Colossal barocaloric effect in fatty acid methyl esters

Abstract

The barocaloric effect is a green refrigeration technology, offering a more environmentally friendly alternative to conventional gas compression refrigeration. The barocaloric effect is induced by pressure in phase change materials, and in which high entropy change and adiabatic temperature change were obtained. Here, a colossal barocaloric effect was discovered in solid–liquid transition of fatty acid methyl esters (FAMEs). In methyl palmitate, the isothermal entropy change can reach as high as 707 J kg⁻¹ K⁻¹ under a low pressure of 80 MPa at 311 K; in methyl stearate, the isothermal entropy change can reach up to 680 J kg⁻¹ K⁻¹ under a pressure of 60 MPa at 308 K. These values are comparable to those of traditional refrigeration materials, such as R314a. The calculated adiabatic temperature change is 22 K for methyl palmitate and 13 K for methyl stearate. Raman spectroscopy indicates that unloading pressure to the liquid phase facilitates the formation of gauche bonds and the formation of solid–liquid phase transformation, which results in a larger configuration entropy change. This work provides a new candidate for solid–liquid transition materials in the practical application of barocaloric effect refrigeration.