Some communities in the United States lack access to clean drinking water. This is problematic because pathogens in unfiltered freshwater cause illness. Current purification methods are costly and often require access to traditional electricity infrastructure. Solar pasteurization is an alternative that maintains water at a desired temperature for a specific period to inactivate pathogens. The goal was to design a solar water pasteurization system that used readily available parts, had a low capital cost, and was powered only by a photovoltaic cell. A photovoltaic-powered density-driven solar water pasteurization system was designed and developed to target pathogens categorized as high-health-risk, according to the World Health Organization (WHO). For each pathogen, thermal inactivation data were collected and used to model the temperature-time relationship for 1-log reductions. Based on the model, an operating point of 80℃ for 500s was selected to achieve the desired reduction for all pathogens. The final design uses a reservoir system to maintain the water level of the supply. Dirty water travels from the reservoir to a heat exchanger, where it is preheated before entering a circulation loop. A resistance-based heater is located in the loop, where water is heated to 80℃. Because density decreases with temperature, the water rises through a tube connected to the loop and enters a holding tube. Water is held at 80℃ for 500s, then released into the heat exchanger to heat incoming water. Once water exits, it travels to a storage volume for on-demand use.
Acknowledgements: I would like to thank Professor Hodgson for his help and guidance throughout the design and development of my project.