Engineers at UT Dallas have turned ordinary wood into a kind of thermal battery that can store and release heat without electricity. The durable, leak-free material could one day help buildings stay comfortable while using far less energy.
A team of engineers has turned everyday wood into a kind of thermal battery that could help buildings stay comfortable while using far less energy.
Researchers at The University of Texas at Dallas and their collaborators have developed and patented a wood-based material that stores and releases heat, potentially easing the load on air conditioners and heaters. The work, published in the journal Materials Today Energy, is part of a growing push to make buildings more energy efficient as climate change drives up demand for cooling and heating.
The key idea is to use wood as a scaffold for phase-change materials, or PCMs. These are substances that absorb heat as they melt and release it as they solidify, much like ice soaking up heat when it turns to water and giving it back as it refreezes.
The new composite behaves like a rechargeable heat pack built into the walls, according to corresponding author Shuang (Cynthia) Cui, an assistant professor of mechanical engineering in UT Dallas’ Erik Jonsson School of Engineering and Computer Science.
“Our material acts as a thermal battery that charges as it absorbs heat,” Cui said in a news release.
In buildings, that kind of passive thermal storage could be powerful. Instead of relying entirely on mechanical systems, parts of the structure itself could help smooth out temperature swings over the course of a day.
Cui explained that the material is designed to soak up excess heat when temperatures climb and then slowly release it as conditions cool.
“During the summer, for example, the phase-change material will absorb and store heat from the exterior, which would reduce the rise of room temperature,” she said. “If the building has enough phase-change material incorporated, the air conditioning may not need to be turned on.”
That concept, known as thermal energy storage, is attracting attention as a way to reduce peak electricity demand and better use renewable energy. Instead of wasting heat when it is abundant, buildings can bank it for later.
“Thermal energy storage offers a solution by harnessing excess heat from the environment for later use — such as storing daytime heat to provide warmth during cold nights,” added co-author Bernadette Magalindan, a mechanical engineering doctoral student in Cui’s lab and a U.S. Department of Energy Innovation in Buildings Graduate Research Fellow.
But PCMs come with a major drawback: many of them melt into liquids, which can leak out of whatever they are embedded in. One common workaround is to seal the PCM inside capsules or mix it into a separate host material. That can prevent leaks, but the host material usually does not store heat itself, limiting overall performance.
The team tackled this problem by re-engineering wood from the inside out.
Wood is naturally made of several components, including lignin, which gives plants stiffness and structure. The researchers removed lignin from the wood, leaving behind a spongelike framework riddled with tiny pores. This porous skeleton became a template for the PCM.
They then infused the wood with a phase-change material blended with an ingredient that turns into a soft plastic. When the PCM melts, the soft plastic helps hold it in place, preventing leaks and reinforcing the wood at the same time.
The result is a composite that can repeatedly melt and solidify without oozing or falling apart. In tests, the material did not leak or degrade over 1,000 heating and cooling cycles, suggesting it could stand up to years of daily use in a building.
Co-author Hongbing Lu, a professor of mechanical engineering, the Louis Beecherl Jr. Chair and director of the Mechanics of Advanced Materials Laboratory at UT Dallas, emphasized that durability is just as important as energy performance.
“Unlike many energy-storage materials that sacrifice strengths, these wood-templated phase-change composites maintain mechanical integrity under repeated heating and cooling cycles, making them both energy efficient and mechanically durable, which are critical for long-term use in buildings,” Lu said in the news release.
Because the composite starts as wood, it could potentially be adapted for use in building components such as wall panels, flooring, or roofing materials. If manufactured at scale, such products might help reduce the size or runtime of conventional HVAC systems, cutting both energy bills and greenhouse gas emissions.
The project also highlights how university researchers and national laboratories can work together on climate and energy challenges. The UT Dallas team collaborated with scientists at the National Renewable Energy Laboratory, recently renamed the National Laboratory of the Rockies, as well as the University of Colorado Boulder, Lawrence Berkeley National Laboratory, and the University of California, Berkeley. Cui holds a joint appointment at the national lab in the Rockies, where she previously worked as a postdoctoral researcher and research scientist.
For students involved in the work, the project offered a front-row seat to the process of turning a lab concept into a potential commercial technology.
“It was exciting to be part of this project, which is showing promising results for more comfortable, energy-efficient buildings,” added co-author Gustavo Felicio Perruci, a mechanical engineering doctoral student co-advised by Lu and Cui. “Working with our national lab partners gave me invaluable experience and opened important doors, demonstrating how interdisciplinary teams can turn sustainable materials into real-world solutions.”
The researchers plan to keep refining the material and exploring how it could be integrated into real buildings. Future steps include optimizing the composition for different climates, testing larger-scale prototypes, and working with industry partners to move the technology toward market.
If successful, wood-based thermal batteries could become a quiet but powerful ally in the effort to make homes, schools, and offices more sustainable — simply by letting the walls do more of the work.