The motion-based analysis of kinetic shading devices activated by smart materials

Solar rays reaching the indoor environment through the transparent components of the building envelope can adversely affect the energy performance of buildings. Operational energy efficiency can be achieved in buildings by using either fixed shading devices or kinetic systems that provide more efficient shading. Although high energy consumption may be required to operate active (i.e. motorized) kinetic shading devices, alternatively, the use of passive kinetic systems activated by smart materials allow for energy-efficient design. However, kinetic shading devices using passive systems have not yet gained currency in terms of production and application, when the associated literature is considered, but, it is clear that the interest in the subject of kinetic shading components activated by smart materials has increased in recent years. Yet, an analysis of the motion types and actuator design principles used in these studies is limited. This paper, therefore, aims to present an overview of kinetic shading devices activated by smart materials through a literature review, focusing on the use location of smart materials within shading devices (i.e. the function fulfilled) and the motion types that can be provided by each different smart material. The smart materials that will be examined and discussed in this respect are the shape memory alloys (SMA), shape memory polymers (SMP), thermo bi-metals, and hygroscopic woods (bi-layer wood, and bi-material wood). Another goal of the paper is to discuss the potential motion and geometry options for SMAs by examining the systems activated by other smart materials since SMAs are among the smart materials with high potential to be used as actuators in construction practice. The literature review focuses mainly on journal articles, conference papers, and book chapters indexed within Scopus and Web of Science databases, with particular attention on those containing implementation/application either as a prototype or as a product. In the paper, firstly, background information is given on smart materials with a focus on shape-changing materials among them, and motion typologies used in architecture. Following the explanation of the study methodology, the findings of the review are presented and discussed according to the common motions and shading device and/or unit geometries used in each shape-changing material. Additionally, the common motion mechanisms (i.e. actuator design principle) in each shape material and their adaption potential to be used with SMA are discussed. The discussions showed that the function of each of the examined smart materials in shading devices, the types of motion they can perform, the surface materials they are used with and their relations with them in the context of motion, their production and usage possibilities contain various advantages and difficulties unique to them.