THE INVENTION

Gulf Stream Turbine’s Unique Design

U.S. Patent 6,531,788 is for a submersible power plant that is a unique concept for a self-supporting structure that utilizes the unchanging laws of physics to maintain stability and control operating depths.  It uses a system that depends on no moving parts to balance the lifting forces to the changing downward vector forces that result from the changes in drag acting through the downward-angled anchor line.  To neutralize the torque that would otherwise roll a tethered generator in the direction opposite to that of a turbine’s rotation, each machine has two turbines and generators that rotate in opposite directions so that the torque produced by one turbine is neutralized by that of the other.

The Gulf Stream Turbine’s two generators and gearboxes are housed in watertight, rear-facing nacelles that are located below and to each side of a torpedo-shaped buoyancy tank that extends fore and aft.  The weight of the generators and gearboxes serve as ballast to get the structure’s center of gravity far below its center of buoyancy.  The Gulf Stream Turbine is the only underwater generating plant that obtains most of its stability by locating its center of gravity far below its center of buoyancy.  (This principal provides stability for blimps, hot-air balloons, submarines, self-righting lifeboats, and sailboats with weighted keels.)  The invention is based on the relative positions of buoyancy and weight and on unique methods of balancing forces.  The actual conversion of the water’s kinetic energy into electricity uses the same technology that is used by the wind-turbine industry. 

The following drawings show a Gulf Stream Turbine equipped with fixed, full-bladed rotors. These full-bladed rotors could be the best choice if the current velocities remained within a relatively narrow range.  If the current should get too strong, a torque-limiting device could be used or the connection from the grid to the stator would be cut to allow the rotors to spin at high speed while producing no power.           

    


Why Gulf Stream Turbines Should Be Made of Carbon-Fiber Composites

            Although it would be possible to build the Gulf Stream turbines using steel or aluminum, there are several reasons why the best choice of materials would be carbon-fiber-reinforced composites, along with other less-expensive plastics.  Carbon fiber has a very low density and great strength. If the turbines’ blades were made of carbon-fiber-reinforced material, they would weigh only a fraction of what they would weigh if made of steel, aluminum, or bronze (often used for boat propellers because of its resistance to corrosion).  A cubic foot of steel or iron weighs about 498.84 pounds; a cubic foot of aluminum weighs about 168.5 pounds, and a cubic foot of bronze weighs about 548 pounds.  In contrast, a cubic foot of solid carbon fiber weighs about 106 pounds.  However, because the salt water being displaced by these materials weighs 64 pounds per cubic foot, the buoyancy requirements would differ by far more than the differences in those unsubmerged weights.  If there were five 50-foot turbines, each made of one of the five materials listed in the following table, each having a volume of 84 cubic feet, each would have the following weights on land and when submerged:

 

 

Comparing Densities of Carbon Fiber to Metals

 

 

 

                     weights are in pounds

 

 

 

 

 

  wt/cu.ft.

 wt. on land

 wt. in water

 

steel

 

489.84

      41,143

       35,767

 

aluminum*

168.48

      14,150

         8,774

 

bronze

 

547.87

      44,507

       39,131

 

carbon fiber (solid)

106.08

        8,908

         3,532

 

carbon fiber (honeycomb)

64

        5,376

0

 

 

 

 

 

 

 

 

 

(*Because the aluminum is much weaker than the other materials, it would

 

 

require thicker blades than those made of the other materials.  No allowance

 

 

has been made for this in the table.)

 

 


If the rotors were made steel, two of them would weight 82,286 pounds.  To support that weight would require an additional displacement of 1,285.72 cubic feet – not including the additional displacement needed to support the bigger and heavier structure.  The use of carbon-fiber-reinforced composites for the rotors would not only reduce the displacement requirements of the buoyancy tank, it could eliminate the vertical loads on the turbines’ bearings.  If the turbine rotors had sufficient honeycomb or syntactic foam to give them a specific gravity near that of the salt water that they displaced, the only loads on the bearing and gearboxes would come from the current pushing longitudinally against the rotors.      

