Ocean thermal energy conversion (OTEC) uses the temperature difference between cooler deep and warmer shallow or surface seawaters to run a heat engine and produce useful work, usually in the form of electricity. OTEC can operate with a very high capacity factor and so can operate in base load mode.
Among ocean energy sources, OTEC is one of the continuously available renewable energy resources that could contribute to base-load power supply. The resource potential for OTEC is considered to be much larger than for other ocean energy forms [World Energy Council, 2000]. Up to 88,000 TWh/yr of power could be generated from OTEC without affecting the ocean’s thermal structure [Pelc and Fujita, 2002].
Systems may be either closed-cycle or open-cycle. Closed-cycle OTEC uses working fluids that are typically thought of as refrigerants such as ammonia or R-134a. These fluids have low boiling points, and are therefore suitable for powering the system’s generator to generate electricity. The most commonly used heat cycle for OTEC to date is the Rankine cycle, using a low-pressure turbine. Open-cycle engines use vapour from the seawater itself as the working fluid.
OTEC can also supply quantities of cold water as a by-product. This can be used for air conditioning and refrigeration and the nutrient-rich deep ocean water can feed biological technologies. Another by-product is fresh water distilled from the sea.
OTEC theory was first developed in the 1880s and the first bench size demonstration model was constructed in 1926. Currently the world's only operating OTEC plant is in Japan, overseen by Saga University.
Attempts to develop and refine OTEC technology started in the 1880s. In 1881, Jacques Arsene d'Arsonval, a French physicist, proposed tapping the thermal energy of the ocean. D'Arsonval's student, Georges Claude, built the first OTEC plant, in Matanzas, Cuba in 1930. The system generated 22 kW of electricity with a low-pressure turbine. The plant was later destroyed in a storm.
In 1935, Claude constructed a plant aboard a 10,000-ton cargo vessel moored off the coast of Brazil. Weather and waves destroyed it before it could generate net power. (Net power is the amount of power generated after subtracting power needed to run the system).
In 1962, J. Hilbert Anderson and James H. Anderson, Jr. focused on increasing component efficiency. They patented their new "closed cycle" design in 1967. This design improved upon the original closed-cycle Rankine system, and included this in an outline for a plant that would produce power at lower cost than oil or coal. At the time, however, their research garnered little attention since coal and nuclear were considered the future of energy.
Japan is a major contributor to the development of OTEC technology. Beginning in 1970 the Tokyo Electric Power Company successfully built and deployed a 100 kW closed-cycle OTEC plant on the island of Nauru. The plant became operational on 14 October 1981, producing about 120 kW of electricity; 90 kW was used to power the plant and the remaining electricity was used to power a school and other places. This set a world record for power output from an OTEC system where the power was sent to a real (as opposed to an experimental) power grid. 1981 also saw a major development in OTEC technology when Russian engineer, Dr. Alexander Kalina, used a mixture of ammonia and water to produce electricity. This new ammonia-water mixture greatly improved the efficiency of the power cycle. In 1994 Saga University designed and constructed a 4.5 kW plant for the purpose of testing a newly invented Uehara cycle, also named after its inventor Haruo Uehara. This cycle included absorption and extraction processes that allow this system to outperform the Kalina cycle by 1-2%. Currently, the Institute of Ocean Energy, Saga University, is the leader in OTEC power plant research and also focuses on many of the technology's secondary benefits.
The 1970s saw an uptick in OTEC research and development during the post 1973 Arab-Israeli War, which caused oil prices to triple. The U.S. federal government poured $260 million into OTEC research after President Carter signed a law that committed the US to a production goal of 10,000 MW of electricity from OTEC systems by 1999.
In 1974, The U.S. established the Natural Energy Laboratory of Hawaii Authority (NELHA) at Keahole Point on the Kona coast of Hawaii. Hawaii is the best US OTEC location, due to its warm surface water, access to very deep, very cold water, and high electricity costs. The laboratory has become a leading test facility for OTEC technology. In the same year, Lockheed received a grant from the U.S. National Science Foundation to study OTEC. This eventually led to an effort by Lockheed, the US Navy, Makai Ocean Engineering, Dillingham Construction, and other firms to build the world's first and only net-power producing OTEC plant, dubbed "Mini-OTEC" For three months in 1979, a small amount of electricity was generated.
Research related to making open-cycle OTEC a reality began earnestly in 1979 at the Solar Energy Research Institute (SERI) with funding from the US Department of Energy. Evaporators and suitably configured direct-contact condensers were developed and patented by SERI (see ). An original design for a power-producing experiment, then called the 165-kW experiment was described by Kreith and Bharathan (, and  ) as the Max Jakob Memorial Award Lecture. The initial design used two parallel axial turbines, using last stage rotors taken from large steam turbines. Later, a team led by Dr. Bharathan at the National Renewable Energy Laboratory (NREL) developed the initial conceptual design for up-dated 210 kW open-cycle OTEC experiment (). This design integrated all components of the cycle, namely, the evaporator, condenser and the turbine into one single vacuum vessel, with the turbine mounted on top to prevent any potential for water to reach it. The vessel was made of concrete as the first process vacuum vessel of its kind. Attempts to make all components using low-cost plastic material could not be fully achieved, as some conservatism was required for the turbine and the vacuum pumps developed as the first of their kind. Later Dr. Bharathan worked with a team of engineers at the Pacific Institute for High Technology Research (PICHTR) to further pursue this design through preliminary and final stages. It was renamed the Net Power Producing Experiment (NPPE) and was constructed at the Natural Energy Laboratory of Hawaii (NELH) by PICHTR by a team led by Chief Engineer Don Evans and the project was managed by Dr. Luis Vega.
In 2002, India tested a 1 MW floating OTEC pilot plant near Tamil Nadu. The plant was ultimately unsuccessful due to a failure of the deep sea cold water pipe. Its government continues to sponsor research.
In 2006, Makai Ocean Engineering was awarded a contract from the U.S. Office of Naval Research (ONR) to investigate the potential for OTEC to produce nationally significant quantities of hydrogen in at-sea floating plants located in warm, tropical waters. Realizing the need for larger partners to actually commercialize OTEC, Makai approached Lockheed Martin to renew their previous relationship and determine if the time was ready for OTEC. And so in 2007, Lockheed Martin resumed work in OTEC and became a subcontractor to Makai to support their SBIR, which was followed by other subsequent collaborations
In March 2011, Ocean Thermal Energy Corporation signed an Energy Services Agreement (ESA) with the Baha Mar resort, Nassau, Bahamas, for the world's first and largest seawater air conditioning (SWAC) system. In June 2015, the project was put on pause while the resort resolved financial and ownership issues. In August 2016, it was announced that the issues had been resolved and that the resort would open in March 2017. It is expected that the SWAC system's construction will resume at that time.
In July 2011, Makai Ocean Engineering completed the design and construction of an OTEC Heat Exchanger Test Facility at the Natural Energy Laboratory of Hawaii. The purpose of the facility is to arrive at an optimal design for OTEC heat exchangers, increasing performance and useful life while reducing cost (heat exchangers being the #1 cost driver for an OTEC plant). And in March 2013, Makai announced an award to install and operate a 100 kilowatt turbine on the OTEC Heat Exchanger Test Facility, and once again connect OTEC power to the grid.
In July 2016, the Virgin Islands Public Services Commission approved Ocean Thermal Energy Corporation's application to become a Qualified Facility. The Company is thus permitted to begin negotiations with the Virgin Islands Water and Power Authority (WAPA) for a Power Purchase Agreement (PPA) pertaining to an Ocean Thermal Energy Conversion (OTEC) plant on the island of St. Croix. This would be the world's first commercial OTEC plant.
In March 2013, Saga University with various Japanese industries completed the installation of a new OTEC plant. Okinawa Prefecture announced the start of the OTEC operation testing at Kume Island on April 15, 2013. The main aim is to prove the validity of computer models and demonstrate OTEC to the public. The testing and research will be conducted with the support of Saga University until the end of FY 2016. IHI Plant Construction Co. Ltd, Yokogawa Electric Corporation, and Xenesys Inc were entrusted with constructing the 100 kilowatt class plant within the grounds of the Okinawa Prefecture Deep Sea Water Research Center. The location was specifically chosen in order to utilize existing deep seawater and surface seawater intake pipes installed for the research center in 2000. The pipe is used for the intake of deep sea water for research, fishery, and agricultural use. The plant consists of two 50 kW units in double Rankine configuration. The OTEC facility and deep seawater research center are open to free public tours by appointment in English and Japanese. Currently, this is one of only two fully operational OTEC plants in the world. This plant operates continuously when specific tests are not underway.
In 2011, Makai Ocean Engineering completed a heat exchanger test facility at NELHA. Used to test a variety of heat exchange technologies for use in OTEC, Makai has received funding to install a 105 kW turbine. Installation will make this facility the largest operational OTEC facility, though the record for largest power will remain with the Open Cycle plant also developed in Hawaii.
