Researchers closer to the ultimate green 'fridge magnet'

May 15, 2009
In the summer, air conditioning and refrigeration accounts for half the USA's energy use.

(PhysOrg.com) -- Scientists are a step closer to making environmentally-friendly 'magnetic' refrigerators and air conditioning systems a reality, thanks to new research published today in Advanced Materials.

Magnetic refrigeration technology could provide a 'green' alternative to traditional energy-guzzling gas-compression fridges and air conditioners. They would require 20-30% less energy to run than the best systems currently available, and would not rely on ozone-depleting chemicals or greenhouse gases. Refrigeration and units make a major contribution to the planet's energy consumption - in the USA in the summer months they account for approximately 50% of the country's energy use.

A magnetic refrigeration system works by applying a to a magnetic material - some of the most promising being metallic alloys - causing it to heat up. This excess heat is removed from the system by water, cooling the material back down to its original temperature. When the magnetic field is removed the material cools down even further, and it is this cooling property that researchers hope to harness for a wide variety of cooling applications.

The technology, based on research funded in the UK by the Engineering and Physical Sciences Research Council (EPSRC), has proved possible in the lab but researchers are still looking for improved materials that provide highly efficient cooling at normal room temperatures, so that the technology can be rolled out from the lab to people's homes and businesses.

They need a material that exhibits dramatic heating and cooling when a magnetic field is applied and removed, which can operate in normal everyday conditions, and which does not lose efficiency when the cooling cycle is repeated time after time.

The new study published today shows that the pattern of crystals inside different alloys - otherwise known as their - has a direct effect on how well they could perform at the heart of a magnetic fridge. The Imperial College London team behind the new findings say this could, in the future, help them to custom-design the best material for the job.

Professor Lesley Cohen, one of the authors of the paper, explains that by using unique probes designed at Imperial, her team, led by Dr James Moore, was able to analyse what happens to different materials on a microscopic level when they are magnetised and de-magnetised. This enabled the team to pinpoint what makes some materials better candidates for a magnetic fridge system than others.

Professor Cohen, from Imperial's Department of Phsyics, said: "We found that the structure of crystals in different metals directly affects how dramatically they heat up and cool down when a magnetic field is applied and removed. This is an exciting discovery because it means we may one day be able to tailor-make a material from the 'bottom up', starting with the microstructure, so it ticks all the boxes required to run a magnetic fridge. This is vitally important because finding a low-energy alternative to the fridges and air conditioning systems in our homes and work places is vital for cutting our carbon emissions and tackling climate change."

This new research follows on from another study published by the same Imperial group in Physical Review B last month, in which they used similar probing techniques to precisely measure the temperature changes that occur when different materials are removed from a magnetic field, and to analyse the different ways they occur.

The lead scientist Kelly Morrison found that at the molecular level two different temperature change processes, known as first- and second-order changes, happen simultaneously in each material. The team think that the extent to which each of these two processes feature in a material also affects its cooling capabilities.

Professor Cohen says this means that whilst the majority of research to perfect magnetic refrigeration worldwide has tended to involve analysing and testing large samples of materials, the key to finding a suitable material for everyday applications may lie in the smaller detail:

"Our research illustrates the importance of understanding the microstructure of these materials and how they respond to magnetic fields on a microscopic level," she concluded.

More information:

1. 'Metamagnetism seeded by nanostructural features of single crystalline Gd5Si2Ge2', Advanced Materials, XX May 2009.

2. 'Capturing first- and second-order behavior in magnetocaloric CoMnSi0.92Ge0.08', Physical Review B, 6 April 2009.

Source: Imperial College London (news : web)

Explore further: Optimum inertial self-propulsion design for snowman-like nanorobot

add to favorites email to friend print save as pdf

Related Stories

Towards the magnetic fridge

Apr 21, 2006

Researchers at the University of Cambridge have discovered a material that gives a whole new complexion to the term 'fridge magnet'. When this alloy is placed in a magnetic field, it gets colder. Karl Sandeman and his co-workers ...

Milestone in magnetic cooling

Aug 24, 2007

The first milestone in magnetic cooling has been achieved. Between 5 and 10 degrees of cooling – this was the success criteria for the first milestone in a project involving magnetic cooling at Risø National Laboratory ...

Compressor-free refrigerator may loom in the future

Aug 07, 2008

Refrigerators and other cooling devices may one day lose their compressors and coils of piping and become solid state, according to Penn State researchers who are investigating electrically induced heat effects of some ferroelectric ...

Recommended for you

A transistor-like amplifier for single photons

17 hours ago

Data transmission over long distances usually utilizes optical techniques via glass fibres – this ensures high speed transmission combined with low power dissipation of the signal. For quite some years ...

User comments : 7

Adjust slider to filter visible comments by rank

Display comments: newest first

mo411
1.7 / 5 (3) May 15, 2009
Magnetocaloric effect exposes a conceptual flaw in discussing the concept. Magneto refrigeration has been around for quite some time (several decades) and still relegated to the lab. Material scientists have a propensity to look for optimum performance of the material involved hence the technology remains in the lab as apposed to commercially viable alternative to propellant based refrigeration methods. In other words, why not deliver to market cooling systems based on reasonable material today? Pick an industry, say the automotive market? Magneto refrigeration is on par with propellant refrigeration and in the transport industry the limited moving parts makes quite a bit of sense. Getting something to market will prove viability far quicker then what has transpired in the labs around the world...
E_L_Earnhardt
1 / 5 (1) May 15, 2009
AMEN, AMEN, and AMEN! THANK YOU, "BRITS", THANK YOU,"mo411" ! This is way past due!
jyro
2 / 5 (4) May 15, 2009
In 1957 I was promised a flying car by 2000, I think it was the same family of scientists.
Physic
not rated yet May 15, 2009
???
Does that include all energy, trucks, planes, factories etc. That sounds like an over-estimation
tkjtkj
not rated yet May 16, 2009
Knowing nothing about this topic, im nonetheless intrigued: but: toa degree, it seems to resemble a 'perpetual motion ' machine:
Under a magnetic field, a device gets 'hot' and the heat is removed by water, which makes the device cool .. Now, didnt we heat it up first?? Just where is the energy flow picture?
earls
5 / 5 (1) May 16, 2009
You're mixed up, tkjtkj.

I don't know what other example you're trying to tie to "magnetic refrigeration", but it couldn't be more simple.

The hot, disordered coolant is subjected to a magnetic field which cause the coolant to become ordered releasing heat and cooling. The coolant then passes by the hotter whatever you're trying to cool, absorbs the heat and becomes disordered again. The process then repeats itself.

Check out the "Related Stories" for graphics and examples.
medium
not rated yet Jun 16, 2009
The CAS or cells alive system keeps frozen food fresh and better tasting much longer then a normal freezer. Will these new magnetic refrigerators keep food longer ?