A team of researchers from the University of California Santa Barbara (UCSB) has created a roof tile capable of passively regulating temperature via a wax motor that opens and closes louvres located on the tile’s surface.

According to the UCSB team, this is accomplished due to the change in the volume of wax in response to temperature, wherein wax motors — which are often found in appliances like washing machines and dishwashers, for instance — create pressure that moves mechanical parts, thereby translating thermal energy into mechanical energy.

On the tile roof, the researchers explained, the wax motor pushes or retracts pistons that alter the surface and, ultimately, its function. Under cooler temperatures, the wax is solid, and the louvres remain closed and lay flat. In that position, the surface is exposed to sunlight, which is absorbed and heat dissipation is consequently minimized via radiation. Conversely, as temperatures reach 18° C, the wax starts melting and expanding, thereby forcing the louvres open and exposing a surface that both reflects sunlight and emits heat.

“It switches between a heating state and a cooling state, depending on the temperature of the tile,” explained the researchers. “The target temperature is about 65° F — about 18° C.”

During testing, the researchers reported that the tile reduced energy consumption for cooling by 3.1 times and heating by 2.6 times versus non-switching devices.

Further, the wax motor requires no electronics, batteries or external power sources to operate.

The technology is detailed in the article, “Passively adaptive radiative switch for thermoregulation in buildings, which appears in the journal Device.

To contact the author of this article, email mdonlon@globalspec.com