In July 2014, DCNS group partnered with Akuo Energy announced NER 300 funding for their NEMO project. If successful, the 16MW gross 10MW net offshore plant will be the largest OTEC facility to date. DCNS plans to have NEMO operational by 2020.
An ocean thermal energy conversion power plant built by Makai Ocean Engineering went operational in Hawaii in August 2015 . The governor of Hawaii, David Ige, "flipped the switch" to activate the plant. This is the first true closed-cycle ocean Thermal Energy Conversion (OTEC) plant to be connected to a U.S. electrical grid . It is a demo plant capable of generating 105 kilowatts, enough to power about 120 homes.
A heat engine gives greater efficiency when run with a large temperature difference. In the oceans the temperature difference between surface and deep water is greatest in the tropics, although still a modest 20 to 25 °C. It is therefore in the tropics that OTEC offers the greatest possibilities. OTEC has the potential to offer global amounts of energy that are 10 to 100 times greater than other ocean energy options such as wave power. OTEC plants can operate continuously providing a base load supply for an electrical power generation system.
The main technical challenge of OTEC is to generate significant amounts of power efficiently from small temperature differences. It is still considered an emerging technology. Early OTEC systems were 1 to 3 percent thermally efficient, well below the theoretical maximum 6 and 7 percent for this temperature difference. Modern designs allow performance approaching the theoretical maximum Carnot efficiency.
Cold seawater is an integral part of each of the three types of OTEC systems: closed-cycle, open-cycle, and hybrid. To operate, the cold seawater must be brought to the surface. The primary approaches are active pumping and desalination. Desalinating seawater near the sea floor lowers its density, which causes it to rise to the surface.
The alternative to costly pipes to bring condensing cold water to the surface is to pump vaporized low boiling point fluid into the depths to be condensed, thus reducing pumping volumes and reducing technical and environmental problems and lowering costs.
Closed-cycle systems use fluid with a low boiling point, such as ammonia (having a boiling point around -33 °C at atmospheric pressure), to power a turbine to generate electricity. Warm surface seawater is pumped through a heat exchanger to vaporize the fluid. The expanding vapor turns the turbo-generator. Cold water, pumped through a second heat exchanger, condenses the vapor into a liquid, which is then recycled through the system.
In 1979, the Natural Energy Laboratory and several private-sector partners developed the "mini OTEC" experiment, which achieved the first successful at-sea production of net electrical power from closed-cycle OTEC. The mini OTEC vessel was moored 1.5 miles (2.4 km) off the Hawaiian coast and produced enough net electricity to illuminate the ship's light bulbs and run its computers and television.
Open-cycle OTEC uses warm surface water directly to make electricity. The warm seawater is first pumped into a low-pressure container, which causes it to boil. In some schemes, the expanding vapour drives a low-pressure turbine attached to an electrical generator. The vapour, which has left its salt and other contaminants in the low-pressure container, is pure fresh water. It is condensed into a liquid by exposure to cold temperatures from deep-ocean water. This method produces desalinized fresh water, suitable for drinking water, irrigation or aquaculture.
In other schemes, the rising vapour is used in a gas lift technique of lifting water to significant heights. Depending on the embodiment, such vapour lift pump techniques generate power from a hydroelectric turbine either before or after the pump is used.
In 1984, the Solar Energy Research Institute (now known as the National Renewable Energy Laboratory) developed a vertical-spout evaporator to convert warm seawater into low-pressure steam for open-cycle plants. Conversion efficiencies were as high as 97% for seawater-to-steam conversion (overall steam production would only be a few percent of the incoming water). In May 1993, an open-cycle OTEC plant at Keahole Point, Hawaii, produced close to 80 kW of electricity during a net power-producing experiment. This broke the record of 40 kW set by a Japanese system in 1982.
A hybrid cycle combines the features of the closed- and open-cycle systems. In a hybrid, warm seawater enters a vacuum chamber and is flash-evaporated, similar to the open-cycle evaporation process. The steam vaporizes the ammonia working fluid of a closed-cycle loop on the other side of an ammonia vaporizer. The vaporized fluid then drives a turbine to produce electricity. The steam condenses within the heat exchanger and provides desalinated water (see heat pipe).
A popular choice of working fluid is ammonia, which has superior transport properties, easy availability, and low cost. Ammonia, however, is toxic and flammable. Fluorinated carbons such as CFCs and HCFCs are not toxic or flammable, but they contribute to ozone layer depletion. Hydrocarbons too are good candidates, but they are highly flammable; in addition, this would create competition for use of them directly as fuels. The power plant size is dependent upon the vapor pressure of the working fluid. With increasing vapor pressure, the size of the turbine and heat exchangers decreases while the wall thickness of the pipe and heat exchangers increase to endure high pressure especially on the evaporator side.
OTEC has the potential to produce gigawatts of electrical power, and in conjunction with electrolysis, could produce enough hydrogen to completely replace all projected global fossil fuel consumption. Reducing costs remains an unsolved challenge, however. OTEC plants require a long, large diameter intake pipe, which is submerged a kilometer or more into the ocean's depths, to bring cold water to the surface.
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 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 degrees) offshore slopes, and relatively smooth sea floors. These sites minimize the length of the 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 costs.
Land-based or near-shore sites can also support mariculture or chilled water agriculture. Tanks or lagoons built on shore allow workers to monitor and control miniature marine environments. Mariculture products can be delivered to market via standard transport.
One disadvantage of land-based facilities arises from the turbulent wave action in the surf zone. OTEC discharge pipes should be placed in protective trenches to prevent subjecting them 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, requiring additional expense in construction and maintenance.
One way that OTEC systems can avoid some of the problems and expenses of operating in a surf zone is by building them 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.
To avoid the turbulent surf zone as well as to move closer to the cold-water resource, OTEC plants can be mounted to the continental shelf at depths up to 100 meters (330 ft). A shelf-mounted plant could be towed to the site and affixed to the sea bottom. This type of construction is already used for offshore oil rigs. The complexities of operating an OTEC plant in deeper water may make them more expensive than land-based approaches. Problems include the stress of open-ocean conditions and more difficult product delivery. Addressing strong ocean currents and large waves adds engineering and construction expense. Platforms require extensive pilings to maintain a stable base. Power delivery can require long underwater cables to reach land. For these reasons, shelf-mounted plants are less attractive.
Floating OTEC facilities operate off-shore. Although potentially optimal for large systems, floating facilities present several difficulties. The difficulty of mooring plants in very deep water complicates 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 connect 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 operation. Major storms and heavy seas can break the vertically suspended cold-water pipe and interrupt warm water intake as well. To help prevent these problems, pipes can be made of 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 storm damage. As an alternative to a warm-water pipe, surface water can be drawn directly into the platform; however, it is necessary to prevent the intake flow from being damaged or interrupted during violent motions caused by heavy seas.
Connecting a floating plant to power delivery cables requires the plant to remain relatively stationary. Mooring is an acceptable method, but current mooring technology is limited to depths of about 2,000 meters (6,600 ft). Even at shallower depths, the cost of mooring may be prohibitive.
OTEC projects under consideration include a small plant for the U.S. Navy base on the British overseas territory island of Diego Garcia in the Indian Ocean. Ocean Thermal Energy Corporation (formerly OCEES International, Inc.) is working with the U.S. Navy on a design for a proposed 13-MW OTEC plant, to replace the current diesel generators. The OTEC plant would also provide 1.25 million gallons per day of potable water. This project is currently waiting for changes in US military contract policies. OTE has proposed building a 10-MW OTEC plant on Guam.
Ocean Thermal Energy Corporation (OTE) currently has plans to install two 10 MW OTEC plants in the US Virgin Islands and a 5-10 MW OTEC facility in The Bahamas. OTE has also designed the world’s largest Seawater Air Conditioning (SWAC) plant for a resort in The Bahamas, which will use cold deep seawater as a method of air-conditioning. In mid-2015, the 95%-complete project was temporarily put on hold while the resort resolved financial and ownership issues. In August 22, 2016, the government of the Bahamas announced that a new agreement had been signed under which the Baha Mar resort will be completed. On September 27, 2016, Bahamian Prime Minister Perry Christie announced that construction had resumed on Baha Mar, and that the resort was slated to open in March 2017.
OTE expects to have the SWAC plant up and running within two years of Baha Mar's opening.
Lockheed Martin's Alternative Energy Development team has partnered with Makai Ocean Engineering to complete the final design phase of a 10-MW closed cycle OTEC pilot system which planned to become operational in Hawaii in the 2012-2013 time frame. This system was designed to expand to 100-MW commercial systems in the near future. In November, 2010 the U.S. Naval Facilities Engineering Command (NAVFAC) awarded Lockheed Martin a US$4.4 million contract modification to develop critical system components and designs for the plant, adding to the 2009 $8.1 million contract and two Department of Energy grants totaling over $1 million in 2008 and March 2010. A small but operational ocean thermal energy conversion (OTEC) plant was inaugurated in Hawaii in August 2015. The opening of the research and development 100-kilowatt facility marked the first time a closed-cycle OTEC plant was connected to the U.S. grid.
