What is Geothermal Energy?

History of Geothermal Energy

Before 10,000 years ago, humans were using hot springs as a source of geothermal energy for bating & cooking. There is evidence showing that Native Americans use geothermal energy for cooking. During the first century of CE, Romans & Greeks were using hot springs for bathing purposes. As per the Britannica, the first district heating system in the world was installed at Chaudes-Aigues, France, in the 14th century. 

In 1892, Americans were used first-time geothermal heat for residential purposes or space heating. After 1930, Reykjavik (Iceland) start using geothermal energy (geothermal water) for space heating. Not only 40 or 50%, but 99% of the city were using geothermal energy.

After the 19th century (Industrial Revolution 2), industries & cities got to know the potential of geothermal power. In 1904, the First experimental plant of geothermal energy for electricity generation was made in Larder Ello. After 1913, the use of this technology took place for commercial purposes. This plant produces 250 kW of power.

In 1927, the first exploratory wells were drilled by a company named Pioneer Development Company in Imperial Valley, California.

Most countries like America, China, hungry, Japan, Iceland, and Turkey were using geothermal energy from 2015. This number is beyond 80 countries using this energy.

What is Geothermal Energy?

Most of us may have heard about the natural hot springs pool, and some of us may have experienced it also. But have ever wondered from where all that heat comes? Well, of course, it is not artificial heat.

All this heat comes from the underground that is deep beneath the surface of the earth, and we call it Geothermal Energy. In simple terms, geothermal energy is the heat energy acquired by the earth.

As we all know, the planet earth is hot and full of energy. The deeper you travel into the earth, the more it gets hotter and hotter. The temperature of the earth’s core is estimated to be above 4000 degrees Celsius.

Geothermal energy is the heat that comes from the earth’s crust. This heat is trapped in between the rocks & other parts of the earth’s crust. Due to this high temperature & pressure, rocks melt & behaves plastically. So that it comes upward and heat the water present inside the earth up to 370 degrees Celsius. In the form of steam, geothermal energy comes from the earth’s surface.

Sometimes, this melted rock breaks the earth’s surface & it comes on the surface.

On the earth surface, geothermal energy available in the below forms-

–         Hot water spring

–         Hot steam & hot gases are released periodically in the volcano region.

–       Volcanic eruptions of geothermal energy in large quantities in form of lava, rocks & boiling mud.

These underground hot water reservoirs generate naturally. We only do well drilling over that surface to use those reservoirs for our purpose. These fulfill our growing energy demands. It also is useful for heating water, air conditioning, and greenhouse heating purpose.

According to the International Renewable Energy Agency (IRENA), geothermal energy has grown steadily from around 10GW worldwide in 2010 to 13.3GW in 2018.

How does Geothermal Energy work?

As we go deeper below the earth’s surface, natural water reservoirs are present. And the earth’s crust gets warm by the sun’s heat. This heat from the earth’s crust warms the underground water reservoirs. This is how natural hot water reservoirs get generated below the earth’s surface.

In some locations, it is available at a depth from 300 to 3000m. Such locations known as geothermal fields. By using today’s advanced technology, we can locate and drill into the geothermal resources at only a few kilometers deep and capture the rising hot water and steam.

By releasing this to the turbine, the turbine rotates & produce electricity. The turbine is in connection with the generator to produce electricity. And the formation of water is reinjected back into the same reservoir underground to be reheated and recycled.

What are Geothermal fields?

Though the amount of thermal energy within the earth is large. But the sites of useful geothermal energy are less or available to certain sites only in the world. This is because of the feasibility to access & extract heat. The thermal energy is extracting from those locations is called geothermal fields.

Generally, thermal energy available inside the earth is at depth of more than 80km. However, there are few locations in the world where this energy is extracting from a depth of 0.3 to 3 km.

Types of Geothermal Energy Power Plant

There are three types of geothermal energy power plants as follows-

Dry steam power plant

In this power plant, steam generates directly from the geothermal reservoir. This steam is directly supplied to the turbine & rotates the turbine. The turbine is in connection with a generator & produces electricity.

After rotating the turbine, the steam goes through the condenser. The condenser converts the steam into the water known as condensate. This condensate is injected back through the injection well into the earth.

These types of hydrothermal reservoirs are very rare.

Flash steam power plant

There are locations where we can find geothermally heated water reservoirs at a high temperature of over 350 Fahrenheit. In such locations, flash steam power plants develop.

This hot water reservoir is known as brine. This brine is transfer to a vessel where it cools. As it cools, the fluid quickly turns into vapor (flash) and the waste brine is injected back into the earth. These vessel-generated vapors drive the turbine, and the rest procedure is the same as in dry steam power plants.

Binary cycle power plant

This type of power plant develops in locations where water reservoirs are available at a lower temperature of up to 100 Fahrenheit. This hot water passed to a heat exchanger. This heat exchanger is with the secondary fluid (Butane and Pentane Hydrocarbon) has a lower boiling point than the primary hot water.

Hot water from underground heats the secondary fluid, and it flashes into vapor at a lower temperature. This vapor drives the turbine, and the rest procedure is the same as in dry steam power plants.

Advantages of Geothermal Energy

  • The main advantage is geothermal energy is an environmentally friendly energy source. It has very low emissions that do not affect the environment. It is an endless, clean, and renewable energy source.
  • Geothermal energy is using to generate electricity, heating water, air conditioning, and greenhouse heating purpose.
  • After the initial plant building cost, the minimal cost requires to generate power. Also, the plant has a small physical footprint as compared to other plants.
  • The thermal and nuclear power plants need fuels to produce electricity. But the geothermal power plant does not require fuel to produce electricity. Ultimately this saves the expense on fuels.
  • The few byproducts that can come up are reinjecting back to the underground. But in other plants, it is difficult to manage the solid waste. So it lowers the cost of this energy source.
  • Geothermal energy helps to meet our growing energy demands.

Disadvantages of Geothermal Energy

  • However, there are some disadvantages to the energy source as geothermal fields are not universally available. These power plants are rare.
  • Also, the initial plant development cost is very high considering the infrastructure and drilling.
  • It is not a large-scale replacement to classic energy sources.
  • Geothermal energy sources are close to volcanic activity and require deep drilling. If done incorrectly, poisonous gases can come from beneath the earth and release into the air.
  • Despite low CO2 production geothermal causes other emissions like sulfur dioxide and hydrogen sulfide.

Thank you Mr. Sagar Wagh for sharing his valuable information about the above topic. Thank you once again.

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