Relevance: mains: G.S paper I: Geography & G.S paper II: Infrastructure: Energy, Ports, Roads, Airports, Railways etc.
What is Ocean Energy?
- Oceans cover 70 percent of the earth’s surface and represent an enormous amount of energy in the form of wave, tidal, marine current and thermal gradient.
- A variety of different technologies are currently under development throughout the world to harness this energy in all its forms.
- Deployment is currently limited but the sector has the potential to grow, fuelling economic growth, reduction of carbon footprint and creating jobs not only along the coasts but also inland along its supply chains.
- As Government of India steps up its effort to reach the objectives to contemplate its Renewable Energy and climate change objectives post 2022, it is opportune to explore all possible avenues to stimulate innovation, create economic growth and new jobs as well as to reduce our carbon footprint.
- India has a long coastline with the estuaries and gulfs.
- MNRE looks over the horizon at development of new technology and considers the various options available to support its deployment.
What is the potential of Ocean energy?
- 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 in India along the country’s coast is estimated to be about 40,000 MW – these are preliminary estimates. 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.
What are the technologies of Ocean Energy?
- Tidal Energy: The tidal cycle occurs every 12 hours due to the gravitational force of the moon.
- The difference in water height from low tide and high tide is potential energy.
- Similar to traditional hydropower generated from dams, tidal water can be captured in a barrage across an estuary during high tide and forced through a hydro-turbine during low tide.
- The Gulf of Cambay and the Gulf of Kutch in Gujarat on the west coast have the locations in the country where potential exists.
- Wave Energy: Wave energy is generated by the movement of a device either floating on the surface of t Wave conversion devices that float on the surface have joints hinged together that bend with the waves.
- This kinetic energy pumps fluid through turbines and creates electric power. • Stationary wave energy conversion devices use pressure fluctuations produced in long tubes from the waves swelling up and down.
- This bobbing motion drives a turbine when critical pressure is reached. Other stationary platforms capture water from waves on their platforms.
- This water is allowed to runoff through narrow pipes that flow through a typical hydraulic turbine.
- Current Energy: Marine current is ocean water moving in one direction.
- This ocean current is known as the Gulf Stream.
- Tides also create currents that flow in two directions.
- Kinetic energy can be captured from the Gulf Stream and other tidal currents with submerged turbines that are very similar in appearance to miniature wind turbines.
- Similar to wind turbines, the movement of the marine current moves the rotor blades to generate electric power.
- Ocean Thermal Energy Conversion (OTEC): Ocean thermal energy conversion, or OTEC, uses ocean temperature differences from the surface to depths lower than 1,000 meters, to extract energy.
- A temperature difference of only 20°C can yield usable energy.
- Research focuses on two types of OTEC technologies to extract thermal energy and convert it to electric power: closed cycle and open cycle.
- In the closed cycle method, a working fluid, such as ammonia, is pumped through a heat exchanger and vaporized. This vaporized steam runs a turbine. • The cold water found at the depths of the ocean condenses the vapor back to a fluid where it returns to the heat exchanger.
- In the open cycle system, the warm surface water is pressurized in a vacuum chamber and converted to steam to run the turbine.
- The steam is then condensed using cold ocean water from lower depths.
What is Geothermal Energy?
- Geothermal Energy is heat stored in earth crust and being used for electric generation and also for direct heat application worldwide since beginning of last century.
- USA, Philippines, Indonesia, Turkey, and New Zealand are leading countries availing commercial exploitation with worldwide installation of 12800 MW at end of 2017.
- Geothermal electricity generation is site and technology specific and India is in Low Geothermal Potential Region with low/medium heat enthalpy.
- Government is planning to encourage the industry lead demonstration projects at the first stage to assess the technical viability of the project before going to the commercial models.
What are the different technologies in Geothermal Energy?
- Dry Steam Power Plants: They draw from underground resources of steam.
- The steam is piped directly from underground wells to the power plant, where it is directed into a turbine/generator unit.
- Flash Steam Power Plants: They use geothermal reservoirs of water with temperatures greater than 360°F (182°C).
- This very hot water flows up through wells in the ground under its own pressure.
- As it flows upward, the pressure decreases and some of the hot water boils into steam.
- The steam is then separated from the water and used to power a turbine/generator.
- Any leftover water and condensed steam are injected back into the reservoir, making this a sustainable resource.
- Binary Cycle Power Plants: They operate on water at lower temperatures of about 225°-360°F (107°-182°C).
- These plants use the heat from the hot water to boil a working fluid, usually an organic compound with a low boiling point.
- The working fluid is vaporized in a heat exchanger and used to turn a turbine. • The water is then injected back into the ground to be reheated.
- The water and the working fluid are kept separated during the whole process, so there are little or no air emissions.