Patent Description:
Unmanned underwater vehicles (UUVs) can be used in a number of applications, such as undersea surveying, recovery, or surveillance operations. However, supplying adequate power to UUVs for prolonged operation can be problematic. For example, one prior approach simply tethers a UUV to a central power plant and supplies power to the UUV through the tether. However, this clearly limits the UUV's range and deployment, and it can prevent the UUV from being used in situations requiring independent or autonomous operation. Another prior approach involves using fuel cells in a UUV to generate power, but fuel cells typically require large packages and substantial space.

<CIT> discloses a system and method for free-piston power generation based on thermal differences. The apparatus includes a generator configured to generate electrical power. The apparatus also includes first and second tanks each configured to receive and store a refrigerant under pressure. The apparatus further includes a first piston assembly having a first piston that divides a volume within the first piston assembly into first and second spaces each configured to receive refrigerant from at least one of the tanks. In addition, the apparatus includes a second piston assembly having a second piston coupled to the first piston. The generator is configured to generate the electrical power based on movement of at least one of the first and second pistons. During use, flows of the refrigerant between the tanks and the spaces can be created based on a pressure differential, such as a pressure differential created by a temperature difference between the tanks.

This disclosure provides a tactical maneuvering ocean thermal energy conversion buoy for ocean activity surveillance.

According to a first aspect of the invention, a system for use in an underwater vehicle includes a first jacket comprising first and second ports; a first tank configured to store a first fluid under pressure, the first jacket being configured to contain water and the first tank; a second jacket comprising third and fourth ports; a second tank configured to store a second fluid under pressure, the second jacket being configured to contain water and the second tank; a pump configured to cause water to move between the first jacket and the second jacket; an actuator cylinder defining a space configured to receive the first fluid from the first tank and the second fluid from the second tank, the actuator cylinder comprising an actuator piston that divides the space into a first volume for the first fluid and a second volume for the second fluid; a hydraulic cylinder defining a space configured to receive a hydraulic fluid, the hydraulic cylinder comprising a hydraulic piston configured to move and change an amount of the hydraulic fluid in the hydraulic cylinder, wherein the hydraulic piston is fixedly coupled to the actuator piston; and a buoyancy plug configured to change a position inward or outward with respect to a body of a vehicle in connection with the amount of the hydraulic fluid in the hydraulic cylinder, wherein movements of the buoyancy plug are fluidly coupled to movements of the actuator and hydraulic pistons, and wherein the position of the buoyancy plug affects a buoyancy of the vehicle.

According to a second aspect of the invention, an underwater vehicle comprising: a body; and a buoyancy engine comprising: a first jacket comprising first and second ports; a first tank configured to store a first fluid under pressure, the first jacket being configured to contain water and the first tank; a second jacket comprising third and fourth ports; a second tank configured to store a second fluid under pressure, the second jacket being configured to contain water and the second tank; a pump configured to cause water to move between the first jacket and the second jacket; an actuator cylinder defining a space configured to receive the first fluid from the first tank and the second fluid from the second tank, the actuator cylinder comprising an actuator piston that divides the space into a first volume for the first fluid and a second volume for the second fluid; a hydraulic cylinder defining a space configured to receive a hydraulic fluid, the hydraulic cylinder comprising a hydraulic piston configured to move and change an amount of the hydraulic fluid in the hydraulic cylinder, wherein the hydraulic piston is fixedly coupled to the actuator piston; and a buoyancy plug configured to change a position inward or outward with respect to the body of the vehicle in connection with the amount of the hydraulic fluid in the hydraulic cylinder, wherein movements of the buoyancy plug are fluidly coupled to movements of the actuator and hydraulic pistons, and wherein the position of the buoyancy plug affects a buoyancy of the vehicle.

According to a third aspect of the invention, a method comprising: creating a flow of a first fluid between a first tank and an actuator cylinder and a flow of a second fluid between a second tank and the actuator cylinder, wherein the first tank is disposed in a first jacket that contains water and the second tank is disposed in a second jacket that contains water, wherein the first fluid is stored under pressure in the first tank and the second fluid is stored under pressure in the second tank, wherein the actuator cylinder defines a space configured to receive the first fluid from the first tank and the second fluid from the second tank; operating a pump to cause water to move between the first jacket and the second jacket; moving an actuator piston disposed within the actuator cylinder and a hydraulic piston disposed in a hydraulic cylinder, wherein the hydraulic piston is fixedly coupled to the actuator piston, wherein movement of the hydraulic piston changes an amount of hydraulic fluid in the hydraulic cylinder; and changing a position of a buoyancy plug inward or outward with respect to a body of an underwater vehicle in connection with the amount of the hydraulic fluid in the hydraulic cylinder, wherein movements of the buoyancy plug are fluidly coupled to movements of the actuator and hydraulic pistons, and wherein the position of the buoyancy plug affects a buoyancy of the vehicle.

For a more complete understanding of this disclosure, reference is made to the following description, taken in conjunction with the accompanying drawings, in which:.

The figures described below and the various embodiments used to describe the principles of the present invention in this patent document are by way of illustration only and should not be construed in any way to limit the scope of the invention as defined by the appended claims. Those skilled in the art will understand that the principles of the present invention may be implemented in any type of suitably arranged device or system.

For simplicity and clarity, some features and components are not explicitly shown in every figure, including those illustrated in connection with other figures. It will be understood that all features illustrated in the figures may be employed in any of the embodiments described. Omission of a feature or component from a particular figure is for purposes of simplicity and clarity, and is not meant to imply that the feature or component cannot be employed in the embodiments described in connection with that figure.

