What is Geothermal Energy?

Geothermal energy is the thermal energy that is generated by, and stored within, the Earth itself. In fact, it is the primary source of energy that determines the mean temperature of all matter on Earth. The innermost core of the Earth is a fairly heated, but solid, ball of iron and nickel. The outer core, however, is the definition of fire and brimstone. At its hottest points, this outer core has been measured at nearly 8,000 degrees Celsius. This extreme heat fuels a process that moves all of the matter resting on top of this liquid fire, from the mantle, to the inner crust, and then the outer crust, upon which rests the continents that we live upon. The conductive energy that is produced during this process is monumental in its conception. Furthermore, there are locations all over the Earth, like steam vents at the bottom of an ocean bead, or a heated water geyser above a magma hotspot, where this energy can be most effectively harvested. Additionally, given the appropriate technology, which is in development, combined with the political will which, in most places unfortunately, is not, this form of energy could be harvested in perpetuity. If humanity were to die off, any new civilizations that evolved would have this form of energy during the full length of their development. Also, so long as the Earth’s core remained active, this source of energy has the potential to outlast all others.

How is Geothermal Energy Produced?

To produce geothermal generated electricity, wells, sometimes a mile / 1.6 kilometers deep or more, are drilled into underground reservoirs to tap steam and very hot water that drive turbines linked to electricity generators. The first geothermally generated electricity was produced in Larderello, Italy, in 1904. There are three types of geothermal power plants. They are dry steam, flash steam, and binary steam. Dry steam, the oldest geothermal technology, takes steam out of fractures in the ground and uses it to directly drive a turbine. Flash plants pull deep, high-pressure hot water into cooler, low-pressure water. The steam that results from this process is used to drive the turbine. In binary plants, the hot water is passed by a secondary fluid with a much lower boiling point than water. This causes the secondary fluid to turn to vapor, which then drives a turbine. Most geothermal power plants in the future will be binary plants. Geothermal energy is generated in over twenty countries, at present. However, more countries are investing in this form of energy production every year. The United States is the world’s largest producer, and the largest geothermal development in the world is “The Geysers” north of San Francisco in California. In Iceland, many of the buildings and even swimming pools are heated with geothermal hot water. Iceland has at least twenty active volcanoes and many hot springs and geysers, all of which can be potentially converted in energy production facilities.

Dry Steam Power Plant


Flash Steam Power Plant


Binary Steam Power Plant


Other Uses of Geothermal Energy

The word “geothermal” is derived from two Greek words: “geo” which means “Earth” and “thermal” which means “heat.” Geothermal energy has been used for many years in various parts of the world for cooking and heating. Since time immemorial, humankind has utilized the geothermal energy that flows freely from underground reservoirs to the Earth’s surface. For instance, geothermal water was used by the Romans to treat different kinds of diseases, to heat the city of Pompeii, and to keep their famous baths warm. For more than 10,000 years, the indigenous peoples of North America used geothermal water for cooking, as well as for medicinal purposes. Geothermal springs have been used for washing and bathing in Iceland. Modern uses of geothermal energy include heating and cooling of buildings, as well as, as has been mentioned, the production of electricity. This is achieved through the use of geothermal pumps that make use of shallow resources.

Potential of Geothermal Energy

Because of the internal heat produced by the Earth’s core, the Earth’s surface heat flow averages 82 mW/m2 which amounts to a total heat of about 42 million megawatts. The total heat content of the Earth is of the order of 12.6 x 1024 MJ, and that of the crust, the order of 5.4 x 1021 MJ. With present technology, it is considered possible to produce up to 8.3% of the total world’s electricity with geothermal resources, supplying 17% of the world population. As of March of 2016, the Geothermal Energy Association reported that a total of 18 new geothermal power plants came online in 2015, adding about 313 MW of new capacity to electricity grids globally. This makes for a global total of 13.3 GW in total electricity production. By 2021, global production is expected to reach 18.4 GW. It is estimated that if the market sustains its present growth, production will have reached 32 GW by the early part of 2030s. As refinements in conversion technologies increase its feasibility, geothermal energy will come to take on a more prominent role in human energy production. As it can be tapped in various regions around the world, on land and in the ocean, geothermal energy has the potential to be an infinite source of electrical power.