The term geothermal can be derived from the Greek words “geo” — meaning earth and “therme” — meaning heat. Geothermal energy is the thermal energy of the Earth. Part of this energy is residual heat from the formation of our planet about 4.5 billion years ago, while another part is continuously generated by the decay of radioactive elements. Geothermal energy is a renewable, low-emission energy source with significant potential for heat and electricity production.