Having been structured 4.6 billion years ago from the clashing of giant disc-shaped clouds of material, the Earth has been forming ever since, with a core that is due to completely solidify in several billion years. While other cosmic events that will likely mark the end of the planet prior to this time, the overall freezing of the core would cause the Earth to completely harden and turn into a geologically dead rock in the solar system. Fortunately, until this time comes, the inside of the planet is actually pushing heat onto the surface, something that we can make use of as a clean source of energy. Geothermal energy is method of electric power generation that is relatively less common amongst different conventional and renewable forms of energy, but it makes use of the energy given to all of us throughout the globe.
Geothermal energy is different from other types of renewables, since it is a constant source of energy, as opposed to solar and wind, which are relatively variable. Additionally, it uses geologic concepts that would not be pertinent when working with energy sources such as solar and wind. ASTM E957-03(2011)E1: Standard Terminology Relating to Geothermal Energy
|Bárðarbunga, a volcano in Iceland|
Geothermal energy makes use of the heat maintained in the upper 10 feet of the Earth’s surface by using it to heat and cool buildings with a heat pump, an air delivery system, and a heat exchanger. This system is also able to heat water by removing air from indoors during the summer to keep the home cool. The guidelines addressed in ASTM E947-83(2015): Standard Specification for Sampling Single-Phase Geothermal Liquid or Steam for Purposes of Chemical Analysis allow for testing of the liquid or steam used in heating and cooling systems to ensure that it properly makes use of the energy it takes from the planet. Geothermal energy is also used in power plants to generate electricity by having the steam formed from hot water found a few miles below the Earth’s surface rotate a turbine to power a generator.
The tectonic plates that make up the mantle of the Earth are constantly shifting because of the continuous activity of the planet, in which radioactive decay from the heated core creates convection currents that drive continental drift. This movement is responsible for the formation and separation of mountains and continents at plate boundaries, but it also creates volcanic activity, from either the convergence or divergence of two plate boundaries. Volcanic activity is a prime source of geothermal energy, since it involves concentrating molten and liquid rock that comes from below the Earth’s surface and occasionally releasing it out of the inner Earth through lava. There is a very significant amount of energy coming off this material, which can be used to generate steam to power a generator, or to directly heat buildings. This is incredibly useful for certain places, particularly Iceland, a hotbed for volcanic activity due to its presence on the diverging North American and Eurasian plates. This fault line cuts directly through the center of the island-nation, making it so that 30 percent of the country’s electricity comes from geothermal. This, in combination with the large amount of hydropower used in the area, makes Iceland’s sources of energy 99 percent renewable.
While not every square foot of inhabitable land on the Earth has the potential to harvest the same level of geothermal energy as places like Iceland, many areas can still make some use of this continuous source of clean energy to accommodate their electricity and heating needs.