Since thedawn of Humanity, Man has always been able to take advantage of geothermal energythis energy of which geysers, hot Springs and volcanic eruptions manifested their existence to him. However, the discovery of more easily mobilized energies (coal, oil) did little to encourage its development. Now, geothermal energy is making a comeback.
Today, the situation is changing in terms of energy. The scheduled depletion of reserves offossil fuelsthe need to preserve the environment and the global warming due togreenhouse effect impose to give their full place to renewable energies. Geothermal energy is one of them.
The heat of the earth comes from the decay of radioactive elements present in the rocks and from the earth core which generate a heat flow to the surface. The greater the depth, the higher the heat, increasing on average by 3°C every 100 meters. But this geothermal gradient can be much higher in certain specific geological configurations.
Low energy geothermal energy and high energy geothermal energy
Certain underground geological formations naturally contain aquifers whose water (and/or steam depending on the conditions of temperature and pressure) are the vector of thethermal energy. Very low energy geothermal energy uses reservoirs located less than 100 meters away and whose water temperature is below 30°C. It is used for heating and/or air conditioner, via a heat pump. Low-energy geothermal energy relies on aquifers at temperatures between 30 and 100°C. It is used in heating networks for the urban heating or in the context of industrial processes, for example. Medium-energy and high-energy geothermal energy (up to 250°C) is used to produce electricity, by means of turbines.
A draft revision of the European ENR directive of 2009 also provides that at least 27% of electricity production in the EU will come from renewable energies by 2030… More specifically with regard to geothermal energy, France’s objectives are to produce 850 ktoe (kiloton of oil equivalent) in very low energy geothermal energy, 500 ktoe in low and medium energy geothermal energy and 80 MW in high energy geothermal energy. Because geothermal energy is the only source of renewable energy that addresses the two major energy sectors: electricity production and heat production.
It is regular, with an average availability of 80%, and non-polluting. And it has reached a level of technical and commercial maturity that allows it to compete without complex with the others. renewable energies.
However, the resources are considerable and, in certain parts of the world (volcanic islands in particular), easily mobilized. As for energy production costs (in the case of electricity, higher than with fossil fuels – with some exceptions, see Bouillante article), a strong development of geothermal energy, a guarantee of scientific and technical achievements, would reduce them, while limiting the risks incurred by investors.
In this file, we describe the geothermal energy or heat of the ground, a local energy and respectful of the environment, it does not emit any greenhouse gas. A continuous and renewable resource, the heat of the earth present on all continents is totally free.