            Although carbon fiber’s lightness and strength provide two excellent reasons for using this space-age material for these underwater generators, it offers yet another advantage that is perhaps even more important: carbon-fiber composites will not corrode.  All metals have a natural tendency to deteriorate into the primeval state in which they are found in the earth.  Iron for instance reverts to iron oxide.  An electric current is the prime mover in all forms of metallic corrosion.  Ions of a metal dissolve into the salt water electrolyte.  The electrons that remain behind travel through the metal to a dissimilar area where they recombine with other ions to form oxides and release hydrogen.  This causes the metal to waste away.

            Every metal has its own electrochemical potential and reacts to corrosive actions at its own tempo.  Nobel metals, such as platinum and gold, are extremely resistant.  The base metals, such as magnesium, corrode very quickly.  In between these extremes are the metals of most practical importance: iron, steel, aluminum, lead, copper, and bronze.

            In addition to the corrosion that is caused by the electrochemical reaction between different metals in the presence of an electrolyte, corrosion can also be caused by electrolysis.  The difference between the electrochemical corrosion and that caused by electrolysis is that the latter is caused by electricity from an outside source, either directly or through induction.  Although separating a metal from the electrolyte with waterproof coatings can prevent corrosion, only a small break in that coating is required for that corrosion being caused by electrolysis to be concentrated at that one point.  The result is that electrolytic corrosion can actually eat a hole much faster through a coated metal with a small break in that coating than it can through metal that has not been coated at all.  This is because, if the metal is fully exposed to the saltwater electrolyte, the electrolysis causing the corrosion will be spread over a much larger area.  Because the Gulf Stream turbines will be generating electricity, the potential for corrosion caused by electrolysis from induced currents would be great.

            Because the corrosive effects of salt water and electrolysis will not effect carbon-fiber composites and other plastics, their use would eliminate the need for the generating units to be periodically removed from the water for scraping and painting.  The plastics would also eliminate the need to scrape and paint the interiors of the buoyancy tanks.         

            The fabrication of the rotor blades can be done using new manufacturing methods that can minimize their cost.  The Gulf Stream Turbine’s rotor blades can be fabricated using the same technology that is now being used by California’s Foam Matrix Company to build wings for Boeing’s X-45 unmanned fighter jet.  Instead of using several tooling machines, foam material is poured into a large molding block.  After curing, the core is wrapped in composite fibers and then placed back into the mold and cured with resin to form the wing’s skin.  This process eliminates about 20 steps, while making a wing that is both lighter and stronger.  With this patented process, the Foam Matrix Company can produce an X-45 wing in just one day – not the several weeks it would take to construct a similar wing out of composites using conventional methods.  Using this method, it would be possible to efficiently manufacture lightweight rotor blades, using syntactic foam or honeycomb to reduce the blades’ densities to that of the water they will displace.  When all factors are considered, this space-age material would prove to be most economical choice for those parts that require great tensile strength.  For all other parts, including much of the buoyancy tank, fiberglass and other less costly plastics can be used.

Placing the Center of Buoyancy above the Center of Gravity

            Every floating object has a center of buoyancy and a center of gravity.  The center of gravity is located at that point where the total weight of an object balances so that, if it were suspended in air from that point in any position, it would not rotate.  The center of buoyancy is at the center of gravity of that water that the floating object displaces.  A fully submerged, free-floating object will always float with its center of gravity directly under its center of buoyancy.  Because the Gulf Stream Turbine’s center of gravity is located far below its center of buoyancy, it provides a powerful righting moment to keep the unit level.


In the preceding drawing, the location of the center of buoyancy is indicated by the green dot at the bottom of the buoyancy tank, and the center of gravity by the lower blue dot.  If a unit tips, the righting moment would equal the length of the righting arm (horizontal blue line projecting to the right from the blue dot to the red line that extends vertically downward from the center of buoyancy), multiplied by the machine’s weight.  The length of this righting arm equals the distance between the centers of gravity and buoyancy, multiplied by the sine of the angle of tilt.  For any given weight and angle of tilt, the righting moment would be proportional to the distance between the center of buoyancy and the center of gravity.  If that distance were doubled, the righting moment for any angle of tilt would also be doubled.  

