Piezoelectric energy harvester scavenging AC magnetic field energy from electric power lines

► We propose a piezoelectric energy harvester for scavenging energy from a power line based on the Ampere's law. ► The harvester employs a novel magnetic circuit mounted on the free end of a piezoelectric cantilever beam. ► The magnetic circuit produces an enhanced magnetic flux density on the power line. ► More energy from the power line can be converted into electrical energy using the cantilever beam. ► An analytical model is developed to predict the output voltage and power, and the theory matches the experiment well. This paper presents a piezoelectric energy harvester for scavenging AC magnetic field energy from an electric power line based on the Ampere's law. The harvester employs a piezoelectric cantilever beam with a magnetic circuit attached to the free end of the beam. The magnetic circuit uses three NdFeB magnets connected by two magnetic yokes in series, which produces an enhanced magnetic flux density on the power line. Consequently, more AC magnetic field energy from the current-carrying power line can be converted into electrical energy using the piezoelectric cantilever beam. In the theoretical analysis, the integral of the magnetic flux density produced by the magnetic circuit along the power line is expressed by a power series of the transverse displacement of the magnetic circuit, and a nonlinear modal equation of motion is derived. The equation is solved by the Linstedt–Poincaré method. The expressions of the steady-state output voltage and power are obtained based on the assumed model. The experimental results are in good agreement with the analytical results. Under the resonant frequency of 50Hz, the harvester can generate a power of 1.58mW with a matching load resistance of 216kΩ at an AC current of 6A.