Geothermal Energy to Electrical Energy Conversion

Please read Geothermal Energy- Introduction to know about the basics of Geothermal energy.

Electricity Generation

The above picture shows the schematic representation of electricity generation in the geothermal power plant.

To generate electricity, we need steam to rotate the turbine which is coupled with the generator to generate electricity.
Generally, in other thermal power plants, they use fossil fuels to boil the water to convert it into steam. But, in the geothermal power plant, we get the steam from the hot water reservoirs which is about a couple of miles or more under the surface of the earth.

Types of Geothermal Power Plants

• Dry steam power plant
• Flash steam power plant
• Binary cycle power plant

Dry Steam Power Plant

• In this type, the Geothermal reservoir containing pure steam is required. 
• The pure dry steam gets directly from the geothermal reservoir to run the turbines that produce power through the generator. 
• It is a very rare type of geothermal power plant and very less number of plants only available in this type. some of them are in California, Italy, and Japan.

Flash Steam Power Plant

• It is a commonly used geothermal power plant. 
• In this type, the geothermal reservoir containing both hot water and steam and also pressure changing system is required.
• Geothermally heated water under pressure is separated in a surface vessel (called as "steam separator") into the steam form and hot water (called "brine").
• The steam is delivered to spin the turbines (heat energy converted into mechanical energy), and the turbine powers the generator (mechanical energy converted into electrical energy).
• The liquid from the turbine is passed to the condenser and injected back into the reservoir.

Binary Cycle Power Plant

• This type of power plant does not use steam directly to spin the turbines.
• The geothermal water heats up another liquid, such as isobutane or other organic fluids such as pentafluoropropane, that boils at a lower temperature than water.
• The two liquids are kept separate during the process by the use of a heat exchanger.
• The heat exchanger transfers the heat energy from the geothermal water to the working fluid.
• The secondary fluid expands into a gaseous vapor, like steam. This expanded steam spins the turbines that produce power through the generator.
• All of the produced geothermal water is injected back into the reservoir.