Subject:- Renewable Energy Sources

Topic:- Geothermal Energy

Difficulty:- Medium

• Geothermal resources are either dry steam fields or wet steam fields.
• Hydrothermal (dry steam ) fields contain non-condensable gases $CO_2$ and small traces of hydrogen sulphide, ammonia, methane etc. these gases are released from centrifugal separators and in turbine exhaust of geothermal power plants. Though the amount of $CO_2$ released is much less compared to conventional power plants but it adds to the problem of global warming.
• $H_2S$ in the geothermal fields in excess quantity causes harmful effects on the bearings and electrical Equipment of the plant. Therefore, it is necessary to trap $H_2S$ and burned with air to produce $SO_2$ which is controlled by scrubbing of flue gases with lime or catalytic conversion technologies. $SO_2$ if not treated before released to atmosphere may have adverse effect on agriculture production and aquatic life caused by acid rain.
• The wet geothermal fields contain poisonous and toxic, material like mercury, arsenic and salt content of brine. These dissolved solids may be as high as 20% to 30% . the liquid waste causes environment problems can be resolved by re – injecting the use water waste deep into the ground. Thus the pollutants in such geothermal plants are almost eliminated.
• The heat energy of turbine exhaust steam is rejected to atmosphere in cooling towers. It causes increase in moisture in atmosphere. The drilling of wells of geothermal energy fields causes soil erosion.