Ocean Energy | 09 Sep 2019

Recently, the Ministry of New and Renewable Energy has declared Ocean Energy as renewable energy.
Includes all forms of ocean energy such as tidal, wave, current, ocean thermal etc and makes them eligible for meeting the non-solar Renewable Purchase Obligations (RPO).

Oceans’ water movement creates a vast store of kinetic energy (energy in motion) in the various forms of renewable energy viz wave energy, tidal energy, ocean current energy, salinity gradient energy and ocean thermal gradient energy which can be harnessed to generate electricity.

Tidal Energy- Like conventional hydroelectric dams, power plants are built on river estuaries and hold back huge amounts of tidal water twice a day which generates electricity when released. India is expected to have 9,000 MW of tidal energy potential.
Wave Energy- This is generated by the movement of a device either floating on the surface of the ocean or moored to the ocean floor.
Current Energy- It is very similar to the wind above the oceans. Underwater turbines, large propellers tethered to the seabed, are moved with the marine currents to 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.

The Intergovernmental Panel on Climate Change (IPCC)

It was created in 1988 by the World Meteorological Organization (WMO) and the United Nations Environment Programme (UNEP).
Currently has 195 members.
Headquartered in Geneva, Switzerland.
It has the objective to provide governments at all levels with scientific information that they can use to develop climate policies.
It provides regular assessments of the scientific basis of climate change, its impact and future risks, and options for adaptation and mitigation.
It gives the report on Renewable Energy Sources and Climate Change Mitigation among other various reports.

Ocean Thermal Energy- Oceans are huge heat reservoirs as they cover almost 70% of Earth’s surface. The temperature difference between warm surface waters and the cold deeper layers can be used to generate steam and then power.

Ocean Thermal Energy Conversion (OTEC)

The technology which uses ocean temperature differences from the surface to depths lower than 1,000 meters, to extract energy.
Research focuses on two types of OTEC technologies-
- In Closed cycle method, 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.
- In Open cycle method, 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.
It has high (94%) capacity factor which makes it the best power source and although it has a high initial cost, low maintenance and regular power supply makes it an attractive alternative.
OTEC is supplied by an infinite supply of solar energy and the stored energy in it after sundown makes it a 24 hour power supplier.
There are no emissions from the OTEC power plants so air quality will not be degraded.

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.

Predictable and Reliable: Unlike wind, ocean energy sources are more predictable. The endless flows create a reliable supply source for future availability.
Global presence: Tidal streams and ocean currents are available almost everywhere across the globe.
Energy-rich: Moving water is more than 800 times denser than moving air, which multiplies the kinetic energy by the same factor and opens up the scope of huge amounts of energy.
Unlimited usage area: Land is a scarce resource for many regions so on-shore solutions have to compete and can extend to a limit but ocean energies are provided by the vast and deep oceans ending the competition.

To accelerate and enhance support for the resource assessment and deployment of ocean energy in the country.
To harness the ocean energies for power generation and to overcome the barrier of energy deficiency.
This sector has been opened to the public and private sectors so that more projects can be carried out in India.
Industry led research and development proposals are invited from stakeholders, for solving problems in Indian conditions.

Deployment is currently limited in our country and already deployed technologies are under utilised.
Either there is not much research done on the technologies or most are currently at the initial stage of R&D, demonstration and commercialization.
Uncertainty of the marine environment and commercial scale risks like- corrosion of materials due to the salinity of seawater, offshore maintenance difficulties, the environmental impact on landscapes and the marine ecosystem and competition from other marine activities such as fishing.

Total identified potential of Tidal Energy is about 12455 MW, with potential locations identified at Khambat & Kutch regions, and large backwaters, where barrage technology could be used.
The total theoretical potential of wave energy is estimated to be about 40,000 MW. This energy is however less intensive than what is available in more northern and southern latitudes.
OTEC has a theoretical potential of 180,000 MW in India subject to suitable technological evolution.
Ocean energy has the potential to grow fully, fuelling economic growth, reducing carbon footprint and creating jobs not only along the coasts but also inland along its supply chains.

India has a long coastline with the estuaries and gulfs which can be fully used to harness this energy.
Tidal streams and ocean currents are huge and almost endless resources which can be used with relatively small environmental interactions for large scale electricity generation.
Basic R&D is being looked after by National Institute of Ocean Technology, Chennai under the Ministry of Earth Sciences but more inputs by other prominent institutions will help us understand and develop the technologies faster.

National Institute of Ocean Technology (NIOT)

Established in November 1993 as an autonomous society under the Ministry of Earth Sciences, Government of India.
It aims to develop reliable indigenous technologies to solve various engineering problems associated with harvesting of non-living and living resources in the Indian Exclusive Economic Zone.

Ocean energy technology can help India stimulate innovation, create economic growth and new jobs as well as to reduce its carbon footprint.
It will also help India to support its neighbouring countries who have energy deficits, for their better economic growth and can guide them on their way to being self sufficient in energy sector.