A novel shading device for façade application was developed by combining innovative geometry elements (twisting cylinders) with a smart use of shape-memory alloys (SMA) component. This allows a dynamic behavior of a shading device, which does not require electrical motors or manual activation, and needs not sophisticated electronic controls. The technical development of the system involved exploration of shading geometries, namely twisting cylinders, which can transition from straight to hourglass configuration, a simple rotation that can be compatible with a small mechanical movement. These are activated by a small impulse given by a SMA spring, which functions as both actuator and sensor. Its design was selected and further refined to obtain a final component that could be activated under a set temperature stimuli, derived by incident solar radiation on a façade. A combination of simulations and physical tests were carried out to assess the optimal conditions of the SMA spring activation, with correlation between activation temperature and incident solar radiation, and the forces required to operate the cylinders. In parallel, a moving mechanism was developed, also by means of fast prototyping, to validate the concept on a geometrical point of view and to ensure that its constraints were compatible with a SMA spring control system.
Nowadays building envelopes are assuming a new identity: a gradual reduction of the façade solid area, which is substituted by transparent surfaces, is characterizing new architecture. The continuous evolution of
Shape memory alloys (SMA’s) are materials typically used in the medical and automotive sector for their reliability and integrability, as actuator or sensor. SMA can be shaped with many geometries
System development and operating principles
The shading system proposed is based on SMA springs passively activated. The use of a customised working principle allowed the optimization of the alloy features and
The temperature required for activation (Tbox), inside of the thermal box, is equal to 50°C. The system was designed to reach the aimed temperature during a time span lower than
Due to the considerations exposed in the data chapter the shading system is designed to self-activate with direct solar radiation on the façade surface > 300 W/m². Whenever this value
Under standard conditions, the parallel single fibers of the twisting cylinders were assumed to behave as a single sheet of fabric, in terms of blocking the incident solar radiation. The
We grateful thank the members of SEEDlab.abc @Politecnico di Milano (www.seed.polimi.it) for the supports during the measurements activities and all the suggestions provided during the writing of the paper. We also thank Pa&Co (http://pacoarchitecture.com/)for the support during the prototyping processes
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