Geothermal energy refers to heat stored within the earth's core. Like any other source of energy geothermal energy has its advantages and disadvantages because there is no such thing as perfect energy source.
The most obvious advantage of geothermal energy refers to the fact that geothermal energy is clean, renewable energy source of energy. Geothermal energy is renewable energy source because it is being constantly replenished by radioactive decay of minerals at a rate of 30 TW. It is a clean source of energy because it is connected with minimum carbon emissions when geothermal power plants have emission-control systems to reduce the exhaust of greenhouse gases carried by drawn fluids.
Geothermal energy belongs to energy sources that can be directly used. Hot springs have been used for bathing since ancient times and in modern times geothermal energy is directly used to heat homes via geothermal heat pumps.
Geothermal energy doesn't suffer from intermittency issue like this is the case with solar and wind. Geothermal heat is available 24-7 and is therefore one of the most reliable renewable energy sources, a one that does not require energy storage solution in order to run all the time.
Harnessing geothermal energy has minimal land and freshwater requirements unlike for instance solar energy which needs large area and plenty of water for cooling. Geothermal plants use only 3.5 square kilometres (1.4 sq mi) per gigawatt of electrical production and require just 20 litres of freshwater per MW/h.
The biggest disadvantage of geothermal energy are high capital costs, most of which refer to exploitation and drilling. Geothermal power plant construction and well drilling currently cost about €2-5 million per generated MW of electricity.
The other disadvantage of geothermal energy refers to small number of countries that currently harness geothermal energy. Geothermal energy is currently being harnessed in only 24 countries of the world. The main reason why more countries do not decide to go for geothermal energy is the fact that geothermal power plants are currently cost-effective only in areas near tectonic plate boundaries though the recent technological advances such as EGS (enhanced geothermal systems) should significantly expand the range of viable geothermal resources in years to come.
The lack of qualified personnel needed to install geothermal systems is often being mentioned as one of the geothermal energy disadvantages. Geothermal energy isn't as popular as solar and wind are which means that there is less available qualified personnel and they also cost a lot.
Local depletion of geothermal resources has been experienced in several well known geothermal sites such as Geysers which means that extraction of geothermal energy must be closely monitored in order to avoid local depletion and keep geothermal energy sustainable on a long run.
If not done with adequate care enhanced geothermal systems can even trigger earthquakes therefore severely affecting land stability.