A Novel Approach to Shape Memory Alloys Applied to Passive Adaptive Shading Systems

A shading device for facade application was developed by combining twisting cylindrical shading elements with the smart use of shape-memory alloy (SMA) components. These allow a dynamic behaviour of a shading device, which does not require electrical motors or manual activation, nor sophisticated electronic controls. The technical development of the system involved research of cylindrical shading geometries, which can transition from straight to hourglass configuration, given a 180° rotation, with limited mechanical movement. This is induced by the stroke of a SMA spring, which functions as both actuator and sensor. Its design is tailored to achieve a passive adaptive component that can be activated under set temperature stimuli, caused by incident solar radiation on a facade. A combination of computer simulations and physical tests were carried out to assess the optimal conditions of the SMA spring activation in a temperate climate condition (Cfa to the Koppen-Geiger classification), correlating transition temperature (50°C), incident solar radiation (>300W/m2 ) and the forces required to operate the cylinders. In parallel, an experimental apparatus was developed to validate the concept on a geometrical point of view, and to ensure its constraints were compatible with a SMA spring control system.