The Age of Undersea Windmills Begins

Posted on March 16, 2006
Posted By: Harry Valentine
 
An announcement was made during late February in Bermuda advising that construction was to begin on an undersea windmill installation that will provide up to 10% of Bermuda's electricity. This project will be the first commercial application of a technology that can generate electrical power ocean currents. It is a concept that has been debated, researched and debated over several years. Unlike tidal power stations that can only generate power for up to 10-hours per day, installations like the proposed Bermuda project could generate power throughout the day.

The installation at Bermuda may be the "proof of concept" and the basis upon which larger and more powerful versions of this technology may be developed. There are numerous other locations around the world where prevailing ocean conditions would favour larger installations that have higher generation capacity. While the construction and installation cost of the technology may be high, its operating cost over long-term is expected to be comparable to that of shore-based hydroelectric installations. Several favourable locations where undersea windmills may be installed actually lie outside of heavily traveled commercial shipping lanes. Some of the locations would include:

Strait of Florida:

The Gulf Stream flows from the Gulf of Mexico and a portion of it flows into the 12-mile wide channel entrance to the channel that lies between Key Largo and the southeast tip of Florida. This channel gently converges over 15-miles to a width of 2-miles and water depth is less than 150-ft. The current at this point in the channel may be strong enough to enable undersea windmills to generate an estimated 10-megawatts of electric power that may mainly be used in the Florida Keys.

Bahamas:

A portion of the Gulf Stream flows from Florida Strait into the Northwest Providence Channel of the Bahamas and through the 30-mile wide entrance to Little Bahama Bank that lies between Grand Bahama and Great Abaco Islands. The Gulf Stream and Equatorial Current merge in this region and flow into the Atlantic through a 2-mile wide exit between Little Abaco and Great Abaco Islands and also through an 8-mile wide exit that lies between Little Abaco and Grand Bahama Islands. Undersea windmills capable of generating over 100-megawatts of electric power may be installed at these exists that are less than 150-ft in depth.

Trinidad and Tobago:

A portion of the South Equatorial Current diverges to the northwest along the Brazilian coast toward the islands of Trinidad and Tobago. These islands form an angle that captures a band of ocean current that is 80-miles wide and within a distance of 20-miles, the band of current converges into the 20-mile wide channel that lies between the 2-islands. This causes a strong ocean current to flow through the channel where the water depth is less than 150-ft near Trinidad and less than 600-ft near Tobago. At the present time electricity on these islands is generated using natural gas and diesel. In the long-term future, a "farm" of large undersea windmills that could be installed in the channel near Tobago and generate up to 1000-megawatts of power.

Indonesia:

As the Equatorial Counter Current moves eastward across the Indian Ocean, the 45-degree angle of the Sumatra coastline will deflect a wide band of ocean current toward the 45-mile wide entrance to Sunda Strait that lies between Sumatra and Java. The strait is 80-miles long and converges to a width of 10-miles near its exist. The water depth rises from over 6000-ft in the Indian Ocean (200-miles to the east) to under 150-ft at the narrowest point in the strait. The converging strait would assure that a fast current would flow through undersea windmills located at the narrowest point. These units may need to be built to a restricted height so as to allow ships with deep keels to pass overhead. Alternatively, special shipping lanes may be implemented in Sunda Strait so as allow the maximum height of windmills to operate there.

Indonesia may have a potential of over 2000-megawatts of tidal electric power, much of which could be sold to Singapore where power stations consume expensive natural gas to produce power. A portion of the Indonesian tidal power may be used to generate hydrogen that would be sold to markets in Japan, China, Hong Kong and possibly Singapore. If the Government of Indonesia is willing, private investors could finance the installation of ocean power conversion systems around Indonesia.

New Zealand:

There are two sites around New Zealand's South Island where undersea windmills may be installed. The angle formed by South Island and Stewart Island captures a 70-mile wide band of the West Wind Drift Ocean Current and forces it to converge into the 20-mile wide Foveaux Strait. The water depth changes rapidly from under 600-ft outside the strait to under 150-feet in the strait. The combined convergence of width and depth causes a strong current to flow in the strait where a "farm" of undersea windmills may be installed and generate up to 1000-megawatts of power.

A portion of the West Wind Drift merges with the East Australian Current and is deflected to flow in a northeasterly direction along the 500-mile west coast of New Zealand's South Island and into the 60-mile wide (north - south distance) entrance to Cook Strait. Twice a day an eastward-moving band of tidal rise from the Tasman Sea that is 450-miles wide would combine with this ocean current. The converging angle made by New Zealand's two main islands would funnel the tidal rise into the entrance of Cook Strait that further converges to a width of 12-miles at its narrowest point.

