Solid-State Thermal Energy Storage Using Reversible Martensitic Transformations

TL;DR

This paper demonstrates the use of reversible Martensitic transformations in shape memory alloys as a new solid-solid phase change material for thermal energy storage, showing superior thermal properties and tunability.

Contribution

First experimental demonstration of reversible Martensitic transformations as a solid-solid phase change material for thermal energy storage.

Findings

Shape memory alloys show up to 100 times higher Figure of Merit than standard materials.

Thermal properties of NiTi alloys can be tuned across a wide temperature and heat range.

Experimental validation of temperature leveling during transient heating and cooling.

Abstract

The identification and use of reversible Martensitic transformations, typically described as shape memory transformations, as a new class of solid-solid phase change material is experimentally demonstrated here for the first time. To prove this claim, time-domain thermoreflectance, frequency-domain thermoreflectance, and differential scanning calorimetry studies were conducted on commercial NiTi alloys to quantify thermal conductivity and latent heat. Additional Joule-heating experiments demonstrate successful temperature leveling during transient heating and cooling in a simulated environment. Compared to standard solid-solid materials and solid-liquid paraffin, these experimental results show that shape memory alloys provide up to a two order of magnitude higher Figure of Merit. Beyond these novel experimental results, a comprehensive review of >75 binary NiTi and NiTi-based ternary and quaternary alloys in the literature shows that shape memory alloys can be tuned in a wide range of transformation temperatures (from -50 to 330{deg}C), latent heats (from 9.1 to 35.1 J/g), and thermal conductivities (from 15.6 to 28 W/mK). This can be accomplished by changing the Ni and Ti balance, introducing trace elements, and/or by thermomechanical processing. Combining excellent corrosion resistance, formability, high strength and ductility, high thermal performance, and tunability, SMAs represent an exceptional phase change material that circumvents many of the scientific and engineering challenges hindering progress in this field.