Adaptive roof tile harnesses wax motor to heat and cool

Based on the change in the volume of wax in response to temperature, a wax motor creates pressure that moves mechanical parts, translating thermal energy into mechanical energy. Wax motors are commonly found in appliances like dishwashers and washing machines, as well as in more specialised applications such as the aerospace industry.

In the case of the tile, the wax motor can push or retract pistons that change the nature of its surface and alter its function. In cooler temperatures when the wax is solid, the louvres are closed and lay flat, exposing a surface that absorbs sunlight and minimises heat dissipation through radiation. When temperatures reach around 18° C, the wax begins to melt and expand, pushing the louvres open and exposing a surface that reflects sunlight and emits heat. The tile is described in the journal Device.

“It switches between a heating state and a cooling state, depending on the temperature of the tile,” explained lead author Charlie Xiao, from the University of California Santa Barbara (UCSB). “The target temperature is about 65° F — about 18° C.”