While the laws of thermodynamics don’t make it easy, some of a system’s lost energy can be recovered through energy harvesting devices. These devices use native vibrations, magnetic fields, electric fields, temperature, etc., to move electrons and induce new currents that can either be used directly or stored through some storage medium, such as a battery. While large-scale thermodynamic engines (power plants) create large-scale electricity, energy harvesting generally refers to utilizing energy that was otherwise considered wasted or lost.

Research described in Applied Physics letters experimentally and theoretically explores an energy harvesting device that couples the conversion of both vibrations and alternating magnetic fields into an electric current. Previous devices and designs consider conversion of only a single type of waste energy, and this unique hybridization shows efficiencies that are between 15 and 30 percent higher than single-energy conversion approaches.

The approach uses a magnetic-sensitive substrate bonded to a piezoelectric sheet. A careful analysis of the phase and frequency differences between the vibration and magnetic excitations can guide performance optimization of the device by changing the signal generators to operate in a variety of environmental conditions.

While this device is made to exploit both vibrations and magnetic fields, it can operate if only a single-energy type is available at efficiencies comparable to other existing devices. Applications of this hybrid approach are wide-ranging and can include waves, foot traffic and others. The authors state, however, that the most viable and first market approaches would likely include industrial settings where high-powered machinery, having both high vibrations and oscillating magnetic fields, is present.

Source: “Hybrid energy harvesting from mechanical vibrations and magnetic field,” by Xueping Xu, Chunlong Zhang, Qinkai Han, and Fulei Chu, Applied Physics Letters (2018). The article can be accessed at https://doi.org/10.1063/1.5038412.