Direct energy recovery system for membrane capacitive deionization

Abstract

Capacitive deionization (CDI) is a water desalination technology using an electrical double layer based on non-faradaic process. One of the powerful advantages of CDI compared to other desalination technologies is that the energy consumed to desalinate can be partially recovered. In this study, we constructed the direct energy recovery system in a membrane capacitive deionization (MCDI) cell with a buck-boost converter and investigated the energy recovery ratio (recovered energy/consumed energy) under various operational conditions. As significant results, the higher energy recovery ratio was achieved with longer charging time and higher charging voltage in constant voltage (CV) charging and with lower charging current and higher concentration in constant current (CC) charging. These results revealed that the salt adsorption capacity plays an important role in the energy recovery process and that constant current charging is more favorable for energy recovery than constant voltage charging. This study is expected to provide a comprehensive guide for the construction and operation of the actual energy recovery system for enhancing energy efficiency in MCDI process.