It will be understood that embodiments of this disclosure may include any one, more than one, or all of the features described here. Also, embodiments of this disclosure may additionally or alternatively include other features not listed here. While the disclosed embodiments may be described with respect to underwater vehicles, these embodiments are also applicable in any other suitable systems or applications.

Vertical diving buoys with fast dives and more periodic dives require more energy than the slower gliders and drifting buoys which take <NUM>-<NUM> days per dive. Such a drifting buoy floats and drifts in ocean currents, navigating for days in the currents at very low speed, remaining at current depths, and not likely to match up with sound channels for surveillance mission operations. Relatively static vertical position at current depth means the buoy does not cross the sound channel very frequently.

In contrast, the embodiments described in this disclosure provide a buoy that performs more periodic dives (e.g., <NUM>-<NUM> dives per hour) with much more frequent diversity sampling of the ocean sound channel, which provides an clear advantage. This advantage is even more substantial when energy is extracted from the ocean, rather than carried within the buoy. Energy extraction from the ocean is based on thermal differences between ocean water at or near the surface (at a temperature of, e.g., <NUM>-<NUM> degrees C) and ocean water at depths greater than <NUM>-<NUM> (at a temperature of, e.g., <NUM>-<NUM> degrees C). The problem of endurance is solved by using a conversion technique that is more efficient than extracting the energy and storing it in batteries for future dive buoyancy engine needs.

The duality of energy extraction with fast, low thermal loss dives and the much more frequent crossing of the sound channel solves problems of energy use, and allows for autonomous operation and higher mobility, as the buoy uses the vertical speed component to spend less time in diverse currents. The disclosed buoy requires no electrical power storage to operate the buoyancy engine. The disclosed buoyancy engine does not exhibit any of the loss mechanisms that are present in power systems, such as friction at the seals of a hydraulic pump, duct losses from small hydraulic lines, valve losses, and other factors related to electrical power conversion losses.

<FIG> illustrate an example underwater vehicle <NUM> configured to operate using ocean thermal energy conversion according to this disclosure. In this example, the vehicle <NUM> denotes an unmanned underwater vehicle or other device that can function as both a buoy and a glider within an ocean or other body of water. As discussed in greater detail below, the vehicle <NUM> uses ocean thermal energy conversion with a hydraulic and carbon dioxide (CO<NUM>) hybrid configuration that can be packaged into a long vertical buoy. The vehicle <NUM> could be used to support various functions, such as undersea surveying, recovery, or surveillance operations.

The vehicle <NUM> is configured to dive to ocean depths greater than <NUM> meters once every <NUM>-<NUM> hours and return to the surface or a shallow depth, transporting through ocean sound channels, which can be monitored as the vehicle <NUM> passes through <NUM> to <NUM> times a day, thereby making the vehicle <NUM> an advantageous acoustic surveillance vessel.

As shown in <FIG>, the vehicle <NUM> includes a body <NUM> having fins 104a-104b disposed near ends of the body <NUM>. The body <NUM> is elongate and is oriented for vertical or substantially vertical travel within an ocean or other body of water. In some embodiments, the body <NUM> has an overall length of approximately <NUM>-<NUM> meters (<NUM>-<NUM> feet) and a diameter of approximately <NUM> centimetres (<NUM> inches). Of course, this is merely one example, and the body <NUM> could have larger or smaller dimensions.

The body <NUM> denotes any suitable structure configured to encase, protect, or otherwise contain other components of the vehicle <NUM>. The body <NUM> could be formed from any suitable material(s) and in any suitable manner. The body <NUM> can be formed so that the vehicle <NUM> is able to withstand extremely elevated pressures found at deep depths in an ocean or other body of water. In some embodiments, the body <NUM> could allow the vehicle <NUM> to operate at depths of up to <NUM>,<NUM> meters or more.

The fins 104a-104b denote projections from the body <NUM> that help to stabilize the body <NUM> during travel. Each of the fins 104a-104b could be formed from any suitable material(s) and in any suitable manner. Also, each of the fins 104a-104b could have any suitable size, shape, and dimensions. Further, at least some of the fins 104a-104b could be movable or adjustable to help alter the course of the body <NUM> and to steer the body <NUM> through water during travel. In addition, the numbers and positions of the fins 104a-104b shown here are examples only, and any numbers and positions of fins could be used to support desired operations of the vehicle <NUM>. For example, in embodiments where the vehicle <NUM> operates primarily at the surface of the water, the vehicle <NUM> may include only the bottom fins 104b (the top fins 104a may be omitted).

As described below, the underwater vehicle <NUM> can both ascend and descend within a body of water during use. In some embodiments, the fins 104a could be used to steer the vehicle <NUM> while ascending, and the fins 104b could be used to steer the vehicle <NUM> while descending. Moreover, when the vehicle <NUM> is ascending, the fins 104a can be used to control the pitch of the vehicle <NUM>, and a differential between the fins 104a can be used to control the roll of the vehicle <NUM>. Similarly, when the vehicle <NUM> is descending, the fins 104b can be used to control the pitch of the vehicle <NUM>, and a differential between the fins 104b can be used to control the roll of the vehicle <NUM>. Orientation or shape of the fins 104a-104b can be selected to steer the vehicle <NUM> in a direction that includes a horizontal component as well as a vertical component. That is, the vehicle <NUM> can travel laterally over time, as well as up and down.

