Geothermal Energy: Countries worldwide are much more aware of the damages that the rampant use of fossil fuel-based sources of energy are causing. Therefore, there is an urgent need to replace our existing sources of energy which consist of non-renewable sources like coal and petroleum. As the search for alternate and cleaner energy sources continues, one energy source that has emerged as a game-changer is Geothermal energy. The word “Geothermal” is composed of two words- ‘Geo’ and ‘Thermal.’ Geo means Earth while Thermal means heat. Thus, the word Geothermal tells us about the heat stored within the surface of the Earth.

The thermal energy generated and stored in the Earth is Geothermal energy. Geothermal heat energy can be recovered and exploited for human use, and it is available anywhere on Earth’s surface. The estimated energy that can be recovered and utilised on the surface is \(4.5 \times {10^6}\) exajoules, or about \(1.4 \times {10^6}\) terawatt-years, This is roughly equal to the three times the world’s annual consumption of all types of energy. The amount of usable energy from geothermal sources varies with depth and by extraction method.

Alternative Energy Sources

An alternate energy source is a renewable energy source. The energy derived from such a source is sustainable – something that cannot run out or is endless, like the Sun. It suggests sources of energy that are alternative to the most commonly used non-sustainable sources – like coal. As our demand for energy increases, we need to look for more and more sources. We could develop the technology to use the available or known energy sources more efficiently and look to new energy sources.

Our lifestyles are also changing; we use machines to do more and more of our tasks. Our basic requirements are also increasing as industrialization improves our living standards. Thus, there is a growing demand for alternate sources capable of filling up the void of fossil fuels but are environmentally friendly.

Types of Alternate Sources of Energy

1. Solar energy: The energy received from the Sun can be efficiently used as a fuel to fulfil our energy requirements. It is the most abundant and reliable source of energy.
2. Wind energy: Wind is a plentiful source of clean energy. Wind energy farms are set up to harness wind energy; turbines are used to drive generators that feed electricity into the Grid.
3. Hydro energy: It is the energy derived from flowing water. A large reservoir can create a controlled water flow by building a dam or barrier to driving a turbine.
4. Tidal energy: This is another form of hydro energy that uses twice-daily tidal currents to drive turbine generators.
5. Geothermal energy: By harnessing the natural heat below the Earth’s surface, geothermal energy can heat homes directly or generate electricity.
6. Biomass energy: This is the conversion of solid fuel made from plant materials into electricity. Although fundamentally, biomass involves burning organic materials to produce electricity. It is a much cleaner, more energy-efficient process.
7. Ocean Thermal Energy:  The water at the surface of the sea or ocean is heated by the Sun while the water in deeper sections is relatively cold. This temperature difference is exploited to obtain energy in ocean-thermal-energy conversion plants.
8. Wave Energy: The kinetic energy possessed by huge waves near the seashore can be trapped to generate electricity. Wave energy would be a viable proposition only where waves are very strong.

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What is Geothermal Energy?

The thermal energy generated and stored inside the Earth’s crust is termed Geothermal energy. The temperature at the centre of the Earth is almost equal to the temperature of the Sun’s surface, which is maintained at a constant level by the continuously occurring process of nuclear fusion. Due to these high temperatures and extreme pressure around the Earth’s Centre, some rocks melt and cause upward movement of the mantle. These molten rocks produced in the Earth’s core get pushed upward and get trapped in particular regions.

Moreover, when underground water comes in contact with a hot spot, it becomes hot and comes out at the surface through possible outlets. Such outlets are known as hot springs or geysers. Owing to the excessive heat, the underground water gets converted into steam and gets trapped in rocks. This steam trapped in rocks can be routed through a pipe to a turbine to generate electricity. The cost of geothermal energy production is not high.

However, it is not easy to find such sites where geothermal energy can be extracted. There are very few commercially viable sites where such energy can be exploited. Several power plants are based on geothermal energy operational in New Zealand and the United States of America.

Geothermal Gradient

Much like potential in a circuit, the heat flows from a region at a higher temperature into a lower temperature, and geothermal energy is synthesized based on this principle. The difference in the temperature between the Earth’s core and its crust is a geothermal gradient. It is the reason behind the constant conduction of thermal energy in the form of heat from the core to the surface. Sometimes, the temperature gradient may reach over \({4000^{\rm{o}}}C.\)

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How is Geothermal Energy Synthesized?

For harnessing geothermal energy, we use a hydrothermal convection system. Geothermal energy generates from the heat within the Earth. The hot rocks in the Earth’s core emit the Earth’s surface with steam and pressure. We use this steam for running and producing electricity. The temperature difference between the core and the Earth’s crust provides a sufficient temperature gradient to harness a substantial amount of energy.

This procedure requires drilling a hole deep under the Earth and then inserting a pipe. The steam trapped in the rocks moves to the Earth’s surface through this pipe, thereby turning the turbine’s blades into an electric generator.  We can also use the steam to heat water from an external source which can be used to rotate the turbine blades.

