DOE Invests in Greenfire’s CCS that Makes Geothermal Cheaper

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Greenfire Energy, a novel geothermal/CCS startup that is attempting to extract geothermal energy using injected CO2 as the working fluid instead of water, has been selected to receive $2 million in funding from the Department of Energy.

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.

Muir told her he is not sure whether they will use a closed loop binary system for the pilot, but if they go with a binary system, they will use underground rocks to heat CO2 into a supercritical state which will then be used, once it returns to the surface, to heat a second fluid that will spin turbines to create electricity.

The supercritical CO2 will be cycled through the system over and over to generate power, but each time, some of the CO2 – between 5 and 60 percent, each cycle – will stay permanently trapped underground.

All of the cutting-edge geothermal technologies selected for trials with the total of $20 million in funding from the DOE work on ways to take advantage of low-temperature geothermal resources, which are more widely available nationwide. The funding is woefully inadequate for fostering innovation. Greenfire Energy alone projects that its total costs from start-up through demonstration-phase operations will be $32 million.

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