This adaptive roof tile can cut both heating and cooling costs

This adaptive roof tile can cut both heating and cooling costs
by Clarence Oxford
Los Angeles CA (SPX) Dec 18, 2023

In an era where energy efficiency is paramount, researchers at the University of California, Santa Barbara (UCSB) are making significant strides. A team, comprising Charlie Xiao, Elliot Hawkes, and Bolin Liao, has developed an adaptive roof tile that could revolutionize how we manage heating and cooling in buildings.

Approximately half of an average American building's energy consumption goes towards heating and cooling, representing a substantial financial and environmental cost. Addressing this issue, the UCSB researchers presented their innovative solution in the journal Device. The team's adaptive tile, designed for array deployment on roofs, promises to lower heating bills in winter and cooling bills in summer, all without relying on electronics.

"The target temperature is about 65F - about 18C," explained Xiao, the study's lead author. This simple yet effective approach hinges on the tile's ability to switch between heating and cooling states based on its temperature. The tile, measuring approximately four inches square, is the fruit of a unique collaboration that merges Liao's expertise in thermal science with Hawkes' background in mechanism design.

The project's genesis traces back to long drives between Santa Barbara and Northern California, where both researchers' spouses were located at Stanford at the time. These journeys sparked the idea of a mechanically tunable thermal device, which later received seed funding from the California NanoSystems Institute at UCSB.

The pivotal component in this venture is the wax motor, an idea proposed by Xiao. Responding to temperature changes, the wax motor leverages the volume change in wax to create pressure that actuates mechanical parts. This conversion of thermal energy into mechanical energy is key to the tile's function. Wax motors are not new; they find applications in household appliances and even in the aerospace industry.

In practical terms, the wax motor in these tiles controls pistons that open or close louvers on the tile's surface. At lower temperatures, with the wax solidified, the louvers remain closed, presenting a surface that absorbs sunlight and retains heat. Conversely, as temperatures approach 18C and the wax melts, the louvers open, revealing a surface that reflects sunlight and dissipates heat.

Moreover, during the wax's phase change, it either absorbs or releases heat, further stabilizing the building's temperature. Xiao highlights the predictability and efficiency of this mechanism, noting that testing has shown a 3.1x reduction in cooling energy consumption and a 2.6x reduction in heating energy needs compared to non-switching devices.

The absence of electronics, batteries, or external power sources in operating this device is a significant advantage, making it both environmentally friendly and cost-effective. Furthermore, its design lends itself to customization and mass production, with different thermal coatings and wax types allowing for operation at various desired temperature ranges.

While currently a proof-of-concept, the UCSB team is optimistic about the future applications of their invention. "The device is still a proof-of-concept, but we hope it will lead to new technologies that one day could have a positive impact on energy expenditure in buildings," said Hawkes.

This innovation from UCSB not only represents a novel approach to building design but also aligns with the broader goal of reducing energy consumption and environmental impact. As the world continues to seek sustainable solutions, technologies like the adaptive roof tile demonstrate how creative engineering can lead to significant advancements in energy efficiency.

Research Report:Passively adaptive radiative switch for thermoregulation in buildings