Editing Ocean thermal energy conversion (section)

== Related activities ==

OTEC has uses other than power production.

=== Desalination ===

Desalinated water can be produced in open- or hybrid-cycle plants using [[surface condenser]]s to turn evaporated seawater into potable water. System analysis indicates that a 2-megawatt plant could produce about {{convert|4300|m3}} of desalinated water each day.<ref>Block and Lalenzuela 1985</ref> Another system patented by Richard Bailey creates condensate water by regulating deep ocean water flow through surface condensers correlating with fluctuating dew-point temperatures.<ref>{{patent|US|7726138}}</ref> 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.<ref name="Saga University Report">{{cite web|url=http://www.ioes.saga-u.ac.jp/jp/openlab/openlab-kume-2015-report|title=海洋エネルギー研究センター 2015久米島サテライトオープンラボ (施設見学会)[報告]|access-date=2015-06-16}}</ref> 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.<ref>{{cite web|last1=Martin|first1=Benjamin|title=IOES Kumejima Satellite|url=http://otecokinawa.com/en/Tours/IOES.html|website=otecokinawa.com|access-date=2015-06-16|archive-date=2020-06-07|archive-url=https://web.archive.org/web/20200607115729/http://otecokinawa.com/en/Tours/IOES.html|url-status=dead}}</ref> The desalinated water can be used in hydrogen production or drinking water (if minerals are added).

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.[81]

=== Air conditioning ===
{{Off topic|date=January 2022}}
The {{convert|41|F}} 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 {{convert|1|ft|m}} in diameter can deliver 4,700 gallons of water per minute. Water at {{convert|43|F}} 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.<ref>[[United States Department of Energy|U.S. Department of Energy]], 1989</ref>

The [[InterContinental]] Resort and Thalasso-Spa on the island of [[Bora Bora]] uses an SWAC system to air-condition its buildings.<ref>{{cite web|url=https://www.youtube.com/watch?v=zTGvPrrkVAA| archive-url=https://web.archive.org/web/20111104075802/http://www.youtube.com/watch?v=zTGvPrrkVAA&gl=US&hl=en| archive-date=2011-11-04 | url-status=dead|title=YouTube video on the OTEC air-conditioning system used at the InterContinental Resort and Thalasso-Spa on the island of Bora Bora|website = [[YouTube]]|access-date=2007-05-28}}</ref>  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.<ref>Green Tech. "Copenhagen’s SeawaterCooling Delivers Energy And Carbon Savings". 24 October 2012. Forbes.</ref>  Ocean Thermal Energy Corporation (OTE) has designed a 9800-ton SDC system for a vacation resort in The Bahamas.

=== Chilled-soil agriculture ===

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 climate]]s 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).<ref>{{patent|us|7069689}}</ref> 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.{{Citation needed|date=December 2010}}

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.<ref>{{cite web|url=http://kumeguide.com/Industry/DeepSeaWater/ResearchInstitute/|title=Deep Sea Water Research Institute|website=kumeguide.com|date=16 August 2019}}</ref>

=== Aquaculture ===

[[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 sea animals, such as [[salmon]] and [[lobster]], thrive in this nutrient-rich, deep seawater. [[Microalgae]] such as ''[[Spirulina (dietary supplement)|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]], [[oyster]]s, and [[clam]]s 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.<ref>Ponia, Ben. "Aquaculture Updates in the Northern Pacific: Hawaii, Federated States of Mirconesia, Palau and Saipan". SPCFisheries Newsletter. July 2006. Web. 25 June 2013. available at: http://www.spc.int/DigitalLibrary/Doc/FAME/InfoBull/FishNews/118/FishNews11 {{Webarchive|url=https://web.archive.org/web/20150925150258/http://www.spc.int/DigitalLibrary/Doc/FAME/InfoBull/FishNews/118/FishNews11 |date=2015-09-25 }} 8_58_Ponia.pdf.</ref>

=== Hydrogen production ===

[[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.<ref>{{cite book |last1=Shah |first1=Yatish |title=Water for Energy and Fuel Production |publisher=CRC Press |isbn=978-1482216189|date=2014-05-16 }}</ref>

=== Mineral extraction ===

The ocean contains 57 [[trace element]]s 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.<ref>{{cite book |last1=Wu |first1=Chih |title=Renewable Energy From The Ocean |publisher=Oxford University Press |isbn=9780195071993|year=1994 }}</ref>
The Japanese investigated the possibility of extracting [[uranium]] and found developments in other technologies (especially materials sciences) were improving the prospects.<ref>{{cite web |last1=Berger |first1=Matthew |title=The Nuclear Option: Technology to Extract Uranium From the Sea Advances |url=https://www.newsdeeply.com/oceans/articles/2018/06/28/the-nuclear-option-technology-to-extract-uranium-from-the-sea-advances |website=NewsDeeply|date=28 June 2018 }}</ref>

===Climate control===
{{More citations needed section|date=January 2022}}
[[Ocean thermal gradient]] can be used to enhance rainfall and moderate the high ambient summer temperatures in tropics to benefit enormously the mankind and the [[flora and fauna]].{{Citation needed|date=January 2022}} When [[sea surface temperature]]s are relatively high on an area, lower atmospheric pressure area is formed compared to atmospheric pressure prevailing on the nearby land mass inducing winds from the landmass towards the ocean. Oceanward winds are dry and warm which would not contribute to good rainfall on the landmass compared to landward moist winds. For adequate rainfall and comfortable summer ambient temperatures (below 35&nbsp;°C) on the landmass, it is preferred to have landward moist winds from the ocean. Creating high pressure zones by artificial [[upwelling]] on sea area selectively can also be used to deflect / guide the normal monsoon [[global winds]] towards the landmass. Artificial upwelling of nutrient-rich deep ocean water to the surface also enhances fisheries growth in areas with tropical and temperate weather.<ref>{{cite journal|title=Enhancing fish stocks with artificial upwelling |citeseerx = 10.1.1.526.2024}}</ref> It would also lead to enhanced [[carbon sequestration]] by the oceans from improved [[algae]] growth and [[Glacier mass balance|mass gain by glaciers]] from the extra snow fall mitigating [[sea level rise]] or [[global warming]] process.{{Citation needed|date=January 2022}} [[Tropical cyclones]] also do not pass through the high pressure zones as they intensify by gaining energy from the warm surface waters of the sea.

The cold deep sea water (<10&nbsp;°C) is pumped to the sea surface area to suppress the sea surface temperature (>26&nbsp;°C) by artificial means using electricity produced by mega scale [[floating wind turbine]] plants on the deep sea. The lower sea water surface temperature would enhance the local ambient pressure so that atmospheric landward winds are created. For [[upwelling]] the cold sea water, a stationary hydraulically driven propeller (≈50 m diameter) is located on the [[deep sea]] floor at 500 to 1000 m depth with a flexible [[draft tube]] extending up to the sea surface. The draft tube is [[Suction caisson|anchored to the sea bed]] at its bottom side and top side to floating [[Float (nautical)|pontoons]] at the sea surface. The flexible draft tube would not collapse as its inside pressure is more compared to outside pressure when the colder water is pumped to the sea surface. Middle east, north east Africa, Indian subcontinent and Australia can get relief from hot and dry weather in summer season, also prone to erratic rainfall, by pumping deep sea water to the sea surface from the Persian gulf, Red sea, Indian Ocean and Pacific Ocean respectively.{{Citation needed|date=January 2022}}