Design and Energy-Balance Assessment of Adaptive Power Management for a Solar-Powered IoT Smart Buoy
Autonomous marine Internet-of-Things (IoT) platforms must preserve sensing and telemetry functions under a limited and weather-dependent energy supply. This paper develops an energy-aware power-management assessment for a multi-parameter smart buoy using only the implemented design parameters and field records of the prototype. The platform combines a 20-Wp photovoltaic array, an MPPT charge controller, a 12-V 12-Ah VRLA battery, an LM2596 conversion stage, a multi-sensor acquisition node, GNSS, microSD storage, and Iridium Short Burst Data communication. A datasheet- and design-based operating-state model estimated 46.62 Wh/day at the 5-V load side for a nominal 30-min cycle and 52.98 Wh/day from the battery when a conservative 88% DC–DC efficiency is included. With 98% MPPT efficiency, analytical solar input for 5, 4, and 2 peak-sun-hours/day was 98, 78, and 39 Wh/day, corresponding to energy balances of +45, +25, and −14 Wh/day. The 72-Wh usable battery window yields a theoretical solar-free autonomy of approximately 1.36 days. A voltage-threshold policy maps the system into normal, power-saving, emergency, and critical-shutdown states. During a 2-h-18-min coastal observation phase, 47 battery records remained between 12.07 and 12.19 V (mean 12.13 V), with a net start-to-end change of −0.07 V and no power-induced interruption. The field evidence demonstrates short-duration supply continuity, while the daily energy-neutrality result remains an analytical design estimate that requires multi-day current, irradiance, and charging measurements for validation.