CO2 Earth Storage: Enhanced Geothermal Energy and Water Recovery and Energy Storage

Mitigating climate change requires a range of measures, including increased use of renewable and low-carbon energy and reducing the CO2 intensity of fossil energy use. We present an approach designed to address the major deployment barriers to CO2 capture, utilization, and storage (CCUS) and utility-scale energy storage needed to maximize use of variable renewable energy and low-carbon baseload power. We use the huge fluid and thermal storage capacity of the earth, together with overpressure driven by CO2 storage, to harvest, store, and dispatch energy from subsurface (geothermal) and surface (solar, fossil, nuclear) thermal resources, as well as excess energy from electric grids. Permanent storage of CO2 enables the earth to function as a low-carbon energy-system hub. Stored CO2 plays three key roles: (1) as a supplemental fluid that creates pressure needed to efficiently recirculate working fluids that store and recover energy, (2) as a working fluid for efficient, low-water-intensity electricity conversion, and (3) as a shock absorber that allows diurnal and seasonal recharge/discharge cycles with minimal pressure oscillations, thereby providing enormous pressure-storage capacity, with reduced risk of induced seismicity or leakage of stored CO2. To assure safe storage pressures, a portion of the brine produced from the CO2 storage reservoir can be diverted to generate water. (C) 2017 The Authors. Published by Elsevier Ltd.