| Title | Geothermal Energy: The Energy-Water Nexus |
|---|---|
| Authors | Christopher HARTO, Jenna SCHROEDER, Lou MARTINO, Robert HORNER, and Corrie CLARK |
| Year | 2013 |
| Conference | Stanford Geothermal Workshop |
| Keywords | EGS, water, LCA, life cycle, environment |
| Abstract | Building upon a life cycle assessment (LCA) of geothermal systems, this paper examines the energy-water interactions and potential challenges faced by a growing geothermal industry. A LCA approach was used to estimate water consumption for a range of geothermal plant designs. The life cycle water consumption values were then used to explore geothermal growth scenarios to estimate potential regional water demands for new geothermal development. These water demands were then compared with metrics for water availability to identify areas where water related challenges are most likely to occur. Through this process a range of water-energy related challenges, trade-offs, and opportunities were identified. Dry cooling systems can significantly reduce water consumption for geothermal plants compared to wet or hybrid systems; however they come at a cost of an energy penalty that increases when power is the most valuable in the summer. Flash plants typically use condensate to run wet cooling systems, however this comes at a cost of reduced reservoir sustainability. Supplemental injection programs can extend the life of the reservoir but consume large quantities of water relative to other electric generation technologies. The large resource base for enhanced geothermal systems (EGS) represents a major opportunity for the geothermal industry; however, depending upon geology, these systems can be quite “thirsty” and require large quantities of make-up water due to reservoir losses. Identifying potential sources of compatible degraded or low quality water for use for make-up injection for EGS and flash systems represents an important opportunity to reduce impacts on fresh water resources. The importance of identifying alternative water sources for geothermal systems is heightened by the fact that a large fraction of the geothermal resources are located in areas already experiencing water stress. |