[Physics Class Notes] on Geothermal Energy Pdf for Exam

Geothermal energy plays an essential role in human progress and provides quality of life to us. The term Geothermal originated from Greek in which Geo means Earth and thermal implies heat. Hence, from here, you get the geothermal energy definition – thermal energy that derives from the 1,800 miles below the crust of the Earth. It is heat deposited in the rock and fluid filling the pores as well as fissures of the Earth’s crust. Geothermal energy reaches the surface of the Earth through water or steam.

Geothermal energy is obtainable all over the planet. However, the Earth takes several years to generate this energy by decaying the minerals and forests. 

How is Geothermal Energy Generated?

There is a rise in the temperature of Earth from the surface to the core. This gradual shift in its temperature is called the geothermal gradient, which is around 25° C per 1 kilometre of depth in the majority parts of the world.

Under the hottest part of the Earth’s core, the vast majority of heat emanates from the continual decay of different radioactive isotopes. Temperatures in this part of the Earth’s surface rises above 5,000° C that helps to create this source of energy. The heat always radiates outside and warms the water, rocks, gas, and different geological elements.

When rock formations in the mantle and lower crust of Earth heat to roughly 700 to 1,300° C, they can turn into magma. It’s a molten rock penetrated by gas as well as gas bubbles that sometimes erupts as lava to the Earth’s surface. This magma melts nearby rocks and underground aquifers that emit out geothermal energy on the Earth’s surface in diverse forms throughout the world. The source of geothermal energy is lava, geysers, steam vents, or dry heat. The heat can be seized and utilised directly for heating purposes, whereas the application of geothermal energy steam is to generate electricity. 

Uses of Geothermal Energy

More than 20 countries are utilising this natural energy today. Amongst them, the USA is the biggest generator of geothermal energy in the world with the most extensive geothermal field. We can divide the uses of geothermal energy into three categories:

1. Direct Uses Of Geothermal Energy

It is the most common application of geothermal energy in which low-temperature geothermal resources are used, such as natural hot springs, therapeutic spas, aquaculture ponds, and greenhouses. Also, it is an excellent source for cooking, milk pasteurisation, drying fruit, vegetables, and timber in industries.

2. Electric Power Generation

One of the most popular uses of geothermal energy is to produce electricity. Since most of the geothermal energy from the Earth’s crust can’t bubble out as magma, steam, or water, it’s extracted by building thermal plants. This renewable source of energy generates through three different techniques, i.e., dry steam, binary and flash. 

After digging wells one or two miles deep into the ground, power produces from geothermal energy by entering the hot water and steam into it. This generated energy runs turbines connected to electricity generators. 

The USA, Indonesia, and the Philippines are successfully using this energy. Apart from these countries, Kenya and Turkey are also efficiently establishing geothermal energy plants. 

(Geothermal energy extracted from Earth through dry steam technique. Steam from hot water is converted into power using the turbine and generator then injected back into the Earth’s surface after cooling down)

3. Geothermal Heat Pumps 

Geothermal heat pumps or GHPs function by using geothermal energy found within 300 metres of Earth’s surface, which has a moderate temperature. This GHP system is made with a pump and a loop of pipes implanted in the ground that transfers heat energy between the surface air and Earth. The GHPs help draws warm air from a building to cool them down during summer. On the contrary, it warms the buildings in the winter season.

 Advantages of Geothermal Energy

• There are plenty of hot springs and natural pools across the world that emit geothermal energy. The water from such a natural source of geothermal energy is commonly used for bathing, warmth, and cooking. 

• GHPs powered heating, and air-conditioning systems are more efficient as they use 25 to 50% less electricity than conventional systems. Ultimately, there is a decrease in greenhouse gas emissions as well. 

• Many buildings, sidewalks, and parking lots are heated using geothermal energy. 

• Also, known as a green source of energy because it does not release hazardous greenhouse gases. Thus, it is safe for both environmental and human health. 

• Geothermal energy systems can adjust to various conditions.

• One of the best advantages of geothermal energy is that cold countries use geothermal energy to heat greenhouses or heat water for irrigation.

• Iceland mostly uses geothermal energy to heat buildings and water using magma and molten rock resources.

• It is a renewable, carbon-free, and sustainable source of energy. The Earth will continuously transmit heat from its core for billions of years.

 Disadvantages of Geothermal Energy

• Geothermal energy emits sulphur dioxide and hydrogen sulphide.

• The regions that consist of geothermal plants often experience minor seismic activity.

• The power plants can also damage roadways, buildings, pipelines, and natural drainage systems. 

• Land subsidence can also occur in case geothermal energy yielders fail to inject back the extracted water from the reservoir into the Earth.

• The method of drilling geothermal plants deep under the Earth proves to be dangerous for the people involved in the process that is one of the greatest disadvantages of geothermal energy.

• It is hard for developing countries to build thermal plants because of their high initial cost.

• Geothermal energy emits out at a gradual speed from the Earth’s mantle.

• The construction of geothermal sites may be hazardous for the environment as the process may discharge highly toxic gases.

More on Geothermal Energy

Geothermal energy is the energy th
at comes from the deeper part of the earth inside. It is due to the phenomenon of slow decaying of radioactive particles present in the core of the earth. This leads to the formation of geothermal energy. Earth has four parts or layers:

• Inner core. It is composed of solid iron. It is around 1500 miles in diameter.

• The outer core is composed of hot molten rock called magma. It is about 1500 miles thick.

• Mantle of magma and rock which surrounds the outer core. It is about 1800 miles thick.

• The crust of solid rock forms the continents and ocean floors. It is 15-35 miles thick in the continental part and 3-5 miles thick in the parts of the ocean.

Geothermal energy is the energy that is generated and is present inside the Earth’s crust. The temperature of the centre of the Earth remains the same as the Sun is nearly constant due to the nuclear process which occurs continuously. Due to a large degree of temperature and pressure, the rocks start to melt and this result in the upward movement of the mantle. This is because the mantle becomes lighter with heat. As the molten rocks that are formed in the crust are moved upward, they are trapped in some regions which are named ‘hot spots. When the water present underground comes in contact with such regions then steam is generated. The hot water region formed sometimes find outlets and the hot water gushes out from these areas which are called the hot springs.