What is Geothermal Energy?
Geothermal energy is natural heat extracted from the earth’s crust. The word “geothermal” comes from Greek . “Geo” means “earth” and “therme” means “heat”. The combination of “geo” means “earth” and “therme” means “heat”. The source of geothermal energy is mainly the heat energy inside the earth. There are two main sources of heat energy for the Earth: solar radiation and geothermal heat from the Earth’s interior (e.g., decay of radioactive elements). The heat of the earth also comes from the decay of radioactive elements inside the earth. We know that the earth contains extremely rich material resources, including radioactive substances such as uranium, thorium, and radium. These radioactive substances contain rich radioactive isotopes such as uranium, thorium, and potassium.
These radioactive isotopes will release a large amount of heat during the decay process to maintain the heat supply inside the earth. The decay cycle of radioactive substances is extremely long. The decay cycle of some substances is as long as 4-5 billion years, so these substances can continuously provide heat to the interior of the earth, so that it is still very hot after billions of years.
Also known as “geothermal gradient”. A parameter indicating the degree of uneven distribution of temperature within the Earth. Generally, the deeper the depth, the higher the temperature value, expressed as the number of degrees Celsius added per 100 meters of vertical depth. The value of the geothermal gradient varies from site to site and is usually (1-3) °C/hundred meters, being higher in volcanically active areas. Simply put, it’s the magnitude of temperature increase the deeper one digs underground. In most regions globally, the average geothermal gradient is within the range of 25-30°C per kilometer. This value is equivalent to the temperature rising by approximately 2.5-3°C for every 100 meters descended underground. For example, if the geothermal gradient in a certain place is 30°C/kilometer, then at a depth of 3000 meters underground, the temperature will be about 90°C higher than at the surface.
Geothermal resources are heat energy stored inside the earth; they can be used for power generation, heating, greenhouse cultivation, hot spring utilization, etc. Magma refers to a hot, viscous, molten material containing volatile components, mainly silicates. Magma mainly exists in the upper mantle layer of the Earth, which is a region hundreds of kilometers deep from the surface. Magma refers to molten or partially molten rock underground. When magma erupts to the surface, it is called lava.
The mantle lies beneath the crust, to a depth of about 2,900 km , and occupies 84% of the Earth’s volume. The amount of geothermal energy released naturally each year is equivalent to five times the global electricity consumption.
Advantages of Geothermal Energy
Geothermal energy , as a renewable energy source , has many advantages. Geothermal energy has the advantages of low carbon emissions and long-term stable supply, and is widely used in building heating, agricultural farming, hot spring facilities and industrial processes. Geothermal energy is basically a clean energy . Clean energy usually refers to energy with less pollution during production and use, mainly including nuclear energy, solar energy, geothermal energy , wind energy, etc.
Types and Applications of Geothermal Energy
Geothermal energy is a renewable energy source that can be widely used for heating, cooling and power generation. The following are some examples of geothermal energy applications:
- Geothermal Heating: Using the stable temperature of the ground, heat is transferred from the ground to the inside of a building through a geothermal heat exchanger to achieve heating. This method saves energy and reduces carbon emissions.
- Geothermal cooling: Similar to geothermal heating, geothermal energy can also be used for cooling. This method usually requires the use of absorption chillers or heat pump systems.
- Geothermal power generation: Geothermal energy can be converted into electricity through geothermal power plants. Geothermal power generation uses water vapor or hot water at high temperatures underground to drive a turbine to generate electricity.
- Spas and hot tubs: Groundwater in many areas is rich in thermal energy and these sources can be used for spas and hot tubs. This method not only provides people with recreation, but can also be used to treat symptoms such as rheumatism and muscle pain.
- Agricultural applications: Geothermal energy can be used for agricultural purposes, such as greenhouse farming. Geothermal energy can provide a temperature-stabilized environment to help plants grow.
In agriculture, especially in cold regions, the use of geothermal energy can significantly reduce the heating costs of greenhouses and improve their operational efficiency. In conclusion, geothermal energy should be very extensive and can provide a reliable source of energy for people’s life and work.
Low-Temperature Resources
Low-temperature geothermal refers to geothermal resources with a temperature greater than 25°C and less than 90°C . The efficiency of low-temperature waste heat power generation is about 5% to 15%, depending on the technology used, heat source temperature, heat source flow, and the performance of the power generation equipment.
