Patent ID: 12258104

DETAILED DESCRIPTION

The Figures illustrate examples of a watercraft with a battery ballast system. Based on the foregoing, it is to be generally understood that the nomenclature used herein is simply for convenience and the terms used to describe the invention should be given the broadest meaning by one of ordinary skill in the art. Unless otherwise specified, like numerals refer to like components herein.

Referring toFIG.1, a watercraft10is depicted. Watercraft10comprises a hull20which includes a bow22and a stern24, as well as a keel26. A distance between bow22and stern24defines a length axis L of the watercraft. A rudder32projects away from the keel26and is used to steer the watercraft10. Watercraft10comprises at least one propeller that is operable to propel the watercraft10through the water. InFIG.1the at least one propeller is propeller52aand propeller52b(not shown inFIG.1). Propeller52ais spaced apart from the keel26and below waterline34(when watercraft10is in a body of water). A distance along the height axis H from the keel26to the waterline34defines the watercraft's draft.

AsFIG.1indicates, watercraft10may have a draft that varies along the length axis. This variation between the draft at the bow22and stern24is characterized as the watercraft's trim. The draft is the distance from a portion of the keel to the waterline in a vertical direction, i.e., perpendicular to the waterline and the surface of the water. The difference between the draft at the bow (HF) and at the stern (HA) is known as the “trim”. The “trim by bow” is the difference in feet between the draft at the bow and at the stern as shown in equation (1):
Trim by Bow=HF−HA(1)wherein, HF=the draft at the bow (ft.)HA=the draft at the stern (ft.)

The “trim by stern” is the difference in feet between the draft at the stern and at the bow, as shown in equation (2):
Trim by Stern=HA−HF(2)

Generally, the convention is to state the trim as a positive number. When HAis greater than HF, the trim is described as a positive trim by stern, and when HAis less than HF, the trim is described as a positive trim by bow. When HAequals HF, the vessel is on an even keel. The trim may be affected by the condition of the body of water, the cargo load, and the ship design. As mentioned previously, ballast is typically adjusted along the length axis of the watercraft10to achieve a desired trim.

FIG.2A-2Bprovide a schematic representation of the stern24of watercraft10used to depict the list of the watercraft10. InFIG.2A, the watercraft10is upright, and its center of gravity and center of buoyancy are collinear with the vertical axis (i.e., an axis perpendicular to the earth, the surface of the water, and the waterline W). Thus, watercraft10has a list angle of zero. InFIG.2Ba disturbance has caused the watercraft10to tilt toward the starboard direction, and the center of gravity and center of buoyancy are co-linear with a line that defines a list angle θ with the vertical line inFIG.2A. As mentioned previously, the ballast may be adjusted along the width axis of watercraft10to adjust the list angle θ.

Referring toFIGS.3A and3B, a ship200is depicted which comprises a hull201and a battery ballast system211. The battery ballast system211is preferably located in a lower deck210below the main deck (not shown) along the ship's height axis H. Lower deck210has a starboard bulkhead202and a port bulkhead204spaced apart along the ship's width axis. InFIG.3Abattery ballast system211is shown below the main deck and cargo hold206as well as below a potable water system deck208that houses a portion of the ship's potable water system, an example of which is discussed below with reference toFIG.6A. Purified potable water is located on deck212.

The battery ballast system211comprises a carriage system that includes a plurality of carriage assemblies214-244(FIG.3B). Each carriage assembly214-244comprises a plurality of batteries292. The carriage assemblies214-244are selectively movable along the watercraft's length axis to adjust the watercraft's ballast along the length axis. Each carriage assembly214-244comprises a plurality of tiers arranged along the watercraft's10height axis. Each tier comprises a pair of tracks and a plurality of battery supports, each of which engages and is movable along a corresponding one of the pairs of tracks.

Carriage assembly214is depicted schematically inFIG.3A. Each of the carriage assemblies214-244has the same structure in the illustrated embodiments, although different structures may be used. Carriage assembly214comprises eight tiers A-H, which are arranged along the watercraft's height axis H. The same tier naming convention applies to the tiers of carriage assemblies216-244. The tiers A-H are spaced apart along the height axis inFIG.3Afor ease of viewing, but are actually connected to define an integral carriage assembly214.

Each tier A-H includes fifty slots which are locations that can accommodate a battery292. The slots are arranged along the watercraft's width axis. The slots1-50are fixed positions within the carriage assembly. Different batteries292may be repositioned to different slots. The batteries292are positioned on battery supports (described below) that move along the tracks of the tier to which the battery belongs and along the ship's width axis. As discussed in greater detail below, the battery supports are generally I-shaped members, the opposite ends of which slidingly engage the rails of the carriage assembly tier to which they belong. In certain examples, each battery and a corresponding battery support (described below) on which the battery is positioned is individually movable along the watercraft's width axis. However, in other examples, individual batteries are grouped together and move together, such as in groups of five, ten, fifteen, or twenty batteries. Grouping batteries in the matter provides somewhat reduced flexibility in positioning the batteries where desired but simplifies the motor assembly required to move the battery supports.

The number of battery supports in a given tier A-H is preferably less than the number of slots1-50in the tier. Otherwise, the batteries292in that tier could not be repositioned along the width axis to alter the list angle θ. (FIG.2B). All batteries292can be moved along the width axis, either toward or away from the starboard and port bulkheads202,204. A subset of batteries292can be moved from one side of midship to the other side of midship along the width axis (Mw). The number of batteries in the subset depends on the loading of the slots. In the example ofFIG.3A, 9 of the 32 batteries in each tier can be moved from one side of midship along the width axis to the other.

The number of open slots293(slots without battery supports) in a given tier A-H is preferably from about 30% to about 50% of the total slots in the tier, more preferably, from about 35% to about 45% of the total number of slots in the tier, and still more preferably from about 34% to about 38% of the slots in a given tier. InFIG.3Aslots H(10)-H(41) of tier H are occupied in carriage assembly214, whereas slots H(1)-H(9) and H(42)-H(50) are unoccupied.

As indicated inFIG.3A, the different tiers A-H may be loaded the same or differently with batteries292. Tiers A-D have batteries292and battery supports in slots1-16and35-50only, whereas tiers E-H have batteries and battery supports in slots10-41only. As an example of how the batteries292would be re-positioned to alter the list angle θ, if watercraft200had the orientation shown inFIG.2Bfor watercraft10, moving batteries292from the starboard side to the port side of the width axis midship line Mw would tend to restore the watercraft10to its upright orientation ofFIG.2A.

Referring toFIG.3B, the upper tier H of each of carriage assemblies214-244is shown. The configuration of batteries292and slots1-50in tier H of carriage assembly214differs inFIG.3Brelative to3A. InFIG.3Bsixteen carriage assemblies214-244are shown. However, many more may be provided depending on the ship200. As the figure indicates, each carriage assembly214-244is selectively movable along the length axis of the ship relative to hull201. As also indicated, the battery292loading configurations for the upper tier H of each carriage assembly214-244may vary along the ship's length axis. In carriage assemblies214-218and220, slots1-9and28-50are occupied with batteries292. In carriage assemblies222-228slots1-32are occupied. In carriage assemblies230-234, slots1-22and41-50are occupied, and in carriage assemblies236-244slots1-32are occupied.

The numbers of slots, the percentage of open slots per tier, and the number of carriage assemblies are preferably selected based on the battery dimensions and weights and the desired degree of ballast on each side of the location that is midship along the width axis (Mw) and midship along the length axis (ML). In certain examples, the distance along the length axis occupied by the carriage assemblies214-244is about 60% to about 75% of the maximum available distance along the length axis, preferably about 65% to about 70% , and more preferably from about 66% to about 68%. The distance occupied by the carriage assemblies214-244along the length axis is the distance along the length axis occupied by the carriage assemblies214-244when they are all placed in abutting engagement with no spaces between them. The maximum available distance is the distance between the maximum fore and aft positions of the two carriages that are closest to the bow and the stern, respectively. InFIG.3Bthose carriage assemblies are214and244.

