What is geothermal energy – where is it in use?

Geothermal energy is energy generated by heat in the ground: “geo” means “earth” and “thermal” means “heat.” Typically, this energy comes from digging deep into the earth, where can be found hot water and steam which is used to generate power.  

Geothermal power can be used to provide hot water and air to communities. The heat can also be used to generate electricity, in a few different ways:

The oldest method is known as “dry steam” generation, where steam is taken from deep underground and used to drive a turbine, which generates power. There is also “flash steam” generation, where hot water is pumped out of the ground at high pressure, and released into a low pressure chamber. The pressure change causes the water to vaporise, and the steam is used to generate power. The third method is known a “binary cycle” generation, and is used in places where the water from the ground isn’t as hot. In this method, the water from underground is used to heat up a second liquid that has a lower boiling point than water. The vapour from the second liquid is then used to drive turbines, which generate electricity. With all these methods, once the water from underground has been used, it is returned to the earth, making geothermal energy a clean energy source. 

One of the drawbacks of geothermal energy is that not everywhere has the same potential for geothermal energy (though nearly everywhere on earth can use small-scale ground source heat pumps). Currently geothermal energy is produced in around 25 countries, with the top 5 being the USA, Indonesia, Philippines, Turkey, and New Zealand. Another notable mention is Iceland, where geothermal energy provides heating and hot water for 87% of the buildings courtesy of geysers and hot springs on this volcanic island. In 2020, 15.6GW of energy was generated by geothermal energy – but global supply could reach as high as 2TW.