Dam-Atoll Patent

Text Of Dam-Atoll Patent (4,152,895)

Note: The United States Patent (4,152,895) has passed into the public domain, and is no longer the intellectual property of its former assignee, a certain aircraft company.


References Cited

1,751,667 3/1930 Taylor........................... 60/398
3,912,938 10/1975 Filipenco........................ 290/42 X
3,928,771 12/1975 Straumsnes....................... 290/43
4,025,220 5/1977 Thompson......................... 415/7

Primary Examiner—Allen M. Ostrager
Attorney, Agent, or Firm—Ralph M. Flygare



Apparatus for converting ocean surface wave energy into useful rotational kinetic energy. A refractive horn and ramp provides reflectionless impedance transformation of ocean surface wave energy at the input to the system. Wave energy, in the form of breakers, which are massive pulses of essentially pure kinetic energy, from the output of the horn/ramp are then smoothed and transformed directly to mechanical rotation. Smoothing is accomplished by the inertial properties of a "liquid flywheel". The rotational kinetic energy may be extracted by means of a turbine to provide useful work. Discharged water is returned to the ambient ocean througoh a low terminal velocity diffuser. The entire structure may be located offshore and the discharged fluids may be used for auxiliary purposes.


Heretofore, many techniques have been used in attempts to convert ocean waves to useful applications. Many of these attempts have been directed to the use of the energy of tidal oscillations induced by the motions of the moon and sun. Other schemes have been directed to harnessing wind-generated surface waves and currents, since these comprise most of the total energy budget of the ocean.

Typical examples of such schemes are those disclosed in the following patents:

Patents directed to schemes for extracting tidal energy include:

Other wave motor devices are disclosed in:

None of the foregoing devices have met with significant commercial success. All such devices known to the applicant fail in one or more important respects to meet all of the requirements that are desirable for an ocean wave harnessing system. Probably the single greatest deterrent to the commercial acceptance of prior systems has been their marginal efficiency and their undue complexity which seriously degrades their reliability in the hostile environment of the ocean.


In view of the serious need to develop new energy sources in the face of depleting resources of fossil fuels, advancements in the state-of-the-art over the above described devices are required.


The overall objective of the p resent invention is to provide a highly practical means for the conversion of wind-induced surface ocean waves into useful power. The basic steps accomplished by the present invention in the desired conversion comprise, (1) concentrating the surface waves without significant reflection, (2) conversion of the potential energy component to essentially pure kinetic energy pulses, (3) smoothing of the kinetic energy pulses, (4) conversion of the smoothed kinetic energy to rotary shaft power, and (5) dispersal of the system effluent.


The novel structure, of the embodiment of the invention preferred for the open sea, utilizes Fermat's principal for concentrating randomly directed wave energy of variable period into pure kinetic energy which may then be applied directly to a turbine rotor.


Available power input of a typical or average ocean swell for a crest one meter above sea level having a ten second period is 40 kilowatts per meter of shoreline. A wave-concentrating element of the apparatus functions as the analog of an acoustical horn to concentrate the surface waves and cause them to crest and break. This device relies upon refraction phenomena and is capable of essentially capturing all incident wave energy over a broad range of wave periods regardless of the direction of approach. Waves propagated in the open ocean comprise energy which is approximately half potential and half kinetic. The geometry of the wave concentrator causes the wave to break and thereby be transformed into nearly horizontal, pure, kinetic energy, which is then directed radially inward towards a central inlet hub of the apparatus. Inlet guide vanes direct this rush of water tangentially into a central downward passage where it swirls in a vortex. The swirling water vortex functions as a liquid flywheel, the inertial properties of which smooths the pulsating energy, permitting the water to uniformly enter a turbine rotor where continuous rotating shaft power is generated.


After leaving the turbine rotor, the water effluent, still possessing some residual swirl, is discharged through a stationary diffuser into the surrounding ocean. In the diffuser the residual swirl serves to reduce the back pressure at the turbine rotor. The turbine rotor shaft may be used to drive an electrical generator or other utilization device. In a first embodiment, the entire assembly may be constructed to float and be tethered to an offshore mooring. Second and third embodiments comprising near-shore-based structures are also described.


After leaving the turbine rotor, the water effluent, still possessing some residual swirl, is discharged through a stationary diffuser into the surrounding ocean. In the diffuser the residual swirl serves to reduce the back pressure at the turbine rotor. The turbine rotor shaft may be used to drive an electrical generator or other utilization device. In a first embodiment, the entire assembly may be constructed to float and be tethered to an offshore mooring. Second and third embodiments comprising near-shore-based structures are also described.


In a typical construction, a device 78 meters in diameter will produce one megawatt of shaft power, rated with waves of one meter half-amplitude and having a period of seven seconds.


It is, therefore, an object of the invention to provide a novel and improved energy conversion system for receiving periodic surface wave energy and generating continuous useful kineetic energy as its output.


