Yoke and swivel arrangement for use on a hydrokinetic system

Abstract

A hydrokinetic system includes a duct having an interior surface defining a central passageway and an exterior surface, one or more rotors suspended within the duct via one or more struts coupled to the one or more rotors, a first slidable carriage on the exterior surface of the duct, a second slidable carriage on the exterior surface of the duct opposite from the first slidable carriage, and a yoke coupled between the first slidable carriage and the second slidable carriage. The duct is substantially circular in cross-section. Both the first slidable carriage and the second slidable carriage are designed to laterally slide along a longitudinal direction of the duct. The yoke is configured to rotate about an axis passing through the first slidable carriage and the second slidable carriage.

Description

YOKE AND SWIVEL ARRANGEMENT FOR USE ON A HYDROKINETIC SYSTEMTECHNICAL FIELD

[0001] The present disclosure relates generally to systems for the generation of electrical power from hydrodynamic forces and. in particular, to the generation of electricity from tidal and river flows.BACKGROUND

[0002] Systems designed to extract energy from natural flows in oceans and rivers have been available for years but issues such as efficiency, cost, deployment, reliability and environmental impact have prevented them from becoming reliable sources of power generation. There has been a long felt need to address these issues, and improvements in the field are necessary in order to increase the use of these energy sources as pail of the world’s energy portfolio.SUMMARY

[0003] Designs of mechanical structures used to provide robust support for a hydrokinetic apparatus and to facilitate the running of electrical cables from the hydrokinetic apparatus are described herein.

[0004] According to an embodiment, a hydrokinetic system includes a duct having an interior surface defining a central passageway and an exterior surface, one or more rotors suspended within the duct via one or more stints coupled to the one or more rotors, a first slidable camage on the exterior surface of the duct, a second slidable carriage on the exterior surface of the duct opposite from the first slidable carriage, and a yoke coupled between the first slidable carriage and the second slidable carriage. The duct is substantially circular in crosssection. The central passageway has a first diameter and the duct further includes a first opening with a second diameter and a second opening with a third diameter with the second and third diameters both being greater than the first diameter. Both the first slidable carriage and the second slidable carriage are configured to laterally slide along a longitudinal direction of the duct. The yoke is configured to rotate about an axis passing through the first slidable carriage and the second slidable carriage.

[0005] According to another embodiment, a swivel mechanism includes a housing, a first mounting plate coupled to the housing and having a first connector configured to interface with a first rod, a second mounting plate coupled to the housing opposite from the first mounting plate and having a second connector configured to interface with a second rod, arid a slip ring withinthe housing. The housing is configured to rotate about a first axis passing through the first connector and the second connector. The slip ring is configured to rotate relative to the housing about a second axis passing longitudinally along a greatest dimension of the housing.

[0006] According to another embodiment, a hydrokinetic system includes a duct configured for placement within a body of water, a yoke coupled to the duet and configured to rotate about a first axis passing through the duct, and a swivel mechanism coupled to the yoke at a first connection and a second connection on sides of the swivel mechanism. The duct includes at least one rotor coupled to at least one electrical generator. The swivel mechanism is designed to rotate about a second axis passing through the first connection and the second connection. The swivel mechanism has a first port arid a second port. The swivel mechanism includes a slip ring configured to provide a rotatable conductive path between the first port and the second port.BRIEF DESCRIPTION OF THE DRAWINGS

[0007] FIG. 1 illustrates an example hydrokinetic system having a duct with a rotatable yoke coupled to the duct and a swivel structure coupled to the yoke, according to some embodiments of the present disclosure.

[0008] FIG. 2 illustrates a cross section view of a rotor design for the hydrokinetic system, according to some embodiments of the present disclosure.

[0009] FIG. 5 illustrates the connection between a hydrokinetic system deployed on an underwater floor and a control station on land, according to some embodiments of the present disclosure.

[0010] FIG. 3 illustrates an example rotor blade design for a hydrokinetic- system, according to some embodiment s of the present disclosure.

[0011] FIG. 4A illustrates an isometric view of a swivel structure, according to some embodiments of the present disclosure.

