Physics World: Efficient refrigerator without coolant

Refrigerators and air conditioning systems consume around a fifth of the electricity generated worldwide – and this trend is increasing. In order to convert electricity into heat – or cold – more efficiently, better systems are needed. Scientists have developed a prototype that requires less electricity than conventional refrigerators to achieve the same cooling performance. As the specialist journal “Science” reports, with an efficiency of 64 percent, it outperforms established cooling systems, which have an efficiency of at best 50 percent.

In most current cooling systems, gases are compressed into liquids. However, they rely on climate-damaging fluorinated substances. In contrast, the new cooling system is based on solids – special crystals are used here. If you apply an electrical voltage to this material, the components of the crystal align and it heats up. If the voltage is cut, the material cools again. The exact cause of this phenomenon – called the electrocaloric effect – is still unclear. It is possible that crystal components vibrate more strongly under tension.

Based on this effect, Emmanuel Defay’s group from the Luxembourg Institute of Science and Technology developed a prototype. To do this, they stacked several layers of scandium tantalate and lead on top of each other, which heat up in an electric field. They alternately created an electric field with voltages of up to 400 volts and then reduced it again. They dissipate the heat generated in this cycle via liquid through the cell structure.

Promising prototype for an alternative cooling system

This cooling system reaches a maximum cooling power of 4.2 watts, enough to cool a few milliliters of water to around 20 degrees Celsius. The previous record value for such electrocaloric cooling dated from 2020 and was only 13 degrees Celsius. The new cooler could be enough to cool smaller objects such as processors in a computer. But it’s still too small and not powerful enough for larger objects like air conditioning systems or refrigerators.

If it is possible in the future to further optimize this alternative cooling system through intelligent design of the cooling and heating crystal layers, many applications will be interesting. On the one hand, more energy-efficient refrigerators and air conditioning systems could be developed. On the other hand, more efficient and quieter heat pumps would also be possible, which would make it possible to heat buildings with electricity from renewable energy sources – without using harmful coolants.

Mathew Baynton

"Bacon nerd. Extreme zombie scholar. Hipster-friendly alcohol fanatic. Subtly charming problem solver. Introvert."

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