Economics of brine desalination for communities near the Salton Sea Geothermal Field, California, USA

This study analyzed the economic factors of geothermal energy source utilization for desalination and power generation near Salton Sea, California. Three following over-arching reasons provided impetus for this study: geothermal source temperature, drinking water needs, and aquifer quality. The Cost of Renewable Energy Spreadsheet Tool (CREST) Model was used to determine the feasibility of three major desalination processes with low and medium temperature geothermal sources as thermal and electrical energy sources. Electrical energy, produced by medium temperature geothermal sources (100–200 °C), was considered for desalination (water) only and desalination and power (water and power) schemes through ten different scenarios using different desalination plant capacities (20,000–30,000 m3/d) and specific energy demands (40–80 kWh/m3). Low-temperature geothermal source was considered for meeting the thermal energy requirements of MED desalination plant supported by grid electricity with four different scenarios, which include new wells (full-size and slim-hole) and existing wells (existing without modification and existing with brine reinjection). Results from the analysis show that low enthalpy geothermal wells provide cost-effective option for desalination only configuration supported by conventional electricity. Medium-temperature geothermal source provided an affordable cost scenario when water and power scheme was considered. It was noted that the majority of freshwater cost ranges were due to the geothermal energy costs which were 1.97–2.39 $/m3, 1.95–2.35 $/m3, 1.75–1.96 $/m3 and 1.66–1.77 $/m3, for new full-size geothermal wells, new slim-hole geothermal well, existing, and existing geothermal well reinjection stream options, respectively. When conventional electricity is considered for desalination, the energy costs varied between 0.52 and 1.14 $/m3 for new full size well option considering different desalination capacities (20,000–30,000 m3/d) and specific energy consumption vales (40–80 kWh/m3). Finally, the lowest freshwater cost option was still 50–100% higher than the conventional water supply options in the region. However, combining factors of high groundwater salinity and high geothermal resource availability suggested geothermal desalination option as an environmentally benign approach for this region.