[0012] FIG. 4B illustrates an exploded view of the swivel structure of FIG. 4A, according to some embodiments of the present disc losure.

[0013] FIG. 5 illustrates the rotation and lateral movement of the yoke coupled to the sides of the duct, according to some embodiments of the present disclosure.

[0014] FIG. 6 illustrates the connection between a hydrokinetic system deployed underwater and a power control station on land, according to some embodiments of the present disclosure.DETAILED DESCRIPTIONOVERVIEW

[0015] This disclosure is directed to hydrodynamic electric generators, and more particularly, to mechanical structures used to control their location underwater and to facilitate the routing of electrical cables. The system may be portable, such that the device is small enough to be earned on the back of a person, or by lifting between two people, and placed within a river or other location with moving water. In some other examples, the system is portable using an appropriate vehicle to bring the system to the desired location in a river or larger body of water. Individual components, such as rotors, generators, and ballast tanks can be modularly installed for easy removal and servicing without having to disturb the entire system.

[0016] The system can employ multiple rotors that extract maximum energy at relatively low speed and provide redundancy should one of the rotors fail or need servicing. The rotors are exposed to high flux by revolving around a small central hub that transmits mechanical energy via shafts or belts that are located in the shuts that connect the rotors to the housing. In some examples, there is no motor or generator housing in the flow stream, so more of the flow can be utilized. The system can be bi-directional, taking advantage of alternating tides without changing position. The rotor blades can be self-feathering in response to direction of flow. According to some embodiments, the rotors can drive independent generators and the electrical output of each can be combined or carried out through individual cables.

[0017] According to some embodiments, the hydiokinetic system includes a duct having an internal surface that is conically shaped to narrow at the waist and expand towards each opening. This reduction in cross sectional area helps to accelerate flow past the rotors, which may be centrally located within the duct. An expanding region at the exit also contributes to accelerated flow. The outer surface of the duct can match the contours of the interior surface or can include straight segments to provide an overall cylindrical shape. Any number of compartments may be formed in a space between the inner and outer walls of the duct. These compartments can house electrical and mechanical components as well as buoyancy chambers (e.g., ballast tanks) that can be filled and drained to alter the overall buoyancy and attitude of the device. The ballasting system allows the device to be towed on the water's surface and provides operators with an easy way to lower the device to its intended depth. Furthermore, the ballasting system can be used to maintain a fixed depth below the surface of the water or a fixed depth above the sea or riverbed. According to some embodiments, the hydi okinetic system can generate up to 10 kW of power

[0018] According to some embodiments, the duct is anchored to the seabed (or any surface beneath the water) via an anchoring cable that is coupled to a swivel structure. The swivel structure is coupled to a yoke that itself is coupled to sides of the duct. The arrangementprovides the duct a high degree of flexibility of movement within the water, while maintaining its anchored position. For example, the yoke is designed to couple to slidable camages on opposite sides of the duct. The slidable carriages may be coupled to tracks that allow the slidable carriages to move longitudinally along the sides of the duct. Additionally, the yoke is designed to rotate about a first axis passing through each of the slidable camages. This may allow the duct to maintain its orientation within the water regardless of the direction or speed of the current acting upon the duct.

[0019] As noted above, a swivel structure is also coupled to the yoke. According to some embodiments, the yoke may couple to opposite sides of the swivel structure, such that the swivel structure can rotate about a second axis passing through the yoke on either side of the swivel structure. According to some embodiments, the swivel structure includes a first port and a second port for interfacing with electrical cables. A conductive path may be formed between the first port and the second port via a slip ring deposed within the swivel structure. The slip ring may be coupled to a central shaft that together are free to rotate about a third axis substantially perpendicular to the second axis. Hie second port may be coupled to a lower portion of the central shaft such that the second port rotates with the central shaft and slip ring. Electrical cables may be couped between one or more generators of the hydrokinetic system and the first port, and also between the second port and one or more external power control stations. Due to the rotation of the various mechanical components about each of the first, second, and third axes, the duct of the hydrokinetic sy stem remains stabilized within the water and any tangling or undesirable pulling of the electr ical cables is reduced or eliminated.

