During the latter part of the last century, the young sciences of Oceanography and Thermodynamics had each separately developed past the initial rush of discovery to attain a certain level of maturity. The science of Oceanography was being built upon the results of measurements made in several voyages of discovery, under a number of flags, towards a broad understanding of the structure and dynamics of the ocean. Thermodynamics, after the development of theoretical underpinnings relating mechanical and thermal energy and work, flowered into practical application in the form of the steam engine and further, the growing Industrial Revolution.

     Jaques-Arsène d'Arsonval, a famous French scientist, noted for his numerous contributions to the physical, physiological, and medical sciences, bridged the two sciences of Thermodynamics and Oceanography with his realization that the ocean and atmosphere acted like a giant steam engine. In the natural solar energy cycle, heat flows horizontally from the sun-warmed tropics to cooler temperate zones. This same heat flow could be tapped vertically in the tropical regions of the ocean via human technological means. This concept could, in effect, be actualized to harness a potentially limitless amount of energy.

     Ocean Thermal Energy Conversion uses the world’s largest renewable energy resource, the ocean. Solar energy stored in the warm tropical ocean is converted to electrical energy using a modified refrigeration technology and cold, deep ocean water. All heat engines collectively share the principle that energy will flow from an area of higher temperature to an area of lower temperature. All modern power plants use temperature differences to produce electricity. Geothermal, coal, nuclear and diesel power plants all employ a high temperature gaseous medium to spin a turbine, which turns a dynamo, which generates electricity. These power plants use a medium with a temperature difference of several hundred degrees. On the other hand, an OTEC energy generation system uses a temperature differential of far less- approximately 20^oC to 24^oC Ocean waters in the equatorial region of the earth have the necessary temperature gradient. Surface water is kept warm all year via the radiation of an ever-present tropical sun. Below the surface, the water remains at Arctic temperatures of approximately 4^oC. The degree of difference in temperature is adequate to power a thermal engine of a relatively low efficiency. Most modern power plants have a resource to electricity conversion efficiency approaching 30 to 40 percent. An OTEC plant operates at a much lower efficiency, but it works with such a large volume of water, 24 hours a day, 365 days a year, that it produces substantially large amounts of energy, negating the apparent disadvantages of operating at a perceived lower efficiency. In reality, the net positive effect is substantial. The fact that the Ocean Energy Resource is extremely large and free makes the importance of technical efficiency less dominant.

     One of d'Arsonval's students, Goerges Claude, took this idea to application, first in 1928, in what is now known as a bottom cycle application. He used warm cooling water from a steel plant in Belgium, and cool Meuse river water from near the plant as the operating medium for an Open-Cycle OTEC plant that produced electricity. It was the first of it's kind to operate at the scale. Modern designs for OTEC plants provide continuous, base-load electric power because ocean water temperatures are stable, unlike other renewable energy sources such as wind and solar which are inherently intermittent in nature. Using the sun for its heat source, the OTEC process is free of any kind of pollution or emissions.

     Claude favored the use of open-cycle OTEC and he developed a system of pre-dearation (taking out dissolved gases from a liquid prior to evaporation.), to remove the non-condensable gases and thus, to improve the efficiency of the whole process. d'Arsonval had suggested the use of a closed cycle system in line with theoretical descriptions of such a cycle by Carnot and later, more realistically, by Rankine. Recently, Exergy, Inc. has developed a new cycle, the Kalina Cycle^®, which considerably improves upon the efficiency of the OTEC concept.

     The OTEC idea lay largely dormant during the period of artificially inexpensive and readily available oil and was resurrected after the OPEC oil crisis in the 1970's. Hawaii became the world center for exploring the potential for development and application of the OTEC concept. In the last 25 years, numerous OTEC relevant research efforts have been conducted in Hawaii. Included in these efforts were MiniOTEC and OTEC-1 that demonstrated power generation, and the development by PICHTR of an operational freshwater producing OPEN-CYCLE OTEC prototype. Other technological advancements included biofouling and corrosion solutions in heat exchanger design; problems that were inherent in previous OTEC designs.

     What has occurred at the research facilities in Hawaii is the realization that not only can electric power be produced using the ocean’s natural thermal gradients, but also abundant, clean, and potable drinking water. In addition, cold, deep seawater is nutrient rich and pathogen free, ideal for aquaculture and mariculture applications such as fish and shellfish farming. The cold seawater causes natural condensation in the soil enhancing growth rates for agriculture. Further, an OTEC power system pumps a large amount of very cold seawater to the surface and therefore can provide air-conditioning which is extremely cost effective. By providing air-conditioning as a separate sub-system within an OTEC facility, electrical load requirements and maintenance costs are drastically reduced. Additionally, through the process of electrolysis, fresh water from the OTEC process can be the basis for a hydrogen production system, of which commercial scale quantities could be constantly produced. This realization has thus led to the development of an OTEC systems approach that can be implemented to produce various optimized amounts of all of these products for a particular installation. The systems approach results in extremely favorable economic conditions for a profitable governmental or commercial entity, energy corporation, division, or consortium.

     An Integrated OTEC System can create harmonious, self-sustaining island communities independent of imported fossil fuels and their associated costs. Pollution and emission free energy with reduced, predictable and stable operational costs largely independent of foreign imposed pricing and politics. Island communities can now create a complete infrastructure providing food, water, and electricity which can reliably support industry, tourism, and trade - effectively bolstering their developing economies.

     The specific market needs for this technology are quite extensive. Commercial OTEC facilities must be located in an environment that is stable enough for efficient system operation. The natural ocean thermal gradient necessary for OTEC operation is generally found between latitudes 20^oN and 20^oS. Within this tropical zone, are portions of several industrial nations (i.e. United States, Taiwan, Japan, etc.), as well as 29 territories and 66 developing nations and nearly a dozen U.S. Department of Defense operated military installations (i.e. Diego Garcia, B.I.O.T.; Guantanamo Bay, Cuba; AUTEC, Bahamas; Kwajalein, etc.). Of all these possible sites, tropical islands with growing power requirements and a dependence on expensive imported oil are the most likely areas for initial OTEC development. Most of these military installations, developing countries and territories have significant needs for reliable, sanitary potable water and/or food sources, afforded through cold water agriculture and/or aquaculture application, adding to the social and political desirability of an integrated OTEC system.