Centrifugal reverse osmosis: A novel energy-efficient desalination approach with mass transfer-controlled analysis

Centrifugal reverse osmosis (CRO) is an emerging desalination method that promises significant energy efficiency over conventional reverse osmosis (RO) by spatially varying pressure via module rotation, aligned with the thermodynamic minimum energy requirements. Many existing desalination studies rely on an idealized thermodynamic equilibrium-controlled (TEC) approach, assuming infinite permeability. This study employs a more realistic mass-transfer controlled (MTC) approach to characterize single-stage CRO and RO systems across a wide range of disk-shaped membrane diameters (0.5 – 2.0 m), permeabilities (1 – 4 LMH/bar), salinities (1 – 35 g/L), feed flow rates (0.01 – 0.2 GPM), and recovery rates (up to 70 %). The MTC approach reveals substantial deviations from TEC predictions, particularly in CRO energy savings, and highlights performance sensitivity to operating conditions. At a 50 % seawater recovery rate, CRO's net specific energy consumption (SECnet) is 31 % lower than RO under the idealized TEC approach (Krantz and Chong [1]). However, under the MTC method with a single 0.5 m-diameter membrane (4 LMH/bar permeability), the reduction is 16 % and 6 % at flow rates of 0.05 and 0.1 GPM, respectively. Achieving minimal energy consumption in both RO and CRO systems requires careful selection of the minimum-energy membrane area or permeability. Notably, the minimum-energy membrane area required for CRO is larger than that for conventional RO. At fixed flow and recovery rates, a larger module lowers the net specific energy consumption by reducing the required transmembrane pressure, while permeation per unit area (flux) decreases.