[0020] The systems described herein are capable of providing on-demand and local power generation for a variety of applications. Locally installed batteries either within the annular compartments of the device itself, or in another nearby location connected via cables can be used to store electrical energy that is not currently being used. Power can then be drawn fr om the batteries at any time or directly from the generators within the device. A control system may be used to determine whether power is to be drawn from the batteries, fr om the generators, or from both. Example applications for the systems described herein include marine charging stations at docks or any other location where moving water is present.DUCT DESIGN

[0021] Figure 1 illustrates an example hydrokinetic system 100 that includes a duct 102 designed for use in an underwater environment, according to some embodiments. Hydrokinetic system 100 may be deployed for any length of time within the water to generate electricalenergy from the underwater currents that turn one or more rotors 104 within duct 102.According to some embodiments, the diameter of each opening of duct 102 is larger than a diameter of a midpoint of the passageway connecting the two openings. Duct 102 may have a total length of between 5 feet and 15 feet, such as around 10 feet, and a diameter at each opening between about 3 feet and about 10 feet, such as around 7 feet.

[0022] According to some embodiments, duct 102 includes a grating 106 over each of its openings to prevent large debris from entering into duct 102. Grating 106 can have a convex shape to passively cause debris to slide away from the openings of duct 102 after contacting grating 106. In some embodiments, gr ating 106 includes a repeating pattern of no smaller than one square inch, such as a repeating square patern, repeating diamond pattern, or a repeating triangular pattern. In some embodiments, grating 106, includes radially extending members connected to a middle ring, as is illustrated in Figure 1. Grating 106 can be made from stainless steel, although any other sufficiently rigid material with good anti-biofouling properties may be used as well.

[0023] Although rotors 104 within duct 102 are rotating based on the speed of the water flow, the grating 106 may be used to prevent large objects such as stumps, marine mammals, large fish, debris and divers from moving through duct 102. This helps prevent potential damage to the inside of duct 102 as well as prevent potential damage of rotors 104. In some embodiments, grating 106 is removable if or when it needs to be cleaned. In some examples, the bi-directional flow of water tln ough duct 102 will help keep grating 106 on a periodic maintenance cycle. In other cases, the device can be flipped longitudinally 180 degrees so that the flow of water passes tlnough the device in the opposite direction.

[0024] According to some embodiments, a track 108 rims longitudinally along an outside surface of duct 102. A similar hack may ran longitudinally along the outside surface of duct 102 on the opposite side (not seen in the view of Figure 1). Track 108 may have any groove shape that is designed to interface with a slidable carriage 110. According to some embodiments, slidable carriage 110 is designed to longitudinally slide along track 108 using any suitable bearing system. It should be noted that a similar slidable carriage may also be coupled to the track on the opposite side of duct 102.

[0025] According to some embodiments, a yoke 112 is coupled to slidable carriage 110 and to the slidable carriage on the opposite side of duct 102. Accordingly, yoke 112 is capable of moving longitudinally along with slidable carriage 110 along track 108. Additionally, yoke 112 may be rotatably coupled to carriage 110 such that yoke 112 can rotate about a first axis A passing through both slidable carriages on opposite sides of duct 102. In this way, duct 102 may be free to flip about first axis A in the water while yoke 112 remains in substantially the sameposition. According to some embodiments, yoke 112 may be stainless steel or another composite material with good anti-biofouling properties.

[0026] According to some embodiments. a swivel structure 114 is coupled to yoke 112. Swivel structure 114 may be centrally located along yoke 112. In an example, swivel structure 114 couples to yoke 112 at opposite sides of swivel structure 114, such that swivel structure 114 can rotate freely about a second axis B passing through the coupling locations with yoke 112. Second axis B may be substantially parallel to first axis A. Swivel structure 114 may serve any number of purposes. In an example, an anchor cable is coupled to a distal end of swivel structure and runs to an anchor that is used to maintain the position of duct 102 underwater. In an example, electrical cables that cany electrical current generated by one or more generators of hydrokinetic system 100 are coupled between ports on or near opposite ends of swivel structure 114. A slip ring may be used within swivel structure 114 to provide a rotatably conductive path between the ports, as will be discussed in more detail herein.

