As global temperatures rise, the demand for air conditioning is surging, driving up energy bills and straining power grids. In the United States, air conditioning accounts for nearly one-fifth of all residential electricity use, and cooling systems in commercial buildings consume about one-third of their total energy. To meet this energy need, a team of researchers at Penn State is developing new materials that cool their surroundings when bent or stressed. On the latest episode of "Growing Impact," the team discusses how this cutting-edge technology could transform the future of building climate control.
"Fundamentally, many cooling technologies move heat in the opposite direction from where it wants to go. You're trying to pump heat against its gradient," explained Herschel Pangborn, assistant professor in the Department of Mechanical Engineering and a collaborator on the project. "Traditional systems rely on large compressors and fans that consume significant electrical energy. Our goal is to harness mechanical energy, such as vibration or compression, and use specialized materials to drive heat where it's needed for cooling."
The focus of the research is on shape memory alloys (SMAs), a class of materials that change shape when mechanical force is applied and return to their original form when the force is removed. During this process, SMAs absorb heat, a phenomenon known as the elastocaloric effect. By leveraging this effect, the team aims to create cooling systems that are not only highly efficient but also free from the environmentally harmful refrigerants used in conventional air conditioners.
"Elastocaloric cooling offers an efficient and environmentally friendly alternative to traditional systems," said Wenjie Li, the project's principal investigator and an associate research professor of materials science and engineering. "This technique eliminates the need for harmful chemicals and can be more energy efficient than conventional methods."
The researchers are developing new types of SMAs using advanced computer modeling and additive manufacturing, specifically 3D printing in this case, to tailor the materials for optimal performance. Their approach looks to enable the design of miniature cooling devices and scalable systems suitable for a wide range of applications, from smart buildings to personal electronics.
One of the project's key goals is to harvest mechanical energy from everyday activities. For example, the pressure from footsteps on a floor or keystrokes on a laptop could trigger the elastocaloric cooling effect, turning wasted energy into useful cooling.
"Our vision is to integrate these materials into future smart buildings, where even small mechanical pressures can activate cooling," Li said. "A major challenge we're addressing is reducing the amount of force required to trigger the effect, making the technology practical for real-world use."
Computer modeling plays a crucial role in optimizing the materials and system design, allowing the team to predict performance and guide their experimental work. By capturing energy that would otherwise go unused, this technology has the potential to reduce the environmental impact of air conditioning and refrigeration, the researchers said.
"Instead of drawing more power from the grid, we're looking to use the mechanical energy already present in our environment," Pangborn added. "Just as solar panels and wind turbines capture renewable energy, our approach extracts mechanical energy from motion and converts it into cooling. It's a new way of thinking about energy use in buildings."
"Growing Impact" is a podcast by the Institute of Energy and the Environment. It features Penn State researchers who have been awarded IEE seed grants and discusses their foundational work as they further their projects. The podcast is available on multiple platforms, including YouTube, Apple, Amazon and Spotify.