 

RM = Wt x RA    or   RM = Wt x D x S

 

 

 

RM = righting moment

 

 

Wt = weight of unit

 

RA = righting arm

 

 

S = sine of angle of tilt

 

D = distance between centers of gravity and buoyancy

 

 

Other Features That Further Improve Stability

Although the vertical separation between of the center of gravity and the center of buoyancy is the most important principle of physics that provides the Gulf Stream Turbines with its great stability, the invention has other features that add still more to that stability.  For example, the hydrofoils are on the buoyancy tank, placing their lifting forces also far above the center of gravity.  Also, the hydrofoils can have substantial dihedral.  This would further increase the stability because the lower hydrofoil of a tipped machine will produce more lift than the raised hydrofoil.  In addition, having the anchor line’s attachment point, with its downward vector force, located far below those lifting forces will add still more to that stability.  And lastly, the placement of the vertical and horizontal tail fins at the rear of the buoyancy tank places the structure’s centers of lateral and vertical resistance far behind the anchor-line’s attachment point.  This will prevent yawing and pitching, and keep the structure facing into the current. (The center of lateral resistance is that theoretical point from where an applied force could move the structure sideways without it rotating.  The center of vertical resistance is that theoretical point from which a force could move the structure vertically without it rotating.)

The Buoyancy Tank


            The above schematic drawing is of the buoyancy tank for all versions of the invention, with the exception of a fully automatic version that will be described later.  At the top of each bulkhead there is a vent to allow air to flow between the compartments to keep the pressures equal.  The hatches at the top of each compartment are through which metered water can be pumped for the initial submersion.  There are lines (124) through which air and water can flow to and from the compartments, should adjustment of the buoyancy be required after the unit is submerged.  The valves (123) for these lines are located in the bottom of the buoyancy tank, behind the rotors.  Because the current will be faster than what a SCUBA diver can swim, a wet sub will be required to transport any divers to submerged machines.  The compartments contain baffles (126) to reduce the longitudinal weight shifting caused by the ballast water sloshing back and forth.

Downward Vectored Forces Must Be Balanced  

            Depending on the downward angle of the anchor chain, the downward vectored forces produced by the horizontal drag from a generator unit producing power could be considerable.  As the angle of the anchor chain increases from the horizontal, that downward force increases as a percent of the unit’s total horizontal drag.  If the unit were prevented from moving lower and the horizontal drag were equivalent to 1,000,000 foot-pounds per second, the downward forces and the pounds of pull on the anchor chain would increase as the chain angle increased as follows:   

 

How Downward Vector Force Increases with Anchor-Line Angle

 

 

anchor line

vector force as

ft-lb./sec

ft-lb./sec of

anchor line

 

chain angle

percent of unit’s

downward

pull on the

length/100 ft.

 

in degrees

horizontal drag

vector force

anchor line

above bottom

 

0

0.000%

0

    1,000,000

             na

 

5

8.748%

         87,480

    1,003,830

             1,147

 

10

17.633%

       176,330

    1,015,430

                576

 

15

26.795%

       267,950

    1,035,280

                386

 

20

36.397%

       363,970

    1,064,180

                292

 

25

46.631%

       466,310

    1,103,380

                237

 

30

57.735%

       577,350

    1,154,700

                200

 

35

70.021%

       700,210

    1,220,770

                174

 

40

83.910%

       839,100

    1,305,410

                156

 

45

100.000%

    1,000,000

    1,414,210

                141


            A generating unit operating in a current with a velocity of 5.5 mph would have a frontal resistance of between 921,382 and 1,214,440 foot-pounds per second.  If that resistance were halfway between those two numbers, it would be 1,069,000 foot-pounds per second.  (I have been using the word “force” for a measure of foot-pounds per second, which is actually a measure of power.  Force is in pounds; work is in foot-pounds, and power is in foot-pounds per second.)

