IoT Buoy for Water Quality Monitoring : Design, prototype, and test of a solar-powered, LoRaWAN-based WQM system for the smart city

Abstract: Although water is incredibly abundant on Earth, only 2.5 % of the water reserve is freshwater, and one third of the world’s population lacks safe drinking water. Water quality monitoring (WQM) is thus a crucial asset to safeguard this invaluable resource. Gaining popularity in the 1960s, WQM has since evolved from a lab-based, labour-intensive program to an increasingly automated operation. Today, autonomous sensors automatically assess water quality, albeit with surpassed technology, complex procedures, and expensive equipment. This thesis presents a next-generation, IoT-based WQM system, capable of unparalleled high-frequency data collection at a fraction of the cost of present-day solutions, that operates via The Thing Network’s public LoRaWAN connectivity. The system is validated through a lightweight prototype buoy, which is deployed on a 14-days-long campaign in the lakes of Stockholm. The study concludes that (i) The Things Network is a promising backbone for monitoring applications in the smart city, with an estimated current 57 % coverage of Stockholm; (ii) IoT devices can harvest sufficient solar energy to deliver 30–60 messages/h all year round even at high latitudes; (iii) IoT-based WQM has the potential for unprecedented resolution, energy-efficiency, and cost-effectiveness compared to traditional industrial-grade, cellular-based systems.