Solar Station for an Off-the-Grid Air Quality Sensor System

Air quality monitoring is a rapidly growing area of citizen science, or community science (CS), thanks to the availability of low-cost sensors. Contributing to a crowdsourced data platform (e.g., http:// purpleair .com/ map) is usually easy in urban areas, where there is access to uninterrupted electricity and wireless internet (Wi-Fi). However, there are sometimes security restrictions on Wi-Fi or a lack of exterior power outlets. Also, rural regions, particularly in low- and middle-income countries, often lack electricity and Wi-Fi continuity. RTI International has designed and distributed a solar power and Wi-Fi station that can adequately power both a small air quality sensor (e.g., PurpleAir PA-II) and a Wi-Fi hotspot to overcome these challenges. The station housing can accommodate a battery, a controller, and a cell phone or another type of Wi-Fi hotspot device. This paper discusses the need for such a station; a design for the current station, including parts list; suggestions for modifications in various use cases; and design factors to consider, including amount of sunlight per day, intended number of operational days under cloudy conditions, season, and total power requirements. This method is intended to be open source and a starting point for citizen scientists and CS projects.