The ionocaloric refrigeration cycle is a cooling technology that utilizes the ionocaloric effect, driven by an electrochemical field, to achieve efficient refrigeration. By manipulating the electrochemical potential through ion addition or removal, significant temperature changes and entropy variations are achieved. This cycle is distinct from typical widespread refrigeration cycles.

It was developed by Drew Lilley and Ravi Prasher at the Department of Energy's Lawrence Berkeley National Laboratory with their work published in January 2023.

The ionocaloric refrigeration cycle is a cooling technology that offers high efficiency and zero global warming potential. This cycle utilizes the ionocaloric effect, which is driven by an electrochemical field, to achieve significant adiabatic temperature changes and isothermal entropy changes. Developed as a solution to the pressing need for sustainable and environmentally-friendly refrigeration systems, the ionocaloric refrigeration cycle shows promising results in terms of performance and energy efficiency.

Traditional refrigeration technologies, such as vapor-compression (VC) systems, have relied on hydrofluorocarbons (HFCs) as refrigerants. However, HFCs have a high global warming potential and contribute significantly to greenhouse gas emissions. To address these environmental concerns, researchers have explored solid-state caloric materials that exhibit refrigeration effects under external fields. While previous caloric materials have shown limited performance and low coefficient of performance (COP), the ionocaloric cycle demonstrates remarkable improvements.

The ionocaloric effect operates by manipulating the electrochemical field surrounding a solid phase through the addition or removal of ions. This electrochemical mixing of species induces significant energetic changes, resulting in a thermal response and temperature variation within the system. Unlike other caloric effects, where the applied field interacts with the material's conjugate field pair, the ionocaloric effect operates in reverse. The control of the electrochemical potential is achieved by altering the concentration of chemical species through various field variables such as temperature, pressure, and voltage.

The ionocaloric refrigeration cycle incorporates the ionocaloric effect into a thermodynamic cycle to provide continuous and efficient refrigeration. The cycle involves four steps: isentropic mixing, isocompositional and isothermal melting via heat absorption, isentropic separation, and isocompositional and isothermal crystallization via heat rejection. By following these steps, the cycle achieves Carnot-like behavior and enables efficient cooling.

Among various ionocaloric systems, the ethylene carbonate-sodium iodide system has shown particular promise. It exhibits high latent heat of fusion, a melting point above room temperature, and environmental compatibility, making it an attractive option for practical applications. The ionocaloric effect in this system surpasses other caloric effects reported to date, demonstrating significantly higher adiabatic temperature changes and entropy changes per unit mass and volume.

The practical implementation of the ionocaloric refrigeration cycle involves the use of desalination techniques, such as electrodialysis, to separate the solution and regenerate the system. While the theoretical properties of the EC/NaI system show competitive performance, real-world efficiency will depend on the details of the separation process. Electrochemical techniques like electrodialysis offer high efficiencies without requiring high operating pressures or fields, making them suitable for practical application.