OTEC Plant in Lakshadweep | 09 Aug 2022

Why in News?

Recently, the National Institute of Ocean Technology, an autonomous institute under the Union Ministry of Earth Sciences (MoES) is establishing an Ocean Thermal Energy Conversion Plant with a capacity of 65 kilowatts (kW) in Kavaratti, Lakshadweep.

• The plant will power the one lakh liter per day low temperature thermal desalination plant, which converts seawater into potable water.
• The plant is the first of its kind in the world as it will generate drinking water from sea water using indigenous technology, green energy and environmentally friendly processes.

What is Ocean Thermal Energy Conversion?

• About:
  • Ocean Thermal Energy Conversion (OTEC) is a process for producing energy by harnessing the temperature differences (thermal gradients) between ocean surface waters and deep ocean waters.
    • Oceans are huge heat reservoirs as they cover almost 70% of Earth’s surface.
  • Researchers focus on two types of OTEC technologies-
    • Closed cycle method - where a working fluid (ammonia) is pumped through a heat exchanger for evaporation and the steam runs a turbine.
      • The vapour is turned back to fluid (condensation) by the cold water found at the depths of the ocean where it returns to the heat exchanger.
    • Open cycle method - where the warm surface water is pressurized in a vacuum chamber and converted to steam which runs the turbine. The steam is then condensed using cold ocean water from lower depths.
• Historical perspective:
  • India initially had planned to set up an OTEC plant way back in 1980, off the Tamil Nadu coast. However, with the foreign vendor closing down its operation, it had to be abandoned.
• India’s OTEC Potential:
  • As India is geographically well-placed to generate ocean thermal energy, with around 2000 kms of coast length along the South Indian coast, where a temperature difference of above 20°C is available throughout the year.
  • The total OTEC potential around India is estimated as 180,000 MW, considering 40% of gross power for parasitic losses.

How does an OTEC Plant Work?

• About:
  • As the energy from the sun heats the surface water of the ocean. In tropical regions, surface water can be much warmer than deep water.
  • This temperature difference can be used to produce electricity and desalinate ocean water.
    • Ocean Thermal Energy Conversion (OTEC) systems use a temperature difference (of at least 77°F) to power a turbine to produce electricity.
    • Warm surface water is pumped through an evaporator containing a working fluid. The vaporized fluid drives a turbine/generator.
    • Then the vaporized fluid is turned back to a liquid in a condenser cooled with cold ocean water pumped from deeper into the ocean.
    • OTEC systems use seawater as the working fluid and can use condensed water to produce desalinated water.
• Significance:
  • Two of the biggest advantages of OTEC are that it produces clean environmentally friendly renewable energy and, unlike solar plants which can't work at night and wind turbines which only work when it's windy, OTEC can produce energy at all times.

What are the Related Recent Initiatives of the Government?

• Deep Sea Mining:
  • The MoES is developing technologies for mining deep sea resources like polymetallic nodules from the Central Indian Ocean at a water depth of 5,500 meters.
• Weather Forecasting:
  • The ministry is also working on introducing ocean climate change advisory services for climate risk assessment due to sea level rise; cyclone intensity and frequency; storm surges and wind waves; biogeochemistry, and changing harmful algal blooms in the coastal waters of India.
• Deep Ocean Mission:
  • MoES is trying to design and develop a prototype crewed submersible rated for 6,000 meters of water depth under the Deep Ocean Mission.
  • It will include technologies for underwater vehicles and underwater robotics.
• DNA Bank:
  • There efforts are being made to improve the detection, sampling and DNA storage of benthic fauna of the northern Indian Ocean through systematic sampling using a remotely operated vehicle.

Source: DTE