[0027] Since duct 102 may be anchored to the seabed and coupled to the anchoring cable via yoke 112 and swivel structure 114, duct 102 may be free to flip or rotate underwater while still remaining anchored to the ground. Furthermore, swivel structure 114 ensures that any electrical cables running between hydrokinetic system 100 and a remote power control station do not become tangled or pulled regardless of any change in the orientation of duct 102 underwater.

[0028] Figure 2 illustrates a cross-section view of duct 102 having a parabolically curved inner surface 202 and a straight outer surface 203 between the openings at opposite ends of duct 102. Accordingly, the diameter of the central passageway passing through duct 102 continually increases from the midpoint of the duct outwards to each end of the duct. The central passageway has an interior diameter that may be defined by inner surface 202 while outer surface 203 provides the overall shape of duct 102 as viewed from the outside.

[0029] The flared ends of duct 102 may be used to enhance the water flowrtlnough the central passageway. Horizontal axis turbines disposed within the central passageway are generally preferred over vertical access turbines because they are easier to self- start, have a higher efficiency and larger speed operation. In addition, horizontal axis turbines have less torque fluctuation. According to some embodiments, one role of the convergent flare (e.g., the flared end acting as the inlet) is to increase the extracted electrical power potential by increasing the mass flow or speed of the water through the central passageway. This flow directly affects the rotor(s) speed. According to some embodiments, one role of the divergent flare (e.g., the flared end acting as the outlet) is to diffuse the water as it leaves the central passageway which can, in turn, create a sucking effect drawing the water out of the central passageway at a higher rate than a straight edged cylinder.

[0030] As discussed above, the hydrokinetic system includes at least two rotors disposed within the central passageway of duct 102. In the illustrated embodiment, duct 102 includes a first rotor 204a and a second rotor 204b. According to some embodiments, rotors 204a and 204b are designed to rotate in opposite directions from one another. For example, rotor 204a may include blades that are shaped such that rotor 204a rotates clockwise while rotor 204b includes blades that are shaped such that rotor 204b rotates counterclockwise, or vice versa. Using two counter-rotating rotors provides enhanced stability for the device while also improving efficiency. Tire two rotors may be symmetrically positioned on either side of the midpoint of duct 102.

[0031] According to some embodiments, rotors 204a and 204b face opposite directions (due to their counter-rotating designs) and may be coupled to opposite ends of a common shaft 206. Each rotor also includes its own strut 208 coupled to common shaft 206. As a general overview, the water pressure caused by tidal and current flows will be tunneled through though duct 102 and will force the rotors 204a and 204b to rotate. These rotational speeds may be relatively low. however due to the pov / erful force of water flow, the torque remains high. According to some embodiments, each rotor 204a / 204b is coupled to a corresponding rotor shaft within common shaft 206, and each rotor shaft in turn is coupled to a corresponding timing belt or drive shaft that runs between common shaft 206 and a corresponding generator 210a / 210b. Accordingly, the rotational torque produced by rotor's 204a / 204b may be transferred to the timing belt or drive shaft within the corresponding strut 208 to generate electrical current at generators 210a / 210b.

[0032] According to some embodiments, each rotor 204a / 204b includes any number of rotor blades connected to a central hub that hi turn connects the rotor blades to the corresponding rotor shaft within common shaft 206. A rotor bearing may be disposed around the hub to allow the rotor blades to rotate freely. According to some embodiments, each rotor 204a / 204b includes three rotor blades in the general shape of a Kaplan blade. Each rotor blade may be formed fr om composite materials due to their strength and low-maintenance qualities.

[0033] Figure 3 illustrates example geometrical details for rotor 204a / 204b, and more particularly for the shape of the rotor blades, according to some embodiments. Each rotor 204a / 204b may be designed to have three identical rotor blades 301 extending radially from a hub 302. In some examples, rotor blades 301 may have a chord-to-diameter ratio (c / D) between about 0.225 and about 0.275 at the root and between about 0.050 and about 0.100 at the tip. In another example, rotor blades 301 have a blade-length to diameter ratio (i> / D) between about 0.2 and about 0.6 from the root to the tip. In another example, the ratio between hub 302 diameter (drat) and the rotor diameter (D) is between 0.075 and 0.100. In some embodiments, hub 302 has a diameter ( dhub) that is less than 10% of the diameter (D) of the rotor 204a / 204b, such as aroundabout 5”, such as around 3.9”.

