Highly efficient mechanocaloric cooling using colossal barocaloric plastic crystals

Despite the emergence of colossal barocaloric materials with great potential to replace environmentally unfriendly vapor-compression refrigerants, a scalable and cyclic reversible cooling device has not been demonstrated yet. Here, we develop experimental compressive mechanocaloric prototypes using bulk amounts of low-cost plastic crystal neopentylglycol (NPG) with high device-level scalability. Large quasi-adiabatic temperature changes in NPG of 20.8 K for heating and −16.7 K for cooling are achieved during the cyclic pressurization-depressurization processes from ambient pressure to 231 MPa. A maximum temperature drop of 3.8 K and cooling energy of 900 J in water as the heat-exchanging medium are observed in the prototype. Using molecular dynamics simulations, an outstanding coefficient of performance of 14 and cooling energy density of 90 kJ/kg are achieved for the reverse Stirling cooling cycle at a large temperature span of 5 K, while the corresponding values are 7.5 and 30 kJ/kg for the reverse Brayton cooling cycle.