Wireless Power for Buried Sensors

Enables Continuous, Battery-Free Operation of Underground Sensor Networks Using Low-Frequency Energy Transfer

This wireless power transfer technology enables continuous operation of underground sensor networks using low-frequency electrodynamic transmission. Modern precision agriculture relies on distributed IoT sensor nodes to monitor soil conditions, crop health, and environmental factors, but these buried devices are difficult to access and require a dependable, long-lasting power source. Conventional batteries can supply energy, but must be replaced frequently, driving up labor costs and causing system downtime. Wireless power transfer (WPT) offers a more sustainable way to recharge battery-powered devices. However, traditional inductive WPT cannot deliver energy through wet soil due to electromagnetic absorption.

Researchers at the University of Florida developed a low-frequency wireless power transfer system that operates at sub-kilohertz frequencies and uses low-cost receivers to deliver power to underground sensors and communication modules. By operating below 1 kHz, the system avoids attenuation and safety concerns that limit conventional inductive solutions, while enabling deployable and scalable systems.

Application

Electrodynamic wireless power transfer for underground sensors and communication modules in smart-farm and field-monitoring networks

Advantages

• Delivers uninterrupted operation of buried sensors, reducing or eliminating battery-replacement cycles
• Scales output power by adding multiple receivers, supporting larger underground sensor arrays
• Uses ultra-low-cost coreless DC-motor hardware as the receiver, reducing manufacturing costs
• Operates below 1 kHz, minimizing electromagnetic attenuation and meeting safety constraints in agricultural environments
• Demonstrated power transfers up to 0.5 meters

Technology

This electrodynamic wireless power transfer system delivers usable energy to underground sensors and communication modules without wired connections. A low-frequency transmitter generates a sub-1kHz magnetic field that penetrates soil, moisture, and nearby metal structures with significantly lower attenuation than conventional high-frequency inductive systems. The architecture supports additive power scaling by deploying multiple receivers within the same field. For example, three receivers can provide a combined 182 mW DC, for denser underground sensor networks. The low-frequency operation, together with simple, mass-producible receiver hardware, makes the system well-suited for large-scale smart agriculture and other underground monitoring applications.