The carriage assemblies214-244are structured similarly to one another. One carriage assembly220is illustrated inFIG.4. Only four tiers A-E and a portion of carriage assembly220proximate starboard bulkhead202are depicted inFIG.4. Tier E has a parallel set of tracks262and264which extend along the ship's200width axis and are spaced apart from one another along the ship's200length axis. Four vertical members (not shown) are placed at the ends of the tracks262and264and are secured to the tracks262and264as well as to the tracks of all the other tiers in carriage assembly220by suitable mechanical fasteners, welding, or other reliable means. Battery support261is one of several battery supports in tier E and may also be referred to as a “carriage seat”. Battery support261is an I-shaped member that comprises a cross-beam266extending between parallel tracks262and264along the length axis of the ship200and end beams267and265(not shown), which each slidingly engage a respective one of parallel tracks262and264along the ship's200width axis. End beam267includes a vertical section269and a horizontal section273. End beam265(not shown) is structured and engages the corresponding track264in a similar fashion. The details of the engagement between the battery supports and tracks are provided inFIG.5and discussed further below.

Batteries292each sit on a corresponding battery support. InFIG.4tier E slots45and46-49are occupied. Although battery support261is visible, when the support261is unoccupied, it would typically be removed to allow a greater degree of movement for the other batteries in the tier.

Tier D comprises parallel tracks268and270which extend along the ship's width axis and are spaced apart along the ship's200length axis. Battery support271extends between parallel tracks268and270along the watercraft's length axis and comprises cross-beam272and end beams274and276. Each end beam274and276slidingly engages a respective one of parallel tracks268and270along the ship's200width axis in the same manner that end beam267engages track262, as described previously. If the support271were occupied, the battery292would rest on the cross-beam272and the end beams274and276.

Tier C comprises parallel tracks278and280and battery support281(along with additional supports not called out). Parallel tracks278and280extend along the ship's200width axis and are spaced apart along the ship's200length axis. Battery support281is an I-shaped member that comprises a cross-beam282which extends between the parallel tracks278and280along the length axis, and end beams284and286, each of which slidingly engages a respective one of parallel track278and280along the ship's200width axis in the same manner that end beam267of battery support261engages track262. InFIG.4slots E(50), D(50), and A(50) are not visible. Carriage assembly220preferably slidingly engages a pair of rails spaced apart along the ship's width axis and extending along the ship's length axis to move carriage assembly220along the ship's length axis relative to hull201as would the other carriage assemblies214-244.

Referring now toFIG.5, an exemplary battery support for the carriage assemblies214-244described herein is illustrated. InFIG.5the battery support271from carriage assembly220ofFIG.4is illustrated. However, it is understood that in this example, the battery supports for the other carriage assemblies are configured similarly.

Each battery support in each tier A-H is movable transversely to the ship's length axis and along the ship's width axis relative to the ship's hull201. In the example, battery support271includes a cross-beam272attached to end beams274and276, as described previously. End beam274comprises an upper horizontal section312and a lower vertical section316. Two wheels are rotationally mounted on the lower vertical section316and are spaced apart along the ship's200width axis direction from one another. Only wheel320is visible on lower vertical section316. Wheel320is positioned between the lower vertical section316of end beam274and an upward extending vertical section306of track268. Track268also includes a lower lip302that projects toward the other track270along the length axis of the ship200. Wheel320rests on the lower lip302and rolls along it to allow end member274to slidingly engage track268along the ship200width axis. The other wheel (not shown) attached to the opposite end of the end beam274is configured in the same way,

End beam276also includes an upper horizontal section314and a lower vertical section308. The track270is configured as a mirror image or track268. End beam276includes two wheels attached to opposite ends of the lower vertical section. Wheel322is shown, but the wheel at the other end of the end beam276is not shown. Lower lip304functions similarly to lower lip302. Thus, wheel322is positioned between the lower vertical section of the end beam276and the upward extending vertical section308of track270and rides along lower lip304of track270. Thus, end member276has two wheels at opposite ends of end member276which roll along lower lip304of track270, thereby allowing the end member276to slidingly engage the track270along the width axis of the ship200.

In certain examples, each battery support in carriage assemblies214-244is motor-driven along its corresponding pair of tracks. A conventional motor assembly is provided and is operable to move each battery support in a given tier A-H of a given carriage assembly214-244to a desired slot location. In other examples, the battery supports are connected in groups (such as groups of five, ten, fifteen, or twenty) of battery supports that move together along the ship's200width axis relative to hull201.

As shown inFIG.5, each battery292is positioned and secured to the battery support271by, for example, four twist locks325,327,329, and331at four corners of the battery292that can be interlocked with openings324,326,328, and330(not shown inFIG.4) positioned in end beams274,276of battery support271manually or by a remote control. It is to be appreciated that although the battery support271has been illustrated with openings324,326,328,330for mating the twist locks325,327,329, and331of the battery support271, the battery support271can also be provided with twist locks that mate with corresponding openings on the battery292. Similar twist locks can also be provided either on the battery supports the batteries for interlocking of abutting battery supports or batteries to each other while the vessel is in motion.

In a preferred example of the battery and ballast system211described herein, a conventional motor assembly is provided to drive each of the battery supports271in each tier A-H along the tracks268,270. In addition, a motor assembly control system which comprises a conventional remote control device may also be provided to allow users to operate the ballast system211outside the deck on which the battery ballast system211is located. The user can thus driveably move batteries292to a desired slot in their respective tier. These conventional mechanisms are typically provided in order to achieve proper alignment of the battery supports271, within each tier, for storage and retrieval operations. The remotely controlled motor assemblies may be mounted, for example, within a cross-beam272of each battery support271.

Thus, in one example, each individual battery support is separately driveable and the remote motor control is provided with a conventional selection device for separately driving each battery support271independently of the other battery supports. When ballast adjustments are required in a particular tier, the user can thus separately drive the individual battery supports to an appropriate slot to affect the vessel's list and/or trim. In one example, each battery support is assigned a unique identifier and each slot is assigned a unique identifier so that a remote control may be operated to drive a particular battery support to a particular slot. Of course, not all slots will be accessible to all battery supports in a given tier because of the number of battery supports in the tier. For example, each tier may have32battery supports identified as S(1)-S(32). Within the tiers shown inFIGS.3A and3B, the S(1) support could be located in any of slots1-32. The S(2) battery support could be located in any of slots2-33, etc. In other words, the number of vacant slots in each tier equals the number of different slots that a given battery support271may occupy within that tier. However, the particular slots that a given battery may occupy will depend on the battery's location relative to other batteries in the same tier. In other examples, the battery supports may be grouped as described previously. They also may be selectively grouped using suitable mechanisms for joining adjacent battery supports271together such as an electromagnetic coupling system, an electromotive coupling system or a mechanical coupling system (e.g., a system of hooks connecting adjacent battery supports271).

In certain examples, each carriage assembly214-244is motor driven along its tracks (not shown) and along the length axis of the vessel. The total length of the available area that is unoccupied by carriage assemblies divided by the length (along the watercraft length axis) of each carriage assembly determines how many carriage assembly locations a given carriage assembly may occupy. For example, if the carriage tracks extend600feet along the vessel length axis and each carriage assembly has a length of four (4) feet along the vessel length axis, there will effectively be150carriage assembly positions along the vessel's length axis. If 100 carriage assemblies are provided, the total effective length of all carriage assemblies will be 400 feet, leaving 200 feet unoccupied. In that case, each carriage assembly may occupy 50 different carriage assembly locations along the vessel length axis. In other examples, adjacent carriage assemblies may be joined or selectively joined to move as groups along the ship's length axis relative to hull201.

