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 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> ) soil energy cell with carbon and zinc electrodes can produce ~60-100 μW, 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-μm CMOS process and only consumes 3 μW. The capacitance readout range is 160-200 pF. The total power consumption of the wireless temperature and air moisture monitoring system is ~20 μW 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.