Thermal processes of miniature thermomagnetic generators in resonant self-actuation mode

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

doi:10.1016/j.isci.2022.104569

Cited by 5 publications

(6 citation statements)

References 38 publications

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“…At least, a minimal heat transfer coefficient is required, above which stable resonant oscillation occurs characterized by large stroke and frequency. [31] In the present case, the required minimal heat transfer coefficient κ is determined to be ≈4000 Wm −2 K −1 by matching the measured electrical and mechanical performance of the TMG with the LEM simulations, which is in line with our previous simulations [31] and literature data. [32] The simulated heat dissipation from the Gd film by heat conduction to the cantilever via the bonding layer (Figure 6b) shows the same dependencies on T amb and T source as the heat intake.…”

Section: Analysis Of Thermal Performancesupporting

confidence: 84%

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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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Section: Analysis Of Thermal Performancesupporting

confidence: 84%

“…The key parameter governing conductive heat dissipation is the thermal resistance R b of the bonding layer between the Gd film and the cantilever. [ 31 ] This value requires adjustment during the design of the TMG device to match heat intake during contact with the heat source for optimal heat transfer.…”

Section: Analysis Of Thermal Performancementioning

confidence: 99%

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

Joseph

Fontana

Devillers

et al. 2023

Adv Funct Materials

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“…Recently, NiMn-based Heusler alloys have been reported by multiple research groups as good TMG materials. 3,24,[28][29][30] Besides, Heusler alloys exhibit both SOMT of austenite phase and FOMT between the FM austenite and weak-magnetic martensite phase. 23,31 Therefore, this allows us to make a more reasonable comparison by choosing materials with similar composition in the same system but different phase transitions.…”

Section: Materials Horizonsmentioning

confidence: 99%

Excellent thermomagnetic power generation for harvesting waste heat via a second-order ferromagnetic transition

Chen,

Liu,

Liu

et al. 2024

Mater. Horiz.

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“…On the other hand, if the cooling of the MSMA film is too slow to be attracted to the magnet surface, it will undergo chaotic oscillations without touching the magnet until the attraction force of one of the magnets is sufficiently large. In the optimum case, however, matching the time constants of heat transfer and mechanical oscillation will lead to resonant self-actuation [33]. In the present actuator design, the dimensions of the MSMA films are adjusted for a sufficiently large surface-to-volume ratio, and the eigenfrequency of the moving mass is tuned to meet the matching conditions.…”

Section: Resonant Self-actuationmentioning

confidence: 99%

Resonant Self-Actuation Based on Bistable Microswitching

et al. 2023

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We present the design, simulation, and characterization of a magnetic shape-memory alloy (MSMA) film actuator that transitions from bistable switching to resonant self-actuation when subjected to a stationary heat source. The actuator design comprises two Ni-Mn-Ga films of 10 µm thickness integrated at the front on either side of an elastic cantilever that moves freely between two heatable miniature permanent magnets and, thus, forms a bistable microswitch. Switching between the two states is induced by selectively heating the MSMA films above their Curie temperature Tc. When continuously heating the permanent magnets above Tc, the MSMA film actuator exhibits an oscillatory motion in between the magnets with large oscillation stroke in the frequency range of 50–60 Hz due to resonant self-actuation. A lumped-element model (LEM) is introduced to describe the coupled thermo-magnetic and magneto-mechanical performance of the actuator. We demonstrate that this performance can be used for the thermomagnetic energy generation of low-grade waste heat (T < 150 °C) with a high power output per footprint in the order of 2.3 µW/cm2.

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Thermal processes of miniature thermomagnetic generators in resonant self-actuation mode

Cited by 5 publications

References 38 publications

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

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

Excellent thermomagnetic power generation for harvesting waste heat via a second-order ferromagnetic transition

Resonant Self-Actuation Based on Bistable Microswitching

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