The Effect of Transition Hysteresis Width in Thermochromic Glazing Systems

Abstract

Thermochromic glazing theoretically has the potential to lead to a large reduction in energy demand in modern buildings by allowing the transmission of visible light for day lighting whilst reducing unwanted solar gain during the cooling season, but allowing useful solar gain in the heating season. In this study building simulation is used to examine the effect of the thermochromic transition hysteresis width on the energy demand characteristics of a model system in a variety of climates. The results are also compared against current industry standard glazing products. The results suggest that in a warm climate with a low transition temperature and hysteresis width energy demand can be reduced by up to 54% compared to standard double glazing.

The effect of variation in the transition hysteresis width and gradient in thermochromic glazing systems

“…With regard to "intelligent" glazing it has been assumed that the ideal properties are that the transition temperature for the material needs to be near that of room temperature (20-25°C), and that the transition should occur quickly meaning that the hysteresis loop width should be as narrow as possible and the gradient of the hysteresis should be steep as possible. While these parameters seem to be reasonable assumptions there has been little work assessing the energy performance dependence on these parameters [5,6].…”

How to be smart and energy efficient: A general discussion on thermochromic windows

“…However, these transition properties were not discussed further in this study. Comprehensive researches on these properties have been performed by the Binions group 16 17 . BuildingEnergy has been validated using ANSI/ASHRAE Standard 140-2004 (“Standard Method of Test for the Evaluation of Building Energy Analysis Computer Programs”) in our previous work 2 .…”

“…Warwick et al have pointed out that the thermochromic window with an energy-efficient benefit requires an ideal transition temperature between 20 and 25°C as well as a high visible transmittance and solar modulation ability 15 . When within this idea transition temperature range, a thin transition hysteresis width and a sharp gradient of the thermochromic materials can further improve the energy-efficient performance 16 17 .…”

Performance demonstration and simulation of thermochromic double glazing in building applications

“…A VO 2 film with a T s as low as 30°C has been reported (Huang et al, 2011). In addition to transmittance and T s , the transition hysteresis width and gradient of VO 2 also play crucial roles in the energy performance (Saeli et al, 2013;Warwick et al, 2013). The performance of a VO 2 single-glazed window has been demonstrated (Long and Ye, 2014;Ye et al, 2013a), showing that the application of the VO 2 film could reduce cooling energy consumption in a low-or heavy-mass room by approximately 15.1% or 9.4%, respectively.…”