Geothermal energy is the thermal energy generated and stored in the Earth. Thermal energy is the energy that determines the temperature of matter. The geothermal energy of the Earth's crust originates from the original formation of the planet and from radioactive decay of materials. The geothermal gradient, which is the difference in temperature between the core of the planet and its surface, drives a continuous conduction of thermal energy in the form of heat from the core to the surface.
The first use of geothermal energy for electricity production was in 1904 in Larderello, Italy. However, it was not until the 1970s that the use of geothermal energy began to be seen as a serious alternative to fossil fuels. The oil crisis of 1973 led to a surge of interest in geothermal energy, and since then, the technology has been developing rapidly.
Geothermal energy has a wide range of applications, from electricity production and heating to agriculture and aquaculture. The technology is also being used to power industrial processes, such as desalination and food processing. The geothermal energy market is expected to grow to $6.8 billion by 2026.