The difference between the temperature in the earth’s core and the surface drives a continuous conduction of thermal energy from the centre to the exterior of the planet.
High temperatures of over 4000°C cause some of the rock in the centre of the Earth to melt and form hot molten rocks called magma. These high temperatures also cause the mantle to behave plastically and portions of it to convect upwards, since it is lighter than the surrounding rock. The rock and water in the Earth’s crust can reach temperatures of around 370°C.
Thermal energy contained in the rocks and fluids can be found from shallow depths right down to several miles below the Earth’s surface.
What is the meaning of Geothermal Energy?
How is it Used?
One example of heating and cooling is where a geothermal heat pump is installed around 10 feet underground. These pipes are filled with water or an antifreeze solution. The water is pumped around the closed loop of pipes. These ground source heat pump systems help to cool buildings in summer and maintain warmth in summer. This occurs by absorbing the earth’s heat as the water circulates back into the building.
Geothermal water has been used to help grow plants in greenhouses, for district heating in homes and businesses. It can also be piped under roads to melt snow.
How is Geothermal Energy Produced?
The first recorded instance of geothermal heat being used for producing electricity was in Larderello, Italy in 1904. Yet, geothermal heat has been used for bathing since the Palaeolithic Age. Monkeys in Japan have also been shown to use heated water from hot springs to keep warm during winter months in mountainous regions.
How Does Geothermal Energy Work?
- The oldest type is dry steam, which takes steam directly from fractures in the ground to drive a turbine.
- Flash plants pull high pressure hot water from underground and mix it with cooler low pressure water. This, in turn, creates steam that is used to drive a turbine.
- Binary plants use hot water passed through a secondary fluid that has a lower boiling point than water. The secondary fluid is turned into vapour which drives a turbine. Most future geothermal power plants are expected to be binary plants.