Drexel University engineers have developed novel cement-based materials incorporating phase-change technology to improve building energy efficiency, inspired by the natural temperature regulation found in elephant ears.
Researchers at Drexel University have introduced groundbreaking cement-based building materials designed to enhance energy efficiency through innovative passive heating and cooling mechanisms. This breakthrough, inspired by the naturally effective temperature regulation systems observed in elephant and jackrabbit ears, could revolutionize building design by embedding a vascular network within walls, floors and ceilings, significantly reducing energy consumption.
The research, published in the Journal of Building Engineering, showcases a new method devised by Drexel’s Advance Infrastructure Materials (AIM) Lab. It involves integrating paraffin-based phase-change materials (PCMs) into a printed polymer matrix within cement surfaces.
PCMs have the unique ability to absorb and release thermal energy as they transition between liquid and solid states, effectively regulating surface temperatures.
“Architecturally, it looks nice to have a lot of window area on a building, but this also results in diminished insulation properties,” co-author Rhythm Osan, an undergraduate student in Drexel’s College of Engineering, said in a news release. “In an ideal world, a building wouldn’t lose any heat, but from a realistic constructability standpoint, issues like thermal bridging, air leakage from ducts, material performance and joint detailing will always pose some heat loss.”
The team’s innovative approach aims to counterbalance the substantial energy demand of buildings, which account for nearly 40% of all energy use globally, with about half of that energy spent on maintaining comfortable indoor temperatures.
Notably, surfaces such as walls, windows and ceilings are responsible for approximately 63% of energy loss in buildings, making the Drexel team’s solution potentially transformative.
“Look at the way our circulatory system is used to regulate temperature. When it’s hot out, blood runs to the surface — we might get a little red in the face and begin to sweat through our glands and this cools us down through a phase-change process — sweat evaporation,” added Amir Farnam, an associate professor in Drexel’s College of Engineering who led the research. “This is a very effective, natural process that we wanted to replicate in building materials.”
The study tested various vascular channel configurations and thicknesses to determine the optimal design for mechanical strength and thermal performance.
The diamond-shaped grid channel architecture emerged as the most effective, offering both structural integrity and superior temperature regulation, slowing surface heating and cooling to 1-1.25 degrees Celsius per hour.
“We found, perhaps not surprisingly, that more vasculature surface area equates to better thermal performance. This observation is similar to physiology of elephant and jackrabbit ears, which contain extensive areas of vasculature to help regulate their body temperature,” added co-author Robin Deb, a research scientist in the AIM Lab. “We believe that our vascular materials could play a similar role in a building by helping to offset temperature shifts and reduce energy demand from HVAC to maintain thermal comfort.”
While this study served as proof of concept, the team’s promising results pave the way for further exploration. Future research will involve testing different PCMs, channel patterns and larger material samples over more extended periods and varied environmental conditions.
“While this study was intended to show a proof of concept, these results are promising and something we can build on,” Farnam added. “This shows both the effectiveness of this method for regulating surface temperature in cementitious materials, as well as a simple and cost-effective method for producing them. With additional testing and scaling, we believe this has the potential to make a significant contribution to the many ongoing efforts to improve the energy efficiency of buildings.”
This innovation holds the promise of making building structures more self-sufficient in temperature control, reducing reliance on external energy sources, and significantly cutting greenhouse gas emissions.
Source: Drexel University