Deep ocean water
Deep Ocean Water is the name for cold, salty water found deep below the surface of Earth's oceans. Ocean water differs in temperature
Temperature is a physical property of matter that quantitatively expresses the common notions of hot and cold. Objects of low temperature are cold, while various degrees of higher temperatures are referred to as warm or hot...

 and salinity
Salinity is the saltiness or dissolved salt content of a body of water. It is a general term used to describe the levels of different salts such as sodium chloride, magnesium and calcium sulfates, and bicarbonates...

, with warm, relatively non-salty water found at the surface, and very cold salty water found deeper below the surface layer. Deep ocean water makes up about 90% of the volume of the oceans. Deep ocean water has a very low temperature, with a high of 1.6 °C (35 °F), and a salinity of about 3.5%.

In specialized locations such as the Natural Energy Laboratory of Hawaii NELHA
The Natural Energy Laboratory of Hawaii Authority administers the Hawaii Ocean Science and Technology Park . NELHA also administers a small site in Puna on the eastern side of the Island of Hawaii for geothermal research. NELHA was founded in 1974...

 ocean water is pumped to the surface from approximately 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 Delta
Delta (letter)
Delta is the fourth letter of the Greek alphabet. In the system of Greek numerals it has a value of 4. It was derived from the Phoenician letter Dalet...

 in water temperature.

When deep ocean water is brought to the surface, it can be used for a variety of things. The most useful property of it is its temperature. At the surface of the Earth, most water and air is well above 1.6°C. The difference in temperature is indicative of a difference in energy
In physics, energy is an indirectly observed quantity. It is often understood as the ability a physical system has to do work on other physical systems...

. Where there is an energy gradient
In vector calculus, the gradient of a scalar field is a vector field that points in the direction of the greatest rate of increase of the scalar field, and whose magnitude is the greatest rate of change....

, skillful application of science and 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 simply for air conditioning
Air conditioning
An air conditioner is a home appliance, system, or mechanism designed to dehumidify and extract heat from an area. The cooling is done using a simple refrigeration cycle...

: using the cold water itself to cool air saves the energy that would be used by the compressors for traditional refrigeration
Refrigeration is a process in which work is done to move heat from one location to another. This work is traditionally done by mechanical work, but can also be done by magnetism, laser or other means...

. Another use could be to replace expensive desalination
Desalination, desalinization, or desalinisation refers to any of several processes that remove some amount of salt and other minerals from saline water...

 plants. When cold water passes through a pipe surrounded by humid air, condensation results. The condensate is pure water
Water is a chemical substance with the chemical formula H2O. A water molecule contains one oxygen and two hydrogen atoms connected by covalent bonds. Water is a liquid at ambient conditions, but it often co-exists on Earth with its solid state, ice, and gaseous state . Water also exists in a...

, suitable for humans to drink or for crop irrigation
Irrigation may be defined as the science of artificial application of water to the land or soil. It is used to assist in the growing of agricultural crops, maintenance of landscapes, and revegetation of disturbed soils in dry areas and during periods of inadequate rainfall...

. Finally, via a technology called Ocean thermal energy conversion
Ocean thermal energy conversion
Ocean Thermal Energy Conversion uses the difference between cooler deep and warmer shallow or surface ocean waters to run a heat engine and produce useful work, usually in the form of electricity....

, the temperature difference can be turned into electricity.
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