Ocean Energy
1. Introduction to 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. The energy potential of our seas and oceans well exceeds our present energy needs. India has a long coastline with the estuaries and gulfs where tides are strong enough to move turbines for electrical power generation. A variety of different technologies are currently under development throughout the world to harness this energy in all its forms including waves (40,000 MW), tides (9000 MW) and thermal gradients (180,000 MW). 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. Given the long-term energy need through this abundant source, action needs to be taken now on RDD&D front in order to ensure that the ocean energy sector can play a meaningful part in achieving our objectives in coming decades. MNRE looks over the horizon at a promising new technology and considers the various options available to support its development. Over 100 different ocean energy technologies are currently under development in more than 30 countries. Most types of technologies are currently at demonstration stage or the initial stage of commercialization.
2. Programme Objectives The objective of the programme is to accelerate and enhance support for the research, development, resource assessment, testing and deployment of ocean energy in the country and to harness it for power generation and to overcome the barriers by encouraging collaboration between the technology developers, investors and other stakeholders so as to bridge the gap between research and the market. Resource Assessment is being planned in 2015-18 for public domain in association with IIT’s, NIOT and alike Government Research Institute to expedite the potential analysis and site identification in coordination with MNRE.
3. History
- Total identified potential of Tidal Energy is about 9000 MW in West Coast Gulf of Cambay (7000 MW), Gulf of Kutch (1200 MW) and in East Coast the Ganges Delta in the Sunderbans in West Bengal for small scale tidal power development estimates the potential in this region to be about 100 MW.
- The total available potential of wave energy in India along the 6000 Km of India’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.
- In 2000 NIOT Goa, launched a programme to conduct study on technologies for producing high quality clean drinking water and energy from the ocean. The objective was to generate 2 - 3 lakh litres per day freshwater using the Low Temperature Thermal Desalination technology by 1 MW OTEC Power Plant. But it was dropped due to difficulties in installations.
- In 2010 Kalpasar Tidal Power Project at The Gulf of Khambhat was identified as a promising site for tidal power generation by UNDP Expert.
- In Jan 2011, the state of Gujarat announced plans to install Asia’s first commercial-scale tidal current power plant; the state government approved the construction of a 50 MW project in the Gulf of Kutch.
- None at the moment, but India’s Ministry of New and Renewable Energy said in Feb 2011 that it may provide financial incentives for as much as 50 percent of the cost for projects seeking to demonstrate tidal power.
- In 2014 Atlantis Energy proposed to install and develop 50-200 MW Tidal stream based power plant at Gulf of Chambey.
a) Wave Energy
Wave energy is generated by the movement of a device either floating on the surface of the ocean or moored to the ocean floor. Many different techniques for converting wave energy to electric power have been studied. 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. Wave energy is proving to be the most commercially advanced of the ocean energy technologies with a number of companies competing for the lead.
b) 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. To capture sufficient power from the tidal energy potential, the height of high tide must be at least five meters (16 feet) greater than low tide. There are only approximately 20 locations on earth with tides this high and India is one of them. The Gulf of Cambay and the Gulf of Kutch in Gujarat on the west coast have the maximum tidal range of 11m and 8m with average tidal range of 6.77m and 5.23m respectively.
c) 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. As with wind turbines, the constant movement of the marine current moves the rotor blades to generate electric power.
d) 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. OTEC has a potential installed capacity of 180,000 MW in India.
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