Dam
Dam-Atoll's
name tells how it extracts energy from ocean waves.
Let's take the 'dam' part first. Just as a dam captures river water and converts its energy to electricity, Dam-Atoll's underwater artificial atoll captures the wave and converts its energy to electricity. Both the dam and the artificial atoll convert water energy to electricity when the water passes through a hole in the dam/atoll to power a generator. Picture Source.
AtollSecond, consider the 'atoll' part of the name. When it has the proper shape, the submerged dome of an atoll will cause approaching waves to spiral in towards its center. This spiral bending is called wave refraction. Now let's say that the diameter of the atoll is one mile. Approaching the atoll is a wave whose crest is, say, 1,000 miles in length. Some part of that length will be affected by the atoll, and will keep bending towards the atoll until it hits the center. The center of the atoll will receive the total energy of one mile's worth of wave. That is to say, the energy received by the atoll is equal to the energy present in the length of wave equal to the diameter of the atoll. Now the wave itself is nothing but energy—a pulse traveling across the ocean—so in receiving the energy contained in a one mile segment of the thousand mile wave, the atoll has captured one mile's worth of that wave.
WaveAn ocean wave is always half potential energy and half kinetic energy so long as it is propagating in deep water. As the wave enters shallower water, this proportion changes. The kinetic portion of the wave's energy becomes greater as the water becomes shallower. Conversely, the potential energy decreases. Finally, the wave's shape changes, its front side becoming steeper until it becomes completely vertical—a moving wall of water. At this point, its energy is nearly all kinetic. This wave configuration is unstable, and the wave breaks into a churning turbulence. This turbulance converts the kinetic energy into heat, so the wave water is a little warmer as it returns to the ocean. Picture Source.
VortexA vortex is a natural swirling motion in any fluid such as water or air. If there is a hole in the center of an atoll with the proper shape, a vortex will form in that hole because the approaching waves are spiralling in towards the atoll's center. In this way, an atoll (if the reader can stomach yet one more pun) adds a special twist to the atoll's natural transformation of the wave's potential energy to kinetic energy. The really nice feature of vortexes is that very little energy is lost in them: they are, in a very real sense, fluid flywheels. Dam-Atoll, a
Dam-Atoll VideoDam-Atoll functions as an artificial atoll, bending incoming waves and focussing their energy as they spiral into the center. Vanes at the center guide the incoming spiralling waves and directs the resulting vortex into a shaft. The whirling water in the vortex transfers its energy to a mechanical component, a shaft-mounted turbine, which then runs a generator to create electrical energy. The shaft-mounted turbine is the only moving part in this beautifully and elegantly simple design. Click here to see a video of working model of Dam-Atoll. In a full-scale prototype of this
Patents, Articles, Technical DescriptionsClick here to see an html version of the patent. Click here to see commentary on Dam-Atoll by John Isaacs at the First Symposium on Wave Energy Utilization, held at Gothenburgh, Sweden. Click here to see an excerpt from the Advanced Techniques chapter of Michael E. McCormick's book, Ocean Wave Energy Conversion. Click here to see various other articles, books, and links to resources on the web discussing Dam-Atoll. Click here to see the Abstract, Table of Contents, and List of Figures of an article working out the mathematics describing the optimal shape of the artificial atoll that will result in the greatest efficiency in conversion from wave energy to electrical energy.
Future ProspectsThe world's energy requirements. Alternative energy clearly a necessity. Picture Source.
HumorHumor may not be the first thing you associate with an
HistoryThe mathematical principles explaining how atolls cause waves to refract were first worked out by the brilliant oceanographer Robert S. Arthur while he was still a graduate student at Scripps and under contract with the navy during the second World War. These mathematical principles form the basis of Dam-Atoll. Click here to see Arthur's classic paper, "The Effect Of Islands On Surface Waves." As noted by Arthur, the ancient Polynesians were aware of many of the same principles for which Arthur provided a mathematical description. Click here to see a discussion of their navigational charts composed of sticks representing islands, currents, and waves. Picture Source.
The Center Contains A Vortex
Changing A Wave's Kinetic Energy To Mechanical Energy By Means Of A Vortex:
A vortex
is a natural swirling motion in any fluid such as water or air. In water, it is often called a whirlpool. In air, it is called a tornado. A true vortex is very efficient as an energy storage device. Viscous losses are minimal, its spin persists for some time. A vortex is, in a real sense, a fluid flywheel. Dam-Atoll, Vortex, Guide Vanes:
The design of Dam-Atoll features a vertical cylindrical chamber at its center that facilitates the formation of this fluid flywheel. We've seen how the optimal shape of the atoll delivers approaching waves in a spiral path towards the center of the atoll, where the waves progressively break. A set of guide vanes at the top of Dam-Atoll's submerged dome directs each breaking wave into the vertical central vessel tangentially, resulting in a powerful whirlpool. Any wheel or array of paddles, any propeller or paddle-wheel in this whirlpool will be forced to spin at the same rate as the whirlpool. By attaching the paddles to a shaft, you will enable the shaft to deliver mechanical power, for example to an electrical generator. This, in sum, is how Dam-Atoll works. Smoothing Out The Succession Of Wave Pulses:
Each successive turning vane delivers its flow contribution in succession. This serves to smooth out the individual pulses of wave energy, much as a radial aircraft engine smooths out individual cylinder pulses. By the time the last portion of a wave enters the rear guide vanes, a new wave is just entering the first set of guide vanes. This smooth action is most clearly seen in the slow motion portion of the video focussed on the waves entering the turning vanes. (next)
Click on any of the following topics that may catch your eye
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
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
Dam-Atoll_History
About the inventor of Dam-Atoll, Leslie S. Wirt
Contact Leslie Wirt
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