On April 13, 2013 Lockheed contracted with the Reignwood Group to build a 10 megawatt plant off the coast of southern China to provide power for a planned resort on Hainan island. A plant of that size would power several thousand homes. The Reignwood Group acquired Opus Offshore in 2011 which forms its Reignwood Ocean Engineering division which also is engaged in development of deepwater drilling.
Currently the only continuously operating OTEC system is located in Okinawa Prefecture, Japan. The Governmental support, local community support, and advanced research carried out by Saga University were key for the contractors, IHI Plant Construction Co. Ltd, Yokogawa Electric Corporation, and Xenesys Inc, to succeed with this project. Work is being conducted to develop a 1MW facility on Kume Island requiring new pipelines. In July 2014, more than 50 members formed the Global Ocean reSource and Energy Association (GOSEA) an international organization formed to promote the development of the Kumejima Model and work towards the installation of larger deep seawater pipelines and a 1MW OTEC Facility. The companies involved in the current OTEC projects, along with other interested parties have developed plans for offshore OTEC systems as well. - For more details, see "Currently Operating OTEC Plants" above.
On March 5, 2014, Ocean Thermal Energy Corporation (OTEC) and the 30th Legislature of the United States Virgin Islands (USVI) signed a Memorandum of Understanding to move forward with a study to evaluate the feasibility and potential benefits to the USVI of installing on-shore Ocean Thermal Energy Conversion (OTEC) renewable energy power plants and Seawater Air Conditioning (SWAC) facilities. The benefits to be assessed in the USVI study include both the baseload (24/7) clean electricity generated by OTEC, as well as the various related products associated with OTEC and SWAC, including abundant fresh drinking water, energy-saving air conditioning, sustainable aquaculture and mariculture, and agricultural enhancement projects for the Islands of St Thomas and St Croix. The Honorable Shawn-Michael Malone, President of the USVI Senate, commented on his signing of the Memorandum of Understanding (MOU) authorizing OTE's feasibility study. “The most fundamental duty of government is to protect the health and welfare of its citizens," said Senator Malone. "These clean energy technologies have the potential to improve the air quality and environment for our residents, and to provide the foundation for meaningful economic development. Therefore, it is our duty as elected representatives to explore the feasibility and possible benefits of OTEC and SWAC for the people of USVI.”
On July 18, 2016, OTE's application to be a Qualifying Facility was approved by the Virgin Islands Public Services Commission. OTE also received permission to begin negotiating contracts associated with this project.
South Korea's Research Institute of Ships and Ocean Engineering (KRISO) received Approval in Principal from Bureau Veritas for their 1MW offshore OTEC design. No timeline was given for the project which will be located 6 km offshore of the Republic of Kiribati.
Akuo Energy and DCNS were awarded NER300 funding on July 8, 2014 for their NEMO (New Energy for Martinique and Overseas) project which is expected to be a 10.7MW-net offshore facility completed in 2020. The award to help with development totaled 72 million Euro.
On February 16, 2018, Global OTEC Resources announced plans to build a 150 kW plant in the Maldives, designed bespoke for hotels and resorts. “All these resorts draw their power from diesel generators. Moreover, some individual resorts consume 7,000 litres of diesel a day to meet demands which equates to over 6,000 tonnes of CO2 annually” said Director, Dan Grech. The EU awarded a grant and Global OTEC resources launched a crowdfunding campaign for the rest.
OTEC has uses other than power production.
Desalinated water can be produced in open- or hybrid-cycle plants using surface condensers to turn evaporated seawater into potable water. System analysis indicates that a 2-megawatt plant could produce about 4,300 cubic metres (150,000 cu ft) of desalinated water each day. Another system patented by Richard Bailey creates condensate water by regulating deep ocean water flow through surface condensers correlating with fluctuating dew-point temperatures. This condensation system uses no incremental energy and has no moving parts.
On March 22, 2015, Saga University opened a Flash-type desalination demonstration facility on Kumejima. This satellite of their Institute of Ocean Energy uses post-OTEC deep seawater from the Okinawa OTEC Demonstration Facility and raw surface seawater to produce desalinated water. Air is extracted from the closed system with a vacuum pump. When raw sea water is pumped into the flash chamber it boils, allowing pure steam to rise and the salt and remaining seawater to be removed. The steam is returned to liquid in a heat exchanger with cold post-OTEC deep seawater. The desalinated water can be used in hydrogen production or drinking water (if minerals are added).
The 41 °F (5 °C) cold seawater made available by an OTEC system creates an opportunity to provide large amounts of cooling to industries and homes near the plant. The water can be used in chilled-water coils to provide air-conditioning for buildings. It is estimated that a pipe 1 foot (0.30 m) in diameter can deliver 4,700 gallons of water per minute. Water at 43 °F (6 °C) could provide more than enough air-conditioning for a large building. Operating 8,000 hours per year in lieu of electrical conditioning selling for 5-10¢ per kilowatt-hour, it would save $200,000-$400,000 in energy bills annually.
The InterContinental Resort and Thalasso-Spa on the island of Bora Bora uses an SWAC system to air-condition its buildings. The system passes seawater through a heat exchanger where it cools freshwater in a closed loop system. This freshwater is then pumped to buildings and directly cools the air.
In 2010, Copenhagen Energy opened a district cooling plant in Copenhagen, Denmark. The plant delivers cold seawater to commercial and industrial buildings, and has reduced electricity consumption by 80 percent. Ocean Thermal Energy Corporation (OTE) has designed a 9800-ton SDC system for a vacation resort in The Bahamas.
OTEC technology supports chilled-soil agriculture. When cold seawater flows through underground pipes, it chills the surrounding soil. The temperature difference between roots in the cool soil and leaves in the warm air allows plants that evolved in temperate climates to be grown in the subtropics. Dr. John P. Craven, Dr. Jack Davidson and Richard Bailey patented this process and demonstrated it at a research facility at the Natural Energy Laboratory of Hawaii Authority (NELHA). The research facility demonstrated that more than 100 different crops can be grown using this system. Many normally could not survive in Hawaii or at Keahole Point.
Japan has also been researching agricultural uses of Deep Sea Water since 2000 at the Okinawa Deep Sea Water Research Institute on Kume Island. The Kume Island facilities use regular water cooled by Deep Sea Water in a heat exchanger run through pipes in the ground to cool soil. Their techniques have developed an important resource for the island community as they now produce spinach, a winter vegetable, commercially year round. An expansion of the deep seawater agriculture facility was completed by Kumejima Town next to the OTEC Demonstration Facility in 2014. The new facility is for researching the economic practicality of chilled-soil agriculture on a larger scale.
Aquaculture is the best-known byproduct, because it reduces the financial and energy costs of pumping large volumes of water from the deep ocean. Deep ocean water contains high concentrations of essential nutrients that are depleted in surface waters due to biological consumption. This "artificial upwelling" mimics the natural upwellings that are responsible for fertilizing and supporting the world's largest marine ecosystems, and the largest densities of life on the planet.
Cold-water delicacies, such as salmon and lobster, thrive in this nutrient-rich, deep, seawater. Microalgae such as Spirulina, a health food supplement, also can be cultivated. Deep-ocean water can be combined with surface water to deliver water at an optimal temperature.
Non-native species such as salmon, lobster, abalone, trout, oysters, and clams can be raised in pools supplied by OTEC-pumped water. This extends the variety of fresh seafood products available for nearby markets. Such low-cost refrigeration can be used to maintain the quality of harvested fish, which deteriorate quickly in warm tropical regions. In Kona, Hawaii, aquaculture companies working with NELHA generate about $40 million annually, a significant portion of Hawaii’s GDP.
The NELHA plant established in 1993 produced an average of 7,000 gallons of freshwater per day. KOYO USA was established in 2002 to capitalize on this new economic opportunity. KOYO bottles the water produced by the NELHA plant in Hawaii. With the capacity to produce one million bottles of water every day, KOYO is now Hawaii’s biggest exporter with $140 million in sales.
Hydrogen can be produced via electrolysis using OTEC electricity. Generated steam with electrolyte compounds added to improve efficiency is a relatively pure medium for hydrogen production. OTEC can be scaled to generate large quantities of hydrogen. The main challenge is cost relative to other energy sources and fuels.
