In the dark depths of solid-state physics labs, a new breed of environmentally concerned scientists is emerging. Their research might seem obscure to those with no background in magnetic domains, hysteresis curves and phase transitions, but the application of their work could have far reaching effects on the way we store our food. Their aim? To change the way our refrigerators remain cold.
Since the late nineteenth century, it has been known that it was possible to change the temperature of a magnetic metal by exposing it to a varying magnetic field at very low temperatures, such as near absolute zero.
By increasing the magnetic field, the metal becomes more disordered and from the laws of thermodynamics it heats up. This heat can then be removed, using a fluid or a gas, so that the metallic material returns to its original temperature. If the applied magnetic field is then decreased, the metal’s temperature drops even lower.
Analogy between magnetic refrigeration and vapor cycle or conventional refrigeration. H = externally applied magnetic field; Q = heat quantity; P = pressure; ΔTad = adiabatic temperature variation – Courtesy of Wikipedia
However, in 1997, Professor Gscheneider, Jr. at the Iowa State University discovered that magnetic cooling was actually possible at room temperatures, leading to a wave of research into the idea of using magnets to provide refrigeration.
“Someone happened to measure what the temperature change was near room temperature and reported the paper and it spread throughout their scientific community…it’s a bit like [the history of] superconductivity” said Dr James Moore, a researcher at Imperial College London who recently published a study in the journal Advanced Materials and is on a quest to produce magnetically-cooled fridges.
Moore’s research focuses on what happens to different metallic materials on a microscopic level when they are magnetised and demagnetised.
“The title of our project is called Solid State Energy Efficient Cooling”, said Moore. “We do materials research into different metallic alloys which show these effects and the whole drive is that the end application would go into a magnetic refrigerator, just like a fridge in your home.”
Magnetic fridges are more efficient, with up to 60% efficiency compared to current refrigeration techniques that rely on gas compression. Another benefit is that they would not contain ozone-depleting gases and would be easier to dispose of at the end of their lifetime.
But, current research relies on expensive metal alloys such as gadolinium, so Moore and his team are desperately trying to find cheaper alternatives. However, they are optimistic that the technology will take off.
“I don’t think you’ll see it in people’s homes straight away, it’ll probably enter more with niche applications and then it will grown from there. But the hope is in the next 4-5 years” advised Moore.
A typical fridge – courtesy of Wikipedia
Refrigerators and air conditioning units are one of the biggest contributors to global energy consumption – in the USA they account for around half of all of the country’s summer energy use. If Moore and his team, in conjunction with their European collaborators, can harness this magnetic power to produce more environmentally friendly fridges then this will have a significant impact on cutting carbon emissions and tackling climate change.