Practical minimum energy use of seawater reverse osmosis

Abstract

Increasing the energy efficiency in seawater reverse osmosis (SWRO) is crucial to address worsening climate change and water scarcity. This study uses data from 39 facilities and detailed modeling to identify configurations for conventional, state-of-the-art, and practical minimum energy use. Performance benchmarks for pump efficiency, membrane permeability, membrane spacer mass-transfer coefficient, and pre- and post treatment were developed. Current systems use substantially more energy than the thermodynamic least work; 69% of this excess energy can be eliminated using state-of-the-art methods, and 82% with future technologies like batch reverse osmosis (RO). Additionally, isobaric energy recovery devices (ERDs) can save significant energy in conventional designs. We also map out the impact on energy of a wide range of operating conditions, including salinity, water flux, and water recovery. The most impactful high-efficiency solutions include using batch and semi-batch configurations, using the most efficient pumps, and operating at lower flux.