The ocean contains 57 trace elements in salts and other forms and dissolved in solution. In the past, most economic analyses concluded that mining the ocean for trace elements would be unprofitable, in part because of the energy required to pump the water. Mining generally targets minerals that occur in high concentrations, and can be extracted easily, such as magnesium. With OTEC plants supplying water, the only cost is for extraction. The Japanese investigated the possibility of extracting uranium and found developments in other technologies (especially materials sciences) were improving the prospects.
Because OTEC facilities are more-or-less stationary surface platforms, their exact location and legal status may be affected by the United Nations Convention on the Law of the Sea treaty (UNCLOS). This treaty grants coastal nations 12- and 200-nautical-mile (370 km) zones of varying legal authority from land, creating potential conflicts and regulatory barriers. OTEC plants and similar structures would be considered artificial islands under the treaty, giving them no independent legal status. OTEC plants could be perceived as either a threat or potential partner to fisheries or to seabed mining operations controlled by the International Seabed Authority.
For OTEC to be viable as a power source, the technology must have tax and subsidy treatment similar to competing energy sources. Because OTEC systems have not yet been widely deployed, cost estimates are uncertain. One study estimates power generation costs as low as US $0.07 per kilowatt-hour, compared with $0.05 - $0.07 for subsidized wind systems.
Beneficial factors that should be taken into account include OTEC's lack of waste products and fuel consumption, the area in which it is available, (often within 20° of the equator) the geopolitical effects of petroleum dependence, compatibility with alternate forms of ocean power such as wave energy, tidal energy and methane hydrates, and supplemental uses for the seawater.
A rigorous treatment of OTEC reveals that a 20 °C temperature difference will provide as much energy as a hydroelectric plant with 34 m head for the same volume of water flow. The low temperature difference means that water volumes must be very large to extract useful amounts of heat. A 100MW power plant would be expected to pump on the order of 12 million gallons (44,400 tonnes) per minute. For comparison, pumps must move a mass of water greater than the weight of the battleship Bismarck, which weighed 41,700 tonnes, every minute. This makes pumping a substantial parasitic drain on energy production in OTEC systems, with one Lockheed design consuming 19.55 MW in pumping costs for every 49.8 MW net electricity generated. For OTEC schemes using heat exchangers, to handle this volume of water the exchangers need to be enormous compared to those used in conventional thermal power generation plants, making them one of the most critical components due to their impact on overall efficiency. A 100 MW OTEC power plant would require 200 exchangers each larger than a 20-foot shipping container making them the single most expensive component.
The total insolation received by the oceans (covering 70% of the earth's surface, with clearness index of 0.5 and average energy retention of 15%) is: 5.45×1018 MJ/yr × 0.7 × 0.5 × 0.15 = 2.87×1017 MJ/yr
We can use Beer–Lambert–Bouguer's law to quantify the solar energy absorption by water,
where, y is the depth of water, I is intensity and μ is the absorption coefficient. Solving the above differential equation,
The absorption coefficient μ may range from 0.05 m−1 for very clear fresh water to 0.5 m−1 for very salty water.
Since the intensity falls exponentially with depth y, heat absorption is concentrated at the top layers. Typically in the tropics, surface temperature values are in excess of 25 °C (77 °F), while at 1 kilometer (0.62 mi), the temperature is about 5–10 °C (41–50 °F). The warmer (and hence lighter) waters at the surface means there are no thermal convection currents. Due to the small temperature gradients, heat transfer by conduction is too low to equalize the temperatures. The ocean is thus both a practically infinite heat source and a practically infinite heat sink.
In this scheme, warm surface water at around 27 °C (81 °F) enters an evaporator at pressure slightly below the saturation pressures causing it to vaporize.
Where Hf is enthalpy of liquid water at the inlet temperature, T1.
This temporarily superheated water undergoes volume boiling as opposed to pool boiling in conventional boilers where the heating surface is in contact. Thus the water partially flashes to steam with two-phase equilibrium prevailing. Suppose that the pressure inside the evaporator is maintained at the saturation pressure, T2.
Here, x2 is the fraction of water by mass that vaporizes. The warm water mass flow rate per unit turbine mass flow rate is 1/x2.
The low pressure in the evaporator is maintained by a vacuum pump that also removes the dissolved non-condensable gases from the evaporator. The evaporator now contains a mixture of water and steam of very low vapor quality (steam content). The steam is separated from the water as saturated vapor. The remaining water is saturated and is discharged to the ocean in the open cycle. The steam is a low pressure/high specific volume working fluid. It expands in a special low pressure turbine.
The above equation corresponds to the temperature at the exhaust of the turbine, T5. x5,s is the mass fraction of vapor at state 5.
The enthalpy at T5 is,
This enthalpy is lower. The adiabatic reversible turbine work = H3-H5,s .
Actual turbine work WT = (H3-H5,s) x polytropic efficiency
The condenser temperature and pressure are lower. Since the turbine exhaust is to be discharged back into the ocean, a direct contact condenser is used to mix the exhaust with cold water, which results in a near-saturated water. That water is now discharged back to the ocean.
H6=Hf, at T5. T7 is the temperature of the exhaust mixed with cold sea water, as the vapour content now is negligible,
The temperature differences between stages include that between warm surface water and working steam, that between exhaust steam and cooling water, and that between cooling water reaching the condenser and deep water. These represent external irreversibilities that reduce the overall temperature difference.
The cold water flow rate per unit turbine mass flow rate,
Turbine mass flow rate,
Warm water mass flow rate,
Cold water mass flow rate
a Developed starting in the 1960s by J. Hilbert Anderson of Sea Solar Power, Inc. In this cycle, QH is the heat transferred in the evaporator from the warm sea water to the working fluid. The working fluid exits the evaporator as a gas near its dew point.
The high-pressure, high-temperature gas then is expanded in the turbine to yield turbine work, WT. The working fluid is slightly superheated at the turbine exit and the turbine typically has an efficiency of 90% based on reversible, adiabatic expansion.
From the turbine exit, the working fluid enters the condenser where it rejects heat, -QC, to the cold sea water. The condensate is then compressed to the highest pressure in the cycle, requiring condensate pump work, WC. Thus, the Anderson closed cycle is a Rankine-type cycle similar to the conventional power plant steam cycle except that in the Anderson cycle the working fluid is never superheated more than a few degrees Fahrenheit. Owing to viscous effects, working fluid pressure drops in both the evaporator and the condenser. This pressure drop, which depends on the types of heat exchangers used, must be considered in final design calculations but is ignored here to simplify the analysis. Thus, the parasitic condensate pump work, WC, computed here will be lower than if the heat exchanger pressure drop was included. The major additional parasitic energy requirements in the OTEC plant are the cold water pump work, WCT, and the warm water pump work, WHT. Denoting all other parasitic energy requirements by WA, the net work from the OTEC plant, WNP is
The thermodynamic cycle undergone by the working fluid can be analyzed without detailed consideration of the parasitic energy requirements. From the first law of thermodynamics, the energy balance for the working fluid as the system is
where WN = WT + WC is the net work for the thermodynamic cycle. For the idealized case in which there is no working fluid pressure drop in the heat exchangers,
so that the net thermodynamic cycle work becomes
Subcooled liquid enters the evaporator. Due to the heat exchange with warm sea water, evaporation takes place and usually superheated vapor leaves the evaporator. This vapor drives the turbine and the 2-phase mixture enters the condenser. Usually, the subcooled liquid leaves the condenser and finally, this liquid is pumped to the evaporator completing a cycle.
Carbon dioxide dissolved in deep cold and high pressure layers is brought up to the surface and released as the water warms.
Mixing of deep ocean water with shallower water brings up nutrients and makes them available to shallow water life. This may be an advantage for aquaculture of commercially important species, but may also unbalance the ecological system around the power plant.
OTEC plants use very large flows of warm surface seawater and cold deep seawater to generate constant renewable power. The deep seawater is oxygen deficient and generally 20-40 times more nutrient rich (in nitrate and nitrite) than shallow seawater. When these plumes are mixed, they are slightly denser than the ambient seawater. Though no large scale physical environmental testing of OTEC has been done, computer models have been developed to simulate the effect of OTEC plants.
In 2010, a computer model was developed to simulate the physical oceanographic effects of one or several 100 megawatt OTEC plant(s). The model suggests that OTEC plants can be configured such that the plant can conduct continuous operations, with resulting temperature and nutrient variations that are within naturally occurring levels. Studies to date suggest that by discharging the OTEC flows downwards at a depth below 70 meters, the dilution is adequate and nutrient enrichment is small enough so that 100-megawatt OTEC plants could be operated in a sustainable manner on a continuous basis.
The nutrients from an OTEC discharge could potentially cause increased biological activity if they accumulate in large quantities in the photic zone. In 2011 a biological component was added to the hydrodynamic computer model to simulate the biological response to plumes from 100 megawatt OTEC plants. In all cases modeled (discharge at 70 meters depth or more), no unnatural variations occurs in the upper 40 meters of the ocean's surface. The picoplankton response in the 110 - 70 meter depth layer is approximately a 10-25% increase, which is well within naturally occurring variability. The nanoplankton response is negligible. The enhanced productivity of diatoms (microplankton) is small. The subtle phytoplankton increase of the baseline OTEC plant suggests that higher-order biochemical effects will be very small.
