• Ocean energy refers to renewable energy derived from the sea, with three main types: wave, tidal, and ocean thermal.
• The Ministry of New and Renewable Energy in India has declared Ocean Energy as a renewable energy source.

Types of Ocean Energy

• Wave Energy:
  • Wave energy is generated by converting the energy within ocean waves into electricity.
  • Different technologies are being developed and tested to harness wave energy.
  • The first wave energy project with a capacity of 150 MW is located at Vizhinjam near Trivandrum.
  • Wave energy has not been fully exploited for human purposes except for power supplies for buoys and navigational aids.
  • Wave power is produced by the up and down motion of floating devices placed on the ocean surface.
  • High-tech devices capture the natural movements of ocean currents and the flow of swells to generate power.
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• Current Energy:
  • Underwater turbines moved by marine currents generate electricity
  • According to the Intergovernmental Panel on Climate Change (IPCC), given the scale of open ocean currents, there is a promise of significant project scale growth when technologies harness lower-velocity currents.
• Tidal energy:
  • Power plants built on river estuaries generate electricity by holding back and releasing tidal water
  • Tides are formed due to gravitational effect of sun and moon on earth
  • Tidal power has great potential in areas with sufficient tidal height for construction of tidal power plants
  • Energy can be extracted from tides by passing tidal water through turbines
  • India has a potential of 9,000 MW of tidal energy
  • Major tidal wave power project costing Rs. 5000 crores proposed in Gulf of Kutch, Gujarat
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• Ocean Thermal Energy:
  • Oceans store large amounts of heat energy due to their coverage of almost 70% of Earth’s surface.
  • The temperature difference between the warm surface waters and the cold deeper layers can be utilized to generate steam and power.
  • Solar energy is also stored in oceans and seas, with tropical seas absorbing an average of solar radiation equivalent to the heat content of 245 billion barrels of oil.
  • Ocean Thermal Energy Conversion (OTEC) is the process of harnessing this energy by using the temperature differences between the ocean surface and depths of about 1000 meters to operate a heat engine that produces electric power.
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• Osmotic Energy:
  • This technique produces energy from the movement of water across a membrane between a saltwater reservoir and fresh water reservoir. It is also called Salinity Gradient Energy.
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Salient Features:

• Predictable and reliable source of energy.
• Global presence of tidal streams and ocean currents.
• High energy density of moving water.
• Unlimited usage area due to the vast and deep oceans.

Limitations:

• Limited deployment and underutilization of existing technologies.
• Lack of research on some technologies and most are at the initial stage of R&D, demonstration, and commercialization.
• Uncertainty of the marine environment and commercial scale risks.

Potential:

• Tidal energy potential of 12,455 MW identified in Khambat & Kutch regions and large backwaters.
• Wave energy theoretical potential of 40,000 MW.
• OTEC theoretical potential of 180,000 MW in India.

Suggestions:

• India’s long coastline with estuaries and gulfs can be fully utilized for ocean energy.
• Tidal streams and ocean currents can be used for large scale electricity generation with relatively small environmental interactions.
• More inputs from prominent institutions can help in faster development of ocean energy technologies.