Systematic characterization of elastocaloric materials with a unified thermo-mechano-caloric testing setup

Given the obstacles to achieving climate neutrality and mitigating global warming, climate-neutral technologies in varying applications must be advanced. The refrigeration industry in particular needs to move forward, as energy consumption for climate control devices is expected to increase to 30% of global energy consumption. In this application area, elastocaloric cooling represents an innovative alternative to conventional vapor-compression based cooling methods, as already been classified as promising by both the EU Commission and the US Department of Energy.

Elastocaloric cooling is based on the caloric effect of superelastic shape memory alloys. The stress-induced phase transformation leads to release and absorption of latent heats and is thus capable of heating or cooling the environment. Commercially available binary Nickel-Titanium alloys were developed for medical purposes and not optimized for elastocaloric application. Thus, a crucial step in the development of elastocaloric devices must be the development and characterization of these very materials with regard to elastocaloric properties.

A complete characterization of elastocaloric materials must include mechanical, thermal and caloric parameters. Since there are no available experimental setups to perform required experiments under application conditions, a novel unified thermo-mechano-caloric testing setup is presented, followed by a characterization routine carried out to determine the elastocaloric potential of materials.

Particularly, the training behaviour of elastocaloric materials is of great interest, since it has a major impact on the resulting stress-strain hysteresis and latent heats, which determine the coefficient of performance for these materials. The paper will present first results on the effect of different training parameters.