University of Texas at Dallas researchers and their collaborators have developed and patented a wood-based material that can store and discharge heat to help make building temperatures more comfortable without using electricity.
"Our material acts as a thermal battery that charges as it absorbs heat," said Dr. Shuang (Cynthia) Cui , assistant professor of mechanical engineering in the Erik Jonsson School of Engineering and Computer Science .
Cui is corresponding author of a study describing the material that was published in the December issue of Materials Today Energy as part of the 2025 Promising Early Career Scientists Special Issue.
The UT Dallas team collaborated with researchers from institutions including the National Renewable Energy Laboratory — recently renamed the National Laboratory of the Rockies — which supported the project, the University of Colorado Boulder, the Lawrence Berkeley National Laboratory and the University of California, Berkeley. Cui, a Fellow, Eugene McDermott Distinguished Professor, holds a joint faculty appointment at the national laboratory in the Rockies, where she previously was a postdoctoral researcher and research scientist.
The approach involves phase-change materials, which collect heat as they melt and release it as they solidify. Such materials could potentially be incorporated into drywall, flooring or roofing to reduce electricity demands and improve energy efficiency.
"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," Cui said. "If the building has enough phase-change material incorporated, the air conditioning may not need to be turned on."
Thermal energy storage is an emerging approach to manage energy loads in buildings.
"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," said Bernadette Magalindan BS'21, MS'25, a mechanical engineering doctoral student in Cui's lab and a Department of Energy Innovation in Buildings Graduate Research Fellow .
Phase-change materials can leak when they transition to liquids, which presents a challenge to their use. One approach to the problem is to enclose the materials within a host material to prevent leakage. Although this solution can work, it is not as effective because the host material does not store heat.
To address the issue, the researchers removed lignin, a substance in plant cells that provides structure and stiffness, from wood to create a spongelike structure with tiny pores. They filled the structure with a phase-change material mixed with an ingredient that forms into soft plastic. The soft plastic holds the phase-change material in place, even when it melts, and strengthens the wood. The resulting material did not leak or degrade over 1,000 phase-change cycles.
"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," said Dr. Hongbing Lu , one of the study's co-authors and professor of mechanical engineering, the Louis Beecherl Jr. Chair and director of the Mechanics of Advanced Materials Laboratory .
The researchers plan to continue to improve and commercialize the technology.
"It was exciting to be part of this project, which is showing promising results for more comfortable, energy-efficient buildings," said Gustavo Felicio Perruci, a co-author of the study and a mechanical engineering doctoral student who is 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."