Multiple ports <NUM> are disposed on exterior surfaces of the vehicle <NUM>. As described in greater detail with respect to <FIG> below, the ports <NUM> allow seawater to enter into, or be discharged from, one or more compartments or cavities (referred to herein as jackets) internal to the vehicle <NUM>. The ports <NUM> are generally low energy, low power (e.g., 12V 1A) ports that are capable of opening or closing in approximately <NUM> seconds. In some embodiments, the ports <NUM> are located on opposite sides of the vehicle <NUM> along a length of the vehicle <NUM>. Each port <NUM> includes any suitable structure configured to allow seawater to enter or exit internal portions of the vehicle <NUM>. Each of the ports <NUM> could be formed from any suitable material(s) and in any suitable manner. Also, each of the ports <NUM> could have any suitable size, shape, and dimensions. Note that the number and positions of the ports <NUM> shown here are examples only, and any number and positions of ports could be used in the vehicle <NUM>.

A buoyancy plug <NUM> is disposed at the bottom end of the vehicle <NUM>. The buoyancy plug <NUM> is a rigid or flexible structure that alternatively extends or expands from surrounding portions of the vehicle <NUM> or contracts to be substantially flush with surrounding portions of the vehicle <NUM>. The position of the buoyancy plug <NUM> affects the overall volume and buoyancy of the vehicle, which, in turn, controls the dive operation of the vehicle <NUM>. In its extended position, the buoyancy plug <NUM> causes the vehicle <NUM> to have an overall larger volume or water displacement, thus causing the vehicle <NUM> to be more buoyant and to rise or float in seawater. In its contracted position, the buoyancy plug <NUM> causes the vehicle <NUM> to have an overall smaller volume or water displacement, thus causing the vehicle <NUM> to sink in seawater. The buoyancy plug <NUM> includes any suitable structure configured to vary in shape or position to affect the overall volume of the vehicle <NUM>. In some embodiments, the buoyancy plug <NUM> is a rigid cylindrical plug that slides outward and inward with respect to the body <NUM> of the vehicle <NUM>. In other embodiments, the buoyancy plug <NUM> is a flexible bladder or diaphragm that expands outward and contracts inward with respect to the body <NUM> of the vehicle <NUM>.

In some embodiments, the vehicle <NUM> can include an optional solar mast <NUM> at (or extending from) the top surface of the vehicle <NUM>. The solar mast <NUM> can include one or more solar panels for additional energy generation. This could provide auxiliary power for operation of one or more components of the vehicle <NUM>, such as one or more of the ports <NUM>, a communication system, or one or more motors to control orientation of one or more fins 104a-104b.

<FIG> shows additional details of the vehicle <NUM> of <FIG> according to this disclosure. In particular, <FIG> is a cross-section view of the vehicle <NUM>, and illustrates components that are disposed internally in the vehicle <NUM>. The view of the vehicle <NUM> in <FIG> is split vertically into a top portion <NUM> and a bottom portion <NUM> in order to more clearly show each component on the page. The bottom portion <NUM> of the view extends the view below the top portion <NUM>. To illustrate continuity of parts, some components of the vehicle <NUM> are shown in both portions <NUM>, <NUM>.

As shown in <FIG>, the vehicle <NUM> includes an energy conversion system (or buoyancy engine) that includes ports 106a-106d (which represent different ones of the ports <NUM> in <FIG>), the buoyancy plug <NUM>, a top jacket <NUM>, a bottom jacket <NUM>, a top tank <NUM>, a bottom tank <NUM>, a pump <NUM>, an actuator cylinder <NUM>, a hydraulic cylinder <NUM>, hydraulic fluid <NUM>, a fluid reservoir <NUM>, a hydraulic valve <NUM>, a hydraulic line <NUM>, a connecting rod <NUM>, a first fluid line <NUM>, a second fluid line <NUM>, crossover valves <NUM>, an actuator piston <NUM>, and a hydraulic piston <NUM>.

The top jacket <NUM> and bottom jacket <NUM> are chambers disposed at or near the top of the vehicle <NUM> and are configured to hold seawater that enters or exits through the ports 106a-106d. Each jacket <NUM>-<NUM> can contain warm, cool, or cold seawater, depending on where the vehicle <NUM> is in a dive cycle. Over the course of one dive cycle (both descent and ascent), each jacket <NUM>-<NUM> will exchange warm water for cold water or vice versa. The pump <NUM>, which is a low power pump, can operate in either direction to move water from the top jacket <NUM> to the bottom jacket <NUM> or vice versa. Each jacket <NUM>-<NUM> includes any suitable structure configured to hold seawater at different temperatures. Each jacket <NUM>-<NUM> can include insulated walls to minimize unwanted transfer of thermal energy into or out of each jacket <NUM>-<NUM>.

The top jacket <NUM> contains the top tank <NUM>, and the bottom jacket <NUM> contains the bottom tank <NUM>. Each tank <NUM>-<NUM> is configured to hold liquid and gas CO<NUM> at high pressures (e.g., greater than <NUM> psi). The CO<NUM> in each tank <NUM>-<NUM> is alternatively warmed and cooled (via conductive heat transfer through the walls of the tank <NUM>-<NUM>) by the water held in the corresponding jacket <NUM>-<NUM>. Over the course of one dive cycle, each tank <NUM>-<NUM> is exposed to water at varying temperatures. The warming and cooling of the CO<NUM> in each tank <NUM>-<NUM> cause pressure differences that result in movement of the actuator cylinder <NUM> and the hydraulic cylinder <NUM>, as described in greater detail below.

