Why is geothermal energy considered a renewable resource?

Is Geothermal Renewable or Nonrenewable?

Many people are confused about whether Geothermal is renewable or nonrenewable as a source of energy. I am going to explain what is a geothermal resource and clear up the confusion when people pose the question – is geothermal renewable or nonrenewable?

Typically, when someone asks – is geothermal energy renewable, my first response would be – geothermal is indeed a renewable and sustainable energy source. But before I go into the explanation of why is geothermal energy considered a renewable resource I will first describe the meaning of the terms ‘Renewable’ and ‘Nonrenewable’ with reference to the energy sources.

What are renewable and nonrenewable resources?

Renewable energy is a term that speaks for itself. Renewable energy source refers to an energy source that is provided naturally by nature and will not run out eventually. This source of energy is replenished naturally within a reasonable length of time on a human timescale at a faster rate than they are consumed.

Examples of renewable energy sources are sunlight, geothermal heat, wind, tides, water, and various forms of biomass.

On the other hand, nonrenewable energy sources refer to energy sources that are not readily replenished naturally at a quick enough pace to keep up with their human consumption.

Fossil fuels which are nonrenewable, are thought to have been formed from the buried remains of plants and animals that lived millions of years ago. These resources are consumed by us much faster than nature can create them. Eventually, they will be exhausted altogether sooner or later and hence we cannot sustain our reliance on them indefinitely. Examples of nonrenewable energy sources are coal, oil, natural gas, and uranium.

Now that it is explained the meaning of the terms ‘renewable’ and ‘nonrenewable’ energy sources, it would be easier to answer the query – is geothermal renewable or nonrenewable?

Now, let’s first look into what is geothermal energy and how is geothermal energy produced, which would also help to understand why is geothermal energy renewable.

 What is geothermal energy?

The term Geothermal originates from two Greek words ‘GEO’ and ‘THERM’. The Greek word ‘Geo’ meant the earth while the word ‘Therm’ meant heat.  Geothermal energy is defined as the Thermal energy derived from heat, which is stored in the core of the Earth.

How is geothermal energy produced?

‘Geothermal’ literally means ‘Earth’s heat. The temperature of Earth’s core is estimated to be 5,500 degrees centigrade – about as hot as the surface of the sun. The earth has retained a huge amount of the heat energy that was generated during the formation of the planet. In addition, heat is continuously produced by the decay of radioactive elements within the earth. Thus geothermal energy is produced from a source that has almost an unlimited amount of heat generated from the core of the earth. The energy produced from Earth’s heat is sustainable and a clean resource that can be tapped by many countries around the world located in geologically favorable places.

How does geothermal work?

Let’s now see how does geothermal work.

The center of the earth which lies almost 4,000 miles beneath its surface is so hot that it is in a molten state. The heat from the earth’s core radiates outwards and heats up the outer layers of rock called the ‘Mantle’. When the rocks in the outermost shell of the earth, made of the earth’s crust and upper part of the Mantle melt at extremely high temperatures, this molten rock is called ‘Magma’. The temperature of Magma usually falls somewhere between 700 and 1300 degrees Celsius. Magma (molten rock) may come quite close to the surface of the earth. When Magma comes close to the surface it transfers heat to the groundwater that is found trapped in porous rock or running along fractured rock surfaces.

A usable form of geothermal energy is thus created under the earth’s surface. Some of this superheated water rises back to the surface of the earth where it emerges as hot springs or even geysers and steam vents. Sometimes the hot water becomes trapped below the surface as a geothermal reservoir. By drilling boreholes into these geothermal reservoirs the hot water and steam are piped up which can then be used directly to heat our homes and businesses or to generate electricity. Many countries have developed various methods of tapping into these geothermal energy sources.

Is geothermal renewable or nonrenewable?

From the explanation given above about how is geothermal energy produced and how does geothermal energy work, there should not be any confusion in deriving the logical answer to the query – is geothermal renewable or nonrenewable? The reasons given below would further show why is geothermal energy renewable.

Why is geothermal energy considered a renewable resource?

