Thanks for your response. Are there studies comparing the energetic and material costs of construction, maintenance and operation of these power plants with other 'non-polluting' power systems? Any leads?

There was a considerable program on Geothermal in the U.S. back during the last energy crisis. The Hot Dry Rock program got a lot of attention, but there were some significant drawbacks. There were, at the time, lots of reports; I must have dumped at some stage several drawer fulls (Moving offices). Sadly it was before digital records of such things, and the old reports may not be widely available any longer.