# US 11,028,818 B2 · Wave energy conversion of horizontal surge motion

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- Number: US 11,028,818 B2
- Document ID: US11028818B2
- Status: Granted
- Kind: B2
- Application number: 15/965,795
- Filed: 2018-04-27
- Published: 2020-03-12
- Granted: 2021-06-08
- Earliest claimed: 2018-04-27
- Assignees: Oscilla Power Inc.
- Applicants: Oscilla Power, Inc.
- Inventors: Brian J Rosenberg; Timothy R Mundon
- Web page: https://patentgrep.com/patent/US11028818B2

## CPC

- F03B 13/18: where the other member, {i.e. rem} is fixed, at least at one point, with respect to the sea bed or shore
- F03B 13/1885: {and the wom is tied to the rem}
- B63B 22/18: having means to control attitude or position, e.g. reaction surfaces or tether
- F05B 2240/93: on a structure floating on a liquid surface
- Y02E 10/30: Energy from the sea, e.g. using wave energy or salinity gradient
- F03B: MACHINES OR ENGINES FOR LIQUIDS (positive-displacement engines for liquid F03C; machines for liquids and gases F01; positive-displacement machines for liquids F04, rotary fluid gearing of the hydrokinetic type F16H41/00)
- B63B: SHIPS OR OTHER WATERBORNE VESSELS; EQUIPMENT FOR SHIPPING (arrangements of vessel ventilation, heating, cooling, or air-conditioning B63J2/00; floating substructures as supports of dredgers or soil-shifting machines E02F9/06)
- F05B: INDEXING SCHEME RELATING TO WIND, SPRING, WEIGHT, INERTIA OR LIKE MOTORS, TO MACHINES OR ENGINES FOR LIQUIDS COVERED BY SUBCLASSES F03B, F03D AND F03G
- Y02E: REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION

## Abstract

A system converts mechanical wave energy into electrical energy. The system includes a wave energy converter (WEC), which includes a surface float, a reaction structure, a plurality of flexible tethers, and a plurality of drivetrains. Each flexible tether connects the surface float to the reaction structure. Each drivetrain is connected to a corresponding flexible tether. Each flexible tether has a length established to treat the system as an inverse pendulum to utilize a horizontal surge motion of the surface float to present tension at the corresponding drivetrain for production of electrical energy from the horizontal surge motion.

## Claims

### Claim 1

A system for converting mechanical wave energy into electrical energy, the system comprising:
a wave energy converter (WEC) comprising:
a surface float;
a reaction structure;
a plurality of flexible tethers, each flexible tether connecting the surface float to the reaction structure; and
a plurality of drivetrains, wherein each drivetrain is connected to a corresponding flexible tether;
wherein each flexible tether connecting the drivetrain to the reaction structure has a length established to treat the system as an inverse pendulum to utilize a horizontal surge motion of the surface float to present tension at the corresponding drivetrain for production of electrical energy from the horizontal surge motion, and to follow approximately a natural pendulum given by the formula:
T
n
≈
2
⁢
π
⁢
L
g
wherein where L is the length of a tether, and g is the gravitational acceleration, and Tn is the natural period,
wherein the each flexible tether is individually adjustable in length, and wherein at least two flexible tethers can produce different effective moment arms about the surface float center of gravity resulting in a net pitch moment.

### Claim 2 (depends on 1)

The system of claim 1, where the reaction structure rests on or is attached to the sea floor.

### Claim 3 (depends on 1)

The system of claim 1, where the reaction structure is suspended above the sea floor by one or more tethers separate from the plurality of flexible tethers.

### Claim 4 (depends on 1)

The system of claim 1, where the natural period of surge oscillation of the system is different than the natural period for pitch motion of the system.

### Claim 5 (depends on 1)

The system of claim 1, where the natural period of surge oscillation of the system is different than the natural period for heave motion of the system.

### Claim 6 (depends on 1)

The system of claim 1, where the natural period of surge oscillation of the system is similar the natural period for pitch motion to maximize energy capture from waves in a sea-state that has an average energy period conducive to the natural period of surge oscillation and the natural period for pitch motion of the system.

### Claim 7 (depends on 1)

The system of claim 1, where the natural period of surge oscillation of the system is similar the natural period for heave motion so as to maximize energy capture from waves in a sea-state that has an average energy period conducive to the natural period of surge oscillation and the natural period for heave motion of the system.

### Claim 8 (depends on 1)

The system of claim 1, further comprising tether controllers to change the length of at least one of the flexible tethers and, therefore, the period of oscillation in surge motion, based on a real or expected sea state that the system is operating in.

### Claim 9 (depends on 1)

The system of claim 1, further comprising more than one body may be suspended from the surface float using the flexible tethers at different depths below the surface.

### Claim 10 (depends on 1)

The system of claim 1, wherein the drivetrain is located within the surface float.

### Claim 11 (depends on 1)

The system of claim 1, further comprising a second reaction structure.

### Claim 12 (depends on 11)

The system of claims 11, wherein the second reaction structures is at different lengths from the reaction structure.

### Claim 13 (depends on 8)

The system of claim 8, wherein the tether controllers are onboard the surface float.

### Claim 14

A system for converting mechanical wave energy into electrical energy, the system comprising:
a wave energy converter (WEC) comprising:
a surface float;
a reaction structure;
a plurality of flexible tethers, each flexible tether connecting the surface float to the reaction structure; and
a plurality of drivetrains, wherein each drivetrain is connected to a corresponding flexible tether;
wherein each flexible tether connecting the drivetrain to the reaction structure has a length to treat the system as an inverse pendulum to utilize a horizontal surge motion of the surface float to present tension at the corresponding drivetrain for production of electrical energy from the horizontal surge motion, and to follow approximately a natural pendulum given by the formula:
T
n
≈
2
⁢
π
⁢
L
g
wherein where L is the length of a tether, and g is the gravitational acceleration, and Tn is the natural period,
wherein the each flexible tether is individually adjustable in length, and wherein at least two flexible tethers can produce different effective moment arms about the surface float center of gravity resulting in a net pitch moment;
tether controllers to change the length of at least one of the flexible tethers and, therefore, the period of oscillation in surge motion, based on a real or expected sea state in which the system is operating.