Understanding Geothermal Energy

by | Educational, Energy Topics

Geothermal energy couldn’t have a more fitting name. A combination of the words geo” (earth) and “thermal” (heat), it quite literally means heat energy from the earth. 

Although this form of energy is geographically dependent, recent technological advancements and modern geothermal systems are allowing this renewable energy resource to become available in different parts of the world. 

What Is Geothermal Energy and How Does It Work? 

Geothermal energy refers to the underground reservoirs of steam and hot water that can be tapped to generate geothermal electricity or to heat and cool buildings directly. 

The term geothermal has been in use since 1875, but the concept of using this energy for tasks isn’t new.  

Geothermal energy has existed for billions of years, but it was only about 10,000 years ago that Native Americans used geothermal energy to cook food. And let’s not forget how Greeks and Romans bathed in water heated by hot springs too.  

To know how geothermal energy works, you first need to know the structure of the Earth. 

Earth has multiple layers that get hotter as you go towards its core (the innermost layer). Earth’s core is 1,800 miles deep and has a temperature of 10,800 degrees Fahrenheit. Yes, that’s as hot as the sun’s surface! 

Another interesting thing here is you don’t need to dig very deep to feel the Earth’s heat. At just 0.001 miles (two meters) below the Earth’s surface, you get a consistent temperature range between 52-53 degrees Fahrenheit. The Earth’s crust is 900-1,000 degrees Fahrenheit700 degrees Fahrenheit.  

In other words, even when the ground feels cool to the touch, it has valuable heat energy underneath. Innovative geothermal technologies can bring this heat to the surface and then convert it into electricity. 

To explain how geothermal energy works from a technical point of view, let’s consider things at the atomic level. 

Electrons revolve around the nucleus of an atom. But when you apply high pressure to the atom, the electrons start to move about quickly, crashing into each other. These constant crash-ins and faster movements end up generating thermal energy as heat.  

In the case of geothermal energy, the pressure applied to the atom is the actual heat created due to temperature rise, and the source of the heat is the Earth’s core. 

Where Does Geothermal Energy Come From? How Is It Generated? 

Geothermal Energy | Origins and How it is Generate imagesource

Geothermal energy comes from the center of the Earth.  

Earth’s core consists of two parts: the inner core and the outer core. While the former is solid iron, the latter is molten iron. Encompassing the core is the mantle, which comprises magma and rocks. Finally, the topmost layer is the crust.  

The heat created in the core is also the result of radioactive decay over billions of years.  

The geothermal resources of our Earth have four main categories: hydrothermal, geo-pressurized, hot dry rock, and magma. All four of them require water and heat and are in developmental stages 

Hot springs, geysers, steam vents, mud pots, and hydrothermal vents are common sources of geothermal energy. Companies have started capturing this geothermal energy through geothermal power plants and geothermal heat pumps that dig deeper into the bowels of the Earth for energy use.  

How Is Geothermal Energy Used and What Is It Used For? 

Geothermal Energy | How and when it is used - smoking energy imagesource

From cooking to heating to electricity production, geothermal energy has a wide range of applications.  

Several countries across the globe have different ways of tapping into geothermal energy – mostly due to the different sources of geothermal energy in different areas of the world. This also affects the overall cost of tapping into this energy.  

For instance, in countries like the United States, geothermal energy has to be drilled, making it more expensive. But in other countries like Iceland, there are abundant geothermal resources, such as hot springs and geysers. Not only does this eliminate the need for any drilling, but it also reduces costs. 

Geothermal heat pump systems can heat homes in the winter and cool them during the summer. These systems are dug into the ground in a way that allows them to make use of the constant temperature of the Earth‘s surface.  

The heat pump system extracts heat from buildings to lower room temperatures during summer and transfers it back to the comparatively cooler ground. Geothermal energy also helps grow plants in greenhouses or for piping geothermal hot water under sidewalks and roads to melt snow. 

This low-temperature form of energy is used for limited industrial production and running fisheries too. 

Moreover, the U.S. Department of Energy recently announced $25 million in funding to explore the potential of Enhanced Geothermal Systems or EGS. These systems aim to set up artificial geothermal reservoirs into dry cracks and gaps underground by injecting water. This will then create water-based heat resources to house a binary cycle power plant. 

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Where Is Geothermal Energy Being Used in the World? Where Was It First Used? 

The Italians built the world’s first geothermal energy plant in Larderello back in 1904 

Prince Piero Ginori Conti of Trevignano used the world’s first geothermal energy generator to power five lightbulbs in a dry steam field called Larderello. In 1913, the world would finally see a working geothermal power plant that powered the towns of Larderello and Volterra. 

Geothermal power generation for industrial processes happened later at the beginning of the 20th century in Tuscany, Italy. 

