3. Polarized Film Shading System in Regular Grids (PFSS)

Although the prototype of CASS documented in Ref. [13] has been based on liquid crystal (LC) technology, the original concept was imagined as an opto-mechanical system of square plates made of polarized glass [9]. Materialization of the reduced-scale prototype with prefabricated LC elements has been the most straightforward. The size of the shading element in the prototype was approx. \(12\times 12\) mm, which is by a range of magnitude smaller than intended final device. Thus in the full-scale prototype, this method probably would not be the most economical choice. The technology constantly evolves and high-tech solutions tend to become more affordable. Nevertheless, LC elements remain relatively expensive both in terms of: fabrication and running cost. LC available on the market requires approx. 5 \(W\over m^{2}\) of continuous power in the activated state [8]. Furthermore, according to [2] the transmittance modulation for commercial LC windows has been found unsatisfactory. Moreover, due to instability for UV radiation, LC windows have not been found appropriate for long-term building façade applications. This chapter further investigates the original method, where shading elements are comprised of two polygonal sheets of normally white polarized film.