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Ocean Thermal Energy Conversion
www.OceanThermalEnergyConversion.org

Our company and our partners provide "turnkey" Ocean Thermal Energy Conversion  "OTEC" development services. 

There may not be a cleaner, greener, "EcoGeneration" power and energy technology than Ocean Thermal Energy Conversion. Ocean Thermal Energy Conversion is the technology and process of making "clean" electricity from the energy available in the world's oceans.  

Cooler, Cleaner, Greener Power & Energy Solutions project development services are one of our specialties. These projects are Kyoto Protocol compliant and generate clean energy and significantly fewer greenhouse gas emissions. Unlike most companies, we are equipment supplier/vendor neutral. This means we help our clients select the best equipment for their specific application. This approach provides our customers with superior performance, decreased operating expenses and increased return on investment. 

Cogeneration Technologies provides project development services that generate clean energy and significantly reduce greenhouse gas emissions and carbon dioxide emissions. Included in this are our turnkey "ecogeneration" products and services which includes renewable energy technologies, waste to energy, waste to watts and waste heat recovery solutions.  Other project development technologies include; Anaerobic Digester, Anaerobic Lagoon, Biogas Recovery, BioMethane, Biomass Gasification, and Landfill Gas To Energy, project development services. 

Products and services provided by Cogeneration Technologies includes the following power and energy project development services: 

  • Project Engineering Feasibility & Economic Analysis Studies  

  • Engineering, Procurement and Construction

  • Environmental Engineering & Permitting 

  • Project Funding & Financing Options; including Equity Investment, Debt Financing, Lease and Municipal Lease

  • Shared/Guaranteed Savings Program with No Capital Investment from Qualified Clients 

  • Project Commissioning 

  • 3rd Party Ownership and Project Development

  • Long-term Service Agreements

  • Operations & Maintenance 

  • Green Tag (Renewable Energy Credit, Carbon Dioxide Credits, Emission Reduction Credits) Brokerage Services; Application and Permitting

For more information: call us at: 832-758-0027

We are Renewable Energy Technologies specialists and develop clean power and energy projects that will generate a "Renewable Energy Credit," Carbon Dioxide Credits  and Emission Reduction Credits.  Some of our products and services solutions and technologies include; Absorption Chillers, Adsorption Chillers, Automated Demand Response, Biodiesel Refineries, Biofuel Refineries, Biomass Gasification, BioMethane, Canola Biodiesel, Coconut Biodiesel, Cogeneration, Concentrating Solar Power, Demand Response Programs, Demand Side Management, Energy Conservation Measures, Energy Master Planning, Engine Driven Chillers, Geothermal Heatpumps, Groundsource Heatpumps, Solar CHP, Solar Cogeneration, Rapeseed Biodiesel, Solar Electric Heat Pumps, Solar Electric Power Systems, Solar Heating and Cooling, Solar Trigeneration, Soy Biodiesel, Trigeneration, and Watersource Heatpumps.

What is Ocean Thermal Energy Conversion? 

The oceans cover a little more than 70 percent of the Earth's surface. This makes them the world's largest solar energy collector and energy storage system. On an average day, 60 million square kilometers (23 million square miles) of tropical seas absorb an amount of solar radiation equal in heat content to about 250 billion barrels of oil. If less than one-tenth of one percent of this stored solar energy could be converted into electric power, it would supply more than 20 times the total amount of electricity consumed in the United States on any given day.

Ocean Thermal Energy Conversion, or "OTEC," is an energy technology that converts solar radiation to electric power. OTEC systems use the ocean's natural thermal gradient—the fact that the ocean's layers of water have different temperatures—to drive a power-producing cycle. As long as the temperature between the warm surface water and the cold deep water differs by about 20°C (36°F), an OTEC system can produce a significant amount of power. The oceans are thus a vast renewable resource, with the potential to help us produce billions of watts of electric power. This potential is estimated to be about 1013 watts of baseload power generation, according to some experts. The cold, deep seawater used in the OTEC process is also rich in nutrients, and it can be used to culture both marine organisms and plant life near the shore or on land.

Ocean's Thermal Gradient Map

The economics of energy production today have delayed the financing of a permanent, continuously operating OTEC plant. However, OTEC is very promising as an alternative energy resource for tropical island communities that rely heavily on imported fuel. OTEC plants in these markets could provide islanders with much-needed power, as well as desalinated water and a variety of mariculture products.

Benefits of Ocean Thermal Energy Conversion

We can measure the value of an ocean thermal energy conversion (OTEC) plant and continued OTEC development by both its economic and noneconomic benefits. OTEC's economic benefits include these:

  • Helps produce fuels such as hydrogen, ammonia, and methanol

  • Produces baseload electrical energy

  • Produces desalinated water for industrial, agricultural, and residential uses

  • Is a resource for on-shore and near-shore mariculture operations

  • Provides air-conditioning for buildings

  • Provides moderate-temperature refrigeration

  • Has significant potential to provide clean, cost-effective electricity for the future.

