An artificial geyser
Electric and thermal power produced from geothermal energy depend on the existence of underground infiltrations.
However, there are some technologies for geothermal exploitation in the absence of natural aquifers. The main idea is to exploit the heat of the rocks (that increases deep underground), even when there is no water under the surface. The main assumption is that in some areas, where there is friction between continental plates, the temperature at 5 km of depth reaches 200°C. Therefore, cold water is injected into natural cracks and recovered (by sucking it with a pump) as vapour in order to activate turbines, also recovering heat to be used with district heating. This technology is also known as HDR (Hot Dry Rock).
The prototype of this project, built close to Strasbourg, uses the oil industry technologies and has 6 MW of power.
However, in 15-20 years, the site, exploited in this way, will loose its heat and it will be necessary to move somewhere else (it takes a hundred years for it to heat up again).