Showing papers on "Wave power published in 1996"

Performance of a High-Solidity Wells Turbine for an OWC Wave Power Plant

Abstract: The paper describes an experimental investigation, and presents the results of the aerodynamic performance of a high-solidity Wells turbine for a wave power plant. A monoplane turbine of 0.6 m rotor diameter with guide vanes was built and tested. The tests were conducted in unidirectional steady airflow. Measurements taken include flow rate, pressure drop, torque, and rotational speed, as well as velocity and pressure distributions. Experimental results show that the presence of guide vanes can provide a remarkable increase in turbine efficiency.

An Atlas of the Wave-Energy Resource in Europe

Abstract: This paper presents an Atlas of the European offshore wave energy resource that is being developed within the scope of an European project. It will be mainly based on wave estimates produced by the numerical wind-wave model WAM that is in routine operation at the European Centre for Medium-Range Weather Forecasts, Reading, UK. This model was chosen after a preliminary verification of two models again buoy data for a one-year period. Wave measurements will be used for the Norwegian Sea and the North Sea. The Atlas will be produced as a user-friendly software package for MS-DOS microcomputers permitting fast retrieval of information as well as saving and printing of statistics and maps. The Atlas will include annual and seasonal statistics of significant wave height, mean and peak period, mean direction and wave power levels (global values as well as directional distributions). These data will be both presented as tables, graphs and as geographic maps.

Optimum Control of a Floating Wave-Energy Converter With Restricted Amplitude

Abstract: In this paper, the use of optimal control techniques for improving the energy absorption by a wave-energy converter (WEC) is investigated. A mathematical model is developed for a floating body, which is exposed to an irregular incident wave, and is moving relative to a fixed reference. This model includes a control force from the power take-off and control machinery, and a friction force which restricts the oscillation amplitude. This force models end-stop devices, which are necessary to protect the machinery. An optimal control strategy is determined, based on variations of a Lagrange functional. This gives a set of adjoint equations in addition to the state equations, as a necessary condition for optimum. An algorithm is given for solving the problem numerically by iteration, based on a gradient method. It is shown that the optimal motion in a sinusoidal wave is not sinusoidal when the excursion is constrained. Instead, the motion should be stopped in certain intervals. In irregular waves the constrained solution is close to the unconstrained solution when the excursion is small. Moreover, the timings of the extrema and of the zero crossings agree fairly well. When the excursion is constrained, the mean output power is reduced compared tomore » the unconstrained case, but the ratio between the output energy and the total energy passing through the machinery is increased. This means that the conversion efficiency of the machinery is less critical.« less

Sir measuring device

Abstract: PROBLEM TO BE SOLVED: To measure and SIR(selective information retrieval) with high accuracy with a simple structure and operation. SOLUTION: An SIR measuring method measures an S/N ratio which is a ratio of expected wave power to noise power or an S/I ratio which is a ratio of expected wave power to interference wave power. In such cases, a signal point changing part 51 takes an absolute value of an I component (common mode component) and a Q component (rectangular component) of a receiving signal, converts the receiving signal into a signal of the 1st quadrant of an I-Q rectangular coordinate system and calculates a 1st mean power (expected wave power) S by squaring a mean value of the converted signal. A receiving power operating part 54 operates the mean value of a squared receiving signal, calculates the mean value of receiving power and calculates noise power or interference wave power I by subtracting the power S from the receiving power. An SIR operating part 57 operates an S/N ratio or an S/I ratio from the power S and noise power or the power I and outputs it.

Theory of wave propagation along waveguide filled with plasma in finite magnetic field

Abstract: Rigorous analytical theory of wave propagation along a cylindrical waveguide filled with plasmas in a dielectric tube immersed in finite magnetic field is presented.The field components' expressions,eigenvalues,dispersion equations and complex wave power transmission equations have been obtained rigorously and discussed in detail.It is shown analytically that there is no disruption of the wave propagationin the ECR (ω=ωa) case,although the electrical permittivities approach to infinite in the case,and it hasbeen found that a real resonance takes place in this case while ω=(ωa2+ωpc2)1/2,in which the wave propagationof any mode is broken.The effective collisions are taken into consideration in the theory.Based on the above theory,the analytical theory of corrugated plasma waveguide immersed in finite axial magnetic field is also presented.The Floquet's expansion of field components,the dispersion equations,and the coupling coefficients of the corrugated plasma waveguide have been derived rigorously and discussed in detail.

A simple theory 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 simple 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 sinusoidallyoscillating flow condition. The estimated results reveal a behavior of the actual characteristics curve of the turbine. Possibility of further increase in efficiency was discussed from a viewpoint of specific speed and specific diameter.

Wave power device using buoys anchored to the sea bed

Abstract: Buoys 500 are rotatably mounted on lattice frame 100, and tied by cables 220 to anchors 210. Their rising and falling movements are converted to rotating forces by unit 600, compressing fluid in unit 700 and pumping it through pipe 910 to a turbine. The turbine drives a generator to produce electricity; both units are mounted on auxiliary frame 160 in power generation sector S1. A pressure relief valve may be fitted (fig. 17), to avoid damage through overloading. A surge tank may be used to avoid pressure pulses. The spiral motion of the fluid in this tank due to the rotation of the earth may be corrected by the direction of introduction of this fluid. Tension control means (figs. 7C, 7D) may be applied to the anchor cables. Compressed air may be used to assist frame buoyancy.

Pendulum type wave power generator to be installed on wave dissipation structure

Abstract: PURPOSE: To provide a pendulum type wave power generator to be installed on a wave dissipation structure of pile fixation type which is installed offshore so that pendulum plates are swung offshore where the wave energy is comparatively high, with which the share of the wave dissipation structure in the equipment cost can be lessened. CONSTITUTION: A wave dissipation structure 1 is composed of wave dissipation blocks 2-1, 2-2 where vertical wave dissipation plates 10 having a certain length provided at the front face, vertical wave dissipation plates at the rear face, pillars 60, and beams are formed in a single piece structure and a water-permeable skeleton structure 50 which supports them in the lower part and is equipped with inserting holes 52 for piles to be fixed to the ground. The plates 10 at the front face are located as confronting the outside of a bay in the longitudinal or transverse arrangement at a certain spacing, wherein the gaps between them serve as wave dissipation holes 12, and a wave receptacle hole 40 is installed in the direction perpendicular to the wave faces. The other plates at the rear face are arranged confronting the inside of the bay in such an arrangement as parallel with the front face wave dissipation plates 10 and are provided with wave dissipation holes and wave outlets. Pendulum plates 90 are installed swingably in positions opposing to the wave receptacles 40 in the plates 10, and a power generator is installed on this wave dissipation structure.

Optimal control of wave energy devices with various power-take-off mechanisms

Abstract: The aims of this research are to develop and test methods for analyzing and computing optimal control strategies for maximizing the useful power generated from wave energy converters incorporating realistic power-take-off and control mechanisms. Previously, strategies for maximizing energy absorbed by wave devices have been investigated, but these studies have assumed an ideal conversion rate using perfectly efficient turbomachinery with no constraints imposed by the generator capacity. In this paper various turbine characteristics and control mechanisms incorporating nonlinear losses are modelled, the qualitative properties of the optimal control strategy for maximizing average power delivered at the turbine shaft are analyzed, computational techniques for determining numerical solutions to the optimal control problem are established and the results are tested on a fully developed hydrodynamic model of a wave energy device.