GB2407438A

GB2407438A - A wave powered air assisted linear generator

Info

Publication number: GB2407438A
Application number: GB0320008A
Authority: GB
Inventors: Terence Halliwell
Original assignee: Individual
Current assignee: Individual
Priority date: 2003-04-29
Filing date: 2003-08-27
Publication date: 2005-04-27
Anticipated expiration: 2023-08-27
Also published as: GB0310481D0; GB2407438B; GB0320008D0

Abstract

A buoyancy powered linear generator comprises an inner vertical tube A which is fixed to the seabed while an outer tube C is attached to an annular float. Attached to this outer tube is an inner tube which moves within the fixed tube, while the outer tube moves within another fixed tube B. This arrangement of tubes thus comprises four linear generators. The whole structure is supported by a structure F which may be likened to an oil/gas platform. The inner fixed tube has a series of bearing rings fitted along its length. The float device is fitted with inclined paddle blades J which cause the sliding components to partially rotate as they move. up and down. Compressed air, from tanks located in the support structure, is used to maintain a critical air gap between the sliding components. Compressed air may also be used to help drive the generator. When sea conditions are calm, or in a lake, compressed air may provide the sole drive for the generator.

Description

1 2407438 Title SEAWAVE or WATER DRIVEN-AIR ASSISTED: HIGH POWERED: LINEAR

ELECTRICAL GENERATOR.

This Patent Application describes the design and construction of a Sea Wave driven/Water-driven/Air assisted Linear Generator capable of producing Megawatts of electrical power.

BACKGROUND

(1) Linear Electrical Machines, both Motors and Generators, are designed by 'rolling flat' the two principal components, (Magnets and Coils), of conventional Rotary Machines, (which are in the circular plane): and then sliding one set over the other in the form of'plates', or curving them around reciprocating concentric tubes. Since the relative velocities between the components, of any Linear Generator are very low compared with rotating machines, (probably less than I %), it is necessary that the swept area of the Magnetic Field is increased, in practice I believe, by as much as a thousandfold, (because of magnetic leakage and larger airgaps), to be able to generate the same levels of electrical power from similar Magnetic Field Densities. To obtain such factors in a practical Linear Generator of equivalent output as conventional rotary Alternators ( 10 Megawatts), requires therefore the construction of huge machines.

(2) Size however, has real advantages in terms of efficiency, from two standpoints.

Larger machines will gain from much higher Reynolds Numbers for the Hydraulic and Flotation Drives, and proportionally lower Magnetic losses for the generators themselves. Losses from friction will be increased only linearly by comparison.

(3) The design of Linear Motors is well established. In low- powered forms they are widely used as actuators in a host of applications, from computer ancillaries to large machinery and compressors. These motors are generally cylindrical in configuration, but flat ones are used for specific applications. High powered, 'flat', versions have been developed for MAGLEV systems, but these have not been successful as yet, largely because of magnetic leakage at the edges of the plates, and the use of very expensive Supermagnets and their support and cooling systems. These serious weaknesses, would also plague any large 'flat' Linear Generators designed to produce equivalent high power outputs, (Megawatts) (4) The maintenance of the critical air gap between the very large sliding plate components necessary to produce these levels of power, in a marine and hostile weather environment, renders such 'flat' configurations totally impractical, since Sea Waves are the most efficient means available for producing the huge linear forces necessary to drive such machines. Less powerful and more compact versions are conceivable, driven by Hydrofoil wings in fast flowing water, but their application is limited, since their performance would be less than that of a conventional water turbine.

(5) The detail design of large, seawave driven Linear Generators, is at the moment uncharted territory, in particular that of the crucial Flotation Device, and the means of sustaining the critically small airgap between the sliding components of the Generator which drives the machine. The proposals submitted in the following Patent Application are eminently feasible, and well within the reach of contemporary technology.

Furthermore it is the contention of this Application, that the only feasible configuration for such large machines, is the cylindrical or tubular format.

(6) In terms of specification, such a machine would need to produce upwards of 10 Megawatts of electrical power from a maximum movement of 60 feet, (the distance the 'Inner Sliding Tube', moves relative to the 'fixed tube'), operating at a minimum relative velocity of 1 Oft per second, and with magnetic flux densities of the same order as conventional rotary machines giving the same output. These tubes would be required to be up to 300 fit high and 30 fit in diameter, to give a sufficient area of Magnetic Field to generate the necessary Magnetic Drag, from these relatively low magnetic flux densities. The air-gap separating the sliding elements of such a Linear Generator, is a critical factor in the performance, and needs to be sustained (at a nominal 0.25 ins.), inspite of the very large surface areas, relative movements, and potential distortion of these huge components. This Patent Application proposes, that, by pressurising the device using high pressure compressed air, then this can be utilised, to maintain and support the air-gap, by using it as an air cushion, made more rigid by constantly circulating the compressed air through the air-gap; basic support and separation being given by a series of annullarly arranged ball bearings, located in the moving parts. This air system is used both to add buoyancy to the Flotation Device, by 'blowing out', the flooding water, and also to help drive the sliding components of the Machine, at the top and bottom of it's stroke. Indeed, in calm water conditions, such as a lake, it is possible to conceive a version of the Machine which is driven solely by these processes; this version is included in this Patent Application. This version being much less efficient than the Seawave driven version, because of it's consumption of compressed air.

