Analysis of thermal energy harvesting using ferromagnetic materials

This Letter aims at giving a preliminary investigation of the thermal energy harvesting capabilities of a technique using the temperature-dependent permeability of ferromagnetic materials. The principles lie in the modification of the magnetic field caused by the variation of the permeability due to the temperature change, hence generating a voltage across a coil surrounding the circuit. The technique can be made truly passive by the use of magnets for applying bias magnetic field. Theoretical results, validated by experimental measurements, show a voltage output of 1.2 mV at optimal load of 2 Omega under 60 K temperature variation in 5 s (with a maximum slope of 25 K s(-1)) Further improvements, such as the use of low resistivity coil and magnet with high remnant magnetic field, indicate that it is possible to convert up to 7.35 mu J cm(-3) K-2 cycle(-1). (C) 2014 Elsevier B.V. All rights reserved.