Although geothermal energy has been exploited for many years, it’s not as common as non-renewable energy sources like coal and natural gas, or renewable energy sources such as solar energy, wind energy, and hydro energy 

However, it’s still an industry that is growing slowly but steadily. Its capacity has increased by 27% in the last five years. This, in turn, helped to add 3.6 gigawatts or 3,600 megawatts of global electricity production. 

Back in 2015, the total worldwide geothermal energy capacity for direct use was about 73,290 megawatts thermal, using about 163,273 gigawatt hours per year. Also, geothermal fields run at about 95% efficiency, which is the highest for any renewable energy form. 

It’s common for geothermal plants to be located along a geological fault line. The United States is the global leader of geothermal energy production while Indonesia takes the second position. Other countries like Kenya, Turkey, the Philippines, New Zealand, Italy, and Iceland are also working on increasing their energy production capabilities. 

In the U.S., California and Nevada are the biggest geothermal energy producers at 71% and 23%, respectively. 

How Does a Geothermal Power Plant Work? 

Geothermal power plants are designed to produce electricity through hot water and steam by piping deep under the earth’s surface through underground wells.  

With several countries trying to tap into geothermal resources to create power, the smaller power generating facilities are quickly being set up all over the world. 

Here are the three main types of geothermal energy plants: 

Dry Steam Power Plants 

Accounting for nearly half of the installed geothermal power plants in the world, dry steam plants are the most common type. In this case, the hot steam from underground reservoirs is piped directly into turbines from geothermal reservoirs. The steam, in turn, helps power generators to generate electricity for households. 

After powering the turbines, the steam condenses into water and is piped back into the earth through an injection well. 

Flash Steam Power Plant 

The difference between flash steam plants and dry steam plants is instead of pumping steam, it pumps hot water at a high temperature from below the Earth to the surface.  

The tank has a much lower temperature, which causes the steam to turn into or “flash“ quickly into steam. Once the steam cools and condenses into water, it’s pumped back into the ground through an injection well. 

Binary Cycle Power Plant 

In a binary cycle power plant, the water or steam from below the Earth’s surface doesn’t come into direct contact with the turbines.  

Instead, water from geothermal reservoirs is pumped through a heat exchanger where another liquid, usually an organic compound with a lower boiling point than water, is heated. After the second liquid is heated into steam, it’s used to power the turbines that drive a generator. 

The hot water from the earth’s surface is recycled back into the earth through the injection well. The second liquid is then recycled through the turbine and back into the heat exchanger where it can be used again. 

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Is Geothermal Energy Renewable? Why Is It Considered a Renewable Energy Resource? 

Renewable Energy | Geothermal Energy - atom picturesource

Geothermal energy is renewable. The heat from the Earth’s core is almost unlimited when compared to non-renewable energy sources, so there’s no need to burn fossil fuels to extract geothermal energy.  

The fact that there are fewer harmful greenhouse gas emissions like carbon dioxide also makes geothermal energy highly sustainable.  

Keep in mind that CO2 isn’t created in large quantities during geothermal processes; it’s just natural gas present in rocks and water. 

Where Does the Heat for Geothermal Energy Come From? 

The heat for geothermal energy comes from the Earth’s core. Scientists predict the temperature to be between 5,000 to 11,000 degrees Fahrenheit, which is transferred to the molten outer core then to the mantle, which is the layer between the Earth’s core and crust. 

This heat reaches the crust (aka the Earth’s surface) where underground water channels and fissures touch the mantle, heating the water. It’s this heated water that companies tap into to provide the hot water or steam for creating geothermal energy. 

Where Is the World’s Largest Geothermal Field? 

With a capacity of 1570 megawatts, Geysers Geothermal Complex in the United States is the largest geothermal field in the world.  

The field is made up of 22 power plants spread over several miles in Northern California. It sits atop a deep chamber of molten rock, spanning over 30 square miles.  

It’s no wonder the United States has the highest geothermal capacity in the world. 

How Do Geothermal Wells Work? 

Similar to other wells, geothermal wells involve drilling holes into the Earth’s surface to extract the heat below.  

Geothermal wells are designed based on the type of geothermal system and how the well will be utilized. They involve the use of specialized drilling practices, which is then harnessed into spinning turbines for electricity generation. Sometimes, the heat from geothermal wells is directed to hot water tanks and homes to be used in a heating system. 

Geothermal Energy for the Win 

Because of climate change, the world is open to renewable energy resources more than ever. As it turns out, what’s old is new again: Geothermal energy has been around for billions of years, yet it’s one of today’s most promising options. It’s clean energy with higher energy efficiency. It can keep households warm with a reliable supply of electricity and help industries continue production without damaging the environment. 

Don’t forget to ask your energy supplier about this renewable energy source, and whether it can be a viable option to meet your personal and professional needs. 

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