DOE Invests in New Geothermal Extraction Method
Source: Clean Technica, Susan Kraemer (4/20/11)
"New method could generate baseload geothermal electricity at lower, safer temperatures."
The DOE's Office of Energy Efficiency and Renewable Energy has awarded GreenFire Energy the funding as part of $20 million in investment in cutting-edge geothermal technologies.
If successful, Greenfire Energy's pilot will demonstrate a way of generating baseload geothermal electricity at lower temperatures, that not only conserves water but also geologically sequesters carbon dioxide. Low temperature geothermal is a much more widely available resource in the US than high temperature.
The company will use naturally occurring CO2 deposits at a depleted gas field for the test of what they call CO2E. The four partners–a geologist, a chemist, an environmental specialist and an oil industry technologist–believe that their proposed technology holds the promise of lower capital costs than regular geothermal.
There are several advantages to using carbon dioxide rather than water as a geothermal drilling fluid. It has a lower viscosity than water, which makes it easier to inject into rock formations. It can be brought to a supercritical state–a state of matter with the qualities of both a gas and a liquid. It can be kept in that state much easier than water, which requires higher heat and pressure.
This reduces the need for cooling towers and pumps and makes it more efficient at shallower depths and lower temperatures. So the technology expands geothermal potential nationwide, and being shallower, lowers drilling costs, and of course, conserves water.
CO2 also increases volume with increases in temperature, much more than water does, and "that's what's powering our system" GreenFire President Mark Muir told Penelope Kern at Energy Prospects.