Wave energy converter

Details Wave energy converter Wave energy converter

1998-10-29

2001-05-08

Lopez, F. Daniel (Department: 3745)

Power plants

Motor having a buoyant working member

Working member actuated by the rise and fall of a surface of...

C060S502000

Reexamination Certificate

active

06226989

ABSTRACT:

This invention relates to a wave energy converter.
Wave energy converters of this kind, which are sometimes referred to as point absorbers or heaving-buoy wave energy converters, are known from, for example, U.S. Pat. No. 4,773,221. The operation of this particular converter is based on relative motion between, on the one hand, a buoyant body and a so-called acceleration tube attached to and depending from the buoyant body, and, on the other hand, a reciprocable working piston in the acceleration tube; this relative motion is caused by the waves of the sea in which the converter operates.
In a wave energy converter of this kind, the working piston and other masses coupled to it form an inertial system which has no positive coupling to the buoyant body and the acceleration tube in the vertical direction, that is, in the direction of the axis of the acceleration tube.
Naturally, the working piston itself and the associated piston rod have a certain mass, but the mass which moves with the piston is determined primarily by a column of water which moves with the piston.
The wave energy converter known from U.S. Pat. No. 4,773,221 includes a relief system which limits the stroke of the working piston to a predetermined operating range within the acceleration tube. If during its movement in either direction the working piston moves out of the operating range, e.g. as a consequence of an excessive heaving of the buoy, the relief system limits continued movement away from the operating range. More particularly, the relief system operates by relieving the working piston of the force which causes its movement away from its working range in the acceleration tube, namely by allowing water to pass more or less freely past the working piston. Accordingly, a substantially unrestricted communication is established between the columns of water above and below the working piston and thereby between these columns of water and the water surrounding the acceleration tube.
The limitation of the stroke of the working piston eliminates or reduces the danger of excessive loads being applied to the piston rod resulting from heavy sea.
However, the returning of the working piston into the working cylinder, that is, into the normal operating range, when the direction of movement of the buoyant body and the acceleration tube is reversed, takes place in an uncontrolled manner and may be considerably delayed. As a consequence, the efficiency of the wave energy converter is reduced.
A primary object of the invention is to solve this problem and provide a wave energy converter in which the working piston is rapidly and reliably returned into the working cylinder whenever it is moved out of its normal working range.
As will be explained in more detail below, if in the wave energy converter according to the invention the working piston is driven out of the working cylinder, an impulse directed towards the working cylinder will be applied to the working piston by means of an energy accumulator previously charged by the working piston. The triggering of the impulse may be accomplished by means of a position sensor which actuates the energy accumulator in response to movement of the working piston out of the working cylinder.
The energy accumulator may be a hydraulic or hydropneumatic accumulator which is charged by a pump driven by the working piston. Other types of energy accumulators may also be used, however, such as resilient devices which are tensioned and relaxed in push-pull fashion by the working piston during its reciprocating movements.


REFERENCES:
patent: 4076463 (1978-02-01), Welczer
patent: 4277690 (1981-07-01), Noren
patent: 4773221 (1988-09-01), Noren
patent: 3938 667 A1 (1991-05-01), None

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