Acoustic power delivery to pipeline monitoring wireless sensors

Abstract

The use of energy harvesting for powering wireless sensors is made more challenging in most applications by the requirement for customi zation to each specific application environment because of specificities of the availab le energy form, such as precise location, direction and motion frequency, as well a s the temporal variation and unpredictability of the energy source. Wireless pow er transfer from dedicated sources can overcome these difficulties, and in this work, the use of targeted ultrasonic power transfer as a possible method for remote powering o f sensor nodes is investigated. A powering system for pipeline monitoring sensors is described and studied experimentally, with a pair of identical, non6inert ial piezoelectric transducers used at the transmitter and receiver. Power transmission of 18 mW (Root6Mean6Square) through 1 m of a 118 mm diameter cast iron pipe, wi th 8 mm wall thickness is demonstrated. By analysis of the delay between tran smission and reception, including reflections from the pipeline edges, a transmission speed of 1000 m/s is observed, corresponding to the phase velocity of the L(0,1) a xial and F(1,1) radial modes of the pipe structure. A reduction of power delivery with water6filling is observed, yet over 4 mW of delivered power through a fully6filled pipe i s demonstrated. The transmitted power and voltage levels exceed the requirements fo r efficient power management, including rectification at cold6starting conditions , and for the operation of low6power sensor nodes. The proposed powering technique may a llow the implementation of energy autonomous wireless sensor systems for monit oring industrial and network pipeline infrastructure.