Geothermal energy

05 Sources of energy


• Geothermal energy is the heat energy from hot rocks present inside the earth.




  • Due to geological changes, molten rocks formed in the deeper hot regions of earth’s crust are pushed upward and trapped in certain regions called ‘hot spots’.


  • When underground water comes in contact with the hot spot, steam is generated. Sometimes hot water from that region finds outlets at the surface.
  • Such outlets are known as hot springs.


  • Hydrothermal convection system is used to harness geothermal energy.
  • A pipe is inserted through a hole which is drilled deep inside the earth.
  • The steam trapped in rocks is routed through a pipe to a turbine.
  • This high pressure steam turns the turbine of a generator to produce electricity which is used to generate electricity.
  • Steam may also be used to heat water from an external source which is then used to rotate the turbine.
Geothermal gradient


  • Geothermal gradient is defined as the difference in the temperature between the core and the crust of the planet which may exceed 4000 °C, in some places.
  • Geothermal gradient is the driving force for a continuous conduction of thermal energy in the form of heat from the core to the surface..


  • Geothermal energy is free and abundant resource to an estimated time span of 4 billion years.
  • Geothermal energy is non-polluting and environment friendly and no residue or by-product is generated.
  • Geothermal power plants are highly sophisticated and involve large scale research before installation. This generates the employment for skilled and unskilled labors at a very large scale at each stage of production and management.
  • In cold countries, the geothermal energy is used directly for melting of ice on the roads, heating houses in winters, green houses, public baths etc.
  • Although the initial cost of installation is very high, the cost for maintenance and repair is negligible.


  • Geothermal energy cannot be transported easily and there are chances of emission of toxic gases getting released into the atmosphere during transmission.
  • The installation of geothermal power plants requires a huge investment in terms of material and human resource.
  • Extensive research is required, as the sites can run out of steam over a period of time due to a drop in the temperature as a result of excessive or irregular supply of inlet water.
  • The source of geothermal energy is available in limited regions, some of which are highly inaccessible, which makes the process economically infeasible.
  • The process of drilling may result in release of highly toxic gases into the environment near these sites, which sometimes prove fatal to the workforce involved in the process.


  • The steam from the geothermal reserves is either directly used to rotate the turbines of an electrical generatoror is used to heat water which then produces steam for the process.
  • In cold countries, geothermal energy is used to heat greenhouses or to heat water that are used for irrigation.
  • Geothermal energy is used in industries for the purpose of food dehydration, milk pasteurizing, gold mining etc.
  • Geothermal energy is used to heat buildings through district heating systems in which hot water through springs is directly transported to the buildings though pipelines.

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