Designing a Wireless Solar Power Monitor for Wireless Sensor Network Applications

Wireless sensor networks (WSNs) are often deployed remotely; hence, typical disposable chemical batteries with limited lifetimes may not be suitable for powering the network. In such cases, photovoltaic (PV) systems that generate electricity from sunlight can serve as a better alternative energy source. The intensity of sunlight varies over time, and thus the rates at which the batteries in the PV system get charged also vary. Monitoring the charging and discharging currents and voltages of the batteries enables us to modify the operation of the system in order to improve its overall efficiency. Moreover, it enables us to detect any fault in the solar panel, battery, or network node. We have designed an independent, low cost, ultra-low power microcontroller-based wireless solar power monitor that can be plugged easily into a PV system. The monitor measures the currents and voltages across the panels, batteries, and the load, and periodically transmits these values through an independent wireless interface to a control center for observation and analysis. We have performed a power analysis of the monitor and learnt about the power consumption in its various states. The use of this power monitor should extend the overall life of the PV system and also minimize power failures in the WSN nodes powered by the PV system. This paper reports about the design of the power monitor as well as the results of our analyses.