Wednesday, January 12, 2011


The following paper was presented by Leighton Chong at the Eco-Balance Conference held in Tokyo last month:


Ostrager Chong Flaherty & Broitman, 133 Kaai Street, Honolulu, HI 96821, USA 

Hawaii Natural Energy Institute, c/o 2101 Nuuanu Avenue, PHA2, Honolulu, HI 96819, USA 


In the vastness of the ocean’s resources lies our future. Many countries of the world have coastal boundaries with Exclusive Economic Zones (EEZ) that extend out 200 miles (340 km) into the sea. In the open ocean, cold seawater from 1000 meter depths can be pumped to the surface and used to produce electricity by ocean thermal energy conversion (OTEC).  

The effluent would have very high mineral concentrations with a Redfield Ratio ideal for stimulating the growth of the total life cycle.  Marine biomass can be harvested for conversion into biofuels, and next generation fisheries can be supported. A “Blue Revolution” in the use of oceans as the ultimate sustainable resource has promising potential for a wide range of sustainable uses -- renewable energy, bioresource materials, integrated marine habitats, marine biomass plantations, aquaculture fisheries, ocean cities, etc.  Near-term technologies are being developed to enable ocean plantships to be deployed for ocean thermal energy conversion (OTEC) and aquaculture. These developments have the potential to provide significant economic returns and environmental benefits outweighing projected costs and ecosystem impacts. 

Keywords: ocean, resource, OTEC, aquaculture 


The so-called “Blue Revolution” is much more than a marine version of the Green Revolution. This marine cornucopia encompasses a wide range of sustainable products -- renewable energy, potable water, bioresource plantations, next generation fisheries, biofuel products, green material and a variety of integrated marine habitats -- while in the process improving the ocean environment through, perhaps, cooling surface water temperatures to  prevent the formation of hurricanes and absorbing carbon dioxide to remediate global climate warming.   

Twenty latitude degrees above and below the equator, the tropical ocean waters are currently considered to be a wet desert, for nothing much grows near the surface. This is because of a lack of nutrients. However, at 1000 meter depths is deep ocean water at 5 degrees Celsius with nitrogen and phosphorous concentrations at 100 times and 20 times, respectively, greater than what is generally found at the surface. This is because life in the photic or euphotic zone, where sufficient sunlight penetrates for photosynthesis to occur, eventually settles into the ocean depths and decomposes in the exact ratio as is required for life at the surface. The deeper ocean depth is cold because of natural convection from the Arctic and Antarctica. 

Marine life in cellular form is said to be from two to five times more efficient in converting sunlight to biomass than any land crop (trees, grasses). Part of the reason is that land plants need to draw nutrients through a root system, while marine life can utilize the entire surface area contacting the aquatic environment. 

The surface of our planet is 71% water. While we largely occupy only two dimensions on land, the average depth of the ocean is 13,124 feet. The oceans have vast potential for supplying clean energy, including windpower at sea, wavepower, tidal power, marine current power, salinity gradient, marine biomass, and ocean thermal energy conversion. 

Deep Ocean Upwelling and Aquaculture 

Natural upwelling brings some of this rich fluid to the surface over only one tenth of one percent of the ocean, where nearly half the wild seafood is harvested, unfortunately so efficiently that all existing fisheries are in various degrees of endangerment. If large volumes of this rich deep-ocean water can be brought to the surface, ocean ranches can be supported, where the growth cycle would be closed, phytoplanktonic life fertilized by the effluent from an OTEC plantship, in a system where irrigation using 
precious freshwater would not be necessary. The timing would be ideal because all existing fisheries are now reported to be declining, at a time when demand is increasing because of population growth and changing nutritional trends. 

The Blue Revolution envisions widespread industrial- scale deployments of grazing platforms where cold ocean water from as deep as 1000 meters would both serve to produce electricitythrough OTEC and initiate new surface biogrowth.  Ocean water from 1000 meters deep is cold (around 5 degrees C) and relatively pathogen free, and has a Redfield ratio with high nutrient concentrations, e.g., 200 times higher in nitrates and 20 times so for phosphates than surface waters.  This dual use of upwelled cold ocean water would enable widespread deployment of grazing OTEC plantships for ocean aquaculture the full range of co- products. 