(7) As a compromise to assembly and installation costs, sea location and depth; smaller, and even multiple versions could be built.

Significantly increasing magnetic flux densities, by the use of'supermagnetic' materials, would allow for smaller machines also, but at the price of increased weight, complexity, cost, and pro-rata increase, in magnetic losses. The performance of the simpler, larger machines, of course, could be greatly improved, by the use of these Hi- Tech magnetic materials and sophisticated coil design and orientation, attached to the working surfaces of the Generator tubes; but as always, complexity, leads to increased costs, for assembly and maintenance. In the hostile environment of an angry sea, simplicity is paramount.

(8) During the 'upward', rising stroke ofthe machine, the only limitation to the vertical force exerted by the seawave, is the displacement of the flotation device, plus any additional upward force, generated by the rising wave itself. It is a further proposal of this Patent Application, that the addition of a Skirt to the base of the Flotation Device, will trap a portion of the rising seawave, and so add significantly to this upward driving force. Additional upwards and downwards force is obtained, by introducing high pressure compressed air, alternately above, and below the ends of the sliding components. These apart, the maximum downward force available however, is confined to that of the total weight of the moving parts of the machine, plus any hydraulic forces generated by the receding seawave. For the machine to operate on the downward stroke, both these forces must be significantly greater than the sum of the Magnetic Drag, and the Frictional Drag, which opposes them in each direction of travel. Ideally, the total weight of the moving parts, ( the Sliding Tubes and the Flotation Device), should be kept as low as possible, by the use of lightweight materials, so that the maximum Magnetic Field Densities can be utilized, for a minimum volume of Flotation Device. To generate sufficient downward force therefore, means must be found to increase the weight of the Flotation Device towards the top of it's travel, and also to use another system of generating downwards force.

To achieve the former is by arranging to partially flood the Device, during the upward stroke. The latter is proposed in this Patent Application,- is by the use of air pressure, to assist in the driving up and down of the moving parts of the Linear Generator.

(9) In the Seawave driven version, to prevent 'stalling', and to maintain efficiency, by keeping as closely synchronized to the frequency of the seawave as possible, the upward and downward velocities of the Flotation Device of the Linear Generator, must closely approach those of the prevailing characteristics of the sea. This implies the necessity of a sensing device to measure these factors, and to automatically adjust, as necessary, a) the restraining magnetic force, and or b)the downward driving forces, acting on the Machine. The vertical acceleration of the sliding components, must be at least that of the rising and falling seawave, in order to keep pace with it, minimally estimated as ±O.Sg.,. This Patent Application, offers a simple solution, as follows.

( 10) To obtain the extra weight needed to accelerate the Machine in the downward stroke as the seawave recedes, the Flotation Device takes onboard seawater during the upward stroke. This partial flooding of the Device is achieved through the use of 'one- way', pressure sensitive valves, situated in the device itself. The 'inlet' valves to open during the 'upward' stroke, the 'outlet' valves to open during the 'downward' stroke, sufficiently to empty the Device, at the point of lowest travel. Indeed it is conceivable that these valves are operated by sea pressure alone. Any necessary reduction in the magnetic forces to achieve the required downwards acceleration, are of course made by reducing the magnetic fields of the Generator itself, but are undesirable since they will also significantly reduce the power generated, in the 'downward' stroke.

Restricting the upward and downward travel of the Flotation Device is necessary, but relatively easy to achieve, simply by the process of flooding the Device to give neutral buoyancy, near to the limits of travel, and or, by directing compressed air, above or below the ends of the sliding tubes and cylinder. Stopping the Device safely, is done by sinking it against a 'buffer-stop ring', attached to the top rim of the Lower Fixed Tube.

(l l)Since the technology and construction of similar structures approaching these dimensions, is already well established in off-shore OiUGas Platforms throughout the world, I propose that these could be the starting point for prototype machines. Indeed the use of existing rig components is very feasible, in the construction of the Support Decking and Tripod, subject to their ability to contend with the very large reciprocating forces involved, (upwards of several thousand tons weight).

Specimen Dimensions: Nominal Sea Depth-2()0ft.,.

The bottom surface area ofthe Flotation Device is 8455 sq.ft, or 1.22 x 10 to the power 6, square ins.,. Allowing compressed air at a mere 101bs. /sq.ins., to enter underneath the skirt, generates an up-thrust of 5435 tons. The total weight of the Machine ( that of Sliding Tubes plus the Flotation Device and including the weight of all the electro -magnetic components), should not much exceed 1000 tons, particularly if most of the Flotation Device is constructed of lightweight material.