[0034] Although dimensions may vary between certain applications, in some examples, the distance between the hubs of each of rotors 204a and 204b is between 30” and 60”. or between40” and 50”. In some examples, the distance between struts 208 is between about 20” and about 40”, such as around 31”. Struts 208 may also each have a diameter of around 1” to 5” such as, for example, around 3” or between 3” and 5”. According to some embodiments, a distance d between the tip of the rotor blades of either of rotors 204a or 204b and inner surface 202 is between about 0,5” and 5”, such as around 2”. less than 2”, or less than 1”.

[0035] According to some embodiments, one or more cavities 211 may be present between inner surface 202 and outer surface 203 of duct 102. In an example, an annular cavity wraps entirely or partially around inner surface 202. One or more cavities 211 may be designed to house any number of electrical or mechanical components. For example, one or more cavities211 may include each of a first generator 210a coupled to first rotor 204a and a second generator 210b coupled to second rotor 204b. Other mechanical components may be present as well within one or more cavities 211, such as any number of gear boxes, differentials, or centrifugal clutches.

[0036] In some embodiments, one or more cavities 211 include any number of ballast tanks212 that can be filled with air or water to affect the overall buoyancy of duct 102, For example, depending on the number of ballast tanks 212 that are filled with air or water, the buoyancy of duct 102 can be changed such that duct 102 floats just below the surface of the water or at any other desired level below the water’s surface. In some embodiments, any of ballast tanks 212 can be filled with water to cause duct 102 to tip forwards or backwards, thus causing the entire duct 102 to flip 180 degrees in the water consequently reversing the orientation of duct 102 along the direction of the water flow. In some embodiments, any of ballast tanks 212 can be filled with water to adjust the location of duct 102 to any position within the water column below the surface. Ballast tanks 212 can also be used to control the angle of duct 102 to the flow of water. For example, ba llast tanks 212 can adjust the angle of duct 102 to + / - 10 degrees of horizontal. Ballast tanks 212 can also be adjusted to compensate for changes in water density, for example, due to changes in salinity or temperature.

[0037] Figure 4A illustrates a three-dimensional view of swivel structure 114 that may be coupled to yoke 112 as shown in Figure 1. Swivel stmcture 114 may have a length between about 8 inches and about 20 inches, and a width (e.g., greatest diameter) between about 4 inches arid about 10 inches. According to some embodiments, swivel structure 114 includes a housing 402 with a substantially cylindrical shape, although other shapes could be used as well. Housing402 may include a first mounting plate 404a coupled to an outside surface of the housing and a first connector 405a on first mounting plate 404a. A similar second mounting plate 404b and connector 405b are also coupled to the opposite side of housing 402 from first mounting plate 404a. According to some embodiments, yoke 112 couples to connectors 405a and 405b on either side of housing 402 to allow swivel structure 114 to rotate freely about second axis B passing through both connectors 405a and 405b.

[0038] According to some embodiments, swivel structure 114 includes a first port 406 configured to couple with a first electrical cable and a second port 408 configured to couple with a second electrical cable. First port 406 may be generally located on a top surface or near a top surface of housing 402 to interfa ce with one or more electrical cables from hydrokinetic system 100. Second port 408 may be coupled to a shaft 410 that extends out from a distal end of housing 402 and is designed to freely rotate about a third axis C passing longitudinally through swivel structure 114. Third axis C may be substantially perpendicular to second axis B. According to some embodiments, a distal end of shaft 410 inc ludes a loop 412 for coupling to an anchor cable or similar anchoring structure.

