About 500 power stations around the world use geothermal power to generate electricity. While there are very few in Europe . . . perhaps only one in Italy, one in France and two in Iceland, interest in such power plant is growing.
A bit of geophysics . . . temperature increases by 30C for every 1,000m of vertical depth below ground.
This thermal gradient, generated by the flow of heat from the inside of the Earth and the breakdown of radioactive elements in the crust, produces geothermal power.
Among the work being conducted in the EU is a study of Spain’s apparently massive potential by the University of Valladolid.
Researchers reckon the subsoil of the Iberian Peninsula (Spain plus Portugal) has the capacity to produce up to 700 gigawatts (about 5 times Spain’s current power generation capability) if this resource was to be exploited with enhanced geothermal systems (EGS) at a depth of 3,000-10,000m, where the temperatures exceed 150C.
For Europe as a whole they estimate the potential to be a staggering 6,500GW.
Although there are experimental EGS stations in countries such as the US, Australia and Japan, there is, according to the geothermal research team at Valladolid, only one connected to the grid: Soultz-sous-Forêts in France.
The remainder are in the few areas of the world where there are thermal anomalies and the presence of hot water at a shallow depth.
“Nevertheless, EGS resources are distributed widely and uniformly, meaning they have enormous potential and could supply significant power in the medium or long-term, 24 hours a day constantly,” said
César Chamorro, one of the Valladolid team.
“The 700GW of electricity indicated in the study represent approximately five times the current electrical power installed in Spain, if we add together fossil fuels, nuclear and renewable power.
“Even if we limit the calculations to a depth of 7km, the potential reaches 190GW; and for 3-5km it would be 30GW,” adds Chamorro.
All of this data refers to the so-called “technical potential”, which entails a cooling (using water) of 10C in rocks that are at least 150C to extract a fraction of energy during the 30-year operating period.
There is another renewable or sustainable potential, which only considers the electrical energy that could be obtained if the thermal flow was harnessed at the rate it arrives at the crust from Earth’s core.
This value is significantly less, and in the case of Spain is estimated at 3.2GW.
“It seems low, but it is the equivalent of three nuclear power stations,” said Chamorro
According to the study, the regions which reach the highest temperatures at shallower depths, and therefore, have greater geothermal potential and are prone to more detailed studies for their development are Galicia, western Castilla y León, the Sistema Central mountain range, Andalusia and Catalonia.
The reason is that there is greater friction in their subsoil between the base plates and presence of granites.
To estimate the temperature at various depths (from 3,500m to 9,500m depth) the researchers have used the heat flow and temperatures at 1,000m and 2,000m provided in the Atlas of Geothermal Resources in Europe, as well as thermal data of the land surface available from NASA.
Applying the same information to the whole of Europe, the researchers have published another study in the journal “Energy”, where they compare the potentials of each country.
Turkey, Iceland and France show the greatest potential. Altogether the technical potential of the continent exceeds 6,500GW of electricity.
With regards to the implementation of EGS technology, Chamorro and his colleagues acknowledge that there are still significant problems that must be researched, such as the appropriate thermal well perforation technique, the best way of fracturing the rock or how to operate advanced thermodynamic cycles.
According to a report from the Massachusetts Institute of Technology (MIT), in 2050, after suitable investment in R&D, 100GW of electricity could be installed with this technology in the United States.
“In the case of Spain, EGS systems could significantly contribute to the national energy mix, reducing energy dependency on other countries and cutting greenhouse gases,” added Chamorro.
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