Geothermal power is a common source of energy for regions with easy access to high geologic or underground temperatures. The technology basically utilizes the high heat sources underground to convert water to steam. This source is not economical to those regions outside geologically active hotspots, where access to this heat source is difficult.

Three types of geothermal power generation exist, which is utilized depending on the level of geothermal heat available. The first and oldest type, called ‘dry steam’ plants, simply use geothermal steam of 150°C or greater to turn turbines.

The second and most common type, called ‘flash steam’ plants, extract deep high-pressure hot water into lower-pressure tanks and use the resulting flashed steam to drive turbines. Unlike dry steam plants, this type requires fluid temperatures of at least 180°C.

The third and newest type, called ‘binary cycle’ plants can accept fluid temperatures as low as 57°C. The moderately hot water is passed by a secondary fluid with a much lower boiling point than water, causing the secondary fluid to flash vaporize, which then drives the turbines. This type is the most common type of geothermal plant being constructed today.