Integrated Solar–Piezoelectric Hybrid Energy Harvesting with IoT-Based Monitoring: A Comparative Analysis of Reported Systems and a Unified Architecture

Hybrid energy harvesting that combines photovoltaic (PV) generation with piezoelectric footstep harvesting promises uninterrupted low-power supply in public spaces, but published prototypes use different tile designs, converters, monitoring schemes and reporting conventions, which makes them hard to compare. This paper critically consolidates three recent studies: an Arduino/ESP8266 solar–piezoelectric system with ThingSpeak monitoring, a footstep floor tile with a closed-loop buck converter, and a tracked-PV plus 48-sensor footstep system for DC loads. Their reported figures are normalised to common metrics (power per unit area, daily energy, and the piezoelectric share of total energy), and inconsistencies in the source data are identified. A unified architecture is then proposed in which a PV string and a piezoelectric tile array feed a common 12 V DC bus through independent converters, with a microcontroller and IoT gateway providing real-time monitoring and fault flagging. Using only values reported in the source studies, an analytical scale-up shows that a 30-tile array (60 Wh over 8 h) can supply a 5.4 W camera for about 11 h, but contributes only about 3–5% of the daily energy of a tracked PV panel of the class reported. The results indicate that piezoelectric tiles are best positioned as a supplementary and sensing-grade source, while PV remains the dominant energy contributor. Experimental validation of the proposed architecture is identified as future work.