            The downward vector force increases in the same proportion as the tangent of the anchor line’s downward angle where it attaches to the unit.  If the anchor line’s downward angle remains constant, the downward vector force will increase in the same proportion as the kinetic energy, increasing with the cube of the current’s velocity.  To prevent this increasing downward force from pulling a unit to greater depths, that downward force must be balanced with an equal and opposite lifting force.  This can be done by either increasing the unit’s buoyancy, by using hydrofoils to provide additional lift, or by a combination of both.  If the downward force is not equalized, the unit will be pulled down to that depth where the angle of the anchor chain’s pull will be reduced sufficiently so that the resulting downward vector force will equal the upward force being provided by the buoyancy and hydrofoils.  The forces would then be in equilibrium and the unit would remain at that depth – as long as there were no changes in the current’s velocity or in the demand for electrical power.  Increasing either would increase the horizontal resistance and cause the unit to descend still lower.  Likewise, if the load on the generator is reduced, the turbine’s rotors will turn with less resistance – thus producing less drag and a reduction in the downward vector force that would result in the unit rising to a higher level.   

Hydrodynamic Lift to Neutralize the Downward Vector Force

            It is important to understand that a Gulf Stream Turbine uses its hydrofoils for a very different purpose than for what an airplane uses its wings.  An airplane uses its wings to oppose the downward forces that are produced by its weight – the Gulf Stream Turbine uses the unchanging lifting forces from its buoyancy to support the weight, and use its hydrofoils’ changeable lifting forces to balance those changing downward vector forces resulting from the drag acting on the downward angled anchor line. 

To better understand the Gulf Stream Turbine’s design, it helps to understand how wings and hydrofoils produce lift.  The lift from an airfoil-shaped fin’s lower-surface can be explained by Newton’s first and third laws of motion that relate to why deflecting a fluid downward results in a corresponding upward force that we call lift.  Newton’s first law states that a body in motion will continue to move in a straight path unless it is acted upon by some exterior force.  The bottom surface of the airfoil-shaped fin changes the fluid’s direction by deflecting it downward.  Newton’s third law states that for every action there must be an equal and opposite reaction.   The force required to deflect the water downward imparts an equal and opposite force that pushed up on the underside of the wing or hydrofoil.  

An entirely different principal produces a fin’s upper-surface lift.  The Bernoulli’s Theorem explains why the pressure of a fluid flowing over a surface decreases with increasing velocity. Because the fluid flowing over the curved top of an airfoil-shaped fin travels farther than that flowing under that fin, it must flow faster.  It is this difference in velocities that produces the lower pressures above a hydrofoil than below it – and it is this pressure imbalance between the fin’s upper and lower surfaces that provides the lift.

When an airplane is flying at high speed, it is possible for its wing to have a zero angle of attack when nearly all of the lift is developed by the airfoil’s upper surface.  If we decrease the angle of attack, the lift will diminish until finally an angle is reached at which point the airfoil will exert neither an upward nor a downward force.  An airplane’s wing would pass through the air with a zero lift if there were no downward loads being imposed on it.  The angle of attack that an airfoil assumes during steady flight is always the one that produces just enough lift to counteract the opposing downward force from the plane’s weight.  When an airplane slows, its wing must approach the air at increasing angles of attack to provide enough lift to support the plane’s unchanging weight.  If the wing’s angle of attack becomes too great for the air to maintain a smooth laminar flow over its upper surface, the wing will stall, the lift will be destroyed, and there will be a large increase in drag.

As previously stated, unlike the airplane, the Gulf Stream Turbine will use its buoyancy to support its weight and its hydrofoils to provide the hydrodynamic lift to balance those downward vector forces produced by the horizontal drag acting through the downward-angled anchor line.  By keeping the lifting and downward forces balanced, the Gulf Stream Turbines can remain at the same depth.

As long as a fin’s angle of attack remains the same and a laminar flow is maintained, both the lift and drag will increase with the cube of the fluid’s velocity.  And, as long as the downward angle of the anchor line at the attachment point remains the same, the downward vector forces will also remain proportional to the cube of the velocity.  

