Energy which determines the temperature of matter is called thermal energy. Geothermal energy is the thermal energy that is generated and stored inside the Earth. It is generated from the continual heat loss due to radioactive decay of materials. The high temperature and pressure in the Earth's interior causes some rocks to melt and solid mantle to behave plastically. Water from geothermal springs can be used for a variety of purposes such as bathing, heating and generating electricity. Geothermal power is cost-effective, reliable, sustainable and environmentally friendly. Geothermal energy is an upcoming field of science that has undergone rapid development over the past few decades. The ever growing need of advanced technology is the reason that has fueled the research in this field in recent times. Scientists and students actively engaged in this field will find this book full of crucial and unexplored concepts.