Wireless Sensor Power Supply Based on Eddy Currents for Structural Health Monitoring

To monitor stress levels inside both concrete and rebars, structural health monitoring systems utilize sensors integrated within reinforced concrete. These sensors can be powered wirelessly using inductive power transfer (IPT) technology, effectively negating the need for batteries with their limited lifespans. However, powering sensors through IPT proves inefficient and challenging due to the presence of eddy currents induced in the rebar loops, which significantly impact power transfer. This article presents an IPT system that utilizes these inherent eddy currents to wirelessly power sensors near the rebars. The proposed IPT system employs the loops in rebar arrays as relay coils, and thereby enables sufficient power to be harvested by a tiny receiver coil. A mathematical model based on an equivalent circuit for magnetically coupled rebar loops is presented to investigate and optimize the system's performance. Moreover, experimental results of a 5-V/2-W output prototype with a 10-cm concrete gap are presented to demonstrate the validity of the proposed method.