WO2016124880A1

WO2016124880A1 - Apparatus for generating electricity from an ocean current

Info

Publication number: WO2016124880A1
Application number: PCT/GB2016/000020
Authority: WO
Inventors: Patrick James Mulvey
Original assignee: OCEAN CURRENT ENERGY LLC
Current assignee: OCEAN CURRENT ENERGY LLC
Priority date: 2015-02-06
Filing date: 2016-01-28
Publication date: 2016-08-11
Anticipated expiration: 2017-08-06
Also published as: GB201502072D0

Abstract

Apparatus (2) for generating electricity from an ocean current, which apparatus (2) comprises: (i) an array (4) of electrical generators (6), with each electrical generator (6) comprising a housing (8), a turbine (10) in the housing (8), and a conduit (12) which is in the housing (8) and which is for enabling ocean water to pass through the housing (8) and over the turbine (10) such as to cause the turbine (10) to rotate and generate electricity, the housing (8) having straight sides (14), and the housings (8) in the array (4) being connected together such that each housing (8) is in contact along at least two of its sides (14) with adjacent housings (8); (ii) at least one ballast compartment (16) inside each housing (8), the ballast compartment (16) being such that ocean water is admitted to cause the electrical generator (6) to sink in the ocean, and such that ocean water is expelled to cause the electrical generator (6) to rise in the ocean; (iii) control means (18) for controlling: (a) the admission of ocean water into the ballast compartment (16) in order to provide the electrical generator (6) with a negative buoyancy whereby the electrical generator (6) is able to sink to a required depth in the ocean; (b) the expulsion of ocean water from the ballast compartment (16) in order to provide the electrical generator (6) with a positive buoyancy whereby the electrical generator (6) is able to rise to a required depth in the ocean; and (c) the admission and expulsion of the ocean water in order to provide the electrical generator (6) with a neutral buoyancy whereby the electrical generator (6) is able to float at a required depth in the ocean; and (iv) at least three lengths (20) of a restrainer, with each length (20) of the restrainer being connectable at an upper portion (22) to the array (4) and at a lower portion (24) to the ocean floor (26) whereby the array (4) is able to be maintained in a desired horizontal angular position with respect to the ocean floor (26), and the apparatus (2) being such that the control means (18) and the lengths (20) of the restrainer enable the array (4) to be positioned in the ocean at a depth where the ocean current is strongest, and in a direction which is aligned with the ocean current for maximum flow of ocean water through the housings (8).

Description

APPARATUS FOR GENERATING ELECTRICITY

FROM AN OCEAN CURRENT

This invention relates to apparatus for generating electricity from an ocean current.

There are many different known types of apparatus for generating electricity from tidal waters. The tidal waters may be ocean waters adjacent land masses, or rivers. The known apparatus is invariably secured to the ocean floor or riverbed. Such installation is complicated but able to be done due to the fact that the depth of water adjacent land masses and in rivers is usually not too great. However, if the known apparatus is to be used for generating electricity from an ocean current, then a problem arises in that the ocean current will normally be considerably away from any land mass, and at a position where the depth of water is very substantial. As the depth of water increases, so does the complexity of installing the known apparatus in an ocean flow. Often the depth of water is too great for it to be economically possible to secure the apparatus to the ocean floor. Also, with known apparatus that is secured to the ocean floor, the ocean flows or streams may be flowing near the surface of the ocean, thereby negating the effectiveness of the apparatus because it is mounted on the ocean floor where it does not receive such ocean flows or streams. It is an aim of the present invention to reduce the above mentioned problem.

Accordingly, in one non-limiting embodiment of the present invention there is provided apparatus for generating electricity from an ocean current, which apparatus comprises:

(i) an array of electrical generators, with each electrical generator comprising a housing, a turbine in the housing, and a conduit which is in the housing and which is for enabling ocean water to pass through the housing and over the turbine such as to cause the turbine to rotate and generate electricity, the housing having straight sides, and the housings in the array being connected together such that each housing is in contact along at least two of its sides with adjacent housings;

(ii) at least one ballast compartment inside each housing, the ballast compartment being such that ocean water is admitted to cause the electrical generator to sink in the ocean, and such that ocean water is expelled to cause the electrical generator to rise in the ocean;

(iii) control means for controlling:

(a) the admission of ocean water into the ballast compartment in order to provide the electrical generator with a negative buoyancy whereby the electrical generator is able to sink to a required depth in the ocean;

(b) the expulsion of ocean water from the ballast compartment in order to provide the electrical generator with a positive buoyancy whereby the electrical generator is able to rise to a required depth in the ocean; and

(c) the admission and expulsion of the ocean water in order to provide the electrical generator with a neutral buoyancy whereby the electrical generator is able to float at a required depth in the ocean; and

(iv) at least three lengths of a restrainer, with each length of the restrainer being connectable at an upper portion to the array and at a lower portion to the ocean floor whereby the array is able to be maintained in a desired horizontal angular position, and the apparatus being such that the control means and the lengths of the restrainer enable the array to be positioned in the ocean at a depth where the ocean current is strongest, and in a direction which is aligned with the ocean current for maximum flow of ocean water through the housings.