A work rate of 10 Megawatts is achieved by moving an Equivalent Magnetic Force of 327 tons weight, 10 ft., in 1.0 second. This proposed Machine has a total magnetic field area of 6500 sq.ft., thus requiring an Equivalent Magnetic Field Strength of 113 Ibs.weight,per square foot, or 0.78 Ibs.weight, per square ins.,. To achieve 500 tons weight of Equivalent Magnetic Force, therefore requires Equivalent Magnetic Field Strength of 1.19 lbs.weight, per square ins.,. If the latter figure is worked to, the downward acceleration ofthe Machine, due to it's weight alone, is 0.5 g. This level of acceleration should be sufficient for the Flotation Device to remain in contact with the receding seawave, on the downward stroke, without recourse to additional weight through the taking on of water during the upward stroke. The use of High Tech., electro- magnetic systems, however, could generate Equivalent Magnetic Forces nearer to the total working weight of 1000 tons, from a Equivalent Magnetic Field Strength of 352 Ibs.weight, per square foot or 2.44 lbs.weight, per square ins.,. Such a machine would have the work rate of 31 Megawatts for a relative velocity of 10 ft.,per second, between the sliding and fixed tubes of the Machine. The preferred version of the Machine therefore, is that where the Equivalent Magnetic Force approaches that of the total working weight ofthe Machine. This version would need to take on 35,000 cubic feet of seawater, (weighing 1000 tons), to achieve 0.5g acceleration on the downward stroke. This is equivalent to 78% flooding of the semi-conical base of the Flotation Device.

The volume of the bottom semi-conical section of the Flotation Device is 44,856, cubic feet.

The volume of the Inner Sliding Cylinder is 212,000 cubic feet The volume ofthe Upper Chamber ofthe Flotation Device is 214,000 cubic feet The area ofthe top ofthe Inner Sliding Cylinder is 706 square feet, or 101,664 square ins., . Air pressure of 20 lbs., per square ins., acting on this area, gives a thrust of 908 tons. The area ofthe base ofthe Flotation Device is 8,461 square feet, or 1.22 million square ins. Air pressure of 20 Ibs., per square ins., acting on this area, gives a thrust of 10,893 tons.

ESSENTIAL TECHNICAL FEATURES

(a) To be of any practical value in terms of producing Megawatts of electrical power, and to avoid the above drawbacks, it is contended, by this Patent Application, that any such Sea Wave driven Linear Generators must therefore be of cylindrical form, and very large- in the order of 300ft. long and 30ft.diameter to be able to produce a minimum of 10 Megawatts from a relative velocity of 10 fit per second, and a maximum movement of 60 ft.

(b) It is proposed in this Patent Application. that the optimum design for a Seawave.or Water Driven, Air Assisted Linear Generator is that consisting of an Inner Sliding Cylinder, an Outer Sliding Tube, an Inner Fixed Tube, (which is mounted vertically and attached to the seabed, or lake bed at it's base!. an Upper Fixed Tube, which supports the top of the Machine and which is itself attached to the Support Decking, which is mounted on Tripod legs, fixed to the seabed at their base. The bottom of the Device, has the required additional support in the form of Lower Fixed Tube, which is attached to the Seabed. and in which the base of the Outer Sliding Tube moves up and down. It is envisaged that the two Fixed Tubes take the principal vertical loading of the Machine. The Tripod and Support Deck take the form of those in a conventional Oil/Gas Platform.

Both the Inner Sliding Cylinder and the Outer Sliding Tube are connected together near the top and are both driven by the Flotation Device which is attached to the outside surface of the Outer Sliding Tube. At it's base this Tube reciprocates inside the Lower Fixed Tube. This format actually comprises four linear generators in one, as follows: 1!The outer surface ofthe Inner Sliding Cylinder against the inner surface ofthe Inner Fixed Tube.

2!The inner surface of the Outer Sliding Tube against the outer surface of the Inner Fixed Tube.

3!The top section of the outer surface of the Outer Sliding Tube against the inner surface of the Upper Fixed Tube.

4!The bottom section of the outer surface of the Outer Sliding Tube against the inner surface of the Lower Fixed Tube.

The moving parts of the Machine run on ball bearings, arranged in a series of annular rings, along the length of the sliding components, and the entire machine is pressurized by high pressure compressed air. The very large compressed air storage tanks necessary, are located. in the whole of the Inner Sliding Cylinder.

(high pressure). and in the Upper Chamber ofthe Flotation Device. (lower pressure for the seawave driven version only!. and in remote (lower pressure! tanks. located in the Tripod Legs. This compressed air is vital in maintaining the critical air-gap. between the sliding components. but is also necessary to help seal the machine from water ingress and to 'blow- out' the water. as required from the Lower Chamber of the Flotation Device. and from under the Skirt. of the Flotation Device. Additional upwards force is generated by feeding compressed air under the skirt of the Flotation Device. when operating in calm conditions. Some additional upwards force is also generated. at the bottom of the Machines downward stroke.

by admitting compressed air under the bottom of the Inner Sliding Cylinder before it progresses through the main air-gaps into the bottom of the Lower Fixed Tube.

and then into the 'lower pressure' system. Air is also utilised. inside the sealed top of the Upper Fixed Tube. (designated as the Top Chambers in a similar manner this time by downwards passage through the main airgaps. This along with the partial flooding of the Device to help drive down the Machine against the Magnetic Drag so helping to maintain this during the downward stroke. thus making the Machine more efficient. By simply arranging a pressure difference between the compressed air tanks. the Inner Sliding Cylinder. being the 'high pressure" the Upper Chamber of the Flotation Device and those in the Tripod Legs the 'low pressure'! the compressed air can be made to constantly circulate through the compressors mounted on the Support Decking since this continuous movement of air through the 'air-gaps' of the Machine gives a more effective and rigid air cushion. In addition. to help prevent 'jamming: ofthe sliding components. by imparting a twisting motion to them as they reciprocate. and also to extract more energy. from the seawave. as it passes. the vertical sides of the Flotation Device is equipped with tilted Inclined paddle blades. which are arranged circumferentially.

