Investigation of Geothermally Sourced Combined Power and Freshwater Generation Systems

Abstract

To address the concurrent water and energy shortage issues regions where geothermal sources are abundant, three geothermally sourced combined power and freshwater generation technologies are investigated. Two of them are based on traditional power generation systems, including a steam system (SS) and a single flash system (SFS). The other one is a proposed trilateral flash system (TFS). Instead of focusing solely on their power generation potentials as previous geothermal exploitations did, the condensation process which produces desalinized freshwater is particularly investigated. To obtain a comprehensive evaluation, system performance under various geothermal wellhead conditions have been considered and compared. Results indicate that, for a typical liquid-dominated well, SS has absolute power generating advantage over SFS and TFS under low wellhead pressure and high wellhead vapor quality conditions. However, the TFS shows more stable power-generating and freshwater-generating performance when the wellhead condition varies, especially when the vapor quality gets lower. Efficiency of the total-flow turbine of TFS determines its system power potential. A turbine efficiency of 50% enables TFS to obtain comparable specific power with traditional power systems. Moreover, fresh water generation is a distinct advantage of the TFS, qualifying it a promising choice in remote arid geothermal terrains for both power and freshwater generation.