For power to be generated in Cook Strait, undersea windmills may need to be installed between Cape Jackson and Kapiti Island where the water depth is less than 600-feet. This channel may be made narrower by building breakwaters and shallower by depositing rocks and boulders on the channel floor. The reduced width and depth of the flow of water would increase the speed of the current that would flow through the artificially narrowed channel where up to 2000-megawatts of electric power could be generated. A designated shipping channel may have to be implemented in Cook Strait at a future time if power from the ocean is to be generated there. This power generation would be complimented by New Zealand's high capacity for hydraulic energy storage.

Australia:

The West Wind Drift Ocean Current moves eastward along the southern coast of Australia and into Bass Strait. The angle that of southwest coast of the State of Victoria deflects a 165-mile band of this ocean current into the 40-mile wide channel between Cape Otway and King Island. The sea floor also rises over 120-miles from a depth of over 6000-ft outside the channel to under 600-ft in the channel. This combined convergence of width and height would assure that a strong tidal current would flow in this channel where in the distant future, a "farm" of undersea windmills may be installed between King Island and Cape Otway and generate some 3,000-megawatts of power from the ocean current.

Other Sites:

There a numerous other suitable straits and channels around the world where the combination of ocean currents, ocean tides, changes in ocean depth and converging coastlines (wide entrance and narrow exit) allow undersea windmills to be installed to generate power. The list of such sites would include:

  • Tsugaru-kaikyo channel between Hokkaido and Honshu in Japan;
  • Muskeget Channel between Martha's Vinyard and Nantucket Island, USA;
  • The deeper channel in Strait of Dover (below depth of ships’ keels);
  • The entrance to the Strait of Gibraltar (below depth of ships' keels);
  • Dardenelles, Turkey (below depth of ships' keels);
  • Strait of Bab el Mandeb (below depth of ships’ keels);
  • The channel between St Vincent Gulf and Encounter Bay, Australia;
  • The channel between Fraser Island and Eastern Australia;
  • The channel between New Britain and Papua New Guinea

Technology:

Submersible windmills are being installed in rivers such as the Hudson River near New York City. Bi-directional undersea windmills are being tested for future use at ocean inlets where power would be generated from the twice-daily change in ocean tides. As the technology develops in the future, larger undersea windmills with much greater generation capacity will appear. Power generation from undersea windmills will be more consistent than power generation from land-based windmills. The ocean tides and currents are more reliable than prevailing winds and ocean water has 870-times the density of air. Undersea power generation technology is likely to become more viable in the long-term future and may do so in the absence of special tax breaks and subsidies from governments. The pioneering installation in Bermuda may be the forerunner of a technology that will serve the economic needs of many nations in the long-term future.

 
 
Authored By:
Harry Valentine holds a degree in engineering and has a backround in free-market economics. He has undertaken extensive research into the field of transportation energy over a period of 20-years and has published numerous technical articles on the subject. His economics commentaries have included several articles on issues that pertain to electric power generation. He lives in Canada and can be reached by e-mail at harryc@ontarioeast.net .
 

Other Posts by: Harry Valentine

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Comments

March, 17 2006

Graham Cowan says

That seawater is ~860 times denser than sea-level air, we knew. But we don't know, or anyway I don't know, how fast ocean currents flow through the mentioned straits. The potential megawattages have been reported, so those speed data must be available. Valentine should put them in.

March, 21 2006

William Quaintance says

What about the impact on sea animals? Unlike with wind, heavy ocean currents attract high concentrations of ocean life. The impact on ocean life per MW generated will probably be much higher than wind, unless the turbines spin much slower. And large animals might be impacted by even slow turbines. This subject will need research.

March, 21 2006

Roger Bedard says

Two questions for the author

1. The first sentence says that "An announcement was made during late February in Bermuda advising that construction was to begin on an undersea windmill installation that will provide up to 10% of Bermuda's electricity" I ask the author to confirm whether it is in fact "permitting" and not "construction" that is to begin as it is my understanding that a permit and license must be obtained before contruction can begin.

2. I ask the author why he chose to cite the Muskeget Channel site as the only example of a North America in stream tidal site when in fact the Muskeget Channel energy resource is probably not worth harnessing (because of low energy resource and high cost of grid interconnection) and ignored mentioning dozens of others including those in the Bay of Fundy, Cook Inlet, Northwest Passage, Puget Sound and San Francisco Bay

March, 21 2006

Graham Cowan says

Birds are much denser than air and to stay up in it must maintain a high mass flow ot it past them that they divert downward; they must fly fast. Sea creatures are at or very near neutral buoyancy, so don't have to go fast, so would not tend to die like birds on striking a turbine blade. (And predictable strong air winds do, surely, attract migrating birds.) So if, as I don't expect, seawater flow turbines were to be built, they would harm only investors, not fish.

--- Graham Cowan, former hydrogen fan
B: internal combustion, nuclear cachet

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