Aquaculture already supplies about half of global seafood production, with the leading countries being China (70%), India (5%), Vietnam (2.5%), Thailand (2%), Indonesia (2%), Bangladesh (2%), Japan (1.5%), Chile (1.5%), Norway (1.5%), and United States (1.5%) [7].  Not only is this a $25 billion annual industry, but the trend towards less red meat and the nutritional benefits of certain seafood commodities will only increase, and more so with a continued growth of the world population.  Most aquaculture today is practiced in on-shore or near-shore waters contiguous to land. However, limits on available land space and clean water supplies, as well as problems with pollution from effluents, waste feed, and excrement and other environmental considerations, make expansion of on-shore or near-shore aquaculture problematic. 

Operation in deep ocean waters can avoid these constraints and pollution problems by utilizing vast open ocean spaces, diffusion of pollution through ocean mixing, and the bacteria-free, nutrient-rich cold waters are ideal for stimulating growth of marine biomass that may be used for sustainable feed. The ultimate goal would be a self- supporting sustainable marine ecosystem where the energy would be provided by OTEC, nutrients from the effluent, and feed though closure of the growth cycle.  Some day, even growing cages could be eliminated through the use of nutrient or thermal barriers. Certainly, harvesting, while prosaic, could be acoustically driven. 

It is clear that the Blue Revolution marine system would have significant environmental and ecological benefits over current energy-intensive, petroleum-driven farms, and, even, aquaculture operations. The potential for deep ocean aquaculture [1] was first described in “The Ultimate Ocean Ranch”, by co-authors Fujio Matsuda, James Szyper, Patrick Takahashi and Joseph Vadus, Sea Technology, August 19991, at a time when the United Nations reported that nearly 30% of world fish stocks were either overexploited or depleted [2], and was further documented in a subsequent U.S.-Japan panel [3]

Deep Ocean Water for OTEC-Powered Plantships 

The temperature differential between 1000-meter and surface waters can be utilized for Ocean Thermal Energy Conversion (OTEC), producing both net positive electricity and freshwater. OTEC power generation in deep ocean waters can support integrated plantations or plantships to produce a wide variety of marine bioproducts, including seafood, biopharmaceuticals, bioresource materials, biofuels, etc. In the very long term, there is reason to believe that integrated OTEC-powered plantships could become floating cities, and, of course, countries.  

Under the United Nations Convention of the Law of the Sea, countries with coastal boundaries have exclusive economic zones (EEZ) extending 200 nautical miles (370 km) from shore. OTEC-powered plantships have the potential for growing, harvesting, and processing a wide range of products in spacious ocean environments far off-shore, certainly to the full 200-mile extent of the EEZ, but also beyond. Such ocean plantships can use artificially-induced upwelling of cold deep-ocean water containing nutrients to enhance biological food productivity unencumbered by 
land-based or near-shore aquaculture limitations. Large- scale employment of ocean plantships could have beneficial environmental effects of reducing acidification of surface waters, curtailing carbon emissions, reducing land and water usage through production of seafood as an alternative to meat, and minimizing the formation of hurricanes by cooling ocean surface waters. 

Someday, perhaps, a thousand OTEC-powered Blue Revolution nations could well be plying our oceans, providing clean and sustainable resources for humanity in harmony with the ocean environment.  Picture a United Nations with 1192 members.  Then, again, maybe you shouldn’t, but do dream that by then we can hope to have overcome Peak Oil and Global Warming. 

Near-Term Technologies for Ocean Plantships 

Offshore platforms are widely used for oil drilling, housing workers and support machinery [4]. But moored systems will not be used for OTEC. Semi-submersible platforms have submerged hulls (columns and pontoons) of sufficient buoyancy to cause the structure to float, but with ballasted weight sufficient to keep the structure upright, and can be used in the open ocean to unlimited depths. Very large floating structure (VLFS) technology is also being explored. 

Lockheed Martin, with their engineering team, is designing to a 5 MW OTEC pilot plant [5] in partnership, reportedly, with the State of Hawaii and the Taiwan Industrial Technology Research Institute for the U.S. Navy off Barbers Point on Oahu.  LM also hopes, in Phase 2, to build a 100 MW OTEC plantship to sell baseload electricity and freshwater to Honolulu. 

The Lockheed Martin work will draw upon expertise across many divisions of the company.  For example, the OTEC team is using an advanced composite material developed by Lockheed Martin Space Systems to make the OTEC cold-water induction pipe, and fuel tank technology used for the Space Shuttle will be used to make low-cost heat exchangers for the OTEC plant.  It will also explore producing desalinated water from the ocean and hydrogen- based fuels. The LM team is partnering with Makai Ocean Engineering and other Hawaii companies and the University of Hawaii.  Research work at UH by Gerard Nihous in ocean thermal mapping  shows that the leeward (southwest) side of the Hawaiian Islands may provide ideal thermal gradient conditions for OTEC plantships (see figure below) [6].

