A laboratory cooling system based on salt and ions has produced a temperature change of up to 25 degrees Celsius using a 1-volt charge. The result points to a possible new path for air conditioners, refrigerators, and drinking-water dispensers that currently rely on freon-based systems.
The approach is known as the ionocaloric cycle, which uses ions to trigger material phase changes that absorb heat. Researchers are exploring it as an alternative to conventional cooling systems that use hydrofluorocarbon, or HFC, fluids.
A Different Route to Cooling
Most existing cooling appliances circulate a heat-transfer fluid through a closed loop. The fluid evaporates into gas and then condenses back into liquid, allowing the cooling cycle to continue.
This process is widely used and effective in household appliances. However, the materials used in such systems carry environmental risks.
Researchers at Lawrence Berkeley National Laboratory and the University of California, Berkeley, are investigating cooling through the energy materials absorb or release when they change form. Their work seeks to produce cooling without depending on the same conventional refrigeration cycle.
| Component or process | Role in cooling |
|---|---|
| HFC or freon | Heat-transfer fluid in conventional cooling systems |
| Melting ice | Absorbs heat as it changes from solid to liquid |
| Ions from salt | Help trigger material changes without raising temperature |
How Salt Ions Are Used
The principle can be understood through melting ice. As ice turns into water, it absorbs heat from its surroundings and makes the nearby area feel cooler.
The researchers aim to initiate a similar change without increasing the material’s temperature. They do this by adding charged energy particles known as ions.
Salt already demonstrates a related effect when it is used to prevent ice from forming on roads during winter. It helps melt ice, and the researchers have adapted the underlying phase-change principle into the ionocaloric cycle.
Drew Lilley of Lawrence Berkeley National Laboratory said the technology remains under development. He noted that no alternative cooling solution has yet combined efficiency, safety, and a lack of harmful environmental effects.
Testing Materials for a Practical System
The team tested a salt made from iodine and sodium to melt ethylene carbonate, a material also used in lithium-ion batteries. The liquid used in the experiment relied on carbon dioxide.
According to the researchers, the process could potentially reach zero emissions and even negative emissions. The reported 25-degree-Celsius temperature change was achieved with a 1-volt charge.
The next challenge is turning the laboratory concept into a practical commercial system. Researchers need to identify the salt that can most effectively draw heat from the space being cooled.
In 2025, their research identified nitrate-based salts as the most efficient option. That finding could provide a foundation for developing a more environmentally safe replacement for freon.
No timeline has been announced for consumer products using the ionocaloric system. If it becomes practical, air conditioners and refrigerators could eventually operate through a mechanism different from today’s HFC-based technology.