Another object of the invention is to provide novel and improved apparatus for the harnessing of ocean surface wave energy.


Still another object of the invention is to provide novel and improved apparatus for capturing and concentrating periodic surface wave energy which is partly potential and partly kinetic and converting it to essentailly all-kinetic energy.


Yet another object of the invention is to provide novel and improved means for smoothing pulses of kinetic energy so as to provide continuously-available kinetic energy, by means of the inertial properties of a liquid vortex.


A general object of the invention is to provide a wave motor system which is simpler in structure, more reliable in operation, and substantially more efficient than those heretofore known in the art.


The invention resides partly in the physical and mechanical structures embodied in the refractor/concentrator, pulse smoother, and rotating member and discharge/diffuser components of the system as herein specifically illustrated, but also embraces the concept of the system itself, considered as an integrated whole, and independently of the structural details of its several parts.


Since certain changes may be made in the energy conversion processes and the detailed constructional features of the system components without departing form the scope of the invention herein involved, it is intended that all matter contained in the descriptions of the preferred embodiments which follow or as shown in the accompanying drawings shall be considered as illustrative and not in a limiting sense.


FIG. 1 is a somewhat diagramatic cross-section of a floating wave powered motor constructed in accordance with a first embodiment of the invention.


FIG. 2 is a chart displaying ray paths and wave fronts impinging upon an atoll, which chart is useful in the exposition of the invention.


FIG. 3 is a plan view of symmetrical inlet guid vanes taken along line 3—3 of FIG 1.


FIG. 4 is a plan view of individually shaped inlet guide vanes taken along line 3—3 of FIG 1.


FIG. 5 is a chart which illustrates a typical power spectrum of ocean waves, and swell.


FIG. 6 is a perspective view of the invention installed in its operating environment.


FIG. 7 is a diagramatic plan view of the wave-concentrator horn portion of a second embodiment of the invention showing the concentration of the ocean surface waves and their transformation to breakers.


FIG. 8 is a diagramatic elevation view of the apparatus of FIG. 7.


FIG. 9 is a diagramatic top plan view of the second embodiment of the invention showing a horn and ramp connected tangentially to a basin which contains the liquid flywheel.


FIG. 10 is a diagramatic elevation cross-section view of the apparatus of FIG. 9 taken along line 10—10 of FIG. 9.


FIG. 11 is a diagramatic cross-section view in elevation illustrating a modification of hte invention adapted to skim oil from the ocean's surface.


FIG. 12 is a plan view of the apparatus of FIGS.13 and 14.


FIG. 13 is a diagramatic cross-section view, in elevation, illustrating a third embodiment of the invention.


FIG. 14 is an elevation view, partially broken away, of the apparatus of FIGS. 12 and 13.


Referring to FIG. 1 there is shown a wave powered motor constructed in accordance with the present invention having a nearly hemispherically shaped member, or shell 1, which comprises the major structural element of the apparatus. The shell FIG. 1 may be fabricated from reinforced concrete, or steel, or other suitable material. The geometry of the shell will be described in greater detail hereinafter in connection with FIGS. 2, 3, 4, 5, and 6. A three-point anchorage comprising mooring blocks secured to the ocean floor and articulated linkages extending therefrom, is provided for holding the apparatus in place. Two of hte mooring blocks are shown at 2 and 3, and may comprise caisson-cast concrete piers. In lieu of the articulated linkages, (5, 6) cables, or other suitable elements may be used to connect the skirt 4 or lower edge of the shell 1 to the anchorage (2-3).


The upper central part of the shell is provided with a circular inlet 7. Depending from the circular inlet 7 is a hollow cylindrical standpipe 8 having a vertical height approximately equivalent to the height of the shell 1. Stationary inlet guide vanes 9 are secured to the shell and extend radially outward from the upper end of the standpipe 8, to the region of breaker formation and function to impart a rotational moment or swirl to water entering the standpipe 8 via inlet 7. A turbine 11 is mounted near the lower end of the standpipe 8. The swirling water in the mid-portion of the standpipe 11 comprises a fluid flywheel which imparts an angular torque to the turbine rotor 11. Water exiting from the turbine 11 passes through a diffuser 13 fixedly secured to the lower terminus of the standpipe 8.


A rotating shaft 14 extends upward from the turbine 11 to a centerbody 15 secured to the upper central portion of the shell 1 above the inlet 7. The centerbody 15 provides support for the top edges of the inlet guide vanes 9. An electrical generator 18, or other utilization device, is rotatably coupled to the upper end of the turbine shaft 14. A suitable protective cover 19 may enclose the upper portion of the centerbody 15. A waterproof conduit or cable 21 connects the electrical generator to a suitable power distribution system which may, for example, be located on shore. The neutral water level (viz., in the absence of wave action) is indicated at 22 in FIG. 1. The location of the neutral water level is not critical. It has been found that the device operates satisfactorily with the water level above or below the level shown. This means that the device may be mounted solidly in shallow water in spite of the tides.