Kajima Corp., a civil engineering and construction firm in Japan, has plans to build the world's largest ocean current turbine for electricity generation, possibly in Hawaii.  The largest today is the SeaGen turbine built by Marine Current Turbines, Bristol, UK, which generates 3 MW of power, enough to meet the energy needs of 1,000 homes. Twin 15-metre rotors are spun by the force of ocean currents. Almost entirely submerged, silent and immovable, the system has numerous environmental benefits, along with its clean energy generation.  However, there are no co-products, for electricity is the only output. 

Shimizu Corp., an architectural engineering firm in Japan with world-wide operations, is planning for a large “Green Floating Island” with an OTEC plant and next generation fisheries [7], possibly in Hawaii. Another floating island proposal by Whim Architecture, Netherlands, envisions a “Recycled Island” built from the sea of waste plastic that has accumulated in the Pacific Ocean deadzone between San Francisco and Hawaii. The floating island is proposed to be as big as the Island of Hawaii (approximately 10,000 sq km). The island would be totally self-sufficient, capable of producing its own food, managing waste and producing renewable energy. One section of the island would be for urban housing, built from recycled plastic, and would also include all the necessary amenities for recreation, commerce, and living. The rest of the island would be available to grow food, and seaweed would be grown right offshore. 

A proposal for growing yellowfin and bigeye tuna in large, autonomous, OTEC-powered ocean vessels off Kawaihae Harbor of the Island of Hawaii has been put forward by Hawaii Oceanic Technology Inc., Honolulu, Hawaii. [8]  A life cycle assessment of the Hawaii Oceanic Oceanspheres proposal indicates that it could earn revenues 4X greater than costs on harvest of 1,000 tons (909,000 kg) per vessel per year over a 10-year service life, and that impacts on the environment and local economy would be on balance positive.  Someday, in the transition to the Ultimate Ocean Ranch, these cage culture systems could be integrated into a Blue Revolution network, for a closed growth cycle can eliminate the cost of artificial feeding. 

The concept of next generation fisheries holds attractive promise, with a range of economic and health benefits, and, even, possible environmental enhancements. In the open ocean, protein farming can be transferred away from populated areas, easing the competition for land and water [9]. Future ocean ranches can be scaled to industrial capacities and deployed to the extent of any country’s EEZ. 


The Blue Revolution envisions development of our oceans as the ultimate sustainable resource with promising potential for a wide range of sustainable products, including generation of renewable energy, production of bioresource materials, creation of integrated marine habitats, production of marine biomass for biofuels, supplying mariculture seafood, etc.  Artificial upwelling of large volumes of pathogen-free, nutrient-rich cold water can be used for both OTEC power generation and stimulating marine life growth for aquaculture.  These near-term developments have potential for significant economic returns and environmental enhancements. 

Blue Revolution Concept: deep cold ocean water upwelling for OTEC generation and aquaculture

Ocean thermal map shows steepest gradient for OTEC on southwest side of Hawaiian Islands (source: Gerard Nihous

Proposed Lockheed Martin ocean OTEC plant to supply Honolulu with baseload electricity and freshwater 

Proposed Hawaii Oceanic semi-buoyant “Oceanspheres” for growing tuna beneath surface in open ocean waters 


[1] Matsuda, F., J. Szyper, P. Takahashi and J. Vadus, “The Ultimate Ocean Ranch,” Sea Technology, August 1999.  

[2] Food and Agricultural Organization of the United Nations (FAO), 1998, Web site: 

[3] Matsuda, F., T. Sakou, M. Takahashi, J. Szyper, J. Vadus and P. Takahashi, “U.S.-Japan Advances in the Development of Open-Ocean Ranching,” 2001 U.S.-Japan Natural Resources Panel Meeting, Tokyo. 

[4] Wikipedia, “Offshore Platform”,  

[5] The Monitor, “Lockheed Martin Looks to the Ocean as Global Energy Source”, November 2009, 

[6] Gerard Nihous, “Mapping available Ocean Thermal Energy Conversion resources around the main Hawaiian Islands”, AIP Journal of Renewable and Sustainable Energy, July 15, 2010, 

[7]  Shimizu Corp., “Green Floating Island”, 

[8] Ahi Aquaculture Project, Kohala Coast, Hawaii, of Hawaii Oceanic Technology, Honolulu, HI, 

[9] “Fish Farming May Soon Overtake Cattle Ranching”, Lester R. Brown, Earth Policy Institute, Oct. 2000,  



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