A previous Final Environmental Impact Statement (EIS) for the United States' NOAA from 1981 is available, but needs to be brought up to current oceanographic and engineering standards. Studies have been done to propose the best environmental baseline monitoring practices, focusing on a set of ten chemical oceanographic parameters relevant to OTEC. Most recently, NOAA held an OTEC Workshop in 2010 and 2012 seeking to assess the physical, chemical, and biological impacts and risks, and identify information gaps or needs.
The performance of direct contact heat exchangers operating at typical OTEC boundary conditions is important to the Claude cycle. Many early Claude cycle designs used a surface condenser since their performance was well understood. However, direct contact condensers offer significant disadvantages. As cold water rises in the intake pipe, the pressure decreases to the point where gas begins to evolve. If a significant amount of gas comes out of solution, placing a gas trap before the direct contact heat exchangers may be justified. Experiments simulating conditions in the warm water intake pipe indicated about 30% of the dissolved gas evolves in the top 8.5 meters (28 ft) of the tube. The trade-off between pre-dearation of the seawater and expulsion of non-condensable gases from the condenser is dependent on the gas evolution dynamics, deaerator efficiency, head loss, vent compressor efficiency and parasitic power. Experimental results indicate vertical spout condensers perform some 30% better than falling jet types.
Because raw seawater must pass through the heat exchanger, care must be taken to maintain good thermal conductivity. Biofouling layers as thin as 25 to 50 micrometres (0.00098 to 0.00197 in) can degrade heat exchanger performance by as much as 50%. A\1977 study in which mock heat exchangers were exposed to seawater for ten weeks concluded that although the level of microbial fouling was low, the thermal conductivity of the system was significantly impaired. The apparent discrepancy between the level of fouling and the heat transfer impairment is the result of a thin layer of water trapped by the microbial growth on the surface of the heat exchanger.
Another study concluded that fouling degrades performance over time, and determined that although regular brushing was able to remove most of the microbial layer, over time a tougher layer formed that could not be removed through simple brushing. The study passed sponge rubber balls through the system. It concluded that although the ball treatment decreased the fouling rate it was not enough to completely halt growth and brushing was occasionally necessary to restore capacity. The microbes regrew more quickly later in the experiment (i.e. brushing became necessary more often) replicating the results of a previous study. The increased growth rate after subsequent cleanings appears to result from selection pressure on the microbial colony.
Continuous use of 1 hour per day and intermittent periods of free fouling and then chlorination periods (again 1 hour per day) were studied. Chlorination slowed but did not stop microbial growth; however chlorination levels of .1 mg per liter for 1 hour per day may prove effective for long term operation of a plant. The study concluded that although microbial fouling was an issue for the warm surface water heat exchanger, the cold water heat exchanger suffered little or no biofouling and only minimal inorganic fouling.
Besides water temperature, microbial fouling also depends on nutrient levels, with growth occurring faster in nutrient rich water. The fouling rate also depends on the material used to construct the heat exchanger. Aluminium tubing slows the growth of microbial life, although the oxide layer which forms on the inside of the pipes complicates cleaning and leads to larger efficiency losses. In contrast, titanium tubing allows biofouling to occur faster but cleaning is more effective than with aluminium.
The evaporator, turbine, and condenser operate in partial vacuum ranging from 3% to 1% of atmospheric pressure. The system must be carefully sealed to prevent in-leakage of atmospheric air that can degrade or shut down operation. In closed-cycle OTEC, the specific volume of low-pressure steam is very large compared to that of the pressurized working fluid. Components must have large flow areas to ensure steam velocities do not attain excessively high values.
An approach for reducing the exhaust compressor parasitic power loss is as follows. After most of the steam has been condensed by spout condensers, the non-condensible gas steam mixture is passed through a counter current region which increases the gas-steam reaction by a factor of five. The result is an 80% reduction in the exhaust pumping power requirements.
In winter in coastal Arctic locations, the delta T between the seawater and ambient air can be as high as 40 °C (72 °F). Closed-cycle systems could exploit the air-water temperature difference. Eliminating seawater extraction pipes might make a system based on this concept less expensive than OTEC. This technology is due to H. Barjot, who suggested butane as cryogen, because of its boiling point of −0.5 °C (31.1 °F) and its non-solubility in water. Assuming a level of efficiency of realistic 4%, calculations show that the amount of energy generated with one cubic meter water at a temperature of 2 °C (36 °F) in a place with an air temperature of −22 °C (−8 °F) equals the amount of energy generated by letting this cubic meter water run through a hydroelectric plant of 4000 feet (1,200 m) height.
Barjot Polar Power Plants could be located on islands in the polar region or designed as swimming barges or platforms attached to the ice cap. The weather station Myggbuka at Greenlands east coast for example, which is only 2,100 km away from Glasgow, detects monthly mean temperatures below −15 °C (5 °F) during 6 winter months in the year.
Cellana, Inc. is a Hawaii- and San Diego-based developer of algae-based bioproducts for high-value nutrition, ink, and bioenergy applications, including Omega-3 nutraceutical applications, sustainable ink, aquaculture and animal feeds, human food ingredients, pigments, specialty chemicals, and biofuels. Cellana has received (or has been a member of consortia that have received) multiple multimillion-dollar grants from the United States Department of Energy and United States Department of Agriculture. In 2018, Cellana and POS Bio-Sciences announced the signing of a letter of intent for the joint development and commercialization of high-value EPA Omega-3 oils from Cellana’s algae biomass. In December 2016, the United States Department of Energy published a funding opportunity announcement in which Cellana's lead commercial algae strains KA32 and CO46, and the biomass yields demonstrated from these strains as part of the DOE-funded Algae Testbed Public-Private Partnership (ATP3), were designated as DOE's "State of Technology" for the photosynthetic algae sector in the United States. In 2017, Cellana and Living Ink Technologies announced the signing of a letter of intent for the joint development and commercialization of inks containing Cellana’s renewable algae biomass. In 2013, Cellana and Neste Oil, the world's largest refiner of renewable diesel, announced the signing of a multi-year, commercial-scale off-take agreement for algae-based biocrude oil.Cellana, Inc. was founded in 2004 as HR BioPetroleum, Inc. and changed its name to Cellana, Inc. in May 2011. On January 31, 2011, Cellana LLC, a joint venture company formed by Royal Dutch Shell and HR BioPetroleum in 2007, became a wholly owned subsidiary of HR BioPetroleum, Inc./Cellana, Inc. Shell had previously announced on December 11, 2007 that it entered into a joint venture with HR BioPetroleum to, among other things, build and operate a demonstration facility in Hawaii for growing algae as a source of biofuels. This 2.5-hectare facility, known as the Kona Demonstration Facility (KDF), was completed and commissioned in 2009.
The original goal of the facility was to cultivate algae in photobioreactors and open raceway ponds filled with seawater using a proprietary process, then harvest the algae and extract oil for conversion into fuels such as biodiesel and utilize the residual high protein algae meal for additional co-products.
KDF is located on a 2.5-hectare (6-acre) parcel of land leased from the Natural Energy Laboratory of Hawaii Authority (NELHA), which is located on the west shore of the island of Hawaii. NELHA pipes in a constant supply of fresh ocean water. NELHA was originally built to support a DOE project for ocean thermal energy conversion, and it continues to employ the project's seawater supply pipes to support a variety of research projects and commercial enterprises, including facilities that currently grow and harvest microalgae for pharmaceuticals and nutritional supplements.
Cellana's facility grows only non-genetically modified, marine microalgae species using proprietary technology.Deep ocean water
Deep ocean water (DOW) is the name for cold, salty water found deep below the surface of Earth's oceans. Ocean water differs in temperature and salinity. Warm surface water is generally saltier than the cooler deep or polar waters; in polar regions, the upper layers of ocean water are cold and fresh. Deep ocean water makes up about 90% of the volume of the oceans. Deep ocean water has a very uniform temperature, around 0-3 °C, and a salinity of about 3.5% or as oceanographers state as 35 ppt (parts per thousand).In specialized locations such as the Natural Energy Laboratory of Hawaii NELHA ocean water is pumped to the surface from approximately 900 metres (3000 feet) deep for applications in research, commercial and pre-commercial activities. DOW is typically used to describe ocean water at sub-thermal depths sufficient to provide a measurable difference in water temperature.
When deep ocean water is brought to the surface, it can be used for a variety of things. Its most useful property is its temperature. At the surface of the Earth, most water and air is well above 3 °C. The difference in temperature is indicative of a difference in energy. Where there is an energy gradient, skillful application of engineering can harness that energy for productive use by humans. Assuming the source of deep ocean water is environmentally friendly and replenished by natural mechanisms, it forms a more innovative basis for cleaner energy than current fossil-fuel-derived energy.
