Skip to main content.
Enviropaedia Sponsors and Supporters

Geothermal Energy

Author: Centre for Renewable and Sustainable Energy Studies - Stellenbosch University

( Article Type: Explanation )

Geothermal energy is thermal energy stored in the earth. The high temperatures are generated mainly from radioactive decay of minerals and volcanic activity and are a source of renewable energy already used for generating over 10 GW of electricity and providing more than 28 GW of heating worldwide. The temperature difference between the higher temperature geothermal source and ambient temperature (or other lower temperature source) is exploited to generate electrical power. The process typically used in this conversion uses an organic rankine cycle or steam cycle where the high temperature steam or working fl uid expands through turbine blades causing the turbine blades to rotate. This rotation of a shaft in turn drives a generator that produces the electrical power. For more information on Geothermal energy in South Africa and more detail on the working principles see