The actuator cylinder <NUM> generally defines a space in which liquid CO<NUM> from the tanks <NUM>-<NUM> can enter and exit. The actuator cylinder <NUM> includes an actuator piston <NUM>, which separates the internal space in the actuator cylinder <NUM> into two volumes filled with the CO<NUM> from the tanks <NUM>-<NUM>. The actuator cylinder <NUM> is fluidly coupled to the top tank <NUM> via the first fluid line <NUM>, and is fluidly coupled to the bottom tank <NUM> via the second fluid line <NUM>. Each fluid line <NUM>-<NUM> includes any suitable passageway configured to allow transport of CO<NUM> between a tank and a cylinder. The crossover valves <NUM> can be used to open and close the flow of CO<NUM> within the fluid lines <NUM>-<NUM>.

Liquid CO<NUM> can flow into and out of the top tank <NUM> and into and out of a first portion of the actuator cylinder <NUM>. Similarly, liquid CO<NUM> can flow into and out of the bottom tank <NUM> and into and out of a second portion of the actuator cylinder <NUM>. Differences in CO<NUM> pressure between the tanks <NUM>-<NUM> (which may be caused by thermal differences) can determine whether the CO<NUM> flows into the top tank <NUM> or the first portion of the actuator cylinder <NUM> and whether the CO<NUM> flows into the bottom tank <NUM> or the second portion of the actuator cylinder <NUM>. The actuator cylinder <NUM> includes any suitable structure defining a space configured to receive CO<NUM> from multiple tanks. Note that the actuator cylinder <NUM> may have any suitable shape and may or may not have a circular cross-section.

The hydraulic cylinder <NUM> generally defines a space in which the hydraulic fluid <NUM> can enter from the fluid reservoir <NUM> or exit to the fluid reservoir <NUM> through the hydraulic line <NUM>. The hydraulic valve <NUM> can open or close to allow or restrict the flow of the hydraulic fluid <NUM> between the hydraulic cylinder <NUM> and the fluid reservoir <NUM>. The hydraulic cylinder <NUM> includes a hydraulic piston <NUM> that defines the internal space occupied by the hydraulic fluid <NUM>. The hydraulic piston <NUM> is fixedly coupled to the actuator piston <NUM> by the connecting rod <NUM>, such that the pistons <NUM>-<NUM> and the connecting rod <NUM> move together.

The fluid reservoir <NUM> generally defines a space in which the hydraulic fluid <NUM> can be stored. The internal volume of the fluid reservoir <NUM> is determined by the position of the buoyancy plug <NUM>, which is configured to move laterally in and out the fluid reservoir <NUM>. Pressure differences between the hydraulic fluid <NUM> and the external sea water can cause the buoyancy plug <NUM> to move in or out, thereby changing the volume of the fluid reservoir <NUM>. Since the total amount of hydraulic fluid <NUM> within the hydraulic cylinder <NUM>, the hydraulic line <NUM> and the fluid reservoir <NUM> is constant, movements of the pistons <NUM>-<NUM> and the buoyancy plug <NUM> are fluidly coupled and are essentially simultaneous.

In one aspect of operation, during different portions of a dive cycle, the vehicle <NUM> alternately vents or receives warmer or colder water through the ports 106a-106d. Changes in temperature in the water result in changes in temperature in the CO<NUM> in each tank <NUM>-<NUM>. The CO<NUM> temperature changes create a pressure difference in the hydraulic cylinder <NUM>, which moves the connected pistons <NUM>-<NUM>, pushing hydraulic fluid <NUM> into the fluid reservoir <NUM> or removing hydraulic fluid <NUM> from the fluid reservoir <NUM>. This affects the position of the buoyancy plug <NUM>, thereby creating positive or negative buoyancy. Further details regarding the operation of the vehicle <NUM> during a dive will now be provided with respect to <FIG> and <FIG>.

<FIG> illustrate operations and configurations of the vehicle <NUM> during one dive cycle according to this disclosure. Corresponding positions of the vehicle <NUM> during the dive cycle are shown in <FIG>.

As shown in <FIG>, and with respect to position #<NUM> in <FIG>, the vehicle <NUM> is at the surface of the water prior to a dive. At this point, the vehicle <NUM> has recently been deployed on the water surface or has ascended from a previous dive. The buoyancy plug <NUM> is extended outward from the body <NUM> of the vehicle <NUM>, which maximizes the overall volume of the vehicle <NUM>, thereby resulting in greatest buoyancy. The hydraulic valve <NUM> is closed, thus maintaining the buoyancy plug <NUM> in its extended position.

Warm CO<NUM> in the actuator cylinder <NUM> from the previous dive has started to cool off. The fluid temperatures in the top jacket <NUM> and the top tank <NUM> are warmer than the fluid temperatures in the bottom jacket <NUM> and the bottom tank <NUM>. The relatively colder water in the bottom jacket <NUM> was carried from the bottom of the previous dive and remains relatively cold. The relatively colder CO<NUM> in the bottom tank <NUM> is at a relatively low CO<NUM> pressure. The ports 106a-106d are closed.

As shown in <FIG>, and with respect to position #<NUM> in <FIG>, the vehicle <NUM> is still at the water surface. The port 106a of the top jacket <NUM> opens, and the port 106d of the bottom jacket <NUM> opens. The pump <NUM> operates to transfer colder water from the bottom jacket <NUM> to the top jacket <NUM>. The transfer of water from the bottom jacket <NUM> to the top jacket <NUM> causes warm seawater at the surface (e.g., <NUM>-<NUM> degrees C) to enter the bottom jacket <NUM> through the port 106d, and causes warm water to vent out of the top jacket <NUM> through the port 106a. The operation of the pump <NUM> is a timed operation. At the end of the pump operation, the top jacket <NUM> has most of the cold seawater that was previously contained in the bottom jacket <NUM>. When the pump <NUM> times out, the port 106c on the bottom jacket <NUM> opens to induce thermal gravity flow, as described with respect to <FIG>.

