Power generation by coupling reverse electrodialysis and ammonium bicarbonate: Implication for recovery of waste heat

Utilization of waste heat has attracted increasing attentions due to energy crisis and environmental problems. Efficiency of traditional thermodynamic cycles for waste heat conversion is limited by the temperature of heat sources. We propose here the concept of a novel waste heat conversion system, namely a thermal-driven electrochemical generator (TDEG), which comprises a reverse electrodialysis (RED) stack and a distillation column. By using thermally instable ammonium bicarbonate solutions as working fluids, waste heat can be converted to electricity. The feasibility of NH4HCO3 to generate electricity for TDEG was validated in a RED stack for the first time. Two important operating conditions influencing power output of RED stack, i.e. concentration of low concentration solution and flow rate of feed solutions were optimized to be 0.02 M and 800 mL/min, respectively. A maximum power density of 0.33 W/m2 was obtained for the specific RED stack. Ionic flux efficiency and energy efficiency under the optimal condition were 88% and 31%, respectively. The study lays a foundation for the establishment of the promising TDEG.

► The concept of a novel waste heat conversion system was proposed.
► Feasibility of NH4HCO3 to generate electricity in RED was proved for the first time.
► Two important operating conditions were optimized to obtain a maximum power density.
► Coupling NH4HCO3 with RED is promising for energy utilization.