Scientists Could Change The Way Refrigerators Work Forever

Before the modern refrigerator, frozen chunks of water had to be hauled over great distances. These days, cooling down food is much easier. The modern refrigerator uses a closed-loop system of pipes filled with refrigerant chemicals to absorb and radiate heat. It's a tried-and-true method that works nicely — as long as you don't mind the huge amount of energy it consumes or the environmentally unsafe chemicals involved. But there's always room for innovation.

In 2023, scientists from Berkeley devised a new system of refrigeration that hearkens back to the old days of using water ice to cool food. The paper, published in Science, calls the method the "ionocaloric refrigeration cycle," and it employs the thermodynamic properties of the phase changes of water. When ice melts into liquid, it absorbs heat from its surroundings. When liquid water freezes into ice, it releases heat. Thus, if you could get ice to melt inside a container and then allow it to freeze again outside the container, you would effectively refrigerate the container's contents.

But how do you get ice to melt inside a refrigerator? The researchers came up with a clever solution: Add some charged ions. When ions, or salts, are added to water, the effect of those salts on water is that they lower its freezing point. It's the same reason why ocean water freezes at 28 degrees Fahrenheit rather than 32 degrees. So, the team designed a refrigerator model that uses an electrical current to add ions to water when it's inside a container and remove the ions when it's outside the container. This way, the water can melt into a liquid to absorb a few degrees of internal heat, and then freeze solid to radiate the heat to the exterior. The process is something of a balancing act, but it may prove an eco-friendly alternative to modern refrigeration.

In an interview with the publication News from Berkeley Lab, the paper's co-author Ravi Prasher explained that the project had three goals for refrigeration: reduce its cost, increase its energy efficiency, and lower its global warming potential. Obviously, the new refrigerator model could be extremely cost-effective, since it uses common ingredients. The team's experiments used purified water, iodine, and sodium — ingredients you could find in a grocery store.

The system for adding and removing the ions from the water could be energy-efficient, as well. In initial tests, the researchers were able to change the temperature by 25 degrees Celsius by using just 0.22 volts. While the model hasn't yet been constructed into a functioning refrigerator, such low energy requirements are quite promising for a replacement to the energy-hungry refrigerators we use today.

But saving on your electric bill is one thing, while saving the planet from global warming is another. The refrigeration sector, which includes air conditioning and heat pumps, is responsible for nearly 8% of all global greenhouse gas emissions. Part of that comes from generating the energy required to keep it all running, so a more energy-efficient refrigerator would reduce greenhouse emissions. Better yet, the team's model uses salt and water in place of the hydrofluorocarbon gases (HFCs) we use in most refrigerators today. HFCs, such as R134a and R410a, are potent greenhouse gases that often leak out of trashed refrigerators and manufacturing facilities. The team even experimented with adding ethylene carbonate to the system, which, like household sodium carbonate, consumes carbon dioxide during its manufacture. That means refrigerators of the future might not just reduce carbon emissions — they might actually pull carbon from the air.