The configuration of reverse electrodialysis stacks utilizing ammonium bicarbonate solutions

The configuration of a reverse electrodialysis(RED)stack utilizing ammonium bicarbonate solution was optimized in order to improve the power output.The variation of energy efficiency was also analyzed.The results showed that a maximum power density of 0.85W/m2 was achieved with the use of five cell pairs and a spacer with a thickness of 0.2mm when ignoring the power consumption due to the electrode system.When the number of cell pairs ranged from 2to 8,the open circuit voltage,internal resistance and maximum power density all improved gradually with increasing number of cell pairs.Meanwhile,the number of cell pairs had a good linear relationship with both the open circuit voltage and internal resistance.However the RED stack had a reduced power output when the number of cell pairs was over 8.For two spacers with the same type,the thinner one resulted in a decreased internal resistance and thus increased the power output.For the spacers with the same thickness,the one with a compact woven structure performed better.Energy efficiency of the RED stack stabilized at about 30% during the experiment,which shows its promise for energy utilization.