1 Inner Sliding Cylinder/Outer Sliding Tube.

This consists of a sealed cylinder, 300ft long x 30ft diameter, which also acts as a high pressure compressed air tank, and slides completely inside the Inner Fixed Tube. The outer surface of this cylinder has inlaid magnets and coils, to comprise half of a linear generator. The top of this cylinder is extended, and the sides 'belled outwards', where it is joined to the inner surface of the Outer Sliding Tube. Above this point the Inner Sliding Cylinder, and the Outer Sliding Tube, become one, and this now combined and extended Cylinder, is sealed at the top. High pressure compressed air is fed into the cap, through flexible hoses, directly from the compressors, located on the Support Decking,- air being then allowed, into air- gap, from valves, situated, both in the top, and in the base of this Cylinder. By the simple means of opening and closing these valves alternately, the bottom valve to open when the Cylinder is at the bottom of it's stroke, and the top valve when the Cylinder is at the top of it's stroke, compressed air is fed either above or below the ends of the Cylinder, to add to either upward or downward forces acting upon it.

[ he alternate, and continuous upward and downward movement of compressed air, through the air-gaps, increases their stiffness, and resistance to the distortion of the moving tubular components of the Machine. Additionally, a set of valves located just above the level where the Inner Sliding Cylinder and the Outer Sliding Tube are joined, and arranged peripherally, in the wall of the Outer Sliding Tube, directs a portion of the high pressure compressed air via the air-gap of the Upper Fixed Tube, during the upward stroke, only.

2 Inner Fixed Tube This tube is attached to the seabed, or lake bed, at it's base, and it's inner surface contains inlaid magnets and coils, to comprise the other half of the above linear generator. This inner surface also carries the Inner Cylinder support ball bearings which are arranged in the form of annular rings at intervals along it's length. The outer surface of this Inner Fixed Tube, replicates the inner surface, by again housing inlaid magnets and coils, and a further set of ball bearings, to support the Outer Sliding Tube. Separate ball bearings are necessary, because both the Outer Sliding Tube and Inner Sliding Cylinder are joined, and travel in the same direction. In the base of this Tube, are a series of peripheral valves, which allow compressed air to return, via external pipes, into the 'lower pressure', air circuit of the Machine, (located in the Tripod Legs),., These valves are closed during the upward stroke, and are open during the downward stroke 3! Outer Sliding Tube/Inner Sliding Cylinder.

This tube is attached to and is driven by the Flotation Device, fixed to it's outer surface. This Tube, blends into, and is attached to the top of the 'belled out', section of the Inner Sliding Cylinder, in such a way, that when the Inner Cylinder is at the bottom of it's stroke, this junction just clears the top of the Inner Fixed Tube. A series of one way 'flap', valves, which only permit the downward movement of air through them, are located in the area just below this junction, in the wall of the Outer Sliding Tube, which allows compressed air, downwards through the main air-gaps. Above this junction in the wall of the Inner Sliding Cylinder, are small valves which allow the controlled leakage of high pressure air, into the Top Chamber, through the air-gap, in the Upper Fixed Tube. The position of the Flotation Device, with respect to the Outer Sliding Tube, is dependent on the nominal water depth, where the Machine is installed.

The top portion of the outer surface of the Outer Sliding Tube, ( that section which enters the bottom of the Outer Fixed Tube), has magnets and coils inlaid into it, to form part of the third Linear Generator, but this section of the outer surface must be smooth to allow the peripheral air/water seals located in the bottom rim of the inner surface of the Upper Fixed Tube, to operate. The bottom portion of the outer surface of the Outer Sliding Tube, is similarly equipped, since it moves inside the Lower Fixed Tube, to form part of the fourth Linear Generator, and has a smooth section of lower outer surface, in contact with the peripheral air/water seals located in the upper rim of the inner surface of the Lower Fixed Tube. Additionally, air which has passed downwards, through the air-gaps, then exits through the outlet valves, (when the Machine is at the bottom of it's stroke), located in the top of the Lower Fixed Tube, via the air -gap of this fourth Linear Generator. Just above the level of the top of the Lower Fixed Tube, when the Outer Sliding Tube is at it's lowest point, there are valves located in the wall ofthe Outer Sliding Tube, which permit the leaking off of compressed air via external pipes into the Upper and or Lower Chambers of the Flotation Device, from the main air-gaps, and are used during the starting of the Machine to fill the Flotation Device with compressed air, and to maintain the requisite pressure during the operation of the Machine.

