The principle is to use heat energy through heating of water to steam. Geothermal energy utilizes high temperatures below the earth’s crust. The hot steam or water heats a fluid that in turn expands to turn turbines that generate electricity.

There are three forms that are utilized. They are as follows −

Dry-steam power stations

Basically, dry steam stations utilize the steam that flows out of geo-deposits to heat a secondary fluid that turns turbines to generate electricity. The steam emerges at a temperature of up to 150 degrees, hot enough to expand the fluid in the geothermal plant. This is one of the oldest techniques of geothermal electricity. The expansion of the secondary fluid produces mechanical energy needed for turning the turbines to generate electricity.

Flash steam power stations

Water in wells under high pressure is drawn to a region of lower pressure. This pressure shift vaporizes the water emitting steam at high temperature. This steam is separated from the water and used to heat up the fluid that turns the turbines in the generator. At this pressure, the gas is at a very high temperature.

Binary cycle power stations

Exploiting the difference in boiling points, as determined by density, is the most recent method used. A fluid with a much lower boiling point than water is used in the system. This method uses water at temperatures 58 degrees to heat a secondary fluid of a lower boiling point. Water heats up the fluid and causes it to vaporize, due to lower boiling point, and turns the turbines to generate electricity.