In certain examples, the total weight (or mass) of the battery ballast system211is from about 20 to 30 percent of the ship's 200 dead weight tonnage. “Deadweight tonnage” is a measurement of total contents of a ship including cargo, fuel, crew, passengers, food, and water aside from boiler water. In the same or other examples, each slot of the carriage assembly (including battery supports, but not batteries) is from about 15 lbs to about 25 lbs., preferably from about 17 lbs. to about 23 lbs., and more preferably from about 18 lbs., to about 21 lbs. In the same or other examples, batteries 292 weigh from about 100-200 lbs., preferably from about 120 lbs. to about 180 lbs., and more preferably from about 140 lbs. to about 160 lbs.

Unlike ballast water systems, battery ballast system211cannot add or expel batteries292while at sea. Thus, while it can be repositioned along the vessel's length and width axes, the total amount of battery ballast on ship200cannot be varied while the ship200is at sea. In one example, the volume of potable water produced by the vessel's200potable water system is varied to effectively provide an additional source of ballast. In certain examples, the ship's potable water system is used to change the watercraft's total amount of ballast by changing the total volume of treated water on board such as by expelling treated water overboard or changing the rate of untreated water being fed to the potable water system.

Referring toFIG.6A, potable water treatment system340is depicted. Potable water treatment system340is provided to produce fresh, drinkable water from sea water. The potable water treatment system340comprises a desalination unit341that includes an evaporator344and condenser342. The evaporator344creates steam from sea water and removes salt and other non-volatile materials. The steam is then condensed to form potable water.

Sea water brought in via sea water inlet345is pumped by ejector pump348into condenser cooling water inlet line356. Coil370is provided in the condenser342to provide additional surface area for heat transfer from condensing steam to the cooling water. The cooling water leaves condenser in discharge stream372. A portion of the discharge stream372is recycled back to the condenser via recycle stream366, and the balance of the discharge stream372is discharged overboard in overboard discharge line364.

The recycle stream366enters secondary cooling coil368within condenser342and provides secondary cooling to evaporating steam. After leaving the cooling coil368, the stream is directed to evaporator344and becomes evaporator feed steam374. Engine jacket water provides the heat of evaporation and enters the evaporator344via evaporator heating medium inlet stream376. The evaporator heating medium inlet stream376enters the evaporator's heated nest380and exits the evaporator344via evaporator heating medium outlet steam378. The heat from the engine jacket water and the pressure at which the evaporator344is operated causes the evaporator feed stream water374to evaporate within the evaporator344and enter the condenser342. The evaporating water (steam) passes through an annular demister358and transfers heat to the cooling water in cooling water coils370and368, causing the steam to condense into condensation trap360. Condensed water from condensation trap360enters treated water pump suction line362and is pumped by treated (fresh) water pump354to fresh water tank346. In one example, a level controller may also be provided to control the level on the condensation trap360and may be cascaded to a condenser fresh water outlet line355flow controller392(FIG.6B). Flow controllers may also be provided on the condenser cooling medium recycle line366and/or the evaporator heating medium inlet line376or outlet line378. A variety of different control schemes may be used, but they preferably ensure that the condensate trap360does not run dry and that the necessary amount of fresh water is supplied to fresh water tank346based on shipboard needs.

In a preferred example, a portion of the volume of fresh water in fresh water tank346is used as ballast. In accordance with the example no ballast water tanks are provided that are not fluidly coupled to potable water system340. As mentioned previously, battery ballast system211cannot add or subtract ballast while ship200is at sea. If it desirable to increase or decrease the vessel's draft at both the bow and the stern, merely adjusting the locations of batteries292will be insufficient. Thus, in certain examples, the potable water treatment system340is sized to allow the volume of water in fresh water tank346to be varied to provide a desired amount of total ballast variation, i.e., an amount of fresh water that can be expelled from or added to fresh water tank346that corresponds to the maximum ballast weight change that is anticipated.

In certain examples, when a decrease in total ballast is required, fresh water from fresh water tank346is expelled overboard. The volume of water corresponding to a particular expelled mass of water is shown in equation (3) below:
VE=ME/ρ(3)where, VE=expelled volume (gal.)ME=expelled mass (lbm)ρ=density of water (8.35 lbm/gal.)

Based on the tank dimensions, the corresponding change in level can be calculated (assuming a cylindrical geometry) as follows:
ΔL=(0.5348VE)/πD2(4)where, VE=expelled volume (gal.)D=Tank diameter (ft.)

For a rectangular prism tank, equation (3) still applies, but instead of equation (4), the following equation is used to calculate level changes:
ΔL=(0.1337VE)/(a·b)   (5)where, VE=expelled volume (gal.)a=tank width (ft.)b=tank length (ft).

When a change in total ballast is required, it can be effected manually or automatically. In a manual implementation, when a ballast increase is required, flow control valve406will first be closed if it is open. If the valve406is already closed or if closing it does not provide the desired amount of additional ballast, the flow rate of sea water into the potable water treatment system340may be increased, for example, by opening flow control valve351on the discharge of pump352(FIG.6A) or by increasing the set point of flow controller353, which receives a flow measurement signal from flow meter355.

A variety of suitable control systems may be provided to allow the volume of fresh water in fresh water tank346to be varied or expelled based on ballast needs. In one example, a suitable control scheme is provided which is configured to admit or expel a volume of water from tank346based on ballast needs while ensuring that the condensate trap360does not run dry and while also ensuring that level in tank346remains at an acceptable level to operate potable water pump408and providing the ship's fresh water usage needs for cooking, bathing, laundry, etc. via shipboard fresh water line414. In one exemplary control scheme, a flow rate of shipboard fresh water in fresh water line414is adjusted to control the level of tank346, and the overboard discharge line411flow rate is adjusted to change the total amount of ship ballast. Fresh water line414and overboard discharge line411are described in greater detail below.

In one implementation, ballast changes are made by varying the flow rate of treated water that is expelled via overboard line411. In the same or other implementations, ballast changes are made by varying the flow rate of sea water into the potable water system such as by adjusting the set point of flow controller353or opening valve351to a desired percentage open.

In a further implementation, desired decreases in ballast are made by increasing the flow rate of expelled water in overboard line411and then, if necessary, decreasing the sea water inlet flow rate to potable water treatment system340. In the same implementation, increases in ballast are made by first decreasing the amount of expelled freshwater in overboard line411, and if necessary, increasing the sea water inlet flow rate to potable water treatment system340. These adjustments may be made by manually manipulating valves406and351, by changing the setpoints via their respective flow controllers404and353or by using a ballast controller such as ballast controller400, described further below.

In another exemplary control scheme, a ballast controller adjusts the flow rate of overboard discharge line411until valve406is closed or until the ballast controller is overridden by a level controller that controls the level in tank346, at which point the ballast controller adjusts the setpoint of flow controller353(FIG.6A) to adjust the sea water inlet flow rate to potable water system340. Because ballast changes will often be discrete, if a ballast decrease is desired, in this example, the ballast controller will first try to increase the flow rate of ballast water in overboard line411and will then try to decrease the sea water inlet flow rate to the potable water treatment system340. In this example, if a ballast increase is required, the ballast controller will first try to decrease the flow rate of overboard line411and will then try to increase the sea water inlet flow rate to potable water treatment system340if needed.

