What is Geothermal Energy?

In the modern day, most people prioritize comfort and efficiency in their homes. How people heat and cool their homes determines the efficient realization of those priorities. A 5600 square foot home, for example, can explode your energy bills if cooling and heating systems are not efficient. The use of conventional electricity for heating and cooling greatly contributes to spike in energy bills. Conventional electricity is generated using fossil fuels such as coal and oil. With these fossil fuel sources running dangerously low, one source that humans have barely exploited, called geothermal energy, could provide attractive possibilities for bridging that gap and saving you massive energy costs. Geothermal systems take advantage of the natural warmth of the earth to heat and cool your home.

Geothermal energy is energy harvested from the heat found deep beneath the surface of the earth. The internal heat of the earth forms as a result of radioactive decay of minerals and consistent heat loss from the original earth formation. It’s is a clean and renewable form of energy because it’s infinite and doesn’t contribute to any greenhouse gas emission.


Energy inside the earth is never going to deplete and will remain as a source of heat, for millions and millions of years and we can harness that energy that is going to be cheaper and can help us to reduce our dependence on fossil fuels and global warming and public health issues that result from their use.

How Geothermal Energy Works?

The core found beneath the earth’s crust harbors a lot of heat. The deeper you go underneath the surface of the earth, the hotter it becomes. The core, which is approximately 6, 437 kilometers or 4,000 miles below the surface of the earth, can achieve temperatures of about 4200 degree Celsius or 7,600 degrees Fahrenheit. A portion of that heat emanated from the earth formation process approximately 4 billion years ago.

The remaining heat stems from continuous decomposition of radioactive materials underneath the earth. The heat found inside the core of the earth is so extreme that it melts rocks found nearby. The melted rock is called magma. Since magma is less dense than rocks wrapping around it, it’s forced up the surface of the earth. On some instances, the pressure inside the core forces magma out through vents, erupting out to the surface, a phenomenon known as volcanic eruption. However, in most instances, magma doesn’t come out of the earth’s crust. Instead, it heats rocks nearby, plus the water trapped within these rocks.

In some instances, the heating of water causes pressure to build up inside and forces the water to escape through vents in the earth culminating into pools of hot water commonly referred to as hot springs or ruptures of steam and hot water, commonly known as Geysers. Heated water that remains under the earth surface form pools known as geothermal reservoirs.

To get that heat, water is pumped down an “injection well”. Then it filters through the cracks in the rocks where they are at a high temperature. The water then returns via the “recovery well” under pressure in the form of steam. That steam is captured and is used to drive electric generators.

To produce geothermal energy, the hot water from the geothermal reservoir must be tapped. There are three techniques used to tap this hot water:

  1. Direct Geothermal energy

This technique is used in locations where geothermal reservoirs and hot springs are in proximity to the surface of the earth. Vents are drilled from the ground to the geothermal reservoir and the hot water pumped directly to homes and buildings for heating purposes. The hot water is pumped via a heat exchanger that transmits the heat from the hot water into the home’s heating system. The used water is then allowed to flow back into the geothermal reservoir to be reheated, and the cycle continues.

  1. Geothermal heat pump

A geothermal heat pump is sometimes called ground source heat pump. It’s a central cooling and heating system, which conveys heat to and from the ground. It leverages the earth as a heat source during winter months and a heat sink during summer months.

Ideally, geothermal heat pump works a lot like the traditional heat pump. It utilizes high-pressure refrigerant to harness and transfer heat in and out of the house. The only difference is that a traditional heat pump captures the heat and releases it to the atmosphere. A geothermal heat pump conveys heat into and out of the building via long loops of pipe filled with liquid buried under the ground. An electric compressor and heat exchanger installed in the building sucks up the heat from the pipes and delivers it throughout the building through a duct system. The geothermal heat pump works exactly the opposite during summer. The pipes suck heat away from the building and transfer it to the ground for absorption.

  1. Geothermal power plant

Geothermal power plants generally harness the heat underneath the earth’s crust and use it to generate electricity. There are three kinds of geothermal power plants:

  • Dry steam

Here, hot steam is harnessed directly from geothermal reservoirs and transmitted to geothermal power plant where it turns a turbine. The turbine then triggers a generator to produce electricity.

  • Flash steam

Here, water at a temperature of 148 to 371 degrees Celsius is sucked up from the geothermal reservoir through drilled down pipes. Some of the water is converted to steam and directed to spin turbines that trigger a generator to produce electricity. The steam is then allowed to cool off and eventually turns to water. The water is directed back to the geothermal reservoir to heat up and continue the cycle.

  • Binary cycle

Binary cycle plants use moderately hot water. The water is transferred via a heat exchanger. In the exchanger, the heat of the water is conveyed to a liquid, like isobutene, which boils at a comparatively lower temperature than water. When the liquid is subjected to heat, it converts to steam. The steam is directed to turn a turbine, which spooks a generator to produce electricity.

How much geothermal energy can be useful depends on several factors for e.g.: location, how hot the water gets, the rocks inside the earth and amount of water pumped into the area. If the rocks are not hot enough or cool down naturally this presents a problem for geothermal power stations.

Examples of geothermal energy


A Geyser is a hot spring where water sporadically boils, sending a long column of steam and water into the atmosphere. It’s quite an amazing spectacle. Nonetheless, some Geysers result in eruptions that burst thousands if not hundreds of liters of hot water up hundreds of feet into the atmosphere. The world’s famous Geyser is the Old Faithful situated in Yellowstone National Park in the United States. It’s known to erupt each 60 to 90 minutes. For a Geyser to occur, the following conditions must be present:

  • Scorching rocks underneath the earth’s surface
  • Ground water source
  • A subsurface water reservoir
  • Vents that enable water to be conveyed to the surface

Geysers are extremely rare phenomenon. United States, Russia, Chile, New Zealand and Iceland are countries that harbor active Geysers.

Hot Springs

Hot springs are springs that come about due to the appearance of geothermally heated groundwater that comes out from the earth’s crust. Geothermal hot springs occur at different locations in the earth’s crust. Some hot springs contain water at a perfect temperature for bathing. Others are so hot that anyone trying to bath in them can sustain severe burns or die.


A fumarole is a vent from which steam and gasses escape into the atmosphere. The vent can be utilized to tap geothermal energy. Fumaroles may form along small cracks or long fissures, in chaotic fields or clusters. They may also form on lava flow surfaces and huge deposits of pyroclastic flows. They may occur for decades or even centuries if they form on top of a constant heat source like active magma. They might well disappear within weeks or months if they form on top of a fresh volcanic deposit that quickly cools. Their temperature range from 70 to 100 degrees Celsius.

The only concern about geothermal energy is that it releases hydrogen sulfide. Hydrogen sulfide is a kind of gas that smells a lot like rotten egg. Otherwise, the advantages of geothermal energy are simply overwhelming. It’s clean, green, renewable, relatively inexpensive, and cuts backs on the use of fossils fuels, which contribute to massive pollution and global warming.

References: ucsusa , howstuffworks
Image credit: pixabay


Rinkesh is passionate about clean and green energy. He is running this site since 2009 and writes on various environmental and renewable energy related topics. He lives a green lifestyle and is often looking for ways to improve the environment around him.