Natural circulation solar thermal system for water disinfection

A system for the disinfection of water using solar energy with natural circulation (no electricity) is described. The system includes solar collectors, a self-adjusting closed circuit driven by buoyancy, and regenerative preheating. Design principles are outlined and performance under off-design seasonal operation is examined in several relevant locations. The system is intended for medium- and long-time operation in emergency areas. The analysis includes exergy balance and thermoeconomics. The productivity is evaluated (daily and seasonal) and the cost of purified water evaluated. The system is compared to the high-tech alternative of using a reverse osmosis unit driven by photovoltaics, and results to be competitive and less intensive in terms of maintenance skills and ease of operation.