Saturday, February 9, 2013

Materials + Methods: Bimetallic Strips

In biology, there are numerous examples of systems intrinsically keeping themselves in balance (bonus point: if the word "homeostasis" jumped into your brain, you get a gold star) through feedback loops of various degrees of complexity. Feedback loops, in and of themselves, operate through mechanics that can be simulated or imitated in artificial methods. We see this done everyday in mundane devices, and sometimes it scarcely even dawns on us just how important it is that systems are capable of self-regulation without human input or intervention.

The notion of incorporating this concept into the built environment is something appeals to me greatly, and with any luck, I'll be able to work toward my thesis exploring this notion. However, my research goals aren't the point of this article. It's about creating smart buildings. Structures that can self-regulate critical functions and possibly even due so without requiring power in the traditional sense. Thus, self-regulating buildings represent a particularly inviting paradigm-shift in the modern setting - a structure that can reduce it's ecological footprint and increase efficiency.

I have no doubt that there are other materials that are capable of being applied to this sort of system, but for now, the material I want to talk about are thermo-bimetals, or more accurately, bimetallic strips. These are comprised of two strips of different metals that are bolted, welded or otherwise permanently connected together. Each piece of metal has a different coefficient of thermal expansion, which causes them to act in opposition to one another as the unit is exposed to heat. 

At this point, I think a quick explanation of the mechanics is in order. So, they have two different coefficients. So what? Well, to put it simply, as the metal unit will expand and bend one way if exposed to heat (due to the coefficient of one of the metals) and will contract and bend the other way if cooled to a point below the baseline temperature. Therefore, we have a system that can react in two possible directions based on a gradation of a particular stimulus (heat, in this case).

We see these in use in everyday items such as a typical thermostat, which uses the difference in expansion coefficients to trip the circuit responsible for heating your home when the ambient temperature becomes too cold. Also, the materials used are typically steel and copper, which makes these devices somewhat affordable for any potential architectural applications. 

Speaking of architectural applications, what are they exactly? Glad you asked. Ironically, it's not just a coincidence that bimetallic strips are seen in use in thermostats - they also possess a remarkable potential for regulating the interior temperature of a building. Imagine a lattice or even a wall woven out of bimetallic strips. If the interior temperature becomes too hot, the strips will deform and create an aperture that allows for air ventilation and circulation, thereby cooling the room back to baseline and causing the strips to return to their original state. Boom. Feedback loop. 

It's amazing to see how a biological concept can translate so well into a potential tool for the built environment.

As a caveat, I'd like to say that I have practically zero knowledge when it comes to the statics of these materials or any of the actual engineering parlance and technical jargon that would be required to implement such tools in practical use. But then again, the first step is often simply identifying a potential solution. The details will work themselves out, usually. However, I simply wanted to bring this sort of possibility to the attention of anyone out there with a vested interest in the architectural field. The scope of reality in the built environment is changing just as rapidly as the world around us. Finding solutions that can work smartly, effectively, and yes, as the risk of sounding passe, sustainably, is not necessarily the necessary choice, but the wise choice.

As they say, work smarter, not harder.

Also, if anyone is interested, there is an architect at USC who is doing a substantial amount of research into this concept - Doris Kim Sung. There's a video of her explaining her research and the applications of thermo-bimetals on TED, which I will provide below:

I hope to write additional posts on other unusual materials and methods later in the future, but I figured this would be a good place to start. These are the sort of things that captivate the imagination of both designers and any people that come to a place, I would think. Definitely feel free to post any suggestions about other ideas to explore or take a look into - I don't mind researching new and exciting things.

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