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What is geothermal energy?

Geothermal energy is thermal energy generated and stored in the Earth.The Geothermal energy of the Earth's crust originates from the original formation of the planet (20%) and from radioactive decay of minerals (80%). The geothermal gradient , which is the difference in temperature between the core of the planet and its surface, drives a continuous conduction of thermal energy in the form of heat from the core to the surface.The Earth's geothermal resources are theoretically more than adequate to supply humanity's energy needs, but only a very small fraction may be profitably exploited.

How it works?

At the core of the Earth, thermal energy is created by radioactive decay and temperatures may reach over 5000 degrees Celsius (9,000 degrees Fahrenheit).Heat conducts from the core to surrounding cooler rock.The high temperature and pressure cause some rock to melt, creating magma convection upward since it is lighter than the solid rock.The magma heats rock and water in the crust, sometimes up to 370 degrees Celsius (700 degrees Fahrenheit).

Advantages & Disadvantages

  • Fluids drawn from the deep earth carry a mixture of gases, notably carbon dioxide ( CO 2 ), hydrogen sulfide ( H 2 S ), methane ( CH 4 ) and ammonia ( NH 3 ).These pollutants contribute to global warming , acid rain , and noxious smells if released.Plant construction can adversely affect land stability.Geothermal has minimal land and freshwater requirements.Some of the legal issues raised by geothermal energy resources include questions of ownership and allocation of the resource, the grant of exploration permits, exploitation rights, royalties.
  • Geothermal power is considered to be renewable because any projected heat extraction is small compared to the Earth's heat content.By using geothermal sources of energy present generations of humans will not endanger the capability of future generations to use their own resources to the same amount that those energy sources are presently used.Geothermal power requires no fuel (except for pumps), and is therefore immune to fuel cost fluctuations.Geothermal power is highly scalable: from a rural village to an entire city.

History & Applications

Mountain Lishan


The Geysers

Hot springs have been used for bathing at least since paleolithic times The oldest known spa is a stone pool on China ’s Lishan mountain built in the Qin dynasty in the 3rd century BC, at the same site where the Huaqing Chi palace was later built.The world's oldest geothermal district heating system in Chaudes-Aigues , France, has been operating since the 14th century.The earliest industrial exploitation began in 1827 with the use of geyser steam to extract boric acid from volcanic mud in Larderello ,Italy. The International Geothermal Association (IGA) has reported that 10,715 megawatts (MW) of geothermal power in 24 countries is online, which is expected to generate 67,246 GWh of electricity in 2010. This represents a 20% increase in online capacity since 2005.In 2010, the United States led the world in geothermal electricity production with 3,086 MW of installed capacity from 77 power plants. The largest group of geothermal power plants in the world is located at The Geysers ,a geothermal field in California .The Philippines is the second highest producer, with 1,904 MW of capacity online.