Performance evaluation for a high temperature alkaline fuel cell integrated with thermal vapor compression desalination

Efficient electricity and freshwater production is a key focus of water-energy nexus research. The proposed system provides an integrated sustainable freshwater and electricity co-generation. This study is the first to integrate high-temperature alkaline fuel cells (AFC) with thermal vapor compression desalination (TVC) driven by steam ejectors. The proposed AFC works at an elevated temperature of 160 °C using concentrated potassium hydroxide as an electrolyte (KOH) to generate the required waste heat used by the TVC system. Meanwhile, the TVC system suggests a top brine temperature of 95 °C and a steam ejector with a 1.85 compression ratio operated at a motive steam pressure of 400 kPa. The thermal behavior of the hybrid system was modeled using MATLAB software. Furthermore, parametric analysis was applied to the proposed system to investigate system performance at different operating conditions, including AFC operating temperature, electrical current density, motive steam pressure, top brine temperature, and compression ratio. Results revealed that the AFC can produce a waste heat of 622.3 kW, where it is fed with oxygen obtained from air at a molar rate of 11.89 mol/s and hydrogen as fuel at a molar rate of 3 mol/s. The system performance was evaluated in terms of performance ratio, specific mass flow rate of cooling water, and specific evaporator area. Results showed that the integrated system achieves a performance ratio of 1.53, a specific cooling water mass flow rate of 3.58, and a specific evaporator area of 54.61 m2/(kg/s). Furthermore, increasing AFC current density caused an increased thermal efficiency and distillate flow rate. The AFC achieved maximum thermal efficiency and distillate flow rate of 88.56 % and 0.42 kg/s respectively at 1600 A/m2 current density. The used approach presents a sustainable solution for water and electricity issues in urban areas.