Applications of Geothermal Energy

The most common uses of geothermal energy are:

Pools and Spas: Around the world, geothermal energy is being effectively used at many swimming pools and balneological (therapeutic) facilities at spas.

Agriculture industry: In the agriculture sector, the greenhouses and aquaculture ponds worldwide are heated with geothermal resources.

Household and industrial use: Cooking, industrial applications (such as drying fruits, vegetables, and timber), milk pasteurisation, and large-scale snow melting are a few other common areas where we find a use for geothermal energy.

Electricity Generation: A geothermal plant is installed within a two-mile radius of the geothermal reserve. Then, the steam from these reserves is utilised to rotate the electrical generator’s turbines or heat water to produce the steam, and consequently to generate electricity.

Geothermal heat pumps (GHPs): The heat pumps are used for heating buildings through district heating systems. They directly transport hot water through springs to facilities via pipelines. The heat pumps based on geothermal energy take advantage of the relatively stable moderate temperature conditions within the first \(300\) meters (\(1000\) feet) of the surface to heat buildings in the winter and cool them in the summer.

Advantages of Geothermal Energy

1. Clean and abundant fuel: It is a renewable resource. It is and abundant, and because there is a constant flow of heat from the Earth, it is inexhaustible and limitless. In other words, it has around for \(4\) billion years.
2. Environment friendly: There are no harmful gases involved. It is non-polluting and environment-friendly; it is not lethal like fossil fuels. Most importantly, it does not leave any residue or create a byproduct.
3. Sophisticated and modern: As geothermal power plants are incredibly sophisticated, they require large-scale research before installing them. Thus, it helps create employment opportunities at almost every stage of production and management.
4. Directly operational: Finally, geothermal energy can be directly employed as a source of energy. The countries that experience harsh cold weather use it for melting ice on the roads, heating houses, greenhouses, public baths, and more. While the price initially may seem high, the maintenance and repair cost is minor, and the energy supply is undisturbed.
5. No harmful byproducts: In nuclear energy, we have to deal with radioactive byproducts; in a biogas plant, we have to displace the leftover biological waste, but when it comes to geothermal energy, we do not have to worry about any such wastes.

Disadvantages of Geothermal Energy

1. Difficulty in Transportation: Transportation of required resources and transmission of the generated energy can be tedious and quite lengthy. We cannot transport them easily like fossil fuels. Once we harness the tapped energy, we can use it efficiently in the nearby areas only. Similarly, there is the possibility of toxic gas emission in the atmosphere with the transmission.
2. Expensive Investment: The initial cost of the installation of a geothermal plant is high. When you install such a plant to get steam from deep under the Earth, you will have to make a huge investment in material and human resources. The government or multi-national companies generally take up these projects.
3. Research intensive: An essential requirement in setting up a geothermal plant is the intensive study of the region and its places. Setting up a plant requires thorough knowledge to avoid the sit run out of steam over time because of temperature drop due to excessive or irregular supply of inlet water.
4. Available only at a few places: Another drawback is that the source of geothermal energy is limited to specific regions. Some of them are highly inaccessible, like high-rise mountains and rocky terrains, making them economically infeasible and increases the costs of setting up one such plant.
5. Requires deep drilling: Setting up a geothermal plant involves deep drilling because of the depth of geothermal sites within the Earth’s surface. However, too much drilling may cause a release of highly toxic gases in the environment, which can be fatal to the workforce and neighbouring areas.

PRACTICE QUESTIONS RELATED TO GEOTHERMAL ENERGY

FAQs

Q.1. State two disadvantages of geothermal energy.
Ans: There are quite a few disadvantages to this energy. Firstly, the procedure of injecting high-pressure streams of water into the Earth can cause minor seismic activity or small earthquakes. Secondly, geothermal plants can release small amounts of greenhouse gases like hydrogen sulfide and carbon dioxide. Thus, it impacts the environment badly. 

Q.2. Define geothermal energy.
Ans: Geothermal energy generates from the heat within the Earth. The hot rocks in the Earth’s core emit the Earth’s surface with steam and pressure. We use this steam for running and producing electricity. 

Q.3. What do you mean by Geothermal gradient?
Ans: The difference in the temperature between the Earth’s core and its crust is a geothermal gradient. It is the reason behind the constant conduction of thermal energy in the form of heat from the core to the surface. 

Q.4. What are alternate sources of energy? Mention a few types.
Ans: Non-conventional sources involve the use of renewable sources like water, sun, and wind to produce energy. These sources, unlike fossil fuels, are sustainable and environmentally friendly. A few types of alternate sources of energy are:
1. Solar energy
2. Tidal energy
3. Hydro energy
4. Biomass
5. Geothermal energy

Q.5. What is biomass energy?
Ans: Biomass is renewable organic material that comes from plants and animals. This energy is developed from the wastes of animals and humans that include byproducts along with agricultural yields, municipal solid wastes, and timber industry.

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