An autonomous shading system based on coupled wood bilayer elements

摘要

Climate Adaptive Building Shells can help to reach the aimed and required global reduction of energy consumption in the building sector. By being implemented as, e.g., facade shading systems, their adaptability to environmental changes can improve energy efficiency and indoor comfort of buildings. Autonomous, humidity-driven wood bilayers are proposed as an alternative to motor-driven facade shading elements. Due the hygro-responsiveness of the wood material, the changes of relative humidity during day and night as well as the drying effect of direct solar radiation can be utilized for inducing cyclic programmed shape changes of wood bilayers for aperture opening and closing of such adaptive facade shading systems. The kinetics of such autonomous shape changes of wood bilayers have been analyzed at small scale, but the application-relevant upscaling remains a challenge. So far, the proposed solutions do not allow maintaining a sufficiently high rate of shape change and the required mechanical stability of the wood bilayers at the same time. Here, we present the coupling of two wood bilayers as one possible solution for the implementation as shading elements. By coupling, the rate of aperture opening and closing can be amplified without increasing the (limited) rate of shape change of the single wood bilayers. The coupling and the resulting combination of shape change and rotation are characterized for five different typologies of lever arm configuration. Based on first studies with bilayer strips, an upscaling in width is conducted and its implementation for a humidity-driven shading system is presented by means of a demonstrator. (C) 2017 Elsevier B.V. All rights reserved.