As shown in <FIG>, and with respect to position #<NUM> in <FIG>, the vehicle <NUM> begins to descend from the water surface. Both ports 106c-106d of the bottom jacket <NUM> are now open, and the pump <NUM> is off. This configuration allows a gravity density feed to operate by induction. The top tank <NUM> cools and the bottom tank <NUM> warms up as fresh surface water flows in through the port 106c. The objective here is that a temperature difference of approximately <NUM> degrees C between the CO<NUM> in the respective tanks <NUM>-<NUM> will produce a pressure difference of approximately <NUM> psi, which is easily capable of moving the buoyancy plug <NUM> against friction and line losses in the hydraulic line <NUM>.

As shown in <FIG>, and with respect to position #<NUM> in <FIG>, the vehicle <NUM> is beginning its dive. The hydraulic valve <NUM> opens, allowing hydraulic fluid <NUM> to flow through the hydraulic line <NUM>, thereby permitting the pistons <NUM>-<NUM> freedom to move. A timed operation of the crossover valves <NUM> causes CO<NUM> to flow through the fluid lines <NUM>-<NUM>. In particular, CO<NUM> flows through the first fluid line <NUM> from the actuator cylinder <NUM> to the top tank <NUM>, and CO<NUM> flows through the second fluid line <NUM> from the bottom tank <NUM> to the actuator cylinder <NUM>. This changes the fluid levels in the actuator cylinder <NUM>, which in turn causes the pistons <NUM>-<NUM> to move inward. When the piston <NUM> moves inward, hydraulic fluid <NUM> is drawn from the fluid reservoir <NUM> into the hydraulic cylinder <NUM>, thereby retracting the buoyancy plug <NUM> for initial descent.

At an intermediate point in time (e.g., after a short period under <NUM> minute), the second fluid line <NUM> closes and the first fluid line <NUM> remains open. The buoyancy plug <NUM> pushes cold CO<NUM> from the actuator cylinder <NUM> back into the top tank <NUM>. The descent of the vehicle <NUM> and the rising water pressure further causes the buoyancy plug <NUM> to retract.

As shown in <FIG>, and with respect to position #<NUM> in <FIG>, the vehicle <NUM> is descending. Increasing water pressure at increasing depths overcome the internal pressure on the buoyancy plug <NUM>, causing the buoyancy plug <NUM> to be completely depressed into the fluid reservoir <NUM>. The vehicle <NUM> increases its speed of descent, eventually reaching a terminal velocity. The depth of the vehicle <NUM> can be measured by seawater pressure, and the descent can be profiled using on-board sensors.

As shown in <FIG>, and with respect to position #<NUM> in <FIG>, the vehicle <NUM> is at or near the bottom of its dive. At some point in the descent profile, it becomes necessary to slow down the vehicle <NUM> to achieve a desired depth. The surrounding seawater temperature can also be profiled using on-board temperature sensors. In some dive operations, it may be desired to reach a seawater temperature of <NUM> degrees C or a maximum depth of <NUM>.

The ports 106a-106b of the top jacket <NUM> may open before the bottom depth is reached to take advantage of mixing flow scavenging into the top jacket <NUM>. At or around that point in time, the hydraulic line <NUM> opens, and then the crossover valves <NUM> open, so that superior differential pressure/force from the warm CO<NUM> in the bottom tank <NUM> to the cold CO<NUM> in the top tank <NUM> overcomes the inward pressure on the buoyancy plug <NUM> at depth.

For example, in an embodiment, the pressure differences in the CO<NUM> in the tanks <NUM>-<NUM> could be approximately <NUM> psi. This causes movement of the pistons <NUM>-<NUM> at <NUM> psi. If the cross-sectional area of the pistons <NUM>-<NUM> is one tenth of the cross-sectional area of the buoyancy plug <NUM>, then mechanical advantage in the hydraulics allows the <NUM> psi CO<NUM> pressure difference to result in <NUM> psi of outward pressure on the buoyancy plug <NUM>, which is more than enough to overcome <NUM> psi seawater pressure at <NUM> depth. For example, a <NUM> movement of the pistons <NUM>-<NUM> at <NUM> psi would result in a <NUM> movement of the buoyancy plug at <NUM> psi. Of course, these numbers are merely one example. Other pressures, dimensions, and ratios are possible and within the scope of this disclosure.

As shown in <FIG>, and with respect to position #<NUM> in <FIG>, the vehicle <NUM> is at the bottom of the dive. At this point, the hydraulics are locked and the fluid lines <NUM>-<NUM> are closed. The ports 106a-106b of the top jacket <NUM> are open in order to cause mixing flow scavenging between the (relatively warmer) water in the top jacket <NUM> and the colder external seawater (which may be, e.g., <NUM>-<NUM> degrees C). In some embodiments, the soak period may be approximately twenty minutes.

As shown in <FIG>, and with respect to position #<NUM> in <FIG>, the vehicle <NUM> is preparing to ascend. At this time, the hydraulic valve <NUM> opens and the fluid lines <NUM>-<NUM> open. Pressure differences between the CO<NUM> in the top tank <NUM> and the CO<NUM> in the bottom tank <NUM> cause CO<NUM> to flow into and out of the actuator cylinder <NUM>, resulting into downward movement of the pistons <NUM>-<NUM> and outward movement of the buoyancy plug <NUM>. In addition, the ports 106a-106b of the top jacket <NUM> may remain open for a short time to continue mixing flow scavenging of cold seawater into the top jacket <NUM>.

