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EGU 2011: CCS and geothermal - the best of both worlds?

By Liz Kalaugher, EGU General Assembly in Vienna

Although they have a common goal - lowering the carbon footprint of energy systems - carbon capture and sequestration (CCS) and geothermal energy could one day end up in competition for both suitable geological sites and funding. Frank Schilling of the Karlsruhe Institute of Technology, Germany believes there’s a solution; he reckons that the two technologies could be combined to the benefit of both.

“Our storage capacity is limited so we must use the resource wisely,” he told the press at the EGU Assembly in Vienna.

Not only could the two technologies share expertise in drilling technology and reservoir management, he believes, but geothermal could enhance the storage potential of CCS. A typical geothermal energy system removes hot water (around 40 degrees C or higher) from thermal aquifers around 1000 m below the ground, extracts the heat and returns cold water to the depths.

Since this cold water is denser than the hot water it’s replacing, it potentially provides more pore space for storing carbon dioxide. In turn the addition of carbon dioxide could prevent any problems for the sub-surface caused by the introduction of negative pressure.

For geological formations where there are multiple barriers at different depths, an alternative combined system could see hot water removed from the thermal aquifer and carbon dioxide pumped in. Following heat extraction, the cold water could be returned to a higher level - the resulting negative pressure gradient would make leakage of carbon dioxide from below less likely. According to Schilling, halving the effective pressure on the caprock doubles the security of the system or doubles the storage space.

Posted by Liz Kalaugher on April 6, 2011 1:33 PM | Permalink