Off-grid photovoltaic-powered capacitive deionization for groundwater desalination in rural Africa

ABSTRACT In regions lacking centralized water supply and electricity grid connections, capacitive deionization (CDI) offers a promising approach with its modular and energy-efficient characteristics for low-salinity solutions. This research evaluates the feasibility of using a photovoltaic (PV)-powered CDI system as an off-grid, household-based water purification solution for groundwater desalination in rural Uganda. In this work, the CDI system was integrated with a PV system, comprising an ultrafiltration unit for pretreatment, a CDI stack for desalination, and a PV array for power supply. As evidenced by the performance analysis of the CDI stack in a single-pass mode, the system exhibited commendable desalination efficiency with a salt removal efficiency (>60%) and stable energy performance (0.110 ± 0.014 kWh/mol) observed under different influent conductivities (500–3,000 μS/cm). When applied to groundwater desalination, the CDI-based system successfully reduced the conductivity to meet Uganda's potable water standard (1,500 μS/cm), achieving a water recovery of 63%, and an energy consumption of less than 1.5 kWh/m3. Consequently, the CDI-based system effectively couples with the PV system to meet daily water needs solely through solar energy, demonstrating the practical implementation of innovative off-grid water desalination solutions in resource-constrained settings.