Ocean Thermal Energy Conversion
Ocean thermal energy conversion
For many years, scientists have been aware of one enormous reservoir of energy on the earth's surface: the oceans. As sunlight falls on the oceans, its energy is absorbed by seawater. The oceans are in one sense, therefore, a huge "storage tank" for solar energy . The practical problem is finding a way to extract that energy and make it available for human use.
The mechanism suggested for capturing heat stored in the ocean depends on a thermal gradient always present in seawater. Upper levels of the ocean may be as much as 36°F (20°C) warmer than regions 0.6 mile (1 km) deeper. The technology of ocean thermal energy conversion (OTEC) takes advantage of this temperature gradient.
An OTEC plant would consist of a very large floating platform with pipes at least 100 feet (30 m) in diameter reaching to a depth of up to 0.6 mile (1 km). The "working fluid" in such a plant would be ammonia, propane, or some other liquid with a low boiling point.
Warm surface waters would be pumped into upper levels of the plant, causing the working fluid to evaporate. As the fluid evaporates, it will also exert increased pressure. That pressure can be used to drive a turbine that, in turn, generates electricity. The electricity could be carried to shore along large cables or used directly on the OTEC plant to desalinize water, electrolyze water, or produce other chemical changes.
In the second stage of operation, cold water from deeper levels of the ocean would be brought to the surface and used to cool the working fluid. Once liquified, the working fluid would be ready for a second turn of the generating cycle.
OTEC plants are attractive alterative energy sources in regions near the equator, where surface temperatures may reach 77°F (25°C) or more. These parts of the ocean are often adjacent to less developed countries , where energy needs are growing.
Wherever they are located, OTEC plants have a number of advantages. For one thing, oceans cover nearly 70 percent of the planet's surface so that the raw material OTEC plants need—seawater—is readily available. The original energy source—sunlight—is also plentiful and free. Such plants are also environmentally attractive since they produce no pollution and cause no disruption of land resources. Planners suggest that a by-product of OTEC plants might be nutrients brought up from deeper ocean levels and used to feed "farms" of fish or shellfish.
Unfortunately, many disadvantages exist also. The most important is the enormous cost of building and maintaining the mammoth structures needed for an OTEC plant. Also, the temperature differential available under even the best of conditions means that an OTEC plant will not be more than about 3% efficient.
Currently, the disadvantages of OTEC plants are so great that none has even been built. Research continues in a number of countries, but some experts believe that the low efficiency of OTEC means that this technology will never be able to compete economically with other alternative sources of energy.
[David E. Newton ]
Fisher, A. "Energy from the Sea." Popular Science (June 1975): 78–83.
Haggin, J. "Ocean Thermal Energy Conversion Experiment Slated for Hawaii." Chemical & Engineering News (February 10, 1986): 24–26. Penney, T. R., and D. Bharathan, "Power from the Sea." Scientific American 256 (January 1987): 86–92.
Walters, S. "Power in the Year 2001, Part 2—Thermal Sea Power." Mechanical Engineering (October 1971): 21–25.
Whitmore, W. "OTEC: Electricity from the Ocean." Technology Review (October 1978): 58–63.
"Ocean Thermal Energy Conversion." Environmental Encyclopedia. . Encyclopedia.com. (November 15, 2018). https://www.encyclopedia.com/environment/encyclopedias-almanacs-transcripts-and-maps/ocean-thermal-energy-conversion
"Ocean Thermal Energy Conversion." Environmental Encyclopedia. . Retrieved November 15, 2018 from Encyclopedia.com: https://www.encyclopedia.com/environment/encyclopedias-almanacs-transcripts-and-maps/ocean-thermal-energy-conversion
Encyclopedia.com gives you the ability to cite reference entries and articles according to common styles from the Modern Language Association (MLA), The Chicago Manual of Style, and the American Psychological Association (APA).
Within the “Cite this article” tool, pick a style to see how all available information looks when formatted according to that style. Then, copy and paste the text into your bibliography or works cited list.
Because each style has its own formatting nuances that evolve over time and not all information is available for every reference entry or article, Encyclopedia.com cannot guarantee each citation it generates. Therefore, it’s best to use Encyclopedia.com citations as a starting point before checking the style against your school or publication’s requirements and the most-recent information available at these sites:
Modern Language Association
The Chicago Manual of Style
American Psychological Association
- Most online reference entries and articles do not have page numbers. Therefore, that information is unavailable for most Encyclopedia.com content. However, the date of retrieval is often important. Refer to each style’s convention regarding the best way to format page numbers and retrieval dates.
- In addition to the MLA, Chicago, and APA styles, your school, university, publication, or institution may have its own requirements for citations. Therefore, be sure to refer to those guidelines when editing your bibliography or works cited list.