As shown in <FIG>, and with respect to position #<NUM> in <FIG>, the vehicle <NUM> is ascending. The buoyancy plug <NUM> is now extending outward for greater buoyancy. At this time, the ports 106a-106b of the top jacket <NUM> close. During the ascent, seawater temperature and pressure can be monitored by on-board sensors.

As shown in <FIG>, and with respect to position #<NUM> in <FIG>, the vehicle <NUM> is ascending. The hydraulic valve <NUM> locks when the buoyancy plug <NUM> is fully extended. The fluid lines <NUM>-<NUM> close. All ports 106a-106d are closed. Seawater temperature and pressure can continue to be monitored.

As shown in <FIG>, and with respect to position #<NUM> in <FIG>, the vehicle <NUM> is at or near the ocean surface. The ports 106a-106b of the top jacket <NUM> can open to take advantage of mixing flow scavenging of warmer seawater into the top jacket <NUM>.

As shown in <FIG>, and with respect to position #<NUM> in <FIG>, the vehicle <NUM> is at or near the ocean surface, prior to a subsequent dive. The ports 106a-106b of the top jacket <NUM> remain open so that the CO<NUM> in the top tank <NUM> warms up from the warm surface seawater flowing into the top jacket <NUM>. The hydraulic valve <NUM> and the fluid lines <NUM>-<NUM> remain closed.

Although <FIG> illustrate an example underwater vehicle <NUM> configured to operate using ocean thermal energy conversion, various changes may be made to <FIG>. For example, the arrangement and relative sizes of the components shown in <FIG> is for illustration only. Various components may not be shown to scale. Also, various components may be placed in any other suitable arrangement. In addition, while the vehicle <NUM> is described as using CO<NUM> as a fluid for generating thermal energy conversion, other fluids could be used.

<FIG> illustrates a chart <NUM> showing lateral distances that the vehicle <NUM> can travel over time while performing dive cycles, according to this disclosure. As shown in <FIG>, the vehicle <NUM> can descend and ascend at an angle that is measured from vertical. The larger the angle, the less vertical the path of the vehicle <NUM> during each descent and ascent of a dive cycle. When the vehicle <NUM> dives at an angle, the vehicle <NUM> necessarily travels laterally while moving up and down. Over time and multiple dives, the vehicle <NUM> can travel a lateral distance of many kilometers. The angle of each descent/ascent during a dive cycle is determined largely by the positions and angular orientations of the fins 104a-104b.

<FIG> illustrates example components of an underwater vehicle <NUM> that operates using ocean thermal energy conversion according to this disclosure. The underwater vehicle <NUM> can, for example, represent the underwater vehicle <NUM> described above. The components shown in <FIG> can therefore represent internal or other components within the vehicle <NUM> that were not shown in other figures.

As shown in <FIG>, the vehicle <NUM> includes at least one controller <NUM> and at least one memory <NUM>. The controller <NUM> controls the overall operation of the vehicle <NUM> and can represent any suitable hardware or combination of hardware and software/firmware for controlling the vehicle <NUM>. For example, the controller <NUM> can represent at least one processor configured to execute instructions obtained from the memory <NUM>. The controller <NUM> may include any suitable number(s) and type(s) of processors or other computing or control devices in any suitable arrangement. Example types of controllers <NUM> include microprocessors, microcontrollers, digital signal processors, field programmable gate arrays, application specific integrated circuits, and discrete circuitry.

The memory <NUM> stores data used, generated, or collected by the controller <NUM> or other components of the vehicle <NUM>. Each memory <NUM> represents any suitable structure(s) configured to store and facilitate retrieval of information (such as data, program code, and/or other suitable information on a temporary or permanent basis). Some examples of the memory <NUM> can include at least one random access memory, read only memory, Flash memory, or any other suitable volatile or non-volatile storage and retrieval device(s).

The vehicle <NUM> in this example also includes one or more sensor components <NUM> and one or more communication interfaces <NUM>. The sensor components <NUM> include sensors that can be used to sense any suitable characteristics of the vehicle <NUM> itself or the environment around the vehicle <NUM>. For example, the sensor components <NUM> can include a position sensor, such as a Global Positioning System (GPS) sensor, which can identify the position of the vehicle <NUM>. This can be used, for instance, to help make sure that the vehicle <NUM> is following a desired path or is maintaining its position at or near a desired location. The sensor components <NUM> can also include pressure sensors or temperature sensors used to estimate a depth of the underwater vehicle <NUM>. The sensor components <NUM> can further include audio sensors for capturing audio signals, photodetectors or other cameras for capturing video signals or photographs, or any other or additional components for capturing any other or additional information. Each sensor component <NUM> includes any suitable structure for sensing one or more characteristics.

The communication interfaces <NUM> support interactions between the vehicle <NUM> and other devices or systems. For example, the communication interfaces <NUM> can include at least one radio frequency (RF) or other transceiver configured to communicate with one or more satellites, airplanes, ships, or other nearby or distant devices. The communication interfaces <NUM> allow the vehicle <NUM> to transmit data to one or more external destinations, such as information associated with data collected by the sensor components <NUM>. The communication interfaces <NUM> also allow the vehicle <NUM> to receive data from one or more external sources, such as instructions for other or additional operations to be performed by the vehicle <NUM> or instructions for controlling where the vehicle <NUM> operates. Each communication interface <NUM> includes any suitable structure(s) supporting communication with the vehicle <NUM>.

