Wave energy converter utilizing internal reaction mass and spring

• US 20070126239A1
• Filed: 12/01/2006
• Published: 06/07/2007
• Est. Priority Date: 12/01/2005
• Status: Active Grant

• Current Assignee: David Robert Stewart, James Gerber
• Original Assignee: David Robert Stewart, James Gerber
• Inventors: Stewart, David, Gerber, James
• Granted Patent: US 7,443,046 B2
• Time in Patent Office: Days
• US Class Current: 290/53
• CPC Class Codes: F03B 13/20 wherein both members , i.e. wom and rem are movable relative to the sea bed or shore
• CPC Class Codes: F05B 2250/44 one element moving inside another one, e.g. wave-operated member (wom) moving inside another member (rem)
• CPC Class Codes: F05B 2260/502 involving springs
• CPC Class Codes: Y02E 10/30 Energy from the sea, e.g. using wave energy or salinity gradient

Abstract

A wave energy converter (WEC) includes a shell suitable for being placed within a body of water. The shell contains an internal oscillator comprising a “reaction mass” and a spring mechanism coupled between the reaction mass and the shell. The shell and internal oscillator are constructed such that, when placed in a body of water and in response to waves in the body of water, there is relative motion between the shell and the internal oscillator'"'"'s mass. A power take-off (PTO) device is coupled between the internal oscillator and the shell to convert their relative motion into electric energy. In systems embodying the invention, the spring mechanism is designed such that its displacement or movement is less than the displacement or movement of the reaction mass. The spring mechanism may be any device which enables the reaction mass to undergo a given replacement while its displacement or movement is less than that of the reaction mass. This property enables the size of the WEC to be more readily controlled (e.g., made smaller).

Claims

1. A wave energy converter (WEC) system comprising:

a shell responsive to wave motion in a body of water;

an internal oscillator including a reaction mass and a spring mechanism;

the spring mechanism for coupling the reaction mass to the shell, said internal oscillator mounted within the shell for moving out of phase relative to the shell, when the shell and the internal oscillator are placed in a body of water subject to wave conditions;

a power take-off (PTO) device coupled between the shell and the internal oscillator for converting their relative motion into electrical energy;

wherein the PTO and internal oscillator are located within the shell so as to be generally insulated from the body of water; and

the spring mechanism being coupled to the reaction mass such that the effective linear displacement of the spring mechanism is less than the linear displacement of the reaction mass.

2. A WEC as claimed in claim 1 wherein decreasing the linear displacement of the spring mechanism enables a reduction in the size of the shell.

3. A WEC as claimed in claim 1 wherein the spring mechanism includes a block and tackle pulley system

4. A WEC as claimed in claim 1 wherein the effective stiffness of the spring mechanism is increased so as to enable a reduction in the displacement of the spring

5. A WEC as claimed in claim 1 wherein the spring mechanism includes a hydraulic cylinder coupled to an accumulator.

6. A WEC as claimed in claim 5 wherein the accumulator is gas charged.

7. A WEC as claimed in claim 1 wherein the spring mechanism includes a scissor mechanism.

8. A WEC as claimed in claim 1 wherein the spring mechanism includes a cantilevered beam

10. A WEC as claimed in claim 1 wherein the spring mechanism includes a pneumatic cylinder coupled to an accumulator

11. A WEC as claimed in claim 1 wherein the spring mechanism includes a ball screw coupled to a torsional spring

12. A WEC as claimed in claim 11 wherein the torsional spring is coupled to the ball screw by a gear box

13. A WEC as claimed in claim 1 wherein the PTO device functions as part of the spring mechanism.

14. A WEC as claimed in claim 1 wherein the natural frequency of the internal oscillator may be tuned to approximate the frequency of the waves.

15. A WEC as claimed in claim 1 wherein the reaction mass may include the energy storage elements.

16. A WEC as claimed in claim 1 wherein the reaction mass may include a chamber selectively filled with water.

17. A WEC as claimed in claim 16 wherein the chamber is filled with water following deployment of the WEC in a body of water.

9. A WEC as claimed in claime 8 wherein the spring is attached to the shell at a point that makes the cantilevered beam level in the steady-state equilibrium condition so as to make the spring behave in a linear manner.

18. A wave energy converter (WEC) system comprising:

a shell responsive to wave motion in a body of water;

an internal oscillator including a reaction mass and a spring mechanism for coupling the reaction mass to the shell, said internal oscillator mounted within the shell and designed to move out of phase relative to the shell and wherein the shell and oscillator, being constructed such that, when placed in the body of water and in response to waves in the body of water, there is relative motion between the shell and the internal oscillator;

a power take-off (PTO) device coupled between the shell and the internal oscillator for converting the motion between the shell and the internal oscillator into electrical energy;

wherein the PTO and internal oscillator are located within the shell so as to be generally insulated from the body of water; and

wherein the shell is designed to be submerged and to include a waterproof cavity in which the PTO and the internal oscillator are contained.

19. A WEC as claimed in claim 18 wherein said WEC includes components to regulate the buoyancy ot the WEC so the WEC can remain underwater in a neutrally buoyant state.

20. A wave energy converter (WEC) system comprising:

a shell responsive to wave motion in a body of water;

an internal oscillator including a reaction mass and a spring mechanism for coupling the reaction mass to the shell, said internal oscillator coupled to the shell and designed to move out of phase relative to the shell and wherein the shell and oscillator, being constructed such that, when placed in the body of water and in response to waves in the body of water, there is relative motion between the shell and the internal oscillator;

a power take-off (PTO) device coupled between the shell and the internal oscillator for converting the motion between the shell and the internal oscillator into electrical energy; and

wherein the spring mechanism is formed such that for a given linear displacement of the reaction mass the effective displacement of the spring mechanism is less than that of the reaction mass.

21. A wave energy converter (WEC) system comprising:

a shell responsive to wave motion in a body of water;

the combination of a reaction mass and a spring mechanism coupling the reaction mass to the shell, said combination mounted within the shell and designed to move out of phase relative to the shell and wherein when the shell and the combination are placed in the body of water and in response to waves in the body of water, there is relative motion between the shell and the combination;

a power take-off (PTO) device, located within the shell, coupled between the shell and the reaction mass for converting their relative motion into electrical energy; and

the spring mechanism being coupled to the reaction mass such that the effective displacement of the spring mechanism is less than the linear displacement of the reaction mass.

22. A WEC as claimed in claim 21 wherein the mass of the reaction mass and the force constant of the spring are tuned to give the desired natural frequency of the WEC