GB2545406A

GB2545406A - A wave energy converter

Info

Publication number: GB2545406A
Application number: GB1521779.7A
Authority: GB
Inventors: James Adkins Nicholas
Original assignee: Individual
Current assignee: Individual
Priority date: 2015-12-10
Filing date: 2015-12-10
Publication date: 2017-06-21
Also published as: GB201521779D0

Abstract

A self-contained wave energy converter (WEC) comprises a wave-operated member (WOM) 1 which supports a reaction member (REM) 2 by energy conversion devices 5. There is therefore no need for a pivoted connection, and energy can be converted from forces (acceleration) in any direction. The device may be fully enclosed in which all moving parts are protected and may be maintained at sea. The energy conversion devices may be hydraulic cylinders 5, powering a hydraulic turbine.

Description

A Wave Energy Converter Field of the Invention

This invention relates to Wave Energy Conversion by means of a self-contained Wave Energy Converter (WEC) comprising a wave-operated member (WOM) and a reaction member (REM) the device being not reliant on connection to shore or seabed for its operation.

Background

Decades of research into wave energy conversion and the application of much ingenuity has yielded valuable data, knowledge, proven components and experience but has not resulted in the extraction of useful energy on a scale anywhere near the potential of the resource.

Published material shows that problems common to many proposed wave energy converters are mechanical complexity and the difficulty of maintenance in the harsh marine environment in which the devices must operate. Mechanical complexity also obscures the simplicity of the underlying physical principles that are necessarily common to all WOM / REM Wave Energy Converters.

Design for seaworthiness should be informed by the existing maritime industry with its wealth of knowledge, experience and expertise. As the design, construction and operation of large wave energy extraction devices will be undertaken by the existing maritime industry it is clearly advantageous if proposals are formulated with existing maritime practices in mind.

My Patent Application GB1311990.4 describes a Wave Energy Extraction Device (WEED), the more generally accepted term is Wave Energy Converter (WEC) and this term will be used throughout this present application. GB1311990.4 describes various aspects of wave energy conversion and identifies several important design principles of WOM/REM Wave Energy Conversion Devices: 1) that the WOM must be of a form and size that under the action of waves there are two parts that are supported in the water periodically at different heights. In practice this will mean that the WOM length, measured in the direction of wave propagation, might be from a few metres up to two thirds of the wavelength of a common oceanic wave or approximately 150 metres, 2) that the WOM should be of a form that enables it to contact a broad wave front when operatively orientated, 3) that the REM should constitute as great a proportion of the total mass of the Wave Energy Conversion device as is practicable, 4) that the mass of the REM should be concentrated at its ends, that is at the farthest practicable distance from the REM’s centre of gravity so that the REM is able to possess the maximum angular momentum or kinetic energy for a given total mass of the REM which in turn means that a Wave Energy Conversion device (WEC) of a given displacement can convert a greater amount of wave energy.

The principle that the REM be pivoted at its centres of gravity has been rendered unnecessary in the light of more recent development and testing and is not included in the present application.

To incorporate these preferred design principles the present invention proposes a Wave Energy Conversion device (WEC) comprising at least one Wave Operated member (WOM) being a buoyant body of sufficient buoyancy to support at least one Reaction Mass (REM) said REM being supported on the WOM by a plurality of Energy Conversion Devices (ECDs) operatively connected to the WOM and REM so that the mass of the REM and acceleration due to gravity produce pressure in the ECDs and that said pressure will be altered by the action of waves upon the WOM so that individual ECDs will contain different pressures and said different pressures may be conducted through at least one manifold to at least one motor, a means of regulating the amount of extracted energy from said energy extraction devise, a means of storing or using or transmitting the extracted energy.

Brief description of drawings

Fig 1 shows a cutaway view of a Wave Energy Conversion device (WEC) according to the present invention; a Wave Operated Member WOM 1 being a buoyant vessel, a Reaction Member REM 2, supported by Energy Conversion Devices (ECDs) 5 which are in turn supported on the WOM by Articulated Supports 4.

Fig 2 shows the Energy Conversion Devices (ECDs) 5 connected by connection means 9 to a manifold 7 in which differential pressures in the Energy Conversion Devices 5 are directed to motors 12 and electrical generators 11 under the direction of control means 8.

Fig 3 a WEC in which the REM is fully enclosed by WOM 1 and the Cover 6.

Fig 4 Shows a WOM 1 comprising two buoyant vessels joined by substantially rigid members 3.

