Current Limitations of Enhanced Geothermal Systems
EGS power plants can be set up wherever there is a sufficient underground heat source combined with a large supply of injection well water. EGS is currently seen as having the greatest potential for generating significant quantities of geothermal electric power. However, EGS power generation has several limitations that have held back its widespread implementation.
In a follow-up to the 2006 MIT report, in 2008 the US Department of Energy did a comprehensive evaluation of the conclusions reached by the MIT panel and issued its own report describing (in detail) the current status of water-based Enhanced Geothermal System technology.
One major limitation of EGS power generation is that it requires very large quantities of water to serve the needs of the injection well in an EGS well system. In those areas where sufficient water is available, a problem arises due to the ultimate pollution of that water due to the minerals, salts and other toxic elements injection well water concentrates as it moves through the EGS cycle.
In addition to the pollution of injection well water, hydrofracing of subsurface hot rock associated with EGS power generation to create an underground reservoir can adversely affect land stability in the surrounding region; cause gaseous emissions; cause noise pollution; induce seismic activity (several plants have been decommissioned due to tremors); induce landslides, potential aquafir contamination and cause disturbance of natural hydrothermal manifestations. In areas like Southern California where there is already seismic activity and earthquake sensitivity, injection of water for EGS has been shown to increase seismic activity (Source: MIT, 2006). Also, due to the severe allocation of water from the Colorado River, the use of injection water for EGS plants is seriously limited.
Maintenance costs for current geothermal technology is adversely affected by scaling, corrosion and mineral deposition due to the caustic nature of the water.