What Is Geothermal Energy?

Geothermal energy is heat derived within 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. Water or steam carry the geothermal energy to the Earth’s surface. Depending on its characteristics, geothermal energy can be used for heating and cooling purposes or be harnessed to generate clean electricity.

This key renewable source covers a significant share of electricity demand in countries like Iceland, El Salvador, New Zealand, Kenya, and the Philippines and more than 90% of heating demand in Iceland. The main advantages are that it is not depending on weather conditions and has very high capacity factors; for these reasons, geothermal power plants are capable of supplying baseload electricity, as well as providing ancillary services for short and long-term flexibility in some cases. It's clean and sustainable.

Many technologies have been developed to take advantage of geothermal energy like 1. Geothermal Electricity Production ( Generating electricity from the earth's heat. ) 2. Geothermal Direct Use ( Producing heat directly from hot water within the earth. ) 3. Geothermal Heat Pumps ( Using the shallow ground to heat and cool buildings. ). 

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 the 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.

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.