OTEC's noneconomic benefits, which help us achieve global environmental goals, include these:

  • Promotes competitiveness and international trade

  • Enhances energy independence and energy security

  • Promotes international sociopolitical stability

  • Has potential to mitigate greenhouse gas emissions resulting from burning fossil fuels.

In small island nations, the benefits of OTEC include self-sufficiency, minimal environmental impacts, and improved sanitation and nutrition, which result from the greater availability of desalinated water and mariculture products.

Background and History of OTEC TechnologyNatural Energy Laboratory

In 1881, Jacques Arsene d'Arsonval, a French physicist, was the first to propose tapping the thermal energy of the ocean. Georges Claude, a student of d'Arsonval's, built an experimental open-cycle OTEC system at Matanzas Bay, Cuba, in 1930. The system produced 22 kilowatts (kW) of electricity by using a low-pressure turbine. In 1935, Claude constructed another open-cycle plant, this time aboard a 10,000-ton cargo vessel moored off the coast of Brazil. But both plants were destroyed by weather and waves, and Claude never achieved his goal of producing net power (the remainder after subtracting power needed to run the system) from an open-cycle OTEC system.

Then in 1956, French researchers designed a 3-megawatt (electric) (MWe) open-cycle plant for Abidjan on Africa's west coast. But the plant was never completed because of competition with inexpensive hydroelectric power. In 1974 the Natural Energy Laboratory of Hawaii (NELHA, formerly NELH), at Keahole Point on the Kona coast of the island of Hawaii, was established. It has become the world's foremost laboratory and test facility for OTEC technologies.

In 1979, the first 50-kilowatt (electric) (kWe) closed-cycle OTEC demonstration plant went up at NELHA. Known as "Mini-OTEC," the plant was mounted on a converted U.S. Navy barge moored approximately 2 kilometers off Keahole Point. The plant used a cold-water pipe to produce 52 kWe of gross power and 15 kWe net power.Natural Energy Laboratory

In 1980, the U.S. Department of Energy (DOE) built OTEC-1, a test site for closed-cycle OTEC heat exchangers installed on board a converted U.S. Navy tanker. Test results identified methods for designing commercial-scale heat exchangers and demonstrated that OTEC systems can operate from slowly moving ships with little effect on the marine environment. A new design for suspended cold-water pipes was validated at that test site. Also in 1980, two laws were enacted to promote the commercial development of OTEC technology: the Ocean Thermal Energy Conversion Act, Public Law (PL) 96-320, later modified by PL 98-623, and the Ocean Thermal Energy Conversion Research, Development, and Demonstration Act, PL 96-310.

At Hawaii's Seacoast Test Facility, which was established as a joint project of the State of Hawaii and DOE, desalinated water was produced by using the open-cycle process. And a 1-meter-diameter cold-seawater/0.7-meter-diameter warm-seawater supply system was deployed at the Seacoast Test Facility to demonstrate how large polyethylene cold-water pipes can be used in an OTEC system.

In 1981, Japan demonstrated a shore-based, 100-kWe closed-cycle plant in the Republic of Nauru in the Pacific Ocean. This plant employed cold-water pipe laid on the sea bed to a depth of 580 meters. Freon was the working fluid, and a titanium shell-and-tube heat exchanger was used. The plant surpassed engineering expectations by producing 31.5 kWe of net power during continuous operating tests.

Later, tests by the U.S. DOE determined that aluminum alloy can be used in place of more expensive titanium to make large heat exchangers for OTEC systems. And at-sea tests by DOE demonstrated that biofouling and corrosion of heat exchangers can be controlled. Biofouling does not appear to be a problem in cold seawater systems. In warm seawater systems, it can be controlled with a small amount of intermittent chlorination (70 parts per billion per hour per day).Vertical-Spout Evaporator

In 1984, scientists at a DOE national laboratory, the Solar Energy Research Institute (SERI, now the National Renewable Energy Laboratory), developed a vertical-spout evaporator to convert warm seawater into low-pressure steam for open-cycle plants. Energy conversion efficiencies as high as 97% were achieved. Direct-contact condensers using advanced packings were also shown to be an efficient way to dispose of steam. Using freshwater, SERI staff developed and tested direct-contact condensers for open-cycle OTEC plants.

British researchers, meanwhile, have designed and tested aluminum heat exchangers that could reduce heat exchanger costs to $1500 per installed kilowatt capacity. And the concept for a low-cost soft seawater pipe was developed and patented. Such a pipe could make size limitations unnecessary, as well as improve the economics of OTEC systems.

