Last week Google.org announced their latest round of clean energy investments which are geared towards the development of unconventional geothermal technology.

A total of about 11 million dollars will be invested across two companies and a university in order to lower the cost, improve the technical feasibility and expand research in the area of Enhanced Geothermal Systems (EGS).

While conventional geothermal technology relies on underground caverns that are filled with water or steam to produce energy, EGS technology injects water into dry holes, thus greatly expanding the number of possible sites that may yield power.

A 2005 study by the Massachusetts Institute of Technology (MIT) assessed the possibility of wider EGS development. The MIT study concluded that, “The potential of EGS in evolving U.S. energy markets is large and warrants a comprehensive research and demonstration effort to move this technology to commercial viability”.

The Director of Climate and Energy Initiatives for Google.org says that, “EGS could be the ‘killer app’ of the energy world.” The challenges in developing meaningful production of energy from both standard geothermal and EGS are many though.

The MIT report notes that, “…the main constraint is creating sufficient connectivity within the injection and production well system in the stimulated region of the EGS reservoir to allow for high per well production rates without reducing reservoir life by rapid cooling.”

So when you inject water into a dry hole that is hot, the rocks in the hole will get cooler over time. No one seems to know exactly how fast the rocks will cool. This fact raises the possibility that repeated drilling will be necessary in order to continue to exploit the geothermal resources in a particular location.

The impact of the drilling related to EGS is likely to be an issue that limits future development. According the Department of Energy, “Drilling a well and testing the temperature deep underground is the only way to be sure a geothermal reservoir really exists.”

So in order to find your resource lots experimental drilling will have to occur. And the holes drilled are thousands of feet deep which means significant time and cost is involved.

The need to inject water presents another potential problem for EGS developers. Where will the water be pumped in from? How much water is needed to maintain production? These questions will be of great concern to the municipalities that govern the lands used in the production of this power.

EGS may be indeed be a viable clean energy generation technology. It is also a very a risky and expensive technology that yields its share of negative environmental impacts.