With the apparatus of the present invention, there is no need for a base structure on which the array of electrical generator stands, and there is no need to secure this base structure to the ocean floor. By avoiding the need for the base structure, it is relatively easy to secure the array of electrical generators in position in ocean waters of quite considerable depths. All that is necessary is to locate the lower portions of the three lengths of the restrainer to the ocean floor. This may be done by way of securing means in the form of a direct fixing to the ocean floor, a weighted anchor, or other securing means or combination of securing means. The securing means is able to be considerably smaller than an entire base on which the array of electrical generators would normally be mounted in known apparatus. This in turn means that it is easier with the apparatus of the present invention to transport various parts of the apparatus to offshore sites for assembly on site. The assembly on site is also much easier because it is simply necessary to secure in position the lower portions of the three lengths of restrainer. Undulations in an ocean flow then are not a problem, whereas if a large base is to be sunk to the ocean floor and secured in position, then an uneven ocean floor may well prevent this from being done.

The apparatus of the present invention is also advantageous in that the ballast compartments in the electrical generators in the array enable the apparatus to be positioned at a precise depth. If negative buoyancy is then provided, the apparatus then has no tendency to rise or fall. It is simply held in position by the length of the restrainer which act as depth tethers. Still further, the three lengths of the restrainer ensure that the array is able to be maintained in a desired horizontal angular position so that the housings of the electrical generators are aligned with the ocean current for maximum flow of ocean water through the housings. This in turn means that the turbines are able to be rotated with maximum speed and efficiency. Still further, by having the turbines aligned with the ocean current, side forces as would occur if the turbines were not so aligned are minimised. This in turn minimises wear on component parts such for example as bearings. This in turn means that the apparatus of the present invention is able to operate on site and without service maintenance and/or repair for longer periods than would otherwise be the case.

The apparatus may be one in which each of the housings has two ends which are each hexagonal in end view. Other shapes for the housing ends may be employed so that, for example, the ends may be octagonal, square or rectangular. Generally, the housings may be of any suitable shape such that their straight sides enables them securely to be connected together. Because the housings have at least two straight sides, the housings are able easily to be secured together such that all the housings are stably connected together in the entire array.

The apparatus may be one in which the conduit comprises a funnel- shaped portion at each end, and a central parallel-sided portion, the turbine being positioned in the central parallel-sided portion, and the funnel-shaped portions being such that they are able to act as a Venturi to increase the velocity of ocean water as the ocean water flows to the turbine. With the funnel-shaped portion being at each end of the turbine, there is no need to worry about directional placement of the turbine in the array. Whichever way around the turbine is placed, it is able to receive the ocean water, and the turbine is able to be rotated by the ocean water.

Each electrical generator may have two of the turbines. In this case, each one of the turbines may have vanes which are angled to best receive the ocean water from the nearest funnel-shaped portion. Two turbines are efficient due to Betz Law stating that no single turbine can capture more than 59.3% of the potential kinetic energy. Therefore, with two turbines, the second turbine is able to capture the residual kinetic energy in order to maximise power output from a single apparatus. The first turbine may capture less than 59.3% of the potential kinetic energy, in which case the second turbine is available to capture that energy which is not captured by the first turbine.

The housing may include connector means along its sides for enabling connection to adjacent housings. The connector means are preferably constructed such that they enable easy connection together of the different housings to form the array. The connector means may be, for example, apertured lugs. Other types of connector means may be employed. The connected means may be a hinged connector means.

The apparatus may include strap means passing around the outside of the array and facilitating the holding together of the housings in the array.

The control means may include gas-operable ballast means for injecting gas into the ballast compartment to expel ocean water when a positive buoyancy is required. The gas may be compressed air, or any other suitable and appropriate gas such for example as an inert gas. The control means may include inlet control means for allowing ocean water to enter the ballast compartment for negative buoyancy.

The control means may include at least one sensor for sensing the position of the apparatus in the ocean, whereby the control means is able to operate consequent upon receiving data from the sensor.