4! The Upper Fixed Tube This shorter tube, ( 1 50ft., long), is fixed at the base of it's outer surface, to the Support Decking, and extends above it sufficiently to allow maximum travel of the Sliding Tubes up into it, and below it to sufficiently to overlap the protruding upper end of the Inner Fixed Tube. The inner surface of the Outer Fixed Tube, has inlaid magnets and coils throughout, thus forming the remaining part of the third Linear Generator. By sealing this tube at the top, (thus making the Top Chamber); high pressure compressed air, from the top of the combined Inner Sliding Cylinder/Inner Sliding Tube, pressurises the third Linear Generator air-gap, then passes downwards via the 'flap valve', in the wall of the Outer Sliding Tube, down through the main air-gaps of the Machine, and into the 'lower pressure', side through the valves in the bottom of the Inner Fixed Tube, and the Outer Sliding Tube. This high pressure air, from the highest point of movement, contributes, together with the partial flooding of the Flotation Device, to drive down the Sliding Tubes against the Magnetic Resistance of the Linear Generators.

Additionally small valves, located in the walls of the Inner Sliding Cylinder, above the joint with the Outer Sliding Tube, when opened, (only in the upward stroke), allow some of the high pressure compressed air into the air-gap of the Upper Fixed Tube, which then returns into the lower pressure side of the air compressors, positioned on the Support Decking, via the valves positioned in the top of the Upper Fixed Tube.

5! The Flotation Device, is in the form of a sealed and hollow elongated doughnut', 100 fit diameter, and 40ft high, in the case ofthe Seawave driven version, only. The Lake Located version, is 10ft. high The base is an inverted hollow semi-cone, 15 ft., high, which also acts as the base of the Lower Chamber and is suitably reinforced, and of annular corrugated form sufficient to support the weight of flooding water above it. The Flotation Device therefore has two chambers, in the Seawave driven version, but only one in the Lake Located version. The Lower Chamber is 25 fit high at the base, ( including the height of the inverted semi-cone base of 15 ft.), the height of the Upper Chamber is 30 ft., above this. A Skirt 15 ft., long extends downwards, from the lower cylindrical rim of the 'doughnut', the purpose of which is both to trap the rising seawave, and also the compressed air fed under it, from the Chamber of the Flotation Device through external pipes,- to assist in the lifting of this Device. The Lower Chamber has a series of water inlet/outlet valves, arranged peripherally, around the top of the semi- conical surface, underneath the top of the Skirt, which open to flood, and empty this Chamber. The bottom of the semi-conical section, also has large triangular 'Flap' water valves, which permit rapid flooding, but slower emptying, at the bottom, and top, respectively of the stroke of the Machine. Inside the top of the Skirt, are air valves which open to allow either trapped air, back into the Upper Chamber during the flooding process, or compressed air, from the Upper Chamber, in the opposite direction through external pipes. Separate air valves connect the Upper and Lower Chambers, in the Seawave driven version, which permit the 'blowing', of water from the Lower Chamber, when required. In the Lake Located version, there is no Upper Chamber. In the Seawave driven version only, the Upper Chamber comprises a second compressed air tank, containing air at a lower pressure than that in the Inner Sliding Cylinder/Tube, and is connected to the air system of the Sliding Tubes, by external pipes, which run from this Chamber, directly into the 'lower pressure', tanks located inside the Tripod Legs in such a way as to provide the circulating air through the entire Machine so ensuring the support and maintenance of the critical air-gap. Allowing the trapped air to escape through valves located in the top of the Skirt back into the Upper Chamber causes it to flood. The rate of flooding can also be controlled by these valves.

Additionally, a series of Inclined paddle blades are arranged around the outside surface of the Device, in both versions to impart a twisting motion to the Sliding Tubes as water passes over them, during both the upward and downward strokes.

The inner surface of the 'doughnut', is attached to the outer surface of the Outer Sliding Tube, at the required height. In it's equilibrium position, with all the magnetic fields activated, the base of the Device, should just be resting on the surface ofthe sea, at it's nominal level.

6) The Lower Fixed Tube. This Tube is attached at it's base to the seabed/lakebed. The inner surface, has inlaid magnets and coils comprising half of the fourth Linear Generator, also the support ball bearings, arranged in a series of rings along it's length. The very top ofthis Tube has the peripheral 'air/water seal' over which the outer surface of the Outer Sliding Tube, runs. Valves are also located in the top of this Tube, which allow the passage of compressed air back into the 'lower pressure ' system, after having passed down through the main air- gaps, and also the air-gap between the inner surface of this Tube and the outer surface of the Outer Sliding Tube. The Buffer Stop Ring is located in the bottom of the gap between the Inner and Lower Fixed Tubes. The length of the Lower Fixed Tube, is determined by water depth, and maximum vertical travel ofthe Machine, which in this example, gives a Tube length of under 1 00ft., (for a nominal water depth of 200ft., and maximum travel of 60ft. ,).

7! The Support Decking and Tripod Legs. The Support Decking is mounted on a tripod of legs which are anchored to the seabed at the bottom. These anchorage's need to be sufficiently robust, to resist the very large reciprocating forces, implicit in the operation of the Machine. Tripod Legs, would also contain the main (lower pressure), air tanks, which are fed by external tubes, from the base of the Inner Fixed Tube, along the sea or lake bed, also Tom the top of the Upper Fixed Tube, and the chamber(s), of the Flotation Device, into the lower pressure side of the air compressors. This tripod arrangement is entirely similar to a conventional oil or gas platform, indeed such a construction could be directly used, provide that it has the capability of withstanding a reciprocating vertical force of several thousand tons weight. The Upper Fixed Tube and bearings are attached to this deck, and giw the necessary support to the top of the entire Machine. The necessary instrumentation, controls, telemetry, and high output air compressors, and support machinery, would be located on this deck, also.