Referring toFIG.6B, in general the level in tank346must be maintained to provide sufficient net positive suction head to pump408, which may constrain the extent to which opening or closing valve406can be used to effect a desired ballast change. InFIG.6Ban exemplary control system is provided which addresses both the level control of tank346and ballast control. The depicted control scheme controls the ship's total ballast load by adjusting the flow rate of expelled water in overboard line411. A desired change in total ballast may be effected in a desired time period and converted to an overboard discharge line411flow rate as follows:
F411=(WE/ρ)/Δt(6)F411=flow rate in line411(gal/hour)WE=Total desired change in ballast (lbs.)ρ=density of water (8.35 lb./gal.)Δt=time interval for changing ballast (hours).

Pump408pumps fresh, potable water from tank346to overboard discharge line411and shipboard fresh water line414. Overboard discharge line411directs fresh water from tank346overboard and is used to adjust the total amount of ballast by expelling fresh water overboard when a ballast reduction is needed or throttling back on the amount of water sent overboard when an increase is needed.

The overboard discharge line411flow rate is controlled by flow controller404which adjusts control valve406based on a flow rate measured by flow meter402. Shipboard fresh water line414routes fresh water to showers, bathrooms, laundry, kitchens, and any other areas requiring fresh water. The flow rate of fresh water in shipboard fresh water line414is controlled by flow controller413which adjusts control valve412based on the flow rate measured by shipboard fresh water flow meter410. Although not shown, a recycle line may be provided downstream of control valve412so that fresh, potable water not demanded by shipboard users can be recycled back to the tank346inlet line355.

A ballast controller400is provided and adjusts the overboard discharge line411flow rate by resetting the set-point of flow controller404to change the total amount of ship ballast in accordance with equations (3) and (4). As indicated inFIG.6, the ballast controller400receives a level indication from level transmitter396and uses the level indication to determine the current volume and weight of fresh water in tank346. Ballast controller400receives a user-entered set point that corresponds to a change in the amount of ballast, or a total amount of ballast in tank346(the ballast provided by batteries292can only be shifted in the vessel and cannot be increased or decreased while at sea), and a time interval during which the ballast change is to be made. If a total ballast set point is entered, ballast controller400would calculate the required ballast change to achieve that set point. In either case the ballast controller400includes an algorithm that converts a desired change in total ballast weight and a user-entered time frame for making the change into a flow rate of overboard stream411in accordance with equation (6). The ballast controller400adjusts the set point of flow controller404to the determined set-point to direct fresh water overboard via overboard discharge line411until the desired amount of total ballast is achieved or until the desired change in ballast is achieved, at which point the ballast controller will re-set the flow controller404set-point to zero. The ballast controller400may also ramp the setpoint of flow controller404gradually to effect a smoother change in ballast.

A level controller398receives a level indication signal from tank346level transmitter396and resets the set point of flow controller413to maintain a desired level of fresh water in tank346. During normal, steady-state operation the overboard discharge line control valve406will preferably remain closed to avoid wasting purified water. Thus, level controller398will typically adjust the flow rate of shipboard fresh water line414by adjusting the set point of flow controller413to maintain the desired level in fresh water tank346. However, if control valve412is fully open and the level in tank346continues to rise, level controller398will preferably increase the set point of discharge line flow controller404to direct fresh water overboard until the tank346level reaches it set point. Alternatively or additionally, the level controller398may first reset flow controller353(FIG.6A) before resetting the setpoint of flow controller404to reduce the amount of seawater coming into the potable water treatment system340to stop the level in tank346from increasing. The flow of fresh water into tank346is controlled by flow controller392which adjusts control valve391based on the flow rate measured by inlet flow meter390. Flow controller392is re-set by level controller394which controls the level of condensate trap360. A level indicator would be provided on condensate trap360but is not shown inFIG.6A. As the setpoint of flow controller353changes, the level in condensate trap360will change, causing condensate tray level controller394to adjust the inlet flow rate setpoint of flow controller392to stabilize the tank346level.

In implementations where level controller398will override the ballast controller400and adjust the set point of flow controller404to control the tank346level, a high signal selector403is provided and selects the higher output signal from among the level controller398and the ballast controller400. It is preferable that this override function occur only after the shipboard fresh water flow control valve412is fully open. Thus, level controller398is preferably configured as a split range controller such that for a first part of its output range, say from 0 to 50 percent, it adjusts the shipboard fresh water line414flow controller413set point and for a second part of its output range, say, from greater than 50 percent to 100 percent, it sends an output signal to the high signal selector403to adjust the set point of overboard discharge line411flow controller404as needed. As suggested above, a three way-split range may be used wherein the level controller opens valve412from 0-33 percent, closes valve351(FIG.6A) from 33-66 percent, and then opens valve406from 67 to 100 percent of the level controller398output signal. The valve adjustments may be directly made or by re-setting the setpoints of flow controllers353,413, and404.

The controllers shown inFIG.6Bmay be implemented in software or hardware and may be digital or analog. Appropriate transducers would also be provided to convert electrical signals to pneumatic signals and vice-versa if needed. In one example, the set point of ballast controller400is adjusted manually by ship personnel to achieve the desired total amount of ballast on board. However, if a draft measurement device or draft estimating technique is used, an advanced ballast control scheme may also be provided which adjusts the set point of the ballast controller400automatically. For example, an advanced control scheme may include a draft controller that allows a user to input a set point for the total amount of draft at one location along the hull or the average of the draft and multiple locations and then re-set the ballast controller set point as needed to achieve the desired draft.

In one example of a watercraft with a battery ballast system, the watercraft is devoid of water ballast tanks other than those fresh water tanks that comprise part of the ship's potable water system. In many existing watercraft, the hull volume consumed by ballast water tanks would leave insufficient room for a battery ballast system with enough batteries to make meaningful ballast adjustments. Thus, in some cases it is preferable that the watercraft10be devoid of water ballast tanks, except to the extent such tanks serve the dual purpose of retaining treated, potable water for shipboard use as is the case with tank346. In other words, in such cases it is preferable if watercraft10is devoid of ballast water tanks that are not fluidly coupled to a fresh, potable water system340.

In accordance with another example, a water craft is provided with a battery ballast system of the type described herein in which the watercraft is devoid of fossil fuel tanks and fossil fuel engines. Fossil fuel tanks and engines. typically consume a significant amount of shipboard volume and which make it difficult to include a battery ballast system of sufficient size to make meaningful ballast adjustments. In accordance with a further example, a watercraft is provided which comprises a hull, a propeller operable to propel the watercraft through a body of water, an air motor operative to rotate the propeller, an air storage tank in selective fluid communication with the air motor, an air compressor operable to selectively supply compressed air to the air storage tank, and a ballast comprising a plurality of batteries, wherein the batteries in the plurality of batteries are selectively positionable along at least one of a vessel length axis and a watercraft width axis. In one implementation of the further example, the watercraft is devoid of fossil fuel and fossil fuel engines. In accordance with the same or other examples, the watercraft includes a potable water system, including, for example, potable water system340type depicted inFIGS.6A-B.

Referring toFIG.7an air and electric propulsion system40useful for use with a watercraft that includes a battery ballast system of the type described herein is provided. The air and electric propulsion system ofFIG.7is sized for a smaller vessel such as watercraft10ofFIG.1. However, the size and/or number of components may be scaled up as needed depending on the size and weight of the vessel. A vessel comprising an air and electric propulsion system and a battery ballast system will be described with reference to watercraft10ofFIG.1and air and propulsion system40ofFIG.7, but it should be understood that the watercraft10and air and electric propulsion system40can be scaled accordingly to accommodate the battery ballast system211of ship200and that a ship200with a battery ballast system of the type described herein and having the air and electric propulsion system40ofFIG.7, scaled as appropriate to the size of ship200, is expressly contemplated.

