WO2012131705A2

WO2012131705A2 - A device for generating electrical energy using ocean waves

Info

Publication number: WO2012131705A2
Application number: PCT/IN2012/000181
Authority: WO
Inventors: Ashutosh Santram VERMA
Original assignee: Verma Ashutosh Santram
Priority date: 2011-03-28
Filing date: 2012-03-15
Publication date: 2012-10-04
Also published as: WO2012131705A3

Abstract

The present invention provides a device for generating electrical energy using ocean waves. The device comprising: a tunnel like structure having two ends; a pair of fixed floats and a pair of articulated floats being attached to the upper end of tunnel like structure; a turbine being accommodated inside the tunnel like structure, the turbine comprises a rotating shaft and a unidirectional rotor; and a direct drive generator being provided at the first end of tunnel like structure and connected to the shaft of turbine. The articulated floats are attached to the tunnel like structure in conjunction with gas springs and the fixed and articulated floats provide driving force to move the tunnel like structure up and down, the up and down movement of the tunnel like structure enables the water column inside it to generate force which results into oscillating motion for driving the unidirectional turbine rotor to rotate the direct drive generator through the shaft and generate electrical energy.

Description

A DEVICE FOR GENERATING ELECTRICAL ENERGY USING OCEAN WAVES

FIELD OF THE INVENTION

Tshe present invention relates to harnessing of ocean wave energy. More particularly it relates to wave energy convertor device to generate electrical energy using ocean wave energy.

PRIOR ART

Traditional sources of energy such as oil, gas, and coal are nonrenewable. They also create pollution by releasing huge quantities of carbon dioxide and other pollutants into the atmosphere. In contrast, ocean waves are a renewable source of energy that contain energy in abundance and doesn't cause pollution. The energy from waves alone could supply the world's electricity needs. The problem is how to harness wave energy efficiently and with minimal environmental, social, and economic impacts.

More than 70% of Earth's surface is covered by oceans which contain two types of energy:

i. mechanical energy from waves and tides and

ii. Thermal energy from solar radiations falling on the ocean surface making them the world's largest solar collectors.

Even though the sun affects all ocean activity, tides are driven primarily by the gravitational pull of the moon, and waves are driven primarily by the winds. As ocean waves are created by the interaction of wind with the surface of the sea, waves have the potential to provide an unlimited source of renewable energy. Waves created by the wind are the most common waves and the waves relevant for most wave energy technology. Wave energy conversion takes advantage of the ocean waves caused primarily by the interaction of winds with the ocean surface. Wave energy is an irregular oscillating low-frequency energy source. They are a powerful source of energy, but are difficult to harness and convert into electricity in large quantities. The energy needs to be converted to a 50/60 Hertz frequency before it can be fed to the electric utility grid.

Ocean wave power is a more promising resource than others for the following reasons:

1. Because waves originate from storms far out in sea and can travel long distances without significant energy loss, power produced from them is much steadier and more predictable, both day to day and season to season. This reduces project risk;

2. Wave energy contains roughly 1000 times the kinetic energy of wind, allowing much smaller and less conspicuous devices to produce the same amount of power in a fraction of the space;

3. Unlike wind and solar power, power from ocean waves continues, to be produced around the clock, whereas wind velocity tends to die in the morning and at night, and solar is only available during the day in areas with relatively little cloud cover;

4. Wave power production is much smoother and more consistent than wind or solar, resulting in higher overall capacity factors;

5. Wave energy varies as the square of wave height, whereas wind power varies with the cube of air speed. Water being 850 times as dense as air, this results in much higher power production from waves averaged over time.

Wave energy generation is a developing technology. Although many wave energy devices have been invented only a small number have been tested and evaluated and even fewer of these have been tested in ocean waves - testing is usually undertaken in a wave tank.

A variety of technologies have been proposed to capture the energy from waves. Some of the more promising designs are undergoing demonstration testing at commercial scales.

Wave technologies have been designed to be installed in near shore, offshore, and far offshore locations. While all wave energy technologies are intended to be installed at or near the water's surface, they differ in their orientation to the waves with which they are interacting and in the manner in which they convert the energy of the waves into other energy forms, usually electricity. The following wave technologies have been the target of recent development.

Terminator devices extend perpendicular to the direction of wave travel and capture or reflect the power of the wave. These devices are typically onshore or nearshore; however, floating versions have been designed for offshore applications. The oscillating water column is a partially submerged, hollow structure that is installed in the ocean. It is open to the sea below the water line, enclosing a column of air on top of a column of water. Waves cause the water column to rise and fall, which in turn compresses and decompresses the air column. This trapped air is allowed to flow to and from the atmosphere via a Wells turbine, which has the ability to rotate in the same direction regardless of the direction of the airflow. The rotation of the turbine is used to generate electricity. A point absorber is a floating structure with components that move relative to each other due to wave action (e.g., a floating buoy inside a fixed cylinder). The relative motion is used to drive electromechanical or hydraulic energy converters.

