Geothermal energy is thermal energy generated and stored in Earth. Temperatures at the core may reach 6000°C. This heat is continuously radiated to the earth's crust which helps to maintain ambient global temperatures of 6-15 °C, 15m below the surface suitable to heat and cool buildings almost anywhere in the world using Ground Source Heat pump and save upto 40% energy locally. Sometimes rock and water is heated up to 370 °C in geologically favorable locations, making it the most sustainable energy resource for heating and electric production.
Hot springs have been used for bathing and for space heating since Aryans, Romans and Greek times. In Manikaran Indian Himalayas food has been cooked in the HOT springs and distributed free to all visitors for the last 600 years. The Blue lagoons in Iceland have emerged as geothermal tourist destination. In modern times geothermal is now better known for electricity generation and heat pumps. The Larderello geothermal power plant in Italy built in 1904 has been successfully running for over 100 years 24 x 365 hours now with nearly one GW base load power. Geothermal power plants use hot steam (Flash, Binary or Dry) from a reservoir to power turbines in USA, Indonesia, Philippines, Iceland New Zealand. Enhanced geothermal systems (EGS) are also in the development stage in Australia and America which use heat from hot rocks to generate electricity by injecting water into hot dry rocks (HDR). Krafla geothermal project successfully concluded after drilling into Magma at 2100 meters generating temperatures of more than 900°C capable of generating many Giga Watt (GW) of power. Agneyodgara (Lava Energy) and GEOCOGEN are advanced geothermal energy concepts aimed to produce plenty of GWh clean energy by tapping lava energy in geologically favorable environments.
Geothermal energy is seen as a most economical energy in present days. There is urgent to frame a National Geothermal Policy for R&D investments in geothermal exploratory wells to provide green clean energy to the people.
Dr Ritesh Arya, Director, Geothermal Energy section of ISEO