Propeller52ais operatively connected to a proximal propeller shaft section48awhich rotates about its lengthwise axis / to rotate propeller52awithin the body of water. The rotation of propeller52awithin the water propels the watercraft10in a direction defined by the direction of rotation of propeller52a,the geometry of the propeller blades, and the orientation of rudder32.

In this embodiment, watercraft10is not powered by a fossil fuel engine and does not include a fossil fuel engine or fossil fuel tanks. Instead, an air motor is provided which is operative to rotate at least one propeller. Referring toFIG.7, air propulsion system40is provided which includes a propeller train42, an air supply system47and a rechargeable battery system44. A control system is also provided. Air supply system47includes at least one compressed air storage tank which is in selective fluid communication with the at least one air motor as well as at least one compressor that is operable to selectively supply compressed air to the at least one air storage tank.

InFIG.7the at least one propeller used to propel watercraft10through the water comprises two propellers52aand52b.Propeller train42comprises two parallel propeller systems43aand43b.Each propeller system43aand43bfurther comprises a respective propeller shaft assembly46aand46band respective propeller52aand52b.Propeller shaft assembly46ais a multi-segment shaft that comprises a proximal propeller shaft section48aand a distal propeller shaft section50a.The proximal propeller shaft section48aand distal propeller shaft section50bare connected by a coupling54a.The proximal end of the propeller shaft assembly46ais defined by the proximal end of the proximal propeller shaft section48aand is connected to air motor62a.The distal end of propeller shaft assembly46ais defined by the distal end of distal propeller shaft section50aand is connected to propeller52a.Similarly, propeller shaft assembly46bis a multi-segment shaft that comprises a proximal propeller shaft section48band a distal propeller shaft section50b.The proximal propeller shaft section48band distal propeller shaft section50bare connected by a coupling54b.The proximal end of the propeller shaft assembly46bis defined by the proximal end of the proximal propeller shaft section48band is connected to air motor62b.The distal end of propeller shaft assembly46bis defined by the distal end of distal section50band is connected to propeller52b.Each propeller shaft assembly46aand46bhas a length along a length axis l. When its respective air motor62aor62bis activated, each shaft assembly46aand46brotates about its respective length axis / as indicated by the curved arrows. The shaft rotation causes each respective propeller52aand52bto rotate about its length axis l and move the watercraft10through the water.

As mentioned above, air motors62aand62bare operable to rotate their respective propeller shaft assembly46aor46band their respective propeller52aor52b.Air motors take compressed air and allow it to expand to do mechanical work. Air motors may be linear or rotary depending on the type of mechanical work required. In the case of air motors62aand62b,rotary air motors are preferred. The specific rotational frequency of the propeller and horsepower will depend on the weight of the watercraft10and the desired speed of travel. In one example, a rotary air motor is used. Suitable, commercially-available, rotary air motors include the 1UP-NRV-15 rotary air motor provided by Gast Manufacturing, Inc. of Benton Harbor, Mich. This motor provides 0.45HP and a torque of 5.25 in-lb at a maximum (no load) rotational speed of 6000 RPM. It also provides a speed of 500 RPM at a maximum torque of 6.0 lb-in. The motor also has a maximum air consumption of 27 cubic feet per minute. The shaft diameter is ⅜ inches, and the air inlet port size is ⅛″ NPT. It is rated for a maximum pressure of 80 psig. In the case of ship200, suitable air motors would include Ingersoll Rand KK5B Piston Air Motors which provide at least 29-30 HP and a torque of about 65 lbf-ft at a maximum rotational speed of about 1400 rpm. The motors have a maximum air consumption of about 800-850 standard cubic feet per minute.

The air used to run the air motors62aand62bis provided by air supply system47. Air supply system47comprises air compressor78and a plurality of in-line air-storage tanks80a,82a,80b,and82b.The term “in-line” refers to the fact that each pair of storage tanks (80a/82aand80b/82b) is in the flow path from the compressor78to the air motors62aand62b. The pairs of storage tanks—80a/82aon the one hand and80b/82bon the other hand—are in parallel with respect to one another, but are each in the flow path from a compressor discharge line (108aand108b,respectively) to the air motors62aand62b.Put differently, the air storage tanks80a,82a,80b,82bdo not supply air motors62aand62bin parallel with the compressor78. One or more auxiliary air compressors (not shown) may also be provided to provide supplemental air and ensure that the air motors62aand62bhave sufficient air flow rates while at the same time ensuring that the air-storage tanks80a,82a,80b,and82bcan be refilled after reaching a desired state of depletion (e.g., a threshold lower pressure limit).

The air compressor78discharges to and is in fluid communication with parallel slave air storage tanks82aand82bvia compressor discharge lines108aand108b.Each slave air storage tank82aand82bis fluidly coupled to and in fluid communication with a respective master air storage tank80aand80bby a respective pressure drop valve84aand84b.The pressure drop valves84aand84bensure that the slave air storage tanks82aand82boperate at a higher pressure than their corresponding master air storage tanks80aand80b,ensuring that air flows from the slave air storage tanks82aand82bto their corresponding master air storage tanks80aand80bbut not in reverse, such as when the slave air storage tanks82aand82bare being refilled. The extra pressure drop forces the compressor78to run at a higher discharge pressure and lower flow rate than it otherwise would, which prevents oversupplying air to the air motors62aand62b.The pressure drop valves84aand84bcan be control valves, pressure regulators, check valves, etc. However, in certain examples they are not automatically manipulable to achieve a desired pressure, but rather, just provide a source of pressure drop in the system and adjust the operation of the compressor to a higher discharge pressure regime. In certain examples, the pressure drop across each pressure drop valve is from about 1000 psig to about 4000 psig, preferably from about 1500 psig to about 3500 psig, still more preferably from about 2000 psig to about 3000 psig, and still more preferably from about 2400 psig to about 2600 psig.

In preferred examples, the air compressor78is run periodically to fill the slave air storage tanks82aand82buntil their respective pressures reach a desired maximum pressure (Pmax). Filling slave air storage tanks82aand82bwill also cause master air storage tanks80aand80bto fill with air. Such periodic refilling operations are carried out when the pressure in the slave air storage tanks82aand82breaches a predefined lower limit (Pmin). A low pressure switch may be installed on the slave air storage tanks82aand82bto determine when the predefined lower pressure limit Pminhas been reached. Alternatively, hardware or firmware in the control unit69may use pressure signals provided from pressure sensors in slave air storage tanks82aand82bto determine if the pressures have fallen below Pmin. Among other benefits, periodic (as opposed to continuous) operation of the compressor78allows watercraft10to run more quietly for long stretches of time (e.g., when the compressor is off). In certain examples, Pminis no less than about 1500 psig, preferably not less than about 1700 psig, and more preferably not less than about 1900 psig. In the same or other examples, Pminis no more than about 2500 psig, preferably not less than about 2200 psig, and more preferably not less than about 2100 psig.

The in-line slave air storage tanks82aand82bare preferably maintained at an operating pressure that is above a first specified threshold value, which is a pre-defined lower limit (Pmin) and below a second specified threshold value, which is a pre-defined upper limit (Pmax). The predefined lower limit Pminis preferably high enough to ensure that a desired air flow rate to the air motors62aand62bcan be maintained at a desired air inlet pressure at the air motors62aand62b.Rotary air motors62aand62bhave characteristic curves that relate the speed of rotation of the motor to the air motor inlet pressure and volumetric flow rate. The in-line air storage tanks80a/80band82a/82bensure that the desired combination of volumetric air flow rate and air motor inlet pressure can be maintained so that the desired speed of propeller rotation can be achieved. Also, the tanks80a/80band82a/82bare preferably pre-filled to the maximum desired tank pressure (Pmax) before a trip. As a result, the compressor78may run only periodically. However, when compressor78is running, it is preferred that the compressor discharge flow rate (mass of air) exceeds the rate of consumption by air motors62aand62bso that the tanks80a,80band82a,82bare replenished. Nevertheless, even during refilling operations, the air motors62aand62bmay periodically consume more air than the compressor78provides as long as on average the air motors62aand62bconsume less air than is being provided by compressor78. Thus, the in-line air storage tanks80a,80b,82a,82bprovide greater flexibility in adjusting the speed of the boat by providing surge volumes and reserve volumes of air.