Method of Operation The Machine is designed in two versions so as to operate in two differing types of conditions: 1) Flat Calm,- up to 15 ftswell, i.e.,( wave height peak to trough of 15 ft.), as in the Lake Located version.

2) Wave height from l 0 to deft., as in the Seawave driven version.

Lake Located Version.

For condition 1), above, this version of the Machine, has a different Flotation Device, comprising the Lower Chamber only. The Machine starts in it's sunken state, with the Chamber of the Flotation Device, partially flooded, and the volume under the Skirt, totally filled, at which point the bottom of the Outer Sliding Tube rests against the ' Buffer-Stop', at the base of the gap between Lower and Inner Fixed Tubes. High pressure compressed air is then blown into the Chamber of the Flotation Device, via the air-gaps, by simply opening the bottom 'high pressure valve' of the Inner Sliding Cylinder/Tube, and so under the top of the Skirt to expel the sea water inside them, causing the Flotation Device to accelerate upwards, assisted by the action of high pressure air on the base of the Inner Sliding Cylinder.

The Flotation Device continues to rise, until the degree of flooding of the Chamber, (achieved by the opening of the water inlet valves in the base of the Flotation Device as it rises), and changes in air pressure inside the Machine stops it. Continued flooding, of the Chamber, at the top of it's stroke, allied to the leaking off of the low pressure compressed air from under the Skirt, back into the low pressure air tank' causes the sliding components', to sink, aided by the high pressure air, admitted into the system, from the top valve of the Inner Sliding Cylinder/Tube, to the point where the bottom of the Outer Sliding Tube rests again on the Buffer- Stop Ring. The whole cycle is then repeated.

Seawave Driven Version.

For condition 2) above: Again the Machine is started from it's sunken position, with the Lower Chamber of the Flotation Device, flooded, and the bottom of the Outer Sliding Tube, resting on the Buffer-Stop Ring. The seawater is then expelled from the Lower Chamber using the high pressure compressed air from the bottom valve of the Inner Sliding Cylinder/Tube, which passes through the air-gaps, into the Top Chamber and then via the opening outlet valves of that Chamber into the lower pressure air tank which is the Upper Chamber of the Flotation Device. The Device will rise, with increasing buoyancy, and will stop, ( due to the Magnetic Resistance of the Linear Motors), during the period of the receding seawave, then to be driven upwards, by buoyancy, and the force of that portion of the rising seawave trapped under the Skirt of the Flotation Device, by the following rising wave. When caught by this rising wave the Flotation Device moves upwards, taking in seawater, into it's Lower Chamber, as it does so. When the seawave begins to recede, the partially Hooded Device descends with the wave, into the trough; assisted by increasing air pressure in the Top Chamber, due to the opening of the top valve, in the Sliding Cylinder/Tube. This high pressure air, passes down the air-gaps, and is directed back into the Upper Chamber of the Flotation Device, through the outlet valve In the central wall of the Sliding Cylinder /Tube, and or back into the 'lower pressure' system, via the ar-gap of the Lower Fixed Tube. During the latter stage of this descent, the contents of the Lower Chamber of the Flotation Device drain away, through the outlet valves, In the base of the Chamber. Ideally this Lower Chamber should be totally empty at the end of the downward stroke.

Reference to the attached drawings, will indicate the construction of the Device: and illustrate the operation of the Compressed Air System.

Referring to the drawings. The Device comprises the following principal components, see: Schematic Arrangement of components (Fipure 1 of 2, Pace 12),and: Arrangement of Compressed Air System (Figure 2 of 2.

Pane 13) Items Comorisinu Schematic Arrannement of Components Finure 1/2 Pane 12 The Inner Fixed Tube (A!* This is attached to the seabed at the base, and the top of this tube protrudes into the base of the Outer Fixed Tube. The entire inner and outer surfaces of this Fixed Tube has Coils and Magnets embedded into them, to form part of the first and second Linear Electrical Generators. Two sets of support ball bearings, are also inlaid into both the inner and outer surfaces of this Tube, arranged in a series of rings, at regular intervals along it's length. Valves in the bottom of this Tube, which open only during the downward stroke of the Machine, allow compressed air to return to the 'lower pressure', system.

The Lower Fixed Tube (B). This is also attached to the seabed at it's base, but is shorter than the Inner Fixed Tube. This tube has support ball bearings, arranged in a series of rings along it's length, which are in contact with the lower portion of the Outer Sliding Tube. The entire inner surface of this Tube has inlaid magnets and coils to form half of the fourth Linear Generator. It also houses a peripheral air/water seal inside the top rim, and has valves to permit compressed air to re- enter the 'lower- pressure', air system, from the air-gaps.

