Carbon storage and
electricity generation project gets DoE funding
A project aimed at using geothermal heat to power an electricity-producing turbine with supercritical carbon dioxide has received a $5 million grant from the U.S. Dept. of Energy (DoE; Washington, D.C.; www.energy.gov). The project also incorporates an element of CO2 sequestration in sedimentary rock, whereby a portion of th CO2 injected into the hot sedimentary layer remains there, so that the process requires a constant stream of CO2.
The three-year project, led by researchers at Lawrence Berkeley National Laboratory (Berkeley, Calif; www.lbl.gov), represents the first attempt to convert geothermally heated CO2 into useful electricity.
"The project is focused on validating the concept of using CO2 as a working fluid in the subsurface for geothermal energy production," says Berkeley Laboratory researcher Barry Freifeld.
The process would begin by injecting CO2 into a wellbore at a supercritical state (pressure above 70 bars and temperature greater than 31ºC ) into a layer of 125ºC sedimentary rock that lies over 3 km beneath the earth's surface. Under these conditions, CO2 becomes more pressurized and further heated in the underground rock. The higher-pressure, higher-temperature CO2 is extracted through a separate but nearby producer well.
It is expanded through a heat-engine turbine, where is higher entalphy is converted to shaft work. The turbine generates electricity, and the CO2 is cycled through the loop again.
The geothermal-heat system will be designed so that a portion of the CO2 remains stored in the rock, and a continuous supply fo new CO2 will be supplied to the loop.
The turbines, to be designed and built by Echogen Power Systems (Akron, Ohio; www.echogen.com), will be based on technology already developed by the company (a supercritical CO2) based power-generation system for low temperature waste heat recovery that has a turbine similar to that required by the geothermal project.
Pilot testing is planned for the third years of the project an the Cranfield site in Mississipi, where a DoE injector well an two heavily instrumented monitor wells for carbon sequestration research already exist.
Ref: Chemical Engineering Magazine - www.che.com - September 2011, pag. 14.
The process would begin by injecting CO2 into a wellbore at a supercritical state (pressure above 70 bars and temperature greater than 31ºC ) into a layer of 125ºC sedimentary rock that lies over 3 km beneath the earth's surface. Under these conditions, CO2 becomes more pressurized and further heated in the underground rock. The higher-pressure, higher-temperature CO2 is extracted through a separate but nearby producer well.
It is expanded through a heat-engine turbine, where is higher entalphy is converted to shaft work. The turbine generates electricity, and the CO2 is cycled through the loop again.
The geothermal-heat system will be designed so that a portion of the CO2 remains stored in the rock, and a continuous supply fo new CO2 will be supplied to the loop.
The turbines, to be designed and built by Echogen Power Systems (Akron, Ohio; www.echogen.com), will be based on technology already developed by the company (a supercritical CO2) based power-generation system for low temperature waste heat recovery that has a turbine similar to that required by the geothermal project.
Pilot testing is planned for the third years of the project an the Cranfield site in Mississipi, where a DoE injector well an two heavily instrumented monitor wells for carbon sequestration research already exist.
Ref: Chemical Engineering Magazine - www.che.com - September 2011, pag. 14.
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