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Energy Alternatives | Ocean Wave Tidal Marine Current Power

Ocean Power Technologies

Ocean power is as vast a subject as the immense size of the oceans, with the energy potential of the ocean being clear.

This is such a new area of renewable energy development that the ocean technologies have not even taken their first commercial breath. There are several types of ocean power technology, wave, tidal, osmotic, saline and marine current power projects are presently on the drawing board. With these projects potentially providing up to 15% of the total electrical energy needs of the US by 2030.

Presently, the US uses about 4,000 terawatt-hours (TWh) of electricity per year. It is estimated that 1,420 TWh of electricity could be supplied by different forms of ocean energy. This is a very encouraging number, if you consider that we are starting from ground zero, with no installed ocean power generating capacity.

Extremely Reliable Energy Source

The Oceans also provide an extremely reliable energy source, that can be built out to a very large scale. This is because of the massive volumes of water that are also rhythmic in nature, making ocean power a very attractive, reliable energy option for mega scale projects. There are limitations however, as these present technologies are only in the development stage. The major issue is availability of potential geographic areas of the World, where present ocean energy technologies can be deployed.

Ocean Wave Power

Attenuator Wave Energy Device

The Salter Duck an example
of a Buoyant Moored Device

Waves result from the wind blowing across the ocean, this wave power has tremendous, clean energy potential. Wave power utilization is best on the western coasts of continents between 30º and 60º latitude of both the north and southern hemispheres.

There is 2,100 terawatt-hours per year of available wave energy along the United States coast line, by just tapping 25% of that available wave energy would equal the total hydro electric dam output in the US. This immense potential energy in the oceans holds much promise as many people live on the coasts.

Waves are more reliable than both solar and wind power, coming with the added benefit of the large populations living close to the coasts, so there is potential for growth of this inexhaustible and eternal energy source. There are some of the obstacles though, including the high cost to build, and finding large enough dynamic wave zones to engineer the clean energy alternative.

The optimistic side of the story is that with the improved design and technological advances large companies and entrepreneurial investors are making even marginal wave zones developmentally practical.

Buoyant Moored Device

There are different types, the one I will point out is the "Salter Duck", in development since 1974 at Edinburgh University, the "Salter Duck", floats on the ocean's surface while cabled to the ocean floor, taking advantage of the natural, rhythmic, ocean wave motion. This benign motion can provide reliable energy in the appropriate wave zones of the world. "The Duck", is designed to have linked cylinders that freely rotate for stability during rough seas, while giving a constant tension to the seabed secure cables, the Salter Duck requires a sea depth zones of 80 metres.

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Ocean Tidal Power

PoplarGroveTideMill, Mathews County, Virginia

Poplar Grove Tide Mill, Mathews County, Virginia

Photo Credit: Frances  Johnston 1864-1952 | Library of Congress

Tidal Power is caused by the Sun and Moon's gravitational tug, with Tidal power one of humanities oldest mass scale technologies, having been used as far back as 787 AD, along the coasts of France, Spain and England.

Tidal Power in ancient times used a technology called Tide Mills that would turn water wheels, or mill grain, by having a reservoir that would store the water from the flood tide, and then this stored water would be released through a sluice gate at low tide to create rotational power, this type of Tidal Power is used up to the present day.

Tidal energy is certainly a possible future renewable energy candidate, that would be both more predictable than solar and wind energy, and can provide vast amounts of reliable energy to millions living on the coasts. Although, presently only geographically feasible in certain regions of the World, primarily on the north west coast of North America and parts of Europe, tidal power could still become a vast, reliable power source and part of the new energy equation.

Although predictable, one downside to using Tidal Power is that although the Tides hold much potential energy, they also run in 12.5 hours cycles, missing peak demand periods. There are two modern day Tidal Power technologies to harness and convert the tides into electricity, although these great engineering projects are being built to protect the environment just the environmental impact of these huge infrastructure projects, (the same concerns are around large, Hydro Electric projects), to the local environment has to be considered.
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Tidal Dams across Estuaries

Tidal Energy along the coasts of the World are captured by building Tidal Dams by placing Barrages across Estuaries that allow the high tide water through sluices, with the water released at low tides, driving hydraulic turbines to create electricity for up to 10 hours a day.

For this approach to be feasible, (and economic), a tidal range of at least 7 meters between twice daily high and low Tides are required. Unfortunately, there are not many places in the world that meet these criteria, and, this technology, given its present state of development is not viable in much of the World.

Offshore Tidal Streams

Entirely predictable energy is available through the use of offshore Tidal Streams, a new use for well known technology, with one of the few obstacles to implementation being the high installation costs, once installed they can be low maintenance, and can be driven by inexpensive, horizontal or vertical axis turbines to create electricity.

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Ocean Marine Current Power

A United States Department of the Interior 2006 report sums up the potential of marine current power, which is the momentum of ocean currents resulting from the push and pull of the tides, a result of the gravitational pull of the Sun and Moon.

The study from the United States Department of the Interior estimated that just harnessing 1/1000th of the energy potential of the Gulf Stream would provide Florida with 35% of the state's energy needs.

Ocean Osmotic Power

A sophisticated hybrid ocean, river clean power technology is osmotic power. Although experimental, using the salinity, (how much salt is in the water), and the difference in water pressure between the Sea and River water produces the potential energy. Until recently the cost of the membrane was not commercially feasible. A recent breakthrough based on an electrically modified polyethylene plastic has made this technology commercially available for development.
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