Between keeping our food cool, beer chilled, and data centers functional, refrigeration uses a fifth of the world's electricity. Although removing heat is always going to be energy intensive, large inefficiencies in the gasses we use for cooling contribute to the problem. Dr Xavier Moya thinks he has a solution, but astonishingly, it isn't a better gas, it's a solid.
The idea that we can use a crystal for refrigeration sounds almost as wacky as using them to solve your legal problems, but Nature Communications is a much more reliable source than the Goop catalog. Indeed, the capacity for solids to be used for cooling has been known for a long time. Certain materials, when put under pressure or exposed to magnetic or electric fields, change their structure and absorb heat. However, these have been even less efficient than the hydrofluorocarbons and hydrocarbons used in most fridges or air-conditioning units, and largely treated as a curiosity.
However, Moya of Cambridge University reports that neopentylglycol ((CH3)2C(CH2OH)2) is different. It is made up of nearly spherical molecules that interact with each other weakly and therefore can change their orientation towards each other. When squashed, neopentylglycol's molecules rearrange to take up much less volume.
A return to the disordered, high-volume state can occur if the pressure is removed and heat absorbed from the external environment, which cools everything around the crystals down. The paper notes that either a secondary circuit with fluid in it, fins, or heat pipes could be used to draw the heat in from the wider environment.
The efficiency of this process is around 10 times greater than any previous solid tested and similar to that for the best hydroflurocabon gas. Moreover, neopentylglycol has significant advantages over the gasses used for refrigeration. It's certainly much less likely to leak, and if it does, it won't contribute to global warming. It also doesn't pose the fire-risk that highly flammable gasses do.
Better still, neopentylglycol is cheap and widely available. It's produced entirely from three of the most common elements, so there's never going to be a shortage. Since it is already used in paints and lubricants, we know something about its health effects too. The path from lab bench to commercial product is seldom swift, but Moya and co-authors are already working on it.
Now that the potential of such soft crystals has been recognized, it's possible that further research will find similar molecules that are even more efficient. However, Moya is not waiting, instead getting started on producing a commercial refrigeration unit based on neopentylglycol.
By chance, a different team also discovered neopentylglycol's capacities, announcing their find just three weeks ago. However, Moya's team claim efficiencies 30 percent higher than their rivals by using different conditions.