NREL explores the potential of geothermal-powered membrane distillation

July 31, 2018 | Case Study

An area of growing interest in desalination is using geothermal energy to power the process. The underlying assumption is that geothermal energy could provide a constant source of stable "base-load" power for continuous, long-term periods. While initial efforts in the space have focused on thermal distillation processes like multi-effect distillation (MED) and multi-stage flash (MSF) that can be powered using the electricity produced from geothermal wells, recent efforts are finding use cases for harnessing low-temperature geothermal resources (around 90 °C) to directly power advanced thermal desalination processes. The U.S. Geological Survey estimates the potential beneficial direct use of heat from low-temperature (<90 °C) geothermal resources to be 46.5 gigawatts thermal (GWth).

Thermal desalination technologies have been widely used for seawater and industrial desalination. The largest installed base is in the Middle East, where a number of these plants are collocated with thermal power plants to utilize waste heat for the water treatment. Since thermal energy for desalination represents 30% to 40% of operating costs, the cost of producing water is generally 10% to 30% higher than that of reverse osmosis (RO), which is the key hurdle for the technology.