(Video credit: TED.com)
In this TEDxUSC talk, Doris Kim Sung shares how she is incorporating her biology training to design more energy efficient and dynamic buildings.
Buildings could be more dynamic if their exteriors were designed like human skin—which regulates body temperature— to be responsive to environmental conditions. Sung talks about incorporating smart materials into building materials to take advantage of natural light, sunlight. Sung refers to these smart materials as thermo-bimetals. They require no energy input and are self-activated. These thermo-bimetals consist of two different metals that are laminated together. The metals have different coefficients of thermal expansion, which means they expand at different rates when heated.
You’ve probably already seen this type of bimetallic material in action, right in your home’s thermostat! The bimetallic material in thermostats consists of one metal with a smaller coefficient of thermal expansion than the other. As the temperature increases the metal with the large coefficient expands more, causing the material to curl upwards. The bimetallic strip in thermostats is used as the arm of a switch between electrical contacts. The strip bends as the room temperature changes. When the strip bends far enough, it contacts the electrical leads that turn the heat or air conditioning on or off.
Ok, now back to how these thermo-bimetals can be used in buildings.
Sung shows a canopy installation at the Materials and Applications Gallery in Silver Lake, California that is made entirely of the thermo-bimetal. The canopy is a sunshading device and the surface constricts how much sun passes through. It also acts as a ventilation system so hot trapped air can move through when necessary. The thermo-bimetal pieces of the canopy moves with the Sun, and there are 14,000 unique pieces. Each piece is calibrated to the angle of the Sun and varies in how it curls.
This new application of thermo-bimetals in architecture means buildings can be tailored to their environment. For example, Sung talks about a 4-story glass building in China which incorporates the laminate metals in the building’s exterior. This layer covering the building can open and close depending on the amount of sunlight available. This thermal-bimetal layer eliminates the need for drapes or shades. It acts as a privacy screen during different times of the day, and also controls the amount of air conditioning needed inside the building. Although, I wonder easily these “blinds” could be tailored to be open, partially opened or closed.
Another application of the thermo-bimetal is placing them between sheets of glass. Again, it can block out the Sun in certain areas of the building. This means the entire surface of a high rise building can be differentiated at different times of the day depending on how the Sun hits the exterior.
Sung doesn’t say which metals are used in her designs, but I suspect they are similar to the ones used in home thermostats (brass and invar steel) since they need to be responsive to a similar temperature range. But perhaps the biggest advantage of using thermo-bimetals in homes is that they are autonomous. They know to open and close when you’re away on vacation, or even during power outages.
Feature image of Sung’s themo-bimetal installation at the M&A in Silver Lake, California (photo credit: M&A)
Cimbala, J.M. (2011). Temperature Measurement. Retrieved from http://www.mne.psu.edu/me345/Lectures/Temperature_measurement.pdf
Howard, E.R. Thermostatic Bimetal. Retrieved from http://calteches.library.caltech.edu/82/1/Howard.pdf
Sung, D.K. (2012). Metal that breathes [Video file]. Retrieved from