Empowering energy-aware task operations and timekeeping with intermittent sensor systems

Varying energy requirements and timekeeping issues faced by intermittent sensor systems are addressed by an Energy and Time Management Unit (ETMU) introduced in this work. This ETMU allows dynamic energy storage size and operating voltage adjustment to meet task energy requirements and startup times. It also includes an ultra-low power real-time clock (RTC) for accurate timekeeping. The ETMU is integrated into an intermittent sensor system for ultrasonic water flow measurements, using three energy harvesters and the LoRaWAN protocol for data transmission and time synchronization. Experimental results show efficient energy management of LoRaWAN communications, e.g. improved startup and charging time for LoRaWAN communication task, and precise timekeeping for data collection.