Attenuators are long multisegment floating structures oriented parallel to the direction of the waves. The differing heights of waves along the length of the device causes flexing where the segments connect, and this flexing is connected to hydraulic pumps or other converters.

Overtopping devices have reservoirs that are filled by incoming waves to levels above the average surrounding ocean. The water is then released, and gravity causes it to fall back toward the ocean surface. The energy of the falling water is used to turn hydro turbines. Specially built seagoing vessels can also capture the energy of offshore waves. These floating platforms create electricity by funneling waves through internal turbines and then back into the sea.

The above-mentioned ocean wave energy technologies suffer from at least one of the following problems: i. They are not viable due to high structural costs.

ii. They require complex power take off systems which are difficult to maintain at sea.

iii. They are very susceptible to stormy condition at sea and thus more prone to damage.

iv. They are capable of converting only a fraction of energy.

v. They have low efficiency due to number of stages to achieve grid voltage power. vi. They involve complex mechanisms which need more maintenance and are prone to breakdowns which are big disadvantages for any offshore device.

Hence it is necessary to develop such an ocean wave energy technology which will be free from aforesaid problems.

OBJECTS OF THE INVENTION

The main object of the present invention is to provide a wave energy convertor device which alleviates all deficiencies associated with prior art ocean wave energy technologies.

Another object of the invention is to provide a device for generating electrical energy using ocean waves which is easy to install and maintain.

Yet another object of the invention is to provide a device for generating electrical energy using ocean waves which is economic to operate and maintain.

Yet another object of the invention is to provide a device for generating electrical energy using ocean waves which converts maximum wave energy. Still another object of the invention is to provide a device for generating electrical energy using ocean waves which can sustain extreme ocean conditions.

Still another object of the invention is to provide a device for generating electrical energy using ocean waves which is of reasonable size and requires less space for installation. Yet another object of the invention is to provide a device for generating electrical energy using ocean waves which generates electricity at its full rated capacity during extreme conditions without need of shutdown, keeping up the capacity factor.

STATEMENT OF THE INVENTION

Accordingly in order to achieve the aforesaid objects, the present invention provides a device for generating electrical energy using ocean waves, the device comprising: a tunnel like structure having two ends being named as first end and second end, the tunnel like structure is open at both ends and defines a water column inside it when installed in the ocean, the first end of the tunnel like structure faces upper surface of the ocean into the atmosphere whereas the second end faces bottom of the ocean inside the water; a pair of fixed floats being attached on each side of the first end of tunnel like structure and are provided diametrically opposite to each other, the fixed floats are parallel to a direction of ocean wave travel; a pair of articulated floats being attached on each side of the first end of tunnel like structure and are provided diametrically opposite to each other, the articulated floats are perpendicular to the fixed floats and to the direction of ocean waves travel, the articulated floats comprises a water tight void chamber being occupied with air at atmospheric pressure and the rest of the space being partially filled water; a turbine being accommodated inside the tunnel like structure, the turbine comprises a rotating shaft and a unidirectional rotor, the unidirectional rotor is rotatably mounted over the periphery of the shaft, the unidirectional rotor faces the second end of the tunnel like structure; a direct drive generator being provided at the first end of tunnel like structure and connected to the shaft of turbine; wherein :~

- the density of the fixed floats and articulated floats is adjusted according to the total weight of the device so that the all floats stay upto a maximum of 90% under water line,

- the articulated floats are attached to the tunnel like structure in conjunction with gas springs to enable free movement of the articulated floats to align themselves according to the shape of the passing wave and to provide surge impetus to upward and downward motion of the tunnel like structure, while storing the energy in the gas springs and provide impetus to the subsequent upward motion of the tunnel like structure using the stored energy in the gas springs, and

- the fixed and articulated floats provide driving force to move the tunnel like structure up and down, the up and down movement of the tunnel like structure enables the water column inside it to generate force which results into oscillating motion for driving the unidirectional turbine rotor to rotate the direct drive generator through the shaft and generate electrical energy. As per one of the embodiment of the invention, plurality of aforesaid devices are connected to each other in series in a power generating system.

BRIEF DESCRIPTION OF THE DRAWINGS

Fig. 1 : Shows perspective view of the device for generating electrical energy using ocean waves in accordance to present invention wherein device is installed in the ocean.

