Distributed Desalination using Solar Energy: A Techno-economic Framework to Decarbonize Nontraditional Water Treatment

Abstract

Desalination of nontraditional waters (e.g., agricultural drainage, brackish groundwater, industrial discharges, etc.) using renewable energy sources offers a possible route to transform our incumbent linear consumption model (discharge after use) to a circular one (beneficial reuse). This transition will also shift desalination from large-scale centralized coastal facilities towards modular distributed treatment plants (~1000 m3/day) in inland locations. This new scale of desalination can be satisfied using solar energy to decarbonize water production, but additional considerations, such as storage to address intermittency and inland brine management to address high disposal costs, become important. In this work, we evaluate the levelized cost of water or LCOW for 16 solar desalination technologies (with different generation–storage-desalination–brine management subsystems) at 2 different salinities corresponding to nontraditional sources. For fossil fuel-driven desalination plants at the distributed scale, we find that zero liquid discharge is economically favorable to inland brine disposal. For renewable desalination, we discover that (i) solar-thermal energy is better suited to both membrane and thermal desalination plants compared to photovoltaics largely due to the low cost of thermal storage, and that (ii) energy storage, despite its higher cost, outperforms water storage on a levelized basis as the latter has a low utilization factor with intermittently operated desalination plants. The analysis also yields a promising outlook for the LCOW of solar desalination by 2030 as the costs of solar generation and energy storage decrease to meet the U.S. Department of Energy targets. Finally, we highlight subsystem cost and performance targets for solar desalination to achieve cost parity with fossil fuel-driven water treatment.