TY - JOUR
T1 - Osmotic Ballasts Enhance Faradaic Efficiency in Closed-Loop, Membrane-Based Energy Systems
AU - Kingsbury, Ryan S.
AU - Coronell, Orlando
N1 - Publisher Copyright:
© 2016 American Chemical Society.
PY - 2017/2/7
Y1 - 2017/2/7
N2 - Aqueous processes for energy storage and conversion based on reverse electrodialysis (RED) require a significant concentration difference across ion exchange membranes, creating both an electrochemical potential and an osmotic pressure difference. In closed-loop RED, which we recently demonstrated as a new means of energy storage, the transport of water by osmosis has a very significant negative impact on the faradaic efficiency of the system. In this work, we use neutral, nonpermeating solutes as "osmotic ballasts" in a closed-loop concentration battery based on RED. We present experimental results comparing two proof-of-concept ballast molecules, and show that the ballasts reduce, eliminate, or reverse the net transport of water through the membranes when cycling the battery. By mitigating osmosis, faradaic and round-trip energy efficiency are more than doubled, from 18% to 50%, and 7% to 15%, respectively in this nonoptimized system. However, the presence of the ballasts has a slightly negative impact on the open circuit voltage. Our results suggest that balancing osmotic pressure using noncharged solutes is a promising approach for significantly reducing faradaic energy losses in closed-loop RED systems. (Figure Presented).
AB - Aqueous processes for energy storage and conversion based on reverse electrodialysis (RED) require a significant concentration difference across ion exchange membranes, creating both an electrochemical potential and an osmotic pressure difference. In closed-loop RED, which we recently demonstrated as a new means of energy storage, the transport of water by osmosis has a very significant negative impact on the faradaic efficiency of the system. In this work, we use neutral, nonpermeating solutes as "osmotic ballasts" in a closed-loop concentration battery based on RED. We present experimental results comparing two proof-of-concept ballast molecules, and show that the ballasts reduce, eliminate, or reverse the net transport of water through the membranes when cycling the battery. By mitigating osmosis, faradaic and round-trip energy efficiency are more than doubled, from 18% to 50%, and 7% to 15%, respectively in this nonoptimized system. However, the presence of the ballasts has a slightly negative impact on the open circuit voltage. Our results suggest that balancing osmotic pressure using noncharged solutes is a promising approach for significantly reducing faradaic energy losses in closed-loop RED systems. (Figure Presented).
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U2 - 10.1021/acs.est.6b03720
DO - 10.1021/acs.est.6b03720
M3 - Article
C2 - 28008760
AN - SCOPUS:85013311758
SN - 0013-936X
VL - 51
SP - 1910
EP - 1917
JO - Environmental Science and Technology
JF - Environmental Science and Technology
IS - 3
ER -