[0039] Figure 4B illustrates an exploded view of swivel structure 114 to visualize the various components, according to some embodiments. Housing 402 may include three segments, such as a central housing portion 402a, an upper housing portion 402b, and a lower housing portion 402c. Each of upper housing portion 402b and lower housing portion 402c may be fastened to opposite top and bottom surfaces of central housing portion 402a. According to some embodiments, swivel structure 114 includes a slip ring 414 to provide a rotatably conductive path between fust port 406 and second port 408 via shaft 410. As such, slip ling 414 may be coupled directly to shaft 410 such that both slip ring 414 and shaft 410 are free to rotate about third axis C within housing 402, and with respect to housing 402. One or more bearings 416 may be provided within housing 402 to facilitate the free rotation of shaft 410 and slip ring 414. Bearings 416 may be taper roller bearings. Any number of other fasteners, washers, nuts, o- rings, etc., may be used to connect any of the elements of swivel structure 114. Using this arrangement, electrical current may be delivered between first port 406 and second port 408 regardless of the rotational dir ection of second port 408. Furthermore, a second elec trical cable coupled to second port 408 can maintain its connected position regardless of the orientation of hydrokinetic system 100. Each of first port 406 and second port 408 are designed for use underwater and thus may be watertight. In some examples, fir st port 406 and second port 408 are each Aquamouse subsea connectors from Glenair (Glendale, CA).

[0040] Figure 5 illustrates a side view of yoke 112 being able to rotate freely about an axis passing through duct 102. As discussed above, yoke 112 may be coupled to a slidable camagell 0 that can move longitudinally along track 108. Yoke is also free io rotate about an axis passing through slidable carriage 110 (e.g., into and out of the page) to adjust for any changes in the water current or for any other reason. Swivel structure 114 may be coupled to an end of yoke 112 away fr om duct 102. It should be noted that duct 102 is also a freely rotatable body when underwater, such that duct 102 can also rotate about the axis passing through slidable camage 110 while yoke 112 remains substantially at the same angle (e.g.. tethered to an anchor).[00411 Figure 6 illustrates an example hydrokinetic electrical system that includes hydrokinetic system 100 producing electrical energy based on the movement of water through the system, and a power control station 602 that receives the electrical energy produced by hydrokinetic system 100. According to some embodiments, hydrokinetic system 100 is anchored to an underwater floor 604 beneath the water’s surface 606. One or more anchor cables 608 may be coupled between a distal end of swivel structure 114 (e.g., through a loop) and an anchor 610 embedded partially or fully witliin floor 604. It should be noted that anchor 610 may also be embedded within a vertical structure or wail structure beneath the water’s surface 606, or on the underside of a floating structure, such as on the underside of a floating iceberg or a floating platform.

[0042] According to some embodiments, one or more first cables 611 may be coupled between the generators onboard hydrokinetic system 100 and the fir st port of swivel structure 114. According to some embodiments, one or more second cables 612 are fed from the second port of swivel structure 114 to a power control station 602. One or more second cables 612 may include both power cables to provide electrical power generated from one or more generators on hydrokinetic system 100 and / or control / sensor cables that provide power and control signals to various sensors and / or controllers on hydrokinetic system 100. Pow'er control station 602 may be located generally anywhere above the water’s surface 606, such as on land, on a floating platform, or on a boat.

[0043] According to some embodiments, power control station 602 provides a user interface for the operations of hydrokinetic system 100. According to some embodiments, power control station 602 also functions to receive, store and distribute the electrical power coining from hydrokinetic system 100 via the one or more underwater cables 612. Power control station 602 may also collect information from various sensors monitoring environmental, mechanical and electr ical data such as ocean currents, revolutions per minute of each rotor and electrical output via the one or more underwater cables 612. In some embodiments, operators can monitor and operate hydrokinetic system 100 either from one or more terminals direcfly onsite (e.g., in power control station 602) or remotely through a computing device 614 and a wireless connection such as cellular, WIFI, 4G, 5G, or Bluetooth.

[0044] According to some embodiments, power control station 602 includes any number of power converters to convert electrical energy between AC and DC power. For example, some of the power converters may be used to convert the AC power received from hydrokinetic system 100 into DC power for storing in one or more storage devices (e.g., batteries). In another example, some of the power converters may be used to convert the DC power stored in the one or more storage devices back into AC power before being distributed onto an electrical grid or directly to a customer. Such power converters that convert from DC power to AC power are sometimes referred to as inverters. According to some embodiments, power control station 602 includes one or more batery chargers that may be designed to receive DC power from the power converters and charge one or more storage devices using the received DC power. The charging protocol depends on the type and size of the storage devices being charged .

