Experimental Demonstration of a Barocaloric Heat Pump

Solid-state refrigeration offers a sustainable alternative to traditional cooling systems, addressing environmental concerns and attracting growing interest due to the significant energy consumption of refrigeration and air conditioning. Barocaloric (BC) solid-state refrigeration leverages substantial isothermal entropy and adiabatic temperature changes resulting from the volumetric deformation of BC materials under hydrostatic pressure. While there have been promising demonstrations of heat pumps utilizing different caloric effects, prototypes of BC heat pumps remain limited due to challenges in maintaining high pressures and effectively exchanging heat with the refrigerant core. This work presents an experimental demonstration of a BC heat pump device with a low-cost natural rubber BC refrigerant and ethylene glycol heat transfer fluid. By cyclically applying and releasing hydrostatic pressure on a BC refrigerant confined within a rigid additively manufactured titanium cylindrical enclosure, we facilitated heat pumping between hot and cold thermal reservoirs using an integrated heat exchanger. We operate the device for a range of applied hydrostatic pressure, coolant flow rates and temperature spans. We measured a specific heating power of 36 W/kg and a coefficient of performance of around 4 at approximately 1 K temperature span and 0.25 GPa applied pressure. These results indicate BC heat pump comparable to state-of-the-art vapor compression, and significantly better performance is likely using other promising BC materials reported in the literature.