GC: n
CT: What is OTEC? Ocean Thermal Energy Conversion (OTEC) is a marine renewable energy technology that harnesses the solar energy absorbed by the oceans to generate electric power. The sun’s heat warms the surface water a lot more than the deep ocean water, which creates the ocean’s naturally available temperature gradient, or thermal energy.
OTEC uses the ocean’s warm surface water with a temperature of around 25°C (77°F) to vaporize a working fluid, which has a low-boiling point, such as ammonia. The vapor expands and spins a turbine coupled to a generator to produce electricity. The vapor is then cooled by seawater that has been pumped from the deeper ocean layer, where the temperature is about 5°C (41°F). That condenses the working fluid back into a liquid, so it can be reused. This is a continuous electricity generating cycle.
The efficiency of the cycle is strongly determined by the temperature differential. The bigger the temperature difference, the higher the efficiency. The technology is therefore viable primarily in equatorial areas where the year-round temperature differential is at least 20 degrees Celsius or 36 degrees Fahrenheit.
S: http://www.otecnews.org/what-is-otec/ (last access: 27 December 2014)
N: 1. Ocean Thermal Energy Conversion technology, known as OTEC, uses the ocean’s natural thermal gradient to generate power. In geographical areas with warm surface water and cold deep water, the temperature difference can be leveraged to drive a steam cycle that turns a turbine and produces power. Warm surface sea water passes through a heat exchanger, vaporizing a low boiling point working fluid to drive a turbine generator, producing electricity.
This process can serve as a baseload power generation system that produces a significant amount of renewable, non-polluting power, available 24 hours a day, seven days a week. Military shore-side bases and communities in the tropics, many of which are largely dependent on imported fossil fuels for power and transportation, are ideal candidates for such a system.
2. The oceans cover more than 70% of Earth’s surface and capture a large part of the sun’s heat in the upper layers, making them the world’s largest solar collectors and energy storage system. Utilizing just a small portion of this energy, can cover the global energy need.
3. The energy source of OTEC is free, available abundantly and is continually being replenished as long as the sun shines and the natural ocean currents exist. Various renowned parties estimate the amount of energy that can be practically harvested to be in the order of 3 to 5 terawatts (1 terawatt is 1012 watts) of baseload power generation, without affecting the temperature of the ocean or the world’s environment. That’s about twice the global electricity demand. The oceans are thus a vast renewable resource, with the potential to contribute to the future energy mix offering a sustainable electricity production method.
The technology is viable primarily in equatorial areas where the year-round temperature differential is at least 20°C (36°F).
S: 1. http://www.lockheedmartin.com/us/products/otec.html (last access: 8 February 2015). 2 & 3. http://www.otecnews.org/what-is-otec/ (last access: 27 December 2014).
SYN: OTEC
S: http://www.otecnews.org/what-is-otec/ (last access: 27 December 2014); GDT – http://www.granddictionnaire.com/ficheOqlf.aspx?Id_Fiche=26513436 (last access: 27 December 2014).
CR: ocean energy, OTEC power plant, ocean’s thermal gradient.
