Securing Water in a Changing Climate: A Transient Solar Desalination Model for the Sundarbans, Bangladesh

ABSTRACT Solar‐powered reverse osmosis (RO) desalination can address water security for coastal communities facing saltwater intrusion, but detailed models that simulate real performance under varying weather and salinity conditions are limited. This study develops and validates a transient photovoltaic (PV)‐RO simulation framework using hourly irradiance, temperature, and salinity data from the Sundarbans, Bangladesh, where seasonal salinity varies nearly 18‐fold (1.4–24.8 ppt). Following steady‐state validation of the RO module, we extended it to a dynamic model simulating 8760 hourly timesteps. Our analysis reveals a critical design bottleneck: monsoon‐driven peak salinity coincides with severely diminished solar irradiance. This mismatch collapses water production by 85%–90% while spiking energy demand to 100–120 kWh/m 3 . Sensitivity analyses indicate that irradiance, PV array size, and system pressure primarily drive water output, whereas drivetrain efficiency dictates operating costs. Furthermore, Monte Carlo simulations quantifying design uncertainty demonstrate that under 95th‐percentile adverse conditions, production drops to 0.227 m 3 /h with an energy requirement of 582 kWh/m 3 . Ultimately, these findings identify membrane permeability and active area as the binding constraints on system productivity when multiple uncertainties compound.