2019 AAPG Annual Convention and Exhibition:

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Building a Geothermal Future on a Sedimentary Foundation


Geothermal energy from sedimentary basins has emerging possibilities that speak to both a new future for sedimentary sciences and a new and important role for sediments in the emerging market for renewable energy. These opportunities however are not necessarily linked or limited to conventional views of geothermal energy extraction. This is the primary finding of the SedHeat initiative. The SedHeat initiative is a Research Coordination Network funded by the National Science Foundation to explore the potential for sustainable geothermal energy from sedimentary basins. The network includes over 300 members from academia and industry dedicated to identifying and overcoming the challenges for economic extraction of geothermal energy from sedimentary basins. The group spans the fields of geology, engineering, economics, social sciences, and education. The group has come to some conclusions over the span of its current six years. First, conventional geothermal power extraction is now possible from sedimentary basins because of new technologies in heat-to-electric conversion. Most conventional geothermal energy depends on flash steam power, which depends on very high heat levels that are rare in sedimentary basins. The newer Rankin-cycle generators are able to run fluids with temperatures below 200 degrees Celsius, temperatures more common in sedimentary basins. They can do so at the current margins of economic viability, and are becoming increasingly competitive. Second, much of the domestic and commercial energy consumed is used to heat spaces and fluids. Upscaling of direct heating systems to manage large infrastructure from large-flow and deep-basin wells is already initiating and has promise for future expansion. Third, the Earth is a good battery. Growth of renewables like solar and wind energy are severely hampered by their intermittent nature. Their future use depends on megawatt-scale energy storage systems that thusfar have not emerged. Coupling of geothermal and solar systems is an encouraging solution. Solar energy is stored in deep sedimentary basins through injection of water superheated by thermal solar systems. The heat is later retrieved as stored base-load geothermal energy. The marginal lower heat of most sedimentary-basin geothermal systems is spiked for maximum output. The solar lost to non-demand periods is smoothed into peak demand times. Two problems with two renewables are solved by linking them together. Each of these options can be applied by expanding existing technologies. Each addresses the push for carbon-neutral energy and gives sedimentary science a large space to occupy in the emerging global renewables market. These speaks to a deep relevance of sedimentary basins and sedimentary science in a currently emerging future.