Fig. 2 : Shows front view of the device for generating electrical energy using ocean waves.

Fig. 3 : Shows side view of the device for generating electrical energy using ocean waves.

Fig. 4 : Shows top view of the device for generating electrical energy using ocean waves.

Fig. 5 : Shows the perspective view of the turbine rotor.

Fig. 6 : Shows sectional view of rotor blades of the turbine.

Fig. 7 : Shows the different movements of rotor blades of the turbine.

Figs. 8-10 : Show different positions of articulated floats as per the wave travel, up and down motion of the tunnel like structure as well as water column and direction of rotation of rotor and shaft.

Fig. 11 : Shows assembly of plurality of devices of figure 1 connected in mooring lines.

Fig. 12 : Shows assembly of plurality of devices of figure 1 connected in series in a power generation system. DETAILED DESCRIPTION OF THE INVENTION

The features, nature, and advantages of the disclosed subject matter will become more apparent from the detailed description set forth below when taken in conjunction with the drawings.

Meaning of the reference numerals which are used in figures 1 to 12 are as follows:

1 : Device

2 : Tunnel like structure

2a : Upper end of Tunnel like structure

2b : Lower end of Tunnel like structure

3a : Fixed float

3b : Fixed float

4a : Articulated float

4b : Articulated float

5 : Water tight void chamber

5a : Extended arm

5b : Pivot Joint

6 : Turbine

7 : Shaft

7a : Shaft support

8 : Rotor

9a : Blade

9b : Blade

9c : Blade

9d : Blade

9e : Blade

9f : Blade

10 : Direct drive generator 11 : Fly wheel

12 : Fly wheel

13 : Gas spring

14 : Water line

15 : Sea bed

16 : Mooring line

17 : Sinker

18 : Floater

1 Chain link

20 : Pile

Referring to figures 1 to 4, different views of a device (1) for generating electrical energy using ocean waves in accordance to the present invention are shown. The device (1) includes a tunnel like structure (2), a pair of fixed floats (3a, 3b), a pair of articulated floats (4a, 4b), a turbine (6) and a direct drive generator (10).

The tunnel like structure (2) includes two ends (2a, 2b). The tunnel like structure (2) is open at both ends and defines a water column inside it when installed in the ocean. The upper end (2a) of the tunnel like structure (2) faces upper surface of the ocean into the atmosphere whereas the lower end (2b) faces bottom of the ocean. The tunnel like structure (2) is kept open at both ends so that the water column can easily oscillate allowing the air to vent out from the top when the water is flowing in from the bottom, during downward motion and vice-versa. The lower end (2b) of tunnel like structure (2) flares out to enable optimal incoming and outgoing of the water. The flaring out kind of design forms a Funnel in order to increase the velocity of the water through the turbine (6) as it enters and exits during oscillation. The pair of fixed floats (3a, 3b) is attached on each side of the upper end of tunnel like structure (2). The fixed floats (3a, 3b) are provided diametrically opposite to each other. The fixed floats (3a, 3b) are kept parallel to a direction of ocean wave travel. The fixed floats (3a, 3b) absorb power from the heaving motion (potential energy) of the passing waves.

The pair of articulated floats (4a, 4b) is attached on each side of the upper end of tunnel like structure (2). The attachment is made with extended arms (5a) which are hinged on Pins at the pivot joints (5b) to provide free movement and to align the articulated floats (4a, 4b) which are provided diametrically opposite to each other according to shape of the passing wave. The articulated floats (4a, 4b) are kept perpendicular to the fixed floats (3a, 3b) on the horizontal plane and to the direction of ocean waves travel. The articulated floats (4a, 4b) exploit the surge (kinetic) energy of the passing waves. A water tight void chamber (5) is provided in each of the articulated floats (4a, 4b). The water tight void chamber (5) is filled with air at atmospheric pressure and the rest of the space being partially filled water which act as dynamic ballasts to aid phase control of the device (1) as the articulated floats (4a, 4b) pitch.

The density of the fixed floats (3a, 3b) and articulated floats (4a, 4b) is adjusted according to the total weight of the device (1) so that the all floats stay up to a maximum of 90% under water line (14). This is an important aspect which is a basic key to survivability during extreme sea conditions. The self aligning articulated float design also takes care of any size of waves by adjusting to the shape of traveling wave. Under stormy conditions, if the wavelength surpasses the total length of the device (1), then the device (1) will just ride the wave avoiding any potential detrimental effects of its enormous force. The articulated floats (4a, 4b) are also attached to the tunnel like structure (2) in conjunction with gas springs (13). In case of big surges, the gas springs (13) dampen the downward motion of the tunnel like structure (2) while storing the energy in the gas springs and provide impetus to the subsequent upward motion of the tunnel like structure (2) using the stored energy in the gas springs (13). The fixed and articulated floats (3a, 3b, 4a, 4b) provide driving force to move the tunnel like structure (2) up and down.

