Wave Power Conversion Research Articles

Characteristics of Pneumatic Wave Power Conversion System with Water Valve Rectifier

Energy conversion characteristics of a new wave power conversion device are discussed. In this system, water valves, not mechanically operated, are combined with air chambers. The advantage of this...

Wave power conversion by point absorbers: A Norwegian project

SYNOPSIS This paper describes a spherical buoy, which can perform heaving oscillation relative to a strut joined to an anchor on the sea bed. The buoy is supplied with latching means for optimum phase control and with an air turbine for power take-off. The electrical generator is rated at 0.4 MW. An estimate is given for the cost of a 200 MW power plant and for its annual energy production if placed off the west coast of Norway. The estimated electricity cost is approximately 4 p/kWh. At the present stage of the research, it is consequently not competitive with hydroelectric power plants in Norway. However. There are several options for cost reduction of a powerbuoy plant.

An experimental study of wave power conversion by a heaving, vertical, circular cylinder in restricted waters

Results of an experimental study of a heaving, vertical, circular cylinder show that there is a relationship between water depth, draft and tank width for which minimum motion damping occurs. In addition, there is a minimum value of added-mass for a depth-diameter relationship. When the cylinder is in a resonant heaving condition at these ‘minimum’ parametric values, the wave energy conversion efficiency of the cylinder is shown to exceed the theoretically predicted maximum deep water value. Finally, for a cylinder spacing (tank width) of one radiant wavelength, the optimum depth value is shown to be four times the draft of the cylinder.

Wave energy conversion by flexible resonant rafts

A long slender floating beam sufficiently flexible to follow the waves, is considered as a wave power converter. Tensioned cables apply a longitudinal compression forces to the beam, encouraging buckling, which enhances the wave-induced vertical oscillations. The oscillations activate pumps incorporated in the structure. The theory of the raft oscillations is presented, together with their radiation effects, leading to curves for the capture width. Exceptionally broad band response is predicted, and confirmed qualitatively by model experiments. The maximum strain in steep waves is calculated and is shown to be acceptable if the cable tension is reduced to zero in storms.

Optimization of Power Absorption From Sea Waves

This article presents a generalized procedure for selecting rationally the design parameters of a simple wave power absorption system. The system utilizes a tethered-symmetrical float which rides the sea waves and transmits the wave energy to a viscously damped load. The optimum load levels corresponding to the different sea states are determined, for several float geometries, in order to maximize the overall efficiency of wave-power conversion. The optimum float dimensions are constrained to guarantee that the float will not leave the wave crest during its upward travel or sink below the wave trough as it goes downward. These constraints, if overlooked, as has been the case so far in the literature, result not only in improper functioning of the system but also in values of the conversion efficiency higher than reality. The developed procedure predicts also, for different float configurations, the limits that, if satisfied, can guarantee that the system would operate at its maximum possible efficiency irrespective of the sea wave conditions. Therefore, the material presented in the study can be extremely useful in designing efficient wave power absorbers which would help in capturing the vast amount of the renewable and nonpolluting sea wave energy.

How to measure and optimize the efficiency of a wave power converter

A method by which one can measure the hydrodynamic efficiency of a wave power converter is discussed. Provided one measures both the horizontal and the vertical wave motion, it is sufficient to have measurements at one point closely in front of the converter and at another point behind it. Good estimates of the efficiency can be obtained without a Fourier analysis of the waves. The method should be useful both for measurements in the laboratory and in the ocean.