Geothermal energy is the energy contained as heat in the Earth's interior. The origin of his heat is related to the internal structure of our planet and the physical processes occurring there. Despite the fact that this heat is present in huge, practically inexhaustible quantities in the Earth's crust, not to mention the deeper parts our planet, it is unevenly distributed, seldom concentrated and often at depths too great to be exploited industrially.

    In the year of 1904, Italy firstly produced electricity powered by the steam of geothermal field in Larderello with the installed capacity of 15kW. If it can be considered as the starting point that the geothermal energy accessed to the practical utilization of energy, thus the industrialized development of geothermal energy has seen a history of nearly one century. In the latest period of 1/4 century, it is generally agreed by more and more countries, including the industrialized country and developing countries, that the thermal energy is an alternative energy available to be replenished.

    The development and utilization of the geothermal energy has little harm for the environment. Regarding the knowledge of environment impact resulted in developing and utilizing of the geothermal energy, it still remains to be accumulated in long term and recognized in depth. However, it is notably that the emission quantity of sulphur oxide and SO₂ produced in large scale geothermal power station is only parts of 100 parts than that of coal power station, in which there are no emission of nitrogen oxide in general. The employed injection technology can avoid the soil and water body in the ground to be polluted. Therefore, as a replenished energy, the geothermal energy can dramatically decline the emission of gases from the warm house and mitigate the unfavorable impact on the environment not matter it is to be used for producing electricity or its thermal resources is directly utilized.