Why the Different Versions of the Gulf Stream Turbine

            The patent includes several versions of the Gulf Stream Turbine that use different methods for balancing the hydrofoil’s lifting forces to the changing downward forces produced by the changes in drag. The principal reason there are these different versions is that, when I applied for the patent I had no assurance that the US Patent Office would approve key claims that would cover them all.  Happily, they did.  Though all of the patented embodiments would work, some have advantages over others.  Since applying for the patent, I have added features that – though not patented – are dependent on the original patent. 

Balancing the Lifting Force With a Low Anchor-Line Hitch Point. 

If the downward angle of the anchor line at the attachment point remains the same, the downward vector force will remain proportional to the drag and the drag will be proportional to the cube of the current’s velocity.   That means that, if the submersible power plants are to remain at the same depth in changing current velocities and with changing generator loads, the hydrofoils’ lifting forces must balance those changing downward forces.  All of the versions of the Gulf Stream Turbine can do that.

The center of frontal resistance is that point where all the drag forces are balanced so that, if the structure were to be towed from that point, it would move forward without rotating. The simplest method to balance the changing downward vector forces is to have the anchor-line’ attachment point located below the structure’s center of drag.  Then, if an increase in the horizontal drag should cause an increase in the downward vector force, the increased pull on the low anchor-line attachment point will rotate the entire machine, raising its nose and dropping its tail.  This rotation will increase the angle of attack of the attached hydrofoils, which will increase their lifting force to remain in balance with the increasing downward vector force.  The beautiful thing about this system is that it utilizes the same changing forces that produce the changing downward vector forces to balance those downward forces with opposite lifting forces.  Better yet, it does this without relying on a single moving part! 

In the following illustration, the green spot near the bottom of the buoyancy tank represents the adjusted center of buoyancy (with the ballast water distributed in the tank’s compartments).  The red spot is the center of gravity.  (Because that center is slightly
forward of the center of buoyancy, if there were no tension on the anchor line, the structure would float slightly nose down so that the blue line between the centers of gravity and buoyancy would be vertical.)  The blue dot represents the center of frontal resistance (drag).  The yellow line is the length of the lever arm produced by the low anchor-line hitch point that can rotate the entire machine to balance the hydrofoil’s lifting force to a changing downward vector force.  The anchor line is attached to a device that can be moved up or down to adjust the length of that lever arm.

The following side and bottom views are of an embodiment that permits the rotors to remain vertical in currents of any strength, thus eliminating those downward forces caused by the water striking the rotors while they are tilted backward.  Because this


feature would reduce the downward force, it would produce a net increase to the lifting force.  For this system to work, the rotors must be extremely light so that the submerged center of gravity of the pivoting portion (colored green) is directly under the pivot point.  (Details are in the patent.) 

Self-Adjusting Hydrofoil

            The previously described low-hitch-point system involves the rotation of the entire structure to adjust the angle of attack of those hydrofoils that are attached to the buoyancy tank.  Unlike that system that operates with no moving parts, the self-adjusting hydrofoil has one moving part.  An advantage of the self-adjusting system is that – like the previously described pivoting version – the turbines’ rotors will always remain vertical.  A disadvantage of the self-adjusting hydrofoils is that they would balance only those downward vector forces that are produced by changes in current velocity not those resulting from changes in the generators’ load. 

            In this system, the unit remains level and it is only the front pair of hydrofoils that rotates to adjust lifting forces.  Unlike the previously described system, the rear horizontal fins can be flat because their only purpose is to keep the unit level by preventing rotation.  Because the movable hydrofoils on the sides of the buoyancy tank must operate in unison, they are connected to each other by a shaft that extends through the tank at the adjustable hydrofoils’ pivot point.  To reduce the forces needed to adjust the hydrofoils, the fin’s surface areas ahead of the pivot point are nearly equal to those behind that pivot point so that those forces pushing on the front portion will almost balance those pushing on the rear portion.  A lever arm is attached to the hydrofoils at the pivot point and extends vertically upward.  To this arm is attached a flat plate that can be slid up and down the lever arm and secured at any point.  Also, affixed to the front edge of the movable hydrofoils is a rod that extends forward onto which a counter weight can be secured at any point.  The self-adjusting hydrofoils’ movement is restricted by a stop to prevent the hydrofoils from tipping too far forward in slow water.