In certain examples, the desired maximum slave tank82a,82bair pressure Pmaxis at least about 3000 psig, preferably at least about 4000 psig, and more preferably at least about 4200 psig. Pmaxis preferably no greater than about 6000 psig, preferably no greater than about 5000 psig, and more preferably not greater than about 4600 psig. In the same or other examples, the volume of each slave tank82a,82band master tank80aand80bis at least about350cubic feet, preferably at least about 380 cubic feet, and more preferably at least about 440 cubic feet, and the volume is no more than about 530 cubic feet, preferably no more than about 500 cubic feet, and more preferably no more than about 450 cubic feet. One exemplary type of air storage tank useful as master tanks80a,80band slave tanks82a,82bis the NUVT4500 storage tank supplied by Nuvair of Oxnard, Calif. The tank has a maximum service pressure of 4500 psig, and an internal storage volume of 437 cubic feet. In one example where the watercraft is a ship200, the volume of each slave tank82a,82band master tank80aand80bis sized to provide the desired maximum ship speed at the maximum expected ship weight based on the weight of the ship, the selected air motors, and the maximum expected cargo load, as well as based on any non-cargo items that affect the ship's weight.

The air compressor78takes air from the atmosphere and compresses it to a pressure sufficient to supply the master and slave tanks80a/80band82a/82buntil the slave air storage tanks82aand82breach their desired maximum pressure (Pmax) during a refilling operation. A high pressure switch may be provided to determine when Pmaxhas been reached. The switch may be a hardware switch installed on each slave air storage tank82aand82bor a software or firmware switch in a controller within power distribution panel88which receives pressure sensor signals from sensors installed on the slave air storage tanks82a,82b.In either configuration, the controller uses an input signal or signals to determine whether to turn off the compressor78motor. In the case of multiple slave air storage tanks82a,82b,the compressor78may be turned off when either slave tank82a,82breaches Pmax. Alternatively, the compressor78may remain on until both slave air storage tanks82aand82breach Pmax. However, the former approach is preferred as it prevents overfilling the slave air storage tanks82a,82bif one of the pressure sensors or switches fails. Suitable commercially available air compressors include the Bauer Model No. 100 air compressor which has a maximum air discharge pressure of about 5000 psig. In the case of ship200, suitable air compressors would preferably be selected based on the maximum desired motor power.

Compressor78discharges compressed air to slave air storage tank82avia compressor discharge line108aand to slave tank82bvia compressor discharge line108b.In some examples, the air compressor78can supply air at a mass flow rate in excess of the rate of consumption of air by the air motors62aand62bat their maximum speed of operation and at the maximum desired compressor discharge pressure. In that case, as the slave air storage tanks82aand82bare being refilled (when their pressures hit the desired low pressure limit Pmin), the rate at which compressed air is added to the slave air storage tanks82aand82bby compressor78will exceed the rate at which air is consumed by the air motors62aand62bso that the amount of air in the master80a/80band slave82a/82btanks will increase until the slave air storage tank82aand82bpressures read the desired upper limit Pmax.

The slave air storage tanks82a,82bare maintained at a pressure that varies between a first selected value (the predefined minimum pressure (Pmin)) and a second selected value (the predefined maximum pressure (Pmax)). If air is flowing to the air motors62aand62b,the pressure in the master air storage tanks80aand80bwill be less than the pressure in the slave air storage tanks82aand82b.The air pressure in the slave82a,82band master80a,80btanks will be significantly higher than the pressure required at the air motors62aand62bbecause it is desirable to maximize the amount of air with which the master tanks80a/80band slave tanks82a/82bare pre-filled while still regulating the air flow rate to air motors62aand62bso that the watercraft10speed may be controlled. In order to regulate the air flow rate to the air motors62aand62b,the pressure must be reduced significantly from the pressure in storage tanks80a/80band82a/82b.In the first instance, pressure drop valves84aand84bdrop the air pressure significantly. In addition, however, pressure regulators86aand86b(fixed or adjustable valves that drop the air pressure) are provided downstream of the master air storage tanks80aand80b. Master air storage tank discharge line110ais connected to regulator86aand master air storage tank discharge line110bis connected to regulator86b.The regulators86aand86bcontrol the inlet air pressure to pneumatic control unit69. In certain examples, the regulators86aand86bcontrol the control unit69inlet pressure to from about 80 psig to about 120 psig, preferably from about 90 to about 110 psig, and more preferably from about 95 to about 105 psig. In one specific example, 100 psig is used.

The pneumatic control unit69includes compressed air discharge lines68and70. The air pressure supplied to air motors62aand62bvia discharge lines68and70is adjustable using throttle72. Compressed air discharge line68is a forward line that is connected, preferably in parallel, to air motor forward rotation inlet port64aof air motor62aand air motor forward rotation inlet port64bof air motor62b.Compressed air discharge line70is a reverse line that is connected, preferably in parallel, to air motor reverse rotation inlet ports66aand66bof air motor62bOne or more internal air control valves within control unit69adjust the air pressure in discharge lines68and70based on the throttle72position. The throttle72includes two levers which can be manipulated to cause the watercraft10to go forward and in reverse by causing air to be selectively supplied from forward line70or reverse line68(i.e., the throttle72is operable to adjust the air flow rate and propeller rotational direction). Supplying air to the air motor forward rotation inlet ports64aand64bcauses gears in air motors62aand62bto rotate in a first direction, which in turn causes propellers52aand52bto rotate in a first direction about the propeller shaft length axes l, propelling the watercraft10forward. Supplying air to air motor reverse rotation air inlet ports66aand66bcauses gears in air motors62aand62bto rotate in a second direction, which in turn causes propellers52aand52bto rotate in a second direction about the propeller shaft length axes l, propelling watercraft10in reverse. The levers on throttle72are manipulable to rotate the propellers52aand52bin forward and reverse from a speed of zero to the maximum rate of rotation of the air motors62aand62b.In one example, the supply pressure to the air motors62aand62branges from 0 to 100 psig, which corresponds to a propeller rotational frequency of from 0 to about 400 rpm.

Throttle72includes wires98aand98band/or suitable electronic components which send a control signal to the control unit69to cause control unit69to adjust the controller discharge pressure in lines68and70via internal air control valves. Thus, the master air storage tanks80aand80bare in fluid communication with the air motors62aand62bvia the pressure regulators86aand86band the air control valves in the control unit69. In certain examples, the compressed air pressure in compressed air discharge lines68and70ranges from 0 to about 100 psig.

Control unit69is also operatively connected to indicators74and76. Indicators74and76provide a visual indication of the frequency of rotation of each propeller52aand52b(e.g., RPM) based on appropriate instruments connected to the propeller shaft assemblies46aand46bor the air motors62aand62b.Indicator lines100aand100bprovide electrical signals necessary to operate the indicators74and76and are in electrical communication with air motors62aand62bor other devices used to indicate the speed of rotation of the shaft assemblies46aand46b.

