April 10-14, 2016
CO2 emissions from human activities are a substantial contributor to climate change.1 To reduce CO2 emissions on a large scale, CO2-reduction technologies such as CO2 capture and storage (CCS) will need to be competitive with current energy technologies.1 CCS systems are costly due to the equipment, construction, and energy needed to capture CO2, transport it via a pipeline network, and inject it into deep saline aquifers. In CO2 capture, utilization, and storage (CCUS) systems, the CO2 is used to produce an economically viable product which could reduce the cost of a CCS system. One option is to use the sequestered CO2 as a heat extraction fluid in sedimentary basin geothermal reservoirs (CO2-Geothermal); CO2 extracts heat more efficiently than naturally existing geo-fluid (e.g., brine).2 CO2-Geothermal would require construction of a geothermal power plant in addition to the infrastructure requirements of CCS. The viability of CO2-Geothermal and CCS in saline aquifers will depend on the infrastructure needed to capture, transport, and inject CO2 from point sources into reservoirs. Despite the additional costs for building and operating a CO2-geothermal power plant, CO2-Geothermal systems could offset the costs of CCS-Saline through the sale of the electricity generated from the geothermal energy.
To compare the viability of CCS-Saline and CO2-Geothermal, we used the SimCCS (scalable infrastructure model for CCS) geospatial-optimization, engineering-economic model3 to determine the infrastructure requirements and supply curves for each technology. SimCCS optimizes integrated CCS networks by deciding where and how much CO2 to capture, where to build pipelines, and where and how much CO2 to inject into the reservoir. We adapted SimCCS to include the levelized cost of electricity for CO2-Geothermal power plants, which will depend on heat flux and aquifer temperature, permeability, porosity, depth, thickness, and CO2 storage capacity. In an application in Colorado and Louisiana, we collected geothermal, aquifer, and CO2 storage data from the National Geothermal Data System and NATCARB. We chose Colorado and Louisiana as case studies for comparing CO2-Geothermal and CCS-Saline due to the presence of a relatively high heat flux in the Denver and Gulf Coast Basins, aquifers that are capable of storing substantial amounts of CO2, and coal-fired power plants present within the state. CO2 emission rates and locations of coal-fired power plants in Colorado and Louisiana were compiled from EPA data. The costs of CO2 capture at power plants were estimated using the Integrated Environmental Control Model. The costs for CCS-Saline were used as a baseline to compare the supply curves and determine the efficacy of CO2-Geothermal.
The results show that CO2-Geothermal could be profitable and substantially reduce the cost of CCS-Saline systems. CO2-Geothermal is first deployed where storage reservoirs have a higher heat flux resulting in more centralized networks, whereas the networks for CCS-Saline are more decentralized. The results also show that the viability of CCS-Saline and CO2-Geothermal varies with the CO2 storage rate. These results plus future detailed cost and network estimates will be helpful for planners and policy makers to compare technologies such as CCS-Saline and CO2-Geothermal and make informed decisions on CO2-reduction technologies and trajectories.
This project is funded by the U.S. National Science Foundation Sustainable Energy Pathways program (1230691).
(1) IPCC. Climate Change 2014: Mitigation of Climate Change. Contribution of Working Group III to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change; Edenhofer, O., Pichs-Madruga, R., Sokona, Y., Farahani, E., Kadner, S., Seyboth, K., Adler, A., Baum, I., Brunner, S., Eickemeier, P., et al., Eds.; Cambridge University Press: Cambridge, United Kingdom and New York, NY, USA, 2014. (2) Adams, B. M.; Kuehn, T. H.; Bielicki, J. M.; Randolph, J. B.; Saar, M. O. A comparison of electric power output of CO2 Plume Geothermal (CPG) and brine geothermal systems for varying reservoir conditions. Appl. Energy 2015, 140, 365–377. (3) Middleton, R. S.; Bielicki, J. M. A scalable infrastructure model for carbon capture and storage: SimCCS. Energy Policy 2009, 37 (1), 1052–1060.