Five separate steps are necessary for the utilization of the propagated surface wave energy. The first is the collection of energy from a considerable length of the available wavefront. For example, a concentrating device which serves 100 meters of wavefront can collect up to 4 megawatts of power from typical ocean swell having a half amplitude of one meter and a period of ten seconds. The critical requirement for the interface with the wavefront is the transmission of the wave energy across the interface rather than its reflection. Because the energy is in the form of a propagating oscillatory wave, whether or not the energy reflects is governed by whether an impedance match or an impedance mismatch exists at the interface. The invention makes use of a structure which is the surface wave equivalent of an acoustical horn to collect and concentrate the propagated surface wave energy. For any given wave of a maximum period (T), a horn shape may be generated to provide a suitable impedance match between the mouth and the throat of the horn. The outer surface shape of the shell 1 comprises the impedance transformer which may be considered as analogous to an acoustical horn. This may be visualized by considering the cross-sectional shape bouonded by the neutral water level 22 and a radial section through the shell 1. Inasmuch as this shape extends thorugh a full revolution, the actual structure is dome-shaped and functionally and physically resembles a natural circular atoll.


The oscillatory waves propagating within the "horn" consist of about 1 &fracsl 2 kinetic energy (of circular rotation) and about 1 &fracsl 2 potential energy (of elevation or depression). If these waves now encounter a sloping ramp, such as that provided by the central outer surface of the shell 1, they will crest and break. The breaking wave is now called a great primary wave of translation. All parts of the wave move horizontally in unison and the energy is mostly kinetic. The region in wich this occurs is called the surf zone. Thus, the horn/ramp combination provided by the shell 1 accepts oscillatory waves and delivers massive pulses of pure kinetic energy to the inlet of the shell.


There is shown in FIG. 2 a graphic representation of ray paths and wavefronts impinging on an atoll-shaped horn/ramp, of the type comprising the shell 1 in FIG 1. As can be seen, the linear wavefront entering from teh upper right quadrant is progressively refracted as it encounters the varying bottom contour (viz., the contour of the top of the shell). The effect is to wrap the wavefront around the atoll ina spiral which tends to converge on the center of the atoll.(next)

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Worst Pun Of The Year Every Year

Best And Most Concise Description Of Dam-Atoll

The damndest thing that ever came out of an acoustics lab

Fermat's Principle

The Patent for Dam-Atoll is now in the public domain

The Name Dam-Atoll Tells How It Extracts Ocean Wave Energy

Dam-Atoll An Amalgam Of the Concepts Dam And Atoll

Dams And Kinetic, Potential, and Mechanical Energy

River As Kinetic Energy

Kinetic Energy Transformed To Potential Energy

Potential Energy Transformed Back To Kinetic Energy

Kinetic Energy Turned Into Mechanical Energy

An Atoll Bends And Refracts The Approaching Wave

Wave Velocity

Wave Refraction

When the submerged atoll is dome-shaped, it refracts the wave path to its center

The exact shape of the atoll's dome is critical

the atoll acts as a kind of lense concentrating the wave energy

A Wave's Potential Energy Gets Changed To Kinetic Energy By An Atoll

A wave is nothing but energy

Waves And Potential And Kinetic Energy

A deep-water ocean wave is always half potential and half kinetic energy

Wave is all kinetic energy when it breaks on the center of the atoll

Changing A Wave's Kinetic Energy To Mechanical Energy By Means Of A Vortex


Vortex is a fluid flywheel

Dam-Atoll, Vortex, Guide Vanes

This in sum is how Dam-Atoll works

Smoothing out the succession of wave pulses

Advantages Over The Other Ocean Wave Energy Extraction Devices

Dam-Atoll has only one moving part

Thus Dam-Atoll loses no energy in monkey motion

Monkey motion

Competing Ocean Wave Energy Extraction Devices are monkey motion machines

Energy Efficiency

Diffuser Important To Energy Efficiency

Mathematically Optimal Shape Of Dome Crucial To Energy Efficiency

A Future So Bright For Ocean Systems You Will Need Sunglasses

The Patent for Dam-Atoll is now in the public domain

The Opportunity

Leslie Wirt is available for lectures

Leslie Wirt offers consulting services

Video of working scale model of Dam-Atoll

Dam-Atoll Patent

Michael McCormick's Comments On Dam-Atoll

John Isaac's Comments On Dam-Atoll

Links To Books, Articles, And Web Sites Mentioning Dam-Atoll

Excerpts From Scattering And Absorption Of Surface Waves By Arthur's Island

Future Prospects For Dam-Atoll

Dam-Atoll Humor


About the inventor of Dam-Atoll, Leslie S. Wirt

Contact Leslie Wirt


Next: Michael McCormick's Commentary On Dam-Atoll


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