The rising potential of competitive solar desalination

Recent advances in solar-cell technology and membrane-separation technology do promise the economic viability of distributed seawater and brackish-water solar desalting systems in the near future. Reverse osmosis desalting processes driven by photovoltaic solar electricity can have the potential of displacing fossil fuel and curbing the rise of CO2 in the environment. This paper models desalination by spiral-wound RO membrane modules driven by solar-to-power photovoltaic converter panels with the purpose of revealing the economic potential of the combination. The paper then investigates the variability of the cost of desalted water with the major efficiency parameters of the desalting process and of the solar-to-power conversion process given water product rate, initial salt content, provisional reject brine salt content, design solar intensity and solar duration. Systems are generated by grouped input parameters of interest to the unit costs of solar power and product water. Runs covering a wide range of system input parameters are made and sample results are presented. The results already show two designs close to competitiveness. As fuel prices rise and/or technology advances, competitiveness becomes more assured. The obvious statement that high-efficiency solar and high efficiency desalting processes are keys to competitive solar desalination within the constraint of cost-effectiveness is confirmed in this study. The study also proposes a dimensionless number for RO membranes that may be useful.