With TierPoint's announcement of funding for their new datacenter they also included the tidbit that they plan to use geothermal cooling as a low-impact, high-efficiency method for providing temperature control in the datacenter rather than traditional chiller cooling. Their planned system is non-consumptive, which means in addition to using the temperature gradient to provide "free" cooling it also reduces the environmental footprint of the datacenter by not introducing pollutants into the local water system that would normally need to be dealt with by sewage treatment plants, making the installation that much more green.
By taking advantage of the natural cooling available underground (the mean temperature 5 feet underground is between 50 and 60 degrees Fahrenheit) a high-volume, closed loop system should be able to deliver significant cooling to a datacenter built just about anywhere in the temperate climate zone. While there would be additional advantages in cooler climes, issues such as permafrost and the practicality of lower outside air temperatures during most of the year would make the investment in geothermal strictly for cooling a much iffier one.
The geothermal cooling technology is not one that I've heard brought up too often. It will be interesting to see, with the rapid growth in new datacenter construction, if a vendor market grows to fill this niche. I made a few phone calls to people I know in the development process for new datacenters, and when I asked about plans related to geothermal, they were uniformly of the opinion that it was a power generation technology or mentioned something I had previously written in regard to datacenters in Iceland.
It will be interesting to see if a greater awareness of the possibilities of making use of the temperature gradient, even in places where no one is really aware of it. We are too many generations away from the "root cellar" in the minds of most IT people; practical methodologies for stable temperatures and cooling that were developed a long time ago rarely enter the thought processes of the technologically driven IT professional..