Integration of an atmospheric solid oxide fuel cell - gas turbine system with reverse osmosis for distributed seawater desalination in a process facility

The integration of a hybrid solid oxide fuel cell - gas turbine (SOFC-GT) system and reverse osmosis (RO) plant is evaluated thermodynamically and economically to enhance power generation and desalinate seawater on-site in a coastal energy-intensive industrial facility in the Persian (Arabian) Gulf. The power and fresh water co-generation scheme is based on the conversion of SOFC-GT exhaust thermal power into electrical work by a bottoming organic Rankine cycle (ORC) to drive the desalination high pressure pump. Seven ORC fluids are evaluated in terms of energetic and exergetic performance, as well as system size indicators. Depending upon the organic fluid selected, the net electrical power output generated from the exhaust of a 25 MWe hybrid SOFC-GT plant ranges from 1.2 to 2.4 MWe at an overall exhaust gas heat recovery efficiency of approximately 8-16% for R245fa and toluene, respectively. Compared with an existing standard GT cycle, the integrated SOFC-GT-toluene ORC-RO system enhances exergy efficiency by approximately 29%, while producing 494 m3/h of fresh water. The avoided purchase of fresh water, natural gas, and environmental emissions could generate net annual operating cost savings of 8-21 million USD based on subsidized and unsubsidized gas and water prices, respectively, and would become profitable within three to five years.