There may be at least one depth sensor for use in maintaining the apparatus at a desired depth. Additionally or alternatively there may be at least one direction sensor for use in maintaining the apparatus in a desired horizontal rotational direction in the ocean current and thereby to ensure that a maximum of ocean water is able to pass through the conduit.

The apparatus may be one in which there are one, two or more of the ballast compartments for each electrical generator. If there are two ballast compartments, then the second ballast compartment may act as an auxiliary ballast compartment. The second ballast compartment may be smaller than the first ballast compartment if desired. Alternatively both ballast compartments may be of the same size.

The apparatus of the present invention is such that there are at least three lengths of the restrainer. Thus the apparatus may employ three, four or more lengths of the restrainer as desired. The lengths of the restrainer will usually be lengths of cable. Alternatively, chains or other devices may be employed. Usually the three lengths of the restrainer will be separate lengths. However, if desired, the three lengths may be formed by one single piece of restrainer which goes up and down between the array and the ocean bed. The apparatus may include stabiliser means for stabilising the array as it floats in the ocean current. The stabiliser means may be a wing arrangement. Other types of stabiliser arrangements may be employed.

Embodiments of the invention will now be described solely by way of example and with reference to the accompanying drawings in which:

Figure 1 is a perspective view of first apparatus of the present invention;

Figure 2 is an enlarged view of the part circled in Figure 1 ;

Figure 3 is a side view of the apparatus as shown in Figure 1 ;

Figure 4 is an end view of the apparatus as shown in Figure 1 ;

Figure 5 is a section through an electrical generator forming part of an array of electrical generators in the apparatus shown in Figure ;

Figure 6 is an end view of the electrical generator as shown in Figure

5;

Figure 7 is a perspective view of half of the electrical generator shown in Figure 5;

Figure 8 is a perspective view of second apparatus of the present invention;

Figure 9 is a side view of the apparatus as shown in Figure 8;

Figure 10 is a perspective view of third apparatus of the present invention;

Figure 1 is an enlarged view of the part circled in Figure 10;

Figure 12 is a side view of the apparatus as shown in Figure 10; Figure 13 is a perspective view of fourth apparatus of the present invention;

Figure 14 is an enlarged view of the circled at the apex of the apparatus shown in Figure 13;

Figure 15 is a side view of the apparatus as shown in Figure 13;

Figure 16 is an enlarged view of the circled part at the right hand corner of the apparatus shown in Figure 13;

Figure 17 is a perspective view of fifth apparatus of the present invention;

Figure 18 is a side view of the apparatus as shown in Figure 16; and

Figure 19 is an end view of the apparatus shown in Figure 16.

Referring to Figures 1 - 7, there is shown apparatus 2 for generating electricity from an ocean current. The apparatus 2 comprises an array 4 of electrical generators 6. Each electrical generator 6 comprises a housing 8, a turbine 10 in the housing 8, and a conduit 12. The conduit 12 is in the housing 8. The conduit 12 is for enabling ocean water to pass through the housing 12 and over the turbine 10 such as to cause the turbine 10 to rotate and generate electricity.

The housing 8 has straight sides 14. The housings 8 in the array 4 are connected together such that each housing 8 is in contact along at least two of its sides 14 with adjacent housings 8. This enables the housings 8 securely to be connected together.

The apparatus 2 also comprises at least one ballast compartment 16 inside each housing 8. The ballast compartment 16 is such that ocean water is admitted to cause the electrical generator 6 to sink in the ocean, and such that ocean water is expelled to cause the electrical generator 6 to rise in the ocean.

The apparatus 2 also comprises control means 18. The control means 18 is for controlling the admission of ocean water into the ballast compartment 16 in order to provide the electrical generator 6 with a negative buoyancy, whereby the electrical generator 6 is able to sink to a required depth in the ocean.

The control means 18 is also able to expel ocean water from the ballast compartment 16 in order to provide the electrical generator 16 with a positive buoyancy, whereby the electrical generator 16 is able to rise to a required depth in the ocean.

The control means 18 is also able to control the admission of ocean water to the ballast compartment 16, and expulsion of ocean water from the ballast compartment 16. This is in order to provide the electrical generator 6 with a neutral buoyancy, whereby the electrical generator 6 is able to float at a required depth in the ocean.

