Remote monitoring unit for solar home systems: a field trial

Solar home systems (SHS) can be utilised for electrification of areas for the 770 million people worldwide which do not have connection to a national electricity grid. SHS, comprised of a solar photovoltaic panel, charge controller, battery, and appliances, provide small amounts of power for household items such as charging phones, LED lights, radios, and televisions. The practical implementation of SHS in, typically, remote rural locations make asset monitoring, operation and maintenance of these systems difficult. For example, in one programme over 30 % of SHS implemented had some form of fault reported within the first 12 months of operation. This impacts the economics and reputation of the SHS supplier and is highly inconvenient to the user. However, the faults were difficult to analyse, as their symptoms were reported verbally in varying levels of detail. The ability to remotely monitor these systems in real time could help to improve their long-term performance and allow preemptive maintenance to be performed. Knowledge of the actual solar power generation and load provision on these systems helps a SHS supplier manage their assets and could help with the future development of lower cost and more efficient SHS. This paper introduces the design of a low-cost low-power data-logging device for remote monitoring of SHS. The logging unit monitors voltage, current, power and temperature sensors, stores this data locally and sends it to a cloud-based store, either using Wi-Fi or General Packet Radio Service (GPRS). The system can be installed in any area with GPRS reception or Wi-Fi and monitored from anywhere with an internet connection. The data is presented in interactive graphs and maps via an Internet of Things (IoT) web dashboard. Data from field trials of the remote monitoring unit on solar power systems in Zambia, Malawi and the UK is presented. This shows key issues, such as low battery state of charge, that can be used to inform customers when to reduce their loads and charge the battery.