The Inner Sliding Cylinder/Outer Sliding Tube. Initially as the Inner Sliding Cylinder, this component runs inside the Fixed I ube on the large ball bearings on the inner surface of the Inner Fixed Tube, and is attached to, and becomes one with the Outer Sliding Tube by 'belling out' at it's top. Coils and Magnets are attached to or embedded, in the outer surface of the Inner Sliding Cylinder, to form part of the first Linear Electrical Generator, along it's total length. This composite Cylinder is sealed at both ends so acting as the 'high pressure' compressed air storage tank. It is fed by hoses into the top directly from compressors located on the Support Decking, and has outlet valves in it's base and top, to control the flow of high pressure compressed air into the airgaps. By opening these valves alternately, (the top valve at the top of the stroke, and the bottom valve at the bottom of the stroke), this allows high pressure air to assist in moving the sliding components of the Linear Generator. Additionally, there are a further two sets of valves located in this component. The first set comprises one way 'flap valves', which only allow the downward passage of compressed air through the air-gaps on the downward stroke. These valves are located at or below the junction of the Inner Sliding Cylinder and the Outer Sliding Tube, in the wall of this Tube. This compressed air then piped from the outlet valves situated towards the base of the Outer Sliding Tube, into the Lower and Upper Chamber of the Flotation Device and then under the Skirt. The second set are positioned in the wall of the Inner Sliding Cylinder, just above the joint, and permit the leakage of higher pressure' air, directly into the air-gap in the Upper Fixed Tube, during the upward stroke of the Machine.

The Flotation Device (D). in the form of a hollow, elongated cylindrical 'doughnut'. It comprises two compartments, in the Seawave driven version, but only one compartment, ( the Lower one), in the Lake Located version. The Upper compartment or Chamber acts as the 'low pressure' compressed air storage tank.

The Lower Chamber, is alternately flooded and emptied, to provide extra weight for the downward stroke, or just buoyancy for the upward stroke, depending on the operating conditions. The base of the Lower Chamber is in the form of an inverted semi-cone, and is reinforced to carry the weight of flooding water above it. The use of a corrugated surface, in the form of concentric rings, serves to significantly increase it's area, and add to it's strength. A Skirt extends downwards from the lower periphery of the 'doughnut', to trap compressed air released under it from the Lower Chamber, and also to capture part of the rising seawave, depending on the operating conditions. The Flotation Device, is attached to the outside surface of the Outer Sliding Tube, at the appropriate height, depending on the operating conditions and dimensions of the Machine. Inclined paddle blades, are fixed to the outer vertical surfaces of the Flotation Device., to make this and the composite Outer Sliding Tube/Inner Sliding Cylinder, twist, as the Device is driven upwards and downwards.

Large triangular shaped valves are set into the apex of the semi-conical base; they permit water to flow, out of the Flotation Device from the start of the downward stroke, to empty it, and in, at the start of the upward stroke to flood it.

The one-way, 'inlet valves', are positioned under the skirt, in the top ofthe semi- conical surface. Compressed air is piped externally, through the appropriate valves, in the wall of the bottom section of the Outer Sliding Tube, into the Upper Chamber, and from the top inside of the Skirt into the Upper Chamber.

The Upper Fixed Tube (E!. is fixed at it's bottom outer rim, to the Support Deck. The top of the Inner Fixed Tube, and the composite Inner Sliding Cylinder/ Outer Sliding Tube, protrudes up into it The inner surface of this Upper Fixed Tube, has support ball bearings, and magnets and coils embedded into it, for it's entire length, and forms with the top section of the Outer Sliding Tube, a third Linear Generator. The bottom inner rim of this Tube, has a peripheral, oiVwater seal which runs along the outside surface of the Outer Sliding Tube. The top of this tube also houses valves, which permit the return of compressed air back into the 'lower pressure', tanks in the Tripod Legs.

The Support Deck and Tripod (F!. The Support Deck is attached to the top of the Tripod Legs, which are themselves fixed to the seabed at the bottom. This arrangement can be considered to be a duplication of a normal oiVgas platform.

The Support Deck houses the compressors, controls, telemetry, and support systems of the Machine. The Tripod Legs contain further low pressure air tanks.

The Skirt. (G!. Extends downwards from the rim of the Flotation Device. They are designed to trap the rising seawave, and also that compressed air used to any required buoyancy under the Skirt in order to drive the Flotation Device upwards.

The Rim Air/Water Seals (H). These are attached to the rims of the exposed ends of the Upper and Lower Fixed Tubes, and operate against the outer surface of the Outer Sliding Tube.

The Inclined Paddles (J). These are arranged around the vertical surface of the Flotation Device, so as to impart a 'twisting motion', to the sliding components of the Machine, as water passes by them, both to aid their movement and help prevent 'jamming'. Is

Nomenclature for Arrangement of Compressed Air System: Fiqure2/2 Pane 13 Lower Pressure Lines _________, ' ' ' ' Higher Pressure Lines O Compressors C1 Lower Pressure Valves Higher Pressure Valves O Air/Water Seals [= Inner Fixed Tube Lower Fixed Tube 3 Inner Sliding Cvlinder/Outer Sliding Tube Flotation Device 0= Upper Fixed Tube Tripod and Support Decking Skirt of Flotation Device Inclined Paddles It

Claims

CLAIMS A High Output, Seawave, or Water Driven,-Air Assisted Linear Generator, (capable of producing upwards of 10 Megawatts of electrical power), from a relative velocity of l Oft per second, with a maximum movement of 60ft, in the form of two concentric vertical tubes, 300 fit longx30ft diameter: one fixed to the seabed, or lake bed at it's base, the other sliding over it, connected at the top to a further sealed cylinder, which itself slides inside the fixed tube. The top portion of the composite, Outer Sliding Tube/Inner Sliding sealed cylinder, reciprocate inside another Upper fixed tube, which is mounted on a support decking, fixed onto a tripod, the feet of which are anchored to the seabed, just as in a conventional Oil/Gas platform. The Machine is additionally supported at it's base, by a Lower Fixed Tube attached at the bottom to the seabed, into which the base of the Outer Sliding Tube reciprocates. This arrangement thus comprises four. linear generators.

