Reverse Electrodialysis in the Utilization of Waste Heat

Abstract

The desire for a secure, abundant, inexpensive, and environmentally friendly energy source has encouraged the pursuit of utilizing waste heat. Converting this waste heat to usable energy can be done with separation coupled reverse electrodialysis (RED). However, the efficiency of this process using NaCl and water is estimated to 0.007%. The objective is then to increase this efficiency and evaluate the feasibility of separation coupled RED. One way is to decrease power input by using ammonium bicarbonate as the solute, increasing the estimated efficiency to 0.2%. Alternatively, the power output of RED could be increased, by adjusting various parameters in a validated model. Specifically, a relationship between the residence time and the power output can be found. Unfortunately, the values for efficiency (0.76%) and power density (3.2 W/m2) are still very small for separation coupled RED, especially when compared to pressure gradient osmosis (PGO) using ammonium bicarbonate. This suggests that separation coupled PGO may be more attractive than separation coupled RED. Future work should then focus on examining the feasibility of PGO using ammonium bicarbonate through computational and experimental research.