Air compressor78(and an auxiliary compressor, if provided) is preferably capable of being powered by battery power. A plurality of batteries92a,92b,94a,and94bare provided to supply electrical energy necessary to operate air compressor78. The positive terminals of batteries92aand94aare connected to a power distribution panel88via electrical connection lines102aand102b,respectively, and the negative terminals of batteries92aand94aare connected to ground. The positive terminals of batteries92band94bare connected to power distribution panel88via electrical connection lines103aand103b,and the negative terminals of batteries92band94bare connected to ground. The power distribution panel88is connected to a positive terminal of the air compressor78electric motor via connection113aand to a negative terminal of the air compressor78electric motor via connection113b.The power distribution panel88selects one from among the four batteries92a,94a,92b,94bat a time to supply power to compressor78.

The batteries92a,94a,92b,94bare preferably rechargeable and are each preferably capable of supplying the energy needed to cyclically operate compressor78. Suitable examples include lithium iron phosphate batteries. The batteries92a,94a,92b,94bare preferably selected to provide a voltage compatible with the requirements of the compressor78motor and a capacity sufficient to ensure that electric power is sufficient to allow watercraft10to remain at sea for a desired period at a desired speed without recharging. In one example, four (4) size 8D lithium iron phosphate batteries supplied by RELi3ON® of Fort Mill, S.C. are used. The batteries92a,94a,92b,94bare connected to a recharging panel90via recharging lines104a,104b,106a,and106b.Recharging panel90is connected to a plug96for connecting recharging panel90to a dock power source. When watercraft10is in port, plug96may be connected to a power source to recharge batteries92a,94a,92b,and94b.As indicated previously, in the case of ship200,512batteries are shown. The particular size, weight, and energy capacity of the batteries may be selected based on the weight of ship200, the expected cargo load, the desired maximum draft, and the expected electrical load to run the ship's electrical systems as well as based on the expected variations in list and trim that the battery ballast system211is expected to encounter. Exemplary masses of individual batteries292, include masses of at least 40 lbm, at least 60 lbm., and at least 80 lbm, and at the same time masses of not more than 200 lbm., not more than 175 lbm., and not more than 150 lbm.

In certain examples, the kinetic energy of the rotating propeller shaft assemblies46aand46bis converted to electrical energy for use by other electrically-powered systems onboard watercraft10. In one implementation, alternators58a,58b,60a,60bare connected to each shaft assembly46aand46band convert a portion of the rotating shaft kinetic energy to electrical energy. The electrical current supplied by the alternators58a,58b,60a,60bis then supplied to the power distribution panel88. The power distribution panel88can then supply the current to recharge accessory batteries used to run lights, horns, radios, etc.

In certain implementations, propulsion system40is used to retrofit a watercraft10, from which an existing fossil fuel engine and fossil fuel tanks have been removed. In certain implementations, the components forming the propulsion system40allow watercraft10to remain at sea longer than the watercraft10with the fossil fuel engine and fuel tanks while weighing significantly less than the removed fossil fuel tanks and engines, fossil fuel, and engine. In certain examples, additional batteries such as batteries92a,94a,92b,and94bmay be installed and used both as ballast and as a source of additional electricity, allowing watercraft10to remain at sea even longer. In such cases, each battery92a,94a,92band94bis preferably selectively positionable along one or both of a watercraft length axis and a watercraft width axis.

In a preferred example, a large number of batteries92a,94a,92b,and94bare provided, and each battery serves as one of the ballast batteries292in3A-3B and4-5. In one example, each battery92a,94a,92,94bis a standard truck battery. In accordance with the preferred example, the ballast system211is designed to selectively electrically connect any number of the batteries92a,94a,92b,and94bto power distribution panel88and a power grid that is operatively connected to compressor78and any other battery-powered components so that any combination of batteries92a,94a,92b,and94bmay be used. In such cases, carriage assemblies such as carriage assemblies214-244are provided and are designed with conductive pathways so that when any given slot is occupied by a battery92a,94a,92b,94b,that battery can be selectively connected to the power grid and power distribution panel88to provide power to whatever accessories or equipment need battery power.

A method of operating watercraft10will now be described. Watercraft10is initially docked. Compressed air storage tanks80a/80band82a/82bare filled with air until the slave air storage tanks82aand82breach their desired maximum pressure Pmax. As air motors62aand62bare initially off, the master tanks80aand80bwill be at the same pressure as their respective slave tanks82aand82b.In the case of NUVT4500 tanks, the maximum pressure is the service pressure of 4500 psig. At this point, pressure regulators86aand86bare set to supply a desired air pressure (e.g., 100 psig) to control unit69supply lines112aand112b.However, internal valves in control unit69are closed and supply no air to the air motors62aand62b(e.g. 0 psig). Batteries92a,94a,92b,94bare fully charged. After unmooring the watercraft10, throttle72is actuated to transmit air pressure via forward rotation line68to air motor forward rotation input ports64aand64b,with the position of the throttle corresponding to both the pressure in forward rotation line70and the rotational frequency of propellers52aand52b.Batteries92a,92b,94a,94bare aligned along the length and width axes of watercraft10to provide the desired trim and list at the start of the journey. Fresh water tank346also preferably has an amount of water which, when combined with the battery and carriage assembly weights, provides an initial desired amount of total ballast.

After the journey has progressed for a period of time, the air pressure in slave air storage tanks82aand82bdrops to a first selected value, the desired minimum pressure Pmin. At this point, a controller in the power distribution panel88electrically connects one of the batteries92a,94a,92b,94bto an electric motor that drives compressor78and/or activates the electric motor that runs compressor78. Compressor78intakes and compresses ambient air, causing it to flow to the slave air storage tanks82aand82band then into the master air storage tanks80aand80b.Alternatively, the regulators86aand86bcan be configured and/or controlled to allow only one tank pair80a/82aor80b/82bto be used at any one time. Once the pressure in the slave air storage tanks82aand82breaches a second selected value, the maximum desired pressure Pmax, the compressor78is turned off (such as by discontinuing the supply of electric power from power distribution panel88). If the pressures in slave air storage tanks82aand82bare different, the system may be configured to turn off compressor78when either slave tank82aor82breaches the maximum desired pressure Pmax. While the system could be configured to keep the compressor78running until both slave tanks82a,82breach Pmax, it is preferred to turn the compressor78off when one of them reaches Pmaxto prevent overfilling if one of the pressure sensors or switches fails.

This process of cycling the compressor78on and off as the pressure drops and rises in the slave tanks82a,82bis repeated. Eventually, the currently operative battery from among batteries92a,94a,92b,94bdrops to a potential difference that is low enough to cause the controller in the power distribution panel88to place another one of the batteries92a,94a,92b,94bin electrical communication with the motor in compressor78. Moreover, during the entire journey, no fossil fuels are consumed and no carbon dioxide, carbon monoxide, water, NOx, SOx or other pollutants are emitted.

If it is desired to adjust the trim of the watercraft10, one or more of the batteries92a,92b,94a,94bmay be moved along the length axis of the watercraft10. If it is desired to adjust the list of the watercraft10, one or more of the batteries92a,92b,94a,94bmay be moved along the width axis of the watercraft10. In examples in which the watercraft10is a larger ship such as ship200, additional batteries would be provided in the manner described previously for ballast batteries292ofFIGS.3A-3B,4, and5. If the overall draft of watercraft10needs to be reduced, ballast controller400or any of the other techniques previously described may be used to expel potable water overboard via overboard line411. Conversely, if more draft is required, the flow rate of sea water into the potable water treatment system340may be increased by increasing the setpoint of flow controller353or using any of the other techniques previously described to increase the level in tank346.

