Upscaling of Thermomagnetic Generators Based on Heusler Alloy Films

Joseph, Joel; Ohtsuka, Makoto; Miki, Hiroyuki; Kohl, Manfred

doi:10.1016/j.joule.2020.10.019

Cited by 25 publications

(38 citation statements)

References 31 publications

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“…However, ordering the data with respect to the working ∆T res two distinct groups are apparent. Devices working over a temperature span of the order of 100°C or more [12,14,4,17] that generally get powers in the milli-Watts per cubic centimeter range, and prototypes working over a few tens degrees (i.e. ≤ 50°C) where the power density is in the range of tens or hundreds of micro-Watts per cubic centimeter.…”

Section: Discussionmentioning

confidence: 99%

“…Once thermal energy has been converted into magnetic one, conversion into electricity can be achieved through different methods (see [16] for a recent and exhaustive review). Direct conversion through Faraday law represents the most straightforward road [15]; in some cases an intermediate mechanical energy conversion step has been successfully used, jointly with Faraday law, in order to enhance conversion efficiency [14,4,17]. On the other hand the mechanical energy can also be harvested through other transducers as electroactive materials [12], and piezoelectric materials [13,18].…”

Section: Introductionmentioning

confidence: 99%

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Self-oscillation and heat management in a LaFeSi based thermomagnetic generator

Ahmim

Almanza

Loyau

et al. 2021

Journal of Magnetism and Magnetic Materials

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Harvesting and directly converting the largely untapped and omnipresent lowgrade heat into electricity has huge technological potential for supplying internet of things (IoT) devices, and wireless sensors in smart buildings applications. To this end, we present a self-actuating, autonomous, thermomagnetic generator (TMG) showing state-of-the-art net power output 4.2 µW (240 µW cm −3 ), working over a 35.1°C temperature difference. The core of our design is made of cheap and easily available piezoelectric buzzers and of commercial LaFeSi magnetocaloric materials from Vacumschmelze. The device self oscillating cycle is studied as a dynamical system with particular attention to the interplay between mechanical and thermal dynamics.

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Self-oscillation and heat management in a LaFeSi based thermomagnetic generator

Ahmim

Almanza

Loyau

et al. 2021

Journal of Magnetism and Magnetic Materials

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“…One of the advantages of this TMG concept is that it is self-adapting to operating conditions like the source temperature and ambient temperature. When the source temperature increases, for instance, heat transfer increases causing an increase in oscillation amplitude and resonance frequency [ 22 ]. Yet, a major challenge is to maintain the condition of resonant self-actuation for optimum power output.…”

Section: Materials Properties and Operation Principlementioning

confidence: 99%

“…One option is to make use of the steep increase in magnetization at the first-order transformation between non-ferromagnetic martensite and ferromagnetic austenite in metamagnetic alloys, which is highly attractive in the case of small hysteresis [ 18 , 19 , 20 ]. Another option is to utilize the large change of magnetization at the second-order transition, e.g., in the Heusler alloy Ni-Mn-Ga, which occurs without hysteresis [ 21 , 22 ].…”

Section: Introductionmentioning

confidence: 99%

“…Recent demonstrators based on Ni-Mn-Ga films show promising results with magnetic power density close to 120 mW/cm 3 with respect to the active layer volume [ 21 ]. The electrical power per footprint of the resonant TMG devices reached 50 µW/cm 2 at a temperature change of only 3 K [ 22 ]. The large power density relies on rapid heat transfer of the film and the unique concept of resonant self-actuation of a film cantilever oscillating at high frequency in the order of 100 Hz.…”

Section: Introductionmentioning

confidence: 99%

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Lumped Element Model for Thermomagnetic Generators Based on Magnetic SMA Films

et al. 2021

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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.

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A Gd‐Film Thermomagnetic Generator in Resonant Self‐Actuation Mode

Joseph

Fontana

Devillers

et al. 2023

Adv Funct Materials

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Thermomagnetic generation is a promising technology for conversion of low-grade waste heat into electricity. Key requirements for the development of efficient thermomagnetic generators (TMGs) are tailored thermomagnetic materials as well as innovative designs enabling fast heat transfer. Recently, film-based thermomagnetic generators are developed that operate in the mode of resonant self-actuation enabling high frequency and stroke of a movable cantilever and, thus, efficient conversion of thermal energy into electrical energy. Here, the performance of a Gadolinium (Gd)-film-based TMG that is optimized for resonant self-actuation near room temperature is reported. The Gd-film TMG exhibits large oscillation frequencies up to 106 Hz and large strokes up to 2 mm corresponding to 38% of the oscillating cantilever's length. This performance occurs in a sharply bound range of ambient temperatures with an upper limit near the film's ferromagnetic to paramagnetic transition temperature T c of 20 °C and of heat source temperatures ranging between 40 and 75 °C. The maximum power per footprint is 23.8 µWcm −2 , at which the Gd film undergoes a temperature change of only 0.9 °C at ≈10 °C above T c .

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Upscaling of Thermomagnetic Generators Based on Heusler Alloy Films

Cited by 25 publications

References 31 publications

Self-oscillation and heat management in a LaFeSi based thermomagnetic generator

Self-oscillation and heat management in a LaFeSi based thermomagnetic generator

Lumped Element Model for Thermomagnetic Generators Based on Magnetic SMA Films

A Gd‐Film Thermomagnetic Generator in Resonant Self‐Actuation Mode

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