Cooling systems with no moving parts or environmentally harmful refrigerant liquids or gases can operate nearly twice as efficiently as a standard air conditioning system, which can reduce electricity use.
Most air conditioners and refrigerators rely on compressing and expanding fluids to absorb or release large amounts of heat. Although these systems are relatively inexpensive and simple to produce, they are not very efficient and therefore require a lot of energy – about one fifth of the electricity used in buildings globally – and many of the refrigerants used are environmental. Are harmful for.
Now, Emmanuel Defay and his colleagues at the Luxembourg Institute of Science and Technology have developed a coolant-free refrigeration device made of lead, scandium and tantalum metals. It can reach a maximum efficiency of more than 60 percent, which is almost twice that of typical single-room air conditioning units.
The technology relies on a principle called electrocaloric cooling, which occurs when an electric field applied to a material changes the direction of electric charges, causing a temporary increase in temperature and a subsequent decrease when the electric field is removed.
To create their cooling system, Defoe and his colleagues stacked eight strips of a material called lead scandium tantalate, which is electrocaloric, on top of each other and immersed them in a heat-carrying fluid, silicone oil. When the electric field is turned on and the strips heat up, the fluid moves to the right, and when it cools, it moves to the left, creating a permanent hot and cold zone of about 20°C difference. Become an area.
These areas can be used as hot and cold reservoirs, from which oil can be circulated through pipes to cool or heat rooms or objects as desired.
Although the efficiency of the device is theoretically 67 percent, the current design is about 12 percent efficient. Defoe says that this could be improved if lead was found to be a better conductor of heat than scandium tantalate.
“An excellent performance has been achieved by combining known elements,” says Neil Mathur of the University of Cambridge. He says using thin strips of electrocaloric material rather than a lump of material means higher electric fields can be applied without breaking the material, giving better cooling performance. However, he added, the team only looked at the cooling power of a stack of metal strips, while it will be interesting to see how the entire device performs together.
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