Deep ocean water
Deep ocean water(DOW) is the name for cold,saltywaterfound in thedeep sea,starting at 200 m (660 ft) below the surface of Earth'soceans.Ocean water differs intemperatureandsalinity.Warm surface water is generally saltier than the cooler deep orpolarwaters;[1]inpolar regions,theupper layersof ocean water are cold and fresh.[2]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 (32–37 °F), and a salinity of about 3.5% or, asoceanographersstate, 35‰ (parts per thousand).[3]
In specialized locations, such as theNatural Energy Laboratory of Hawaii,ocean water is pumped to the surface from approximately 900 m (3,000 ft) deep for applications in research, commercial and pre-commercial activities. DOW is typically used to describe ocean water atsub-thermal depths[clarify]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 inenergy.Where there is an energygradient,skillful application of engineering can harness that energy for productive use by humans.
The simplest use of cold water is forair conditioning:using the cold water itself to cool air saves the energy that would be used by the compressors for traditionalrefrigeration.Another use could be to replace expensivedesalinationplants. When cold water passes through a pipe surrounded by humid air, condensation results. The condensate is purewater,suitable for humans to drink or for cropirrigation.Via a technology calledocean thermal energy conversion,the temperature difference can be used to run aheat engineto generate electricity.
Cold-bed agriculture[edit]
A potential indirect use of cold ocean water is "cold-bed agriculture". During condensation or ocean thermal energy conversion operations, the water does not reachambient temperature,because a certain temperature gradient is required to make these processes viable. The water leaving those operations is therefore still colder than the surroundings, and a further benefit can be extracted by passing this water through underground pipes, thereby cooling agricultural soil. This reduces evaporation, and even causes water to condense from the atmosphere.[4]This allows agricultural production where crops would normally not be able to grow. This technique is sometimes referred to as "cold agriculture"[5]or "cold-bed agriculture".[6]
See also[edit]
References[edit]
- ^"Ocean Stratification".The Climate System.Columbia University Press.Archived fromthe originalon 29 March 2020.Retrieved2015-09-22.
- ^"The Hidden Meltdown of Greenland".NASA Science News.NASA.Retrieved2023-11-27.
- ^"Temperature of Ocean Water".UCAR.Archived fromthe originalon 2010-03-27.Retrieved2012-09-05.
- ^"Energinat - DOW Technologies - Cold Agriculture".energinat.Archived fromthe originalon 29 January 2016.Retrieved14 July2016.
- ^West Hawaii Tech Pau Hana
- ^"What is OTEC".OTEC News.the OTEC foundation. 30 September 2011.Retrieved14 July2016.