Industrial Processing
Industrial processing: High temperature geothermal resources can provide thermal energy for industrial drying, food processing, etc.
District Heating
Heating: Geothermal heat can be used directly in district heating systems (e.g. heating network in Iceland).
Power Generation
Power generation: Geothermal energy is known to have direct application through steam or hot water driving a turbine to generate electricity.
Real-Life Examples of Geothermal Energy
Examples of Geothermal Energy Applications
Humans have been using geothermal energy for a long time, such as using hot springs for bathing, medical treatment, using underground hot water for heating, building greenhouses for crops, aquaculture, and drying grains.
1. Hot Spring Baths
In our town, there is an amazing place, the hot spring bath in town. This hot spring is a great example of the application of geothermal energy.
I remember one time, I went to the hot spring with some of my good friends. When we walked into the hot spring, we could smell the faint odor of sulfur, which was unique, but not unpleasant, like the unique scent of the earth. There are several pools of different temperatures in the bathhouse, and each pool is bubbling with hot air, just like the earth is happily spitting bubbles. We first came to a pool with a moderate temperature. Just put my feet in, wow, the warm feeling spread along the feet to the whole body, so comfortable that I couldn’t help but shout out, “Ouch, this is too good.” My friend Murphy also followed, “Yes, yes, I feel that the fatigue of the whole body has disappeared at once.” An older man heard us and said with a smile, “This is all due to the geothermal energy. The heat energy under the ground is drawn up and turned into hot springs, soaking in it is good for your body.”
Curious, we gathered around Uncle and asked him to tell us what this geothermal energy was all about. Uncle cleared his throat and began to speak: “You see, this geothermal energy is like a big furnace deep in the earth. Through a special pipeline, the thermal energy is led here, so that the water becomes hot, and it becomes a hot spring.” We nodded our heads as if we didn’t understand. At this time, another friend of mine, Andrew, suddenly said, “Will this geothermal energy run out one day?” Uncle waved his hand and said, “No, no, this geothermal energy can be abundant, just like the treasure of the earth, inexhaustible.” After hearing this, we all soaked in the hot springs with peace of mind.
I also found some interesting devices in the pool. There was a spout with water coming out all the time, and when the water hit my body, it was like a massage. I asked the staff next to me, “Is this also because of geothermal energy?” The staff smiled and said, “This is the use of geothermal energy heated water, through a special pressure device to make the water flow, so there is a massage effect.” After soaking in the hot springs, we all felt relaxed. This hot spring bath, relying on geothermal energy, gave us such a comfortable enjoyment. It is not only a place to take a bath, but also a real example of the application of geothermal energy, so that we can really feel the charm of geothermal energy.
2. Geothermal Greenhouses
To talk about the application of geothermal energy, I have to tell you about the geothermal greenhouse at my grandfather’s house. When I was a child, I often went to my grandfather’s house to play. Grandpa’s house is in the countryside, where there is a large geothermal temperature room. This greenhouse is a local treasure.
One winter, I followed my grandfather to help in the greenhouse. Just as I walked into the greenhouse, I felt a rush of heat. It was so warm inside, a completely different world from the icy and snowy world outside. The greenhouse was full of all kinds of vegetables: lush green vegetables, bright red tomatoes, and long cucumbers.
Geothermal greenhouses are important for food security and sustainability, especially in high-latitude or mountainous regions where traditional heating is expensive or unsustainable. By using geothermal heat, farmers can keep crops growing all winter, increasing yields and improving local diets.
The Future of Geothermal Energy
With continuous research and increasing climate concerns, more attention is being paid to geothermal energy as a stable, green, and reliable source. It can support renewable transitions worldwide, with a vast reserve literally beneath our feet.
Advances in drilling, heat-pump technologies, and waste heat recovery are gradually increasing efficiency and reducing costs. From powering entire cities to warming a small rural greenhouse or providing a therapeutic soak in a hot spring, the future applications of geothermal energy are only limited by our imagination and our willingness to invest in the earth’s own warmth.
In summary, geothermal energy is a clean, renewable, and stable energy source rooted in Earth’s internal heat. Its applications—from power plants and heating systems to spas and agriculture—touch lives the world over, and local examples like hot spring baths and greenhouses show us the direct benefits of harnessing this treasure beneath our feet.