Fig 5 shows three WOMs 1 connected by Members 3 and Articulated Joints 14

Detailed description of the invention A first embodiment of the present invention will be described with reference to Figures 1, 2 and 3. Figure 1 shows the Wave Operated Member (WOM 1) and the Reaction Member (REM 2) in cutaway view and Figure 2 shows the Energy Conversion Devises (ECDs) 5 and various equipment to be housed in the REM 2. For clarity this various equipment is not shown in Figure 1. The ECDs are hydraulic pumps. Figure 3 shows WOM 1 and COVER 6 forming a watertight enclosure such that no moving parts need be exposed to the operating environment.

Fixed to WOM 1 are Articulated Supports 4 which support the ECDs. The Articulated Supports might be so constructed as to allow the ECDs to be rigidly fixed to the REM and still allow relative movement in all axes between REM and WOM.

The ECDs are hydraulically connected via Connection Means 9 to a Manifold 7. Manifold 7 contains hydraulic valves which are controlled by Control Means 8. Hydraulic valves also control flow to the Motors 12 and Accumulator 13.

The Motors 12 in turn drive Electrical Generators 11 and the electrical energy taken from the WEC by cables to a terminal or hub alternatively energy might be stored on the WEC for later transhipment. Some possible energy storage means include; batteries, battery electrolyte, hydrogen from electrolysis, liquefied air.

In operation the REM is supported by the ECDs. In still water the total pressure on the ECDs will be constant and determined by the mass of the REM and acceleration due to gravity.

When the WOM is subjected to wave conditions accelerations due to the buoyancy of the WOM are passed to the REM via the ECDs and these accelerations result in pressure differentials between ECDs.

For example a wave with a direction of propagation along the long axis of the WOM will alternately raise and lower each end of the WOM giving rise to differential pressures in the relevant ECDs. Wave action inducing pitch, roll and yaw in the WOM will give rise to differential pressures in the ECDs.

Wave action inducing heave in the WOM will not give rise to differential pressures in the ECDs however the Accumulator 13 will be able to store the pressure produced by a rising wave and thus provide a pressure which is higher than that of the ECDs during the falling wave. The differential pressures are conducted by Control Means 8 and Manifold 7 to the hydraulic Motors 12

Since all forces are transferred to the REM via the ECDs it is possible for the WEC to convert energy from complex waves. Control Means 8 might optimally direct the hydraulic flow by monitoring instantaneous pressure differentials and, with other data, anticipate differentials. The differential pressures are conducted by Control Means 8 and Manifold 7 to the hydraulic Motors.

The overall function of the Control Means is to optimise the extraction of wave energy by directing the hydraulic flow and by controlling the electrical load on the generators. The overall position of the REM within the WOM is also controlled.

The WEC might connected to the sea bed or shore by a tether for the purpose of station keeping and connected by electrical cables to a terminal or hub. It is also possible for the WEC to operate un-tethered and provided with propulsion means for positioning and also provided with energy storage means. A WEC of sufficient size will allow maintenance at sea, the interior of die REM providing a semi-stabilised environment. A second embodiment of the present invention is shown in Figure 4 which shows two WOM’s 1 joined by substantially Rigid Members 3. This embodiment allows the WOM’s to be spaced apart so that one WOM is subjected to the maximum rate of rise of a wave while at the same time the other WOM is being subjected to the maximum rate of fall, the resultant ECD pressure differential producing hydraulic flow in pipes inside Rigid Members 3. A third embodiment of the present invention is shown in Figure 5 which shows three WOM’s connected by Rigid Members 3 and Articulated Joints 14. Any number of WOM’s might be joined in this way with the advantage that only a single tether and a single electrical connection means are required. A disadvantage is that the Articulated Joints 14 are exposed to the operating environment.

The present invention is not limited to the foregoing embodiments.

Claims

1. A Wave Energy Converter (WEC) comprising at least one Wave Operated member (WOM) being a buoyant body of sufficient buoyancy to support at least one Reaction Mass (REM) said REM being supported on said WOM by a plurality of Energy Conversion Devices (ECDs) operatively connected to the WOM and REM so that the mass of the REM and acceleration due to gravity produce pressure in the ECDs and that said pressure will be altered by the action of waves upon the WOM so that individual ECDs will contain different pressures and said different pressures may be conducted to at least one motor.

2. A Wave Energy Conversion device according to claiml in which the energy conversion device is a hydraulic pump providing hydraulic energy.

3. A Wave Energy Conversion device according to claiml in which the motion of the reaction member relative to the wave operated member is controlled by the energy conversion device.

4. A Wave Energy Conversion device according to claiml in which an accumulator stores pressure.

5. A Wave Energy Conversion device according to claiml in which the energy conversion device is a heat pump.

6. A Wave Energy Conversion device according to claiml which is tethered for the purpose of position keeping.

7. A Wave Energy Conversion device according to claiml which is tethered for the purpose of energy transmission.