Geothermal energy is the heat that comes from the sub-surface of the earth. It is contained in the rocks and fluids beneath the earth’s crust and can be found as far down to the earth’s hot molten rock, magma.
To produce power from geothermal energy, wells are dug a mile deep into underground reservoirs to access the steam and hot water there, which can then be used to drive turbines connected to electricity generators. There are three types of geothermal power plants; dry steam, flash and binary.
Dry steam is the oldest form of geothermal technology and takes steam out of the ground and uses it to directly drive a turbine. Flash plants use high-pressure hot water into cool, low-pressure water whilst binary plants pass hot water through a secondary liquid with a lower boiling point, which turns to vapour to drive the turbine.
Geothermal energy is used in over 20 countries. The United States is the largest producer of geothermal energy in the world, and hosts the largest geothermal field.
Pros and Cons of geothermal energy
The British Geological Survey describes geothermal energy as a “carbon-free, renewable, sustainable form of energy that provides a continuous, uninterrupted supply of heat that can be used to heat homes and office buildings and to generate electricity.”
Geothermal energy only produces one-sixth of the CO2 produced by a natural gas plant and is not an intermittent source of energy like wind or solar. Its potential production could reach at least 35GW and as high as 2TW.
However, there are some drawbacks to the energy source. Despite low CO2 production geothermal has been associated with other emissions like sulphur dioxide and hydrogen sulphide.
Similar to fracking, geothermal power plants have been the cause of mini tremors in the area they operate in and also has a high initial cost to build. It is also described as “the most location-specific energy source known to man” due to its activity being along the tectonic plates of the earth’s crust. As such, it is limited to countries such as the aforementioned US and Iceland, alongside Kenya and Indonesia.