For an energy source to be reckoned as renewable the following three main criteria are required to be fulfilled:

1. The energy source is provided by nature;

2. The source is sustainable and will not run out eventually;

3. The energy source will be replenished naturally within a reasonable length of time;

As already explained, geothermal energy comes from the heat produced within the earth. An unlimited amount of heat is continuously produced naturally in the earth’s core by the slow decay of radioactive particles inside the earth. Thus the energy source is provided by the nature.

Now regarding sustainability. Why geothermal energy is also sustainable and will not run out eventually is explained below.

As mentioned earlier, the Earth has retained a huge amount of the heat energy that was generated during the formation of the planet. In addition, heat is continuously produced by the decay of radioactive elements within the Earth. As already explained geothermal energy harnesses energy from Magma, the earth’s molten rock, which continuously produces heat at a constant rate and this heat is not going to exhaust if re-used multiple times since it is generated from the core of the earth. At any one geothermal field, however, the temperature of the geothermal reservoir or the water levels or pressure in the reservoir may decrease over time as fluids are produced and energy is extracted. However, the volume of water taken out can be re-injected to maintain pressure, making it a sustainable energy source.

Thus, Geothermal energy can be re-used multiple times as it will be replenished naturally within a reasonable length of time at a faster rate than humans use them today.

From the explanations above it would be evident that geothermal energy fulfills all three decisive factors, for being reckoned as renewable. Hence it should not be difficult to understand why is geothermal energy considered a renewable resource.

You may also like to read this post: How does geothermal heating and cooling work?

Frequently asked questions

Now that I have explained in detail the real answer to the question – is geothermal renewable or nonrenewable, I will also address some of the related questions often asked by people:

What is geothermal energy used for?

Some applications of Geothermal energy use the constant temperature near the surface of the earth, while others use the underground reservoirs of steam and hot water by drilling into the earth. There are three main uses of geothermal energy:

1. Direct use: The hot water from the reservoirs located near the surface of the earth can be used directly for heating homes and offices. Hot water near the earth’s surface is piped into the buildings for heating purposes;

2. Use for Electricity generation: The underground reservoirs of steam and hot water can be used to generate electricity. Geothermal power plants are generally built within a mile or two of the locations of geothermal reservoirs;

3. Use in Geothermal heat pumps: Geothermal heat pumps use the constant temperature near the surface of the earth for heating and cooling of buildings. The heat pumps transfer heat from the ground (or water) into the buildings during the winter and reverse the process in the summer;

Can geothermal energy run out?

Although at face value, geothermal energy is considered a sustainable energy source, it is also true that changes in the underlying structure of the earth’s crust may cause geothermal wells to go dry and stop producing heat. Such possibility of local depletion of the energy source is something that we have absolutely no control over.

What country uses the most geothermal energy?

Geothermal energy is produced in more than 20 countries. The United States is the world’s largest producer of this energy. Most of the geothermal power plants in the United States are situated in western states and California generates the most electricity from geothermal energy.

How deep is a typical geothermal well?

The depth of Geothermal Wells is typically anywhere between 150 feet to 400 feet.

Is geothermal bad for the environment?

Geothermal power plants do not burn fuel to generate electricity and hence emit low air pollutants. These power plants emit much less carbon dioxide and sulfur compounds than fossil fuel plants of similar size.

You may also like to read: Pros and cons of geothermal energy

Conclusion

 When someone asks – is geothermal renewable or nonrenewable, it is clear from the explanation above that geothermal is a source of energy that is replenished by nature continuously and is not going to run out eventually. Hence, there should not be any difficulty to understand why is geothermal energy considered a renewable resource.  

However, while answering whether geothermal is renewable or nonrenewable, one point needs to be kept in mind things aren’t always the same as they may seem. As already mentioned, a productive geothermal well that is working perfectly today may go dry over time (in 10 or 20 years) and stop producing heat due to changes in the underlying structure of the earth’s crust. Over time, it is, therefore, commonly necessary to drill additional wells in order to maintain energy production as temperatures and/or reservoir fluid pressures decline. The geo-Sciences group is, therefore always in the search of new areas of possible sources of geothermal heat.

It is hoped that after going through all the facts about the geothermal energy sources discussed in the post there should not be any confusion in answering the question – is geothermal energy renewable ?