The vehicle <NUM> may include one or more device actuators <NUM>, which are used to adjust one or more operational aspects of the vehicle <NUM>. For example, the device actuators <NUM> can be used to move the fins 104a-104b of the vehicle while the vehicle is ascending or descending. As a particular example, the device actuators <NUM> can be used to move the fins 104a-104b during ascent or descent of the vehicle so that the vehicle obtains a desired attitude with respect to the Earth's magnetic field (in order to achieve a desired descent or ascent path). Each device actuator <NUM> includes any suitable structure for physically modifying one or more components of an underwater vehicle. Note, however, that the vehicle <NUM> need not include device actuators <NUM>, such as when the vehicle <NUM> lacks moveable fins.

The vehicle <NUM> further includes a power generator <NUM>, a power conditioner <NUM>, and a power storage <NUM>. The power generator <NUM> generally operates to create electrical energy. The power generator <NUM> includes any suitable structure configured to generate electrical energy based on thermal differences.

The power conditioner <NUM> is configured to condition or convert the power generated by the power generator <NUM> into a suitable form for storage or use. For example, the power conditioner <NUM> can receive a direct current (DC) signal from the power generator <NUM>, filter the DC signal, and store power in the power storage <NUM> based on the DC signal. The power conditioner <NUM> can also receive power from the power storage <NUM> and convert the power into suitable voltage(s) and current(s) for other components of the vehicle <NUM>. The power conditioner <NUM> includes any suitable structure(s) for conditioning or converting electrical power.

The power storage <NUM> is used to store electrical power generated by the power generator <NUM> for later use. The power storage <NUM> represents any suitable structure(s) for storing electrical power, such as one or more batteries or super-capacitors.

The vehicle <NUM> may include one or more propulsion components <NUM>, which represent components used to physically move the vehicle <NUM> in or through water. In some embodiments, the propulsion components <NUM> can represent one or more motors or other propulsion systems. Note, however, that the vehicle <NUM> need not include propulsion components <NUM>, such as when the vehicle <NUM> represents a passive buoy.

Various buses <NUM> can be used to interconnect components of the vehicle <NUM>. For example, a power bus can transport power to various components of the vehicle <NUM>. The power generated by the power generator <NUM> and the power stored in the power storage <NUM> can be supplied to any of the components in <FIG>. For instance, electrical power can be provided to the controller <NUM> and memory <NUM> to facilitate computations and instruction execution by the controller <NUM> and data storage/retrieval by the memory <NUM>. Electrical power can also be provided to the sensor components <NUM>, communication interfaces <NUM>, and device actuators <NUM> in order to support sensing, communication, and actuation operations. In addition, electrical power can be provided to the propulsion components <NUM> in order to support movement of the vehicle <NUM>. The power bus may have a range of voltages and purposes, such as 5V, 12V, and 24V main drive power for servos and other device actuators (such as ballasting). A control bus can transport control signals for various components, such as control signals generated by the controller <NUM>. A sensor bus can transport sensor data for various components.

Although <FIG> illustrates one example of components of an underwater vehicle <NUM> that operates using ocean thermal energy conversion, various changes may be made to <FIG>. For example, various components in <FIG> can be combined, further subdivided, rearranged, or omitted or additional components can be added according to particular needs.

<FIG> illustrates an example method <NUM> for operating an underwater vehicle using ocean thermal energy conversion according to this disclosure. For ease of explanation, the method <NUM> is described with respect to the vehicle <NUM>. However, the method <NUM> could be used in any other suitable device or system.

Prior to step <NUM>, the vehicle <NUM> is at the surface of the water prior to a dive. At step <NUM>, the port 106a of the top jacket <NUM> opens, and the port 106d of the bottom jacket <NUM> opens, and the pump <NUM> operates to transfer colder water from the bottom jacket <NUM> to the top jacket <NUM>. The transfer of water from the bottom jacket <NUM> to the top jacket <NUM> causes warm seawater at the surface to enter the bottom jacket <NUM> through the port 106d, and causes warm water to vent out of the top jacket <NUM> through the port 106a. The operation of the pump <NUM> is a timed operation.

At step <NUM>, when the pump <NUM> times out, the port 106c on the bottom jacket <NUM> opens to induce thermal gravity flow. The vehicle <NUM> begins to descend from the water surface.

At step <NUM>, the port 106c of the bottom jacket <NUM> opens while the port 106d remains open. This configuration allows a gravity density feed to operate by induction. The top tank <NUM> cools and the bottom tank <NUM> warms up as fresh surface water flows in through the port 106c.

At step <NUM>, the vehicle <NUM> is beginning its dive, and the hydraulic valve <NUM> opens, allowing hydraulic fluid <NUM> to flow through the hydraulic line <NUM>, thereby permitting the pistons <NUM>-<NUM> freedom to move.

At step <NUM>, the crossover valves <NUM> operate for a predetermined period of time, which causes CO<NUM> to flow through the fluid lines <NUM>-<NUM>. In particular, CO<NUM> flows through the first fluid line <NUM> from the actuator cylinder <NUM> to the top tank <NUM>, and CO<NUM> flows through the second fluid line <NUM> from the bottom tank <NUM> to the actuator cylinder <NUM>. This changes the fluid levels in the actuator cylinder <NUM>, which in turn causes the pistons <NUM>-<NUM> to move inward. When the piston <NUM> moves inward, hydraulic fluid <NUM> is drawn from the fluid reservoir <NUM> into the hydraulic cylinder <NUM>, thereby retracting the buoyancy plug <NUM> for initial descent.

At step <NUM>, the second fluid line <NUM> closes and the first fluid line <NUM> remains open. The buoyancy plug <NUM> push cold CO<NUM> from the actuator cylinder <NUM> back into the top tank <NUM>. The descent of the vehicle <NUM> and the rising water pressure further causes the buoyancy plug <NUM> to retract.

