Dynamic Window

Windows are typically operable building components that are crucial to the good thermal performance of buildings. Windows had evolved from holes covered with cloth, mullioned glass, or paper, to modern-style floor-to-ceiling curtain walls, sealed with industrial glass. Today, responsive materials and AI control methods promise to add new dynamics to the functionality and the aesthetics of windows.

Dynamic windows aim to take active role in the dynamic optimization of building performance with low operational cost. The transitions of smart windows, optimally managed, can contribute to the reduction of energy consumption by heating and cooling.

For example, by optimizing the control of the state of electrochromic glass panes, the solar transmittance of windows becomes a programmable feature, by which it is possible to regulate the interior illuminance and temperature.

Also, polymer dispersed liquid crystal films (PDLC) and suspended particle displays, can eliminate the need for traditional blinds and shutter systems and revolutionize building aesthetics. Optical dimming and density variation can replace mechanical actuation with solid-state shading, glare and view-control.

Windows equipped with such capacities, can provide new ways to think about the management of energy, of daylight and of privacy, and can drastically transform the way we perceive and inhabit the built environment.

The capacity to reprogram a dynamic window enables autonomous, responsive and interactive behaviors, while taking into account not only functionality, but also social and cultural aspects. Smart windows re-establish some familiar attributes of traditional windows in the digital age.

In the dynamic window we developed for the connected sustainable home each window frame can be independently operable so that the permeability to airflow can be adjusted with precision. Each windowpane is an overlay of two electronically switchable materials: the first polymer-dispersed liquid crystal film [PDLC] can render the window transparent or opaque to visible light, securing privacy; the second Sage electrochromic layer controls the degree of solar penetration, securing thermal performance and regulating interior illuminance.

Dynamic windows operate in selective mode, admitting natural light, heat, and air, or excluding any of the above as needed. At the global level, the windows are directed by the central control system of the house without having any interference among them. At the local level, each window is driven by its own low level intelligence, software and custom electronics that enable the activation of its switchable materials.

Each window pane is equipped with a photocell to calculate the amount of light that it is exposed to, while an IR sensor detects the presence of the residents. The windows provide this sensory feedback to the central control that compiles the information to activate any number of windows is required.

Since the switchable materials have varying response times and exhibit different optical, thermal and power consumption characteristics, their activation processing is pre-planned.

The slow dimming response of 8 minutes, of the electrochromic glass, is suitable for controlling sunlight and heat, while the instant transition of the PDLC film is useful for controlling shade and privacy.

The PDLC film can be switched to entirely block the view, or it can adjust the degree of its opacity based on the detection of specific patterns of user activity. For example, the PDLC film can be programmed to output a varying opacity, corresponding to the gesture of holding the hand in front of the photocell for a range of time durations.

Reference
Kotsopoulos, SD, Casalegno, F, Ono, M, Graybill, W, 2012, “Window Panes Become Smart: How responsive materials and intelligent control will revolutionize the architecture of buildings”, in the Proceedings of the First International Conference on Smart Systems, Devices and Technologies (SMART 2012), Stuttgart, Germany, pp. 112-118.

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Connected Sustainable Home 2011