A Novel Ultralow-Power, Battery-Less BLE Plant Monitoring, and Energy Harvesting System

This paper presents the design, implementation, and experimental validation of a fully battery-less BLE-enabled plant monitoring system, powered by energy harvested from a plant–soil–electrode interface. The proposed system leverages the electrochemical potential difference between two dissimilar metal electrodes inserted in the soil to drive a low-power energy harvesting circuit. A Maximum Power Point Tracking (MPPT) strategy based on the Fractional Open Circuit Voltage method ensures optimal energy extraction across variable conditions. The harvested energy is stored in a small supercapacitor, which powers a BLE SoC performing environmental sensing and data transmission in periodic bursts. Experimental I–V and P–V characterizations were performed on five different plant species and multiple electrode combinations, with the Dieffenbachia Seguine plant coupled with copper/zinc electrodes achieving the highest power output of 47 μW. The system was able to complete a full sensing and BLE transmission cycle with a total energy requirement of 19.4 mJ, accumulated within approximately 6.9 minutes using a 4.7 mF storage capacitor. Acquired sensor data demonstrate the ability to harvest sufficient energy to support a periodic acquisition every 8 minutes of light and soil moisture values over time, validating the feasibility of autonomous and battery-less operation.