Electrodialytic Energy Storage System: Permselectivity, Stack Measurements and Life-Cycle Analysis

Reverse electrodialysis and electrodialysis can be combined into a closed energy storage system, allowing for storing surplus energy through a salinity difference between two solutions. A closed system benefits from simple temperature control, the ability to use higher salt concentrations and mitigation of membrane fouling. In this work, the permselectivity of two membranes from Fumatech, FAS-50 and FKS-50, is found to be ranging from 0.7 to 0.5 and from 0.8 to 0.7 respectively. The maximum unit cell open-circuit voltage was measured to be 115 +/- 9 mV and 118 +/- 8 mV at 25 degrees C and 40 degrees C, respectively, and the power density was found to be 1.5 +/- 0.2 W muc-2 at 25 degrees C and 2.0 +/- 0.3 W muc-2 at 40 degrees C. Given a lifetime of 10 years, three hours of operation per day and 3% downtime, the membrane price can be 2.5 +/- 0.3 $ m-2 and 1.4 +/- 0.2 $ m-2 to match the energy price in the EU and the USA, respectively. A life-cycle analysis was conducted for a storage capacity of 1 GWh and 2 h of discharging. The global warming impact is 4.53105 kg CO2 equivalents/MWh and the cumulative energy demand is 1.61103 MWh/MWh, which are 30% and 2 times higher than a lithium-ion battery pack with equivalent capacity, respectively. An electrodialytic energy storage system reaches a comparable global warming impact and a lower cumulative energy demand than a lithium-ion battery for an average life span of 20 and 3 years, respectively.