Geothermal Energy Definition

The Geothermal energy comes from two words – Geo (Earth) and thermal (Energy). It is renewable energy because heat comes from earth surface continuously. The geothermal energy is renewable energy produced by using heat of earth surface.

Earth Layers

An inner core of solid iron about 1500 in diameter.
An outer core of hot molten rock called magma about 1500 miles thick
A rock surrounding magma is about 1800 miles thick
A crust of solid rock that forms the continents and ocean floors of 15 to 35 miles thick under the continents

Core

About 1800 miles below earth’s surface, hottest part of the earth that is called as core.
A small portion of the core heat comes from gravitational pull formed when earth was created.
The most of the earth heat is generated by radioactive isotopes such as potassium-40 and thorium-232.
The potassium has 20 neutrons in its nucleus however potassium-40 has 21 neutrons.
The radioactive decay is continuous process in the core therefore rise about 5000 ⁰C.
The earth’s temperature rises as we go depth from the surface, it is called as geothermal gradient.
The geothermal gradient is about 25 degree centigrade per 1 km of depth.

Courtesy: Undecided with Matt Farrell

Magma

The magma is molten rock by gas and gas bubbles.
The rock is heated about 700 – 1300 degree centigrade and it becomes magma.
The magma heats nearby rocks and underground water, hot water is released through hot springs, geysers, steam vents etc.

Courtesy: US Department of Energy

Geothermal Energy Sources

Hot water
Hot springs
Spring vents
Underwater hydrothermal vents
These are geothermal resources captured and used directly to heat or their steam can be used to generate electricity.

https://education.nationalgeographic.org/resource/geothermal-energy

Advantages Of Geothermal Energy

The earth is continuously radiate out heat for billion of year therefore it is renewable energy.
The geothermal energy can be assessed anywhere and utilized anywhere in the world.
Geothermal energy is clean, it only emits water vapor
Some types of geothermal energy emit sulfur oxide, nitrous oxides and particulates.
If the primary reservoir is managed properly, the geothermal power plant can be last for decades.
The geothermal plant works as base load plant, they can work in summer or winter. It produces electricity for 24 hours in a days.
The geothermal plant required 1046 square kms of land for GWh plant, wind energy requires 3,458 square kms whereas solar plant requires 9,433 square kms.
Geothermal power plant emits 97% less acid rain causing sulfur compound and 99% less carbon dioxide than fossil fuel power plant of same size.
Most geothermal power plants inject the geothermal steam and water that they use back into the earth. This recycling helps to renew the geothermal resource and to reduce emissions from the geothermal power plants.

Disadvantages of Geothermal Energy

Geothermal plant is linked with lower earth’s surface or sinking of land, this can lead to damaged roadways, natural drainage, underground cables and pipelines.
It released small amount of carbon dioxide and hydrogen sulfide.
If the geothermal resources are not properly insulated, toxic element in the underground water such as mercury, arsenic and selenium can be leaked.
The capital cost of the geothermal plant is very high.

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