1) The Critical Air-gap between the sliding surfaces ofthe Linear Generators, is supported and maintained, not only by a series of ball bearings arranged in a series of rings between the sliding surfaces, but more importantly by pressurizing the entire Machine, with compressed air. By maintaining a constant pressure difference, between the air tanks, through the external compressors; compressed air, is continuously flowing through the critical air-gaps between the sliding components, and it is this movement which adds stiffness to the air cushion.

Compressed air is also used to drive the machine, both directly, by acting on the top and bottom surfaces of the sliding Inner components, and by blowing out the water, flooding the Lower Chamber ofthe Flotation Device, and it's skirt.

2) The Inner Sliding Cylinder, is attached by 'belling out', the top onto the inner surface of the Outer Sliding Tube. This Cylinder comprises the 'higher pressure', air tank.

3) The Inner Fixed Tube, is attached to the seabed at the base and has large (1.0ft diameter), ball bearings, arranged in a series of rings fitted all along it's length of both the inner and outer surface. which themselves run along the inner surface of the Inner Sliding Tube, in order to maintain the Critical Air Gap, (maximum of 0.25 ins), between the sliding components two Linear Generator, composed of, this surface, the inner surface of the Outer Sliding Tube, and the outer surface of the Inner Sliding Cylinder. Air is returned to the lower pressure system, through valves, which open during the downward stroke.

4) The Outer Slide Tube, has a peripheral air/water seal at the bottom of it's inside surface, which rubs along the outer surface of the Fixed Tube. The inside surface of this Tube, comprises half of a Linear Generator.

5) The Flotation Device, is in the form of an elongated cylindrical 'doughnut', 40ft in height, in the Seawave driven version and 150 in the Lake Located version. The Device is 1 00ft in diameter, sealed at the top, and is connected to the outer surface of the Outer Sliding Tube. A 'Rim Skirt', projects downwards, as an extension of the sides of the 'doughnut', to trap a portion of the rising seawave, or compressed air vented from the Lower Chamber. The base of this device, is a hollow inverted semi-cone, 15 fit high, which houses the 'one-way' valves. The Inlet Valves, are situated under the 'Rim Skirt', where it meets the base ofthe 'doughnut', in the region of highest seawater pressure, and allow partial flooding of the Device during the upward stroke. The Valves, which allow the rapid flooding, and slower emptying of the semi-conical base, are situated in the apex of this semi-conical section. The Upper Chamber ofthis Device constitutes a 'lower pressure', compressed air tank, in the Seawave Driven version, only, since this Chamber is not included in the Lake Located version. The outer cylindrical surface of the Device has inclined paddle blades mounted on it so that the sliding components of the Machine partially rotate as they move up and down.

6) The Upper Fixed Tube. is mounted at the lower end onto the Support Decking, and the inner surface at the bottom carries a peripheral air/water seal, which is in contact with the top outer surface of the Outer Sliding Tube The Upper Fixed Tube also has ball bearings arranged in a series of rings on the inside surface, to support the top of the Outer Sliding Tube, which moves inside it. The space in the top of this Tube, above the cap of the Outer Sliding Tube/Inner Sliding Cylinder, called the Top Chamber, when pressurised with high pressure compressed air from the Inner Sliding Cylinder, assists in driving the Outer Sliding Tube downwards at the top of the Machine's stroke. Valves in the roof of this Top Chamber, allow the lower pressure air' back into the lower pressure storage tanks located in the Tripod Legs, via the Support Deck.

7! Support Decking and Tripod, is similar in arrangement to a conventional Oil/Gas platform with the bottom of the Tripod Legs attached to the seabed. The Tripod Legs also house 'lower pressure', compressed air tanks, fed from the valves located in the bottom of the Inner Fixed Cylinder, and in the walls at the top of both the Upper Fixed Tube and the Lower Fixed Tube.

To enable the Machine to operate in calm conditions, even if located in a lake; compressed air is used to 'blow out', water from the Flotation Device to give enough buoyancy to drive the Flotation Device and the attached Inner Sliding Tube upwards, aided by high pressure compressed air, which is fed under the end of the Inner Sliding Cylinder. As the sliding tubes move upwards, the Flotation Device takes in water, sufficient, that the upward motion is stopped, and the sliding components are driven down again by the combination of the weight of this water, and the high pressure compressed air admitted into the Top Chamber, above the top end of the Inner Sliding Tube. At the bottom of the downward stroke water is expelled from the Flotation Device, by compressed air, admitted from the air-gaps, through the valves in the wall of the Outer Sliding Tube.