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

A shading device for façade 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 mo-tors or manual activation, nor sophisticated electronic controls. The technical development of the system involved research of cylindri-cal 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 façade. 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