The turbine (6) is accommodated inside the tunnel like structure (2). The turbine (6) includes a rotating shaft (7) and a unidirectional rotor (8). The unidirectional rotor (8) is rotatably mounted over the periphery of the shaft (7). The unidirectional rotor (8) faces the lower end (2b) of the tunnel like structure (2). The unidirectional turbine (6) rotor (8) comprises a plurality of blades (9a-9f) connected to a hub.

Referring to figure 6, the six blades (9a-9f) along with rotor (8) is shown. In figure 7 different positions of the blade are shown. The blades (9a-9f) are designed symmetrically to self pitch at 15 degrees on either side of the plane of rotation as per the direction of water running through the turbine (6) perpendicularly to provide lift on the blades for maximum efficiency. Such particular design of the blades (9a-9f) ensure running of the rotor (8) in only one direction irrespective of the direction of water flow. All the blades (9a-9f) simultaneously change the angle along the radial axis due to sheer force of water to run the rotor (8) in one direction only irrespective of the direction of flow. As the water column flows past the unidirectional turbine (6) it also creates a wake rotation in contra-direction to the turbine (6) in the form of a swirl behind it. This wake swirl is also unidirectional but always in the opposite direction with respect to the running turbine (6). As and when, the flow of oscillating water column changes direction in the tunnel like structure (2), this swirl moving in contra- direction confronts the running turbine (6) and assists in decreasing the angle of attack and also the drag on the blades (9a-9f) thus also increasing and maintaining the tip speed ratio, efficiency and power coefficient.

The shaft (7) is supported and aligned in the center of the tunnel by means of shaft supports (7a) with bearings. A one way clutch is provided for restricting the movement of shaft (7) in one way direction of the unidirectional turbine (6) rotor (8) when transmitting mechanical power to the generator and free running momentarily by virtue of the flywheel inertia while reversing direction during oscillations.

The direct drive generator (10) is provided at the upper end (2a) of tunnel like structure (2) and connected to the shaft (7) of turbine (6). The direct drive generator (10) is a slow moving generator with plurality of poles which does not need a gear-box to move it at high RPM. The direct drive generator (10) also includes two flywheels (1 1, 12) one below and the other above it to smoothen the power and the two flywheels (1 1, 12) store the mechanical energy and try to maintain the rotation speed of the direct drive generator (10) as constantly as possible in one direction during the reversing motions of the oscillating column. The unidirectional turbine (6) rotor (8) keeps the direct drive generator (10) running in one direction at close to constant speed with the help of the flywheels (1 1 , 12). This will also benefit the associated power electronics needed to electrically tie the device (1) to feed the grid.

Now again referring to figure 1 , the installation of the device (1) of present invention in the ocean is illustrated. The articulated floats or tunnel like structure (2) are connected to the Mooring lines (16) for the installation of the device (1) in the ocean. The Mooring lines (16) with the assistance of Chain link (19) with floater (18) and sinker (17) is connected to a pile (20). The chain link (19) is anchored to the pile (20). The pile (20) is provided into the ocean bed (15). The mooring lines (16), chain link (19), floater (18) and sinker (17) maintain the sufficient slack. The lines & links are made of sea-worthy grade materials. Generally mooring lines are made of high strength polymers or wire rope and the chain links of high tensile steel.

Several wave energy convertor device units (1) of the present invention can be collectively combined to create an offshore floating wave farm in a power generation system, on oceans with a typical depth of 50-70 meters. The set up is shown in figure 1 1 and 12. Energy can be created by the rotational motion of turbines turned by the up/ down motion resulting from specially profiled articulated floats placed in the sea. This energy is directly converted into electricity through direct drive permanent magnet generators.

The wave energy convertor device (1) of the present invention can also be used with other types of power take-offs already being commercialized such as Linear Generators, Hydraulic pumps/ motors, oscillating water columns etc., though it would be prudent to mention that the Unidirectional Turbine (6) as proposed would be the most effective with minimum trade-off. The direct drive generator (10) eliminates all of the moving parts in the energy train associated with the current hydraulic conversion systems of attenuators and Gearbox design of others. The Slow Speed, (but High Power Output due to large cross sectional area) ensures less wear and tear within the mechanical components. A large wave will have wave-length proportional to its wave-height with a longer wave-period as well. So the turbine (6) tunnel only has to travel a longer distance up and down at almost the same speed as buoyant force will be constant. Hence power can still be generated at its full rated capacity during extreme conditions without the need to shutdown, keeping up the capacity factor.