EXAMPLE 1

A 1972 Luhrs Sport Fishing Boat weighing approximately 19,000 lbs. is provided. The boat includes two Chrysler 318 cc engines. Including the reverse and reduction gears, the engines weigh approximately 900 lbs. each. Two 75 gallon gas tanks are also included, which collectively weigh about 250 lbs. empty. 150 gallons of gasoline weighs approximately 1,100 lbs. Thus, the total weight of the gasoline engines, gas tanks, and gasoline is about 3150 lbs. The boat is retrofitted with a propulsion system in accordance with propulsion system40ofFIG.2.

The Chrysler engines, the gas tanks, and the gas are removed from the vessel. Four Nuvair NUVT4500 compressed air storage tanks are installed in the vessel, each of which has an empty weight of about 145.5 lbs.

Two GAST 1UP-NRV-15 rotary air motors are installed as shown inFIG.2. One commercially available main compressor weighing about 800 lbs. and two commercially available auxiliary compressors weighing about 400 lbs. each are also installed. The compressors are selected to have a maximum discharge pressure of about 4500 psig and to supply a flow rate or air to both air tanks80a,82a,80b,and82bwhich exceeds the amount of air consumed by air motors62aand62bwhen watercraft10is at a cruising speed of 15-18 miles per hour. The weight of each motor62aand62bis approximately 25 lbs. Twelve RELi3ON® lithium iron phosphate 12V, size 8D batteries weighing approximately 83 lbs each are installed. The boat has an existing control panel and power distribution panel which are rewired and outfitted with pneumatic lines for use with air motors.

The retrofitted components weigh about 220 lbs more than the removed components. However, prior to retrofitting, when watercraft10is cruising at a speed of about 15-18 miles per hour, it consumes about 7 gallons of gasoline per hour, which will exhaust the full 150 gallon fuel supply in about 21.4 hours. In contrast, each of the 12 lithium iron phosphate batteries is estimated to be able to run the main and auxiliary compressors for 72 hours continuously, even though in operation, the compressors will only be run periodically (i.e., when the slave tank82a,82bpressures fall below Pmin). With 12 lithium iron phosphate batteries of the type described above, even if the main and auxiliary compressors were operating continuously, the air motors could be operated continuously for about 36 days (874 hours) while moving watercraft10at a speed of about 15-18 miles per hour through the water. Thus, air propulsion systems in accordance with the present disclosure provide the ability to stay at sea for more than 30 times as long as a fossil fuel engine and fuel system sized for the same watercraft.

If only one of the twelve (12) lithium iron phosphate batteries were used, watercraft10could still remain at sea more than three times as long with the air propulsion system of the present disclosure than with the replaced fossil fuel system and the retrofitted watercraft10would weigh over 650 lbs. less than the original watercraft. Thus, it has surprisingly been discovered that not only can air propulsion systems built in accordance with the present disclosure avoid the burning of fossil fuels, but they can allow the watercraft to remain at sea far longer than fossil fuel engines.

It has also been discovered that adding lithium iron phosphate batteries also helps maintain the list and trim of the watercraft10. In accordance with this example, the lithium iron phosphate batteries are selectively positionable along the length and width axes of boat, preferably using a carriage system similar in design and smaller in size to ballast system211ofFIGS.3A-B,4and5. If the watercraft10shows a positive trim by stern (FIG.1), one or more of the12lithium iron phosphate batteries would be moved along the watercraft's length axis toward the bow to reduce the trim by stern. Conversely, if the watercraft10shows a negative trim by stern, one or more of the lithium iron batteries would be moved along the length axis toward the stern to increase the trim by stern.

Referring toFIG.2B, in the case of a list angle that is positive in the clockwise direction when viewing the stern of watercraft10in a direction toward the bow of watercraft10, one or more of the lithium iron phosphate batteries would be moved along the width axis of the watercraft10toward the port side of the watercraft10. Conversely, if the watercraft10has a negative list angle in the clockwise direction when viewing the stern of watercraft10in a direction toward the bow, one or more of the lithium iron phosphate batteries would be moved along the watercraft10width axis toward the starboard side of the watercraft10.

EXAMPLE 2

An example of a large ship having a 112 foot beam with a battery ballast system like battery ballast system211ofFIGS.3A-3Bwill now be provided. 100 carriage assemblies similar to carriage assemblies214-244are provided and located in the lower deck210. Each carriage assembly has eight (8) tiers arranged along the ship's height axis H. Each battery support in each carriage assembly (e.g., battery support271) has a length along the ship's length axis of 4 feet, a width along the ship's width axis of two (2) feet, and is spaced apart from is vertically adjacent neighbors by two (2) feet. 100 feet of the ship's 112 foot width is available for carriage assemblies. Thus, there are 100/2=50 slots (e.g., H(1)-H(50)) comprising each tier of each carriage assembly. Each tier has 32 batteries and battery supports occupying 32 of the 50 slots. Each battery weighs 150 pounds, and the average weight per slot (accounting for the fact that 18 slots do not have a battery support271in them) is 20 pounds. Thus, the battery weight per tier of each carriage assembly is 150 lbs.×32 batteries/tier=49,800 lbs./tier. The slot weight per tier (without batteries) is 20 lbs./slot×50 slots/tier=1,000 lbs./tier. Thus, the weight of each tier including batteries is 50,800 lbs. or 25.4 tons.

Each carriage assembly has eight (8) tiers, bringing the total weight per carriage assembly to 8 tiers/carriage assembly (25.4 tons/tier)=203.2 tons/carriage assembly. The total weight of the entire battery ballast system is then 100 carriage assemblies×203.2 tons/carriage assembly=20,320 tons. A potable water system is also provided and includes a fresh water tank having a rectangular prism shape with a length of 200 feet and a cross-section of 50 feet by 14 feet, yielding a volume of 145,600 cu. ft. The weight of potable water for such a tank is 145,600 cu. ft.×62.4 lbs./cu. ft.=4542 tons.

In certain examples, the potable water tank is designed to provide an amount of ballast water capacity beyond that which is needed to satisfy the expected maximum consumption of potable water on the ship. As explained previously, the battery ballast can be used to adjust the ship's list and trim, but batteries cannot be selectively added or expelled from a ship at sea. In one example, the potable water tank is sized to hold the maximum required volume of potable water required for shipboard consumption over a specified period of time and to ensure that the ship's waterline does not vary by more than a desired amount when the cargo loading varies between the minimum and maximum expected load. Based on known relationships between the gravitational force on the ship (i.e., the weight expressed as a force), the buoyancy force exerted by the body of water, and the maximum desired variation in the waterline, a maximum allowable change in the ship's mass can be calculated. This variation will correspond to a maximum change in the mass and volume of ballast water held in the potable water tank and the cargo weight. If it is desired for the ship to handle greater swings in cargo mass while staying within the maximum desired waterline variation, additional potable water tank capacity may be provided so that the mass of the potable water allocated to ballast is adjusted accordingly. For example, if the ship's maximum waterline variation is 20 feet, a corresponding change in total ship mass may be calculated which corresponds to that water-line variation. That maximum weight variation may be allocated as follows:
ΔMT=ΔMC+ΔMB(7)wherein, ΔMT=Total change in ship mass corresponding to maximum allowable waterline height variation (lbmor kg)ΔMC=maximum expected variation in cargo mass (lbmor kg); andΔMB=maximum variation in mass of ballast (lbmor kg).

Because the mass of the battery ballast will not change at sea, ΔMBmay be used to calculate the incremental potable tank volume required to accommodate the maximum desired cargo and waterline variations using equation (3), above.

The present invention has been described with reference to certain exemplary embodiments thereof. However, it will be readily apparent to those skilled in the art that it is possible to embody the invention in specific forms other than those of the exemplary embodiments described above. This may be done without departing from the spirit of the invention. The exemplary embodiments are merely illustrative and should not be considered restrictive in any way. The scope of the invention is defined by the appended claims and their equivalents, rather than by the preceding description.