RMI, Magnotherm & Phononic: Creating Sustainable AC Systems

While Earth’s climate has changed throughout its history, the current warming is happening at a rate not seen in the past 10,000 years.

As the planet heats up, the demand for cooling systems is soaring, with the US$235bn global cooling market projected by Morgan Stanley to more than double by 2030.

Conventional air conditioning, with its high energy consumption and potent greenhouse gas emissions, is unsustainable. 

However, solid-state cooling, magnetocaloric and thermoelectric systems offer a new generation of cooling technologies that are emerging to reduce environmental harm while improving efficiency.

The climatic cost of AC systems

Earth was about 2.65°F (1.47 °C) warmer in 2024 than in the late 19th-century (1850-1900) preindustrial average. 

The 10 most recent years are the warmest on record.

With temperatures rising, meeting the increasing demand of cooling systems--  without further driving climate change – is one of the most urgent technology challenges of the decade. 

Air conditioning is currently responsible for a significant share of global energy use and emissions. 

Despite the predicted doubling of the global cooling market, the most common technologies remain reliant on hydrofluorocarbons (HFCs) — synthetic refrigerants with extremely high global warming potential. 

These gases frequently leak from systems, reducing efficiency and causing environmental damage.

Alternatives like propane, ammonia and carbon dioxide each have drawbacks: flammability, toxicity and high-pressure requirements respectively. 

As these are phased in, it is increasingly clear that replacing refrigerants alone won’t solve the problem.

Solid-state cooling systems offer a fundamentally different approach. 

Rather than using liquid refrigerants to transfer heat, they rely on physical forces — such as magnetism, pressure or electric current — to induce temperature changes.

“Not only do they eliminate those super-polluting refrigerants, but they can also offer improved efficiency to the systems,” says Lindsay Rasmussen, Manager and Building Sector Lead at RMI.

These technologies operate without moving parts, making them quieter, more compact and more reliable. 

“That's because there's zero moving parts, the heat is occurring because of the reaction in the material level,” says Lindsay Rasmussen.

Magnetocaloric and Elastocaloric cooling systems

Among the most promising solid-state technologies is magnetocaloric cooling. 

Magnetocaloric cooling is a refrigeration technology that relies on the magnetocaloric effect (MCE), a physical phenomenon observed in certain magnetic materials. 

When these materials are exposed to a changing magnetic field, they undergo a reversible temperature change – heating up when a magnetic field is applied and cooling down when the field is removed.

German company, Magnotherm, is at the forefront of commercial development in this space.

“With our technology, it's inherently safe because it's not toxic, it's a metal and we operate at very low pressures,” says Timur Sirman, CEO and Co-Founder of Magnotherm. 

Elastocaloric cooling is also solid-state refrigeration technology that exploits the elastocaloric effect, a phenomenon where certain materials undergo a temperature change when subjected to mechanical stress.

When mechanical stress is applied to an elastocaloric material, it triggers a phase transformation, releasing latent heat and causing the material to heat up. 

When the stress is removed, the material absorbs heat and cools down – cycling the material between stressed and unstressed states creates a continuous refrigeration effect.

Projects like SMACool in Europe are experimenting with elastocaloric systems that use tubes made from these alloys to deliver effective air conditioning without refrigerants.

While elastocaloric devices are still in the prototype phase, recent breakthroughs have shown promising results. 

A team in Hong Kong recently developed a system achieving 1,284W of cooling power — surpassing the 1,000W threshold for the first time. 

Innovations like using graphene nanofluids instead of water for heat transfer are helping improve performance.

Thermoelectric cooling and future directions

Thermoelectric cooling systems use semiconductor materials to move heat through the application of electrical energy. 

These compact, chip-like devices can be easily integrated into various systems and require far less maintenance than traditional air conditioning.

“Our chips are really thin, really small, but they get really cold. They consume a small amount of electricity in generating that coldness, but they pack one hell of a punch,” says Tony Atti, Co-Founder and CEO of Phononic.

In contrast to vapour-compression systems, which must run continuously, thermoelectric systems offer on-demand cooling that reduces energy use and operational noise. 

“We like to present the coolness on demand where you need it,” says Tony.

Although solid-state technologies are not yet as powerful or affordable as conventional A/C, rapid progress is being made. 

“Can these technologies scale up to where they could be affordable for those who need it the most and where the greatest demand for cooling is coming from?” questions Lindsay Rasmussen.

If these solutions can be scaled, they offer a way to meet global cooling needs without worsening the climate crisis. 

Sustainable cooling will be essential not only for comfort, but for public health, productivity and economic resilience in a warming world. 

The challenge now is ensuring the transition from high-emission systems to low-impact technologies is both swift and inclusive.

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