       

In a weak current, the counter weight would more than balance the mass of the front of the hydrofoil with the mass of the rear portion to keep the front of the hydrofoil low to provide little or no lift.  With the movable plate on the lever arm properly positioned – as the current increased, increasing that downward force that would pull the unit deeper – the increasing kinetic energy of the water pushing back against the plate on the lever arm would push that arm rearward, causing the hydrofoils to rotate to increase their angle of attack.  This would increase the upward lifting force to neutralize the increased downward force resulting from the current’s greater velocity.  These self-adjusting fins would be located on the sides of the buoyancy tank.  Because there would be no physical connection with the buoyancy tank that would interfere with a fin’s ability to adjust their angle of attack to the current flow, they can be located forward of the structure’s centers of gravity and buoyancy.  By locating the fins there, they will be able to change the lifting force while allowing the unit to remain in level trim.  For these self-adjusting hydrofoils to work properly, the anchor line should attached to the unit in front of the center drag, high enough so that the changes in drag will not cause any vertical rotation of the entire unit.  The system is controlled by balancing leveraged forces, which can be adjusted by changing the location or size of the plate on the vertical lever arm, by moving the weight that is secured to the rod that projects forward from the hydrofoil, and by adjusting the height of the anchor line’s attachment point.  The amount of angle of attack required to balance the forces will depend on the hydrofoil’s surface area.

Bottom Weights for Controlling Depth

The low-hitch-point and the self-adjusting-hydrofoil systems should work well where the current always flowed at speeds that never dropped too low.  However, if the current slowed too much, the resulting weakened downward force could allow positive buoyancy to float the structure toward the surface.  The current speed when this might occur would depend on the amount of the lifting force that is being supplied by buoyancy and how much by the hydrofoils.  To minimize this possibility, the machines should have just enough buoyancy so that, if there were absolutely no current, only the tops of the buoyancy tanks’ rear ends would appear above the surface. 

Because of the Gulf Stream’s velocities should always exceed 3 mph, there should never be a problem of a properly adjusted Gulf Stream Turbine coming to the surface in that current.  This might not be true for a more uneven current, such as the Kuroshio.  The problem with the Kuroshio is not that of the current flowing too slowly, it is that its path is not as stable and its central axis could shift laterally away from the turbines.  One way to keep the Gulf Stream Turbines at controlled depths under all conditions would be to give them more positive buoyancy than otherwise and then use a weight on the bottom to restrict their height.  The next drawing shows a line fastened to the anchor line and to a weight on the ocean floor.



The above drawing shows an alternative to this system. Instead of attaching the line to the anchor line, attach it to the buoyancy tank’s nose.  This modification could use a much lighter bottom weight because, if an imbalance of forces tries to take the Gulf Stream Turbine above the desired operating depths, the downward pull on the nose would destroy the positive lift being produced by the hydrofoils and could even cause them to produce negative lift.  This simple system would keep the machine operating at the same depth – regardless of any the changes in the current’s strength or generator’s load.  This version could have a bit more buoyancy at the front of the buoyancy tank than the other versions, and the anchor line’s hitch point could also be set slightly lower.  The buoyancy adjustments would produce more lift to keep the machine as high above the ocean floor as the line would allow.  With the Gulf Stream Turbine operating at the top of the line, the harder the pull on that line, the more that line will pull down on the buoyancy tank’s nose.  Not only would the line pull down on the structure – it would do so in a way that would cut the hydrofoils’ lifting force to just that needed to keep the machine at the proper depth under all conditions.  This is an extremely simple, self-governing system that can keep the Gulf Stream Turbines at exactly the desired distance above the ocean bottom.  Not only is it simple – it requires no moving parts!


