The World Needs a New Way to Keep People Cool

If you live in a place with hot summers, you know how refreshing it feels to step into a cool, air-conditioned building after being outside. But air conditioning is more than just a luxury—it can be a lifesaver. High temperatures can be dangerous, especially for children, older adults, and people with certain health conditions. Having access to cool indoor spaces can prevent heat-related illnesses and even save lives during extreme heatwaves.

As global temperatures rise, the need for cooling is growing quickly. By 2050, the energy used for air conditioning and refrigeration is expected to more than triple [1]. Most cooling systems today rely on electricity, much of which comes from burning fossil fuels. The more energy we use, the more greenhouse gases are released into the atmosphere, making climate change even worse. There is another problem: refrigerant gases used in cooling systems, like freon or hydrofluorocarbons. These chemicals cool the air but can leak into the environment, trapping heat and contributing to global warming. Some refrigerants are thousands of times more harmful to the climate than carbon dioxide.

In places where electricity is limited or expensive, many people cannot rely on air conditioning to stay cool. This means that millions of people, especially in developing countries, may not have a safe way to cope with extreme heat. We need a new kind of cooling system—one that uses less energy, avoids harmful chemicals, and works even in areas where electricity is scarce.

Emerging Technology: Elastocaloric Heat Pumps

Most cooling systems today rely on a process called vapor-compression cooling, which uses refrigerant gases. These gases are compressed to release heat and then expanded to absorb heat, cooling the surrounding air. While effective, this process uses a lot of electricity to power the compressor—in addition to relying on dangerous refrigerant gases.

Elastocalorics could offer a new, better way to cool and heat spaces by mimicking how muscles work. When you stretch a muscle, it heats up slightly because the molecules inside it rearrange and rub against each other, generating heat. When you relax the muscle, it cools down as the tension is released and absorbs heat from its surroundings. Elastocaloric heat pumps use materials that behave similarly—releasing heat when stretched or compressed and absorbing heat when relaxed.

Instead of harmful refrigerant gases, elastocaloric systems use shape-memory alloys made of metals like nickel and titanium. These metals can come in various forms, like flexible strips or coils, tubes, or other advanced structures. When shape-memory alloy structures are stretched or squeezed by a machine, they heat up. The heat generated can be transferred to a fluid like water or air, which carries it away and releases it outside the building. When the pressure is released, the metal relaxes and returns to its original shape, cooling down and absorbing heat from the surrounding air or water in the process. This absorbed heat is carried away by the fluid in the next cycle, ensuring that the room or building stays cool. This cooling cycle repeats over and over, and the shape-memory alloys can handle millions of cycles without breaking down.

Tech to The Rescue

One big advantage of elastocaloric heat pumps is their efficiency. By directly converting mechanical (stretching/compressing and relaxing) energy into cooling, they skip the energy-intensive steps of compressing and expanding refrigerant gases used in traditional systems. This means elastocaloric heat pumps use less electricity, making them an environmentally friendly and cost-effective alternative [2]. Elastocaloric heat pumps could be especially useful in areas where electricity is limited or expensive [3].

Elastocaloric technology is already showing promise for heating and cooling. Researchers are testing elastocaloric heat pumps as replacements for traditional air conditioners (Figure 1C). These systems could cool homes, schools, and workplaces more efficiently while reducing greenhouse gas emissions. Elastocalorics also has potential for refrigeration, especially in areas where electricity is limited. In rural communities or developing countries, elastocaloric heat pumps could provide an affordable way to keep food fresh or medicines cool (Figure 1A). Because they use less energy, elastocaloric systems can run on smaller, renewable energy sources, like solar panels, which are often more practical in these settings.

Elastocaloric technology is also being explored for electric vehicles. Current car heating and cooling systems use a lot of energy and can quickly drain car batteries, reducing the driving range of electric cars. Elastocaloric technology could offer a more efficient solution, helping electric vehicles maintain comfortable temperatures while conserving energy—making these cars more practical and appealing to drivers (Figure 1B).

In addition to cooling, elastocaloric heat pumps could also improve heating systems in colder climates. By reversing the process—absorbing heat from the outside air and releasing it indoors—they could efficiently warm homes and buildings, providing an all-in-one solution for temperature control.

Big Challenges, Bigger Opportunities

Before elastocaloric technology is widely used to keep us cool, there are some challenges to solve. One big challenge is the durability of the materials. Shape-memory alloys can handle millions of cycles of stretching and relaxing, but researchers are working to improve their lifespan and performance, to make them more cost-effective for large-scale use. Another challenge is designing the machinery that stretches and relaxes the materials efficiently from an energetic point of view: these systems must be precise, durable, and energy efficient to compete with the commonly used vapor compression cooling systems. Engineers are testing different designs, like advanced motors or rotating mechanisms, to create the stretching motion in a continuous cycle. Another issue is the cost of producing the specialized metal alloys needed for elastocaloric systems. These alloys are expensive, so researchers are looking for cheaper ways to manufacture them in large quantities. Making these materials affordable is key to ensuring this technology can be used all over the world.

If researchers can overcome these challenges, elastocaloric technologies could reduce greenhouse gas emissions, lower energy costs, and expand access to cooling and heating, helping people all over the world to keep cool.

Glossary

Refrigerant: ↑ A solid or liquid material used in air conditioners and refrigerators to cool the air. Some refrigerants, mainly the fluids, can harm the environment if they leak.

Vapor-Compression Cooling: ↑ A process that cools air by compressing and expanding refrigerant fluids. This method is used in most air conditioners and refrigerators today.

Elastocalorics: ↑ A cooling technology that uses shape-memory alloys that heat up or cool down when squeezed or relaxed, providing an energy-efficient way to control temperatures.

Shape-Memory Alloys: ↑ Metal mixtures, often nickel and titanium, that return to their original shape after being stretched or squeezed. Their ability to handle repeated stretching and relaxing makes them essential for elastocaloric cooling.

Conflict of Interest

The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

Acknowledgments

Co-written and edited by Susan Debad Ph.D., graduate of the UMass Chan Medical School Morningside Graduate School of Biomedical Sciences (USA) and scientific writer/editor at SJD Consulting, LLC. Figure created by Somersault18:24.