[0045] According to some embodiments, power control station 602 includes one or more computing devices with a touchscreen display or any other type of user interface to allow an operator to monitor the health of one or more components of hydrokinetic system 100. The interface may include an emergency or manual braking function to slow7or stop the rotation of any of the rotors within hydrokinetic system 100. In some embodiments, an operator may be alerted if any alarms are set off, such as for an overheating generator, a brake failure, an electrical failure, a rotor failure, etc. Diagnostic details collected from a variety of sensors or controllers may be provided via the touchscreen display or other type of user interface. Such sensors / controllei s may include acoustic sensors, vibration sensors, brake condition sensors to monitor a condition of the rotor brakes, a batery monitor to provide diagnostic information about the storage devices such as charging rate, charging current, and batery voltage, a battery controller to protect the storage devices from overcharging and control charging rates, and an acoustic Doppler current profiler sensor to anticipate maximum and minimum potential current values, to name a few examples.

[0046] Numerous specific details have been set forth herein to provide a thorough understanding of the embodiments. It will be appreciated, however, that the embodiments may be practiced without these specific details. In other instances, well known operations, components and circuits have not been described in detail so as not to obscure the embodiments. It can be further appreciated that the specific structural and functional details disclosed herein may be representative and do not necessarily limit the scope of the embodiments. In addition, although the subject matter has been described in language specific to structural features and / or methodological acts, it is to be understood that the subject matter defined in the appended claims is not necessarily limited to the specific features or acts described herein. Rather , the specific features and acts described herein are disclosed as example forms of implementing the claims.

Claims

What is claimed is:

1. A hydrokinetic system, comprising: a duct having an interior surface defining a central passageway and an exterior surface, the duct being substantially circular in cross-section, wherein the central passageway has a first diameter and the duct further includes a fir st opening with a second diameter and a second opening with a third diameter, the second and third diameters both being greater than the first diameter: one or more rotors suspended within the duct via one or more struts coupled to the one or more rotors; a first slidable carriage on the exterior surface of the duct, the first slidable carriage configured to laterally slide along a longitudinal direction of the duct; a second slidable carriage on the exterior surface of the duct opposite from the first slidable carriage, the second slidable carriage configured to laterally slide along the longitudinal direction of the duct; and a yoke coupled between the first slidable carriage and the second slidable carriage, the yoke being configured to rotate about an axis passing through the first slidable carriage and the second slidable carriage.

2. The hydrokinetic system of claim 1, further comprising a swivel structure coupled to the yoke, such that the yoke attaches to the swivel structure on opposite sides of the swivel structure, and wherein the swivel structure is configured to rotate about an axis passing through the yoke at the opposite sides of the swivel structure,3. The hydrokinetic system of claim 2, wherein the swivel structure comprises a loop at a bottom end of the swivel structure.

4. The hydrokinetic system of claim 3, further comprising an anchor and an anchor cable, wherein the anchor cable extends between the anchor and the loop at the bottom end of the swivel structure.

5. The hydrokinetic system of claim 2, wherein the swi vel structure comprises a first port on a top end of the swivel structure and a second port at or near a bottom end of the swivel structure,6. The hydrokinetic system of claim 5, wherein one or more first electrical cables are coupled to the first port and one or more second electrical cables are coupled to the second port.The hydrokinetic system of claim 6, wherein the one or more first electrical cables are coupled between the first port and one or more generators in the duct.

8. The hydrokinetic system of claim 6, wherein the one or more second electr ical cables are coupled between the second port and one or more power control stations.

9. The hydrokinetic system of claim 8, wherein the one or more power control stations are positioned on land and the duct is positioned under the surface of a body of water.

10. The hydrokinetic system of claim 6, wherein the swivel structure comprises a slip ring configured to transfer electrical signals between the one or more first electrical cables and the one or more second electrical cables.

11. The hydrokinetic system of claim 1, wherein the first diameter of the central passageway is at a midpoint between the first opening and the second opening and the first diameter is a smallest diameter within the central passageway.