Automatic System Uses Water Pressure to Control Depth 

Gulf Stream Turbines will operate at various depths under the sea in strong currents.  Because they will not be readily accessible for servicing or repair, the fewer moving parts the better.  Even though I favor simplicity, the patent contains one embodiment of the invention that is completely automatic and, with the proper redundancy and quality control in its design and construction, it could be reliable.

Once the pressure controls are set and the unit is lowered into the water and the anchor and electric lines connected, this version of the Gulf Stream Turbine would automatically add the proper amount of ballast water and distribute that water among the buoyancy tank’s compartments to keep the machine perfectly level.  Then, while remaining level, the Gulf Stream Turbine would descend at a controlled rate to a pre-set range of depths where it would remain, regardless of changes in the current’s velocity or generator load.  This version could resemble the previously described version with the self-adjusting hydrofoils, except there would be nothing projecting from the adjustable fins.     

This automatic version has four separate elements: a buoyancy component, a leveling component, a water-return component, and a hydrofoil control component.  Both the buoyancy component and the hydrofoil control component include similar systems that limit the rates of descents and ascents to prevent the structure from oscillating in giant sine curves up and down through the desired depth range.  These two systems measure both the hydrostatic pressures and the rate that those pressures are changing.  A schematic of one of these systems appears below.   


The ambient pressure of seawater increases at the rate of .4444 psi per foot of depth.  That means if a unit is to operate at depths of between 100 and 110 feet, the pressure setting would be set with a low pressure limit of 44.4 psi and a high pressure limit of 48.9 psi.  A pressure control switch (102) is set to activate if the water pressure should get outside of the pre-set limits, closing the connection between the switch and either the rate-of-ascent switch (103) or the rate-of-descent switch (104).  These switches then activate their respective solenoid (116) and (117) to turn the reversible electric motor (109).  The motor rotates the hydrofoils to adjust their angles of attack until one of the following occurs: the rate of ascent or descent becomes adequate, the hydrofoils have rotated to their maximum angle, or the Gulf Stream Turbine has moved into the desired depth range.   The schematic shows that the structure is below the desired depths and is moving up at a satisfactory rate so that no additional fin rotation is required. 

The only difference between the depth control system for the hydrofoils and the buoyancy adjustment system is that the depth range for controlling the hydrofoils would be set much closer together within the depth range settings for buoyancy.  For example, if the hydrofoil controls were set for 44.4 psi (100 feet) and 48.9 psi (110 feet), the buoyancy might be set with a low 40 psi (90 feet) 53.5 psi (120feet).  This would reduce the possibilities of the ballast tank and plumbing becoming fouled by an infestation of marine flora and fauna.     

Seawater contains plankton that includes algae, and the eggs and larvae of marine invertebrates that include coral, sponges, barnacles, jellyfish, shellfish, and more.  The algae and other marine plants must receive light energy for their chlorophyll to photosynthesize carbon dioxide and water into carbohydrates. Although animals do not require light directly, they are part of a food chain that begins with those carbohydrates that are produced by plants.  With no light and with no new water bringing nutrients into the buoyancy tank, any tiny animals and plants in the plankton that might get inside the tank and plumbing should be unable to survive and thrive.  Although the patent does include a plankton filter, chlorine, copper sulfate, or some other toxic chemical should be added to any new ballast water.  One simple and environmentally friendly method of preventing organism infestations would be to simply place enough salt blocks inside the front and rear compartments so that the ballast water would remain sufficiently saturated with salt to kill any organisms that might get in. A detailed explanation is in the patent.

Gulf Stream Turbines operating in the Gulf Stream will be at depths where the current velocities will probably be between 4.5 and 6.5 mph.  Although the automatic version would offer no advantage over the other versions when operating in the Gulf Stream, it could be a good choice where current variations were great and the bottom conditions prohibited the use of bottom weights.  This would be where the current’s direction varied or where the ocean bottom contained wrecked ships, rocks, or coral formations that could foul or be damaged by the weights or the lines to the weights, or where the depths varied greatly over short distances.  This latter condition could describe where the Kuroshio passes over the Izu-Ogasaware Ridge. 

