(GIST OF YOJANA) Geo-Thermal and Ocean Energy Technologies [JUNE-2019]


(GIST OF YOJANA) Geo-Thermal and Ocean Energy Technologies

[JUNE-2019]


Geo-Thermal and Ocean Energy Technologies

Introduction

  • Accordingly, an ambitious target has been set of installing 175 GW of renewable energy capacity by 2022.
  • This includes 100 GW from solar, 60 GW from wind, 10 GW from bio power and 5 GW from small hydro power. As on date, around 77 GW of renewable energy capacity has been installed in the country with major share coming from solar and wind power technologies.
  • The possibility of venturing into new emerging renewable energy technologies, such as Floating Solar. Offshore wind, solar wind hybrid, energy storage, etc is also being explored.
  • However, renewable energy technologies such as geo-thermal and ocean energy still remain at a nascent stage in India.

Ocean Energy

  • Oceans occupy more than 70 per cent of earth’s surface and are an inexhaustible source of renewable energy. Ocean energy is the energy harnessed from ocean waves, tidal range (rise and fall) and tidal streams, temperature gradients and salinity gradients. Only few commercial ocean energy power plants have been commissioned till date. Around 536 MW of installed ocean energy capacity is in operation at the. end of 2016, with major share of two large scale tidal barrage plants i.e., the 254 MW Sihwa plant in the South Korea (completed in 2011 ) and the 240 MW La Rance tidal power station in France (completed in 1966 ) Apart from tidal barrage plants which use established tidal turbine technology, other ocean energy technologies are still largely in pre-commercial development stages.

World Scenario

  • Leading countries in Ocean Energy technology are UK, USA, Sweden, Canada, France, South Korea. Examples of few large scale Tidal (Barrage) Plants are 254 MW at South Korea (2011), 240 MW at France (1966), 20 MW at Canada, etc. Ocean Technology, such as Tidal (Current), Wave, Ocean Thermal Energy Conversion (OTEC) are still at pre R&D stage/ Kilo Watt level.

Indian Scenario

  • As per study conducted by IIT Madras, Theoretical Potential for tidal Energy in India is 12500 MW. Promising locations are Gulf of Khambhat and Gulf of Kutch (GJ). Sunderbans (WB), Western Ghats (MH), etc , Theoretical Potential for Wave Energy in India is 41.000 MW , Promising locations are, Western coast of Maharashtra, Goa, Karnataka, Kerala, Kanyakumari, Southern tip of India, etc. However, resource survey at target locations i.e., Western Ghats, Eastern Ghats, etc, may be undertaken to assess validate actual potential.
    Technology

Tidal Energy

  • The tidal cycle occurs every 12 hours due to the gravitational pull of the moon. The difference in water level from low tide and high tide is potential energy that can be harnessed. Similar to hydropower generated from dams, tidal water is captured in a barrage across an estuary during high tide and forced through a turbine during low tide.
  • The capital cost for tidal energy power plants is very high due to high civil construction that results in high power tariff. In order to harness power from the tidal energy, the height of high tide must be at least five meters (16 feet) greater than low tide.

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 by the force generated by the ocean waves. Many different techniques for convening wave energy to electric power have been developed, Wave conversion devices floats on the surface have joints hinged together that moves with the waves. The kinetic energy pumps fluid through turbines and generates electric power Moored wave energy conversion devices use pressure fluctuations produced in long tubes from the waves moving up and down. This wave motion drives a turbine. Current Energy
  • Ocean current is ocean water moving in one direction. This ocean current is also known as the Gulf Stream 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 harness energy. A temperature difference of even 20°C can yield energy efficiently Research focuses are on two types of OTEC technologies to extract thermal energy and convert it to electric power closed cycle and open cycle.

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Technology

  • Power Generation: Hot water and steam from deep underground can be piped up through underground wells and used to generate electricity in a power plant. There are three types of geothermal power plants:
  • Dry Steam Plants which use geothermal steam directly. Dry steam power plants use very hot (>235 °C) steam from the geothermal reservoir. The steam goes directly through a pipe to a turbine to spin a generator that produces electricity.
  • Flash Steam Plants which use high pressure hot water to produce steam . Flash steam power plants use hot water (> 182 °C) from the geothermal reservoir. When the water is pumped to the generator, it is released from the pressure of the deep reservoir, The sudden drop in pressure causes some of the water to vaporize to steam, which spins a turbine to generate electricity. Hot water not flashed into steam is returned to the geothermal reservoir through injection wells.
  • Binary Cycle Plants which use moderate temperature water (107 to 182°C) from the geothermal reservoir. In binary systems, hot geothermal fluids are passed through one side of a heat exchanger to heat a working fluid in a separate adjacent pipe. The working fluid, usually an organic compound with a low boiling point such as Iso-butane or Iso- pentane, is vaporized and passed through a turbine to generate electricity.

Other thermal applications:

  • Apart from geothermal power generation , this renewable source can be utilized directly for thermal applications through these technologies:-
  • Space/District Heating: in areas where hot springs or geothermal reservoirs are near the Earth's surface, hot water can be piped in directly to heat homes or office buildings.
  • Geothermal water is pumped through a heat exchanger, which transfers the heat from the water into the building’s heating system. The  used water is injected back down a well into the reservoir to be reheated and used again.
  • Geothermal Heat Pump/Ground Source Heat Pumps: A few feet under the ground, the soil or water remain a constant 50 to 60 degrees Fahrenheit (10-15 degrees Celsius) year-round. In this method , geothermal heat pumps use a system of buried pipes linked to a heat exchanger and ductwork into buildings In winter the relatively warm earth transfers heat into the buildings and in summer the buildings transfer heat to the ground or uses some of it to heat water. These heat pumps function as both air-conditioning and heating systems.
  • Fluid circulates through a series of pipes under the ground or beneath the water of a pond or lake and into a building. An electric compressor and heat exchanger pull the heat from the pipes and send it via a duct system throughout the building. In the summer the process is reversed. The pipes draw heat away from the house and carry it to the ground or water outside where it is absorbed.

Way forward

  • Industry led, applied R and D proposals to harness geothermal energy under Research, Design, Development and Demonstration (RDDandD) policy are necessary for this renewable energy source to become operational.
  • Plans should be made to develop Demonstration projects initially each tor geothermal electricity' production & direct heat use applications. PSUs may undertake resource assessment with support from leading countries as geothermal expert.
  • Projects for space cooling and industrial process heating using GSHP technology may be supported through subsidy, preferential tariff front power companies as technology is energy water efficient.

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