At step <NUM>, before the bottom depth is reached, the ports 106a-106b of the top jacket <NUM> open to take advantage of mixing flow scavenging into the top jacket <NUM>. At or around that point in time, the hydraulic line <NUM> opens, and then the crossover valves <NUM> open, so that superior differential pressure/force from the warm CO<NUM> in the bottom tank <NUM> to the cold CO<NUM> in the top tank <NUM> overcomes the inward pressure on the buoyancy plug <NUM> at depth.

At step <NUM>, when the vehicle <NUM> is at the bottom of the dive, the hydraulics lock and the fluid lines <NUM>-<NUM> close. The ports 106a-106b of the top jacket <NUM> open in order to cause mixing flow scavenging between the water in the top jacket <NUM> and the colder external seawater. In some embodiments, the soak period may be approximately twenty minutes.

As step <NUM>, as the vehicle <NUM> is preparing to ascend, the hydraulic valve <NUM> opens and the fluid lines <NUM>-<NUM> open. Pressure differences between the CO<NUM> in the top tank <NUM> and the CO<NUM> in the bottom tank <NUM> cause CO<NUM> to flow into and out of the actuator cylinder <NUM>, resulting into downward movement of the pistons <NUM>-<NUM> and outward movement of the buoyancy plug <NUM>.

At step <NUM>, as the vehicle <NUM> is ascending, the ports 106a-106b of the top jacket <NUM> close. During the ascent, seawater temperature and pressure can be monitored by on-board sensors. The hydraulic valve <NUM> locks when the buoyancy plug <NUM> is fully extended. The fluid lines <NUM>-<NUM> close.

At step <NUM>, as the vehicle <NUM> is at or near the ocean surface, the ports 106a-106b of the top jacket <NUM> open to take advantage of mixing flow scavenging of warmer seawater into the top jacket <NUM>. The ports 106a-106b of the top jacket <NUM> remain open for a period of time so that the CO<NUM> in the top tank <NUM> warms up from the warm surface seawater flowing into the top jacket <NUM>.

Although <FIG> illustrates one example of a method <NUM> for operating an underwater vehicle using ocean thermal energy conversion, various changes may be made to <FIG>. For example, while shown as a series of steps, various steps in <FIG> could overlap, occur in parallel, occur in a different order, or occur any number of times.

In some embodiments, various functions described in this patent document are implemented or supported by a computer program that is formed from computer readable program code and that is embodied in a computer readable medium.

It may be advantageous to set forth definitions of certain words and phrases used throughout this patent document. The terms "application" and "program" refer to one or more computer programs, software components, sets of instructions, procedures, functions, objects, classes, instances, related data, or a portion thereof adapted for implementation in a suitable computer code (including source code, object code, or executable code). The term "communicate," as well as derivatives thereof, encompasses both direct and indirect communication. The phrase "associated with," as well as derivatives thereof, may mean to include, be included within, interconnect with, contain, be contained within, connect to or with, couple to or with, be communicable with, cooperate with, interleave, juxtapose, be proximate to, be bound to or with, have, have a property of, have a relationship to or with, or the like.

The description in the present application should not be read as implying that any particular element, step, or function is an essential or critical element that must be included in the claim scope. The scope of patented subject matter is defined only by the allowed claims. Moreover, none of the claims is intended to invoke <NUM> U. § <NUM>(f) with respect to any of the appended claims or claim elements unless the exact words "means for" or "step for" are explicitly used in the particular claim, followed by a participle phrase identifying a function. Use of terms such as (but not limited to) "mechanism," "module," "device," "unit," "component," "element," "member," "apparatus," "machine," "system," "processor," or "controller" within a claim is understood and intended to refer to structures known to those skilled in the relevant art, as further modified or enhanced by the features of the claims themselves, and is not intended to invoke <NUM> U. § <NUM>(f).

Claim 1:
A system for use in an underwater vehicle (<NUM>) comprising:
a first jacket (<NUM>) comprising first and second ports (106a, 106b);
a first tank (<NUM>) configured to store a first fluid under pressure, the first jacket being configured to contain water and the first tank (<NUM>);
a second jacket (<NUM>) comprising third and fourth ports (106c, 106d);
a second tank (<NUM>) configured to store a second fluid under pressure, the second jacket being configured to contain water and the second tank (<NUM>);
a pump (<NUM>) configured to cause water to move between the first jacket (<NUM>) and the second jacket (<NUM>);
an actuator cylinder (<NUM>) defining a space configured to receive the first fluid from the first tank (<NUM>) and the second fluid from the second tank (<NUM>), the actuator cylinder comprising an actuator piston (<NUM>) that divides the space into a first volume for the first fluid and a second volume for the second fluid;
a hydraulic cylinder (<NUM>) defining a space configured to receive a hydraulic fluid (<NUM>), the hydraulic cylinder comprising a hydraulic piston (<NUM>) configured to move and change an amount of the hydraulic fluid in the hydraulic cylinder, wherein the hydraulic piston is fixedly coupled to the actuator piston (<NUM>); and
a buoyancy plug (<NUM>) configured to change a position inward or outward with respect to a body (<NUM>) of the vehicle (<NUM>) in connection with the amount of the hydraulic fluid in the hydraulic cylinder (<NUM>), wherein movements of the buoyancy plug are fluidly coupled to movements of the actuator and hydraulic pistons (<NUM>, <NUM>), and wherein the position of the buoyancy plug affects a buoyancy of the vehicle.