Powering agricultural Internet of Things (IoT) sensors scattered across vast farmlands is challenging. Significant obstacles are faced for smart agriculture. The sensors track and report essential data like GPS coordinates, moisture levels, temperatures, soil acidity, nutrient concentrations and pest invasions. There are several solutions available including long-life batteries, solar panels and wind generators, but efficiency is questioned. Researchers at Tennessee Technological University in Cookeville have developed an innovative approach. The team claims to revolutionize the segment by sending electric power directly through the soil.
The through-the-soil (TTS) system is a theoretical idea, but researchers have successfully used it to power remote sensors and low-power LoRa radios. Their setup was powered by a mobile solar panel array and it roughly consumed 0.1 kilowatt-hour per day. The cost was just over a penny daily at retail rates.
The TTS system mainly comprises of three main components. These are power transmitter, some power receivers and multiple sensor modules. The test network linked four sensor packs and each contained a microcontroller, a LoRa network integrated circuit, a capacitor for power bursts, and soil sensors for moisture and temperature. The sensor modules required a combined total of 0.8 watts. The transmitter initially drew more power. However, it later optimized from 500 W to 250 W. the daily consumption was thereafter reduced to 0.1 kWh.
The concept basically involves a coupled circuit formed from the transmitter and receivers. Power is sent deep into the ground at the transmitter. The power is drawn up by the receivers. The transmitter includes a surface electrode and a bottom electrode. The surface electrode is a 15-meter steel well casing and the bottom electrode extends to 90 meters underground. Two rods are driven into the ground at each receiver. These are connected to the sensor module. Voltage is adjusted based on the spacing between these electrodes.
