Autonomous operation and maintenance of small-scale PVRO systems for remote communities

Abstract

Solar-powered reverse osmosis desalination (Photovoltaic-powered reverse osmosis [PVRO]) is a technically feasible method of providing fresh water to many remote communities with saline water sources. To be practical, these systems must be well operated and maintained by non-experts. Their productivity is a complex function of their locations, water chemistry and demand, and the solar radiation history at their locations, which is quite variable with time. A key aspect of the maintenance program is the cleaning of the reverse osmosis (RO) membranes, including system flushing and chemical cleaning. Guidelines for cleaning from membrane manufacturers do not consider the complex, variable operating conditions for these small solar-powered systems. Local operators do not have the expertise to determine how and when cleaning should be done. While cleaning will generally improve clean water production, it is costly, requires the system to be shut down, and uses some of the clean water produced. Here, simple, physics-based models of RO membrane fouling and remediation are used to find maintenance schedules that maximize water produced by a small-scale PVRO system under deterministic conditions, such as found in large RO plants using conventional grid power. However, it is shown that for small PVRO systems working in remote locations, the large uncertainties have a significant impact on optimal cleaning schedules.

Keywords:

• Solar-powered reverse osmosis
• Maintenance
• Fouling
• Remediation

Acknowledgments

The support of the W.K. Kellogg Foundation is acknowledged as is the United States Department of Defense SMART Scholarship Program for Ms Kelley’s graduate studies. Also acknowledged are the important technical contributions of Prof. Amy Bilton.

Notes

Presented at the Conference on Desalination for the Environment: Clean Water and Energy 11–15 May 2014, Limassol, Cyprus