wave energy distribution along the Korean coastal sea area was analysed based on the calculated wave data at KORDI. The wave data for the analysis is for the last 24 years (1979∼2002) and the model is HYPA and WAM using known wind field. The wave energy or wave power was evaluated based on the linear wave theory with a simple wave period assumption. The results shed some idea on the amount of usable wave energy and the sites of higher efficiency. It is fair to say that 3kw/m wave energy is easily observable and 10kw/m is frequently available depending on the season and location. The south west region of Jeju island is believed to have the highest overall wave energy density.

Wave-PV hybrid generation system carried in the offshore floating type wave power device "Mighty Whale"

Abstract: Japan Agency for Marine-Earth Science and Technology (JAMSTEC) has been engaged in research and development of ocean-wave energy extraction technology for many years now. In particular, work began in 1987 an offshore floating type wave power device called "Mighty Whale". The open sea tests were started on the 10th of September 1998. Tests were conducted until March 2002. For converting renewable energy into electricity, it is not only important to raise energy conversion efficiency, but also to flat-and-smooth of generating electricity considering demand-and-supply balance and system cooperation. Although there are accumulation of electricity and a proposal of storing energy with a flywheel etc., as this measure, equipment different from power generation is needed, and it becomes the factor which raises cost. Generally, when it is fine, a wave is small, and when a wave is high, it is bad weather. For this reason, it is thought that photovoltaics and wave power generation can complement each other fault, and can perform flat-and-smoothization of the amount of power generation. This paper describes verification of the possibility of hybridizing of solar and wave energy and application to the system from an experiment of the combined cycle power generation system of the photovoltaics and wave power generation which were performed with the offshore wave power device "Mighty Whale"

Wave Energy Distribution at Jeju Sea and Investigation of Optimal Sites for Wave Power Generation

Abstract: Wave power distribution is investigated to determine the optimal sites for wave power generation at Jeju sea which has the highest wave energy density in the Korean coastal waters. The spatial and seasonal variation of wave power per unit length is calculated in the Jeju sea area based on the monthly mean wave data from 1979 to 2002 which is produced by the SWAN wave model simulation in prior research. The selected favorable locations for wave power generation are compared in terms of magnitude of wave energy density and distribution characteristics of wave parameters. The results suggest that Chagui-Do is the most optimal site for wave power generation in the Jeju sea. The seasonal distribution of wave energy density reveals that the highest wave energy density occurs in the northwest sea in the winter and it is dominated by wind waves, while the second highest one happens at south sea in the summer and it is dominated by a swell sea. The annual average of wave energy density shows that it gradually increases from east to west of the Jeju sea. At Chagui-Do, the energy density of the sea swell sea is relatively uniform while the energy density of the wind waves is variable and strong in the winter.

Wave power assembly provided with an electromagnetic dampning means

Abstract: The invention relates to a wave power assembly comprising a hull and a linear electric generator. The rotor is connected to the hull and the stator (6a) is arranged to be anchored at a sea/lake bottom. According to the invention, the generator is provided with an electromagnetic damping means in order to keep the pulsations of the axial force exerted by the stator (6a) on the rotor at a relatively low level, which damping means (12) comprises geometric arrangement adapted herefor of at least some one of the stator winding (12), the stator slots (13) and the rotor magnets. The invention also relates to a wave power plant built up from wave power assemblies according to the invention. Furthermore, the invention relates to a use of the wave power assembly and a method for generation of electric energy.

Apparatus for converting of water surface waves energy into mechanical energy

Abstract: The invention related to wave power engineering in general and, more particularly, to apparatuses for converting energy from water surfaces waves, preferably that from sea and ocean waves, to useful mechanical energy, which can be either used directly or converted to another type of energy, for instance, to electric energy. The apparatus has a substantially horizontal axis of rotation and comprises a plurality of tanks, which are connected to each other, arranged uniformly in series in a cyclic manner, substantially symmetrically about their axis of rotation and at a some distance from the axis of rotation and form an one-piece construction, which comprises at least one full turn of tanks. Each tank is confined by a casing, which has a leading section relative to the direction of apparatus rotation, a trailing section relative to the direction of apparatus rotation, and a middle section located between said leading section and said trailing section the trailing section of each casing comprising an inlet, through which the internal cavity of the tank communicates the environment. The leading section of the tank casing is provided with a valve, which allows fluid flow in the direction from the outside inside the tank only and prevents flowing of fluid from the tank outwards. The apparatuses will rotate at any wave height, whatever a tank height is, and the parameters of plants such as the number of apparatuses, the dimensions and shape of their elements will be chosen to meet the requirements for energy efficiency of a given plant. The plant would ensure safe operation at any wave height.

Microwave power supply system and travelling-wave power control method of microwave power supply system

Abstract: PROBLEM TO BE SOLVED: To provide a microwave power supply system and a travelling-wave power control method of the microwave power supply system by propagating a load-side supply power of a given value further toward the load side than an input end 3a of a manual matching unit 3, by keeping the load-side supply power value PL at a given value through an incremental compensation of a travelling-wave power value PF by the value by which a reflective wave power value PR is increased and the load-side supply power value PL is decreased, without augmenting a processing time and without augmenting an adjustment man-hour SOLUTION: With the microwave power supply system and its travelling-wave power control method, an output power setting signal Vst and a reflective wave power value signal Vpr corresponding in size to the reflective wave power value PR are added without changing the movable position of the impedance element from an initial operation state even at processing after the initial operation state of the system, and a magnetron supply power PM making an anode current Ia of the magnetron change in accordance with the above added signals is supplied to the magnetron to output the travelling wave power PF from the output end of a microwave power source 1 COPYRIGHT: (C)2004,JPO

Pendulum type wave power generator

Abstract: PROBLEM TO BE SOLVED: To improve power generation efficiency by equalizing intermittent wave power to be used for power generation, to reduce a construction cost compared with a conventional wave breaker type wave power generator, and to allow power generation using wind power and the wave power as natural energy by additionally providing a wind mill. SOLUTION: A plurality of water chambers 2, 2 are formed in a circumferential direction, in such a manner that a plurality of partition walls 3 stand to be circumferentially spaced from each other on a foundation mount 1 formed on the sea bottom B, and substrates 4 as closing walls stand at the rear of the water chambers to form openings 2A in front of the water chambers. Pendulum plates 11 are connected to and supported by a hydraulic pump 13 such as a swing type vane pump disposed on the partition walls, so that the pendulum plates are axially supported by the water chambers 2 to be capable of swinging. A generator 16 is driven by rotating a hydraulic motor 14 disposed in a machine room 4C of the base body 4 by working oil from the hydraulic pump 13. COPYRIGHT: (C)2004,JPO