Geothermal energy has generally been seen as limited to areas lucky enough to have hot water bubbling to the surface. Iceland, for instance, manages to produce about 19% of its electricity and about 90% of the heat for homes from geothermal sources (though they also manage to have higher per capita emissions than France or Spain). The Philippines manages to generate 25% of its energy from geothermal sources. One intriguing suggestion to broader the applicability is to create by design what plate tectonics has sometimes produce by chance. The idea is to drill two shafts into hot dry rock, pump cool water down one, and exploit the hot and high-pressure water coming up from the other. If successful, such techniques could make geothermal energy dramatically more widely available. One estimate holds that 100 gigawatts worth of engineered geothermal could be created in the United States by 2050, at a ‘commercially acceptable price.’
There are problems, of course. Our drilling expertise mostly relates to porous oil-bearing rocks: not the more solid sorts that would be between the shafts. There are also concerns that building artificial geothermal sites will destabilize the surrounding land. A project in Switzerland apparently caused a small earthquake back in 2006.
Hopefully, the technology will prove viable in some areas. The more renewable power options we have, the less we need fossil-fuel powered plants to balance the grid. Furthermore, the more different types of renewable energy are in use, the more resilient the system is to climatic changes and other shocks.