An alkaline fuel cell/direct contact membrane distillation hybrid system for cogenerating electricity and freshwater

Abstract

Abstract To reuse the exhaust heat from alkaline fuel cell for water purification, a new hybrid system that hybridizes a direct contact membrane distillation to an alkaline fuel cell is proposed. Including various irreversible losses, the models of alkaline fuel cell and direct contact membrane distillation are formulated in detail. Mathematical formulas of power output and energy efficiency for the proposed system are derived and further used as performance indicators. The effectiveness of hybrid system is demonstrated by comparing with the single alkaline fuel cell. Calculation results illustrate that the power output density and energy efficiency of hybrid system allow 144.58% and 144.55% larger than that of the stand-alone alkaline fuel cell, respectively. Moreover, a number of parametric studies are carried out to study how the performances of hybrid system are impacted by several key operation conditions and design parameters. Results show that larger feed water temperature, convective heat-transfer coefficients on feed side and permeate side, flow velocities of feed water and permeate water or pore radius of hydrodynamic membrane benefit the hybrid system performance. However, a larger hydrodynamic membrane thickness or permeate water temperature worsens the hybrid system performance.