The world’s less known renewable energy conversion system is called OTEC (Ocean Thermal Energy Conversion). OTEC (Ocean Thermal Energy Conversion’s) idea was conceived by French engineer Jacques D’Arsonval in 1881. USA started research on OTEC for the first time in 1974 with one of the world’s leading test laboratories Natural Energy Laboratory of Hawaii Authority. A 105 KW demonstration OTEC plant was set up at the laboratory site, which was being supported by US Navy. The plant started its operations in 1990 and 2015 supplied electricity to the US electricity grid. This plant was working on an experimental basis, whereas many other countries also stated planning for electricity supply and desalinated water for their people or inhabitants on islands. The desalination process is to remove salts from water and make it useable for daily use. Currently, eight countries are active in the research and development of OTEC Systems and have launched numerous projects. They are the United Kingdom, Netherland, Norway, France, Sweden, Taiwan, Japan, and the United States of America.
OTEC can potentially be an alternative energy source, but it needs many funds for exploration and research. OTEC plants need a very high capital cost. The plant size of the 10 MW OTEC System is compatible with the size of an average platform. However, the best part is that it is clean energy and has no pollutants to send into the air.
Basically, there are two types of OTEC systems
- Closed Cycle
- Open Cycle
The Closed Cycle uses a working fluid as AMMONIA
The Open Cycle uses the surface water itself as a working fluid
The Hybrid cycle is a combination of both Open and Closed cycles, but it is not tested yet. OTEC System uses the Carnot cycle to generate electricity at very low efficiency. Theoretically, this efficiency is around 7%, but practically it hardly reaches 3%. OTEC system uses the Carnot cycle to generate electricity at very low efficiency.
The heat from the sun makes the surface of the seas and oceans warm. Especially in tropical regions, seas, and oceans, the surface water becomes much warmer; therefore, the water temperature can help produce energy and desalination. OTEC systems use at least 77 Fahrenheit of temperature to run a turbine for electricity production. Warm water from the ocean surface is pumped through an evaporator containing a working fluid that drives the turbines and generators. At the second stage, the vaporized water is turned back to a liquid in a condenser which is cooled with cold ocean water.
However OTEC system produces electricity, but in the Open and Hybrid Cycle, it can be a good source to produce freshwater as a by-product.
The main benefit of the OTEC System could be that it would create the potential to reduce atmospheric CO2 through the combined effect of biological growth and mineral addition.
Whereas its disadvantages are observed, experts fear changing local or global weather due to hot and cold weather conversions. But this is very rare so far. The best suited geographical areas for OTEC systems are America, Africa, Indian, and Pacific Oceans.
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