Geothermal energy is a renewable energy source whereby thermal energy is obtained from within the planet and utilized as a source of electricity, heat, etc. For over a thousand years, geothermal energy has been used for bathing, cooking and heating. Applications have been witnessed over the years such as hot springs used for bathing.
Geothermal energy is stored in fluids and rocks in the center of the earth which can reach about 370°C. The energy is generated due to heat formed from the frictional and gravitational pull formed from the initial formation of the planet and the radioactive decay of Uranium, Potassium and Thorium in the Earth’s core. There is continuous thermal energy conduction from the core of the earth to the crust (surface) due to the high-temperature difference.
The heat from the Earth’s core (interior) manifests on the surface through natural activities like hot springs, lava, steam pots, geysers, fumaroles and mud pots. For example, the high temperature in the earth’s interior causes some rocks to melt into a hot molten form called Magma. This magma manifests on the surface of the earth as flowing lava.
Unlike some renewable sources of energy, geothermal energy can produce power at a constant rate without interruption from factors like weather conditions as in solar and wind energy. These resources are more than enough to cater for humans’ energy needs.
Approximately 1.4 × 10⁶ terawatt of geothermal energy can be harnessed per year and utilized on the surface of the earth. This amount of energy is roughly equal to three times the annual utilization of all kinds of energy in the world. The amount of geothermal energy that is usable depends and varies on the extraction method used and the depth of extraction.
How can geothermal energy be used?
Geothermal reservoirs of heated water and steam placed underground can be used to generate electricity. Geothermal heat pumps installed underground are also used for heating and cooling applications which include cooling a building in summer and providing heat warmth during cold seasons.
Geothermal water has been used for various purposes such as heating homes, melting snow by piping under roads, and helping plants grow in greenhouses.
Production of Geothermal energy
Geothermal resources underground are accessed by drilling wells deep into the ground into the reservoirs in areas with geothermal activities. The resources can be utilized using geothermal systems by a process called hydraulic stimulation which enhances the geothermal resources. The heat naturally occurring in the rocks and water through permeability can also be utilized.
These natural and enhanced geothermal resources then help to drive turbines in electricity generators thereby producing electrical power.
How does geothermal power work?
There are three different designs of geothermal power plants used in producing geothermal power. These include;
- Dry steam: In dry steam geothermal power plants, the steam from fractures in the ground is taken directly to drive the turbines.
- Flash plants: They extract high-pressure hot water underground and mix it with cooler low-pressure water. This process releases steam which is separated from the liquid by cyclone separators. This steam drives the turbines to generate electricity
- Binary plants: This design of geothermal power plants works with hot water and another fluid with a lower boiling point than water. The hot water is passed through the fluid, and this converts the fluid to vapour. This vapour is then used to work the turbines.
Some of the advantages of geothermal energy include;
- The use of geothermal energy is cheaper than energy produced with fossil fuels
- It is a renewable source of energy which means it is replenished as it is used and does not get exhausted.
- The energy source is constantly available and does not depend on the weather like other sources of energy.
- It is environmentally friendly as it produces low gas emissions during electricity generation.
Some of the cons of geothermal energy include;
- The exploration and drilling of sites with geothermal power plants can be quite expensive.
- Production of geothermal energy can only be done near tectonic plate boundaries.
- These sites can also dry up after years of use and exploration.
- Geothermal power plants release hydrogen sulfide which is a gas with a very foul rotten egg smell.
- Toxic materials are contained in some geothermal fluids which must be disposed of properly.