|Fig. 1: Diagram showing the production of geothermal energy. (Source: Wikimedia Commons)|
The world population has been increasing, coinciding with a rise in energy consumption; average per person energy usage has seen an increase of 15 times between 1850 and 2010.  This rise in energy consumption has led fuel to become more difficult to access, leading to a need to find stable energy sources that are sustainable and economical.  Geothermal energy has emerged as a viable alternate energy source that has the potential to significantly reduce fossil fuel use.
As Figure 1 shows, geothermal energy is created through the decay of radioactive elements heating rocks below the surface; water then comes down through man made springs or natural cracks in the ground and gets heated by the rocks, and then returns to the surface as steam or hot water, which can then be used to power turbines and produce electricity.  Traditionally, geothermal plants were located near geysers as the rocks in those areas were permeable, so hot water could flow through those areas and thoroughly heat the rock.  A 1973 experiment in the Los Alamos Laboratory showed the widespread availability of geothermal energy by demonstrating that geothermal energy can still be created in areas that lack hot water and steam by having cold water seep down into hot rock areas to get heated and become steam. 
Geothermal energy can heat and cool buildings directly and indirectly, eliminating the need to use fossil fuels to heat and air condition buildings.  Though the amount may vary, every square meter of land does have heat flowing through it.  Areas that do not have a large amount of heat flow can still provide energy, in place of fossil fuels, for food processing, drying materials, agricultural activities, greenhouses, aquaculture and paper manufacturing.  In areas that have a higher amount of heat flow, geothermal energy can be used to generate electricity. 
A main benefit of geothermal energy is that it utilizes the flow of heat, which means that it does not need any fuel. Furthermore, using geothermal energy instead of electrical energy reduces greenhouse gas emissions by at least 90%, demonstrating the significant impact geothermal energy can have on fossil fuel consumption.  In Imperial Valley, California, geothermal energy could provide enough energy to fuel the entire southwest for two or three centuries; Imperial Valley has a $300 million geothermal energy business. [2,4] Iceland is another area that has utilized and benefited from geothermal energy. Iceland draws 49% of its energy from geothermal energy, demonstrating how viable of an energy source it is for the country.  The benefits of geothermal energy are clear: 80 countries have geothermal resources, 58 countries actually use geothermal energy directly or for electricity,and 5 countries use geothermal energy for 10% of all their electricity. 
As a result of this increase in population and energy consumption, there is a huge need to develop alternate, sustainable energy sources as there is not enough fuel nor is it sustainable to rely so heavily on fossil fuels. Therefore, geothermal energy has resulted as a very viable solution given that most of the world could be powered by combining geothermal, wind, solar, biomass, and hydrodynamic energy. 
© Britt Mikkelsen. The author grants permission to copy, distribute and display this work in unaltered form, with attribution to the author, for noncommercial purposes only. All other rights, including commercial rights, are reserved to the author.
 W. E. Glassley, Geothermal Energy: Renewable Energy and the Environment, 2nd Ed. (CRC Press, 2015).
 A. Costa. "Geothermal Energy," Journal of College Science Teaching 4, 221 (1975).
 P. Smillie, "Induced Seismicity," Physics 240, Stanford University, Winter 2010.
 A. Wilson, "Imperial Valley Geothermal Energy," Physics 240, Stanford University, Fall 2010.
 B. Crowe, "Geothermal Energy," Physics 240, Stanford University, Fall 2012.
 Z. Yan, "Binary Power Plants," Physics 240, Stanford University, Fall 2011.