WORKING OF THE DEVICE OF THE PRESENT INVENTION:

- After installation of the device (1) in the ocean, the passing waves provide motion to the fixed floats and articulated floats. The fixed and articulated floats provide driving force to move the tunnel like structure (2) up and down. The up and down movement of the tunnel like structure (2) enables the water column inside it to generate force which results into oscillating motion for driving the unidirectional turbine rotor (8) to rotate the direct drive generator in one direction only, through the shaft and generate electrical energy.

ADVANTAGES OF THE DEVICE FOR GENERATING ELECTRICAL ENERGY USING OCEAN WAVES OF THE PRESENT INVENTION: i. Its unique Articulated Floats help in capturing more energy from both components of wave, the vertical (Heave) as well as the Horizontal (Surge). ii. Its articulated Floats self-adjusts its natural frequency which not only helps to converge energy captured to run the turbine inside the tunnel but will also ride the waves safely under stormy conditions. iii. There is no need for shut down under any conditions as it cannot exceed its maximum rated RPM by virtue of its design. iv. It consists of minimal moving parts. It does not require gear box. Hence it has very simple construction. v. It has normal minimal routine maintenance. vi. It is environmental friendly as it does not cause any kind of pollution in air and water. vii. It is quieter and much less visually obstructive than other energy generating devices such as wind devices. viii. Infrastructure cost associated with it is very less.

Further modifications and alternative embodiments of various aspects of the invention will be apparent to those skilled in the art in view of this description. Accordingly, this description is to be construed as illustrative only and is for the purpose of teaching those skilled in the art the general manner of carrying out the invention. Elements and materials may be substituted for those illustrated and described herein, parts and processes may be reversed, and certain features of the invention may be utilized independently, all as would be apparent to one skilled in the art after having the benefit of this description of the invention. Changes may be made in the elements described herein without departing from the spirit and scope of the invention.

Claims

1. A device for generating electrical energy using ocean waves, the device comprising: a tunnel like structure having two ends being named as first end and second end, the tunnel like structure is open at both ends and defines a water column inside it when installed in the ocean, the first end of the tunnel like structure faces upper surface of the ocean into the atmosphere whereas the second end faces bottom of the ocean into the water; a pair of fixed floats being attached on each side of the first end of tunnel like structure and are provided diametrically opposite to each other, the fixed floats- are parallel to a direction of ocean wave travel; a pair of articulated floats being attached on each side of the first end of tunnel like structure and are provided diametrically opposite to each other, the articulated floats are perpendicular to the fixed floats and to the direction of ocean waves travel, the articulated floats comprises a water tight void chamber, being occupied with air at atmospheric pressure and the rest of the space being partially filled with water; a turbine being accommodated inside the tunnel like structure, the turbine comprises a rotating shaft and a unidirectional rotor, the unidirectional rotor is rotatably mounted over the periphery of the shaft, the unidirectional rotor faces the second end of the tunnel like structure; a direct drive generator being provided at the first end of tunnel like structure and connected to the shaft of turbine; wherein:

- the articulated floats are attached to the tunnel like structure in conjunction with gas springs to enable free movement of the articulated floats at the pivot joints to align themselves according to the shape of the passing wave and in case of big surges to dampen the downward motion of the tunnel like structure while storing the energy in the gas springs and provide impetus to the subsequent upward motion of the tunnel like structure using the stored energy in the gas springs, and

- the fixed and articulated floats provide driving force to move the tunnel like structure up and down, the up and down movement of the tunnel like structure enables the water column inside it to generate force which results into oscillating motion for driving the unidirectional turbine rotor to rotate the direct drive generator through the shaft and generate electrical energy.

2. The device as claimed in claim 1 wherein the second end of tunnel like structure flares out to enable optimal incoming and outgoing of the water.

3. The device as claimed in claim 1 wherein the unidirectional turbine rotor comprises a plurality of blades connected to a hub.

4. The device as claimed in claim 3 wherein the plurality of blades swivel 15° on either side to ensure running of the rotor in only one direction irrespective of the direction of water flow.

5. The device as claimed in claim 1 wherein the shaft is supported and aligned in the centre of the tunnel like structure by means of a supporter.

6. The device as claimed in claim 1 further comprising a one way clutch for restricting the movement of shaft in one way direction of the unidirectional turbine rotor.

7. The device as claimed in claim 1 wherein the direct drive generator comprises a pair of flywheels.

8. A power generating system for generating electricity using ocean waves comprising a plurality of devices as claimed in claim 1 being connected to each other in series.