Geothermal energy is a trending term in today’s go-green movement. Everyone wants to be energy-conscious and carbon negative. And, what could be a better option than geothermal technology if you leave fewer carbon footprints?

As appealing as it sounds, geothermal energy is yet to gain popularity in terms of usage. Many people are still unaware of its source and implications for the future generation.

Earth’s core is the ultimate source of geothermal energy. It is the intense heat generated inside the earth. In Greek, “Geo” means earth, and “thermal” means heat. As simple as that!

But how do the hot rocks and molten metals produce enough energy to power an entire house? The process is lengthy; it takes hundreds of years for geothermal energy to form inside the earth.

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Understanding the science behind the source of geothermal energy

The hottest part of our planet, the core, is around 1800 miles below the earth’s surface. The core’s heat results from friction and gravitational pull generated during the earth’s formation. That would be around 4 billion years ago!

Radioactive decay is a recurring process in the core responsible for a significant portion of the heat. The temperature of the earth’s core is above 9,000 degrees Fahrenheit. Henceforth, this immense heat is always escaping outwards.

In due process, various geological matters such as water, rocks, and gases get heated up. As a result, the temperature from the earth’s surface to the core is always rising. This temperature change is called a geothermal gradient.

The geothermal gradient is approximately 1 degree Fahrenheit per 77 feet of depth (25 degrees Celsius per 1 kilometer). When the underground rocks heat to about 1,300-2,400 degrees Fahrenheit (700-1,300 degrees Celsius), they convert into magma.

As the magma flows around the earth’s mantle and lower crust, they heat the nearby rocks and underground aquifers. Hereafter, hot water is released through hot springs, steam exhausts, mud pots, underwater hydrothermal outlets, and geysers.

Now that’s our various sources of geothermal energy. The extreme heat produced by these sources can be taken and used directly. Or we can also use the steam generated in due process to generate electricity.

What is dry geothermal heat?

The heat energy produced by the earth’s core doesn’t always bubble out as magma, hot water, or steam. Many times, it remains under the lower crust and mantle. They come outside on the crust at an extremely slow pace forming outer heat pockets.

These heat pockets are known as dry geothermal heat. The energy stored can be accessed by drilling holes into the hot rocks and continuous water injection to generate superheated steam.

Dry-steam power plants

Dry Steam Power Plant
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Dry-steam power plants are the oldest power plants that utilize geothermal technology to generate energy. They use the underground source of steam. The steam is focused directly into the fuel turbines, which generate electricity.

Flash-steam power plants

Flash Steam Power Plant
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These are the naturally present sources of underground boiling water and steam. Water above 360 degrees Fahrenheit (182 degrees Celsius) is propelled into a low-pressure area.

The vapor that evaporates during the process operates the turbine and generates electricity. The residual water is then rushed into another reservoir to produce additional energy.

Flash-steam power plants are the most common forms of geothermal power plants as they are easily accessible, especially in volcanically active locations such as Iceland and the Philippines.

Can we source geothermal energy from all parts of the world?

Low-temperature geothermal energy can be accessed from anywhere on the earth and used instantly as a reliable energy source. 

We can source the energy from low-temperature heat pockets with around 301 degrees Fahrenheit (150 degrees Celsius) temperature. They are located a few feet below the earth’s surface.

Such low-temperature geothermal energies are commonly used in heating homes and industrial processes. Although it works best when used for heating purposes, it can also generate some electricity.

Geothermal Heat Pumps can outsource geothermal energy from any part of the world!

Now isn’t that good news for those of us residing in low volcanic activity locations?

Geothermal Heat Pumps (GHPs) make the best use of the earth’s heat. They don’t have to be drilled into hot rocks to reach the energy source. Depending on the location, they are plugged into the earth’s surface about 10 to 300 feet underground.

A continuous loop of pipe is formed by connecting it to a GHP. The slinky loop circles underground and above the ground throughout a building. Hence, it meets the heating requirement of an entire apartment, including the parking lot!

Water or some antifreeze liquid moves through the pipe. During the winter, the fluid inside this continuous pipe absorbs underground geothermal heat. They carry warmth throughout the living spaces and are also used to heat water for daily use.

And during the summer season, the commercial GPH system works in the reverse method. The fluid absorbs warmth from the heat inside the apartments and transports it underground to be chilled.

Geothermal Heat Pump
Geothermal Heat Pump (source)

Various countries have started taking advantage of geothermal energy. They have been tapping into geothermal energy naturally from volcanic locations or drilling into hot rocks. The latter comes at a higher cost.

How is geothermal energy being sourced across the globe?

At present, over 20 countries are rigorously generating geothermal energy. And did you know that the United States of America is the largest producer? Northern San Francisco, California, has the most extensive geothermal development globally and is called The Geysers.

The Philippines lies just over a tectonically active zone known as the “Ring of Fire.” It is unsurprising that they own the biggest single geothermal power plant, a flash-steam power plant.

Natural geysers and steam outlets have been heating the homes and farms of New Zealanders. They have also used dry geothermal heat to feed livestock and dry timber.

Iceland has over 20 active volcanoes, and the country uses geothermally heated waters in its swimming pools. After all, who doesn’t love a warm pool, right?

Lastly, the earth’s core is an endless supply of energy; we must learn and effectively tap into this green energy.

(Last Updated on December 1, 2023 by Sadrish Dabadi)

Shradha Bhatta holds a Bachelors’s Degree in Social Work along with a Post-graduate degree in Project Management from Georgian College in Canada. Shradha enjoys writing on a variety of topics and takes pleasure in discovering new ideas. She likes traveling and spending time with nature. She is a very people-person who loves talking about climate change and alerting people to go green!