The simplest use of cold water is for air conditioning: using the cold water itself to cool air saves the energy that would be used by the compressors for traditional refrigeration. Another use could be to replace expensive desalination plants. When cold water passes through a pipe surrounded by humid air, condensation results. The condensate is pure water, suitable for humans to drink or for crop irrigation. Via a technology called Ocean thermal energy conversion, the temperature difference can be turned into electricity.Dispatchable generation
Dispatchable generation refers to sources of electricity that can be used on demand and dispatched at the request of power grid operators, according to market needs. Dispatchable generators can be turned on or off, or can adjust their power output according to an order.
This is in contrast with non-dispatchable renewable energy sources such as wind power and solar PV power which cannot be controlled by operators.
The only types of renewable energy that are dispatchable without separate energy storage are hydroelectric, biomass, geothermal and ocean thermal energy conversion.Dispatchable plants have different speed at which they can be dispatched.
The fastest plants to dispatch are hydroelectric power plants and natural gas power plants.
For example, the 1,728 MW Dinorwig pumped storage power plant can reach full output in 16 seconds.
Although theoretically dispatchable, certain thermal plants such as nuclear or coal are designed to run as base load power plants and may take hours or sometimes days to cycle off and then back on again.The attractiveness of utility-scale energy storage is that it can compensate for the indeterminacy of wind power and solar PV power.
During 2017, solar thermal storage power has become cheaper and a bulk dispatchable source.
Earlier, affordable large-scale storage technologies other than hydro were not available.
The main reasons why dispatchable power plants are needed are:
to provide spinning reserves (frequency control),
to balance the electric power system (load following),
to optimize the economic generation dispatch (merit order), and
to contribute to clear grid congestion (redispatch).Use cases for dispatchable generators comprise:
Load matching - slow changes in power demand between, for example, night and day, require changes in supply too, as the system needs to be balanced at all times (see also Electricity).
Peak matching - short periods of time during which demand exceeds the output of load matching plants; generation capable of satisfying these peaks in demand is implemented through quick deployment of output by flexible sources.
Lead-in times - periods during which an alternative source is employed to supplement the lead time required by large coal or natural gas fueled plants to reach full output; these alternative power sources can be deployed in a matter of seconds or minutes to adapt to rapid shocks in demand or supply that cannot be satisfied by peak matching generators.
Frequency regulation or intermittent power sources - changes in the electricity output sent into the system may change quality and stability of the transmission system itself because of a change in the frequency of electricity transmitted; renewable sources such as wind and solar are intermittent and need flexible power sources to smooth out their changes in energy production.
Backup for base-load generators - Nuclear power plants, for example, are equipped with nuclear reactor safety systems that can stop the generation of electricity in less than a second in case of emergency.Energy Security Act
The Energy Security Act was signed into law by U.S. President Jimmy Carter on June 30, 1980.It consisted of six major acts:
U.S. Synthetic Fuels Corporation Act
Biomass Energy and Alcohol Fuels Act
Renewable Energy Resources Act
Solar Energy and Energy Conservation Act
Solar Energy and Energy Conservation Bank Act
Geothermal Energy Act
Ocean Thermal Energy Conversion ActGas lift
Gas lift or bubble pumps use the artificial lift technique of raising a fluid such as water or oil by introducing bubbles of compressed air, water vapor or other vaporous bubbles into the outlet tube. This has the effect of reducing the hydrostatic pressure in the outlet tube vs. the hydrostatic pressure at the inlet side of the tube.
Devices using this type of lift mechanism:
Coffee percolators use vaporized water to lift hot water
Airlift pumps uses compressed air to lift water
Pulser pumps use a subterranean chamber of air for an airlift pump
Suction dredges use an airlift pump to vacuum mud, sand and debris
Mist lift pumps uses vaporized water to lift seawater in Ocean thermal energy conversionGeorges Claude
Georges Claude (24 September 1870 – 23 May 1960) was a French engineer and inventor. He is noted for his early work on the industrial liquefaction of air, for the invention and commercialization of neon lighting, and for a large experiment on generating energy by pumping cold seawater up from the depths. He has been considered by some to be "the Edison of France". Claude was an active collaborator with the German occupiers of France during the Second World War, for which he was imprisoned in 1945 and stripped of his honors.List of energy resources
These are modes of energy production, energy storage, or energy conservation, listed alphabetically. Note that not all sources are accepted as legitimate or have been proven to be tappable.
Bubble fusion – a nuclear fusion reaction hypothesized to occur during sonoluminescence, an extreme form of acoustic cavitation.
Compound turbine – two axle, steam
Compressed air energy storage
Concentrated solar power
Deep lake water cooling
External combustion engine
Fossil-fuel power station
Fuel – a substance used as a source of energy, usually by the heat produced in combustion.
Geothermal exchange heat pump
Grid energy storage
High-altitude wind power - Energy can be captured from the wind by kites, aerostats, airfoil matrices, balloons, bladed turbines, kytoon, tethered gliders sailplanes
Hydrogen storage, Underground hydrogen storage
Hydropower-Energy from moving water
Liquid nitrogen engine
Marine current power
Magnetohydrodynamic,generator, MHD generator or dynamo transforms thermal energy or kinetic energy directly into electricity
Natural gas field
Natural gas vehicle
Nuclear energy – energy in the nucleus or core of atoms
Osmotic power- or salinity gradient power- is the energy available from the difference in the salt concentration between seawater and river water
OTEC – Ocean thermal energy conversion
Pneumatics – compressed air
Products based on refined oil
Savonius wind turbine – wind
Solar box cooker
Solar power satellite
Solar thermal energy
Solar updraft tower – large version of the solar chimney concept
Solar water heating
Sonoluminescence – the emission of short bursts of light from imploding bubbles in a liquid when excited by sound.
SSTAR – small, sealed, transportable, autonomous reactor
Straight vegetable oil
Stranded gas reserve
Thermal power station
Turgo turbine – impulse water turbine designed for medium head applications
Tyson turbine – for river flow harnessing
Vibration energy scavenging
Quark Matter energy
Zero-point energyLow-temperature thermal desalination
Low-temperature thermal desalination (LTTD) is a desalination technique which takes advantage of the fact that water evaporates at lower temperatures at low pressures, even as low as ambient temperature. The system uses vacuum pumps to create a low pressure, low-temperature environment in which water evaporates even at a temperature gradient of 8°C between two volumes of water. Cooling water is supplied from deep sea depths of as much as 600 metres (2,000 ft). This cold water is pumped through coils to condense the evaporated water vapor. The resulting condensate is purified water.
The LTTD process may also take advantage of the temperature gradient available at power plants, where large quantities of warm cooling water are discharged from the plant, reducing the energy input needed to create a temperature gradient.The principle of LTTD has been known for some time, originally stemming from ocean thermal energy conversion research. Some experiments were conducted in the U.S. and Japan to test low-temperature-driven desalination technology. In Japan, a spray ﬂash evaporation system was developed by Saga University. In the U.S. Hawaiian Islands, the National Energy Laboratory tested an open-cycle OTEC plant with fresh water and power production using a temperature of 20°C between surface water and water at a depth of around 500 m.
LTTD was studied by India's National Institute of Ocean Technology (NIOT) from 2004. Their first LTTD plant was opened in 2005 at Kavaratti in the Lakshadweep islands. The plant's capacity is 100,000 litres (22,000 imp gal; 26,000 US gal)/day, at a capital cost of INR 50 million (€922,000). The plant uses deep sea water at a temperature of 7 to 15 °C (45 to 59 °F). In 2007, NIOT opened an experimental floating LTTD plant off the coast of Chennai with a capacity of 1,000,000 litres (220,000 imp gal; 260,000 US gal)/day. A smaller plant was established in 2009 at the North Chennai Thermal Power Station to prove the LTTD application where power plant cooling water is available.MV Holoholo
M/V Holoholo was a charter research vessel for the Research Corporation of the University of Hawaii (RCUH) for the Ocean thermal energy conversion (OTEC) project. On 10 December 1978 Holoholo went missing at sea, presumed capsized and sank with all hands.Minto wheel
The Minto wheel is a heat engine named after Wally Minto. The engine consists of a set of sealed chambers arranged in a circle, with each chamber connected to the chamber opposite it. One chamber in each connected pair is filled with a liquid with a low boiling point (propane (TB = −42 °C) and R-12 (TB = −29.8 °C) are listed in the Mother Earth News articles). Ideally, the working fluid also has a high vapor pressure and density.Mist lift
The Mist lift, Mist flow or Steam lift pump is a gas lift technique of lifting water used in a form of Ocean Thermal Energy Conversion (OTEC) where water falls to operate a hydro-electric turbine. The water is pumped from the level it drops to using rising steam which is combined into a multiphase flow. Independent of energy production, the technique can be used simply as a thermally powered pump used to raise ocean water from depths for unspecified uses.Natural Energy Laboratory of Hawaii Authority
The Natural Energy Laboratory of Hawaii Authority (NELHA) administers the Hawaii Ocean Science and Technology Park (HOST Park). NELHA was founded in 1974. At 870 acres (350 ha), HOST Park is perhaps the largest single green economic development project in the world solely devoted to growing a green economy. NELHA also administers a small site, 4 acres (1.6 ha), in Puna on the eastern side of the Island of Hawaii for geothermal research.
