Energy consumption analysis of constant voltage and constant current operations in capacitive deionization

a b s t r a c t a r t i c l e i n f o Article history: Received 2 June 2016 Received in revised form 9 August 2016 Accepted 15 September 2016 Available online xxxx We report our studies to compare energy consumption of a CDI cell in constant voltage (CV) and constant current (CC) operations, with a focus on understanding the underlying physics of consumption patterns. The comparison is conducted under conditions that the CV and CC operations result in the same amounts of input charge and within identical charging phase durations.Wepresent two electrical circuitmodels to simulate energy consumption in charging phase: one is a simple RC circuit model, and the other a transmission line circuit model.We built and tested a CDI cell to validate the transmission line model, and performed a series of experiments to compare CV versus CC operation under the condition of equal applied charge and charging duration. The experiments show that CCmode consumes energy at 33.8 kJ per mole of ions removed, which is only 28% of CVmode energy consumption (120.6 kJ/mol), but achieves similar level of salt removals. Together, the models and experiment support our major conclusion that CC is more energy efficient than CV for equal charge and charging duration. The models also suggest that the lower energy consumption of CC in charging is due to its lower resistive dissipation. © 2016 Published by Elsevier B.V.