The apparatus 2 also comprises three lengths 20 of a restrainer. Each length 20 of the retainer is connectable at an upper portion 22 to the array 24 and at a lower portion 24 to the ocean floor 26. The array 4 is thus able to be maintained in a desired horizontal angular position respect to the ocean floor 26

The apparatus 2 is such that the control means 18 and the lengths 20 of the restrainer enable the array to be positioned in the ocean at a depth where the ocean current is strongest, and in a direction which is aligned with the ocean current for maximum flow of ocean water through the housings 8. In this way, the apparatus 2 is able to be positioned at a desired depth in water so that the apparatus 2 is able to operate efficiently. The tethering to the ocean floor 26 is simple as compared with providing the array 12 with some kind of solid base which would then need anchoring to the ocean floor, especially if the ocean floor is undulating and not easily able to accept the bottom of the base. Still further, the apparatus 2 is able to be positioned in directional alignment with the ocean current. Not only does this enable maximum flow of ocean water through the housings, but it avoids the flow of the ocean water acting at an angle on the sides of the housings and attempting to turn the array 4, thereby placing unnecessary strain and wear on bearings or other parts of the apparatus 2.

The apparatus 2 further comprises electrical power take-off means 28 comprising an electric cable 30 leading to an electrical junction box 32. The electrical junction box 32 feeds a further electrical cable 34 which takes the generated electricity to wherever desired, for example to an electrical substation.

As best shown in Figures 2, 5 and 6, the housing has two ends 36, 38. Each end 36, 38 is hexagonal in end view.

Figures 5 and 7 show how the conduit 12 comprises a funnel-shaped portion 40 at each end, and a central parallel-sided portion 42. The turbine 10 is positioned in the central parallel-sided portion 42. The funnel-shaped portions 40 are such that they are able to act as a Venturi to increase the velocity of ocean water as the ocean water flows to the turbine 10.

As shown in Figure 5, there are two of the turbines 10. Each turbine comprises a stator 44 and a rotor 46. The rotor 46 has vanes 48 as shown. The rotor 46 rotates about a central shaft 50 mounted at its ends in bearings 52.

As best shown in Figure 6, the housing 8 includes connector means in the form of apertured lugs 54. The lugs 54 are positioned as shown along the sides of the housing 8 and they enable the connection of each housing 8 to adjacent housings 8. The lugs 54 may be hinged lugs which can be folded from the position shown in Figure 6 if they are not required for use.

Figure 2 shows how the array 4 includes strap means at each end of the array 4. The strap means 6 passes around the outside of the ends of the array 4 as shown, and it facilitates the holding together of the housings 8 in the array 4.

As shown in Figures 5 and 7, the control means 18 includes gas- operable ballast means 58 for injecting gas into the ballast compartment 16 to expel ocean water when a positive buoyancy for the electrical generator 6 and/or the entire array 4 is required. The ballast means 58 comprises a ballast purge gas cylinder 60 and a water pump 62. There is one of the gas cylinders 60 and one of the water pumps 62 for each one of the illustrated two ballast compartments 16 which form main ballast compartments 16. The housing 8 is also provided with an auxiliary ballast compartment 64 in each of its two halves. The control means 18 may include at least one position sensor for sensing the position 3 of the apparatus 2 in the ocean, whereby the control means 18 is able to operate consequent upon receiving data from the sensor. One position sensor is a depth sensor 66 (see Figure 14) for maintaining the apparatus at a desired depth. Another position sensor is a direction sensor 68 (see Figure 14) for use in maintaining the apparatus 2 in a desired horizontal rotational direction in the ocean current. The two sensors 66, 68 ensure that a maximum of the ocean current is able to pass through the conduit 12 because the housing 8 is in the ocean current and is aligned with the ocean current. Also, because the housing 8 is aligned with the ocean current, the ocean current does not try and turn the housing 8, as it would do if the housing 8 were not aligned with the ocean current. This in turn helps to avoid wear on bearings and another parts of the apparatus 2.

The two sensors 66, 68 are housed in a housing 69. The housing 69 may be provided with a camera.

As shown in Figure 5, there are a main ballast compartment 16 and an auxiliary ballast compartment 64 for each electrical generator 6. In alternative embodiments of the invention, there may be just one ballast compartment 6 for the entire electrical generator 6, and optionally just one auxiliary ballast compartment 64 for each electrical generator 6.

Figure 7 shows how the electrical generator 2 is able to be formed in two halves. The inner edge of each half is provided with a connecting flange 65 that is able to be bolted to an adjacent connecting flange 65 on the other half of the housing 8. Figure 7 also shows how there are two of the gas cylinders 60 and two of the water pumps 62.

In subsequent Figures, similar parts as in Figures 1 - 7 have been given the same reference numerals for ease of comparison and understanding.

Figures 8 and 9 show second apparatus 70 of the present invention. Figures 8 and 9 are like Figures 1 and 3 and they illustrate how the apparatus 70 is able to have four of the lengths 20 of the restrainer.

Figures 10, 1 1 and 12 show third apparatus 72 of the present invention. The apparatus 72 is like the apparatus 2, shown in Figures 1 , 2 and 3 except that the apparatus 72 is additionally provided with stabiliser means in the form of a stabiliser wing 74.