Open-Cycle OTEC Plant

In May 1993, an open-cycle OTEC plant at Keahole Point, Hawaii, produced 50,000 watts of electricity during a net power-producing experiment. This broke the record of 40,000 watts set by a Japanese system in 1982. Today, scientists are developing new, cost-effective, state-of-the-art turbines for open-cycle OTEC systems.

OTEC Plant Design and Location

Commercial ocean thermal energy conversion (OTEC) plants must be located in an environment that is stable enough for efficient system operation. The temperature of the warm surface seawater must differ about 20°C (36°F) from that of the cold deep water that is no more than about 1000 meters (3280 feet) below the surface. The natural ocean thermal gradient necessary for OTEC operation is generally found between latitudes 20 deg N and 20 deg S. Within this tropical zone are portions of two industrial nations—the United States and Australia—as well as 29 territories and 66 developing nations. Of all these possible sites, tropical islands with growing power requirements and a dependence on expensive imported oil are the most likely areas for OTEC development.

Commercial OTEC facilities can be built on

       * Land or near the shore
       * Platforms attached to the shelf
       * Moorings or free-floating facilities in deep ocean water.

Land-Based and Near-Shore Facilities

Land-based and near-shore facilities offer three main advantages over those located in deep water. Plants constructed on or near land do not require sophisticated mooring, lengthy power cables, or the more extensive maintenance associated with open-ocean environments. They can be installed in sheltered areas so that they are relatively safe from storms and heavy seas. Electricity, desalinated water, and cold, nutrient-rich seawater could be transmitted from near-shore facilities via trestle bridges or causeways. In addition, land-based or near-shore sites allow OTEC plants to operate with related industries such as mariculture or those that require desalinated water.

Favored locations include those with narrow shelves (volcanic islands), steep (15-20 deg) offshore slopes, and relatively smooth sea floors. These sites minimize the length of the cold-water intake pipe. A land-based plant could be built well inland from the shore, offering more protection from storms, or on the beach, where the pipes would be shorter. In either case, easy access for construction and operation helps lower the cost of OTEC-generated electricity.

Land-based or near-shore sites can also support mariculture. Mariculture tanks or lagoons built on shore allow workers to monitor and control miniature marine environments. Mariculture products can be delivered to market with relative ease via railroads or highways.

One disadvantage of land-based facilities arises from the turbulent wave action in the surf zone. Unless the OTEC plant's water supply and discharge pipes are buried in protective trenches, they will be subject to extreme stress during storms and prolonged periods of heavy seas. Also, the mixed discharge of cold and warm seawater may need to be carried several hundred meters offshore to reach the proper depth before it is released. This arrangement requires additional expense in construction and maintenance.

OTEC systems can avoid some of the problems and expenses of operating in a surf zone if they are built just offshore in waters ranging from 10 to 30 meters deep (Ocean Thermal Corporation 1984). This type of plant would use shorter (and therefore less costly) intake and discharge pipes, which would avoid the dangers of turbulent surf. The plant itself, however, would require protection from the marine environment, such as breakwaters and erosion-resistant foundations, and the plant output would need to be transmitted to shore.

Shelf-Mounted Facilities

To avoid the turbulent surf zone as well as to have closer access to the cold-water resource, OTEC plants can be mounted to the continental shelf at depths up to 100 meters. A shelf-mounted plant could be built in a shipyard, towed to the site, and fixed to the sea bottom. This type of construction is already used for offshore oil rigs. The additional problems of operating an OTEC plant in deeper water, however, may make shelf-mounted facilities less desirable and more expensive than their land-based counterparts. Problems with shelf-mounted plants include the stress of open-ocean conditions and more difficult product delivery. Having to consider strong ocean currents and large waves necessitates additional engineering and construction expense. Platforms require extensive pilings to maintain a stable base for OTEC operation. Power delivery could also become costly because of the long underwater cables required to reach land. For these reasons, shelf-mounted plants are less attractive for near-term OTEC development.

Floating Facilities

Floating OTEC facilities could be designed to operate off-shore. Although potentially preferred for systems with a large power capacity, floating facilities present several difficulties. This type of plant is more difficult to stabilize, and the difficulty of mooring it in very deep water may create problems with power delivery. Cables attached to floating platforms are more susceptible to damage, especially during storms. Cables at depths greater than 1000 meters are difficult to maintain and repair. Riser cables, which span the distance between the sea bed and the plant, need to be constructed to resist entanglement.

