Technoeconomic Analysis of Brackish Water Capacitive Deionization: Navigating Tradeoffs between Performance, Lifetime, and Material Costs

Capacitive deionization (CDI), a class of electrochemical separation technologies, has been proposed as an energy-efficient brackish water desalination method. Previous studies have focused on improving capacity and energy consumption through material (e.g., ion-selective membranes [IEMs], charged carbon) and operational modifications, but there has been no analysis that directly links lab-scale experimental performance to capital and operating costs of full-scale water production. In this study, we developed a parameterized process model and technoeconomic analysis framework to project capital and operating costs at the million gallon per day scale based on reported material and operational characteristics for constant current CDI with and without low ($20 m^-2)- and high-cost ($100 m^-2) IEMs. Using this framework, we conducted global sensitivity and uncertainty analyses for water price across the reported CDI design space. Our results show that the operating constraints of brackish water desalination lead to capital costs 2-14 times greater than operating costs (particularly for MCDI). While MCDI outperforms CDI, IEM prices dictate the threshold at which MCDI is more cost-effective. The high relative capital costs highlight the importance of achieving system lifetimes at 2 years or beyond. Last, we set performance and areal cost benchmarks for material-based CDI performance and lifetime improvements.