You probably don't think much about your refrigerator unless it breaks down in the middle of a heatwave on a public holiday.

Key points: Current cooling technologies produce greenhouse gases and cannot be scaled down to use for electronic devices

Current cooling technologies produce greenhouse gases and cannot be scaled down to use for electronic devices Applying pressure to plastic crystals causes changes at the atomic level that produce a cooling effect

Applying pressure to plastic crystals causes changes at the atomic level that produce a cooling effect The material shows potential as an eco-friendly replacement but has some disadvantages

The technology behind this workhorse, which has been with us since the 19th century, has transformed the way we live.

But the race is on to find much greener ways to keep us and our food cool in the future — and scientists are edging closer to a solution.

The idea is to replace potent greenhouse gases with solid materials that can not only be used in fridges and air conditioners, but in electronic devices too.

Led by Bing Li from the Chinese Academy of Sciences, an international team of scientists has discovered that crystals of a plastic called neopentyl glycol have the potential to do just that.

Compression and decompression of the molecules inside the crystal can produce a huge cooling effect, they report in the journal Nature.

"One cycle will cause a 50-degree difference in room temperature with very little pressure," said study co-author Dehong Yu of Australia's Nuclear Science and Technology Organisation (ANSTO).

"This is a perfect example of where we use our fundamental research to lead into a real thing that can benefit our everyday life."

Why do we need a new way of cooling?

Between 25 and 30 per cent of the world's electricity is used for refrigeration.

Your humble fridge or air conditioner relies on the compression and decompression of gases.

But there is a pressing need to find more eco-friendly and scalable alternatives to gas refrigeration, said Claudio Cazorla, a materials scientist from the University of New South Wales who wrote an independent commentary on the research.

"When your fridge is finished, the gas that is contained in the fridge is released to the atmosphere."

How your fridge works in four steps Gas heats up as it is compressed under pressure, becoming a liquid

Gas heats up as it is compressed under pressure, becoming a liquid When it comes into contact with a heat sink such as air it cools down to around room temperature

When it comes into contact with a heat sink such as air it cools down to around room temperature The liquid is decompressed, becoming colder than room temperature and absorbing heat from whatever it comes into contact with

The liquid is decompressed, becoming colder than room temperature and absorbing heat from whatever it comes into contact with It evaporates back into a gas and the process starts again

It is estimated that one kilogram of refrigerant contributes as much to the greenhouse effect as two tonnes of carbon dioxide — the equivalent of running a car uninterrupted for six months.

"Also [the gases] are toxic. If someone gets in contact with them they can have some health problems," Dr Cazorla said.

More efficient cooling technologies could drive the development of faster and more compact computers and devices, he added.

"Microchips in CPUs get hot and when they get hot they cannot work properly," Dr Cazorla said. "[But] compression and decompression of gases doesn't really work in the microscales.

"You can't put a fridge in your smartwatch, or in your iPhone."

So, for the past decade, scientists have been exploring the potential of solid-state systems that use either electrical or magnetic fields or pressure to create a cooling effect.

How do the plastic crystals work?

The plastic crystal technology works in a similar way to the four-step vapour cooling refrigeration method — but at an atomic scale.

Instead of changing the state of gas into a liquid, it uses pressure to change the structure of the plastic crystal, said Richard Mole, also of ANSTO.

The plastic crystals are made up of molecules that sit in a symmetrical lattice.

Dr Mole and Dr Yu investigated what was happening at the microscopic level using a special instrument at ANSTO called Pelican, which measures the motion of atoms in molecules when they are placed under pressure.

The degree to which the atoms jiggle around is known as entropy.

Before they are put under pressure, the atoms spin randomly around points within the lattice. But as the pressure increases, the atoms become highly ordered and line up in a crystalline structure.

When the pressure is removed, the structure reverts back to the plastic phase, where the atoms randomly rotate.

Diagram A shows the alignment of molecules in the two phases; B shows how the molecules become more or less disordered as pressure is applied and released in a four-stage cycle. ( Supplied: Cazorla/Nature )

The cooling capacity comes from the change in entropy between the two states.

"It's that degree of disorder, that degree of randomness that drives the cooling," Dr Mole said.

"Just as in a normal refrigerant where you compress the gas to be a liquid and you go from a huge degree of freedom in a gas to more confined in a liquid — this is doing the same thing but in a solid state. "

According to the researchers the cooling effect is 10 times more effective than other types of solid state materials that use electrical or magnetic fields to produce a cooling effect.

Dr Cazorla said the cooling effect demonstrated by the crystal technology was "very impressive".

"The cooling performance is very large and it is comparable to what can be achieved with gas. So this is a very important result," he said.

"This goes in the direction that maybe in the far future we could have some improved, more environmentally friendly cooling technology."

So when will it be in a fridge — or a computer — near me?

The new material ticks a lot of boxes, Dr Cazorla said.

Not only does the material have a good cooling capacity but it is cheap to synthesise out of readily available organic materials such as hydrogen, carbon and oxygen. But there is a major disadvantage.

"Your crystal has to be able to endure a large number of cooling cycles," he said.

"You can have a very good material that in one cooling cycle gets you a really good performance, but imagine that your system starts creating defects and at some point just doesn't work anymore."

Old refrigerators can leak greenhouse gases into the atmosphere. ( Getty Images: Image Source )

Unlike gases, which can be cycled again and again indefinitely, crystal lattices distort over time.

"Plastic crystals can change their state quite significantly with pressure, but also they're likely to not be able to sustain a large number of cooling cycles," Dr Cazorla said. "They're very soft, so they're not resistant."

The key to getting a new material out of the lab and into the real world, he added, is ticking all these different requirements at the same time.

Dr Mole acknowledged that the technology had only been tested over one or two cycles, to understand the physics behind the cooling effect.

"It's definitely an engineering problem that's got to be addressed, because no-one wants to buy a fridge that stops working after 1,000 cycles."

Dr Yu agreed: "We understand the mechanism from the physics point of view.

"The next problem is up to the engineers to make it into a real machine."