Scientists have just invented a whole new way to cool things: ScienceAlert

Say hello to ionocaloric cooling: a new way to lower the mercury that has the potential to replace existing methods with something safer and friendlier to the planet.

Typical cooling systems transport heat away from a room via a gas that cools as it expands some distance away. As efficient as this process is, some of the selected gases we use are also particularly unfriendly to the environment.

However, there is more than one way a substance can be forced to absorb and release heat energy.

A new method developed by researchers from the Lawrence Berkeley National Laboratory and the University of California, Berkeley, in the US, exploits the way energy is stored or released when a material changes phase, such as when solid ice turns into liquid water, for example.

Increase the temperature of a block of ice, it melts. What we may not see so easily is that melting absorbs heat from the surroundings and cools it effectively.

One way to force ice to melt without having to turn up the heat is to add a few charged particles, or ions. Salt on roads to prevent ice formation is a common example of this in action. The ion caloric cycle also uses salt to change a liquid’s phase and cool its surroundings.

“The refrigerant landscape is an unsolved problem,” says mechanical engineer Drew Lilley, of the Lawrence Berkeley National Laboratory in California. “Nobody has developed an alternative solution that keeps things cool, works efficiently, is safe and doesn’t harm the environment.”

“We believe the ionocaloric cycle has the potential to fulfill all of these goals if properly realized.”

The researchers modeled the theory of the ionocaloric cycle to show how it could potentially compete with, or even improve on, the efficiency of refrigerants used today. A current passing through the system would move the ions within it, changing the material’s melting point to change temperature.

Ionocaloric cooling
The ionocaloric cycle in action. (Jenny Nuss/Berkeley Lab)

The team also ran experiments with a salt made of iodine and sodium to melt ethylene carbonate. This common organic solvent is also used in lithium-ion batteries, and is produced using carbon dioxide as an input. It can make the system not just GWP [global warming potential] zero, but GWP negative.

A temperature shift of 25 degrees Celsius (45 degrees Fahrenheit) was measured by applying less than a single volt of charge in the experiment, a result that surpasses what other caloric technologies have been able to achieve so far.

“There are three things we’re trying to balance: the GWP of the refrigerant, energy efficiency and the cost of the equipment itself,” says mechanical engineer Ravi Prasher, of Lawrence Berkeley National Laboratory.

“From the first attempt, our data look very promising on all three of these aspects.”

The vapor compression systems currently used in refrigeration processes rely on gases that have a high GWP, such as various hydrofluorocarbons (HFCs). Countries that have signed the Kigali Amendment have committed to reducing the production and consumption of HFCs by at least 80 percent over the next 25 years – and ionocaloric refrigeration can play a big role in that.

Now the researchers must get the technology out of the laboratory and into practical systems that can be used commercially and scaled up without problems. Eventually, these systems can be used for both heating and cooling.

“We have this brand new thermodynamic cycle and framework that brings together elements from different fields, and we’ve shown that it can work,” says Prasher.

“Now is the time for experimentation to test different combinations of materials and techniques to meet the technical challenges.”

The research is published in Science.

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