A Simpler Version Using Water Pressure to Control Depths

The automatic version just described contains one feature that can be used in a simpler version: the system for controlling the hydrofoils by measuring the water pressures and the rates that those pressures are changing.  Unlike the fully automatic system, this version would be unable to add or subtract ballast water, which would avoid any problems from infestations of marine organisms.  One of these versions could be similar to the automatic version, except for the compartmentalization of the buoyancy tank and the plumbing.  Like the fully automatic version, it could use a simple mercury switch to control pumps to move ballast water between the end compartments to keep the unit level. Except for a small watertight space to enclose the electrical control system, motors, and pumps, the compartmentalization of the buoyancy tanks could be similar to those for the non-automatic versions.  From its outward appearance, the machine could be indistinguishable from the fully automatic version.

Using Water Pressure to Control the Depth on Low-Hitch-Point Versions

            The pressure-reading system for the previously described versions can also be used for versions with low-hitch-points, however, for a slightly different purpose.  Because the low-hitch-point versions control depth by using leveraged drag forces to rotate the entire structure to balance their hydrofoils’ lifting forces to the changing downward vector forces, adding a pressure-controlled adjustable fin could cause problems if it were not done correctly.  The pressure-controlled movable fin should not be the major source of the structure’s lifting force.  This is because, when the hydrofoil is rotated to increase the lift, it would increase the rotation of the entire structure.  That, in turn, would further increase that fin’s angle of attack.  This would set up a perpetual up and down oscillation that would cause the fin’s controlling motor to continuously reverse.    


 

The electrical depth control system, however, should work on low-hitch-point versions if the powered hydrofoils were used primarily to change the angles of attack and lifting forces being produced by the much larger rear-mounted hydrofoils.  If the movable hydrofoils were small canards, as they rotated they also would cause the entire structure to rotate, which would further increase the fins’ angle of attack.  However, the rotation of the entire structure would also increase the angle of attack of much larger rear-mounted hydrofoils, which would increase their lifting force still more, which would stop the rotation.  The preceding drawings show a low-hitch point version that is equipped with small depth-controlling canards and constant-speed, variable-pitch rotors.   

Using Water Pressure to Adjust the Anchor Line’s Attachment Point

Another way that the depth control system can be used is to adjust the height of the anchor line’s hitch point. As the downward vector forces cause the unit to be too high or too low, the device could slowly move the anchor line’s attachment point up or down.  If low water pressure indicated that the machine was too high, the device would raise the hitch point, which would reduce the hydrofoils’ angle of attack and, consequently, their lift.  Conversely, if the machine were too low, it would lower the device to increase the hydrofoils’ angle of attack to increase their lift.  With the machine’s submerged center of gravity properly adjusted, the device would seek out that attachment point where the structure would remain at the desired depth with no further movements of the device being required.  This pressure-reading device could be valuable for adjusting the hitch point heights of the first machines to go into service.  If the device were not well designed, it could eventually become fouled due a buildup of encrusting bio-organisms.

 Using Water Pressure to Shift Center of Gravity to Control Depth

Though all of the previously described systems for controlling the operating depths can work, the best approach would be to combine the low-hitch-point system with a simplified version of the pressure-reading device.  In this case the pressure-reading device would be used to control pumps that would move the ballast water between the buoyancy tank’s front and rear compartments.  Pumping the water from the front to the rear would cause the structure’s rear end to drop lower.  This would increase the hydrofoils’ angle of attack, which would increase their lift.  Moving the water forward would obviously do the reverse. 

Because this application of the pressure-reading device would result in slow responses and because the structure’s vertical movements would not overshoot the desired depths, the switches 103 and 104 (see the previous schematic) that limit the rates of ascent and decent, can be eliminated.  When used in combination with the low-hitch-point system, this device would do a superb job of keeping long strings of many Gulf Stream Turbines operating at their preset depths.  Another advantage of this combined system is that it should also make it much easier to recover the individual machines for servicing or repair.  After a unit has been disconnected from the electricity collecting cables, shifting the ballast water to the rear compartment would increase the hydrodynamic lift to bring the still anchored structure to the surface.

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