#magnetocaloric

The future of eco-friendly cooling: Enhancing efficiency and sustainability of magnetic refrigerants

Conventional air conditioners and refrigerators rely on vapor-compression cycles and chemical refrigerants that contribute significantly to global warming. Magnetic refrigeration offers a cleaner alternative using the magnetocaloric effect (MCE), a phenomenon where certain materials change temperature when exposed to a magnetic field. Until now, researchers have faced a fundamental dilemma: Materials with a high cooling effect often suffered from irreversible energy losses, an effect known as hysteresis, which leads to rapid degradation in the cooling effect under operating conditions. Conversely, the conventional durable materials failed to achieve the large cooling effect required for practical application. Researchers from a global consortium, including NIMS (Japan), TU Darmstadt (Germany), and other institutes, have now unlocked a new pathway toward sustainable refrigeration. Published in Advanced Materials, the study highlights a significant leap forward in cooling technology.

Magnetic frustration in atacamite triggers dramatic cooling when exposed to strong fields

Natural crystals fascinate with their vibrant colors, their nearly flawless appearance and their manifold symmetrical forms. But researchers are interested in them for quite different reasons: Among the countless minerals already known, they always discover some materials with unusual magnetic properties. One of these is atacamite, which exhibits magnetocaloric behavior at low temperatures—that is, the material's temperature changes significantly when it is subjected to a magnetic field. A team headed by TU Braunschweig and the HZDR has now investigated this rare property. In the long term, the results, now published in Physical Review Letters, could help to develop new materials for energy-efficient magnetic cooling.

Squeezable Metal Offers a Greener Approach to Refrigeration

A system built around a metal that gains and loses heat when compressed could lead the way to the commercialization of chemical-free refrigeration technology. 

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Refrigeration systems that use materials that cool in response to an applied electric, magnetic, or mechanical force offer environmentally friendly alternatives to the greenhouse-gas-leaking ones found in most homes and factories (see Feature: In Hot Pursuit of 21st Century Cooling). Now researchers have demonstrated a cost-effective, scalable version of one of these so-called “caloric cooling” systems [1]. Their approach, which uses a material that responds to a mechanical force, exceeds performance records set by methods that rely on magnetic fields. The researchers say their technology is also much less expensive to make and to operate and could be ready for commercial use within a year. 

In Hot Pursuit of 21st Century Cooling

Caloric materials could potentially replace conventional cooling systems with planet-friendly technology, but making them cheap and practical is a major challenge.

It’s not exactly a looker, but a five-foot tall, A-shaped engineering rig at the University of Maryland’s College Park campus could potentially evolve into a partial solution for a warming planet. At the heart of this refrigeration prototype is a material that gets cold just by being squeezed and released. It’s one of many so-called caloric materials that could provide for the world’s rapidly expanding cooling needs without exacerbating climate change. These materials cool in response to pressure, electric fields, or magnetic fields. Completely absent from this solid-state cooling concept are the volatile liquid refrigerants that are the lifeblood for just about all current cooling technologies and that are important contributors to global warming.

As the world’s billions of air conditioners, refrigerators, chillers, and dehumidifiers age and become throwaways, their refrigerants mostly leak into the atmosphere, where they trap solar radiation far more powerfully than carbon dioxide. And every day, the increasingly sweaty citizens of the planet install about 260,000 new air-conditioning (AC) units. At that rate, the number of ACs will likely balloon from the current 1.2 billion or so to 4.5 billion by 2050 [1]. The vapor-compression systems inside cooling appliances already consume about 20% of global electricity, the generation of which is a top source of humanity’s carbon dioxide emissions. Without a planet-wide redo of cooling technology, the explosive growth expected in cooling demand and supply is destined to make global warming worse. And that, in turn, will increase demand for more cooling.

Scientists at the U.S. Department of Energy's Ames Laboratory have discovered an earlier unknown discontinuous magnetoelastic transition in a rare-earth intermetallic. The mechanism of the material's changing magnetic state is so unusual, it provides new possibilities for discovery of similar materials.

Materials that possess magnetoelastic phase transitions are highly sought after for a number of developing technologies, including caloric heating and cooling systems. Materials that display this property are rare, and are thought to be exclusively transition metal-based.

But the Ames Laboratory research group found that a rare earth compound made of Europium and Indium, Eu2In, displayed a startlingly sharp magnetic phase transition accompanied with a giant magnetocaloric effect (change in temperature) and no hysteresis.

"This was a very surprising result and one of the least expected places to find such a phenomenon," said Yaroslav Mudryk, an Ames Laboratory scientist. "So this represents the first example of what potentially may become a new class of materials."

Comparative Study of the Magnetocaloric Properties of Two Anisotropic Heisenberg Systems with Spin 1/2 and 1