As with shelf-mounted plants, floating plants need a stable base for continuous OTEC operation. Major storms and heavy seas can break the vertically suspended cold-water pipe and interrupt the intake of warm water as well. To help prevent these problems, pipes can be made of relatively flexible polyethylene attached to the bottom of the platform and gimballed with joints or collars. Pipes may need to be uncoupled from the plant to prevent damage during storms. As an alternative to having a warm-water pipe, surface water can be drawn directly into the platform; however, it is necessary to locate the intake carefully to prevent the intake flow from being interrupted during heavy seas when the platform would heave up and down violently.

If a floating plant is to be connected to power delivery cables, it needs to remain relatively stationary. Mooring is an acceptable method, but current mooring technology is limited to depths of about 2000 meters (6560 feet). Even at shallower depths, the cost of mooring may prohibit commercial OTEC ventures.

An alternative to deep-water OTEC may be drifting or self-propelled plantships. These ships use their net power on board to manufacture energy-intensive products such as hydrogen, methanol, or ammonia (Francis, Avery, and Dugger 1980).

Less-Developed Countries with Adequate Ocean-Thermal Resources 25 Kilometers or Less from Shore

Country/Area

Temperature Difference (°C) of Water Between 0 and 1,000 m

Distance from Resource to Shore (km)

Africa

Benin

22-24

25

Gabon

20-22

15

Ghana

22-24

25

Kenya

20-21

25

Mozambique

18-21

25

São Tomé and Príncipe

22

1-10

Somalia

18-20

25

Tanzania

20-22

25

Latin America and the Caribbean

Bahamas, The

20-22

15

Barbados

22

1-10

Cuba

22-24

1

Dominica

22

1-10

Dominican Republic

21-24

1

Grenada

27

1-10

Haiti

21-24

1

Jamaica

22

1-10

Saint Lucia

22

1-10

Saint Vincent and the Grenadines

22

1-10

Trinidad and Tobago

22-24

10

U.S. Virgin Islands

21-24

1

Indian and Pacific Oceans

Comoros

20-25

1-10

Cook Islands

21-22

1-10

Fiji

22-23

1-10

Guam

24

1

Kiribati

23-24

1-10

Maldives

22

1-10

Mauritius

20-21

1-10

New Caledonia

20-21

1-10

Pacific Islands Trust Territory

22-24

1

Philippines

22-24

1

Samoa

22-23

1-10

Seychelles

21-22

1

Solomon Islands

23-24

1-10

Vanuatu

22-23

1-10

NOTE: Many less developed countries have access to energy obtained through exploitation of the differences in water temperatures. They must be within 25 kilometers (15.5 miles) of an ocean region where there is a temperature difference of about 20°C (36°F) in the first 1000 meters (3280 feet) below the surface.

Electricity generated by plants fixed in one place can be delivered directly to a utility grid. A submersed cable would be required to transmit electricity from an anchored floating platform to land. Moving ships could manufacture transportable products such as methanol, hydrogen, or ammonia on board.

Markets for OTEC

An economic analysis indicates that, over the next 5 to 10 years, ocean thermal energy conversion (OTEC) plants may be competitive in four markets. The first market is the small island nations in the South Pacific and the island of Molokai in Hawaii. In these islands, the relatively high cost of diesel-generated electricity and desalinated water may make a small [1 megawatt (electric) (MWe)], land-based, open-cycle OTEC plant coupled with a second-stage desalinated water production system cost effective. A second market can be found in American territories such as Guam and American Samoa, where land-based, open-cycle OTEC plants rated at 10 MWe with a second-stage water production system would be cost effective. A third market is Hawaii, where a larger, land-based, closed-cycle OTEC plant could produce electricity with a second-stage desalinated water production system. OTEC should quickly become cost effective in this market, when the cost of diesel fuel doubles, for plants rated at 50 MWe or larger. The fourth market is for floating, closed-cycle plants rated at 40 MWe or larger that house a factory or transmit electricity to shore via a submarine power cable. These plants could be built in Puerto Rico, the Gulf of Mexico, and the Pacific, Atlantic, and Indian Oceans. Military and security uses of large floating plantships with major life-support systems (power, desalinated water, cooling, and aquatic food) should be included in this last category.

Oceans Thermal Gradient Map

OTEC's greatest potential is to supply a significant fraction of the fuel the world needs by using large, grazing plantships to produce hydrogen, ammonia, and methanol. Of the three worldwide markets studied for small OTEC installations—U.S. Gulf Coast and Caribbean regions, Africa and Asia, and the Pacific Islands—the Pacific Islands are expected to be the initial market for open-cycle OTEC plants. This prediction is based on the cost of oil-fired power, the demand for desalinated water, and the social benefits of this clean energy technology. U.S. OTEC technology is focused on U.S. Coastal areas, including the Gulf of Mexico, Florida, and islands such as Hawaii, Puerto Rico, and the Virgin Islands.

 

 


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