Geothermy

Geothermal energy comes from the Earth's heat. Most of this heat comes from the disintegration of radioactive elements in the Earth's crust and the dissipation of primitive energy. Its most visible manifestations are well known (volcanoes, geysers, hot springs, etc.).

Less well known than the majority of other renewable energies (solar, wind, etc.), geothermal energy nonetheless has certain characteristics that give it specific advantages: independence from external elements, presence in all locations, respect for the environment, energy and economic performance. Used long before traditional energies, its potential, depending on the techniques developed over time, is virtually unlimited.

The term geothermal energy covers a wide range of techniques and applications. As far as techniques are concerned, the spectrum ranges from heat extracted at great depths to the use of the properties of the subsoil at shallow depths, via the exploitation of heat from volcanic zones. As far as applications are concerned, there are two main ones: power generation and heat supply. Electricity generation requires a resource with a temperature in excess of 90°C, found in particular in volcanic zones bordering lithospheric plates. For heat supply, applications range from heating a single house to creating a heating network capable of supplying urban complexes of several thousand dwellings, as well as heating greenhouse crops or fish farming ponds.

Geothermal energy has reached a level of technical maturity that enables it to be used to produce electricity at costs comparable to those of other renewable energies (hydropower and wind power) and heat at costs competitive with those of fossil fuels (gas, fuel oil).

New forms of geothermal energy, in particular those that do away with the need for aquifers – such as "deep hot fractured rock" geothermal energy –, open up prospects for the widespread use of geothermal energy anywhere.

Like most renewable energy sources, geothermal energy is capital-intensive, i.e. involving high investment costs. Its development requires :

• a degree of price stability for competing fossil fuels. The current prospect of high fossil fuel prices is certainly an advantage, but the difficulties encountered during the oil counter-shock of 1985 are also a hindrance for some;

• financial support and investment guarantees, for which the public authorities have developed the necessary incentives;

• setting up structures specific to the sector: project management, financing, project management, technical management, research, etc.

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