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.

Atoll

Second, 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.

This is the basic principle of Dam-Atoll as an ocean wave energy concentration device.

Picture Source.

Wave

An 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.

Vortex

A 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

sea wave power station,

uses the kinetic energy of this vortex to power a turbine generating electricity. Picture Source.

Dam-Atoll Video

Dam-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

ocean wave power station,

real boats will replace the toy boats, which L.S. Wirt stole from his grandsons. Picture Source.

Patents, Articles, Technical Descriptions

Click 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 Prospects

The world's energy requirements. Alternative energy clearly a necessity. Picture Source.

Humor

Humor may not be the first thing you associate with an

ocean wave power station.

Nonetheless, humor and brilliant technical inventions sometimes spring from the same source in the inventive mind. Click here to see some Dam-Atoll related humor, starting with the name itself, Dam-Atoll (pun definitely intended). Picture Source.

History

The 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.

Refinements—The Diffuser:

As we've mentioned above, the working model of Dam-Atoll attained an efficiency of 25%. We are working on various refinements to the design to increase this efficiency. One refinement regards how the water returns to the ocean after its kinetic energy has been transferred to the shaft. A major factor affecting efficiency is how you handle this downstream water. If it returns to the ocean through a properly shaped duct, called a diffuser, this helps suck the water back into the ocean in a way that does not reduce Dam-Atoll's efficiency.

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A Crucial Refinement—The Proper Shape Of The Dome

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