LARGE SCALE electricity generation from geothermal energy has taken a step closer to reality with the success of a recent trial in Alsace, France.
Researchers from the European Deep Geothermal Energy Programme, drilling at Soultz-sous-Forêts 50km north of Strasbourg near the German border, found rocks reaching 200°C at the relatively shallow depth of between 3km and 5km.
They believe it is feasible to inject water into a network of dry fractured rocks and then recover it through a second borehole to generate electricity and heating.
Tapping into geothermal energy is usually restricted to those rare areas with naturally occurring water at depth. So, while underground heat is distributed fairly uniformly over the Earth, only a few places can benefit from it.
Researchers said that if heat could be extracted from dry rock, this barrier would be removed and every country in the world could be sitting on an abundant source of clean and constant energy, estimated at 15M. toe (tonnes of oil equivalent) per km 2of rock at a depth of 10km.
After a series of validation tests, work is now under way on a pilot production unit. Led by an European economic interest group, GEIE Heat Mining (Electricité de France (EDF), Enel (Italy), Pfalzwerke (Germany) and Shell), the project aims to extract 75kg to 100kg of water per second at 195°C. The heat will power a turbine and an alternator to provide capacity of 5-6MW of electricity.
Construction should be finished by 2005. The prototype plant should then achieve a power of 25MW. The electricity will be bought by EDF subsidiary Electricité de Strasbourg, the local distribution company.
Geothermal energy generation is still prohibitively expensive but the team believes further research will drive costs down.