Lumped element model for thermomagnetic generators based on magnetic sma films

Joel Joseph, Makoto Ohtsuka, Hiroyuki Miki, Manfred Kohl

Research output: Contribution to journalArticlepeer-review

Abstract

This paper presents a lumped element model (LEM) to describe the coupled dynamic properties of thermomagnetic generators (TMGs) based on magnetic shape memory alloy (MSMA) films. The TMG generators make use of the concept of resonant self‐actuation of a freely movable cantilever, caused by a large abrupt temperature‐dependent change of magnetization and rapid heat transfer inherent to the MSMA films. The LEM is validated for the case of a Ni‐Mn‐Ga film with Curie temperature TC of 375 K. For a heat source temperature of 443 K, the maximum power generated is 3.1 μW corresponding to a power density with respect to the active material’s volume of 80 mW/cm3. Corresponding LEM simulations allow for a detailed study of the time‐resolved temperature change of the MSMA film, the change of magnetic field at the position of the film and of the corresponding film magnetization. Resonant self‐actuation is observed at 114 Hz, while rapid temperature changes of about 10 K occur within 1 ms during mechanical contact between heat source and Ni‐Mn‐Ga film. The LEM is used to estimate the effect of decreasing TC on the lower limit of heat source temperature in order to predict possible routes towards waste heat recovery near room temperature.

Original languageEnglish
Article number1234
Pages (from-to)1-13
Number of pages13
JournalMaterials
Volume14
Issue number5
DOIs
Publication statusPublished - 2021 Mar 1

Keywords

  • Curie temperature
  • Lumped-element modelling
  • Magnetic shape memory films
  • Magnetization change
  • Ni‐Mn‐Ga film
  • Power generation
  • Thermomagnetic energy generators
  • Waste heat recovery

ASJC Scopus subject areas

  • Materials Science(all)

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