Energy Prospects of Deep Hot Fractured Rocks

15May
2001

With the help of the EEIG “Exploitation Minière de la Chaleur”, the operator of the European geothermal research project, the Foundation organised a dinner-debate on the energy prospects for deep, hot, fractured rocks.

The European geothermal research project at Soultz-sous-Forêt (50 km north of Strasbourg) which began in 1987 has reached the stage where beginning construction of a pilot electricity production installation (in this case of 6Mwe) based on making use of the heat contained in deep (5000 m), hot (200°C) and fractured rocks is justifiable. This heat is extracted from below ground by heating a flow of water injected from the surface and which is returned to the surface after passing through the fractured rocks. The European sub-strata contains vast deposits of such rocks whose potential is extremely promising.

A quantity of heat equivalent to that produced by burning some 1 500 000 tonnes of oil can be extracted from a volume of just 1 km ³ of rock, reducing its temperature by only 25 °C. If the initial temperature is 200°C, somewhere in the region of 15 to 20 MW of electricity could be produced for 20 years at a rate of 8000 hours/year, or more than 150 to 200 MW of heat could be distributed over the same period.

As far as France is concerned, it is estimated that 30 000 km² could be developed over a depth of 2km. Extracting 25°C from this expanse would be equivalent to an energy value of 1 million thermal Terrawatthours .
125 000 km² have been identified in Europe as having potential. By developing only 10% of this deposit to a depth of one kilometer and taking only 20° from rocks whose temperature is in excess of 200°C at a depth of around 5000 m, it would be possible to produce 1000 Terrawatthours of electricity a year, i.e. the annual production of all the nuclear power plants in Europe.

The continued support of the European Commission has been essential in providing a major proportion of the logistic means needed for the investigations, but also for encouraging and sustaining the development of ever closer links between the plethora of laboratories and research teams of different nationalities that offer a broad range of skills.

A European Economic Interest Grouping (EEIG) was set up in 1996 in order to ensure maximum efficiency in overseeing what is always a difficult transition between the stages involving purely scientific research and those dealing with the industrialisation of results via applied research. The Grouping brings together Electricité de Strasbourg, Pfalzwerke, EDF, Erga and Shell. The EEIG has suggested that the European Commission takes on responsibility for building successive stages of a pilot plant for producing electricity from geothermal sources at the site at Soultz-sous-Forêts.