Integrating a supercapacitor with capacitive deionization for direct energy recovery from the desalination of brackish water
Journal
Applied Energy
Journal Volume
252
Date Issued
2019
Author(s)
Abstract
The importance of energy recovered from desalination techniques has been of considerable interest because of increasing water scarcity and energy crises. Capacitive deionization (CDI), a promising desalination technology using pairs of carbon electrodes under an electric field, has an attractive advantage in that energy stored during the charging step for salt removal can be further recovered during the discharging step. In this research, an energy recovery system based on a four-switch buck-boost converter with variable frequency was successfully constructed to transfer electric energy from a CDI module to a supercapacitor. The effects of the influent NaCl concentration and the distance between two oppositely placed electrodes were investigated on both the desalination behavior and energy recovery performance. The experimental procedure involved a charging step for ion removal, stop-flow operation for energy recovery, and discharging step for electrode regeneration. For the desalination of a 10 mM NaCl solution, a deionization capacity of 10.1 mg g−1 and a total energy input of 0.09 kWh m−3 were obtained. Overall, as demonstrated, a higher energy recovery ratio was achieved with a higher influent NaCl concentration and a shorter distance between the two electrodes. Significantly, up to 49.6% of the energy stored in the CDI module while reducing the salinity of a 50 mM NaCl solution could be directly recovered, indicating that the energy recovery system based on a four-switch buck-boost converter shows superior performance. The utilization of CDI integrated with a supercapacitor in this work holds great potential in both low-energy-requirement desalination and high-efficiency energy storage. © 2019 Elsevier Ltd
Subjects
Capacitive deionization; Desalination; Energy recovery; Energy storage; Four-switch buck-boost converter
Other Subjects
Desalination; Electric current regulators; Electric fields; Electric switches; Electrodes; Energy policy; Energy storage; Recovery; Sodium chloride; Supercapacitor; Capacitive deionization; Desalination technologies; Energy recovery; Energy recovery system; Energy requirements; Experimental procedure; Four Switch Buck-Boost converters; Variable frequencies; DC-DC converters; brackish water; desalination; electrode; electronic equipment; energy efficiency; performance assessment; salinity; superconductivity
Type
journal article