A Self-Powering Wireless Environment Monitoring System Using Soil Energy

Abstract

This paper presents a self-powering wireless environment monitoring system using renewable and cost-efficient soil energy. The D-size (55.8 cm $^{3})$ soil energy cell with carbon and zinc electrodes can produce $\sim 60$ –100 $\mu \text{W}$ , depending on the water contents and microbial reactions in the soil. The $RC$ circuit model of a soil cell is proposed for understanding the electrical characteristics of the cell. The wireless sensing system, including temperature and air moisture sensors, a custom low-power capacitive sensor readout silicon chip, a microcontroller, and a Bluetooth low-energy transmitter, is demonstrated for long-term environmental monitoring solely by the fabricated D-size soil cell. The capacitive sensor readout chip is fabricated in a 0.18- $\mu \text{m}$ CMOS process and only consumes 3 $\mu \text{W}$ . The capacitance readout range is 160–200 pF. The total power consumption of the wireless temperature and air moisture monitoring system is $\sim 20~\mu \text{W}$ and 1 mW in the sleep mode and the active wireless data communication operations, respectively. The new technology can enable remote field environment monitoring with less labor-intensive work and battery replacement.