Geothermal Energy
- Geothermal energy in the form of thermal energy is a form of renewable source of energy having high energy density. It is renewable since the earth’s interior will continue to provide energy continuously in the process of cooling of earth’s interior.
- It is inexhaustible like solar or wind energy. The geothermal energy in the form of heat energy can be utilized economically and efficiently for power generation and other applications with the existing available technologies.
- Geothermal energy or earth’s heat manifests itself on the earth’s surface in the following forms :
1. Hot water springs.
2. The geysers (hot water and steam) and fumaroles (hot steam and hot gases) released o periodically in the volcanic region or geothermal fields.
3. Volcanic eruptions of geothermal energy in the large quantities released in the form of hot lava, rocks, boiling mud etc. Though the amount of thermal energy within in the earth is very large, useful geothermal energy is limited to certain site only in the world because of the feasibility to access and extract heat. The sites from where the thermal energy can be extracted are called geothermal fields.
Generally the thermal energy available inside the earth is at a depth of more than 80 km. However, there are few locations in the world where this energy can be extracted at a depth of 0.3 km to 3 km called geothermal fields.
The geothermal energy is extracted in the form of hot water, steam and brines by drilling a hole in thermal fields. This energy can be utilized for space heating, electric power generation, industrial applications as process heat etc.
It is estimated that the average temperature gradient in the earth’s surface is 30°C per km depth. Therefore, for power generation to achieve temperatures upto 300°C, hole has to be drilled in earth’s surface of about 10 km depth.
Advantages of Geothermal Energy :
- It is reliable source of energy which is available continuously throughout the year.
- It is independent of weather conditions.
- No thermal storage facility is required.
- Capital and generation cost is low as compared to conventional thermal power plants.
- No solid pollutants.
- Needs very small land area.
Disadvantages of Geothermal Energy :
- It is a low grade heat energy since the temperatures are limited to 150°C.
- Parts of plant may corrode due to presence of salt.
- Geothermal fluids also bring in dissolved gases like H2S, CO2, NH3, gases and other solute which causes air pollution and land pollution if effuelent is not discharged into Verona ground.
- Life of plant is low compared to conventional power plants due to corrosive and ingilis abrasive geothermal fluids.
- Continuous extraction of fluid may cause settlement of land.
- Causes noise pollution due to exhausts, centrifugal separators, blow down etc. Thus, silencers are needed on some of installed equipments.