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| Fig. 1: The layout of a Dry Steam Power Plant. (Source: Wikimedia Commons) |
Geothermal Energy is a renewable energy source that utilizes the heat in the Earth's crust to generate energy. A number of countries use Geothermal energy to power their homes. [1] The three main methods that geothermal power plants use to extract energy are flash, dry steam, and binary. [2] Power plants that use the flash method pump hot water at high pressure from the ground and then expose it to cold water at a lower pressure. This creates a massive amount of steam which is used to turn the turbines. [2] Dry steam method captures the steam dissipating directly from the cracks in the ground and then use the vapor to turn the turbines (see Fig. 1). [2] Finally, binary plants take the hot water from the ground and expose it to a fluid with a lower boiling point than water. The mixing process between the hot water and the second fluid causes the secondary fluid to evaporate and then the steam is used to powers the turbines. [2]
Geothermal energy has a few major drawbacks to it. To begin with, it can cause land subsidence. When geothermal plants withdraw fluids from permeable rocks, this leads to a decrease in pressure of the rocks and causes land subsidence. There is no way to prevent land subsidence in permeated rocks because of the pressure change. However, if the water was drawn from an under reservoirs we can attempt to refill it with water to prevent the subsidence. Unfortunately, this may lead to tectonic stress which inter leads to the second major drawback seismic activity. This constant change in pressure applied to the rocks can imbalance the crust and lead to an increase in seismic activity. [3] Finally, geothermal plants produce toxic materials true by extracting steam and hot water from the Earth's crust. Geothermal fluids have been found to contain low concentrations of hydrogen sulfide, arsenic, mercury, lead, zinc, boron, and sulfur. [4] Despite the low concentration of these toxic gases with excessive production they can start accumulating and damaging the environment.
Obviously, the biggest benefits of geothermal energy are its renewability and sustainability. Sadly only a small part of it is being used, in 2015 we only utilize 6.5 percents of Earth's geothermal energy. [2] With advances in technology and money being invested to research simpler and more efficient ways to generate geothermal energy, we will see an increase in this number. Earth has an enormous potential to generate energy, we just need to learn how to harvest it. In addition, to being renewability and sustainability geothermal energy can produce free heating and hot water. In countries like Norway and Island, geothermal power plans also generate free heating and hot water for the houses. They use the hot water from the ground and directly send it the houses. This eliminates the need to use electricity to heat the water which in turn lowers the price of hot water, heating, and electricity in those countries. [5]
Geothermal energy will play a major roll in moving from fossil fuel to green renewable energy sources. Whit further advances in technology we will be able to collect even more energy from the Earth and be more efficient. What is more, these advances might be able to eliminate some of the draws back suck as toxic materials, subsidence, and seismic activity. Geothermal energy can be the key to a green and sustainable Earth in the future.
© Lukas Kisunas. The author warrants that the work is the author's own and that Stanford University provided no input other than typesetting and referencing guidelines. The author grants permission to copy, distribute and display this work in unaltered form, with attribution to the author, for non-commercial purposes only. All other rights, including commercial rights, are reserved to the author.
[1] G. Sivesind, "Geothermal Energy in Iceland," Physics 240, Stanford University, Fall 2016.
[2] B. Matek, "2015 Annual U.S. and Global Geothermal Power Production Report," Geothermal Energy Association, February 2015.
[3] P. Smillie, "Induced Seismicity," Physics 240, Stanford University, Fall 2010.
[4] E. Barbier, "Geothermal Energy Technology and Current Status: an Overview," Renew. Sustain. Energy Rev. 6, 3 (2002).
[5] B. Mikkelsen, "Geothermal Energy Benefits," Physics 240, Stanford University, Fall 2015.