12. The hydrokinetic system of claim 1, wherein a diameter of the interior surface of the duct increases parabolically between the first diameter and the second diameter and between the first diameter and the third diameter.

13. The hydrokinetic system of claim 1, wherein the exterior surfa ce of the duct has substantially straight walls along its length between the first opening and the second opening.

14. The hydrokinetic system of claim 1, further comprising a compartment between the interior surface and the exterior surface of the duct.

15. The hydrokinetic system of claim 14, further comprising one or more ballast tanks positioned in the compartment, wherein the one or more ballast tanks are independently operable.

16. The hydrokinetic system of claim 14. further comprising one or more generators positioned in the compartment.

17. The hydrokinetic system of claim 1, further comprising a first track coupled to the exterior surface of the duct, wherein the first slidable carriage is configured to slide along the first tra ck, and a second track coupled to the exterior sur face of the duct, wherein the second slidable carriage is configmed to slide along the second track.

18. A swivel mechanism, comprising:a housing; a first mounting plate coupled to the housing and having a first connector configured to interface with a first rod; a second mounting plate coupled to the housing opposite from the first mounting plate and having a second connector configured to interface with a second rod, wherein the housing is configured to rotate about a first axis passing through the first connector and the second connector; and a slip ring within the housing arid configured to rotate relative to the housing about a second axis passing longitudinally along a greatest dimension of the housing.

19. The swivel mechanism of claim 18, wherein the housing has a substantially cylindrical shape.

20. The swivel mechanism of claim 18, further comprising a shaft within the housing and coupled to the slip ring.

21. The swivel mechanism of claim 20, further comprising one or more bearings coupled to the shaft, such that the shaft is configured to rotate about the second axis relative to the housing.

22. The swivel mechanism of claim 20, wherein the slip ring is arranged bet ween the shaft and a port on or near a top surface of the housing.

23. The swivel mechanism of c laim 22, wherein the port is a first port, and the swivel mechanism further comprises a second port coupled to the shaft.

24. The swivel mechanism of claim 23, wherein the first port is configured to couple to a first electrical cable and the second port is configured to couple to a second electrical cable.

25. The swivel mechanism of claim 23, wherein both the first port and the second port comprise a water-tight seal.

26. The swivel mechanism of claim 20, further comprising a loop coupled to a distal end of the shaft.

27. The swivel mechanism of claim 18, wherein the second axis is substantially perpendicular to the first axis.

28. A hydrokinetic system, comprisinga duct configured for placement within a body of water, the duct comprising at least one rotor coupled to at least one electrical generator; a yoke coupled to the duct and configured to rotate about a first axis passing through the duct; and a swivel mechanism coupled to the yoke at a first connection and a second connection on sides of the swivel mechanism, the swivel mechanism configured to rotate about a second axis passing through the first connection and the second connection, the swivel mechanism having a first port and a second port, wherein the swivel mechanism comprises a slip ring configured to provide a rotatable conductive path between the fir st port and the second port.

29. The hydrokiiietic system of claim 28, further comprising: a first electrical cable coupled between the at least one electrical gener ator and the fir st port of the swivel mechanism; and a second electrical cable coupled between the second port of the swivel mechanism and one or more power control stations.

30. The hydrokinetic system of claim 29. wherein the one or more power control stations are positioned on land.

31. The hydrokinetic system of claim 28, wherein the slip ring is coupled to a shaft within the swivel mechanism, the slip ring and shaft being configured to rotate about a third axis passing longitudinally through the swivel mechanism.

32. The hydrokinetic system of claim 31 , further comprising a loop coupled to a distal end of the shaft.

33. The hydrokinetic system of claim 28. wherein both the first port and the second port comprise a water-tight seal.

34. The hydrokinetic system of claim 28. wherein the yoke is coupled to a first slidable carriage on a first side of the duct and is coupled to a second slidable camage on a second side of the duct.

35. The hydrokinetic system of claim 28, wherein the duct compr ises one or more ballast tanks.

36. The hydrokinetic system of claim 28, wherein the first axis is substantially parallel to the second axis.

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