The original mission was for research into the uses of Deep Ocean Water in Ocean thermal energy conversion (OTEC) renewable energy production and in aquaculture. It later added research into sustainable uses of natural energy sources such as solar energy.
Its administration offices are located in the HOST Park Keahole Point in the North Kona District.
The entrance is on the Hawaii Belt Road at coordinates 19°42′58″N 156°02′01″W, just south of the Kona International Airport. The main administration office is in the 4 acre research campus at the end of the road along the coastline on Keahole Point.
The laboratory was founded in 1974 with 345 acres (140 ha), associated with the University of Hawaii. Large pipelines pump cold sea water from a depth of 3,000 feet (910 m). For three months in 1979, a small amount of electricity was generated. A larger plant was constructed in the Almost $250M was spent on Ocean thermal energy conversion, but by 1991, the research shifted to other areas. The adjacent Science and Technology Park was merged into the facility, expanding it to 877 acres (355 ha). A neutrino detector was partially constructed in the 1990s called Project DUMAND.After four decades, NELHA is well on track to fulfilling its mission as an engine for economic development in Hawaii and the economic impact generated by HOST Park is approaching $150M annually with the creation of over 600 jobs statewide. In 2002, 50 acres (20 ha) were leased to a commercial company which filters and bottles the water for sale in Japan.
Makai Ocean Engineering, working with Lockheed Martin, restarted OTEC research. Aquaculture, biofuel from algae, solar thermal energy, solar concentrating and wind power are some of the 40 tenants.OTE (disambiguation)
OTE is the national telecommunications provider of Greece.
OTE may also refer to:
Ocean thermal energy conversion, a renewable energy source
Oda of Haldensleben (978–1023), daughter of the Margrave of the North March, Theoderich
On-target earnings, a feature in some job adverts
Operational Test and Evaluation (OT&E), as in the U.S. Operational Test and Evaluation Directorate
Optical Telescope Element, a sub-section of the planned James Webb Space TelescopePatrick Kenji Takahashi
Patrick Kenji Takahashi (born September 6, 1940 in Honolulu, Hawaii) is an American biochemical engineer and popular science writer. He has published more than a hundred scientific papers and written four books. He is Director Emeritus of the Hawaii Natural Energy Institute at the University of Hawaii.Thermal energy
Thermal energy can refer to several distinct thermodynamic quantities, such as the internal energy of a system; heat or sensible heat, which are defined as types of energy transfer (as is work); or for the characteristic energy of a degree of freedom in a thermal system , where is temperature and is the Boltzmann constant.Title 42 of the United States Code
Title 42 of the United States Code is the United States Code dealing with public health, social welfare, and civil rights.
42 U.S.C. ch. 1—The Public Health Service
42 U.S.C. ch. 1A—The Public Health Service, Supplemental Provisions
42 U.S.C. ch. 2—Sanitation and Quarantine
42 U.S.C. ch. 3—Leprosy
42 U.S.C. ch. 3A—Cancer
42 U.S.C. ch. 4—Viruses, Serums, Toxins, Antitoxins, Etc.
42 U.S.C. ch. 5—Maternity and Infancy Welfare and Hygiene
42 U.S.C. ch. 6—The Children's Bureau
42 U.S.C. ch. 6A—Public Health Service (Public Health Service Act)
42 U.S.C. ch. 7—Social Security
42 U.S.C. ch. 7A—Temporary Unemployment Compensation Program
42 U.S.C. ch. 8—Low-Income Housing
42 U.S.C. ch. 8A—Slum Clearance, Urban Renewal, and Farm Housing
42 U.S.C. ch. 8B—Public Works or Facilities
42 U.S.C. ch. 8C—Open-Space Land
42 U.S.C. ch. 9—Housing of Persons Engaged in National Defense
42 U.S.C. ch. 10—Federal Security Agency
42 U.S.C. ch. 11—Compensation for Disability or Death to Persons Employed at Military, Air, and Naval Bases Outside United States
42 U.S.C. ch. 12—Compensation for Injury, Death, or Detention of Employees of Contractors with United States Outside United States
42 U.S.C. ch. 13—School Lunch Programs
42 U.S.C. ch. 13A—Child Nutrition
42 U.S.C. ch. 14—Development and Control of Atomic Energy
42 U.S.C. ch. 15—Disaster Relief
42 U.S.C. ch. 15A—Reciprocal Fire Protection Agreements
42 U.S.C. ch. 15B—Air Pollution Control
42 U.S.C. ch. 16—National Science Foundation
42 U.S.C. ch. 16A—Grants for Support of Scientific Research
42 U.S.C. ch. 16B—Contracts for Scientific and Technological Research
42 U.S.C. ch. 17—Federal Employment Service
42 U.S.C. ch. 18—Youth Medals
42 U.S.C. ch. 19—Saline and Salt Waters
42 U.S.C. ch. 19A—Water Resources Research Program
42 U.S.C. ch. 19B—Water Resources Planning
42 U.S.C. ch. 20—Elective Franchise
42 U.S.C. ch. 20A—Civil Rights Commission
42 U.S.C. ch. 21—Civil Rights
42 U.S.C. ch. 21A—Privacy Protection
42 U.S.C. ch. 21B—Religious Freedom Restoration
42 U.S.C. ch. 21C—Protection of Religious Exercise in Land Use and by Institutionalized Persons
42 U.S.C. ch. 22—Indian Hospitals and Health Facilities
42 U.S.C. ch. 23—Development and Control of Atomic Energy
42 U.S.C. ch. 24—Disposal of Atomic Energy Communities
42 U.S.C. ch. 25—Federal Flood Insurance
42 U.S.C. ch. 26—National Space Program
42 U.S.C. ch. 26A—National Space Grant College and Fellowship Program
42 U.S.C. ch. 26B—Biomedical Research in Space
42 U.S.C. ch. 27—Loan Service of Captioned Films and Educational Media for Handicapped
42 U.S.C. ch. 28—Area Redevelopment Program
42 U.S.C. ch. 29—Juvenile Delinquency and Youth Offenses Control
42 U.S.C. ch. 30—Manpower Development and Training Program
42 U.S.C. ch. 31—Public Works Acceleration Program
42 U.S.C. ch. 32—Third Party Liability for Hospital and Medical Care
42 U.S.C. ch. 33—Community Mental Health Centers
42 U.S.C. ch. 34—Economic Opportunity Program
42 U.S.C. ch. 35—Programs for Older Americans
42 U.S.C. ch. 35A—Community Service Employment for Older Americans
42 U.S.C. ch. 36—Compensation of Condemnees in Development Programs
42 U.S.C. ch. 37—Community Facilities and Advance Land Acquisition
42 U.S.C. ch. 38—Public Works and Economic Development
42 U.S.C. ch. 39—Solid Waste Disposal
42 U.S.C. ch. 40—Soil Information Assistance for Community Planning and Resource Development
42 U.S.C. ch. 41—Demonstration Cities and Metropolitan Development Program
42 U.S.C. ch. 42—Narcotic Addict Rehabilitation
42 U.S.C. ch. 43—Department of Health and Human Services
42 U.S.C. ch. 44—Department of Housing and Urban Development
42 U.S.C. ch. 45—Fair Housing
42 U.S.C. ch. 46—Justice System Improvement
42 U.S.C. ch. 47—Juvenile Delinquency Prevention and Control
42 U.S.C. ch. 48—Guarantees for Financing New Community Land Development
42 U.S.C. ch. 49—National Housing Partnerships
42 U.S.C. ch. 50—National Flood Insurance
42 U.S.C. ch. 51—Design and Construction of Public Buildings to Accommodate Physically Handicapped
42 U.S.C. ch. 52—Intergovernmental Cooperation
42 U.S.C. ch. 52A—Joint Funding Simplification
42 U.S.C. ch. 53—Advisory Commission on Intergovernmental Relations
42 U.S.C. ch. 54—Cabinet Committee on Opportunities for Spanish-Speaking People
42 U.S.C. ch. 55—National Environmental Policy
42 U.S.C. ch. 56—Environmental Quality Improvement
42 U.S.C. ch. 57—Environmental Pollution Study
42 U.S.C. ch. 58—Disaster Relief
42 U.S.C. ch. 59—National Urban Policy and New Community Development
42 U.S.C. ch. 60—Comprehensive Alcohol Abuse and Alcoholism Prevention, Treatment, and Rehabilitation Program