Figures 13, 14, 15 and 16 show fourth apparatus 76 of the present invention. The apparatus 76 is like that shown in Figures 8 and 9 except that the apparatus 70 is additionally provided with a stabiliser wing 74 and a winch 76. The stabiliser wing 74 comprises a directional control rudder 78 and an attitude control elevator 80. The winch 76 is provided with a back-up battery 82. There is one of the winches 76 and back-up batteries 82 at each lower end of the four lengths 20 of the restrainer.

Figures 17, 18 and 19 show six units of the apparatus 72 mounted on the ocean floor 26, with an electrical cable 34 for taking off electricity generates by the six units of the apparatus 72. The generated electricity is taken to an electrical sub-station 84 mounted on a shore 86. The apparatus 2, 70, 72, 76 are easily installed by virtue of the use of the lengths 20 of the restrainer. The lengths 20 will usually be lengths of cable but they may be lengths of chain or other material as may be desired. The lengths 20 are easily able to be secured to the ocean floor 26. The lengths 20 are able to maintain the array or arrays 4 at a required depth and angular rotation in the ocean water, in order to ensure that the apparatus 2 is positioned in an ocean current and such as to obtain maximum flow of the ocean current through the electrical generator 6. Connection of the lengths 20 to the array 4 is easily affected. The array 4 can be assembled on site.

It is to be appreciated that the embodiments of the invention described above with reference to the accompanying drawings have been given by way of example only and that modifications may be effected. Thus, for example, the housings 8 may be other than hexagonal in end view and so they may be octagonal, square or rectangular in end view. Various types of turbines in the electrical generator 6 may be employed. More than three lengths 20 of the restrainer may be employed. The control means 18 may be programmed to control a wide variety of operational aspects of the apparatus 2, including the positioning of the array 4, the amount of electricity generated, and the supply of the electricity to the sub-station 76. The electrical cable 34 can be arranged to run over long distances over the ocean floor 26 prior to rising up a face 88 to reach the shore or other land formation 86. Individual components shown in the drawings are not limited to use in their drawings and they may be used in other drawings and in all aspects of the invention.

Claims

1. Apparatus for generating electricity from an ocean current, which apparatus comprises:

(iii) control means for controlling:

(a) the admission of ocean water into the ballast compartment in order to provide the electrical generator with a negative buoyancy whereby the electrical generator is able to sink to a required depth in the ocean; (b) the expulsion of ocean water from the ballast compartment in order to provide the electrical generator with a positive buoyancy whereby the electrical generator is able to rise to a required depth in the ocean; and

2. Apparatus according to claim 1 in which the housing has two ends which are each hexagonal in end view.

3. Apparatus according to claim 1 or claim 2 in which the conduit comprises a funnel-shaped portion at each end, and a central parallel-sided portion, the turbine being positioned in the central parallel-sided portion, and the funnel-shaped portions being such that they are able to act as a Venturi to increase the velocity of ocean water as the ocean water flows to the turbine.

4. Apparatus according to any one of the preceding claims in which there are two of the turbines.

5. Apparatus according to claim 4 in which each one of the turbines has vanes which are angled to best receive the ocean water from the nearest funnel-shaped portion.

6. Apparatus according to any one of the preceding claims in which the housing includes connector means along its sides for enabling connection to adjacent housings.

7. Apparatus according to any one of the preceding claims and including strap means passing around the outside of the array and facilitating the holding together of the housings in the array.

8. Apparatus according to any one of the preceding claims in which the control means included gas-operable ballast means for injecting gas into the ballast compartment to expel ocean water when a positive buoyancy is required.

9. Apparatus according to any one of the preceding claims in which the control means includes at least one sensor for sensing the position of the apparatus in the ocean, whereby the control means is able to operate consequent upon receiving data from the sensor.

10. Apparatus according to claim 9 in which there is at least one depth sensor for use in maintaining the apparatus at a desired depth.

11. Apparatus according to claim 9 or claim 10 in which there is at least one direction sensor for use in maintaining the apparatus in a desired horizontal rotational direction in the ocean current and thereby to ensure that a maximum of ocean water is able to pass through the conduit.

12. Apparatus according to any one of the preceding claims in which there are one, two or more of the ballast compartments for each electrical generator.

13. Apparatus according to any one of the preceding claims in which the lengths of the restrainer are lengths of cable.

4. Apparatus according to any one of the preceding claims and including stabiliser means for stabilising the array as it floats in the ocean current.

15. Apparatus according to claim 14 in which the stabiliser means is a wing arrangement.