Non-conventional sources are turning out to be significant sources of energy for humanity. With global warming a certainty, it is imperative that we turn to non-polluting and renewable sources of energy. One such source of energy is Ocean Thermal Energy Conversion (OTEC).
Ocean Thermal Energy (OTEC)
Ocean thermal energy conversion is an electricity generation system. Ocean Thermal Energy, also called Ocean Thermal Energy Conversion (OTEC), refers to using the temperature difference between the deep parts of the sea, which are cold and the shallow parts of the sea, which are cold, to run a heat engine and produce useful work. The deeper parts of the ocean are cooler because the heat of sunlight cannot penetrate very deep into the water. Here the efficiency of the system depends on the temperature difference. Greater the temperature difference, the greater the efficiency. The temperature difference in the oceans between the deep and shallow parts is maximum in the tropics, 20 to 25o C. Tropics receive a lot of sunlight which warms the surface of the oceans, increasing the temperature gradient.
The energy source of OTEC is abundantly available, free, and will be so for as long as the sun shines and ocean currents exist. Estimates suggest that ocean thermal energy could contain more than twice the world’s electricity demand. This makes it necessary for us to give it a closer look.
Types of Ocean Thermal Energy Conversion Systems
- Closed Cycle: Closed cycle Ocean Thermal Energy Conversion systems use a working fluid with a low boiling point, Ammonia, for example, and use it to power a turbine to generate electricity. Warm seawater is taken in from the surface of the oceans and cold water from the deep at 5o. The warm seawater vaporises the fluid in the heat exchanger, turning the generator’s turbines. The fluid now in the vapour state is brought in contact with cold water, which turns it back into a liquid. The fluid is recycled in the system, which is why it is called a closed system.
- Open Cycle: Open cycle OTEC directly uses the warm water from the surface to make electricity. The warm seawater is first pumped into a low-pressure chamber, where it undergoes a drop in boiling point due to the pressure drop. This causes the water to boil. This steam drives a low-pressure turbine which is attached to an electrical generator. The advantage this system has over a closed system is that, in the open cycle, desalinated water is obtained in the form of steam. Since it is steam, it is free from all impurities. This water can be used for domestic, industrial, or agricultural purposes.
Ocean Thermal Energy (OTEC) is a real candidate as one of the future sources of energy. Its environmental impact is negligible. The mixing of deep and shallow seawater brings up nutrients from the seafloor. The deepwater is rich in nitrates, which can also be used in agriculture.
Watch the video to find out why is it so important to conserve fossil fuels and use them wisely?
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