42 U.S.C. ch. 61—Uniform Relocation Assistance and Real Property Acquisition Policies for Federal and Federally Assisted Programs
42 U.S.C. ch. 62—Intergovernmental Personnel Program
42 U.S.C. ch. 63—Lead-Based Paint Poisoning Prevention
42 U.S.C. ch. 63A—Residential Lead-Based Paint Hazard Reduction
42 U.S.C. ch. 64—Public Service Employment Programs
42 U.S.C. ch. 65—Noise Control
42 U.S.C. ch. 66—Domestic Volunteer Services
42 U.S.C. ch. 67—Child Abuse Prevention and Treatment and Adoption Reform
42 U.S.C. ch. 68—Disaster Relief
42 U.S.C. ch. 69—Community Development
42 U.S.C. ch. 70—Manufactured Home Construction and Safety Standards
42 U.S.C. ch. 71—Solar Energy
42 U.S.C. ch. 72—Juvenile Justice and Delinquency Prevention
42 U.S.C. ch. 73—Development of Energy Sources
42 U.S.C. ch. 74—Nonnuclear Energy Research and Development
42 U.S.C. ch. 75—Programs for Individuals with Developmental Disabilities
42 U.S.C. ch. 76—Age Discrimination in Federally Assisted Programs
42 U.S.C. ch. 77—Energy Conservation
42 U.S.C. ch. 78—National Petroleum Reserve in Alaska
42 U.S.C. ch. 79—Science and Technology Policy, Organization and Priorities
42 U.S.C. ch. 80—Public Works Employment
42 U.S.C. ch. 81—Energy Conservation and Resource Renewal
42 U.S.C. ch. 82—Solid Waste Disposal
42 U.S.C. ch. 83—Energy Extension Service
42 U.S.C. ch. 84—Department of Energy
42 U.S.C. ch. 85—Air Pollution Prevention and Control
42 U.S.C. ch. 86—Earthquake Hazards Reduction
42 U.S.C. ch. 87—Water Research and Development
42 U.S.C. ch. 88—Uranium Mill Tailings Radiation Control Act
42 U.S.C. ch. 89—Congregate Housing Services
42 U.S.C. ch. 90—Neighborhood and City Reinvestment, Self-Help and Revitalization
42 U.S.C. ch. 91—National Energy Conservation Policy
42 U.S.C. ch. 92—Powerplant and Industrial Fuel Use
42 U.S.C. ch. 93—Emergency Energy Conservation
42 U.S.C. ch. 94—Low-Income Energy Assistance
42 U.S.C. ch. 95—United States Synthetic Fuels Corporation
42 U.S.C. ch. 96—Biomass Energy and Alcohol Fuels
42 U.S.C. ch. 97—Acid Precipitation Program and Carbon Dioxide Study
42 U.S.C. ch. 98—Ocean Thermal Energy Conversion Research and Development
42 U.S.C. ch. 99—Ocean Thermal Energy Conversion
42 U.S.C. ch. 100—Wind Energy Systems
42 U.S.C. ch. 101: Magnetic Fusion Energy Engineering
42 U.S.C. ch. 102: Mental Health Systems
42 U.S.C. ch. 103: Comprehensive Environmental Response, Compensation, and Liability
42 U.S.C. ch. 104: Nuclear Safety Research, Development, and Demonstration
42 U.S.C. ch. 105: Community Services Programs
42 U.S.C. ch. 106: Community Services Block Grant Program
42 U.S.C. ch. 107: Consumer-Patient Radiation Health and Safety
42 U.S.C. ch. 108: Nuclear Waste Policy
42 U.S.C. ch. 109: Water Resources Research
42 U.S.C. ch. 109a: Membrane Processes Research
42 U.S.C. ch. 110: Family Violence Prevention and Services
42 U.S.C. ch. 111: Emergency Federal Law Enforcement Assistance
42 U.S.C. ch. 112: Victim Compensation and Assistance
42 U.S.C. ch. 113: State Justice Institute
42 U.S.C. ch. 114: Protection And Advocacy For Mentally Ill Individuals
42 U.S.C. ch. 115: Child Development Associate Scholarship Assistance Program
42 U.S.C. ch. 116: Emergency Planning and Community Right-To-Know
42 U.S.C. ch. 117: Encouraging Good Faith Professional Review Activities
42 U.S.C. ch. 118: Alzheimer's Disease and Related Dementias Research
42 U.S.C. ch. 119: Homeless Assistance
42 U.S.C. ch. 120: Enterprise Zone Development
42 U.S.C. ch. 121: International Child Abduction Remedies
42 U.S.C. ch. 122: Native Hawaiian Health Care
42 U.S.C. ch. 123: Drug Abuse Education and Prevention
42 U.S.C. ch. 124: Public Housing Drug Elimination
42 U.S.C. ch. 125: Renewable Energy and Energy Efficiency Technology Competitiveness
42 U.S.C. ch. 126: Equal Opportunity For Individuals With Disabilities
42 U.S.C. ch. 127: Coordinated Services For Children, Youth, and Families
42 U.S.C. ch. 128: Hydrogen Research, Development, And Demonstration Program
42 U.S.C. ch. 129: National and Community Service
42 U.S.C. ch. 130: National Affordable Housing
42 U.S.C. ch. 131: Housing Opportunities for Persons with AIDS
42 U.S.C. ch. 132: Victims of Child Abuse
42 U.S.C. ch. 133: Pollution Prevention
42 U.S.C. ch. 134: Energy Policy
42 U.S.C. ch. 135: Residency and Service Requirements in Federally Assisted Housing
42 U.S.C. ch. 136: Violent Crime Control and Law Enforcement
42 U.S.C. ch. 137: Management of Rechargeable Batteries and Batteries Containing Mercury
42 U.S.C. ch. 138: Assisted Suicide Funding Restriction
42 U.S.C. ch. 139: Volunteer Protection
42 U.S.C. ch. 140: Criminal Justice Identification, Information, and Communication
42 U.S.C. ch. 140A: Jennifer's Law
42 U.S.C. ch. 141: Commercial Space Opportunities and Transportation Services
42 U.S.C. ch. 142: Poison Control Center Enhancement and Awareness
42 U.S.C. ch. 143: Intercountry Adoptions
42 U.S.C. ch. 144: Developmental Disabilities Assistance and Bill of Rights
42 U.S.C. ch. 145: Public Safety Officer Medal of Valor and Tributes
42 U.S.C. ch. 146: Election Administration Improvement
42 U.S.C. ch. 147: Prison Rape Elimination
42 U.S.C. ch. 148: Windstorm Impact Reduction
42 U.S.C. ch. 149: Energy Policy, 2005
42 U.S.C. ch. 150: National Aeronautics and Space Programs, 2005
42 U.S.C. ch. 151: Child Protection and Safety
42 U.S.C. ch. 152: Energy Independence and SecurityTony deBrum
Tony deBrum (February 26, 1945 – August 22, 2017) was a Marshallese politician and government minister. He helped organize the Marshall Islands' independence from the United States and later served as Foreign Minister of the Marshall Islands from 1979 to 1987, from 2008 to 2009 and from 2014 to 2016. He was the Minister in Assistance to the President of Marshall Islands from 2012 to 2014. He was particularly outspoken on climate change, and participated in numerous conferences and demonstrations, including the People's Climate March in New York City in September 2014.In mid December 2015, he took part in the 2015 United Nations Climate Change Conference. He succeeded in forming a new coalition between developed countries and developing countries called "High Ambition Coalition". The coalition of over 90 countries was credited with galvanising the conference around the goal of holding global temperatures to a 1.5°C increase.DeBrum won the 2015 Right Livelihood Award in recognition of his "vision and courage to take legal action against the nuclear powers for failing to honour their disarmament obligations under the Nuclear Non-Proliferation Treaty and customary international law.".He was an outspoken proponent for ocean thermal energy conversion technology (OTEC) and tried to get the US and Marshallese governments to agree to build a 20 MW floating OTEC power plant by Kwajalein atoll in the Marshall Islands in association with Energy Harvesting Systems of Honolulu, Hawaii. On Kwajalein the local children nicknamed him "Mr. OTEC".Wave base
The wave base, in physical oceanography, is the maximum depth at which a water wave's passage causes significant water motion. For water depths deeper than the wave base, bottom sediments and the seafloor are no longer stirred by the wave motion above.William H. Avery (engineer)
William Hinckley Avery (July 25, 1912 – June 26, 2004) was an influential aeronautical engineer. He designed the propulsion mechanism known as the ramjet, and was known for heading the Ocean Thermal Energy Conversion program which generates electricity from the temperature differential between shallow and deep ocean water.