The Economist has published an excellent article about the competitive edge that geothermal have over all other forms of renewable and low-carbon energy.
A quick quote from the article:
There is, however, much to like about geothermal energy. It is reasonably clean; leaves behind little in the way of waste; does not suffer the vagaries of the weather or the inevitability of sunset; makes the tiniest of footprints on the land; and is pretty well inexhaustible. Above all, it is more or less free for the taking. Yet, lacking the political clout of wind and solar power, geothermal electricity has never received the attention it deserves.
Give it a read at: http://www.economist.com/news/