Geothermal Regional Water Resource Assessment

Abstract

With a potential threefold increase in geothermal electricity generation by 2035, geothermal energy is increasingly recognized for its potential to reduce carbon emissions (EIA 2011a). Energy and environmental analyses are critical to developing a robust set of geothermal energy technologies that meet future demand. Previous work has summarized what is currently known about the life cycle fresh-water requirements of geothermal powergenerating systems and the water quality of geothermal waters. This paper builds upon that work, presenting an assessment of freshwater demand for future growth in utility-scale geothermal power generation. The approach used combines a geothermal supply curve with an analysis of life cycle water consumption for geothermal systems and presents consumption information according to resource type, levelized cost of energy, and potential growth scenarios. Four resource types were considered: identified hydrothermal, unidentified hydrothermal, near-field enhanced geothermal systems (EGSs), and deep EGSs. Near-field EGS resources can significantly impact overall water demand for geothermal resources despite contributing a relatively small percentage of the potential generation capacity in most states evaluated. Similarly, as the electricity generation potential increases along the supply curve, the potential water consumption increases at a faster rate because the more capital- and water-intensive EGS technologies, with higher costs, can be developed. When realistic geothermal growth scenarios were analyzed to evaluate the relative amount of additional water demand compared with additional electricity generation, the results were mixed. In some states, the growth in power generation exceeded the growth in water consumption, resulting in a decline in overall water intensity of electricity generation, while in others the opposite was true. In cases where growth in geothermal systems increased the water intensity of electricity generation, it was observed that baseline water intensity was already significantly below the national average, potentially indicating existing water stress. The results highlight the fact that as geothermal electricity generation continues to grow, it will be important to explore alternatives to freshwater resources that are available to meet increased water demand. Potential resources include geofluid reuse from geopressured geothermal resources, water produced from oil and gas activities, water extracted from carbon capture and sequestration projects, and saline groundwater resources.